Bug Summary

File:src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
Warning:line 3650, column 7
Called C++ object pointer is uninitialized

Annotated Source Code

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clang -cc1 -cc1 -triple amd64-unknown-openbsd7.0 -analyze -disable-free -disable-llvm-verifier -discard-value-names -main-file-name InstCombineCompares.cpp -analyzer-store=region -analyzer-opt-analyze-nested-blocks -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=cplusplus -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -setup-static-analyzer -mrelocation-model static -mframe-pointer=all -relaxed-aliasing -fno-rounding-math -mconstructor-aliases -munwind-tables -target-cpu x86-64 -tune-cpu generic -debugger-tuning=gdb -fcoverage-compilation-dir=/usr/src/gnu/usr.bin/clang/libLLVM/obj -resource-dir /usr/local/lib/clang/13.0.0 -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/Transforms -I /usr/src/gnu/usr.bin/clang/libLLVM/obj/../include/llvm/AMDGPU -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/lib/Target/AMDGPU -I /usr/src/gnu/usr.bin/clang/libLLVM/obj/../include/llvm/AMDGPU -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/lib/Target/AMDGPU -I /usr/src/gnu/usr.bin/clang/libLLVM/obj/../include/llvm/AMDGPU -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/lib/Target/AMDGPU -I /usr/src/gnu/usr.bin/clang/libLLVM/obj/../include/llvm/AMDGPU -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/lib/Target/AMDGPU -I /usr/src/gnu/usr.bin/clang/libLLVM/obj/../include/llvm/AMDGPU -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/lib/Target/AMDGPU -I /usr/src/gnu/usr.bin/clang/libLLVM/obj/../include/llvm/AMDGPU -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/lib/Target/AMDGPU -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/Analysis -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/ASMParser -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/BinaryFormat -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/Bitcode -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/Bitcode -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/Bitstream -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/Transforms -I /include/llvm/CodeGen -I /include/llvm/CodeGen/PBQP -I /usr/src/gnu/usr.bin/clang/libLLVM/obj/../include/llvm/IR -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/IR -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/Transforms -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/Transforms/Coroutines -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/ProfileData/Coverage -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/DebugInfo/CodeView -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/DebugInfo/DWARF -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/DebugInfo -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/DebugInfo/MSF -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/DebugInfo/PDB -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/Demangle -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/ExecutionEngine -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/ExecutionEngine/JITLink -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/ExecutionEngine/Orc -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/Frontend -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/Frontend/OpenACC -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/Frontend -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/Frontend/OpenMP -I /include/llvm/CodeGen/GlobalISel -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/IRReader -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/Transforms -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/Transforms/InstCombine -I /usr/src/gnu/usr.bin/clang/libLLVM/obj/../include/llvm/Transforms/InstCombine -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/Transforms -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/LTO -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/Linker -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/MC -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/MC/MCParser -I /include/llvm/CodeGen/MIRParser -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/Transforms -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/Object -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/Option -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/Passes -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/ -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/ProfileData -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/Transforms -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/Transforms/Scalar -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/ADT -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/Support -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/DebugInfo/Symbolize -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/Target -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/Transforms -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/Transforms/Utils -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/Transforms -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/Transforms/Vectorize -I /usr/src/gnu/usr.bin/clang/libLLVM/obj/../include/llvm/X86 -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/lib/Target/X86 -I /usr/src/gnu/usr.bin/clang/libLLVM/obj/../include/llvm/X86 -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/lib/Target/X86 -I /usr/src/gnu/usr.bin/clang/libLLVM/obj/../include/llvm/X86 -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/lib/Target/X86 -I /usr/src/gnu/usr.bin/clang/libLLVM/obj/../include/llvm/X86 -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/lib/Target/X86 -I /usr/src/gnu/usr.bin/clang/libLLVM/obj/../include/llvm/X86 -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/lib/Target/X86 -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/Transforms -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include/llvm/Transforms/IPO -I /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/include -I /usr/src/gnu/usr.bin/clang/libLLVM/../include -I /usr/src/gnu/usr.bin/clang/libLLVM/obj -I /usr/src/gnu/usr.bin/clang/libLLVM/obj/../include -D NDEBUG -D __STDC_LIMIT_MACROS -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D LLVM_PREFIX="/usr" -internal-isystem /usr/include/c++/v1 -internal-isystem /usr/local/lib/clang/13.0.0/include -internal-externc-isystem /usr/include -O2 -Wno-unused-parameter -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -Wno-comment -std=c++14 -fdeprecated-macro -fdebug-compilation-dir=/usr/src/gnu/usr.bin/clang/libLLVM/obj -ferror-limit 19 -fvisibility-inlines-hidden -fwrapv -stack-protector 2 -fno-rtti -fgnuc-version=4.2.1 -vectorize-loops -vectorize-slp -fno-builtin-malloc -fno-builtin-calloc -fno-builtin-realloc -fno-builtin-valloc -fno-builtin-free -fno-builtin-strdup -fno-builtin-strndup -analyzer-output=html -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /home/ben/Projects/vmm/scan-build/2022-01-12-194120-40624-1 -x c++ /usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp

/usr/src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp

→
1//===- InstCombineCompares.cpp --------------------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file implements the visitICmp and visitFCmp functions.
10//
11//===----------------------------------------------------------------------===//
12
13#include "InstCombineInternal.h"
14#include "llvm/ADT/APSInt.h"
15#include "llvm/ADT/SetVector.h"
16#include "llvm/ADT/Statistic.h"
17#include "llvm/Analysis/ConstantFolding.h"
18#include "llvm/Analysis/InstructionSimplify.h"
19#include "llvm/Analysis/TargetLibraryInfo.h"
20#include "llvm/IR/ConstantRange.h"
21#include "llvm/IR/DataLayout.h"
22#include "llvm/IR/GetElementPtrTypeIterator.h"
23#include "llvm/IR/IntrinsicInst.h"
24#include "llvm/IR/PatternMatch.h"
25#include "llvm/Support/Debug.h"
26#include "llvm/Support/KnownBits.h"
27#include "llvm/Transforms/InstCombine/InstCombiner.h"
28
29using namespace llvm;
30using namespace PatternMatch;
31
32#define DEBUG_TYPE"instcombine" "instcombine"
33
34// How many times is a select replaced by one of its operands?
35STATISTIC(NumSel, "Number of select opts")static llvm::Statistic NumSel = {"instcombine", "NumSel", "Number of select opts"
};
36
37
38/// Compute Result = In1+In2, returning true if the result overflowed for this
39/// type.
40static bool addWithOverflow(APInt &Result, const APInt &In1,
41 const APInt &In2, bool IsSigned = false) {
42 bool Overflow;
43 if (IsSigned)
44 Result = In1.sadd_ov(In2, Overflow);
45 else
46 Result = In1.uadd_ov(In2, Overflow);
47
48 return Overflow;
49}
50
51/// Compute Result = In1-In2, returning true if the result overflowed for this
52/// type.
53static bool subWithOverflow(APInt &Result, const APInt &In1,
54 const APInt &In2, bool IsSigned = false) {
55 bool Overflow;
56 if (IsSigned)
57 Result = In1.ssub_ov(In2, Overflow);
58 else
59 Result = In1.usub_ov(In2, Overflow);
60
61 return Overflow;
62}
63
64/// Given an icmp instruction, return true if any use of this comparison is a
65/// branch on sign bit comparison.
66static bool hasBranchUse(ICmpInst &I) {
67 for (auto *U : I.users())
68 if (isa<BranchInst>(U))
69 return true;
70 return false;
71}
72
73/// Returns true if the exploded icmp can be expressed as a signed comparison
74/// to zero and updates the predicate accordingly.
75/// The signedness of the comparison is preserved.
76/// TODO: Refactor with decomposeBitTestICmp()?
77static bool isSignTest(ICmpInst::Predicate &Pred, const APInt &C) {
78 if (!ICmpInst::isSigned(Pred))
79 return false;
80
81 if (C.isNullValue())
82 return ICmpInst::isRelational(Pred);
83
84 if (C.isOneValue()) {
85 if (Pred == ICmpInst::ICMP_SLT) {
86 Pred = ICmpInst::ICMP_SLE;
87 return true;
88 }
89 } else if (C.isAllOnesValue()) {
90 if (Pred == ICmpInst::ICMP_SGT) {
91 Pred = ICmpInst::ICMP_SGE;
92 return true;
93 }
94 }
95
96 return false;
97}
98
99/// This is called when we see this pattern:
100/// cmp pred (load (gep GV, ...)), cmpcst
101/// where GV is a global variable with a constant initializer. Try to simplify
102/// this into some simple computation that does not need the load. For example
103/// we can optimize "icmp eq (load (gep "foo", 0, i)), 0" into "icmp eq i, 3".
104///
105/// If AndCst is non-null, then the loaded value is masked with that constant
106/// before doing the comparison. This handles cases like "A[i]&4 == 0".
107Instruction *
108InstCombinerImpl::foldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP,
109 GlobalVariable *GV, CmpInst &ICI,
110 ConstantInt *AndCst) {
111 Constant *Init = GV->getInitializer();
112 if (!isa<ConstantArray>(Init) && !isa<ConstantDataArray>(Init))
113 return nullptr;
114
115 uint64_t ArrayElementCount = Init->getType()->getArrayNumElements();
116 // Don't blow up on huge arrays.
117 if (ArrayElementCount > MaxArraySizeForCombine)
118 return nullptr;
119
120 // There are many forms of this optimization we can handle, for now, just do
121 // the simple index into a single-dimensional array.
122 //
123 // Require: GEP GV, 0, i {{, constant indices}}
124 if (GEP->getNumOperands() < 3 ||
125 !isa<ConstantInt>(GEP->getOperand(1)) ||
126 !cast<ConstantInt>(GEP->getOperand(1))->isZero() ||
127 isa<Constant>(GEP->getOperand(2)))
128 return nullptr;
129
130 // Check that indices after the variable are constants and in-range for the
131 // type they index. Collect the indices. This is typically for arrays of
132 // structs.
133 SmallVector<unsigned, 4> LaterIndices;
134
135 Type *EltTy = Init->getType()->getArrayElementType();
136 for (unsigned i = 3, e = GEP->getNumOperands(); i != e; ++i) {
137 ConstantInt *Idx = dyn_cast<ConstantInt>(GEP->getOperand(i));
138 if (!Idx) return nullptr; // Variable index.
139
140 uint64_t IdxVal = Idx->getZExtValue();
141 if ((unsigned)IdxVal != IdxVal) return nullptr; // Too large array index.
142
143 if (StructType *STy = dyn_cast<StructType>(EltTy))
144 EltTy = STy->getElementType(IdxVal);
145 else if (ArrayType *ATy = dyn_cast<ArrayType>(EltTy)) {
146 if (IdxVal >= ATy->getNumElements()) return nullptr;
147 EltTy = ATy->getElementType();
148 } else {
149 return nullptr; // Unknown type.
150 }
151
152 LaterIndices.push_back(IdxVal);
153 }
154
155 enum { Overdefined = -3, Undefined = -2 };
156
157 // Variables for our state machines.
158
159 // FirstTrueElement/SecondTrueElement - Used to emit a comparison of the form
160 // "i == 47 | i == 87", where 47 is the first index the condition is true for,
161 // and 87 is the second (and last) index. FirstTrueElement is -2 when
162 // undefined, otherwise set to the first true element. SecondTrueElement is
163 // -2 when undefined, -3 when overdefined and >= 0 when that index is true.
164 int FirstTrueElement = Undefined, SecondTrueElement = Undefined;
165
166 // FirstFalseElement/SecondFalseElement - Used to emit a comparison of the
167 // form "i != 47 & i != 87". Same state transitions as for true elements.
168 int FirstFalseElement = Undefined, SecondFalseElement = Undefined;
169
170 /// TrueRangeEnd/FalseRangeEnd - In conjunction with First*Element, these
171 /// define a state machine that triggers for ranges of values that the index
172 /// is true or false for. This triggers on things like "abbbbc"[i] == 'b'.
173 /// This is -2 when undefined, -3 when overdefined, and otherwise the last
174 /// index in the range (inclusive). We use -2 for undefined here because we
175 /// use relative comparisons and don't want 0-1 to match -1.
176 int TrueRangeEnd = Undefined, FalseRangeEnd = Undefined;
177
178 // MagicBitvector - This is a magic bitvector where we set a bit if the
179 // comparison is true for element 'i'. If there are 64 elements or less in
180 // the array, this will fully represent all the comparison results.
181 uint64_t MagicBitvector = 0;
182
183 // Scan the array and see if one of our patterns matches.
184 Constant *CompareRHS = cast<Constant>(ICI.getOperand(1));
185 for (unsigned i = 0, e = ArrayElementCount; i != e; ++i) {
186 Constant *Elt = Init->getAggregateElement(i);
187 if (!Elt) return nullptr;
188
189 // If this is indexing an array of structures, get the structure element.
190 if (!LaterIndices.empty())
191 Elt = ConstantExpr::getExtractValue(Elt, LaterIndices);
192
193 // If the element is masked, handle it.
194 if (AndCst) Elt = ConstantExpr::getAnd(Elt, AndCst);
195
196 // Find out if the comparison would be true or false for the i'th element.
197 Constant *C = ConstantFoldCompareInstOperands(ICI.getPredicate(), Elt,
198 CompareRHS, DL, &TLI);
199 // If the result is undef for this element, ignore it.
200 if (isa<UndefValue>(C)) {
201 // Extend range state machines to cover this element in case there is an
202 // undef in the middle of the range.
203 if (TrueRangeEnd == (int)i-1)
204 TrueRangeEnd = i;
205 if (FalseRangeEnd == (int)i-1)
206 FalseRangeEnd = i;
207 continue;
208 }
209
210 // If we can't compute the result for any of the elements, we have to give
211 // up evaluating the entire conditional.
212 if (!isa<ConstantInt>(C)) return nullptr;
213
214 // Otherwise, we know if the comparison is true or false for this element,
215 // update our state machines.
216 bool IsTrueForElt = !cast<ConstantInt>(C)->isZero();
217
218 // State machine for single/double/range index comparison.
219 if (IsTrueForElt) {
220 // Update the TrueElement state machine.
221 if (FirstTrueElement == Undefined)
222 FirstTrueElement = TrueRangeEnd = i; // First true element.
223 else {
224 // Update double-compare state machine.
225 if (SecondTrueElement == Undefined)
226 SecondTrueElement = i;
227 else
228 SecondTrueElement = Overdefined;
229
230 // Update range state machine.
231 if (TrueRangeEnd == (int)i-1)
232 TrueRangeEnd = i;
233 else
234 TrueRangeEnd = Overdefined;
235 }
236 } else {
237 // Update the FalseElement state machine.
238 if (FirstFalseElement == Undefined)
239 FirstFalseElement = FalseRangeEnd = i; // First false element.
240 else {
241 // Update double-compare state machine.
242 if (SecondFalseElement == Undefined)
243 SecondFalseElement = i;
244 else
245 SecondFalseElement = Overdefined;
246
247 // Update range state machine.
248 if (FalseRangeEnd == (int)i-1)
249 FalseRangeEnd = i;
250 else
251 FalseRangeEnd = Overdefined;
252 }
253 }
254
255 // If this element is in range, update our magic bitvector.
256 if (i < 64 && IsTrueForElt)
257 MagicBitvector |= 1ULL << i;
258
259 // If all of our states become overdefined, bail out early. Since the
260 // predicate is expensive, only check it every 8 elements. This is only
261 // really useful for really huge arrays.
262 if ((i & 8) == 0 && i >= 64 && SecondTrueElement == Overdefined &&
263 SecondFalseElement == Overdefined && TrueRangeEnd == Overdefined &&
264 FalseRangeEnd == Overdefined)
265 return nullptr;
266 }
267
268 // Now that we've scanned the entire array, emit our new comparison(s). We
269 // order the state machines in complexity of the generated code.
270 Value *Idx = GEP->getOperand(2);
271
272 // If the index is larger than the pointer size of the target, truncate the
273 // index down like the GEP would do implicitly. We don't have to do this for
274 // an inbounds GEP because the index can't be out of range.
275 if (!GEP->isInBounds()) {
276 Type *IntPtrTy = DL.getIntPtrType(GEP->getType());
277 unsigned PtrSize = IntPtrTy->getIntegerBitWidth();
278 if (Idx->getType()->getPrimitiveSizeInBits().getFixedSize() > PtrSize)
279 Idx = Builder.CreateTrunc(Idx, IntPtrTy);
280 }
281
282 // If inbounds keyword is not present, Idx * ElementSize can overflow.
283 // Let's assume that ElementSize is 2 and the wanted value is at offset 0.
284 // Then, there are two possible values for Idx to match offset 0:
285 // 0x00..00, 0x80..00.
286 // Emitting 'icmp eq Idx, 0' isn't correct in this case because the
287 // comparison is false if Idx was 0x80..00.
288 // We need to erase the highest countTrailingZeros(ElementSize) bits of Idx.
289 unsigned ElementSize =
290 DL.getTypeAllocSize(Init->getType()->getArrayElementType());
291 auto MaskIdx = [&](Value* Idx){
292 if (!GEP->isInBounds() && countTrailingZeros(ElementSize) != 0) {
293 Value *Mask = ConstantInt::get(Idx->getType(), -1);
294 Mask = Builder.CreateLShr(Mask, countTrailingZeros(ElementSize));
295 Idx = Builder.CreateAnd(Idx, Mask);
296 }
297 return Idx;
298 };
299
300 // If the comparison is only true for one or two elements, emit direct
301 // comparisons.
302 if (SecondTrueElement != Overdefined) {
303 Idx = MaskIdx(Idx);
304 // None true -> false.
305 if (FirstTrueElement == Undefined)
306 return replaceInstUsesWith(ICI, Builder.getFalse());
307
308 Value *FirstTrueIdx = ConstantInt::get(Idx->getType(), FirstTrueElement);
309
310 // True for one element -> 'i == 47'.
311 if (SecondTrueElement == Undefined)
312 return new ICmpInst(ICmpInst::ICMP_EQ, Idx, FirstTrueIdx);
313
314 // True for two elements -> 'i == 47 | i == 72'.
315 Value *C1 = Builder.CreateICmpEQ(Idx, FirstTrueIdx);
316 Value *SecondTrueIdx = ConstantInt::get(Idx->getType(), SecondTrueElement);
317 Value *C2 = Builder.CreateICmpEQ(Idx, SecondTrueIdx);
318 return BinaryOperator::CreateOr(C1, C2);
319 }
320
321 // If the comparison is only false for one or two elements, emit direct
322 // comparisons.
323 if (SecondFalseElement != Overdefined) {
324 Idx = MaskIdx(Idx);
325 // None false -> true.
326 if (FirstFalseElement == Undefined)
327 return replaceInstUsesWith(ICI, Builder.getTrue());
328
329 Value *FirstFalseIdx = ConstantInt::get(Idx->getType(), FirstFalseElement);
330
331 // False for one element -> 'i != 47'.
332 if (SecondFalseElement == Undefined)
333 return new ICmpInst(ICmpInst::ICMP_NE, Idx, FirstFalseIdx);
334
335 // False for two elements -> 'i != 47 & i != 72'.
336 Value *C1 = Builder.CreateICmpNE(Idx, FirstFalseIdx);
337 Value *SecondFalseIdx = ConstantInt::get(Idx->getType(),SecondFalseElement);
338 Value *C2 = Builder.CreateICmpNE(Idx, SecondFalseIdx);
339 return BinaryOperator::CreateAnd(C1, C2);
340 }
341
342 // If the comparison can be replaced with a range comparison for the elements
343 // where it is true, emit the range check.
344 if (TrueRangeEnd != Overdefined) {
345 assert(TrueRangeEnd != FirstTrueElement && "Should emit single compare")((void)0);
346 Idx = MaskIdx(Idx);
347
348 // Generate (i-FirstTrue) <u (TrueRangeEnd-FirstTrue+1).
349 if (FirstTrueElement) {
350 Value *Offs = ConstantInt::get(Idx->getType(), -FirstTrueElement);
351 Idx = Builder.CreateAdd(Idx, Offs);
352 }
353
354 Value *End = ConstantInt::get(Idx->getType(),
355 TrueRangeEnd-FirstTrueElement+1);
356 return new ICmpInst(ICmpInst::ICMP_ULT, Idx, End);
357 }
358
359 // False range check.
360 if (FalseRangeEnd != Overdefined) {
361 assert(FalseRangeEnd != FirstFalseElement && "Should emit single compare")((void)0);
362 Idx = MaskIdx(Idx);
363 // Generate (i-FirstFalse) >u (FalseRangeEnd-FirstFalse).
364 if (FirstFalseElement) {
365 Value *Offs = ConstantInt::get(Idx->getType(), -FirstFalseElement);
366 Idx = Builder.CreateAdd(Idx, Offs);
367 }
368
369 Value *End = ConstantInt::get(Idx->getType(),
370 FalseRangeEnd-FirstFalseElement);
371 return new ICmpInst(ICmpInst::ICMP_UGT, Idx, End);
372 }
373
374 // If a magic bitvector captures the entire comparison state
375 // of this load, replace it with computation that does:
376 // ((magic_cst >> i) & 1) != 0
377 {
378 Type *Ty = nullptr;
379
380 // Look for an appropriate type:
381 // - The type of Idx if the magic fits
382 // - The smallest fitting legal type
383 if (ArrayElementCount <= Idx->getType()->getIntegerBitWidth())
384 Ty = Idx->getType();
385 else
386 Ty = DL.getSmallestLegalIntType(Init->getContext(), ArrayElementCount);
387
388 if (Ty) {
389 Idx = MaskIdx(Idx);
390 Value *V = Builder.CreateIntCast(Idx, Ty, false);
391 V = Builder.CreateLShr(ConstantInt::get(Ty, MagicBitvector), V);
392 V = Builder.CreateAnd(ConstantInt::get(Ty, 1), V);
393 return new ICmpInst(ICmpInst::ICMP_NE, V, ConstantInt::get(Ty, 0));
394 }
395 }
396
397 return nullptr;
398}
399
400/// Return a value that can be used to compare the *offset* implied by a GEP to
401/// zero. For example, if we have &A[i], we want to return 'i' for
402/// "icmp ne i, 0". Note that, in general, indices can be complex, and scales
403/// are involved. The above expression would also be legal to codegen as
404/// "icmp ne (i*4), 0" (assuming A is a pointer to i32).
405/// This latter form is less amenable to optimization though, and we are allowed
406/// to generate the first by knowing that pointer arithmetic doesn't overflow.
407///
408/// If we can't emit an optimized form for this expression, this returns null.
409///
410static Value *evaluateGEPOffsetExpression(User *GEP, InstCombinerImpl &IC,
411 const DataLayout &DL) {
412 gep_type_iterator GTI = gep_type_begin(GEP);
413
414 // Check to see if this gep only has a single variable index. If so, and if
415 // any constant indices are a multiple of its scale, then we can compute this
416 // in terms of the scale of the variable index. For example, if the GEP
417 // implies an offset of "12 + i*4", then we can codegen this as "3 + i",
418 // because the expression will cross zero at the same point.
419 unsigned i, e = GEP->getNumOperands();
420 int64_t Offset = 0;
421 for (i = 1; i != e; ++i, ++GTI) {
422 if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i))) {
423 // Compute the aggregate offset of constant indices.
424 if (CI->isZero()) continue;
425
426 // Handle a struct index, which adds its field offset to the pointer.
427 if (StructType *STy = GTI.getStructTypeOrNull()) {
428 Offset += DL.getStructLayout(STy)->getElementOffset(CI->getZExtValue());
429 } else {
430 uint64_t Size = DL.getTypeAllocSize(GTI.getIndexedType());
431 Offset += Size*CI->getSExtValue();
432 }
433 } else {
434 // Found our variable index.
435 break;
436 }
437 }
438
439 // If there are no variable indices, we must have a constant offset, just
440 // evaluate it the general way.
441 if (i == e) return nullptr;
442
443 Value *VariableIdx = GEP->getOperand(i);
444 // Determine the scale factor of the variable element. For example, this is
445 // 4 if the variable index is into an array of i32.
446 uint64_t VariableScale = DL.getTypeAllocSize(GTI.getIndexedType());
447
448 // Verify that there are no other variable indices. If so, emit the hard way.
449 for (++i, ++GTI; i != e; ++i, ++GTI) {
450 ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i));
451 if (!CI) return nullptr;
452
453 // Compute the aggregate offset of constant indices.
454 if (CI->isZero()) continue;
455
456 // Handle a struct index, which adds its field offset to the pointer.
457 if (StructType *STy = GTI.getStructTypeOrNull()) {
458 Offset += DL.getStructLayout(STy)->getElementOffset(CI->getZExtValue());
459 } else {
460 uint64_t Size = DL.getTypeAllocSize(GTI.getIndexedType());
461 Offset += Size*CI->getSExtValue();
462 }
463 }
464
465 // Okay, we know we have a single variable index, which must be a
466 // pointer/array/vector index. If there is no offset, life is simple, return
467 // the index.
468 Type *IntPtrTy = DL.getIntPtrType(GEP->getOperand(0)->getType());
469 unsigned IntPtrWidth = IntPtrTy->getIntegerBitWidth();
470 if (Offset == 0) {
471 // Cast to intptrty in case a truncation occurs. If an extension is needed,
472 // we don't need to bother extending: the extension won't affect where the
473 // computation crosses zero.
474 if (VariableIdx->getType()->getPrimitiveSizeInBits().getFixedSize() >
475 IntPtrWidth) {
476 VariableIdx = IC.Builder.CreateTrunc(VariableIdx, IntPtrTy);
477 }
478 return VariableIdx;
479 }
480
481 // Otherwise, there is an index. The computation we will do will be modulo
482 // the pointer size.
483 Offset = SignExtend64(Offset, IntPtrWidth);
484 VariableScale = SignExtend64(VariableScale, IntPtrWidth);
485
486 // To do this transformation, any constant index must be a multiple of the
487 // variable scale factor. For example, we can evaluate "12 + 4*i" as "3 + i",
488 // but we can't evaluate "10 + 3*i" in terms of i. Check that the offset is a
489 // multiple of the variable scale.
490 int64_t NewOffs = Offset / (int64_t)VariableScale;
491 if (Offset != NewOffs*(int64_t)VariableScale)
492 return nullptr;
493
494 // Okay, we can do this evaluation. Start by converting the index to intptr.
495 if (VariableIdx->getType() != IntPtrTy)
496 VariableIdx = IC.Builder.CreateIntCast(VariableIdx, IntPtrTy,
497 true /*Signed*/);
498 Constant *OffsetVal = ConstantInt::get(IntPtrTy, NewOffs);
499 return IC.Builder.CreateAdd(VariableIdx, OffsetVal, "offset");
500}
501
502/// Returns true if we can rewrite Start as a GEP with pointer Base
503/// and some integer offset. The nodes that need to be re-written
504/// for this transformation will be added to Explored.
505static bool canRewriteGEPAsOffset(Value *Start, Value *Base,
506 const DataLayout &DL,
507 SetVector<Value *> &Explored) {
508 SmallVector<Value *, 16> WorkList(1, Start);
509 Explored.insert(Base);
510
511 // The following traversal gives us an order which can be used
512 // when doing the final transformation. Since in the final
513 // transformation we create the PHI replacement instructions first,
514 // we don't have to get them in any particular order.
515 //
516 // However, for other instructions we will have to traverse the
517 // operands of an instruction first, which means that we have to
518 // do a post-order traversal.
519 while (!WorkList.empty()) {
520 SetVector<PHINode *> PHIs;
521
522 while (!WorkList.empty()) {
523 if (Explored.size() >= 100)
524 return false;
525
526 Value *V = WorkList.back();
527
528 if (Explored.contains(V)) {
529 WorkList.pop_back();
530 continue;
531 }
532
533 if (!isa<IntToPtrInst>(V) && !isa<PtrToIntInst>(V) &&
534 !isa<GetElementPtrInst>(V) && !isa<PHINode>(V))
535 // We've found some value that we can't explore which is different from
536 // the base. Therefore we can't do this transformation.
537 return false;
538
539 if (isa<IntToPtrInst>(V) || isa<PtrToIntInst>(V)) {
540 auto *CI = cast<CastInst>(V);
541 if (!CI->isNoopCast(DL))
542 return false;
543
544 if (Explored.count(CI->getOperand(0)) == 0)
545 WorkList.push_back(CI->getOperand(0));
546 }
547
548 if (auto *GEP = dyn_cast<GEPOperator>(V)) {
549 // We're limiting the GEP to having one index. This will preserve
550 // the original pointer type. We could handle more cases in the
551 // future.
552 if (GEP->getNumIndices() != 1 || !GEP->isInBounds() ||
553 GEP->getType() != Start->getType())
554 return false;
555
556 if (Explored.count(GEP->getOperand(0)) == 0)
557 WorkList.push_back(GEP->getOperand(0));
558 }
559
560 if (WorkList.back() == V) {
561 WorkList.pop_back();
562 // We've finished visiting this node, mark it as such.
563 Explored.insert(V);
564 }
565
566 if (auto *PN = dyn_cast<PHINode>(V)) {
567 // We cannot transform PHIs on unsplittable basic blocks.
568 if (isa<CatchSwitchInst>(PN->getParent()->getTerminator()))
569 return false;
570 Explored.insert(PN);
571 PHIs.insert(PN);
572 }
573 }
574
575 // Explore the PHI nodes further.
576 for (auto *PN : PHIs)
577 for (Value *Op : PN->incoming_values())
578 if (Explored.count(Op) == 0)
579 WorkList.push_back(Op);
580 }
581
582 // Make sure that we can do this. Since we can't insert GEPs in a basic
583 // block before a PHI node, we can't easily do this transformation if
584 // we have PHI node users of transformed instructions.
585 for (Value *Val : Explored) {
586 for (Value *Use : Val->uses()) {
587
588 auto *PHI = dyn_cast<PHINode>(Use);
589 auto *Inst = dyn_cast<Instruction>(Val);
590
591 if (Inst == Base || Inst == PHI || !Inst || !PHI ||
592 Explored.count(PHI) == 0)
593 continue;
594
595 if (PHI->getParent() == Inst->getParent())
596 return false;
597 }
598 }
599 return true;
600}
601
602// Sets the appropriate insert point on Builder where we can add
603// a replacement Instruction for V (if that is possible).
604static void setInsertionPoint(IRBuilder<> &Builder, Value *V,
605 bool Before = true) {
606 if (auto *PHI = dyn_cast<PHINode>(V)) {
607 Builder.SetInsertPoint(&*PHI->getParent()->getFirstInsertionPt());
608 return;
609 }
610 if (auto *I = dyn_cast<Instruction>(V)) {
611 if (!Before)
612 I = &*std::next(I->getIterator());
613 Builder.SetInsertPoint(I);
614 return;
615 }
616 if (auto *A = dyn_cast<Argument>(V)) {
617 // Set the insertion point in the entry block.
618 BasicBlock &Entry = A->getParent()->getEntryBlock();
619 Builder.SetInsertPoint(&*Entry.getFirstInsertionPt());
620 return;
621 }
622 // Otherwise, this is a constant and we don't need to set a new
623 // insertion point.
624 assert(isa<Constant>(V) && "Setting insertion point for unknown value!")((void)0);
625}
626
627/// Returns a re-written value of Start as an indexed GEP using Base as a
628/// pointer.
629static Value *rewriteGEPAsOffset(Value *Start, Value *Base,
630 const DataLayout &DL,
631 SetVector<Value *> &Explored) {
632 // Perform all the substitutions. This is a bit tricky because we can
633 // have cycles in our use-def chains.
634 // 1. Create the PHI nodes without any incoming values.
635 // 2. Create all the other values.
636 // 3. Add the edges for the PHI nodes.
637 // 4. Emit GEPs to get the original pointers.
638 // 5. Remove the original instructions.
639 Type *IndexType = IntegerType::get(
640 Base->getContext(), DL.getIndexTypeSizeInBits(Start->getType()));
641
642 DenseMap<Value *, Value *> NewInsts;
643 NewInsts[Base] = ConstantInt::getNullValue(IndexType);
644
645 // Create the new PHI nodes, without adding any incoming values.
646 for (Value *Val : Explored) {
647 if (Val == Base)
648 continue;
649 // Create empty phi nodes. This avoids cyclic dependencies when creating
650 // the remaining instructions.
651 if (auto *PHI = dyn_cast<PHINode>(Val))
652 NewInsts[PHI] = PHINode::Create(IndexType, PHI->getNumIncomingValues(),
653 PHI->getName() + ".idx", PHI);
654 }
655 IRBuilder<> Builder(Base->getContext());
656
657 // Create all the other instructions.
658 for (Value *Val : Explored) {
659
660 if (NewInsts.find(Val) != NewInsts.end())
661 continue;
662
663 if (auto *CI = dyn_cast<CastInst>(Val)) {
664 // Don't get rid of the intermediate variable here; the store can grow
665 // the map which will invalidate the reference to the input value.
666 Value *V = NewInsts[CI->getOperand(0)];
667 NewInsts[CI] = V;
668 continue;
669 }
670 if (auto *GEP = dyn_cast<GEPOperator>(Val)) {
671 Value *Index = NewInsts[GEP->getOperand(1)] ? NewInsts[GEP->getOperand(1)]
672 : GEP->getOperand(1);
673 setInsertionPoint(Builder, GEP);
674 // Indices might need to be sign extended. GEPs will magically do
675 // this, but we need to do it ourselves here.
676 if (Index->getType()->getScalarSizeInBits() !=
677 NewInsts[GEP->getOperand(0)]->getType()->getScalarSizeInBits()) {
678 Index = Builder.CreateSExtOrTrunc(
679 Index, NewInsts[GEP->getOperand(0)]->getType(),
680 GEP->getOperand(0)->getName() + ".sext");
681 }
682
683 auto *Op = NewInsts[GEP->getOperand(0)];
684 if (isa<ConstantInt>(Op) && cast<ConstantInt>(Op)->isZero())
685 NewInsts[GEP] = Index;
686 else
687 NewInsts[GEP] = Builder.CreateNSWAdd(
688 Op, Index, GEP->getOperand(0)->getName() + ".add");
689 continue;
690 }
691 if (isa<PHINode>(Val))
692 continue;
693
694 llvm_unreachable("Unexpected instruction type")__builtin_unreachable();
695 }
696
697 // Add the incoming values to the PHI nodes.
698 for (Value *Val : Explored) {
699 if (Val == Base)
700 continue;
701 // All the instructions have been created, we can now add edges to the
702 // phi nodes.
703 if (auto *PHI = dyn_cast<PHINode>(Val)) {
704 PHINode *NewPhi = static_cast<PHINode *>(NewInsts[PHI]);
705 for (unsigned I = 0, E = PHI->getNumIncomingValues(); I < E; ++I) {
706 Value *NewIncoming = PHI->getIncomingValue(I);
707
708 if (NewInsts.find(NewIncoming) != NewInsts.end())
709 NewIncoming = NewInsts[NewIncoming];
710
711 NewPhi->addIncoming(NewIncoming, PHI->getIncomingBlock(I));
712 }
713 }
714 }
715
716 for (Value *Val : Explored) {
717 if (Val == Base)
718 continue;
719
720 // Depending on the type, for external users we have to emit
721 // a GEP or a GEP + ptrtoint.
722 setInsertionPoint(Builder, Val, false);
723
724 // If required, create an inttoptr instruction for Base.
725 Value *NewBase = Base;
726 if (!Base->getType()->isPointerTy())
727 NewBase = Builder.CreateBitOrPointerCast(Base, Start->getType(),
728 Start->getName() + "to.ptr");
729
730 Value *GEP = Builder.CreateInBoundsGEP(
731 Start->getType()->getPointerElementType(), NewBase,
732 makeArrayRef(NewInsts[Val]), Val->getName() + ".ptr");
733
734 if (!Val->getType()->isPointerTy()) {
735 Value *Cast = Builder.CreatePointerCast(GEP, Val->getType(),
736 Val->getName() + ".conv");
737 GEP = Cast;
738 }
739 Val->replaceAllUsesWith(GEP);
740 }
741
742 return NewInsts[Start];
743}
744
745/// Looks through GEPs, IntToPtrInsts and PtrToIntInsts in order to express
746/// the input Value as a constant indexed GEP. Returns a pair containing
747/// the GEPs Pointer and Index.
748static std::pair<Value *, Value *>
749getAsConstantIndexedAddress(Value *V, const DataLayout &DL) {
750 Type *IndexType = IntegerType::get(V->getContext(),
751 DL.getIndexTypeSizeInBits(V->getType()));
752
753 Constant *Index = ConstantInt::getNullValue(IndexType);
754 while (true) {
755 if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
756 // We accept only inbouds GEPs here to exclude the possibility of
757 // overflow.
758 if (!GEP->isInBounds())
759 break;
760 if (GEP->hasAllConstantIndices() && GEP->getNumIndices() == 1 &&
761 GEP->getType() == V->getType()) {
762 V = GEP->getOperand(0);
763 Constant *GEPIndex = static_cast<Constant *>(GEP->getOperand(1));
764 Index = ConstantExpr::getAdd(
765 Index, ConstantExpr::getSExtOrBitCast(GEPIndex, IndexType));
766 continue;
767 }
768 break;
769 }
770 if (auto *CI = dyn_cast<IntToPtrInst>(V)) {
771 if (!CI->isNoopCast(DL))
772 break;
773 V = CI->getOperand(0);
774 continue;
775 }
776 if (auto *CI = dyn_cast<PtrToIntInst>(V)) {
777 if (!CI->isNoopCast(DL))
778 break;
779 V = CI->getOperand(0);
780 continue;
781 }
782 break;
783 }
784 return {V, Index};
785}
786
787/// Converts (CMP GEPLHS, RHS) if this change would make RHS a constant.
788/// We can look through PHIs, GEPs and casts in order to determine a common base
789/// between GEPLHS and RHS.
790static Instruction *transformToIndexedCompare(GEPOperator *GEPLHS, Value *RHS,
791 ICmpInst::Predicate Cond,
792 const DataLayout &DL) {
793 // FIXME: Support vector of pointers.
794 if (GEPLHS->getType()->isVectorTy())
795 return nullptr;
796
797 if (!GEPLHS->hasAllConstantIndices())
798 return nullptr;
799
800 // Make sure the pointers have the same type.
801 if (GEPLHS->getType() != RHS->getType())
802 return nullptr;
803
804 Value *PtrBase, *Index;
805 std::tie(PtrBase, Index) = getAsConstantIndexedAddress(GEPLHS, DL);
806
807 // The set of nodes that will take part in this transformation.
808 SetVector<Value *> Nodes;
809
810 if (!canRewriteGEPAsOffset(RHS, PtrBase, DL, Nodes))
811 return nullptr;
812
813 // We know we can re-write this as
814 // ((gep Ptr, OFFSET1) cmp (gep Ptr, OFFSET2)
815 // Since we've only looked through inbouds GEPs we know that we
816 // can't have overflow on either side. We can therefore re-write
817 // this as:
818 // OFFSET1 cmp OFFSET2
819 Value *NewRHS = rewriteGEPAsOffset(RHS, PtrBase, DL, Nodes);
820
821 // RewriteGEPAsOffset has replaced RHS and all of its uses with a re-written
822 // GEP having PtrBase as the pointer base, and has returned in NewRHS the
823 // offset. Since Index is the offset of LHS to the base pointer, we will now
824 // compare the offsets instead of comparing the pointers.
825 return new ICmpInst(ICmpInst::getSignedPredicate(Cond), Index, NewRHS);
826}
827
828/// Fold comparisons between a GEP instruction and something else. At this point
829/// we know that the GEP is on the LHS of the comparison.
830Instruction *InstCombinerImpl::foldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
831 ICmpInst::Predicate Cond,
832 Instruction &I) {
833 // Don't transform signed compares of GEPs into index compares. Even if the
834 // GEP is inbounds, the final add of the base pointer can have signed overflow
835 // and would change the result of the icmp.
836 // e.g. "&foo[0] <s &foo[1]" can't be folded to "true" because "foo" could be
837 // the maximum signed value for the pointer type.
838 if (ICmpInst::isSigned(Cond))
839 return nullptr;
840
841 // Look through bitcasts and addrspacecasts. We do not however want to remove
842 // 0 GEPs.
843 if (!isa<GetElementPtrInst>(RHS))
844 RHS = RHS->stripPointerCasts();
845
846 Value *PtrBase = GEPLHS->getOperand(0);
847 // FIXME: Support vector pointer GEPs.
848 if (PtrBase == RHS && GEPLHS->isInBounds() &&
849 !GEPLHS->getType()->isVectorTy()) {
850 // ((gep Ptr, OFFSET) cmp Ptr) ---> (OFFSET cmp 0).
851 // This transformation (ignoring the base and scales) is valid because we
852 // know pointers can't overflow since the gep is inbounds. See if we can
853 // output an optimized form.
854 Value *Offset = evaluateGEPOffsetExpression(GEPLHS, *this, DL);
855
856 // If not, synthesize the offset the hard way.
857 if (!Offset)
858 Offset = EmitGEPOffset(GEPLHS);
859 return new ICmpInst(ICmpInst::getSignedPredicate(Cond), Offset,
860 Constant::getNullValue(Offset->getType()));
861 }
862
863 if (GEPLHS->isInBounds() && ICmpInst::isEquality(Cond) &&
864 isa<Constant>(RHS) && cast<Constant>(RHS)->isNullValue() &&
865 !NullPointerIsDefined(I.getFunction(),
866 RHS->getType()->getPointerAddressSpace())) {
867 // For most address spaces, an allocation can't be placed at null, but null
868 // itself is treated as a 0 size allocation in the in bounds rules. Thus,
869 // the only valid inbounds address derived from null, is null itself.
870 // Thus, we have four cases to consider:
871 // 1) Base == nullptr, Offset == 0 -> inbounds, null
872 // 2) Base == nullptr, Offset != 0 -> poison as the result is out of bounds
873 // 3) Base != nullptr, Offset == (-base) -> poison (crossing allocations)
874 // 4) Base != nullptr, Offset != (-base) -> nonnull (and possibly poison)
875 //
876 // (Note if we're indexing a type of size 0, that simply collapses into one
877 // of the buckets above.)
878 //
879 // In general, we're allowed to make values less poison (i.e. remove
880 // sources of full UB), so in this case, we just select between the two
881 // non-poison cases (1 and 4 above).
882 //
883 // For vectors, we apply the same reasoning on a per-lane basis.
884 auto *Base = GEPLHS->getPointerOperand();
885 if (GEPLHS->getType()->isVectorTy() && Base->getType()->isPointerTy()) {
886 auto EC = cast<VectorType>(GEPLHS->getType())->getElementCount();
887 Base = Builder.CreateVectorSplat(EC, Base);
888 }
889 return new ICmpInst(Cond, Base,
890 ConstantExpr::getPointerBitCastOrAddrSpaceCast(
891 cast<Constant>(RHS), Base->getType()));
892 } else if (GEPOperator *GEPRHS = dyn_cast<GEPOperator>(RHS)) {
893 // If the base pointers are different, but the indices are the same, just
894 // compare the base pointer.
895 if (PtrBase != GEPRHS->getOperand(0)) {
896 bool IndicesTheSame = GEPLHS->getNumOperands()==GEPRHS->getNumOperands();
897 IndicesTheSame &= GEPLHS->getOperand(0)->getType() ==
898 GEPRHS->getOperand(0)->getType();
899 if (IndicesTheSame)
900 for (unsigned i = 1, e = GEPLHS->getNumOperands(); i != e; ++i)
901 if (GEPLHS->getOperand(i) != GEPRHS->getOperand(i)) {
902 IndicesTheSame = false;
903 break;
904 }
905
906 // If all indices are the same, just compare the base pointers.
907 Type *BaseType = GEPLHS->getOperand(0)->getType();
908 if (IndicesTheSame && CmpInst::makeCmpResultType(BaseType) == I.getType())
909 return new ICmpInst(Cond, GEPLHS->getOperand(0), GEPRHS->getOperand(0));
910
911 // If we're comparing GEPs with two base pointers that only differ in type
912 // and both GEPs have only constant indices or just one use, then fold
913 // the compare with the adjusted indices.
914 // FIXME: Support vector of pointers.
915 if (GEPLHS->isInBounds() && GEPRHS->isInBounds() &&
916 (GEPLHS->hasAllConstantIndices() || GEPLHS->hasOneUse()) &&
917 (GEPRHS->hasAllConstantIndices() || GEPRHS->hasOneUse()) &&
918 PtrBase->stripPointerCasts() ==
919 GEPRHS->getOperand(0)->stripPointerCasts() &&
920 !GEPLHS->getType()->isVectorTy()) {
921 Value *LOffset = EmitGEPOffset(GEPLHS);
922 Value *ROffset = EmitGEPOffset(GEPRHS);
923
924 // If we looked through an addrspacecast between different sized address
925 // spaces, the LHS and RHS pointers are different sized
926 // integers. Truncate to the smaller one.
927 Type *LHSIndexTy = LOffset->getType();
928 Type *RHSIndexTy = ROffset->getType();
929 if (LHSIndexTy != RHSIndexTy) {
930 if (LHSIndexTy->getPrimitiveSizeInBits().getFixedSize() <
931 RHSIndexTy->getPrimitiveSizeInBits().getFixedSize()) {
932 ROffset = Builder.CreateTrunc(ROffset, LHSIndexTy);
933 } else
934 LOffset = Builder.CreateTrunc(LOffset, RHSIndexTy);
935 }
936
937 Value *Cmp = Builder.CreateICmp(ICmpInst::getSignedPredicate(Cond),
938 LOffset, ROffset);
939 return replaceInstUsesWith(I, Cmp);
940 }
941
942 // Otherwise, the base pointers are different and the indices are
943 // different. Try convert this to an indexed compare by looking through
944 // PHIs/casts.
945 return transformToIndexedCompare(GEPLHS, RHS, Cond, DL);
946 }
947
948 // If one of the GEPs has all zero indices, recurse.
949 // FIXME: Handle vector of pointers.
950 if (!GEPLHS->getType()->isVectorTy() && GEPLHS->hasAllZeroIndices())
951 return foldGEPICmp(GEPRHS, GEPLHS->getOperand(0),
952 ICmpInst::getSwappedPredicate(Cond), I);
953
954 // If the other GEP has all zero indices, recurse.
955 // FIXME: Handle vector of pointers.
956 if (!GEPRHS->getType()->isVectorTy() && GEPRHS->hasAllZeroIndices())
957 return foldGEPICmp(GEPLHS, GEPRHS->getOperand(0), Cond, I);
958
959 bool GEPsInBounds = GEPLHS->isInBounds() && GEPRHS->isInBounds();
960 if (GEPLHS->getNumOperands() == GEPRHS->getNumOperands()) {
961 // If the GEPs only differ by one index, compare it.
962 unsigned NumDifferences = 0; // Keep track of # differences.
963 unsigned DiffOperand = 0; // The operand that differs.
964 for (unsigned i = 1, e = GEPRHS->getNumOperands(); i != e; ++i)
965 if (GEPLHS->getOperand(i) != GEPRHS->getOperand(i)) {
966 Type *LHSType = GEPLHS->getOperand(i)->getType();
967 Type *RHSType = GEPRHS->getOperand(i)->getType();
968 // FIXME: Better support for vector of pointers.
969 if (LHSType->getPrimitiveSizeInBits() !=
970 RHSType->getPrimitiveSizeInBits() ||
971 (GEPLHS->getType()->isVectorTy() &&
972 (!LHSType->isVectorTy() || !RHSType->isVectorTy()))) {
973 // Irreconcilable differences.
974 NumDifferences = 2;
975 break;
976 }
977
978 if (NumDifferences++) break;
979 DiffOperand = i;
980 }
981
982 if (NumDifferences == 0) // SAME GEP?
983 return replaceInstUsesWith(I, // No comparison is needed here.
984 ConstantInt::get(I.getType(), ICmpInst::isTrueWhenEqual(Cond)));
985
986 else if (NumDifferences == 1 && GEPsInBounds) {
987 Value *LHSV = GEPLHS->getOperand(DiffOperand);
988 Value *RHSV = GEPRHS->getOperand(DiffOperand);
989 // Make sure we do a signed comparison here.
990 return new ICmpInst(ICmpInst::getSignedPredicate(Cond), LHSV, RHSV);
991 }
992 }
993
994 // Only lower this if the icmp is the only user of the GEP or if we expect
995 // the result to fold to a constant!
996 if (GEPsInBounds && (isa<ConstantExpr>(GEPLHS) || GEPLHS->hasOneUse()) &&
997 (isa<ConstantExpr>(GEPRHS) || GEPRHS->hasOneUse())) {
998 // ((gep Ptr, OFFSET1) cmp (gep Ptr, OFFSET2) ---> (OFFSET1 cmp OFFSET2)
999 Value *L = EmitGEPOffset(GEPLHS);
1000 Value *R = EmitGEPOffset(GEPRHS);
1001 return new ICmpInst(ICmpInst::getSignedPredicate(Cond), L, R);
1002 }
1003 }
1004
1005 // Try convert this to an indexed compare by looking through PHIs/casts as a
1006 // last resort.
1007 return transformToIndexedCompare(GEPLHS, RHS, Cond, DL);
1008}
1009
1010Instruction *InstCombinerImpl::foldAllocaCmp(ICmpInst &ICI,
1011 const AllocaInst *Alloca,
1012 const Value *Other) {
1013 assert(ICI.isEquality() && "Cannot fold non-equality comparison.")((void)0);
1014
1015 // It would be tempting to fold away comparisons between allocas and any
1016 // pointer not based on that alloca (e.g. an argument). However, even
1017 // though such pointers cannot alias, they can still compare equal.
1018 //
1019 // But LLVM doesn't specify where allocas get their memory, so if the alloca
1020 // doesn't escape we can argue that it's impossible to guess its value, and we
1021 // can therefore act as if any such guesses are wrong.
1022 //
1023 // The code below checks that the alloca doesn't escape, and that it's only
1024 // used in a comparison once (the current instruction). The
1025 // single-comparison-use condition ensures that we're trivially folding all
1026 // comparisons against the alloca consistently, and avoids the risk of
1027 // erroneously folding a comparison of the pointer with itself.
1028
1029 unsigned MaxIter = 32; // Break cycles and bound to constant-time.
1030
1031 SmallVector<const Use *, 32> Worklist;
1032 for (const Use &U : Alloca->uses()) {
1033 if (Worklist.size() >= MaxIter)
1034 return nullptr;
1035 Worklist.push_back(&U);
1036 }
1037
1038 unsigned NumCmps = 0;
1039 while (!Worklist.empty()) {
1040 assert(Worklist.size() <= MaxIter)((void)0);
1041 const Use *U = Worklist.pop_back_val();
1042 const Value *V = U->getUser();
1043 --MaxIter;
1044
1045 if (isa<BitCastInst>(V) || isa<GetElementPtrInst>(V) || isa<PHINode>(V) ||
1046 isa<SelectInst>(V)) {
1047 // Track the uses.
1048 } else if (isa<LoadInst>(V)) {
1049 // Loading from the pointer doesn't escape it.
1050 continue;
1051 } else if (const auto *SI = dyn_cast<StoreInst>(V)) {
1052 // Storing *to* the pointer is fine, but storing the pointer escapes it.
1053 if (SI->getValueOperand() == U->get())
1054 return nullptr;
1055 continue;
1056 } else if (isa<ICmpInst>(V)) {
1057 if (NumCmps++)
1058 return nullptr; // Found more than one cmp.
1059 continue;
1060 } else if (const auto *Intrin = dyn_cast<IntrinsicInst>(V)) {
1061 switch (Intrin->getIntrinsicID()) {
1062 // These intrinsics don't escape or compare the pointer. Memset is safe
1063 // because we don't allow ptrtoint. Memcpy and memmove are safe because
1064 // we don't allow stores, so src cannot point to V.
1065 case Intrinsic::lifetime_start: case Intrinsic::lifetime_end:
1066 case Intrinsic::memcpy: case Intrinsic::memmove: case Intrinsic::memset:
1067 continue;
1068 default:
1069 return nullptr;
1070 }
1071 } else {
1072 return nullptr;
1073 }
1074 for (const Use &U : V->uses()) {
1075 if (Worklist.size() >= MaxIter)
1076 return nullptr;
1077 Worklist.push_back(&U);
1078 }
1079 }
1080
1081 Type *CmpTy = CmpInst::makeCmpResultType(Other->getType());
1082 return replaceInstUsesWith(
1083 ICI,
1084 ConstantInt::get(CmpTy, !CmpInst::isTrueWhenEqual(ICI.getPredicate())));
1085}
1086
1087/// Fold "icmp pred (X+C), X".
1088Instruction *InstCombinerImpl::foldICmpAddOpConst(Value *X, const APInt &C,
1089 ICmpInst::Predicate Pred) {
1090 // From this point on, we know that (X+C <= X) --> (X+C < X) because C != 0,
1091 // so the values can never be equal. Similarly for all other "or equals"
1092 // operators.
1093 assert(!!C && "C should not be zero!")((void)0);
1094
1095 // (X+1) <u X --> X >u (MAXUINT-1) --> X == 255
1096 // (X+2) <u X --> X >u (MAXUINT-2) --> X > 253
1097 // (X+MAXUINT) <u X --> X >u (MAXUINT-MAXUINT) --> X != 0
1098 if (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_ULE) {
1099 Constant *R = ConstantInt::get(X->getType(),
1100 APInt::getMaxValue(C.getBitWidth()) - C);
1101 return new ICmpInst(ICmpInst::ICMP_UGT, X, R);
1102 }
1103
1104 // (X+1) >u X --> X <u (0-1) --> X != 255
1105 // (X+2) >u X --> X <u (0-2) --> X <u 254
1106 // (X+MAXUINT) >u X --> X <u (0-MAXUINT) --> X <u 1 --> X == 0
1107 if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_UGE)
1108 return new ICmpInst(ICmpInst::ICMP_ULT, X,
1109 ConstantInt::get(X->getType(), -C));
1110
1111 APInt SMax = APInt::getSignedMaxValue(C.getBitWidth());
1112
1113 // (X+ 1) <s X --> X >s (MAXSINT-1) --> X == 127
1114 // (X+ 2) <s X --> X >s (MAXSINT-2) --> X >s 125
1115 // (X+MAXSINT) <s X --> X >s (MAXSINT-MAXSINT) --> X >s 0
1116 // (X+MINSINT) <s X --> X >s (MAXSINT-MINSINT) --> X >s -1
1117 // (X+ -2) <s X --> X >s (MAXSINT- -2) --> X >s 126
1118 // (X+ -1) <s X --> X >s (MAXSINT- -1) --> X != 127
1119 if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE)
1120 return new ICmpInst(ICmpInst::ICMP_SGT, X,
1121 ConstantInt::get(X->getType(), SMax - C));
1122
1123 // (X+ 1) >s X --> X <s (MAXSINT-(1-1)) --> X != 127
1124 // (X+ 2) >s X --> X <s (MAXSINT-(2-1)) --> X <s 126
1125 // (X+MAXSINT) >s X --> X <s (MAXSINT-(MAXSINT-1)) --> X <s 1
1126 // (X+MINSINT) >s X --> X <s (MAXSINT-(MINSINT-1)) --> X <s -2
1127 // (X+ -2) >s X --> X <s (MAXSINT-(-2-1)) --> X <s -126
1128 // (X+ -1) >s X --> X <s (MAXSINT-(-1-1)) --> X == -128
1129
1130 assert(Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE)((void)0);
1131 return new ICmpInst(ICmpInst::ICMP_SLT, X,
1132 ConstantInt::get(X->getType(), SMax - (C - 1)));
1133}
1134
1135/// Handle "(icmp eq/ne (ashr/lshr AP2, A), AP1)" ->
1136/// (icmp eq/ne A, Log2(AP2/AP1)) ->
1137/// (icmp eq/ne A, Log2(AP2) - Log2(AP1)).
1138Instruction *InstCombinerImpl::foldICmpShrConstConst(ICmpInst &I, Value *A,
1139 const APInt &AP1,
1140 const APInt &AP2) {
1141 assert(I.isEquality() && "Cannot fold icmp gt/lt")((void)0);
1142
1143 auto getICmp = [&I](CmpInst::Predicate Pred, Value *LHS, Value *RHS) {
1144 if (I.getPredicate() == I.ICMP_NE)
1145 Pred = CmpInst::getInversePredicate(Pred);
1146 return new ICmpInst(Pred, LHS, RHS);
1147 };
1148
1149 // Don't bother doing any work for cases which InstSimplify handles.
1150 if (AP2.isNullValue())
1151 return nullptr;
1152
1153 bool IsAShr = isa<AShrOperator>(I.getOperand(0));
1154 if (IsAShr) {
1155 if (AP2.isAllOnesValue())
1156 return nullptr;
1157 if (AP2.isNegative() != AP1.isNegative())
1158 return nullptr;
1159 if (AP2.sgt(AP1))
1160 return nullptr;
1161 }
1162
1163 if (!AP1)
1164 // 'A' must be large enough to shift out the highest set bit.
1165 return getICmp(I.ICMP_UGT, A,
1166 ConstantInt::get(A->getType(), AP2.logBase2()));
1167
1168 if (AP1 == AP2)
1169 return getICmp(I.ICMP_EQ, A, ConstantInt::getNullValue(A->getType()));
1170
1171 int Shift;
1172 if (IsAShr && AP1.isNegative())
1173 Shift = AP1.countLeadingOnes() - AP2.countLeadingOnes();
1174 else
1175 Shift = AP1.countLeadingZeros() - AP2.countLeadingZeros();
1176
1177 if (Shift > 0) {
1178 if (IsAShr && AP1 == AP2.ashr(Shift)) {
1179 // There are multiple solutions if we are comparing against -1 and the LHS
1180 // of the ashr is not a power of two.
1181 if (AP1.isAllOnesValue() && !AP2.isPowerOf2())
1182 return getICmp(I.ICMP_UGE, A, ConstantInt::get(A->getType(), Shift));
1183 return getICmp(I.ICMP_EQ, A, ConstantInt::get(A->getType(), Shift));
1184 } else if (AP1 == AP2.lshr(Shift)) {
1185 return getICmp(I.ICMP_EQ, A, ConstantInt::get(A->getType(), Shift));
1186 }
1187 }
1188
1189 // Shifting const2 will never be equal to const1.
1190 // FIXME: This should always be handled by InstSimplify?
1191 auto *TorF = ConstantInt::get(I.getType(), I.getPredicate() == I.ICMP_NE);
1192 return replaceInstUsesWith(I, TorF);
1193}
1194
1195/// Handle "(icmp eq/ne (shl AP2, A), AP1)" ->
1196/// (icmp eq/ne A, TrailingZeros(AP1) - TrailingZeros(AP2)).
1197Instruction *InstCombinerImpl::foldICmpShlConstConst(ICmpInst &I, Value *A,
1198 const APInt &AP1,
1199 const APInt &AP2) {
1200 assert(I.isEquality() && "Cannot fold icmp gt/lt")((void)0);
1201
1202 auto getICmp = [&I](CmpInst::Predicate Pred, Value *LHS, Value *RHS) {
1203 if (I.getPredicate() == I.ICMP_NE)
1204 Pred = CmpInst::getInversePredicate(Pred);
1205 return new ICmpInst(Pred, LHS, RHS);
1206 };
1207
1208 // Don't bother doing any work for cases which InstSimplify handles.
1209 if (AP2.isNullValue())
1210 return nullptr;
1211
1212 unsigned AP2TrailingZeros = AP2.countTrailingZeros();
1213
1214 if (!AP1 && AP2TrailingZeros != 0)
1215 return getICmp(
1216 I.ICMP_UGE, A,
1217 ConstantInt::get(A->getType(), AP2.getBitWidth() - AP2TrailingZeros));
1218
1219 if (AP1 == AP2)
1220 return getICmp(I.ICMP_EQ, A, ConstantInt::getNullValue(A->getType()));
1221
1222 // Get the distance between the lowest bits that are set.
1223 int Shift = AP1.countTrailingZeros() - AP2TrailingZeros;
1224
1225 if (Shift > 0 && AP2.shl(Shift) == AP1)
1226 return getICmp(I.ICMP_EQ, A, ConstantInt::get(A->getType(), Shift));
1227
1228 // Shifting const2 will never be equal to const1.
1229 // FIXME: This should always be handled by InstSimplify?
1230 auto *TorF = ConstantInt::get(I.getType(), I.getPredicate() == I.ICMP_NE);
1231 return replaceInstUsesWith(I, TorF);
1232}
1233
1234/// The caller has matched a pattern of the form:
1235/// I = icmp ugt (add (add A, B), CI2), CI1
1236/// If this is of the form:
1237/// sum = a + b
1238/// if (sum+128 >u 255)
1239/// Then replace it with llvm.sadd.with.overflow.i8.
1240///
1241static Instruction *processUGT_ADDCST_ADD(ICmpInst &I, Value *A, Value *B,
1242 ConstantInt *CI2, ConstantInt *CI1,
1243 InstCombinerImpl &IC) {
1244 // The transformation we're trying to do here is to transform this into an
1245 // llvm.sadd.with.overflow. To do this, we have to replace the original add
1246 // with a narrower add, and discard the add-with-constant that is part of the
1247 // range check (if we can't eliminate it, this isn't profitable).
1248
1249 // In order to eliminate the add-with-constant, the compare can be its only
1250 // use.
1251 Instruction *AddWithCst = cast<Instruction>(I.getOperand(0));
1252 if (!AddWithCst->hasOneUse())
1253 return nullptr;
1254
1255 // If CI2 is 2^7, 2^15, 2^31, then it might be an sadd.with.overflow.
1256 if (!CI2->getValue().isPowerOf2())
1257 return nullptr;
1258 unsigned NewWidth = CI2->getValue().countTrailingZeros();
1259 if (NewWidth != 7 && NewWidth != 15 && NewWidth != 31)
1260 return nullptr;
1261
1262 // The width of the new add formed is 1 more than the bias.
1263 ++NewWidth;
1264
1265 // Check to see that CI1 is an all-ones value with NewWidth bits.
1266 if (CI1->getBitWidth() == NewWidth ||
1267 CI1->getValue() != APInt::getLowBitsSet(CI1->getBitWidth(), NewWidth))
1268 return nullptr;
1269
1270 // This is only really a signed overflow check if the inputs have been
1271 // sign-extended; check for that condition. For example, if CI2 is 2^31 and
1272 // the operands of the add are 64 bits wide, we need at least 33 sign bits.
1273 unsigned NeededSignBits = CI1->getBitWidth() - NewWidth + 1;
1274 if (IC.ComputeNumSignBits(A, 0, &I) < NeededSignBits ||
1275 IC.ComputeNumSignBits(B, 0, &I) < NeededSignBits)
1276 return nullptr;
1277
1278 // In order to replace the original add with a narrower
1279 // llvm.sadd.with.overflow, the only uses allowed are the add-with-constant
1280 // and truncates that discard the high bits of the add. Verify that this is
1281 // the case.
1282 Instruction *OrigAdd = cast<Instruction>(AddWithCst->getOperand(0));
1283 for (User *U : OrigAdd->users()) {
1284 if (U == AddWithCst)
1285 continue;
1286
1287 // Only accept truncates for now. We would really like a nice recursive
1288 // predicate like SimplifyDemandedBits, but which goes downwards the use-def
1289 // chain to see which bits of a value are actually demanded. If the
1290 // original add had another add which was then immediately truncated, we
1291 // could still do the transformation.
1292 TruncInst *TI = dyn_cast<TruncInst>(U);
1293 if (!TI || TI->getType()->getPrimitiveSizeInBits() > NewWidth)
1294 return nullptr;
1295 }
1296
1297 // If the pattern matches, truncate the inputs to the narrower type and
1298 // use the sadd_with_overflow intrinsic to efficiently compute both the
1299 // result and the overflow bit.
1300 Type *NewType = IntegerType::get(OrigAdd->getContext(), NewWidth);
1301 Function *F = Intrinsic::getDeclaration(
1302 I.getModule(), Intrinsic::sadd_with_overflow, NewType);
1303
1304 InstCombiner::BuilderTy &Builder = IC.Builder;
1305
1306 // Put the new code above the original add, in case there are any uses of the
1307 // add between the add and the compare.
1308 Builder.SetInsertPoint(OrigAdd);
1309
1310 Value *TruncA = Builder.CreateTrunc(A, NewType, A->getName() + ".trunc");
1311 Value *TruncB = Builder.CreateTrunc(B, NewType, B->getName() + ".trunc");
1312 CallInst *Call = Builder.CreateCall(F, {TruncA, TruncB}, "sadd");
1313 Value *Add = Builder.CreateExtractValue(Call, 0, "sadd.result");
1314 Value *ZExt = Builder.CreateZExt(Add, OrigAdd->getType());
1315
1316 // The inner add was the result of the narrow add, zero extended to the
1317 // wider type. Replace it with the result computed by the intrinsic.
1318 IC.replaceInstUsesWith(*OrigAdd, ZExt);
1319 IC.eraseInstFromFunction(*OrigAdd);
1320
1321 // The original icmp gets replaced with the overflow value.
1322 return ExtractValueInst::Create(Call, 1, "sadd.overflow");
1323}
1324
1325/// If we have:
1326/// icmp eq/ne (urem/srem %x, %y), 0
1327/// iff %y is a power-of-two, we can replace this with a bit test:
1328/// icmp eq/ne (and %x, (add %y, -1)), 0
1329Instruction *InstCombinerImpl::foldIRemByPowerOfTwoToBitTest(ICmpInst &I) {
1330 // This fold is only valid for equality predicates.
1331 if (!I.isEquality())
1332 return nullptr;
1333 ICmpInst::Predicate Pred;
1334 Value *X, *Y, *Zero;
1335 if (!match(&I, m_ICmp(Pred, m_OneUse(m_IRem(m_Value(X), m_Value(Y))),
1336 m_CombineAnd(m_Zero(), m_Value(Zero)))))
1337 return nullptr;
1338 if (!isKnownToBeAPowerOfTwo(Y, /*OrZero*/ true, 0, &I))
1339 return nullptr;
1340 // This may increase instruction count, we don't enforce that Y is a constant.
1341 Value *Mask = Builder.CreateAdd(Y, Constant::getAllOnesValue(Y->getType()));
1342 Value *Masked = Builder.CreateAnd(X, Mask);
1343 return ICmpInst::Create(Instruction::ICmp, Pred, Masked, Zero);
1344}
1345
1346/// Fold equality-comparison between zero and any (maybe truncated) right-shift
1347/// by one-less-than-bitwidth into a sign test on the original value.
1348Instruction *InstCombinerImpl::foldSignBitTest(ICmpInst &I) {
1349 Instruction *Val;
1350 ICmpInst::Predicate Pred;
1351 if (!I.isEquality() || !match(&I, m_ICmp(Pred, m_Instruction(Val), m_Zero())))
1352 return nullptr;
1353
1354 Value *X;
1355 Type *XTy;
1356
1357 Constant *C;
1358 if (match(Val, m_TruncOrSelf(m_Shr(m_Value(X), m_Constant(C))))) {
1359 XTy = X->getType();
1360 unsigned XBitWidth = XTy->getScalarSizeInBits();
1361 if (!match(C, m_SpecificInt_ICMP(ICmpInst::Predicate::ICMP_EQ,
1362 APInt(XBitWidth, XBitWidth - 1))))
1363 return nullptr;
1364 } else if (isa<BinaryOperator>(Val) &&
1365 (X = reassociateShiftAmtsOfTwoSameDirectionShifts(
1366 cast<BinaryOperator>(Val), SQ.getWithInstruction(Val),
1367 /*AnalyzeForSignBitExtraction=*/true))) {
1368 XTy = X->getType();
1369 } else
1370 return nullptr;
1371
1372 return ICmpInst::Create(Instruction::ICmp,
1373 Pred == ICmpInst::ICMP_EQ ? ICmpInst::ICMP_SGE
1374 : ICmpInst::ICMP_SLT,
1375 X, ConstantInt::getNullValue(XTy));
1376}
1377
1378// Handle icmp pred X, 0
1379Instruction *InstCombinerImpl::foldICmpWithZero(ICmpInst &Cmp) {
1380 CmpInst::Predicate Pred = Cmp.getPredicate();
1381 if (!match(Cmp.getOperand(1), m_Zero()))
1382 return nullptr;
1383
1384 // (icmp sgt smin(PosA, B) 0) -> (icmp sgt B 0)
1385 if (Pred == ICmpInst::ICMP_SGT) {
1386 Value *A, *B;
1387 SelectPatternResult SPR = matchSelectPattern(Cmp.getOperand(0), A, B);
1388 if (SPR.Flavor == SPF_SMIN) {
1389 if (isKnownPositive(A, DL, 0, &AC, &Cmp, &DT))
1390 return new ICmpInst(Pred, B, Cmp.getOperand(1));
1391 if (isKnownPositive(B, DL, 0, &AC, &Cmp, &DT))
1392 return new ICmpInst(Pred, A, Cmp.getOperand(1));
1393 }
1394 }
1395
1396 if (Instruction *New = foldIRemByPowerOfTwoToBitTest(Cmp))
1397 return New;
1398
1399 // Given:
1400 // icmp eq/ne (urem %x, %y), 0
1401 // Iff %x has 0 or 1 bits set, and %y has at least 2 bits set, omit 'urem':
1402 // icmp eq/ne %x, 0
1403 Value *X, *Y;
1404 if (match(Cmp.getOperand(0), m_URem(m_Value(X), m_Value(Y))) &&
1405 ICmpInst::isEquality(Pred)) {
1406 KnownBits XKnown = computeKnownBits(X, 0, &Cmp);
1407 KnownBits YKnown = computeKnownBits(Y, 0, &Cmp);
1408 if (XKnown.countMaxPopulation() == 1 && YKnown.countMinPopulation() >= 2)
1409 return new ICmpInst(Pred, X, Cmp.getOperand(1));
1410 }
1411
1412 return nullptr;
1413}
1414
1415/// Fold icmp Pred X, C.
1416/// TODO: This code structure does not make sense. The saturating add fold
1417/// should be moved to some other helper and extended as noted below (it is also
1418/// possible that code has been made unnecessary - do we canonicalize IR to
1419/// overflow/saturating intrinsics or not?).
1420Instruction *InstCombinerImpl::foldICmpWithConstant(ICmpInst &Cmp) {
1421 // Match the following pattern, which is a common idiom when writing
1422 // overflow-safe integer arithmetic functions. The source performs an addition
1423 // in wider type and explicitly checks for overflow using comparisons against
1424 // INT_MIN and INT_MAX. Simplify by using the sadd_with_overflow intrinsic.
1425 //
1426 // TODO: This could probably be generalized to handle other overflow-safe
1427 // operations if we worked out the formulas to compute the appropriate magic
1428 // constants.
1429 //
1430 // sum = a + b
1431 // if (sum+128 >u 255) ... -> llvm.sadd.with.overflow.i8
1432 CmpInst::Predicate Pred = Cmp.getPredicate();
1433 Value *Op0 = Cmp.getOperand(0), *Op1 = Cmp.getOperand(1);
1434 Value *A, *B;
1435 ConstantInt *CI, *CI2; // I = icmp ugt (add (add A, B), CI2), CI
1436 if (Pred == ICmpInst::ICMP_UGT && match(Op1, m_ConstantInt(CI)) &&
1437 match(Op0, m_Add(m_Add(m_Value(A), m_Value(B)), m_ConstantInt(CI2))))
1438 if (Instruction *Res = processUGT_ADDCST_ADD(Cmp, A, B, CI2, CI, *this))
1439 return Res;
1440
1441 // icmp(phi(C1, C2, ...), C) -> phi(icmp(C1, C), icmp(C2, C), ...).
1442 Constant *C = dyn_cast<Constant>(Op1);
1443 if (!C || C->canTrap())
1444 return nullptr;
1445
1446 if (auto *Phi = dyn_cast<PHINode>(Op0))
1447 if (all_of(Phi->operands(), [](Value *V) { return isa<Constant>(V); })) {
1448 Type *Ty = Cmp.getType();
1449 Builder.SetInsertPoint(Phi);
1450 PHINode *NewPhi =
1451 Builder.CreatePHI(Ty, Phi->getNumOperands());
1452 for (BasicBlock *Predecessor : predecessors(Phi->getParent())) {
1453 auto *Input =
1454 cast<Constant>(Phi->getIncomingValueForBlock(Predecessor));
1455 auto *BoolInput = ConstantExpr::getCompare(Pred, Input, C);
1456 NewPhi->addIncoming(BoolInput, Predecessor);
1457 }
1458 NewPhi->takeName(&Cmp);
1459 return replaceInstUsesWith(Cmp, NewPhi);
1460 }
1461
1462 return nullptr;
1463}
1464
1465/// Canonicalize icmp instructions based on dominating conditions.
1466Instruction *InstCombinerImpl::foldICmpWithDominatingICmp(ICmpInst &Cmp) {
1467 // This is a cheap/incomplete check for dominance - just match a single
1468 // predecessor with a conditional branch.
1469 BasicBlock *CmpBB = Cmp.getParent();
1470 BasicBlock *DomBB = CmpBB->getSinglePredecessor();
1471 if (!DomBB)
1472 return nullptr;
1473
1474 Value *DomCond;
1475 BasicBlock *TrueBB, *FalseBB;
1476 if (!match(DomBB->getTerminator(), m_Br(m_Value(DomCond), TrueBB, FalseBB)))
1477 return nullptr;
1478
1479 assert((TrueBB == CmpBB || FalseBB == CmpBB) &&((void)0)
1480 "Predecessor block does not point to successor?")((void)0);
1481
1482 // The branch should get simplified. Don't bother simplifying this condition.
1483 if (TrueBB == FalseBB)
1484 return nullptr;
1485
1486 // Try to simplify this compare to T/F based on the dominating condition.
1487 Optional<bool> Imp = isImpliedCondition(DomCond, &Cmp, DL, TrueBB == CmpBB);
1488 if (Imp)
1489 return replaceInstUsesWith(Cmp, ConstantInt::get(Cmp.getType(), *Imp));
1490
1491 CmpInst::Predicate Pred = Cmp.getPredicate();
1492 Value *X = Cmp.getOperand(0), *Y = Cmp.getOperand(1);
1493 ICmpInst::Predicate DomPred;
1494 const APInt *C, *DomC;
1495 if (match(DomCond, m_ICmp(DomPred, m_Specific(X), m_APInt(DomC))) &&
1496 match(Y, m_APInt(C))) {
1497 // We have 2 compares of a variable with constants. Calculate the constant
1498 // ranges of those compares to see if we can transform the 2nd compare:
1499 // DomBB:
1500 // DomCond = icmp DomPred X, DomC
1501 // br DomCond, CmpBB, FalseBB
1502 // CmpBB:
1503 // Cmp = icmp Pred X, C
1504 ConstantRange CR = ConstantRange::makeExactICmpRegion(Pred, *C);
1505 ConstantRange DominatingCR =
1506 (CmpBB == TrueBB) ? ConstantRange::makeExactICmpRegion(DomPred, *DomC)
1507 : ConstantRange::makeExactICmpRegion(
1508 CmpInst::getInversePredicate(DomPred), *DomC);
1509 ConstantRange Intersection = DominatingCR.intersectWith(CR);
1510 ConstantRange Difference = DominatingCR.difference(CR);
1511 if (Intersection.isEmptySet())
1512 return replaceInstUsesWith(Cmp, Builder.getFalse());
1513 if (Difference.isEmptySet())
1514 return replaceInstUsesWith(Cmp, Builder.getTrue());
1515
1516 // Canonicalizing a sign bit comparison that gets used in a branch,
1517 // pessimizes codegen by generating branch on zero instruction instead
1518 // of a test and branch. So we avoid canonicalizing in such situations
1519 // because test and branch instruction has better branch displacement
1520 // than compare and branch instruction.
1521 bool UnusedBit;
1522 bool IsSignBit = isSignBitCheck(Pred, *C, UnusedBit);
1523 if (Cmp.isEquality() || (IsSignBit && hasBranchUse(Cmp)))
1524 return nullptr;
1525
1526 // Avoid an infinite loop with min/max canonicalization.
1527 // TODO: This will be unnecessary if we canonicalize to min/max intrinsics.
1528 if (Cmp.hasOneUse() &&
1529 match(Cmp.user_back(), m_MaxOrMin(m_Value(), m_Value())))
1530 return nullptr;
1531
1532 if (const APInt *EqC = Intersection.getSingleElement())
1533 return new ICmpInst(ICmpInst::ICMP_EQ, X, Builder.getInt(*EqC));
1534 if (const APInt *NeC = Difference.getSingleElement())
1535 return new ICmpInst(ICmpInst::ICMP_NE, X, Builder.getInt(*NeC));
1536 }
1537
1538 return nullptr;
1539}
1540
1541/// Fold icmp (trunc X, Y), C.
1542Instruction *InstCombinerImpl::foldICmpTruncConstant(ICmpInst &Cmp,
1543 TruncInst *Trunc,
1544 const APInt &C) {
1545 ICmpInst::Predicate Pred = Cmp.getPredicate();
1546 Value *X = Trunc->getOperand(0);
1547 if (C.isOneValue() && C.getBitWidth() > 1) {
1548 // icmp slt trunc(signum(V)) 1 --> icmp slt V, 1
1549 Value *V = nullptr;
1550 if (Pred == ICmpInst::ICMP_SLT && match(X, m_Signum(m_Value(V))))
1551 return new ICmpInst(ICmpInst::ICMP_SLT, V,
1552 ConstantInt::get(V->getType(), 1));
1553 }
1554
1555 unsigned DstBits = Trunc->getType()->getScalarSizeInBits(),
1556 SrcBits = X->getType()->getScalarSizeInBits();
1557 if (Cmp.isEquality() && Trunc->hasOneUse()) {
1558 // Simplify icmp eq (trunc x to i8), 42 -> icmp eq x, 42|highbits if all
1559 // of the high bits truncated out of x are known.
1560 KnownBits Known = computeKnownBits(X, 0, &Cmp);
1561
1562 // If all the high bits are known, we can do this xform.
1563 if ((Known.Zero | Known.One).countLeadingOnes() >= SrcBits - DstBits) {
1564 // Pull in the high bits from known-ones set.
1565 APInt NewRHS = C.zext(SrcBits);
1566 NewRHS |= Known.One & APInt::getHighBitsSet(SrcBits, SrcBits - DstBits);
1567 return new ICmpInst(Pred, X, ConstantInt::get(X->getType(), NewRHS));
1568 }
1569 }
1570
1571 // Look through truncated right-shift of the sign-bit for a sign-bit check:
1572 // trunc iN (ShOp >> ShAmtC) to i[N - ShAmtC] < 0 --> ShOp < 0
1573 // trunc iN (ShOp >> ShAmtC) to i[N - ShAmtC] > -1 --> ShOp > -1
1574 Value *ShOp;
1575 const APInt *ShAmtC;
1576 bool TrueIfSigned;
1577 if (isSignBitCheck(Pred, C, TrueIfSigned) &&
1578 match(X, m_Shr(m_Value(ShOp), m_APInt(ShAmtC))) &&
1579 DstBits == SrcBits - ShAmtC->getZExtValue()) {
1580 return TrueIfSigned
1581 ? new ICmpInst(ICmpInst::ICMP_SLT, ShOp,
1582 ConstantInt::getNullValue(X->getType()))
1583 : new ICmpInst(ICmpInst::ICMP_SGT, ShOp,
1584 ConstantInt::getAllOnesValue(X->getType()));
1585 }
1586
1587 return nullptr;
1588}
1589
1590/// Fold icmp (xor X, Y), C.
1591Instruction *InstCombinerImpl::foldICmpXorConstant(ICmpInst &Cmp,
1592 BinaryOperator *Xor,
1593 const APInt &C) {
1594 Value *X = Xor->getOperand(0);
1595 Value *Y = Xor->getOperand(1);
1596 const APInt *XorC;
1597 if (!match(Y, m_APInt(XorC)))
1598 return nullptr;
1599
1600 // If this is a comparison that tests the signbit (X < 0) or (x > -1),
1601 // fold the xor.
1602 ICmpInst::Predicate Pred = Cmp.getPredicate();
1603 bool TrueIfSigned = false;
1604 if (isSignBitCheck(Cmp.getPredicate(), C, TrueIfSigned)) {
1605
1606 // If the sign bit of the XorCst is not set, there is no change to
1607 // the operation, just stop using the Xor.
1608 if (!XorC->isNegative())
1609 return replaceOperand(Cmp, 0, X);
1610
1611 // Emit the opposite comparison.
1612 if (TrueIfSigned)
1613 return new ICmpInst(ICmpInst::ICMP_SGT, X,
1614 ConstantInt::getAllOnesValue(X->getType()));
1615 else
1616 return new ICmpInst(ICmpInst::ICMP_SLT, X,
1617 ConstantInt::getNullValue(X->getType()));
1618 }
1619
1620 if (Xor->hasOneUse()) {
1621 // (icmp u/s (xor X SignMask), C) -> (icmp s/u X, (xor C SignMask))
1622 if (!Cmp.isEquality() && XorC->isSignMask()) {
1623 Pred = Cmp.getFlippedSignednessPredicate();
1624 return new ICmpInst(Pred, X, ConstantInt::get(X->getType(), C ^ *XorC));
1625 }
1626
1627 // (icmp u/s (xor X ~SignMask), C) -> (icmp s/u X, (xor C ~SignMask))
1628 if (!Cmp.isEquality() && XorC->isMaxSignedValue()) {
1629 Pred = Cmp.getFlippedSignednessPredicate();
1630 Pred = Cmp.getSwappedPredicate(Pred);
1631 return new ICmpInst(Pred, X, ConstantInt::get(X->getType(), C ^ *XorC));
1632 }
1633 }
1634
1635 // Mask constant magic can eliminate an 'xor' with unsigned compares.
1636 if (Pred == ICmpInst::ICMP_UGT) {
1637 // (xor X, ~C) >u C --> X <u ~C (when C+1 is a power of 2)
1638 if (*XorC == ~C && (C + 1).isPowerOf2())
1639 return new ICmpInst(ICmpInst::ICMP_ULT, X, Y);
1640 // (xor X, C) >u C --> X >u C (when C+1 is a power of 2)
1641 if (*XorC == C && (C + 1).isPowerOf2())
1642 return new ICmpInst(ICmpInst::ICMP_UGT, X, Y);
1643 }
1644 if (Pred == ICmpInst::ICMP_ULT) {
1645 // (xor X, -C) <u C --> X >u ~C (when C is a power of 2)
1646 if (*XorC == -C && C.isPowerOf2())
1647 return new ICmpInst(ICmpInst::ICMP_UGT, X,
1648 ConstantInt::get(X->getType(), ~C));
1649 // (xor X, C) <u C --> X >u ~C (when -C is a power of 2)
1650 if (*XorC == C && (-C).isPowerOf2())
1651 return new ICmpInst(ICmpInst::ICMP_UGT, X,
1652 ConstantInt::get(X->getType(), ~C));
1653 }
1654 return nullptr;
1655}
1656
1657/// Fold icmp (and (sh X, Y), C2), C1.
1658Instruction *InstCombinerImpl::foldICmpAndShift(ICmpInst &Cmp,
1659 BinaryOperator *And,
1660 const APInt &C1,
1661 const APInt &C2) {
1662 BinaryOperator *Shift = dyn_cast<BinaryOperator>(And->getOperand(0));
1663 if (!Shift || !Shift->isShift())
1664 return nullptr;
1665
1666 // If this is: (X >> C3) & C2 != C1 (where any shift and any compare could
1667 // exist), turn it into (X & (C2 << C3)) != (C1 << C3). This happens a LOT in
1668 // code produced by the clang front-end, for bitfield access.
1669 // This seemingly simple opportunity to fold away a shift turns out to be
1670 // rather complicated. See PR17827 for details.
1671 unsigned ShiftOpcode = Shift->getOpcode();
1672 bool IsShl = ShiftOpcode == Instruction::Shl;
1673 const APInt *C3;
1674 if (match(Shift->getOperand(1), m_APInt(C3))) {
1675 APInt NewAndCst, NewCmpCst;
1676 bool AnyCmpCstBitsShiftedOut;
1677 if (ShiftOpcode == Instruction::Shl) {
1678 // For a left shift, we can fold if the comparison is not signed. We can
1679 // also fold a signed comparison if the mask value and comparison value
1680 // are not negative. These constraints may not be obvious, but we can
1681 // prove that they are correct using an SMT solver.
1682 if (Cmp.isSigned() && (C2.isNegative() || C1.isNegative()))
1683 return nullptr;
1684
1685 NewCmpCst = C1.lshr(*C3);
1686 NewAndCst = C2.lshr(*C3);
1687 AnyCmpCstBitsShiftedOut = NewCmpCst.shl(*C3) != C1;
1688 } else if (ShiftOpcode == Instruction::LShr) {
1689 // For a logical right shift, we can fold if the comparison is not signed.
1690 // We can also fold a signed comparison if the shifted mask value and the
1691 // shifted comparison value are not negative. These constraints may not be
1692 // obvious, but we can prove that they are correct using an SMT solver.
1693 NewCmpCst = C1.shl(*C3);
1694 NewAndCst = C2.shl(*C3);
1695 AnyCmpCstBitsShiftedOut = NewCmpCst.lshr(*C3) != C1;
1696 if (Cmp.isSigned() && (NewAndCst.isNegative() || NewCmpCst.isNegative()))
1697 return nullptr;
1698 } else {
1699 // For an arithmetic shift, check that both constants don't use (in a
1700 // signed sense) the top bits being shifted out.
1701 assert(ShiftOpcode == Instruction::AShr && "Unknown shift opcode")((void)0);
1702 NewCmpCst = C1.shl(*C3);
1703 NewAndCst = C2.shl(*C3);
1704 AnyCmpCstBitsShiftedOut = NewCmpCst.ashr(*C3) != C1;
1705 if (NewAndCst.ashr(*C3) != C2)
1706 return nullptr;
1707 }
1708
1709 if (AnyCmpCstBitsShiftedOut) {
1710 // If we shifted bits out, the fold is not going to work out. As a
1711 // special case, check to see if this means that the result is always
1712 // true or false now.
1713 if (Cmp.getPredicate() == ICmpInst::ICMP_EQ)
1714 return replaceInstUsesWith(Cmp, ConstantInt::getFalse(Cmp.getType()));
1715 if (Cmp.getPredicate() == ICmpInst::ICMP_NE)
1716 return replaceInstUsesWith(Cmp, ConstantInt::getTrue(Cmp.getType()));
1717 } else {
1718 Value *NewAnd = Builder.CreateAnd(
1719 Shift->getOperand(0), ConstantInt::get(And->getType(), NewAndCst));
1720 return new ICmpInst(Cmp.getPredicate(),
1721 NewAnd, ConstantInt::get(And->getType(), NewCmpCst));
1722 }
1723 }
1724
1725 // Turn ((X >> Y) & C2) == 0 into (X & (C2 << Y)) == 0. The latter is
1726 // preferable because it allows the C2 << Y expression to be hoisted out of a
1727 // loop if Y is invariant and X is not.
1728 if (Shift->hasOneUse() && C1.isNullValue() && Cmp.isEquality() &&
1729 !Shift->isArithmeticShift() && !isa<Constant>(Shift->getOperand(0))) {
1730 // Compute C2 << Y.
1731 Value *NewShift =
1732 IsShl ? Builder.CreateLShr(And->getOperand(1), Shift->getOperand(1))
1733 : Builder.CreateShl(And->getOperand(1), Shift->getOperand(1));
1734
1735 // Compute X & (C2 << Y).
1736 Value *NewAnd = Builder.CreateAnd(Shift->getOperand(0), NewShift);
1737 return replaceOperand(Cmp, 0, NewAnd);
1738 }
1739
1740 return nullptr;
1741}
1742
1743/// Fold icmp (and X, C2), C1.
1744Instruction *InstCombinerImpl::foldICmpAndConstConst(ICmpInst &Cmp,
1745 BinaryOperator *And,
1746 const APInt &C1) {
1747 bool isICMP_NE = Cmp.getPredicate() == ICmpInst::ICMP_NE;
1748
1749 // For vectors: icmp ne (and X, 1), 0 --> trunc X to N x i1
1750 // TODO: We canonicalize to the longer form for scalars because we have
1751 // better analysis/folds for icmp, and codegen may be better with icmp.
1752 if (isICMP_NE && Cmp.getType()->isVectorTy() && C1.isNullValue() &&
1753 match(And->getOperand(1), m_One()))
1754 return new TruncInst(And->getOperand(0), Cmp.getType());
1755
1756 const APInt *C2;
1757 Value *X;
1758 if (!match(And, m_And(m_Value(X), m_APInt(C2))))
1759 return nullptr;
1760
1761 // Don't perform the following transforms if the AND has multiple uses
1762 if (!And->hasOneUse())
1763 return nullptr;
1764
1765 if (Cmp.isEquality() && C1.isNullValue()) {
1766 // Restrict this fold to single-use 'and' (PR10267).
1767 // Replace (and X, (1 << size(X)-1) != 0) with X s< 0
1768 if (C2->isSignMask()) {
1769 Constant *Zero = Constant::getNullValue(X->getType());
1770 auto NewPred = isICMP_NE ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_SGE;
1771 return new ICmpInst(NewPred, X, Zero);
1772 }
1773
1774 // Restrict this fold only for single-use 'and' (PR10267).
1775 // ((%x & C) == 0) --> %x u< (-C) iff (-C) is power of two.
1776 if ((~(*C2) + 1).isPowerOf2()) {
1777 Constant *NegBOC =
1778 ConstantExpr::getNeg(cast<Constant>(And->getOperand(1)));
1779 auto NewPred = isICMP_NE ? ICmpInst::ICMP_UGE : ICmpInst::ICMP_ULT;
1780 return new ICmpInst(NewPred, X, NegBOC);
1781 }
1782 }
1783
1784 // If the LHS is an 'and' of a truncate and we can widen the and/compare to
1785 // the input width without changing the value produced, eliminate the cast:
1786 //
1787 // icmp (and (trunc W), C2), C1 -> icmp (and W, C2'), C1'
1788 //
1789 // We can do this transformation if the constants do not have their sign bits
1790 // set or if it is an equality comparison. Extending a relational comparison
1791 // when we're checking the sign bit would not work.
1792 Value *W;
1793 if (match(And->getOperand(0), m_OneUse(m_Trunc(m_Value(W)))) &&
1794 (Cmp.isEquality() || (!C1.isNegative() && !C2->isNegative()))) {
1795 // TODO: Is this a good transform for vectors? Wider types may reduce
1796 // throughput. Should this transform be limited (even for scalars) by using
1797 // shouldChangeType()?
1798 if (!Cmp.getType()->isVectorTy()) {
1799 Type *WideType = W->getType();
1800 unsigned WideScalarBits = WideType->getScalarSizeInBits();
1801 Constant *ZextC1 = ConstantInt::get(WideType, C1.zext(WideScalarBits));
1802 Constant *ZextC2 = ConstantInt::get(WideType, C2->zext(WideScalarBits));
1803 Value *NewAnd = Builder.CreateAnd(W, ZextC2, And->getName());
1804 return new ICmpInst(Cmp.getPredicate(), NewAnd, ZextC1);
1805 }
1806 }
1807
1808 if (Instruction *I = foldICmpAndShift(Cmp, And, C1, *C2))
1809 return I;
1810
1811 // (icmp pred (and (or (lshr A, B), A), 1), 0) -->
1812 // (icmp pred (and A, (or (shl 1, B), 1), 0))
1813 //
1814 // iff pred isn't signed
1815 if (!Cmp.isSigned() && C1.isNullValue() && And->getOperand(0)->hasOneUse() &&
1816 match(And->getOperand(1), m_One())) {
1817 Constant *One = cast<Constant>(And->getOperand(1));
1818 Value *Or = And->getOperand(0);
1819 Value *A, *B, *LShr;
1820 if (match(Or, m_Or(m_Value(LShr), m_Value(A))) &&
1821 match(LShr, m_LShr(m_Specific(A), m_Value(B)))) {
1822 unsigned UsesRemoved = 0;
1823 if (And->hasOneUse())
1824 ++UsesRemoved;
1825 if (Or->hasOneUse())
1826 ++UsesRemoved;
1827 if (LShr->hasOneUse())
1828 ++UsesRemoved;
1829
1830 // Compute A & ((1 << B) | 1)
1831 Value *NewOr = nullptr;
1832 if (auto *C = dyn_cast<Constant>(B)) {
1833 if (UsesRemoved >= 1)
1834 NewOr = ConstantExpr::getOr(ConstantExpr::getNUWShl(One, C), One);
1835 } else {
1836 if (UsesRemoved >= 3)
1837 NewOr = Builder.CreateOr(Builder.CreateShl(One, B, LShr->getName(),
1838 /*HasNUW=*/true),
1839 One, Or->getName());
1840 }
1841 if (NewOr) {
1842 Value *NewAnd = Builder.CreateAnd(A, NewOr, And->getName());
1843 return replaceOperand(Cmp, 0, NewAnd);
1844 }
1845 }
1846 }
1847
1848 return nullptr;
1849}
1850
1851/// Fold icmp (and X, Y), C.
1852Instruction *InstCombinerImpl::foldICmpAndConstant(ICmpInst &Cmp,
1853 BinaryOperator *And,
1854 const APInt &C) {
1855 if (Instruction *I = foldICmpAndConstConst(Cmp, And, C))
1856 return I;
1857
1858 const ICmpInst::Predicate Pred = Cmp.getPredicate();
1859 bool TrueIfNeg;
1860 if (isSignBitCheck(Pred, C, TrueIfNeg)) {
1861 // ((X - 1) & ~X) < 0 --> X == 0
1862 // ((X - 1) & ~X) >= 0 --> X != 0
1863 Value *X;
1864 if (match(And->getOperand(0), m_Add(m_Value(X), m_AllOnes())) &&
1865 match(And->getOperand(1), m_Not(m_Specific(X)))) {
1866 auto NewPred = TrueIfNeg ? CmpInst::ICMP_EQ : CmpInst::ICMP_NE;
1867 return new ICmpInst(NewPred, X, ConstantInt::getNullValue(X->getType()));
1868 }
1869 }
1870
1871 // TODO: These all require that Y is constant too, so refactor with the above.
1872
1873 // Try to optimize things like "A[i] & 42 == 0" to index computations.
1874 Value *X = And->getOperand(0);
1875 Value *Y = And->getOperand(1);
1876 if (auto *LI = dyn_cast<LoadInst>(X))
1877 if (auto *GEP = dyn_cast<GetElementPtrInst>(LI->getOperand(0)))
1878 if (auto *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0)))
1879 if (GV->isConstant() && GV->hasDefinitiveInitializer() &&
1880 !LI->isVolatile() && isa<ConstantInt>(Y)) {
1881 ConstantInt *C2 = cast<ConstantInt>(Y);
1882 if (Instruction *Res = foldCmpLoadFromIndexedGlobal(GEP, GV, Cmp, C2))
1883 return Res;
1884 }
1885
1886 if (!Cmp.isEquality())
1887 return nullptr;
1888
1889 // X & -C == -C -> X > u ~C
1890 // X & -C != -C -> X <= u ~C
1891 // iff C is a power of 2
1892 if (Cmp.getOperand(1) == Y && (-C).isPowerOf2()) {
1893 auto NewPred =
1894 Pred == CmpInst::ICMP_EQ ? CmpInst::ICMP_UGT : CmpInst::ICMP_ULE;
1895 return new ICmpInst(NewPred, X, SubOne(cast<Constant>(Cmp.getOperand(1))));
1896 }
1897
1898 // (X & C2) == 0 -> (trunc X) >= 0
1899 // (X & C2) != 0 -> (trunc X) < 0
1900 // iff C2 is a power of 2 and it masks the sign bit of a legal integer type.
1901 const APInt *C2;
1902 if (And->hasOneUse() && C.isNullValue() && match(Y, m_APInt(C2))) {
1903 int32_t ExactLogBase2 = C2->exactLogBase2();
1904 if (ExactLogBase2 != -1 && DL.isLegalInteger(ExactLogBase2 + 1)) {
1905 Type *NTy = IntegerType::get(Cmp.getContext(), ExactLogBase2 + 1);
1906 if (auto *AndVTy = dyn_cast<VectorType>(And->getType()))
1907 NTy = VectorType::get(NTy, AndVTy->getElementCount());
1908 Value *Trunc = Builder.CreateTrunc(X, NTy);
1909 auto NewPred =
1910 Pred == CmpInst::ICMP_EQ ? CmpInst::ICMP_SGE : CmpInst::ICMP_SLT;
1911 return new ICmpInst(NewPred, Trunc, Constant::getNullValue(NTy));
1912 }
1913 }
1914
1915 return nullptr;
1916}
1917
1918/// Fold icmp (or X, Y), C.
1919Instruction *InstCombinerImpl::foldICmpOrConstant(ICmpInst &Cmp,
1920 BinaryOperator *Or,
1921 const APInt &C) {
1922 ICmpInst::Predicate Pred = Cmp.getPredicate();
1923 if (C.isOneValue()) {
1924 // icmp slt signum(V) 1 --> icmp slt V, 1
1925 Value *V = nullptr;
1926 if (Pred == ICmpInst::ICMP_SLT && match(Or, m_Signum(m_Value(V))))
1927 return new ICmpInst(ICmpInst::ICMP_SLT, V,
1928 ConstantInt::get(V->getType(), 1));
1929 }
1930
1931 Value *OrOp0 = Or->getOperand(0), *OrOp1 = Or->getOperand(1);
1932 const APInt *MaskC;
1933 if (match(OrOp1, m_APInt(MaskC)) && Cmp.isEquality()) {
1934 if (*MaskC == C && (C + 1).isPowerOf2()) {
1935 // X | C == C --> X <=u C
1936 // X | C != C --> X >u C
1937 // iff C+1 is a power of 2 (C is a bitmask of the low bits)
1938 Pred = (Pred == CmpInst::ICMP_EQ) ? CmpInst::ICMP_ULE : CmpInst::ICMP_UGT;
1939 return new ICmpInst(Pred, OrOp0, OrOp1);
1940 }
1941
1942 // More general: canonicalize 'equality with set bits mask' to
1943 // 'equality with clear bits mask'.
1944 // (X | MaskC) == C --> (X & ~MaskC) == C ^ MaskC
1945 // (X | MaskC) != C --> (X & ~MaskC) != C ^ MaskC
1946 if (Or->hasOneUse()) {
1947 Value *And = Builder.CreateAnd(OrOp0, ~(*MaskC));
1948 Constant *NewC = ConstantInt::get(Or->getType(), C ^ (*MaskC));
1949 return new ICmpInst(Pred, And, NewC);
1950 }
1951 }
1952
1953 if (!Cmp.isEquality() || !C.isNullValue() || !Or->hasOneUse())
1954 return nullptr;
1955
1956 Value *P, *Q;
1957 if (match(Or, m_Or(m_PtrToInt(m_Value(P)), m_PtrToInt(m_Value(Q))))) {
1958 // Simplify icmp eq (or (ptrtoint P), (ptrtoint Q)), 0
1959 // -> and (icmp eq P, null), (icmp eq Q, null).
1960 Value *CmpP =
1961 Builder.CreateICmp(Pred, P, ConstantInt::getNullValue(P->getType()));
1962 Value *CmpQ =
1963 Builder.CreateICmp(Pred, Q, ConstantInt::getNullValue(Q->getType()));
1964 auto BOpc = Pred == CmpInst::ICMP_EQ ? Instruction::And : Instruction::Or;
1965 return BinaryOperator::Create(BOpc, CmpP, CmpQ);
1966 }
1967
1968 // Are we using xors to bitwise check for a pair of (in)equalities? Convert to
1969 // a shorter form that has more potential to be folded even further.
1970 Value *X1, *X2, *X3, *X4;
1971 if (match(OrOp0, m_OneUse(m_Xor(m_Value(X1), m_Value(X2)))) &&
1972 match(OrOp1, m_OneUse(m_Xor(m_Value(X3), m_Value(X4))))) {
1973 // ((X1 ^ X2) || (X3 ^ X4)) == 0 --> (X1 == X2) && (X3 == X4)
1974 // ((X1 ^ X2) || (X3 ^ X4)) != 0 --> (X1 != X2) || (X3 != X4)
1975 Value *Cmp12 = Builder.CreateICmp(Pred, X1, X2);
1976 Value *Cmp34 = Builder.CreateICmp(Pred, X3, X4);
1977 auto BOpc = Pred == CmpInst::ICMP_EQ ? Instruction::And : Instruction::Or;
1978 return BinaryOperator::Create(BOpc, Cmp12, Cmp34);
1979 }
1980
1981 return nullptr;
1982}
1983
1984/// Fold icmp (mul X, Y), C.
1985Instruction *InstCombinerImpl::foldICmpMulConstant(ICmpInst &Cmp,
1986 BinaryOperator *Mul,
1987 const APInt &C) {
1988 const APInt *MulC;
1989 if (!match(Mul->getOperand(1), m_APInt(MulC)))
1990 return nullptr;
1991
1992 // If this is a test of the sign bit and the multiply is sign-preserving with
1993 // a constant operand, use the multiply LHS operand instead.
1994 ICmpInst::Predicate Pred = Cmp.getPredicate();
1995 if (isSignTest(Pred, C) && Mul->hasNoSignedWrap()) {
1996 if (MulC->isNegative())
1997 Pred = ICmpInst::getSwappedPredicate(Pred);
1998 return new ICmpInst(Pred, Mul->getOperand(0),
1999 Constant::getNullValue(Mul->getType()));
2000 }
2001
2002 // If the multiply does not wrap, try to divide the compare constant by the
2003 // multiplication factor.
2004 if (Cmp.isEquality() && !MulC->isNullValue()) {
2005 // (mul nsw X, MulC) == C --> X == C /s MulC
2006 if (Mul->hasNoSignedWrap() && C.srem(*MulC).isNullValue()) {
2007 Constant *NewC = ConstantInt::get(Mul->getType(), C.sdiv(*MulC));
2008 return new ICmpInst(Pred, Mul->getOperand(0), NewC);
2009 }
2010 // (mul nuw X, MulC) == C --> X == C /u MulC
2011 if (Mul->hasNoUnsignedWrap() && C.urem(*MulC).isNullValue()) {
2012 Constant *NewC = ConstantInt::get(Mul->getType(), C.udiv(*MulC));
2013 return new ICmpInst(Pred, Mul->getOperand(0), NewC);
2014 }
2015 }
2016
2017 return nullptr;
2018}
2019
2020/// Fold icmp (shl 1, Y), C.
2021static Instruction *foldICmpShlOne(ICmpInst &Cmp, Instruction *Shl,
2022 const APInt &C) {
2023 Value *Y;
2024 if (!match(Shl, m_Shl(m_One(), m_Value(Y))))
2025 return nullptr;
2026
2027 Type *ShiftType = Shl->getType();
2028 unsigned TypeBits = C.getBitWidth();
2029 bool CIsPowerOf2 = C.isPowerOf2();
2030 ICmpInst::Predicate Pred = Cmp.getPredicate();
2031 if (Cmp.isUnsigned()) {
2032 // (1 << Y) pred C -> Y pred Log2(C)
2033 if (!CIsPowerOf2) {
2034 // (1 << Y) < 30 -> Y <= 4
2035 // (1 << Y) <= 30 -> Y <= 4
2036 // (1 << Y) >= 30 -> Y > 4
2037 // (1 << Y) > 30 -> Y > 4
2038 if (Pred == ICmpInst::ICMP_ULT)
2039 Pred = ICmpInst::ICMP_ULE;
2040 else if (Pred == ICmpInst::ICMP_UGE)
2041 Pred = ICmpInst::ICMP_UGT;
2042 }
2043
2044 // (1 << Y) >= 2147483648 -> Y >= 31 -> Y == 31
2045 // (1 << Y) < 2147483648 -> Y < 31 -> Y != 31
2046 unsigned CLog2 = C.logBase2();
2047 if (CLog2 == TypeBits - 1) {
2048 if (Pred == ICmpInst::ICMP_UGE)
2049 Pred = ICmpInst::ICMP_EQ;
2050 else if (Pred == ICmpInst::ICMP_ULT)
2051 Pred = ICmpInst::ICMP_NE;
2052 }
2053 return new ICmpInst(Pred, Y, ConstantInt::get(ShiftType, CLog2));
2054 } else if (Cmp.isSigned()) {
2055 Constant *BitWidthMinusOne = ConstantInt::get(ShiftType, TypeBits - 1);
2056 if (C.isAllOnesValue()) {
2057 // (1 << Y) <= -1 -> Y == 31
2058 if (Pred == ICmpInst::ICMP_SLE)
2059 return new ICmpInst(ICmpInst::ICMP_EQ, Y, BitWidthMinusOne);
2060
2061 // (1 << Y) > -1 -> Y != 31
2062 if (Pred == ICmpInst::ICMP_SGT)
2063 return new ICmpInst(ICmpInst::ICMP_NE, Y, BitWidthMinusOne);
2064 } else if (!C) {
2065 // (1 << Y) < 0 -> Y == 31
2066 // (1 << Y) <= 0 -> Y == 31
2067 if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE)
2068 return new ICmpInst(ICmpInst::ICMP_EQ, Y, BitWidthMinusOne);
2069
2070 // (1 << Y) >= 0 -> Y != 31
2071 // (1 << Y) > 0 -> Y != 31
2072 if (Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE)
2073 return new ICmpInst(ICmpInst::ICMP_NE, Y, BitWidthMinusOne);
2074 }
2075 } else if (Cmp.isEquality() && CIsPowerOf2) {
2076 return new ICmpInst(Pred, Y, ConstantInt::get(ShiftType, C.logBase2()));
2077 }
2078
2079 return nullptr;
2080}
2081
2082/// Fold icmp (shl X, Y), C.
2083Instruction *InstCombinerImpl::foldICmpShlConstant(ICmpInst &Cmp,
2084 BinaryOperator *Shl,
2085 const APInt &C) {
2086 const APInt *ShiftVal;
2087 if (Cmp.isEquality() && match(Shl->getOperand(0), m_APInt(ShiftVal)))
2088 return foldICmpShlConstConst(Cmp, Shl->getOperand(1), C, *ShiftVal);
2089
2090 const APInt *ShiftAmt;
2091 if (!match(Shl->getOperand(1), m_APInt(ShiftAmt)))
2092 return foldICmpShlOne(Cmp, Shl, C);
2093
2094 // Check that the shift amount is in range. If not, don't perform undefined
2095 // shifts. When the shift is visited, it will be simplified.
2096 unsigned TypeBits = C.getBitWidth();
2097 if (ShiftAmt->uge(TypeBits))
2098 return nullptr;
2099
2100 ICmpInst::Predicate Pred = Cmp.getPredicate();
2101 Value *X = Shl->getOperand(0);
2102 Type *ShType = Shl->getType();
2103
2104 // NSW guarantees that we are only shifting out sign bits from the high bits,
2105 // so we can ASHR the compare constant without needing a mask and eliminate
2106 // the shift.
2107 if (Shl->hasNoSignedWrap()) {
2108 if (Pred == ICmpInst::ICMP_SGT) {
2109 // icmp Pred (shl nsw X, ShiftAmt), C --> icmp Pred X, (C >>s ShiftAmt)
2110 APInt ShiftedC = C.ashr(*ShiftAmt);
2111 return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
2112 }
2113 if ((Pred == ICmpInst::ICMP_EQ || Pred == ICmpInst::ICMP_NE) &&
2114 C.ashr(*ShiftAmt).shl(*ShiftAmt) == C) {
2115 APInt ShiftedC = C.ashr(*ShiftAmt);
2116 return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
2117 }
2118 if (Pred == ICmpInst::ICMP_SLT) {
2119 // SLE is the same as above, but SLE is canonicalized to SLT, so convert:
2120 // (X << S) <=s C is equiv to X <=s (C >> S) for all C
2121 // (X << S) <s (C + 1) is equiv to X <s (C >> S) + 1 if C <s SMAX
2122 // (X << S) <s C is equiv to X <s ((C - 1) >> S) + 1 if C >s SMIN
2123 assert(!C.isMinSignedValue() && "Unexpected icmp slt")((void)0);
2124 APInt ShiftedC = (C - 1).ashr(*ShiftAmt) + 1;
2125 return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
2126 }
2127 // If this is a signed comparison to 0 and the shift is sign preserving,
2128 // use the shift LHS operand instead; isSignTest may change 'Pred', so only
2129 // do that if we're sure to not continue on in this function.
2130 if (isSignTest(Pred, C))
2131 return new ICmpInst(Pred, X, Constant::getNullValue(ShType));
2132 }
2133
2134 // NUW guarantees that we are only shifting out zero bits from the high bits,
2135 // so we can LSHR the compare constant without needing a mask and eliminate
2136 // the shift.
2137 if (Shl->hasNoUnsignedWrap()) {
2138 if (Pred == ICmpInst::ICMP_UGT) {
2139 // icmp Pred (shl nuw X, ShiftAmt), C --> icmp Pred X, (C >>u ShiftAmt)
2140 APInt ShiftedC = C.lshr(*ShiftAmt);
2141 return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
2142 }
2143 if ((Pred == ICmpInst::ICMP_EQ || Pred == ICmpInst::ICMP_NE) &&
2144 C.lshr(*ShiftAmt).shl(*ShiftAmt) == C) {
2145 APInt ShiftedC = C.lshr(*ShiftAmt);
2146 return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
2147 }
2148 if (Pred == ICmpInst::ICMP_ULT) {
2149 // ULE is the same as above, but ULE is canonicalized to ULT, so convert:
2150 // (X << S) <=u C is equiv to X <=u (C >> S) for all C
2151 // (X << S) <u (C + 1) is equiv to X <u (C >> S) + 1 if C <u ~0u
2152 // (X << S) <u C is equiv to X <u ((C - 1) >> S) + 1 if C >u 0
2153 assert(C.ugt(0) && "ult 0 should have been eliminated")((void)0);
2154 APInt ShiftedC = (C - 1).lshr(*ShiftAmt) + 1;
2155 return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
2156 }
2157 }
2158
2159 if (Cmp.isEquality() && Shl->hasOneUse()) {
2160 // Strength-reduce the shift into an 'and'.
2161 Constant *Mask = ConstantInt::get(
2162 ShType,
2163 APInt::getLowBitsSet(TypeBits, TypeBits - ShiftAmt->getZExtValue()));
2164 Value *And = Builder.CreateAnd(X, Mask, Shl->getName() + ".mask");
2165 Constant *LShrC = ConstantInt::get(ShType, C.lshr(*ShiftAmt));
2166 return new ICmpInst(Pred, And, LShrC);
2167 }
2168
2169 // Otherwise, if this is a comparison of the sign bit, simplify to and/test.
2170 bool TrueIfSigned = false;
2171 if (Shl->hasOneUse() && isSignBitCheck(Pred, C, TrueIfSigned)) {
2172 // (X << 31) <s 0 --> (X & 1) != 0
2173 Constant *Mask = ConstantInt::get(
2174 ShType,
2175 APInt::getOneBitSet(TypeBits, TypeBits - ShiftAmt->getZExtValue() - 1));
2176 Value *And = Builder.CreateAnd(X, Mask, Shl->getName() + ".mask");
2177 return new ICmpInst(TrueIfSigned ? ICmpInst::ICMP_NE : ICmpInst::ICMP_EQ,
2178 And, Constant::getNullValue(ShType));
2179 }
2180
2181 // Simplify 'shl' inequality test into 'and' equality test.
2182 if (Cmp.isUnsigned() && Shl->hasOneUse()) {
2183 // (X l<< C2) u<=/u> C1 iff C1+1 is power of two -> X & (~C1 l>> C2) ==/!= 0
2184 if ((C + 1).isPowerOf2() &&
2185 (Pred == ICmpInst::ICMP_ULE || Pred == ICmpInst::ICMP_UGT)) {
2186 Value *And = Builder.CreateAnd(X, (~C).lshr(ShiftAmt->getZExtValue()));
2187 return new ICmpInst(Pred == ICmpInst::ICMP_ULE ? ICmpInst::ICMP_EQ
2188 : ICmpInst::ICMP_NE,
2189 And, Constant::getNullValue(ShType));
2190 }
2191 // (X l<< C2) u</u>= C1 iff C1 is power of two -> X & (-C1 l>> C2) ==/!= 0
2192 if (C.isPowerOf2() &&
2193 (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_UGE)) {
2194 Value *And =
2195 Builder.CreateAnd(X, (~(C - 1)).lshr(ShiftAmt->getZExtValue()));
2196 return new ICmpInst(Pred == ICmpInst::ICMP_ULT ? ICmpInst::ICMP_EQ
2197 : ICmpInst::ICMP_NE,
2198 And, Constant::getNullValue(ShType));
2199 }
2200 }
2201
2202 // Transform (icmp pred iM (shl iM %v, N), C)
2203 // -> (icmp pred i(M-N) (trunc %v iM to i(M-N)), (trunc (C>>N))
2204 // Transform the shl to a trunc if (trunc (C>>N)) has no loss and M-N.
2205 // This enables us to get rid of the shift in favor of a trunc that may be
2206 // free on the target. It has the additional benefit of comparing to a
2207 // smaller constant that may be more target-friendly.
2208 unsigned Amt = ShiftAmt->getLimitedValue(TypeBits - 1);
2209 if (Shl->hasOneUse() && Amt != 0 && C.countTrailingZeros() >= Amt &&
2210 DL.isLegalInteger(TypeBits - Amt)) {
2211 Type *TruncTy = IntegerType::get(Cmp.getContext(), TypeBits - Amt);
2212 if (auto *ShVTy = dyn_cast<VectorType>(ShType))
2213 TruncTy = VectorType::get(TruncTy, ShVTy->getElementCount());
2214 Constant *NewC =
2215 ConstantInt::get(TruncTy, C.ashr(*ShiftAmt).trunc(TypeBits - Amt));
2216 return new ICmpInst(Pred, Builder.CreateTrunc(X, TruncTy), NewC);
2217 }
2218
2219 return nullptr;
2220}
2221
2222/// Fold icmp ({al}shr X, Y), C.
2223Instruction *InstCombinerImpl::foldICmpShrConstant(ICmpInst &Cmp,
2224 BinaryOperator *Shr,
2225 const APInt &C) {
2226 // An exact shr only shifts out zero bits, so:
2227 // icmp eq/ne (shr X, Y), 0 --> icmp eq/ne X, 0
2228 Value *X = Shr->getOperand(0);
2229 CmpInst::Predicate Pred = Cmp.getPredicate();
2230 if (Cmp.isEquality() && Shr->isExact() && Shr->hasOneUse() &&
2231 C.isNullValue())
2232 return new ICmpInst(Pred, X, Cmp.getOperand(1));
2233
2234 const APInt *ShiftVal;
2235 if (Cmp.isEquality() && match(Shr->getOperand(0), m_APInt(ShiftVal)))
2236 return foldICmpShrConstConst(Cmp, Shr->getOperand(1), C, *ShiftVal);
2237
2238 const APInt *ShiftAmt;
2239 if (!match(Shr->getOperand(1), m_APInt(ShiftAmt)))
2240 return nullptr;
2241
2242 // Check that the shift amount is in range. If not, don't perform undefined
2243 // shifts. When the shift is visited it will be simplified.
2244 unsigned TypeBits = C.getBitWidth();
2245 unsigned ShAmtVal = ShiftAmt->getLimitedValue(TypeBits);
2246 if (ShAmtVal >= TypeBits || ShAmtVal == 0)
2247 return nullptr;
2248
2249 bool IsAShr = Shr->getOpcode() == Instruction::AShr;
2250 bool IsExact = Shr->isExact();
2251 Type *ShrTy = Shr->getType();
2252 // TODO: If we could guarantee that InstSimplify would handle all of the
2253 // constant-value-based preconditions in the folds below, then we could assert
2254 // those conditions rather than checking them. This is difficult because of
2255 // undef/poison (PR34838).
2256 if (IsAShr) {
2257 if (Pred == CmpInst::ICMP_SLT || (Pred == CmpInst::ICMP_SGT && IsExact)) {
2258 // icmp slt (ashr X, ShAmtC), C --> icmp slt X, (C << ShAmtC)
2259 // icmp sgt (ashr exact X, ShAmtC), C --> icmp sgt X, (C << ShAmtC)
2260 APInt ShiftedC = C.shl(ShAmtVal);
2261 if (ShiftedC.ashr(ShAmtVal) == C)
2262 return new ICmpInst(Pred, X, ConstantInt::get(ShrTy, ShiftedC));
2263 }
2264 if (Pred == CmpInst::ICMP_SGT) {
2265 // icmp sgt (ashr X, ShAmtC), C --> icmp sgt X, ((C + 1) << ShAmtC) - 1
2266 APInt ShiftedC = (C + 1).shl(ShAmtVal) - 1;
2267 if (!C.isMaxSignedValue() && !(C + 1).shl(ShAmtVal).isMinSignedValue() &&
2268 (ShiftedC + 1).ashr(ShAmtVal) == (C + 1))
2269 return new ICmpInst(Pred, X, ConstantInt::get(ShrTy, ShiftedC));
2270 }
2271
2272 // If the compare constant has significant bits above the lowest sign-bit,
2273 // then convert an unsigned cmp to a test of the sign-bit:
2274 // (ashr X, ShiftC) u> C --> X s< 0
2275 // (ashr X, ShiftC) u< C --> X s> -1
2276 if (C.getBitWidth() > 2 && C.getNumSignBits() <= ShAmtVal) {
2277 if (Pred == CmpInst::ICMP_UGT) {
2278 return new ICmpInst(CmpInst::ICMP_SLT, X,
2279 ConstantInt::getNullValue(ShrTy));
2280 }
2281 if (Pred == CmpInst::ICMP_ULT) {
2282 return new ICmpInst(CmpInst::ICMP_SGT, X,
2283 ConstantInt::getAllOnesValue(ShrTy));
2284 }
2285 }
2286 } else {
2287 if (Pred == CmpInst::ICMP_ULT || (Pred == CmpInst::ICMP_UGT && IsExact)) {
2288 // icmp ult (lshr X, ShAmtC), C --> icmp ult X, (C << ShAmtC)
2289 // icmp ugt (lshr exact X, ShAmtC), C --> icmp ugt X, (C << ShAmtC)
2290 APInt ShiftedC = C.shl(ShAmtVal);
2291 if (ShiftedC.lshr(ShAmtVal) == C)
2292 return new ICmpInst(Pred, X, ConstantInt::get(ShrTy, ShiftedC));
2293 }
2294 if (Pred == CmpInst::ICMP_UGT) {
2295 // icmp ugt (lshr X, ShAmtC), C --> icmp ugt X, ((C + 1) << ShAmtC) - 1
2296 APInt ShiftedC = (C + 1).shl(ShAmtVal) - 1;
2297 if ((ShiftedC + 1).lshr(ShAmtVal) == (C + 1))
2298 return new ICmpInst(Pred, X, ConstantInt::get(ShrTy, ShiftedC));
2299 }
2300 }
2301
2302 if (!Cmp.isEquality())
2303 return nullptr;
2304
2305 // Handle equality comparisons of shift-by-constant.
2306
2307 // If the comparison constant changes with the shift, the comparison cannot
2308 // succeed (bits of the comparison constant cannot match the shifted value).
2309 // This should be known by InstSimplify and already be folded to true/false.
2310 assert(((IsAShr && C.shl(ShAmtVal).ashr(ShAmtVal) == C) ||((void)0)
2311 (!IsAShr && C.shl(ShAmtVal).lshr(ShAmtVal) == C)) &&((void)0)
2312 "Expected icmp+shr simplify did not occur.")((void)0);
2313
2314 // If the bits shifted out are known zero, compare the unshifted value:
2315 // (X & 4) >> 1 == 2 --> (X & 4) == 4.
2316 if (Shr->isExact())
2317 return new ICmpInst(Pred, X, ConstantInt::get(ShrTy, C << ShAmtVal));
2318
2319 if (C.isNullValue()) {
2320 // == 0 is u< 1.
2321 if (Pred == CmpInst::ICMP_EQ)
2322 return new ICmpInst(CmpInst::ICMP_ULT, X,
2323 ConstantInt::get(ShrTy, (C + 1).shl(ShAmtVal)));
2324 else
2325 return new ICmpInst(CmpInst::ICMP_UGT, X,
2326 ConstantInt::get(ShrTy, (C + 1).shl(ShAmtVal) - 1));
2327 }
2328
2329 if (Shr->hasOneUse()) {
2330 // Canonicalize the shift into an 'and':
2331 // icmp eq/ne (shr X, ShAmt), C --> icmp eq/ne (and X, HiMask), (C << ShAmt)
2332 APInt Val(APInt::getHighBitsSet(TypeBits, TypeBits - ShAmtVal));
2333 Constant *Mask = ConstantInt::get(ShrTy, Val);
2334 Value *And = Builder.CreateAnd(X, Mask, Shr->getName() + ".mask");
2335 return new ICmpInst(Pred, And, ConstantInt::get(ShrTy, C << ShAmtVal));
2336 }
2337
2338 return nullptr;
2339}
2340
2341Instruction *InstCombinerImpl::foldICmpSRemConstant(ICmpInst &Cmp,
2342 BinaryOperator *SRem,
2343 const APInt &C) {
2344 // Match an 'is positive' or 'is negative' comparison of remainder by a
2345 // constant power-of-2 value:
2346 // (X % pow2C) sgt/slt 0
2347 const ICmpInst::Predicate Pred = Cmp.getPredicate();
2348 if (Pred != ICmpInst::ICMP_SGT && Pred != ICmpInst::ICMP_SLT)
2349 return nullptr;
2350
2351 // TODO: The one-use check is standard because we do not typically want to
2352 // create longer instruction sequences, but this might be a special-case
2353 // because srem is not good for analysis or codegen.
2354 if (!SRem->hasOneUse())
2355 return nullptr;
2356
2357 const APInt *DivisorC;
2358 if (!C.isNullValue() || !match(SRem->getOperand(1), m_Power2(DivisorC)))
2359 return nullptr;
2360
2361 // Mask off the sign bit and the modulo bits (low-bits).
2362 Type *Ty = SRem->getType();
2363 APInt SignMask = APInt::getSignMask(Ty->getScalarSizeInBits());
2364 Constant *MaskC = ConstantInt::get(Ty, SignMask | (*DivisorC - 1));
2365 Value *And = Builder.CreateAnd(SRem->getOperand(0), MaskC);
2366
2367 // For 'is positive?' check that the sign-bit is clear and at least 1 masked
2368 // bit is set. Example:
2369 // (i8 X % 32) s> 0 --> (X & 159) s> 0
2370 if (Pred == ICmpInst::ICMP_SGT)
2371 return new ICmpInst(ICmpInst::ICMP_SGT, And, ConstantInt::getNullValue(Ty));
2372
2373 // For 'is negative?' check that the sign-bit is set and at least 1 masked
2374 // bit is set. Example:
2375 // (i16 X % 4) s< 0 --> (X & 32771) u> 32768
2376 return new ICmpInst(ICmpInst::ICMP_UGT, And, ConstantInt::get(Ty, SignMask));
2377}
2378
2379/// Fold icmp (udiv X, Y), C.
2380Instruction *InstCombinerImpl::foldICmpUDivConstant(ICmpInst &Cmp,
2381 BinaryOperator *UDiv,
2382 const APInt &C) {
2383 const APInt *C2;
2384 if (!match(UDiv->getOperand(0), m_APInt(C2)))
2385 return nullptr;
2386
2387 assert(*C2 != 0 && "udiv 0, X should have been simplified already.")((void)0);
2388
2389 // (icmp ugt (udiv C2, Y), C) -> (icmp ule Y, C2/(C+1))
2390 Value *Y = UDiv->getOperand(1);
2391 if (Cmp.getPredicate() == ICmpInst::ICMP_UGT) {
2392 assert(!C.isMaxValue() &&((void)0)
2393 "icmp ugt X, UINT_MAX should have been simplified already.")((void)0);
2394 return new ICmpInst(ICmpInst::ICMP_ULE, Y,
2395 ConstantInt::get(Y->getType(), C2->udiv(C + 1)));
2396 }
2397
2398 // (icmp ult (udiv C2, Y), C) -> (icmp ugt Y, C2/C)
2399 if (Cmp.getPredicate() == ICmpInst::ICMP_ULT) {
2400 assert(C != 0 && "icmp ult X, 0 should have been simplified already.")((void)0);
2401 return new ICmpInst(ICmpInst::ICMP_UGT, Y,
2402 ConstantInt::get(Y->getType(), C2->udiv(C)));
2403 }
2404
2405 return nullptr;
2406}
2407
2408/// Fold icmp ({su}div X, Y), C.
2409Instruction *InstCombinerImpl::foldICmpDivConstant(ICmpInst &Cmp,
2410 BinaryOperator *Div,
2411 const APInt &C) {
2412 // Fold: icmp pred ([us]div X, C2), C -> range test
2413 // Fold this div into the comparison, producing a range check.
2414 // Determine, based on the divide type, what the range is being
2415 // checked. If there is an overflow on the low or high side, remember
2416 // it, otherwise compute the range [low, hi) bounding the new value.
2417 // See: InsertRangeTest above for the kinds of replacements possible.
2418 const APInt *C2;
2419 if (!match(Div->getOperand(1), m_APInt(C2)))
2420 return nullptr;
2421
2422 // FIXME: If the operand types don't match the type of the divide
2423 // then don't attempt this transform. The code below doesn't have the
2424 // logic to deal with a signed divide and an unsigned compare (and
2425 // vice versa). This is because (x /s C2) <s C produces different
2426 // results than (x /s C2) <u C or (x /u C2) <s C or even
2427 // (x /u C2) <u C. Simply casting the operands and result won't
2428 // work. :( The if statement below tests that condition and bails
2429 // if it finds it.
2430 bool DivIsSigned = Div->getOpcode() == Instruction::SDiv;
2431 if (!Cmp.isEquality() && DivIsSigned != Cmp.isSigned())
2432 return nullptr;
2433
2434 // The ProdOV computation fails on divide by 0 and divide by -1. Cases with
2435 // INT_MIN will also fail if the divisor is 1. Although folds of all these
2436 // division-by-constant cases should be present, we can not assert that they
2437 // have happened before we reach this icmp instruction.
2438 if (C2->isNullValue() || C2->isOneValue() ||
2439 (DivIsSigned && C2->isAllOnesValue()))
2440 return nullptr;
2441
2442 // Compute Prod = C * C2. We are essentially solving an equation of
2443 // form X / C2 = C. We solve for X by multiplying C2 and C.
2444 // By solving for X, we can turn this into a range check instead of computing
2445 // a divide.
2446 APInt Prod = C * *C2;
2447
2448 // Determine if the product overflows by seeing if the product is not equal to
2449 // the divide. Make sure we do the same kind of divide as in the LHS
2450 // instruction that we're folding.
2451 bool ProdOV = (DivIsSigned ? Prod.sdiv(*C2) : Prod.udiv(*C2)) != C;
2452
2453 ICmpInst::Predicate Pred = Cmp.getPredicate();
2454
2455 // If the division is known to be exact, then there is no remainder from the
2456 // divide, so the covered range size is unit, otherwise it is the divisor.
2457 APInt RangeSize = Div->isExact() ? APInt(C2->getBitWidth(), 1) : *C2;
2458
2459 // Figure out the interval that is being checked. For example, a comparison
2460 // like "X /u 5 == 0" is really checking that X is in the interval [0, 5).
2461 // Compute this interval based on the constants involved and the signedness of
2462 // the compare/divide. This computes a half-open interval, keeping track of
2463 // whether either value in the interval overflows. After analysis each
2464 // overflow variable is set to 0 if it's corresponding bound variable is valid
2465 // -1 if overflowed off the bottom end, or +1 if overflowed off the top end.
2466 int LoOverflow = 0, HiOverflow = 0;
2467 APInt LoBound, HiBound;
2468
2469 if (!DivIsSigned) { // udiv
2470 // e.g. X/5 op 3 --> [15, 20)
2471 LoBound = Prod;
2472 HiOverflow = LoOverflow = ProdOV;
2473 if (!HiOverflow) {
2474 // If this is not an exact divide, then many values in the range collapse
2475 // to the same result value.
2476 HiOverflow = addWithOverflow(HiBound, LoBound, RangeSize, false);
2477 }
2478 } else if (C2->isStrictlyPositive()) { // Divisor is > 0.
2479 if (C.isNullValue()) { // (X / pos) op 0
2480 // Can't overflow. e.g. X/2 op 0 --> [-1, 2)
2481 LoBound = -(RangeSize - 1);
2482 HiBound = RangeSize;
2483 } else if (C.isStrictlyPositive()) { // (X / pos) op pos
2484 LoBound = Prod; // e.g. X/5 op 3 --> [15, 20)
2485 HiOverflow = LoOverflow = ProdOV;
2486 if (!HiOverflow)
2487 HiOverflow = addWithOverflow(HiBound, Prod, RangeSize, true);
2488 } else { // (X / pos) op neg
2489 // e.g. X/5 op -3 --> [-15-4, -15+1) --> [-19, -14)
2490 HiBound = Prod + 1;
2491 LoOverflow = HiOverflow = ProdOV ? -1 : 0;
2492 if (!LoOverflow) {
2493 APInt DivNeg = -RangeSize;
2494 LoOverflow = addWithOverflow(LoBound, HiBound, DivNeg, true) ? -1 : 0;
2495 }
2496 }
2497 } else if (C2->isNegative()) { // Divisor is < 0.
2498 if (Div->isExact())
2499 RangeSize.negate();
2500 if (C.isNullValue()) { // (X / neg) op 0
2501 // e.g. X/-5 op 0 --> [-4, 5)
2502 LoBound = RangeSize + 1;
2503 HiBound = -RangeSize;
2504 if (HiBound == *C2) { // -INTMIN = INTMIN
2505 HiOverflow = 1; // [INTMIN+1, overflow)
2506 HiBound = APInt(); // e.g. X/INTMIN = 0 --> X > INTMIN
2507 }
2508 } else if (C.isStrictlyPositive()) { // (X / neg) op pos
2509 // e.g. X/-5 op 3 --> [-19, -14)
2510 HiBound = Prod + 1;
2511 HiOverflow = LoOverflow = ProdOV ? -1 : 0;
2512 if (!LoOverflow)
2513 LoOverflow = addWithOverflow(LoBound, HiBound, RangeSize, true) ? -1:0;
2514 } else { // (X / neg) op neg
2515 LoBound = Prod; // e.g. X/-5 op -3 --> [15, 20)
2516 LoOverflow = HiOverflow = ProdOV;
2517 if (!HiOverflow)
2518 HiOverflow = subWithOverflow(HiBound, Prod, RangeSize, true);
2519 }
2520
2521 // Dividing by a negative swaps the condition. LT <-> GT
2522 Pred = ICmpInst::getSwappedPredicate(Pred);
2523 }
2524
2525 Value *X = Div->getOperand(0);
2526 switch (Pred) {
2527 default: llvm_unreachable("Unhandled icmp opcode!")__builtin_unreachable();
2528 case ICmpInst::ICMP_EQ:
2529 if (LoOverflow && HiOverflow)
2530 return replaceInstUsesWith(Cmp, Builder.getFalse());
2531 if (HiOverflow)
2532 return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SGE :
2533 ICmpInst::ICMP_UGE, X,
2534 ConstantInt::get(Div->getType(), LoBound));
2535 if (LoOverflow)
2536 return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SLT :
2537 ICmpInst::ICMP_ULT, X,
2538 ConstantInt::get(Div->getType(), HiBound));
2539 return replaceInstUsesWith(
2540 Cmp, insertRangeTest(X, LoBound, HiBound, DivIsSigned, true));
2541 case ICmpInst::ICMP_NE:
2542 if (LoOverflow && HiOverflow)
2543 return replaceInstUsesWith(Cmp, Builder.getTrue());
2544 if (HiOverflow)
2545 return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SLT :
2546 ICmpInst::ICMP_ULT, X,
2547 ConstantInt::get(Div->getType(), LoBound));
2548 if (LoOverflow)
2549 return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SGE :
2550 ICmpInst::ICMP_UGE, X,
2551 ConstantInt::get(Div->getType(), HiBound));
2552 return replaceInstUsesWith(Cmp,
2553 insertRangeTest(X, LoBound, HiBound,
2554 DivIsSigned, false));
2555 case ICmpInst::ICMP_ULT:
2556 case ICmpInst::ICMP_SLT:
2557 if (LoOverflow == +1) // Low bound is greater than input range.
2558 return replaceInstUsesWith(Cmp, Builder.getTrue());
2559 if (LoOverflow == -1) // Low bound is less than input range.
2560 return replaceInstUsesWith(Cmp, Builder.getFalse());
2561 return new ICmpInst(Pred, X, ConstantInt::get(Div->getType(), LoBound));
2562 case ICmpInst::ICMP_UGT:
2563 case ICmpInst::ICMP_SGT:
2564 if (HiOverflow == +1) // High bound greater than input range.
2565 return replaceInstUsesWith(Cmp, Builder.getFalse());
2566 if (HiOverflow == -1) // High bound less than input range.
2567 return replaceInstUsesWith(Cmp, Builder.getTrue());
2568 if (Pred == ICmpInst::ICMP_UGT)
2569 return new ICmpInst(ICmpInst::ICMP_UGE, X,
2570 ConstantInt::get(Div->getType(), HiBound));
2571 return new ICmpInst(ICmpInst::ICMP_SGE, X,
2572 ConstantInt::get(Div->getType(), HiBound));
2573 }
2574
2575 return nullptr;
2576}
2577
2578/// Fold icmp (sub X, Y), C.
2579Instruction *InstCombinerImpl::foldICmpSubConstant(ICmpInst &Cmp,
2580 BinaryOperator *Sub,
2581 const APInt &C) {
2582 Value *X = Sub->getOperand(0), *Y = Sub->getOperand(1);
2583 ICmpInst::Predicate Pred = Cmp.getPredicate();
2584 const APInt *C2;
2585 APInt SubResult;
2586
2587 // icmp eq/ne (sub C, Y), C -> icmp eq/ne Y, 0
2588 if (match(X, m_APInt(C2)) && *C2 == C && Cmp.isEquality())
2589 return new ICmpInst(Cmp.getPredicate(), Y,
2590 ConstantInt::get(Y->getType(), 0));
2591
2592 // (icmp P (sub nuw|nsw C2, Y), C) -> (icmp swap(P) Y, C2-C)
2593 if (match(X, m_APInt(C2)) &&
2594 ((Cmp.isUnsigned() && Sub->hasNoUnsignedWrap()) ||
2595 (Cmp.isSigned() && Sub->hasNoSignedWrap())) &&
2596 !subWithOverflow(SubResult, *C2, C, Cmp.isSigned()))
2597 return new ICmpInst(Cmp.getSwappedPredicate(), Y,
2598 ConstantInt::get(Y->getType(), SubResult));
2599
2600 // The following transforms are only worth it if the only user of the subtract
2601 // is the icmp.
2602 if (!Sub->hasOneUse())
2603 return nullptr;
2604
2605 if (Sub->hasNoSignedWrap()) {
2606 // (icmp sgt (sub nsw X, Y), -1) -> (icmp sge X, Y)
2607 if (Pred == ICmpInst::ICMP_SGT && C.isAllOnesValue())
2608 return new ICmpInst(ICmpInst::ICMP_SGE, X, Y);
2609
2610 // (icmp sgt (sub nsw X, Y), 0) -> (icmp sgt X, Y)
2611 if (Pred == ICmpInst::ICMP_SGT && C.isNullValue())
2612 return new ICmpInst(ICmpInst::ICMP_SGT, X, Y);
2613
2614 // (icmp slt (sub nsw X, Y), 0) -> (icmp slt X, Y)
2615 if (Pred == ICmpInst::ICMP_SLT && C.isNullValue())
2616 return new ICmpInst(ICmpInst::ICMP_SLT, X, Y);
2617
2618 // (icmp slt (sub nsw X, Y), 1) -> (icmp sle X, Y)
2619 if (Pred == ICmpInst::ICMP_SLT && C.isOneValue())
2620 return new ICmpInst(ICmpInst::ICMP_SLE, X, Y);
2621 }
2622
2623 if (!match(X, m_APInt(C2)))
2624 return nullptr;
2625
2626 // C2 - Y <u C -> (Y | (C - 1)) == C2
2627 // iff (C2 & (C - 1)) == C - 1 and C is a power of 2
2628 if (Pred == ICmpInst::ICMP_ULT && C.isPowerOf2() &&
2629 (*C2 & (C - 1)) == (C - 1))
2630 return new ICmpInst(ICmpInst::ICMP_EQ, Builder.CreateOr(Y, C - 1), X);
2631
2632 // C2 - Y >u C -> (Y | C) != C2
2633 // iff C2 & C == C and C + 1 is a power of 2
2634 if (Pred == ICmpInst::ICMP_UGT && (C + 1).isPowerOf2() && (*C2 & C) == C)
2635 return new ICmpInst(ICmpInst::ICMP_NE, Builder.CreateOr(Y, C), X);
2636
2637 return nullptr;
2638}
2639
2640/// Fold icmp (add X, Y), C.
2641Instruction *InstCombinerImpl::foldICmpAddConstant(ICmpInst &Cmp,
2642 BinaryOperator *Add,
2643 const APInt &C) {
2644 Value *Y = Add->getOperand(1);
2645 const APInt *C2;
2646 if (Cmp.isEquality() || !match(Y, m_APInt(C2)))
2647 return nullptr;
2648
2649 // Fold icmp pred (add X, C2), C.
2650 Value *X = Add->getOperand(0);
2651 Type *Ty = Add->getType();
2652 const CmpInst::Predicate Pred = Cmp.getPredicate();
2653
2654 // If the add does not wrap, we can always adjust the compare by subtracting
2655 // the constants. Equality comparisons are handled elsewhere. SGE/SLE/UGE/ULE
2656 // are canonicalized to SGT/SLT/UGT/ULT.
2657 if ((Add->hasNoSignedWrap() &&
2658 (Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SLT)) ||
2659 (Add->hasNoUnsignedWrap() &&
2660 (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_ULT))) {
2661 bool Overflow;
2662 APInt NewC =
2663 Cmp.isSigned() ? C.ssub_ov(*C2, Overflow) : C.usub_ov(*C2, Overflow);
2664 // If there is overflow, the result must be true or false.
2665 // TODO: Can we assert there is no overflow because InstSimplify always
2666 // handles those cases?
2667 if (!Overflow)
2668 // icmp Pred (add nsw X, C2), C --> icmp Pred X, (C - C2)
2669 return new ICmpInst(Pred, X, ConstantInt::get(Ty, NewC));
2670 }
2671
2672 auto CR = ConstantRange::makeExactICmpRegion(Pred, C).subtract(*C2);
2673 const APInt &Upper = CR.getUpper();
2674 const APInt &Lower = CR.getLower();
2675 if (Cmp.isSigned()) {
2676 if (Lower.isSignMask())
2677 return new ICmpInst(ICmpInst::ICMP_SLT, X, ConstantInt::get(Ty, Upper));
2678 if (Upper.isSignMask())
2679 return new ICmpInst(ICmpInst::ICMP_SGE, X, ConstantInt::get(Ty, Lower));
2680 } else {
2681 if (Lower.isMinValue())
2682 return new ICmpInst(ICmpInst::ICMP_ULT, X, ConstantInt::get(Ty, Upper));
2683 if (Upper.isMinValue())
2684 return new ICmpInst(ICmpInst::ICMP_UGE, X, ConstantInt::get(Ty, Lower));
2685 }
2686
2687 // This set of folds is intentionally placed after folds that use no-wrapping
2688 // flags because those folds are likely better for later analysis/codegen.
2689 const APInt SMax = APInt::getSignedMaxValue(Ty->getScalarSizeInBits());
2690 const APInt SMin = APInt::getSignedMinValue(Ty->getScalarSizeInBits());
2691
2692 // Fold compare with offset to opposite sign compare if it eliminates offset:
2693 // (X + C2) >u C --> X <s -C2 (if C == C2 + SMAX)
2694 if (Pred == CmpInst::ICMP_UGT && C == *C2 + SMax)
2695 return new ICmpInst(ICmpInst::ICMP_SLT, X, ConstantInt::get(Ty, -(*C2)));
2696
2697 // (X + C2) <u C --> X >s ~C2 (if C == C2 + SMIN)
2698 if (Pred == CmpInst::ICMP_ULT && C == *C2 + SMin)
2699 return new ICmpInst(ICmpInst::ICMP_SGT, X, ConstantInt::get(Ty, ~(*C2)));
2700
2701 // (X + C2) >s C --> X <u (SMAX - C) (if C == C2 - 1)
2702 if (Pred == CmpInst::ICMP_SGT && C == *C2 - 1)
2703 return new ICmpInst(ICmpInst::ICMP_ULT, X, ConstantInt::get(Ty, SMax - C));
2704
2705 // (X + C2) <s C --> X >u (C ^ SMAX) (if C == C2)
2706 if (Pred == CmpInst::ICMP_SLT && C == *C2)
2707 return new ICmpInst(ICmpInst::ICMP_UGT, X, ConstantInt::get(Ty, C ^ SMax));
2708
2709 if (!Add->hasOneUse())
2710 return nullptr;
2711
2712 // X+C <u C2 -> (X & -C2) == C
2713 // iff C & (C2-1) == 0
2714 // C2 is a power of 2
2715 if (Pred == ICmpInst::ICMP_ULT && C.isPowerOf2() && (*C2 & (C - 1)) == 0)
2716 return new ICmpInst(ICmpInst::ICMP_EQ, Builder.CreateAnd(X, -C),
2717 ConstantExpr::getNeg(cast<Constant>(Y)));
2718
2719 // X+C >u C2 -> (X & ~C2) != C
2720 // iff C & C2 == 0
2721 // C2+1 is a power of 2
2722 if (Pred == ICmpInst::ICMP_UGT && (C + 1).isPowerOf2() && (*C2 & C) == 0)
2723 return new ICmpInst(ICmpInst::ICMP_NE, Builder.CreateAnd(X, ~C),
2724 ConstantExpr::getNeg(cast<Constant>(Y)));
2725
2726 return nullptr;
2727}
2728
2729bool InstCombinerImpl::matchThreeWayIntCompare(SelectInst *SI, Value *&LHS,
2730 Value *&RHS, ConstantInt *&Less,
2731 ConstantInt *&Equal,
2732 ConstantInt *&Greater) {
2733 // TODO: Generalize this to work with other comparison idioms or ensure
2734 // they get canonicalized into this form.
2735
2736 // select i1 (a == b),
2737 // i32 Equal,
2738 // i32 (select i1 (a < b), i32 Less, i32 Greater)
2739 // where Equal, Less and Greater are placeholders for any three constants.
2740 ICmpInst::Predicate PredA;
2741 if (!match(SI->getCondition(), m_ICmp(PredA, m_Value(LHS), m_Value(RHS))) ||
2742 !ICmpInst::isEquality(PredA))
2743 return false;
2744 Value *EqualVal = SI->getTrueValue();
2745 Value *UnequalVal = SI->getFalseValue();
2746 // We still can get non-canonical predicate here, so canonicalize.
2747 if (PredA == ICmpInst::ICMP_NE)
2748 std::swap(EqualVal, UnequalVal);
2749 if (!match(EqualVal, m_ConstantInt(Equal)))
2750 return false;
2751 ICmpInst::Predicate PredB;
2752 Value *LHS2, *RHS2;
2753 if (!match(UnequalVal, m_Select(m_ICmp(PredB, m_Value(LHS2), m_Value(RHS2)),
2754 m_ConstantInt(Less), m_ConstantInt(Greater))))
2755 return false;
2756 // We can get predicate mismatch here, so canonicalize if possible:
2757 // First, ensure that 'LHS' match.
2758 if (LHS2 != LHS) {
2759 // x sgt y <--> y slt x
2760 std::swap(LHS2, RHS2);
2761 PredB = ICmpInst::getSwappedPredicate(PredB);
2762 }
2763 if (LHS2 != LHS)
2764 return false;
2765 // We also need to canonicalize 'RHS'.
2766 if (PredB == ICmpInst::ICMP_SGT && isa<Constant>(RHS2)) {
2767 // x sgt C-1 <--> x sge C <--> not(x slt C)
2768 auto FlippedStrictness =
2769 InstCombiner::getFlippedStrictnessPredicateAndConstant(
2770 PredB, cast<Constant>(RHS2));
2771 if (!FlippedStrictness)
2772 return false;
2773 assert(FlippedStrictness->first == ICmpInst::ICMP_SGE && "Sanity check")((void)0);
2774 RHS2 = FlippedStrictness->second;
2775 // And kind-of perform the result swap.
2776 std::swap(Less, Greater);
2777 PredB = ICmpInst::ICMP_SLT;
2778 }
2779 return PredB == ICmpInst::ICMP_SLT && RHS == RHS2;
2780}
2781
2782Instruction *InstCombinerImpl::foldICmpSelectConstant(ICmpInst &Cmp,
2783 SelectInst *Select,
2784 ConstantInt *C) {
2785
2786 assert(C && "Cmp RHS should be a constant int!")((void)0);
2787 // If we're testing a constant value against the result of a three way
2788 // comparison, the result can be expressed directly in terms of the
2789 // original values being compared. Note: We could possibly be more
2790 // aggressive here and remove the hasOneUse test. The original select is
2791 // really likely to simplify or sink when we remove a test of the result.
2792 Value *OrigLHS, *OrigRHS;
2793 ConstantInt *C1LessThan, *C2Equal, *C3GreaterThan;
2794 if (Cmp.hasOneUse() &&
2795 matchThreeWayIntCompare(Select, OrigLHS, OrigRHS, C1LessThan, C2Equal,
2796 C3GreaterThan)) {
2797 assert(C1LessThan && C2Equal && C3GreaterThan)((void)0);
2798
2799 bool TrueWhenLessThan =
2800 ConstantExpr::getCompare(Cmp.getPredicate(), C1LessThan, C)
2801 ->isAllOnesValue();
2802 bool TrueWhenEqual =
2803 ConstantExpr::getCompare(Cmp.getPredicate(), C2Equal, C)
2804 ->isAllOnesValue();
2805 bool TrueWhenGreaterThan =
2806 ConstantExpr::getCompare(Cmp.getPredicate(), C3GreaterThan, C)
2807 ->isAllOnesValue();
2808
2809 // This generates the new instruction that will replace the original Cmp
2810 // Instruction. Instead of enumerating the various combinations when
2811 // TrueWhenLessThan, TrueWhenEqual and TrueWhenGreaterThan are true versus
2812 // false, we rely on chaining of ORs and future passes of InstCombine to
2813 // simplify the OR further (i.e. a s< b || a == b becomes a s<= b).
2814
2815 // When none of the three constants satisfy the predicate for the RHS (C),
2816 // the entire original Cmp can be simplified to a false.
2817 Value *Cond = Builder.getFalse();
2818 if (TrueWhenLessThan)
2819 Cond = Builder.CreateOr(Cond, Builder.CreateICmp(ICmpInst::ICMP_SLT,
2820 OrigLHS, OrigRHS));
2821 if (TrueWhenEqual)
2822 Cond = Builder.CreateOr(Cond, Builder.CreateICmp(ICmpInst::ICMP_EQ,
2823 OrigLHS, OrigRHS));
2824 if (TrueWhenGreaterThan)
2825 Cond = Builder.CreateOr(Cond, Builder.CreateICmp(ICmpInst::ICMP_SGT,
2826 OrigLHS, OrigRHS));
2827
2828 return replaceInstUsesWith(Cmp, Cond);
2829 }
2830 return nullptr;
2831}
2832
2833static Instruction *foldICmpBitCast(ICmpInst &Cmp,
2834 InstCombiner::BuilderTy &Builder) {
2835 auto *Bitcast = dyn_cast<BitCastInst>(Cmp.getOperand(0));
2836 if (!Bitcast)
2837 return nullptr;
2838
2839 ICmpInst::Predicate Pred = Cmp.getPredicate();
2840 Value *Op1 = Cmp.getOperand(1);
2841 Value *BCSrcOp = Bitcast->getOperand(0);
2842
2843 // Make sure the bitcast doesn't change the number of vector elements.
2844 if (Bitcast->getSrcTy()->getScalarSizeInBits() ==
2845 Bitcast->getDestTy()->getScalarSizeInBits()) {
2846 // Zero-equality and sign-bit checks are preserved through sitofp + bitcast.
2847 Value *X;
2848 if (match(BCSrcOp, m_SIToFP(m_Value(X)))) {
2849 // icmp eq (bitcast (sitofp X)), 0 --> icmp eq X, 0
2850 // icmp ne (bitcast (sitofp X)), 0 --> icmp ne X, 0
2851 // icmp slt (bitcast (sitofp X)), 0 --> icmp slt X, 0
2852 // icmp sgt (bitcast (sitofp X)), 0 --> icmp sgt X, 0
2853 if ((Pred == ICmpInst::ICMP_EQ || Pred == ICmpInst::ICMP_SLT ||
2854 Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_SGT) &&
2855 match(Op1, m_Zero()))
2856 return new ICmpInst(Pred, X, ConstantInt::getNullValue(X->getType()));
2857
2858 // icmp slt (bitcast (sitofp X)), 1 --> icmp slt X, 1
2859 if (Pred == ICmpInst::ICMP_SLT && match(Op1, m_One()))
2860 return new ICmpInst(Pred, X, ConstantInt::get(X->getType(), 1));
2861
2862 // icmp sgt (bitcast (sitofp X)), -1 --> icmp sgt X, -1
2863 if (Pred == ICmpInst::ICMP_SGT && match(Op1, m_AllOnes()))
2864 return new ICmpInst(Pred, X,
2865 ConstantInt::getAllOnesValue(X->getType()));
2866 }
2867
2868 // Zero-equality checks are preserved through unsigned floating-point casts:
2869 // icmp eq (bitcast (uitofp X)), 0 --> icmp eq X, 0
2870 // icmp ne (bitcast (uitofp X)), 0 --> icmp ne X, 0
2871 if (match(BCSrcOp, m_UIToFP(m_Value(X))))
2872 if (Cmp.isEquality() && match(Op1, m_Zero()))
2873 return new ICmpInst(Pred, X, ConstantInt::getNullValue(X->getType()));
2874
2875 // If this is a sign-bit test of a bitcast of a casted FP value, eliminate
2876 // the FP extend/truncate because that cast does not change the sign-bit.
2877 // This is true for all standard IEEE-754 types and the X86 80-bit type.
2878 // The sign-bit is always the most significant bit in those types.
2879 const APInt *C;
2880 bool TrueIfSigned;
2881 if (match(Op1, m_APInt(C)) && Bitcast->hasOneUse() &&
2882 InstCombiner::isSignBitCheck(Pred, *C, TrueIfSigned)) {
2883 if (match(BCSrcOp, m_FPExt(m_Value(X))) ||
2884 match(BCSrcOp, m_FPTrunc(m_Value(X)))) {
2885 // (bitcast (fpext/fptrunc X)) to iX) < 0 --> (bitcast X to iY) < 0
2886 // (bitcast (fpext/fptrunc X)) to iX) > -1 --> (bitcast X to iY) > -1
2887 Type *XType = X->getType();
2888
2889 // We can't currently handle Power style floating point operations here.
2890 if (!(XType->isPPC_FP128Ty() || BCSrcOp->getType()->isPPC_FP128Ty())) {
2891
2892 Type *NewType = Builder.getIntNTy(XType->getScalarSizeInBits());
2893 if (auto *XVTy = dyn_cast<VectorType>(XType))
2894 NewType = VectorType::get(NewType, XVTy->getElementCount());
2895 Value *NewBitcast = Builder.CreateBitCast(X, NewType);
2896 if (TrueIfSigned)
2897 return new ICmpInst(ICmpInst::ICMP_SLT, NewBitcast,
2898 ConstantInt::getNullValue(NewType));
2899 else
2900 return new ICmpInst(ICmpInst::ICMP_SGT, NewBitcast,
2901 ConstantInt::getAllOnesValue(NewType));
2902 }
2903 }
2904 }
2905 }
2906
2907 // Test to see if the operands of the icmp are casted versions of other
2908 // values. If the ptr->ptr cast can be stripped off both arguments, do so.
2909 if (Bitcast->getType()->isPointerTy() &&
2910 (isa<Constant>(Op1) || isa<BitCastInst>(Op1))) {
2911 // If operand #1 is a bitcast instruction, it must also be a ptr->ptr cast
2912 // so eliminate it as well.
2913 if (auto *BC2 = dyn_cast<BitCastInst>(Op1))
2914 Op1 = BC2->getOperand(0);
2915
2916 Op1 = Builder.CreateBitCast(Op1, BCSrcOp->getType());
2917 return new ICmpInst(Pred, BCSrcOp, Op1);
2918 }
2919
2920 // Folding: icmp <pred> iN X, C
2921 // where X = bitcast <M x iK> (shufflevector <M x iK> %vec, undef, SC)) to iN
2922 // and C is a splat of a K-bit pattern
2923 // and SC is a constant vector = <C', C', C', ..., C'>
2924 // Into:
2925 // %E = extractelement <M x iK> %vec, i32 C'
2926 // icmp <pred> iK %E, trunc(C)
2927 const APInt *C;
2928 if (!match(Cmp.getOperand(1), m_APInt(C)) ||
2929 !Bitcast->getType()->isIntegerTy() ||
2930 !Bitcast->getSrcTy()->isIntOrIntVectorTy())
2931 return nullptr;
2932
2933 Value *Vec;
2934 ArrayRef<int> Mask;
2935 if (match(BCSrcOp, m_Shuffle(m_Value(Vec), m_Undef(), m_Mask(Mask)))) {
2936 // Check whether every element of Mask is the same constant
2937 if (is_splat(Mask)) {
2938 auto *VecTy = cast<VectorType>(BCSrcOp->getType());
2939 auto *EltTy = cast<IntegerType>(VecTy->getElementType());
2940 if (C->isSplat(EltTy->getBitWidth())) {
2941 // Fold the icmp based on the value of C
2942 // If C is M copies of an iK sized bit pattern,
2943 // then:
2944 // => %E = extractelement <N x iK> %vec, i32 Elem
2945 // icmp <pred> iK %SplatVal, <pattern>
2946 Value *Elem = Builder.getInt32(Mask[0]);
2947 Value *Extract = Builder.CreateExtractElement(Vec, Elem);
2948 Value *NewC = ConstantInt::get(EltTy, C->trunc(EltTy->getBitWidth()));
2949 return new ICmpInst(Pred, Extract, NewC);
2950 }
2951 }
2952 }
2953 return nullptr;
2954}
2955
2956/// Try to fold integer comparisons with a constant operand: icmp Pred X, C
2957/// where X is some kind of instruction.
2958Instruction *InstCombinerImpl::foldICmpInstWithConstant(ICmpInst &Cmp) {
2959 const APInt *C;
2960 if (!match(Cmp.getOperand(1), m_APInt(C)))
2961 return nullptr;
2962
2963 if (auto *BO = dyn_cast<BinaryOperator>(Cmp.getOperand(0))) {
2964 switch (BO->getOpcode()) {
2965 case Instruction::Xor:
2966 if (Instruction *I = foldICmpXorConstant(Cmp, BO, *C))
2967 return I;
2968 break;
2969 case Instruction::And:
2970 if (Instruction *I = foldICmpAndConstant(Cmp, BO, *C))
2971 return I;
2972 break;
2973 case Instruction::Or:
2974 if (Instruction *I = foldICmpOrConstant(Cmp, BO, *C))
2975 return I;
2976 break;
2977 case Instruction::Mul:
2978 if (Instruction *I = foldICmpMulConstant(Cmp, BO, *C))
2979 return I;
2980 break;
2981 case Instruction::Shl:
2982 if (Instruction *I = foldICmpShlConstant(Cmp, BO, *C))
2983 return I;
2984 break;
2985 case Instruction::LShr:
2986 case Instruction::AShr:
2987 if (Instruction *I = foldICmpShrConstant(Cmp, BO, *C))
2988 return I;
2989 break;
2990 case Instruction::SRem:
2991 if (Instruction *I = foldICmpSRemConstant(Cmp, BO, *C))
2992 return I;
2993 break;
2994 case Instruction::UDiv:
2995 if (Instruction *I = foldICmpUDivConstant(Cmp, BO, *C))
2996 return I;
2997 LLVM_FALLTHROUGH[[gnu::fallthrough]];
2998 case Instruction::SDiv:
2999 if (Instruction *I = foldICmpDivConstant(Cmp, BO, *C))
3000 return I;
3001 break;
3002 case Instruction::Sub:
3003 if (Instruction *I = foldICmpSubConstant(Cmp, BO, *C))
3004 return I;
3005 break;
3006 case Instruction::Add:
3007 if (Instruction *I = foldICmpAddConstant(Cmp, BO, *C))
3008 return I;
3009 break;
3010 default:
3011 break;
3012 }
3013 // TODO: These folds could be refactored to be part of the above calls.
3014 if (Instruction *I = foldICmpBinOpEqualityWithConstant(Cmp, BO, *C))
3015 return I;
3016 }
3017
3018 // Match against CmpInst LHS being instructions other than binary operators.
3019
3020 if (auto *SI = dyn_cast<SelectInst>(Cmp.getOperand(0))) {
3021 // For now, we only support constant integers while folding the
3022 // ICMP(SELECT)) pattern. We can extend this to support vector of integers
3023 // similar to the cases handled by binary ops above.
3024 if (ConstantInt *ConstRHS = dyn_cast<ConstantInt>(Cmp.getOperand(1)))
3025 if (Instruction *I = foldICmpSelectConstant(Cmp, SI, ConstRHS))
3026 return I;
3027 }
3028
3029 if (auto *TI = dyn_cast<TruncInst>(Cmp.getOperand(0))) {
3030 if (Instruction *I = foldICmpTruncConstant(Cmp, TI, *C))
3031 return I;
3032 }
3033
3034 if (auto *II = dyn_cast<IntrinsicInst>(Cmp.getOperand(0)))
3035 if (Instruction *I = foldICmpIntrinsicWithConstant(Cmp, II, *C))
3036 return I;
3037
3038 return nullptr;
3039}
3040
3041/// Fold an icmp equality instruction with binary operator LHS and constant RHS:
3042/// icmp eq/ne BO, C.
3043Instruction *InstCombinerImpl::foldICmpBinOpEqualityWithConstant(
3044 ICmpInst &Cmp, BinaryOperator *BO, const APInt &C) {
3045 // TODO: Some of these folds could work with arbitrary constants, but this
3046 // function is limited to scalar and vector splat constants.
3047 if (!Cmp.isEquality())
3048 return nullptr;
3049
3050 ICmpInst::Predicate Pred = Cmp.getPredicate();
3051 bool isICMP_NE = Pred == ICmpInst::ICMP_NE;
3052 Constant *RHS = cast<Constant>(Cmp.getOperand(1));
3053 Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1);
3054
3055 switch (BO->getOpcode()) {
3056 case Instruction::SRem:
3057 // If we have a signed (X % (2^c)) == 0, turn it into an unsigned one.
3058 if (C.isNullValue() && BO->hasOneUse()) {
3059 const APInt *BOC;
3060 if (match(BOp1, m_APInt(BOC)) && BOC->sgt(1) && BOC->isPowerOf2()) {
3061 Value *NewRem = Builder.CreateURem(BOp0, BOp1, BO->getName());
3062 return new ICmpInst(Pred, NewRem,
3063 Constant::getNullValue(BO->getType()));
3064 }
3065 }
3066 break;
3067 case Instruction::Add: {
3068 // Replace ((add A, B) != C) with (A != C-B) if B & C are constants.
3069 if (Constant *BOC = dyn_cast<Constant>(BOp1)) {
3070 if (BO->hasOneUse())
3071 return new ICmpInst(Pred, BOp0, ConstantExpr::getSub(RHS, BOC));
3072 } else if (C.isNullValue()) {
3073 // Replace ((add A, B) != 0) with (A != -B) if A or B is
3074 // efficiently invertible, or if the add has just this one use.
3075 if (Value *NegVal = dyn_castNegVal(BOp1))
3076 return new ICmpInst(Pred, BOp0, NegVal);
3077 if (Value *NegVal = dyn_castNegVal(BOp0))
3078 return new ICmpInst(Pred, NegVal, BOp1);
3079 if (BO->hasOneUse()) {
3080 Value *Neg = Builder.CreateNeg(BOp1);
3081 Neg->takeName(BO);
3082 return new ICmpInst(Pred, BOp0, Neg);
3083 }
3084 }
3085 break;
3086 }
3087 case Instruction::Xor:
3088 if (BO->hasOneUse()) {
3089 if (Constant *BOC = dyn_cast<Constant>(BOp1)) {
3090 // For the xor case, we can xor two constants together, eliminating
3091 // the explicit xor.
3092 return new ICmpInst(Pred, BOp0, ConstantExpr::getXor(RHS, BOC));
3093 } else if (C.isNullValue()) {
3094 // Replace ((xor A, B) != 0) with (A != B)
3095 return new ICmpInst(Pred, BOp0, BOp1);
3096 }
3097 }
3098 break;
3099 case Instruction::Sub:
3100 if (BO->hasOneUse()) {
3101 // Only check for constant LHS here, as constant RHS will be canonicalized
3102 // to add and use the fold above.
3103 if (Constant *BOC = dyn_cast<Constant>(BOp0)) {
3104 // Replace ((sub BOC, B) != C) with (B != BOC-C).
3105 return new ICmpInst(Pred, BOp1, ConstantExpr::getSub(BOC, RHS));
3106 } else if (C.isNullValue()) {
3107 // Replace ((sub A, B) != 0) with (A != B).
3108 return new ICmpInst(Pred, BOp0, BOp1);
3109 }
3110 }
3111 break;
3112 case Instruction::Or: {
3113 const APInt *BOC;
3114 if (match(BOp1, m_APInt(BOC)) && BO->hasOneUse() && RHS->isAllOnesValue()) {
3115 // Comparing if all bits outside of a constant mask are set?
3116 // Replace (X | C) == -1 with (X & ~C) == ~C.
3117 // This removes the -1 constant.
3118 Constant *NotBOC = ConstantExpr::getNot(cast<Constant>(BOp1));
3119 Value *And = Builder.CreateAnd(BOp0, NotBOC);
3120 return new ICmpInst(Pred, And, NotBOC);
3121 }
3122 break;
3123 }
3124 case Instruction::And: {
3125 const APInt *BOC;
3126 if (match(BOp1, m_APInt(BOC))) {
3127 // If we have ((X & C) == C), turn it into ((X & C) != 0).
3128 if (C == *BOC && C.isPowerOf2())
3129 return new ICmpInst(isICMP_NE ? ICmpInst::ICMP_EQ : ICmpInst::ICMP_NE,
3130 BO, Constant::getNullValue(RHS->getType()));
3131 }
3132 break;
3133 }
3134 case Instruction::UDiv:
3135 if (C.isNullValue()) {
3136 // (icmp eq/ne (udiv A, B), 0) -> (icmp ugt/ule i32 B, A)
3137 auto NewPred = isICMP_NE ? ICmpInst::ICMP_ULE : ICmpInst::ICMP_UGT;
3138 return new ICmpInst(NewPred, BOp1, BOp0);
3139 }
3140 break;
3141 default:
3142 break;
3143 }
3144 return nullptr;
3145}
3146
3147/// Fold an equality icmp with LLVM intrinsic and constant operand.
3148Instruction *InstCombinerImpl::foldICmpEqIntrinsicWithConstant(
3149 ICmpInst &Cmp, IntrinsicInst *II, const APInt &C) {
3150 Type *Ty = II->getType();
3151 unsigned BitWidth = C.getBitWidth();
3152 switch (II->getIntrinsicID()) {
3153 case Intrinsic::abs:
3154 // abs(A) == 0 -> A == 0
3155 // abs(A) == INT_MIN -> A == INT_MIN
3156 if (C.isNullValue() || C.isMinSignedValue())
3157 return new ICmpInst(Cmp.getPredicate(), II->getArgOperand(0),
3158 ConstantInt::get(Ty, C));
3159 break;
3160
3161 case Intrinsic::bswap:
3162 // bswap(A) == C -> A == bswap(C)
3163 return new ICmpInst(Cmp.getPredicate(), II->getArgOperand(0),
3164 ConstantInt::get(Ty, C.byteSwap()));
3165
3166 case Intrinsic::ctlz:
3167 case Intrinsic::cttz: {
3168 // ctz(A) == bitwidth(A) -> A == 0 and likewise for !=
3169 if (C == BitWidth)
3170 return new ICmpInst(Cmp.getPredicate(), II->getArgOperand(0),
3171 ConstantInt::getNullValue(Ty));
3172
3173 // ctz(A) == C -> A & Mask1 == Mask2, where Mask2 only has bit C set
3174 // and Mask1 has bits 0..C+1 set. Similar for ctl, but for high bits.
3175 // Limit to one use to ensure we don't increase instruction count.
3176 unsigned Num = C.getLimitedValue(BitWidth);
3177 if (Num != BitWidth && II->hasOneUse()) {
3178 bool IsTrailing = II->getIntrinsicID() == Intrinsic::cttz;
3179 APInt Mask1 = IsTrailing ? APInt::getLowBitsSet(BitWidth, Num + 1)
3180 : APInt::getHighBitsSet(BitWidth, Num + 1);
3181 APInt Mask2 = IsTrailing
3182 ? APInt::getOneBitSet(BitWidth, Num)
3183 : APInt::getOneBitSet(BitWidth, BitWidth - Num - 1);
3184 return new ICmpInst(Cmp.getPredicate(),
3185 Builder.CreateAnd(II->getArgOperand(0), Mask1),
3186 ConstantInt::get(Ty, Mask2));
3187 }
3188 break;
3189 }
3190
3191 case Intrinsic::ctpop: {
3192 // popcount(A) == 0 -> A == 0 and likewise for !=
3193 // popcount(A) == bitwidth(A) -> A == -1 and likewise for !=
3194 bool IsZero = C.isNullValue();
3195 if (IsZero || C == BitWidth)
3196 return new ICmpInst(Cmp.getPredicate(), II->getArgOperand(0),
3197 IsZero ? Constant::getNullValue(Ty) : Constant::getAllOnesValue(Ty));
3198
3199 break;
3200 }
3201
3202 case Intrinsic::uadd_sat: {
3203 // uadd.sat(a, b) == 0 -> (a | b) == 0
3204 if (C.isNullValue()) {
3205 Value *Or = Builder.CreateOr(II->getArgOperand(0), II->getArgOperand(1));
3206 return new ICmpInst(Cmp.getPredicate(), Or, Constant::getNullValue(Ty));
3207 }
3208 break;
3209 }
3210
3211 case Intrinsic::usub_sat: {
3212 // usub.sat(a, b) == 0 -> a <= b
3213 if (C.isNullValue()) {
3214 ICmpInst::Predicate NewPred = Cmp.getPredicate() == ICmpInst::ICMP_EQ
3215 ? ICmpInst::ICMP_ULE : ICmpInst::ICMP_UGT;
3216 return new ICmpInst(NewPred, II->getArgOperand(0), II->getArgOperand(1));
3217 }
3218 break;
3219 }
3220 default:
3221 break;
3222 }
3223
3224 return nullptr;
3225}
3226
3227/// Fold an icmp with LLVM intrinsic and constant operand: icmp Pred II, C.
3228Instruction *InstCombinerImpl::foldICmpIntrinsicWithConstant(ICmpInst &Cmp,
3229 IntrinsicInst *II,
3230 const APInt &C) {
3231 if (Cmp.isEquality())
3232 return foldICmpEqIntrinsicWithConstant(Cmp, II, C);
3233
3234 Type *Ty = II->getType();
3235 unsigned BitWidth = C.getBitWidth();
3236 ICmpInst::Predicate Pred = Cmp.getPredicate();
3237 switch (II->getIntrinsicID()) {
3238 case Intrinsic::ctpop: {
3239 // (ctpop X > BitWidth - 1) --> X == -1
3240 Value *X = II->getArgOperand(0);
3241 if (C == BitWidth - 1 && Pred == ICmpInst::ICMP_UGT)
3242 return CmpInst::Create(Instruction::ICmp, ICmpInst::ICMP_EQ, X,
3243 ConstantInt::getAllOnesValue(Ty));
3244 // (ctpop X < BitWidth) --> X != -1
3245 if (C == BitWidth && Pred == ICmpInst::ICMP_ULT)
3246 return CmpInst::Create(Instruction::ICmp, ICmpInst::ICMP_NE, X,
3247 ConstantInt::getAllOnesValue(Ty));
3248 break;
3249 }
3250 case Intrinsic::ctlz: {
3251 // ctlz(0bXXXXXXXX) > 3 -> 0bXXXXXXXX < 0b00010000
3252 if (Pred == ICmpInst::ICMP_UGT && C.ult(BitWidth)) {
3253 unsigned Num = C.getLimitedValue();
3254 APInt Limit = APInt::getOneBitSet(BitWidth, BitWidth - Num - 1);
3255 return CmpInst::Create(Instruction::ICmp, ICmpInst::ICMP_ULT,
3256 II->getArgOperand(0), ConstantInt::get(Ty, Limit));
3257 }
3258
3259 // ctlz(0bXXXXXXXX) < 3 -> 0bXXXXXXXX > 0b00011111
3260 if (Pred == ICmpInst::ICMP_ULT && C.uge(1) && C.ule(BitWidth)) {
3261 unsigned Num = C.getLimitedValue();
3262 APInt Limit = APInt::getLowBitsSet(BitWidth, BitWidth - Num);
3263 return CmpInst::Create(Instruction::ICmp, ICmpInst::ICMP_UGT,
3264 II->getArgOperand(0), ConstantInt::get(Ty, Limit));
3265 }
3266 break;
3267 }
3268 case Intrinsic::cttz: {
3269 // Limit to one use to ensure we don't increase instruction count.
3270 if (!II->hasOneUse())
3271 return nullptr;
3272
3273 // cttz(0bXXXXXXXX) > 3 -> 0bXXXXXXXX & 0b00001111 == 0
3274 if (Pred == ICmpInst::ICMP_UGT && C.ult(BitWidth)) {
3275 APInt Mask = APInt::getLowBitsSet(BitWidth, C.getLimitedValue() + 1);
3276 return CmpInst::Create(Instruction::ICmp, ICmpInst::ICMP_EQ,
3277 Builder.CreateAnd(II->getArgOperand(0), Mask),
3278 ConstantInt::getNullValue(Ty));
3279 }
3280
3281 // cttz(0bXXXXXXXX) < 3 -> 0bXXXXXXXX & 0b00000111 != 0
3282 if (Pred == ICmpInst::ICMP_ULT && C.uge(1) && C.ule(BitWidth)) {
3283 APInt Mask = APInt::getLowBitsSet(BitWidth, C.getLimitedValue());
3284 return CmpInst::Create(Instruction::ICmp, ICmpInst::ICMP_NE,
3285 Builder.CreateAnd(II->getArgOperand(0), Mask),
3286 ConstantInt::getNullValue(Ty));
3287 }
3288 break;
3289 }
3290 default:
3291 break;
3292 }
3293
3294 return nullptr;
3295}
3296
3297/// Handle icmp with constant (but not simple integer constant) RHS.
3298Instruction *InstCombinerImpl::foldICmpInstWithConstantNotInt(ICmpInst &I) {
3299 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
3300 Constant *RHSC = dyn_cast<Constant>(Op1);
3301 Instruction *LHSI = dyn_cast<Instruction>(Op0);
3302 if (!RHSC || !LHSI)
3303 return nullptr;
3304
3305 switch (LHSI->getOpcode()) {
3306 case Instruction::GetElementPtr:
3307 // icmp pred GEP (P, int 0, int 0, int 0), null -> icmp pred P, null
3308 if (RHSC->isNullValue() &&
3309 cast<GetElementPtrInst>(LHSI)->hasAllZeroIndices())
3310 return new ICmpInst(
3311 I.getPredicate(), LHSI->getOperand(0),
3312 Constant::getNullValue(LHSI->getOperand(0)->getType()));
3313 break;
3314 case Instruction::PHI:
3315 // Only fold icmp into the PHI if the phi and icmp are in the same
3316 // block. If in the same block, we're encouraging jump threading. If
3317 // not, we are just pessimizing the code by making an i1 phi.
3318 if (LHSI->getParent() == I.getParent())
3319 if (Instruction *NV = foldOpIntoPhi(I, cast<PHINode>(LHSI)))
3320 return NV;
3321 break;
3322 case Instruction::Select: {
3323 // If either operand of the select is a constant, we can fold the
3324 // comparison into the select arms, which will cause one to be
3325 // constant folded and the select turned into a bitwise or.
3326 Value *Op1 = nullptr, *Op2 = nullptr;
3327 ConstantInt *CI = nullptr;
3328
3329 auto SimplifyOp = [&](Value *V) {
3330 Value *Op = nullptr;
3331 if (Constant *C = dyn_cast<Constant>(V)) {
3332 Op = ConstantExpr::getICmp(I.getPredicate(), C, RHSC);
3333 } else if (RHSC->isNullValue()) {
3334 // If null is being compared, check if it can be further simplified.
3335 Op = SimplifyICmpInst(I.getPredicate(), V, RHSC, SQ);
3336 }
3337 return Op;
3338 };
3339 Op1 = SimplifyOp(LHSI->getOperand(1));
3340 if (Op1)
3341 CI = dyn_cast<ConstantInt>(Op1);
3342
3343 Op2 = SimplifyOp(LHSI->getOperand(2));
3344 if (Op2)
3345 CI = dyn_cast<ConstantInt>(Op2);
3346
3347 // We only want to perform this transformation if it will not lead to
3348 // additional code. This is true if either both sides of the select
3349 // fold to a constant (in which case the icmp is replaced with a select
3350 // which will usually simplify) or this is the only user of the
3351 // select (in which case we are trading a select+icmp for a simpler
3352 // select+icmp) or all uses of the select can be replaced based on
3353 // dominance information ("Global cases").
3354 bool Transform = false;
3355 if (Op1 && Op2)
3356 Transform = true;
3357 else if (Op1 || Op2) {
3358 // Local case
3359 if (LHSI->hasOneUse())
3360 Transform = true;
3361 // Global cases
3362 else if (CI && !CI->isZero())
3363 // When Op1 is constant try replacing select with second operand.
3364 // Otherwise Op2 is constant and try replacing select with first
3365 // operand.
3366 Transform =
3367 replacedSelectWithOperand(cast<SelectInst>(LHSI), &I, Op1 ? 2 : 1);
3368 }
3369 if (Transform) {
3370 if (!Op1)
3371 Op1 = Builder.CreateICmp(I.getPredicate(), LHSI->getOperand(1), RHSC,
3372 I.getName());
3373 if (!Op2)
3374 Op2 = Builder.CreateICmp(I.getPredicate(), LHSI->getOperand(2), RHSC,
3375 I.getName());
3376 return SelectInst::Create(LHSI->getOperand(0), Op1, Op2);
3377 }
3378 break;
3379 }
3380 case Instruction::IntToPtr:
3381 // icmp pred inttoptr(X), null -> icmp pred X, 0
3382 if (RHSC->isNullValue() &&
3383 DL.getIntPtrType(RHSC->getType()) == LHSI->getOperand(0)->getType())
3384 return new ICmpInst(
3385 I.getPredicate(), LHSI->getOperand(0),
3386 Constant::getNullValue(LHSI->getOperand(0)->getType()));
3387 break;
3388
3389 case Instruction::Load:
3390 // Try to optimize things like "A[i] > 4" to index computations.
3391 if (GetElementPtrInst *GEP =
3392 dyn_cast<GetElementPtrInst>(LHSI->getOperand(0))) {
3393 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0)))
3394 if (GV->isConstant() && GV->hasDefinitiveInitializer() &&
3395 !cast<LoadInst>(LHSI)->isVolatile())
3396 if (Instruction *Res = foldCmpLoadFromIndexedGlobal(GEP, GV, I))
3397 return Res;
3398 }
3399 break;
3400 }
3401
3402 return nullptr;
3403}
3404
3405/// Some comparisons can be simplified.
3406/// In this case, we are looking for comparisons that look like
3407/// a check for a lossy truncation.
3408/// Folds:
3409/// icmp SrcPred (x & Mask), x to icmp DstPred x, Mask
3410/// Where Mask is some pattern that produces all-ones in low bits:
3411/// (-1 >> y)
3412/// ((-1 << y) >> y) <- non-canonical, has extra uses
3413/// ~(-1 << y)
3414/// ((1 << y) + (-1)) <- non-canonical, has extra uses
3415/// The Mask can be a constant, too.
3416/// For some predicates, the operands are commutative.
3417/// For others, x can only be on a specific side.
3418static Value *foldICmpWithLowBitMaskedVal(ICmpInst &I,
3419 InstCombiner::BuilderTy &Builder) {
3420 ICmpInst::Predicate SrcPred;
3421 Value *X, *M, *Y;
3422 auto m_VariableMask = m_CombineOr(
3423 m_CombineOr(m_Not(m_Shl(m_AllOnes(), m_Value())),
3424 m_Add(m_Shl(m_One(), m_Value()), m_AllOnes())),
3425 m_CombineOr(m_LShr(m_AllOnes(), m_Value()),
3426 m_LShr(m_Shl(m_AllOnes(), m_Value(Y)), m_Deferred(Y))));
3427 auto m_Mask = m_CombineOr(m_VariableMask, m_LowBitMask());
3428 if (!match(&I, m_c_ICmp(SrcPred,
3429 m_c_And(m_CombineAnd(m_Mask, m_Value(M)), m_Value(X)),
3430 m_Deferred(X))))
3431 return nullptr;
3432
3433 ICmpInst::Predicate DstPred;
3434 switch (SrcPred) {
3435 case ICmpInst::Predicate::ICMP_EQ:
3436 // x & (-1 >> y) == x -> x u<= (-1 >> y)
3437 DstPred = ICmpInst::Predicate::ICMP_ULE;
3438 break;
3439 case ICmpInst::Predicate::ICMP_NE:
3440 // x & (-1 >> y) != x -> x u> (-1 >> y)
3441 DstPred = ICmpInst::Predicate::ICMP_UGT;
3442 break;
3443 case ICmpInst::Predicate::ICMP_ULT:
3444 // x & (-1 >> y) u< x -> x u> (-1 >> y)
3445 // x u> x & (-1 >> y) -> x u> (-1 >> y)
3446 DstPred = ICmpInst::Predicate::ICMP_UGT;
3447 break;
3448 case ICmpInst::Predicate::ICMP_UGE:
3449 // x & (-1 >> y) u>= x -> x u<= (-1 >> y)
3450 // x u<= x & (-1 >> y) -> x u<= (-1 >> y)
3451 DstPred = ICmpInst::Predicate::ICMP_ULE;
3452 break;
3453 case ICmpInst::Predicate::ICMP_SLT:
3454 // x & (-1 >> y) s< x -> x s> (-1 >> y)
3455 // x s> x & (-1 >> y) -> x s> (-1 >> y)
3456 if (!match(M, m_Constant())) // Can not do this fold with non-constant.
3457 return nullptr;
3458 if (!match(M, m_NonNegative())) // Must not have any -1 vector elements.
3459 return nullptr;
3460 DstPred = ICmpInst::Predicate::ICMP_SGT;
3461 break;
3462 case ICmpInst::Predicate::ICMP_SGE:
3463 // x & (-1 >> y) s>= x -> x s<= (-1 >> y)
3464 // x s<= x & (-1 >> y) -> x s<= (-1 >> y)
3465 if (!match(M, m_Constant())) // Can not do this fold with non-constant.
3466 return nullptr;
3467 if (!match(M, m_NonNegative())) // Must not have any -1 vector elements.
3468 return nullptr;
3469 DstPred = ICmpInst::Predicate::ICMP_SLE;
3470 break;
3471 case ICmpInst::Predicate::ICMP_SGT:
3472 case ICmpInst::Predicate::ICMP_SLE:
3473 return nullptr;
3474 case ICmpInst::Predicate::ICMP_UGT:
3475 case ICmpInst::Predicate::ICMP_ULE:
3476 llvm_unreachable("Instsimplify took care of commut. variant")__builtin_unreachable();
3477 break;
3478 default:
3479 llvm_unreachable("All possible folds are handled.")__builtin_unreachable();
3480 }
3481
3482 // The mask value may be a vector constant that has undefined elements. But it
3483 // may not be safe to propagate those undefs into the new compare, so replace
3484 // those elements by copying an existing, defined, and safe scalar constant.
3485 Type *OpTy = M->getType();
3486 auto *VecC = dyn_cast<Constant>(M);
3487 auto *OpVTy = dyn_cast<FixedVectorType>(OpTy);
3488 if (OpVTy && VecC && VecC->containsUndefOrPoisonElement()) {
3489 Constant *SafeReplacementConstant = nullptr;
3490 for (unsigned i = 0, e = OpVTy->getNumElements(); i != e; ++i) {
3491 if (!isa<UndefValue>(VecC->getAggregateElement(i))) {
3492 SafeReplacementConstant = VecC->getAggregateElement(i);
3493 break;
3494 }
3495 }
3496 assert(SafeReplacementConstant && "Failed to find undef replacement")((void)0);
3497 M = Constant::replaceUndefsWith(VecC, SafeReplacementConstant);
3498 }
3499
3500 return Builder.CreateICmp(DstPred, X, M);
3501}
3502
3503/// Some comparisons can be simplified.
3504/// In this case, we are looking for comparisons that look like
3505/// a check for a lossy signed truncation.
3506/// Folds: (MaskedBits is a constant.)
3507/// ((%x << MaskedBits) a>> MaskedBits) SrcPred %x
3508/// Into:
3509/// (add %x, (1 << (KeptBits-1))) DstPred (1 << KeptBits)
3510/// Where KeptBits = bitwidth(%x) - MaskedBits
3511static Value *
3512foldICmpWithTruncSignExtendedVal(ICmpInst &I,
3513 InstCombiner::BuilderTy &Builder) {
3514 ICmpInst::Predicate SrcPred;
3515 Value *X;
3516 const APInt *C0, *C1; // FIXME: non-splats, potentially with undef.
3517 // We are ok with 'shl' having multiple uses, but 'ashr' must be one-use.
3518 if (!match(&I, m_c_ICmp(SrcPred,
3519 m_OneUse(m_AShr(m_Shl(m_Value(X), m_APInt(C0)),
3520 m_APInt(C1))),
3521 m_Deferred(X))))
3522 return nullptr;
3523
3524 // Potential handling of non-splats: for each element:
3525 // * if both are undef, replace with constant 0.
3526 // Because (1<<0) is OK and is 1, and ((1<<0)>>1) is also OK and is 0.
3527 // * if both are not undef, and are different, bailout.
3528 // * else, only one is undef, then pick the non-undef one.
3529
3530 // The shift amount must be equal.
3531 if (*C0 != *C1)
3532 return nullptr;
3533 const APInt &MaskedBits = *C0;
3534 assert(MaskedBits != 0 && "shift by zero should be folded away already.")((void)0);
3535
3536 ICmpInst::Predicate DstPred;
3537 switch (SrcPred) {
3538 case ICmpInst::Predicate::ICMP_EQ:
3539 // ((%x << MaskedBits) a>> MaskedBits) == %x
3540 // =>
3541 // (add %x, (1 << (KeptBits-1))) u< (1 << KeptBits)
3542 DstPred = ICmpInst::Predicate::ICMP_ULT;
3543 break;
3544 case ICmpInst::Predicate::ICMP_NE:
3545 // ((%x << MaskedBits) a>> MaskedBits) != %x
3546 // =>
3547 // (add %x, (1 << (KeptBits-1))) u>= (1 << KeptBits)
3548 DstPred = ICmpInst::Predicate::ICMP_UGE;
3549 break;
3550 // FIXME: are more folds possible?
3551 default:
3552 return nullptr;
3553 }
3554
3555 auto *XType = X->getType();
3556 const unsigned XBitWidth = XType->getScalarSizeInBits();
3557 const APInt BitWidth = APInt(XBitWidth, XBitWidth);
3558 assert(BitWidth.ugt(MaskedBits) && "shifts should leave some bits untouched")((void)0);
3559
3560 // KeptBits = bitwidth(%x) - MaskedBits
3561 const APInt KeptBits = BitWidth - MaskedBits;
3562 assert(KeptBits.ugt(0) && KeptBits.ult(BitWidth) && "unreachable")((void)0);
3563 // ICmpCst = (1 << KeptBits)
3564 const APInt ICmpCst = APInt(XBitWidth, 1).shl(KeptBits);
3565 assert(ICmpCst.isPowerOf2())((void)0);
3566 // AddCst = (1 << (KeptBits-1))
3567 const APInt AddCst = ICmpCst.lshr(1);
3568 assert(AddCst.ult(ICmpCst) && AddCst.isPowerOf2())((void)0);
3569
3570 // T0 = add %x, AddCst
3571 Value *T0 = Builder.CreateAdd(X, ConstantInt::get(XType, AddCst));
3572 // T1 = T0 DstPred ICmpCst
3573 Value *T1 = Builder.CreateICmp(DstPred, T0, ConstantInt::get(XType, ICmpCst));
3574
3575 return T1;
3576}
3577
3578// Given pattern:
3579// icmp eq/ne (and ((x shift Q), (y oppositeshift K))), 0
3580// we should move shifts to the same hand of 'and', i.e. rewrite as
3581// icmp eq/ne (and (x shift (Q+K)), y), 0 iff (Q+K) u< bitwidth(x)
3582// We are only interested in opposite logical shifts here.
3583// One of the shifts can be truncated.
3584// If we can, we want to end up creating 'lshr' shift.
3585static Value *
3586foldShiftIntoShiftInAnotherHandOfAndInICmp(ICmpInst &I, const SimplifyQuery SQ,
3587 InstCombiner::BuilderTy &Builder) {
3588 if (!I.isEquality() || !match(I.getOperand(1), m_Zero()) ||
32
←
Assuming the condition is false
→
34
←
Taking false branch
→
3589 !I.getOperand(0)->hasOneUse())
33
←
Assuming the condition is false
→
3590 return nullptr;
3591
3592 auto m_AnyLogicalShift = m_LogicalShift(m_Value(), m_Value());
3593
3594 // Look for an 'and' of two logical shifts, one of which may be truncated.
3595 // We use m_TruncOrSelf() on the RHS to correctly handle commutative case.
3596 Instruction *XShift, *MaybeTruncation, *YShift;
3597 if (!match(
35
←
Calling 'match<llvm::Value, llvm::PatternMatch::BinaryOp_match<llvm::PatternMatch::match_combine_and<llvm::PatternMatch::BinOpPred_match<llvm::PatternMatch::class_match<llvm::Value>, llvm::PatternMatch::class_match<llvm::Value>, llvm::PatternMatch::is_logical_shift_op>, llvm::PatternMatch::bind_ty<llvm::Instruction>>, llvm::PatternMatch::match_combine_and<llvm::PatternMatch::match_combine_or<llvm::PatternMatch::CastClass_match<llvm::PatternMatch::match_combine_and<llvm::PatternMatch::BinOpPred_match<llvm::PatternMatch::class_match<llvm::Value>, llvm::PatternMatch::class_match<llvm::Value>, llvm::PatternMatch::is_logical_shift_op>, llvm::PatternMatch::bind_ty<llvm::Instruction>>, 38>, llvm::PatternMatch::match_combine_and<llvm::PatternMatch::BinOpPred_match<llvm::PatternMatch::class_match<llvm::Value>, llvm::PatternMatch::class_match<llvm::Value>, llvm::PatternMatch::is_logical_shift_op>, llvm::PatternMatch::bind_ty<llvm::Instruction>>>, llvm::PatternMatch::bind_ty<llvm::Instruction>>, 28, true>>'
→
43
←
Returning from 'match<llvm::Value, llvm::PatternMatch::BinaryOp_match<llvm::PatternMatch::match_combine_and<llvm::PatternMatch::BinOpPred_match<llvm::PatternMatch::class_match<llvm::Value>, llvm::PatternMatch::class_match<llvm::Value>, llvm::PatternMatch::is_logical_shift_op>, llvm::PatternMatch::bind_ty<llvm::Instruction>>, llvm::PatternMatch::match_combine_and<llvm::PatternMatch::match_combine_or<llvm::PatternMatch::CastClass_match<llvm::PatternMatch::match_combine_and<llvm::PatternMatch::BinOpPred_match<llvm::PatternMatch::class_match<llvm::Value>, llvm::PatternMatch::class_match<llvm::Value>, llvm::PatternMatch::is_logical_shift_op>, llvm::PatternMatch::bind_ty<llvm::Instruction>>, 38>, llvm::PatternMatch::match_combine_and<llvm::PatternMatch::BinOpPred_match<llvm::PatternMatch::class_match<llvm::Value>, llvm::PatternMatch::class_match<llvm::Value>, llvm::PatternMatch::is_logical_shift_op>, llvm::PatternMatch::bind_ty<llvm::Instruction>>>, llvm::PatternMatch::bind_ty<llvm::Instruction>>, 28, true>>'
→
44
←
Taking false branch
→
3598 I.getOperand(0),
3599 m_c_And(m_CombineAnd(m_AnyLogicalShift, m_Instruction(XShift)),
3600 m_CombineAnd(m_TruncOrSelf(m_CombineAnd(
3601 m_AnyLogicalShift, m_Instruction(YShift))),
3602 m_Instruction(MaybeTruncation)))))
3603 return nullptr;
3604
3605 // We potentially looked past 'trunc', but only when matching YShift,
3606 // therefore YShift must have the widest type.
3607 Instruction *WidestShift = YShift;
3608 // Therefore XShift must have the shallowest type.
3609 // Or they both have identical types if there was no truncation.
3610 Instruction *NarrowestShift = XShift;
3611
3612 Type *WidestTy = WidestShift->getType();
3613 Type *NarrowestTy = NarrowestShift->getType();
3614 assert(NarrowestTy == I.getOperand(0)->getType() &&((void)0)
3615 "We did not look past any shifts while matching XShift though.")((void)0);
3616 bool HadTrunc = WidestTy != I.getOperand(0)->getType();
45
←
Assuming the condition is false
→
3617
3618 // If YShift is a 'lshr', swap the shifts around.
3619 if (match(YShift, m_LShr(m_Value(), m_Value())))
46
←
Taking false branch
→
3620 std::swap(XShift, YShift);
3621
3622 // The shifts must be in opposite directions.
3623 auto XShiftOpcode = XShift->getOpcode();
3624 if (XShiftOpcode == YShift->getOpcode())
47
←
Assuming the condition is false
→
48
←
Taking false branch
→
3625 return nullptr; // Do not care about same-direction shifts here.
3626
3627 Value *X, *XShAmt, *Y, *YShAmt;
49
←
'XShAmt' declared without an initial value
→
3628 match(XShift, m_BinOp(m_Value(X), m_ZExtOrSelf(m_Value(XShAmt))));
50
←
Calling 'm_Value'
→
54
←
Returning from 'm_Value'
→
55
←
Calling 'm_ZExtOrSelf<llvm::PatternMatch::bind_ty<llvm::Value>>'
→
63
←
Returning from 'm_ZExtOrSelf<llvm::PatternMatch::bind_ty<llvm::Value>>'
→
64
←
Calling 'm_BinOp<llvm::PatternMatch::bind_ty<llvm::Value>, llvm::PatternMatch::match_combine_or<llvm::PatternMatch::CastClass_match<llvm::PatternMatch::bind_ty<llvm::Value>, 39>, llvm::PatternMatch::bind_ty<llvm::Value>>>'
→
66
←
Returning from 'm_BinOp<llvm::PatternMatch::bind_ty<llvm::Value>, llvm::PatternMatch::match_combine_or<llvm::PatternMatch::CastClass_match<llvm::PatternMatch::bind_ty<llvm::Value>, 39>, llvm::PatternMatch::bind_ty<llvm::Value>>>'
→
3629 match(YShift, m_BinOp(m_Value(Y), m_ZExtOrSelf(m_Value(YShAmt))));
3630
3631 // If one of the values being shifted is a constant, then we will end with
3632 // and+icmp, and [zext+]shift instrs will be constant-folded. If they are not,
3633 // however, we will need to ensure that we won't increase instruction count.
3634 if (!isa<Constant>(X) && !isa<Constant>(Y)) {
67
←
Assuming 'X' is a 'Constant'
→
3635 // At least one of the hands of the 'and' should be one-use shift.
3636 if (!match(I.getOperand(0),
3637 m_c_And(m_OneUse(m_AnyLogicalShift), m_Value())))
3638 return nullptr;
3639 if (HadTrunc) {
3640 // Due to the 'trunc', we will need to widen X. For that either the old
3641 // 'trunc' or the shift amt in the non-truncated shift should be one-use.
3642 if (!MaybeTruncation->hasOneUse() &&
3643 !NarrowestShift->getOperand(1)->hasOneUse())
3644 return nullptr;
3645 }
3646 }
3647
3648 // We have two shift amounts from two different shifts. The types of those
3649 // shift amounts may not match. If that's the case let's bailout now.
3650 if (XShAmt->getType() != YShAmt->getType())
68
←
Called C++ object pointer is uninitialized
3651 return nullptr;
3652
3653 // As input, we have the following pattern:
3654 // icmp eq/ne (and ((x shift Q), (y oppositeshift K))), 0
3655 // We want to rewrite that as:
3656 // icmp eq/ne (and (x shift (Q+K)), y), 0 iff (Q+K) u< bitwidth(x)
3657 // While we know that originally (Q+K) would not overflow
3658 // (because 2 * (N-1) u<= iN -1), we have looked past extensions of
3659 // shift amounts. so it may now overflow in smaller bitwidth.
3660 // To ensure that does not happen, we need to ensure that the total maximal
3661 // shift amount is still representable in that smaller bit width.
3662 unsigned MaximalPossibleTotalShiftAmount =
3663 (WidestTy->getScalarSizeInBits() - 1) +
3664 (NarrowestTy->getScalarSizeInBits() - 1);
3665 APInt MaximalRepresentableShiftAmount =
3666 APInt::getAllOnesValue(XShAmt->getType()->getScalarSizeInBits());
3667 if (MaximalRepresentableShiftAmount.ult(MaximalPossibleTotalShiftAmount))
3668 return nullptr;
3669
3670 // Can we fold (XShAmt+YShAmt) ?
3671 auto *NewShAmt = dyn_cast_or_null<Constant>(
3672 SimplifyAddInst(XShAmt, YShAmt, /*isNSW=*/false,
3673 /*isNUW=*/false, SQ.getWithInstruction(&I)));
3674 if (!NewShAmt)
3675 return nullptr;
3676 NewShAmt = ConstantExpr::getZExtOrBitCast(NewShAmt, WidestTy);
3677 unsigned WidestBitWidth = WidestTy->getScalarSizeInBits();
3678
3679 // Is the new shift amount smaller than the bit width?
3680 // FIXME: could also rely on ConstantRange.
3681 if (!match(NewShAmt,
3682 m_SpecificInt_ICMP(ICmpInst::Predicate::ICMP_ULT,
3683 APInt(WidestBitWidth, WidestBitWidth))))
3684 return nullptr;
3685
3686 // An extra legality check is needed if we had trunc-of-lshr.
3687 if (HadTrunc && match(WidestShift, m_LShr(m_Value(), m_Value()))) {
3688 auto CanFold = [NewShAmt, WidestBitWidth, NarrowestShift, SQ,
3689 WidestShift]() {
3690 // It isn't obvious whether it's worth it to analyze non-constants here.
3691 // Also, let's basically give up on non-splat cases, pessimizing vectors.
3692 // If *any* of these preconditions matches we can perform the fold.
3693 Constant *NewShAmtSplat = NewShAmt->getType()->isVectorTy()
3694 ? NewShAmt->getSplatValue()
3695 : NewShAmt;
3696 // If it's edge-case shift (by 0 or by WidestBitWidth-1) we can fold.
3697 if (NewShAmtSplat &&
3698 (NewShAmtSplat->isNullValue() ||
3699 NewShAmtSplat->getUniqueInteger() == WidestBitWidth - 1))
3700 return true;
3701 // We consider *min* leading zeros so a single outlier
3702 // blocks the transform as opposed to allowing it.
3703 if (auto *C = dyn_cast<Constant>(NarrowestShift->getOperand(0))) {
3704 KnownBits Known = computeKnownBits(C, SQ.DL);
3705 unsigned MinLeadZero = Known.countMinLeadingZeros();
3706 // If the value being shifted has at most lowest bit set we can fold.
3707 unsigned MaxActiveBits = Known.getBitWidth() - MinLeadZero;
3708 if (MaxActiveBits <= 1)
3709 return true;
3710 // Precondition: NewShAmt u<= countLeadingZeros(C)
3711 if (NewShAmtSplat && NewShAmtSplat->getUniqueInteger().ule(MinLeadZero))
3712 return true;
3713 }
3714 if (auto *C = dyn_cast<Constant>(WidestShift->getOperand(0))) {
3715 KnownBits Known = computeKnownBits(C, SQ.DL);
3716 unsigned MinLeadZero = Known.countMinLeadingZeros();
3717 // If the value being shifted has at most lowest bit set we can fold.
3718 unsigned MaxActiveBits = Known.getBitWidth() - MinLeadZero;
3719 if (MaxActiveBits <= 1)
3720 return true;
3721 // Precondition: ((WidestBitWidth-1)-NewShAmt) u<= countLeadingZeros(C)
3722 if (NewShAmtSplat) {
3723 APInt AdjNewShAmt =
3724 (WidestBitWidth - 1) - NewShAmtSplat->getUniqueInteger();
3725 if (AdjNewShAmt.ule(MinLeadZero))
3726 return true;
3727 }
3728 }
3729 return false; // Can't tell if it's ok.
3730 };
3731 if (!CanFold())
3732 return nullptr;
3733 }
3734
3735 // All good, we can do this fold.
3736 X = Builder.CreateZExt(X, WidestTy);
3737 Y = Builder.CreateZExt(Y, WidestTy);
3738 // The shift is the same that was for X.
3739 Value *T0 = XShiftOpcode == Instruction::BinaryOps::LShr
3740 ? Builder.CreateLShr(X, NewShAmt)
3741 : Builder.CreateShl(X, NewShAmt);
3742 Value *T1 = Builder.CreateAnd(T0, Y);
3743 return Builder.CreateICmp(I.getPredicate(), T1,
3744 Constant::getNullValue(WidestTy));
3745}
3746
3747/// Fold
3748/// (-1 u/ x) u< y
3749/// ((x * y) u/ x) != y
3750/// to
3751/// @llvm.umul.with.overflow(x, y) plus extraction of overflow bit
3752/// Note that the comparison is commutative, while inverted (u>=, ==) predicate
3753/// will mean that we are looking for the opposite answer.
3754Value *InstCombinerImpl::foldUnsignedMultiplicationOverflowCheck(ICmpInst &I) {
3755 ICmpInst::Predicate Pred;
3756 Value *X, *Y;
3757 Instruction *Mul;
3758 bool NeedNegation;
3759 // Look for: (-1 u/ x) u</u>= y
3760 if (!I.isEquality() &&
3761 match(&I, m_c_ICmp(Pred, m_OneUse(m_UDiv(m_AllOnes(), m_Value(X))),
3762 m_Value(Y)))) {
3763 Mul = nullptr;
3764
3765 // Are we checking that overflow does not happen, or does happen?
3766 switch (Pred) {
3767 case ICmpInst::Predicate::ICMP_ULT:
3768 NeedNegation = false;
3769 break; // OK
3770 case ICmpInst::Predicate::ICMP_UGE:
3771 NeedNegation = true;
3772 break; // OK
3773 default:
3774 return nullptr; // Wrong predicate.
3775 }
3776 } else // Look for: ((x * y) u/ x) !=/== y
3777 if (I.isEquality() &&
3778 match(&I, m_c_ICmp(Pred, m_Value(Y),
3779 m_OneUse(m_UDiv(m_CombineAnd(m_c_Mul(m_Deferred(Y),
3780 m_Value(X)),
3781 m_Instruction(Mul)),
3782 m_Deferred(X)))))) {
3783 NeedNegation = Pred == ICmpInst::Predicate::ICMP_EQ;
3784 } else
3785 return nullptr;
3786
3787 BuilderTy::InsertPointGuard Guard(Builder);
3788 // If the pattern included (x * y), we'll want to insert new instructions
3789 // right before that original multiplication so that we can replace it.
3790 bool MulHadOtherUses = Mul && !Mul->hasOneUse();
3791 if (MulHadOtherUses)
3792 Builder.SetInsertPoint(Mul);
3793
3794 Function *F = Intrinsic::getDeclaration(
3795 I.getModule(), Intrinsic::umul_with_overflow, X->getType());
3796 CallInst *Call = Builder.CreateCall(F, {X, Y}, "umul");
3797
3798 // If the multiplication was used elsewhere, to ensure that we don't leave
3799 // "duplicate" instructions, replace uses of that original multiplication
3800 // with the multiplication result from the with.overflow intrinsic.
3801 if (MulHadOtherUses)
3802 replaceInstUsesWith(*Mul, Builder.CreateExtractValue(Call, 0, "umul.val"));
3803
3804 Value *Res = Builder.CreateExtractValue(Call, 1, "umul.ov");
3805 if (NeedNegation) // This technically increases instruction count.
3806 Res = Builder.CreateNot(Res, "umul.not.ov");
3807
3808 // If we replaced the mul, erase it. Do this after all uses of Builder,
3809 // as the mul is used as insertion point.
3810 if (MulHadOtherUses)
3811 eraseInstFromFunction(*Mul);
3812
3813 return Res;
3814}
3815
3816static Instruction *foldICmpXNegX(ICmpInst &I) {
3817 CmpInst::Predicate Pred;
3818 Value *X;
3819 if (!match(&I, m_c_ICmp(Pred, m_NSWNeg(m_Value(X)), m_Deferred(X))))
3820 return nullptr;
3821
3822 if (ICmpInst::isSigned(Pred))
3823 Pred = ICmpInst::getSwappedPredicate(Pred);
3824 else if (ICmpInst::isUnsigned(Pred))
3825 Pred = ICmpInst::getSignedPredicate(Pred);
3826 // else for equality-comparisons just keep the predicate.
3827
3828 return ICmpInst::Create(Instruction::ICmp, Pred, X,
3829 Constant::getNullValue(X->getType()), I.getName());
3830}
3831
3832/// Try to fold icmp (binop), X or icmp X, (binop).
3833/// TODO: A large part of this logic is duplicated in InstSimplify's
3834/// simplifyICmpWithBinOp(). We should be able to share that and avoid the code
3835/// duplication.
3836Instruction *InstCombinerImpl::foldICmpBinOp(ICmpInst &I,
3837 const SimplifyQuery &SQ) {
3838 const SimplifyQuery Q = SQ.getWithInstruction(&I);
3839 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
3840
3841 // Special logic for binary operators.
3842 BinaryOperator *BO0 = dyn_cast<BinaryOperator>(Op0);
1
Assuming 'Op0' is a 'BinaryOperator'
→
3843 BinaryOperator *BO1 = dyn_cast<BinaryOperator>(Op1);
2
←
Assuming 'Op1' is not a 'BinaryOperator'
→
3844 if (!BO0
2.1
'BO0' is non-null
2.1
'BO0' is non-null
 && !BO1)
3845 return nullptr;
3846
3847 if (Instruction *NewICmp
2.2
'NewICmp' is null
2.2
'NewICmp' is null
 = foldICmpXNegX(I))
3
←
Taking false branch
→
3848 return NewICmp;
3849
3850 const CmpInst::Predicate Pred = I.getPredicate();
3851 Value *X;
3852
3853 // Convert add-with-unsigned-overflow comparisons into a 'not' with compare.
3854 // (Op1 + X) u</u>= Op1 --> ~Op1 u</u>= X
3855 if (match(Op0, m_OneUse(m_c_Add(m_Specific(Op1), m_Value(X)))) &&
4
←
Taking false branch
→
3856 (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_UGE))
3857 return new ICmpInst(Pred, Builder.CreateNot(Op1), X);
3858 // Op0 u>/u<= (Op0 + X) --> X u>/u<= ~Op0
3859 if (match(Op1, m_OneUse(m_c_Add(m_Specific(Op0), m_Value(X)))) &&
5
←
Taking false branch
→
3860 (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_ULE))
3861 return new ICmpInst(Pred, X, Builder.CreateNot(Op0));
3862
3863 bool NoOp0WrapProblem = false, NoOp1WrapProblem = false;
3864 if (BO0
5.1
'BO0' is non-null
5.1
'BO0' is non-null
 && isa<OverflowingBinaryOperator>(BO0))
6
←
Assuming 'BO0' is not a 'OverflowingBinaryOperator'
→
7
←
Taking false branch
→
3865 NoOp0WrapProblem =
3866 ICmpInst::isEquality(Pred) ||
3867 (CmpInst::isUnsigned(Pred) && BO0->hasNoUnsignedWrap()) ||
3868 (CmpInst::isSigned(Pred) && BO0->hasNoSignedWrap());
3869 if (BO1
7.1
'BO1' is null
7.1
'BO1' is null
 && isa<OverflowingBinaryOperator>(BO1))
3870 NoOp1WrapProblem =
3871 ICmpInst::isEquality(Pred) ||
3872 (CmpInst::isUnsigned(Pred) && BO1->hasNoUnsignedWrap()) ||
3873 (CmpInst::isSigned(Pred) && BO1->hasNoSignedWrap());
3874
3875 // Analyze the case when either Op0 or Op1 is an add instruction.
3876 // Op0 = A + B (or A and B are null); Op1 = C + D (or C and D are null).
3877 Value *A = nullptr, *B = nullptr, *C = nullptr, *D = nullptr;
3878 if (BO0
7.2
'BO0' is non-null
7.2
'BO0' is non-null
 && BO0->getOpcode() == Instruction::Add) {
8
←
Assuming the condition is false
→
9
←
Taking false branch
→
3879 A = BO0->getOperand(0);
3880 B = BO0->getOperand(1);
3881 }
3882 if (BO1
9.1
'BO1' is null
9.1
'BO1' is null
 && BO1->getOpcode() == Instruction::Add) {
3883 C = BO1->getOperand(0);
3884 D = BO1->getOperand(1);
3885 }
3886
3887 // icmp (A+B), A -> icmp B, 0 for equalities or if there is no overflow.
3888 // icmp (A+B), B -> icmp A, 0 for equalities or if there is no overflow.
3889 if ((A
9.2
'A' is not equal to 'Op1'
9.2
'A' is not equal to 'Op1'
 == Op1 || B
9.3
'B' is not equal to 'Op1'
9.3
'B' is not equal to 'Op1'
 == Op1) && NoOp0WrapProblem)
3890 return new ICmpInst(Pred, A == Op1 ? B : A,
3891 Constant::getNullValue(Op1->getType()));
3892
3893 // icmp C, (C+D) -> icmp 0, D for equalities or if there is no overflow.
3894 // icmp D, (C+D) -> icmp 0, C for equalities or if there is no overflow.
3895 if ((C
9.4
'C' is not equal to 'Op0'
9.4
'C' is not equal to 'Op0'
 == Op0 || D
9.5
'D' is not equal to 'Op0'
9.5
'D' is not equal to 'Op0'
 == Op0) && NoOp1WrapProblem)
3896 return new ICmpInst(Pred, Constant::getNullValue(Op0->getType()),
3897 C == Op0 ? D : C);
3898
3899 // icmp (A+B), (A+D) -> icmp B, D for equalities or if there is no overflow.
3900 if (A
9.6
'A' is null
9.6
'A' is null
 && C && (A == C || A == D || B == C || B == D) && NoOp0WrapProblem &&
3901 NoOp1WrapProblem) {
3902 // Determine Y and Z in the form icmp (X+Y), (X+Z).
3903 Value *Y, *Z;
3904 if (A == C) {
3905 // C + B == C + D -> B == D
3906 Y = B;
3907 Z = D;
3908 } else if (A == D) {
3909 // D + B == C + D -> B == C
3910 Y = B;
3911 Z = C;
3912 } else if (B == C) {
3913 // A + C == C + D -> A == D
3914 Y = A;
3915 Z = D;
3916 } else {
3917 assert(B == D)((void)0);
3918 // A + D == C + D -> A == C
3919 Y = A;
3920 Z = C;
3921 }
3922 return new ICmpInst(Pred, Y, Z);
3923 }
3924
3925 // icmp slt (A + -1), Op1 -> icmp sle A, Op1
3926 if (A
9.7
'A' is null
9.7
'A' is null
 && NoOp0WrapProblem && Pred == CmpInst::ICMP_SLT &&
10
←
Taking false branch
→
3927 match(B, m_AllOnes()))
3928 return new ICmpInst(CmpInst::ICMP_SLE, A, Op1);
3929
3930 // icmp sge (A + -1), Op1 -> icmp sgt A, Op1
3931 if (A
10.1
'A' is null
10.1
'A' is null
 && NoOp0WrapProblem && Pred == CmpInst::ICMP_SGE &&
11
←
Taking false branch
→
3932 match(B, m_AllOnes()))
3933 return new ICmpInst(CmpInst::ICMP_SGT, A, Op1);
3934
3935 // icmp sle (A + 1), Op1 -> icmp slt A, Op1
3936 if (A
11.1
'A' is null
11.1
'A' is null
 && NoOp0WrapProblem && Pred == CmpInst::ICMP_SLE && match(B, m_One()))
12
←
Taking false branch
→
3937 return new ICmpInst(CmpInst::ICMP_SLT, A, Op1);
3938
3939 // icmp sgt (A + 1), Op1 -> icmp sge A, Op1
3940 if (A
12.1
'A' is null
12.1
'A' is null
 && NoOp0WrapProblem && Pred == CmpInst::ICMP_SGT && match(B, m_One()))
13
←
Taking false branch
→
3941 return new ICmpInst(CmpInst::ICMP_SGE, A, Op1);
3942
3943 // icmp sgt Op0, (C + -1) -> icmp sge Op0, C
3944 if (C
13.1
'C' is null
13.1
'C' is null
 && NoOp1WrapProblem && Pred == CmpInst::ICMP_SGT &&
14
←
Taking false branch
→
3945 match(D, m_AllOnes()))
3946 return new ICmpInst(CmpInst::ICMP_SGE, Op0, C);
3947
3948 // icmp sle Op0, (C + -1) -> icmp slt Op0, C
3949 if (C
14.1
'C' is null
14.1
'C' is null
 && NoOp1WrapProblem && Pred == CmpInst::ICMP_SLE &&
15
←
Taking false branch
→
3950 match(D, m_AllOnes()))
3951 return new ICmpInst(CmpInst::ICMP_SLT, Op0, C);
3952
3953 // icmp sge Op0, (C + 1) -> icmp sgt Op0, C
3954 if (C
15.1
'C' is null
15.1
'C' is null
 && NoOp1WrapProblem && Pred == CmpInst::ICMP_SGE && match(D, m_One()))
16
←
Taking false branch
→
3955 return new ICmpInst(CmpInst::ICMP_SGT, Op0, C);
3956
3957 // icmp slt Op0, (C + 1) -> icmp sle Op0, C
3958 if (C
16.1
'C' is null
16.1
'C' is null
 && NoOp1WrapProblem && Pred == CmpInst::ICMP_SLT && match(D, m_One()))
17
←
Taking false branch
→
3959 return new ICmpInst(CmpInst::ICMP_SLE, Op0, C);
3960
3961 // TODO: The subtraction-related identities shown below also hold, but
3962 // canonicalization from (X -nuw 1) to (X + -1) means that the combinations
3963 // wouldn't happen even if they were implemented.
3964 //
3965 // icmp ult (A - 1), Op1 -> icmp ule A, Op1
3966 // icmp uge (A - 1), Op1 -> icmp ugt A, Op1
3967 // icmp ugt Op0, (C - 1) -> icmp uge Op0, C
3968 // icmp ule Op0, (C - 1) -> icmp ult Op0, C
3969
3970 // icmp ule (A + 1), Op0 -> icmp ult A, Op1
3971 if (A
17.1
'A' is null
17.1
'A' is null
 && NoOp0WrapProblem && Pred == CmpInst::ICMP_ULE && match(B, m_One()))
18
←
Taking false branch
→
3972 return new ICmpInst(CmpInst::ICMP_ULT, A, Op1);
3973
3974 // icmp ugt (A + 1), Op0 -> icmp uge A, Op1
3975 if (A
18.1
'A' is null
18.1
'A' is null
 && NoOp0WrapProblem && Pred == CmpInst::ICMP_UGT && match(B, m_One()))
19
←
Taking false branch
→
3976 return new ICmpInst(CmpInst::ICMP_UGE, A, Op1);
3977
3978 // icmp uge Op0, (C + 1) -> icmp ugt Op0, C
3979 if (C
19.1
'C' is null
19.1
'C' is null
 && NoOp1WrapProblem && Pred == CmpInst::ICMP_UGE && match(D, m_One()))
20
←
Taking false branch
→
3980 return new ICmpInst(CmpInst::ICMP_UGT, Op0, C);
3981
3982 // icmp ult Op0, (C + 1) -> icmp ule Op0, C
3983 if (C
20.1
'C' is null
20.1
'C' is null
 && NoOp1WrapProblem && Pred == CmpInst::ICMP_ULT && match(D, m_One()))
21
←
Taking false branch
→
3984 return new ICmpInst(CmpInst::ICMP_ULE, Op0, C);
3985
3986 // if C1 has greater magnitude than C2:
3987 // icmp (A + C1), (C + C2) -> icmp (A + C3), C
3988 // s.t. C3 = C1 - C2
3989 //
3990 // if C2 has greater magnitude than C1:
3991 // icmp (A + C1), (C + C2) -> icmp A, (C + C3)
3992 // s.t. C3 = C2 - C1
3993 if (A
21.1
'A' is null
21.1
'A' is null
 && C && NoOp0WrapProblem && NoOp1WrapProblem &&
3994 (BO0->hasOneUse() || BO1->hasOneUse()) && !I.isUnsigned())
3995 if (ConstantInt *C1 = dyn_cast<ConstantInt>(B))
3996 if (ConstantInt *C2 = dyn_cast<ConstantInt>(D)) {
3997 const APInt &AP1 = C1->getValue();
3998 const APInt &AP2 = C2->getValue();
3999 if (AP1.isNegative() == AP2.isNegative()) {
4000 APInt AP1Abs = C1->getValue().abs();
4001 APInt AP2Abs = C2->getValue().abs();
4002 if (AP1Abs.uge(AP2Abs)) {
4003 ConstantInt *C3 = Builder.getInt(AP1 - AP2);
4004 bool HasNUW = BO0->hasNoUnsignedWrap() && C3->getValue().ule(AP1);
4005 bool HasNSW = BO0->hasNoSignedWrap();
4006 Value *NewAdd = Builder.CreateAdd(A, C3, "", HasNUW, HasNSW);
4007 return new ICmpInst(Pred, NewAdd, C);
4008 } else {
4009 ConstantInt *C3 = Builder.getInt(AP2 - AP1);
4010 bool HasNUW = BO1->hasNoUnsignedWrap() && C3->getValue().ule(AP2);
4011 bool HasNSW = BO1->hasNoSignedWrap();
4012 Value *NewAdd = Builder.CreateAdd(C, C3, "", HasNUW, HasNSW);
4013 return new ICmpInst(Pred, A, NewAdd);
4014 }
4015 }
4016 }
4017
4018 // Analyze the case when either Op0 or Op1 is a sub instruction.
4019 // Op0 = A - B (or A and B are null); Op1 = C - D (or C and D are null).
4020 A = nullptr;
4021 B = nullptr;
4022 C = nullptr;
4023 D = nullptr;
4024 if (BO0
21.2
'BO0' is non-null
21.2
'BO0' is non-null
 && BO0->getOpcode() == Instruction::Sub) {
22
←
Assuming the condition is false
→
23
←
Taking false branch
→
4025 A = BO0->getOperand(0);
4026 B = BO0->getOperand(1);
4027 }
4028 if (BO1
23.1
'BO1' is null
23.1
'BO1' is null
 && BO1->getOpcode() == Instruction::Sub) {
4029 C = BO1->getOperand(0);
4030 D = BO1->getOperand(1);
4031 }
4032
4033 // icmp (A-B), A -> icmp 0, B for equalities or if there is no overflow.
4034 if (A
23.2
'A' is not equal to 'Op1'
23.2
'A' is not equal to 'Op1'
 == Op1 && NoOp0WrapProblem)
4035 return new ICmpInst(Pred, Constant::getNullValue(Op1->getType()), B);
4036 // icmp C, (C-D) -> icmp D, 0 for equalities or if there is no overflow.
4037 if (C
23.3
'C' is not equal to 'Op0'
23.3
'C' is not equal to 'Op0'
 == Op0 && NoOp1WrapProblem)
4038 return new ICmpInst(Pred, D, Constant::getNullValue(Op0->getType()));
4039
4040 // Convert sub-with-unsigned-overflow comparisons into a comparison of args.
4041 // (A - B) u>/u<= A --> B u>/u<= A
4042 if (A
23.4
'A' is not equal to 'Op1'
23.4
'A' is not equal to 'Op1'
 == Op1 && (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_ULE))
4043 return new ICmpInst(Pred, B, A);
4044 // C u</u>= (C - D) --> C u</u>= D
4045 if (C
23.5
'C' is not equal to 'Op0'
23.5
'C' is not equal to 'Op0'
 == Op0 && (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_UGE))
4046 return new ICmpInst(Pred, C, D);
4047 // (A - B) u>=/u< A --> B u>/u<= A iff B != 0
4048 if (A
23.6
'A' is not equal to 'Op1'
23.6
'A' is not equal to 'Op1'
 == Op1 && (Pred == ICmpInst::ICMP_UGE || Pred == ICmpInst::ICMP_ULT) &&
4049 isKnownNonZero(B, Q.DL, /*Depth=*/0, Q.AC, Q.CxtI, Q.DT))
4050 return new ICmpInst(CmpInst::getFlippedStrictnessPredicate(Pred), B, A);
4051 // C u<=/u> (C - D) --> C u</u>= D iff B != 0
4052 if (C
23.7
'C' is not equal to 'Op0'
23.7
'C' is not equal to 'Op0'
 == Op0 && (Pred == ICmpInst::ICMP_ULE || Pred == ICmpInst::ICMP_UGT) &&
4053 isKnownNonZero(D, Q.DL, /*Depth=*/0, Q.AC, Q.CxtI, Q.DT))
4054 return new ICmpInst(CmpInst::getFlippedStrictnessPredicate(Pred), C, D);
4055
4056 // icmp (A-B), (C-B) -> icmp A, C for equalities or if there is no overflow.
4057 if (B
23.8
'B' is null
23.8
'B' is null
 && D && B == D && NoOp0WrapProblem && NoOp1WrapProblem)
4058 return new ICmpInst(Pred, A, C);
4059
4060 // icmp (A-B), (A-D) -> icmp D, B for equalities or if there is no overflow.
4061 if (A
23.9
'A' is null
23.9
'A' is null
 && C && A == C && NoOp0WrapProblem && NoOp1WrapProblem)
4062 return new ICmpInst(Pred, D, B);
4063
4064 // icmp (0-X) < cst --> x > -cst
4065 if (NoOp0WrapProblem
23.10
'NoOp0WrapProblem' is false
23.10
'NoOp0WrapProblem' is false
 && ICmpInst::isSigned(Pred)) {
4066 Value *X;
4067 if (match(BO0, m_Neg(m_Value(X))))
4068 if (Constant *RHSC = dyn_cast<Constant>(Op1))
4069 if (RHSC->isNotMinSignedValue())
4070 return new ICmpInst(I.getSwappedPredicate(), X,
4071 ConstantExpr::getNeg(RHSC));
4072 }
4073
4074 {
4075 // Try to remove shared constant multiplier from equality comparison:
4076 // X * C == Y * C (with no overflowing/aliasing) --> X == Y
4077 Value *X, *Y;
4078 const APInt *C;
4079 if (match(Op0, m_Mul(m_Value(X), m_APInt(C))) && *C != 0 &&
24
←
Taking false branch
→
4080 match(Op1, m_Mul(m_Value(Y), m_SpecificInt(*C))) && I.isEquality())
4081 if (!C->countTrailingZeros() ||
4082 (BO0->hasNoSignedWrap() && BO1->hasNoSignedWrap()) ||
4083 (BO0->hasNoUnsignedWrap() && BO1->hasNoUnsignedWrap()))
4084 return new ICmpInst(Pred, X, Y);
4085 }
4086
4087 BinaryOperator *SRem = nullptr;
4088 // icmp (srem X, Y), Y
4089 if (BO0
24.1
'BO0' is non-null
24.1
'BO0' is non-null
 && BO0->getOpcode() == Instruction::SRem && Op1 == BO0->getOperand(1))
25
←
Assuming the condition is false
→
4090 SRem = BO0;
4091 // icmp Y, (srem X, Y)
4092 else if (BO1
25.1
'BO1' is null
25.1
'BO1' is null
 && BO1->getOpcode() == Instruction::SRem &&
4093 Op0 == BO1->getOperand(1))
4094 SRem = BO1;
4095 if (SRem
25.2
'SRem' is null
25.2
'SRem' is null
) {
26
←
Taking false branch
→
4096 // We don't check hasOneUse to avoid increasing register pressure because
4097 // the value we use is the same value this instruction was already using.
4098 switch (SRem == BO0 ? ICmpInst::getSwappedPredicate(Pred) : Pred) {
4099 default:
4100 break;
4101 case ICmpInst::ICMP_EQ:
4102 return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4103 case ICmpInst::ICMP_NE:
4104 return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4105 case ICmpInst::ICMP_SGT:
4106 case ICmpInst::ICMP_SGE:
4107 return new ICmpInst(ICmpInst::ICMP_SGT, SRem->getOperand(1),
4108 Constant::getAllOnesValue(SRem->getType()));
4109 case ICmpInst::ICMP_SLT:
4110 case ICmpInst::ICMP_SLE:
4111 return new ICmpInst(ICmpInst::ICMP_SLT, SRem->getOperand(1),
4112 Constant::getNullValue(SRem->getType()));
4113 }
4114 }
4115
4116 if (BO0
26.1
'BO0' is non-null
26.1
'BO0' is non-null
 && BO1
26.2
'BO1' is null
26.2
'BO1' is null
 && BO0->getOpcode() == BO1->getOpcode() && BO0->hasOneUse() &&
4117 BO1->hasOneUse() && BO0->getOperand(1) == BO1->getOperand(1)) {
4118 switch (BO0->getOpcode()) {
4119 default:
4120 break;
4121 case Instruction::Add:
4122 case Instruction::Sub:
4123 case Instruction::Xor: {
4124 if (I.isEquality()) // a+x icmp eq/ne b+x --> a icmp b
4125 return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
4126
4127 const APInt *C;
4128 if (match(BO0->getOperand(1), m_APInt(C))) {
4129 // icmp u/s (a ^ signmask), (b ^ signmask) --> icmp s/u a, b
4130 if (C->isSignMask()) {
4131 ICmpInst::Predicate NewPred = I.getFlippedSignednessPredicate();
4132 return new ICmpInst(NewPred, BO0->getOperand(0), BO1->getOperand(0));
4133 }
4134
4135 // icmp u/s (a ^ maxsignval), (b ^ maxsignval) --> icmp s/u' a, b
4136 if (BO0->getOpcode() == Instruction::Xor && C->isMaxSignedValue()) {
4137 ICmpInst::Predicate NewPred = I.getFlippedSignednessPredicate();
4138 NewPred = I.getSwappedPredicate(NewPred);
4139 return new ICmpInst(NewPred, BO0->getOperand(0), BO1->getOperand(0));
4140 }
4141 }
4142 break;
4143 }
4144 case Instruction::Mul: {
4145 if (!I.isEquality())
4146 break;
4147
4148 const APInt *C;
4149 if (match(BO0->getOperand(1), m_APInt(C)) && !C->isNullValue() &&
4150 !C->isOneValue()) {
4151 // icmp eq/ne (X * C), (Y * C) --> icmp (X & Mask), (Y & Mask)
4152 // Mask = -1 >> count-trailing-zeros(C).
4153 if (unsigned TZs = C->countTrailingZeros()) {
4154 Constant *Mask = ConstantInt::get(
4155 BO0->getType(),
4156 APInt::getLowBitsSet(C->getBitWidth(), C->getBitWidth() - TZs));
4157 Value *And1 = Builder.CreateAnd(BO0->getOperand(0), Mask);
4158 Value *And2 = Builder.CreateAnd(BO1->getOperand(0), Mask);
4159 return new ICmpInst(Pred, And1, And2);
4160 }
4161 }
4162 break;
4163 }
4164 case Instruction::UDiv:
4165 case Instruction::LShr:
4166 if (I.isSigned() || !BO0->isExact() || !BO1->isExact())
4167 break;
4168 return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
4169
4170 case Instruction::SDiv:
4171 if (!I.isEquality() || !BO0->isExact() || !BO1->isExact())
4172 break;
4173 return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
4174
4175 case Instruction::AShr:
4176 if (!BO0->isExact() || !BO1->isExact())
4177 break;
4178 return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
4179
4180 case Instruction::Shl: {
4181 bool NUW = BO0->hasNoUnsignedWrap() && BO1->hasNoUnsignedWrap();
4182 bool NSW = BO0->hasNoSignedWrap() && BO1->hasNoSignedWrap();
4183 if (!NUW && !NSW)
4184 break;
4185 if (!NSW && I.isSigned())
4186 break;
4187 return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
4188 }
4189 }
4190 }
4191
4192 if (BO0
26.3
'BO0' is non-null
26.3
'BO0' is non-null
) {
27
←
Taking true branch
→
4193 // Transform A & (L - 1) `ult` L --> L != 0
4194 auto LSubOne = m_Add(m_Specific(Op1), m_AllOnes());
4195 auto BitwiseAnd = m_c_And(m_Value(), LSubOne);
4196
4197 if (match(BO0, BitwiseAnd) && Pred == ICmpInst::ICMP_ULT) {
4198 auto *Zero = Constant::getNullValue(BO0->getType());
4199 return new ICmpInst(ICmpInst::ICMP_NE, Op1, Zero);
4200 }
4201 }
4202
4203 if (Value *V
27.1
'V' is null
27.1
'V' is null
 = foldUnsignedMultiplicationOverflowCheck(I))
28
←
Taking false branch
→
4204 return replaceInstUsesWith(I, V);
4205
4206 if (Value *V
28.1
'V' is null
28.1
'V' is null
 = foldICmpWithLowBitMaskedVal(I, Builder))
29
←
Taking false branch
→
4207 return replaceInstUsesWith(I, V);
4208
4209 if (Value *V
29.1
'V' is null
29.1
'V' is null
 = foldICmpWithTruncSignExtendedVal(I, Builder))
30
←
Taking false branch
→
4210 return replaceInstUsesWith(I, V);
4211
4212 if (Value *V = foldShiftIntoShiftInAnotherHandOfAndInICmp(I, SQ, Builder))
31
←
Calling 'foldShiftIntoShiftInAnotherHandOfAndInICmp'
→
4213 return replaceInstUsesWith(I, V);
4214
4215 return nullptr;
4216}
4217
4218/// Fold icmp Pred min|max(X, Y), X.
4219static Instruction *foldICmpWithMinMax(ICmpInst &Cmp) {
4220 ICmpInst::Predicate Pred = Cmp.getPredicate();
4221 Value *Op0 = Cmp.getOperand(0);
4222 Value *X = Cmp.getOperand(1);
4223
4224 // Canonicalize minimum or maximum operand to LHS of the icmp.
4225 if (match(X, m_c_SMin(m_Specific(Op0), m_Value())) ||
4226 match(X, m_c_SMax(m_Specific(Op0), m_Value())) ||
4227 match(X, m_c_UMin(m_Specific(Op0), m_Value())) ||
4228 match(X, m_c_UMax(m_Specific(Op0), m_Value()))) {
4229 std::swap(Op0, X);
4230 Pred = Cmp.getSwappedPredicate();
4231 }
4232
4233 Value *Y;
4234 if (match(Op0, m_c_SMin(m_Specific(X), m_Value(Y)))) {
4235 // smin(X, Y) == X --> X s<= Y
4236 // smin(X, Y) s>= X --> X s<= Y
4237 if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_SGE)
4238 return new ICmpInst(ICmpInst::ICMP_SLE, X, Y);
4239
4240 // smin(X, Y) != X --> X s> Y
4241 // smin(X, Y) s< X --> X s> Y
4242 if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::ICMP_SLT)
4243 return new ICmpInst(ICmpInst::ICMP_SGT, X, Y);
4244
4245 // These cases should be handled in InstSimplify:
4246 // smin(X, Y) s<= X --> true
4247 // smin(X, Y) s> X --> false
4248 return nullptr;
4249 }
4250
4251 if (match(Op0, m_c_SMax(m_Specific(X), m_Value(Y)))) {
4252 // smax(X, Y) == X --> X s>= Y
4253 // smax(X, Y) s<= X --> X s>= Y
4254 if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_SLE)
4255 return new ICmpInst(ICmpInst::ICMP_SGE, X, Y);
4256
4257 // smax(X, Y) != X --> X s< Y
4258 // smax(X, Y) s> X --> X s< Y
4259 if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::ICMP_SGT)
4260 return new ICmpInst(ICmpInst::ICMP_SLT, X, Y);
4261
4262 // These cases should be handled in InstSimplify:
4263 // smax(X, Y) s>= X --> true
4264 // smax(X, Y) s< X --> false
4265 return nullptr;
4266 }
4267
4268 if (match(Op0, m_c_UMin(m_Specific(X), m_Value(Y)))) {
4269 // umin(X, Y) == X --> X u<= Y
4270 // umin(X, Y) u>= X --> X u<= Y
4271 if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_UGE)
4272 return new ICmpInst(ICmpInst::ICMP_ULE, X, Y);
4273
4274 // umin(X, Y) != X --> X u> Y
4275 // umin(X, Y) u< X --> X u> Y
4276 if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::ICMP_ULT)
4277 return new ICmpInst(ICmpInst::ICMP_UGT, X, Y);
4278
4279 // These cases should be handled in InstSimplify:
4280 // umin(X, Y) u<= X --> true
4281 // umin(X, Y) u> X --> false
4282 return nullptr;
4283 }
4284
4285 if (match(Op0, m_c_UMax(m_Specific(X), m_Value(Y)))) {
4286 // umax(X, Y) == X --> X u>= Y
4287 // umax(X, Y) u<= X --> X u>= Y
4288 if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_ULE)
4289 return new ICmpInst(ICmpInst::ICMP_UGE, X, Y);
4290
4291 // umax(X, Y) != X --> X u< Y
4292 // umax(X, Y) u> X --> X u< Y
4293 if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::ICMP_UGT)
4294 return new ICmpInst(ICmpInst::ICMP_ULT, X, Y);
4295
4296 // These cases should be handled in InstSimplify:
4297 // umax(X, Y) u>= X --> true
4298 // umax(X, Y) u< X --> false
4299 return nullptr;
4300 }
4301
4302 return nullptr;
4303}
4304
4305Instruction *InstCombinerImpl::foldICmpEquality(ICmpInst &I) {
4306 if (!I.isEquality())
4307 return nullptr;
4308
4309 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
4310 const CmpInst::Predicate Pred = I.getPredicate();
4311 Value *A, *B, *C, *D;
4312 if (match(Op0, m_Xor(m_Value(A), m_Value(B)))) {
4313 if (A == Op1 || B == Op1) { // (A^B) == A -> B == 0
4314 Value *OtherVal = A == Op1 ? B : A;
4315 return new ICmpInst(Pred, OtherVal, Constant::getNullValue(A->getType()));
4316 }
4317
4318 if (match(Op1, m_Xor(m_Value(C), m_Value(D)))) {
4319 // A^c1 == C^c2 --> A == C^(c1^c2)
4320 ConstantInt *C1, *C2;
4321 if (match(B, m_ConstantInt(C1)) && match(D, m_ConstantInt(C2)) &&
4322 Op1->hasOneUse()) {
4323 Constant *NC = Builder.getInt(C1->getValue() ^ C2->getValue());
4324 Value *Xor = Builder.CreateXor(C, NC);
4325 return new ICmpInst(Pred, A, Xor);
4326 }
4327
4328 // A^B == A^D -> B == D
4329 if (A == C)
4330 return new ICmpInst(Pred, B, D);
4331 if (A == D)
4332 return new ICmpInst(Pred, B, C);
4333 if (B == C)
4334 return new ICmpInst(Pred, A, D);
4335 if (B == D)
4336 return new ICmpInst(Pred, A, C);
4337 }
4338 }
4339
4340 if (match(Op1, m_Xor(m_Value(A), m_Value(B))) && (A == Op0 || B == Op0)) {
4341 // A == (A^B) -> B == 0
4342 Value *OtherVal = A == Op0 ? B : A;
4343 return new ICmpInst(Pred, OtherVal, Constant::getNullValue(A->getType()));
4344 }
4345
4346 // (X&Z) == (Y&Z) -> (X^Y) & Z == 0
4347 if (match(Op0, m_OneUse(m_And(m_Value(A), m_Value(B)))) &&
4348 match(Op1, m_OneUse(m_And(m_Value(C), m_Value(D))))) {
4349 Value *X = nullptr, *Y = nullptr, *Z = nullptr;
4350
4351 if (A == C) {
4352 X = B;
4353 Y = D;
4354 Z = A;
4355 } else if (A == D) {
4356 X = B;
4357 Y = C;
4358 Z = A;
4359 } else if (B == C) {
4360 X = A;
4361 Y = D;
4362 Z = B;
4363 } else if (B == D) {
4364 X = A;
4365 Y = C;
4366 Z = B;
4367 }
4368
4369 if (X) { // Build (X^Y) & Z
4370 Op1 = Builder.CreateXor(X, Y);
4371 Op1 = Builder.CreateAnd(Op1, Z);
4372 return new ICmpInst(Pred, Op1, Constant::getNullValue(Op1->getType()));
4373 }
4374 }
4375
4376 // Transform (zext A) == (B & (1<<X)-1) --> A == (trunc B)
4377 // and (B & (1<<X)-1) == (zext A) --> A == (trunc B)
4378 ConstantInt *Cst1;
4379 if ((Op0->hasOneUse() && match(Op0, m_ZExt(m_Value(A))) &&
4380 match(Op1, m_And(m_Value(B), m_ConstantInt(Cst1)))) ||
4381 (Op1->hasOneUse() && match(Op0, m_And(m_Value(B), m_ConstantInt(Cst1))) &&
4382 match(Op1, m_ZExt(m_Value(A))))) {
4383 APInt Pow2 = Cst1->getValue() + 1;
4384 if (Pow2.isPowerOf2() && isa<IntegerType>(A->getType()) &&
4385 Pow2.logBase2() == cast<IntegerType>(A->getType())->getBitWidth())
4386 return new ICmpInst(Pred, A, Builder.CreateTrunc(B, A->getType()));
4387 }
4388
4389 // (A >> C) == (B >> C) --> (A^B) u< (1 << C)
4390 // For lshr and ashr pairs.
4391 if ((match(Op0, m_OneUse(m_LShr(m_Value(A), m_ConstantInt(Cst1)))) &&
4392 match(Op1, m_OneUse(m_LShr(m_Value(B), m_Specific(Cst1))))) ||
4393 (match(Op0, m_OneUse(m_AShr(m_Value(A), m_ConstantInt(Cst1)))) &&
4394 match(Op1, m_OneUse(m_AShr(m_Value(B), m_Specific(Cst1)))))) {
4395 unsigned TypeBits = Cst1->getBitWidth();
4396 unsigned ShAmt = (unsigned)Cst1->getLimitedValue(TypeBits);
4397 if (ShAmt < TypeBits && ShAmt != 0) {
4398 ICmpInst::Predicate NewPred =
4399 Pred == ICmpInst::ICMP_NE ? ICmpInst::ICMP_UGE : ICmpInst::ICMP_ULT;
4400 Value *Xor = Builder.CreateXor(A, B, I.getName() + ".unshifted");
4401 APInt CmpVal = APInt::getOneBitSet(TypeBits, ShAmt);
4402 return new ICmpInst(NewPred, Xor, Builder.getInt(CmpVal));
4403 }
4404 }
4405
4406 // (A << C) == (B << C) --> ((A^B) & (~0U >> C)) == 0
4407 if (match(Op0, m_OneUse(m_Shl(m_Value(A), m_ConstantInt(Cst1)))) &&
4408 match(Op1, m_OneUse(m_Shl(m_Value(B), m_Specific(Cst1))))) {
4409 unsigned TypeBits = Cst1->getBitWidth();
4410 unsigned ShAmt = (unsigned)Cst1->getLimitedValue(TypeBits);
4411 if (ShAmt < TypeBits && ShAmt != 0) {
4412 Value *Xor = Builder.CreateXor(A, B, I.getName() + ".unshifted");
4413 APInt AndVal = APInt::getLowBitsSet(TypeBits, TypeBits - ShAmt);
4414 Value *And = Builder.CreateAnd(Xor, Builder.getInt(AndVal),
4415 I.getName() + ".mask");
4416 return new ICmpInst(Pred, And, Constant::getNullValue(Cst1->getType()));
4417 }
4418 }
4419
4420 // Transform "icmp eq (trunc (lshr(X, cst1)), cst" to
4421 // "icmp (and X, mask), cst"
4422 uint64_t ShAmt = 0;
4423 if (Op0->hasOneUse() &&
4424 match(Op0, m_Trunc(m_OneUse(m_LShr(m_Value(A), m_ConstantInt(ShAmt))))) &&
4425 match(Op1, m_ConstantInt(Cst1)) &&
4426 // Only do this when A has multiple uses. This is most important to do
4427 // when it exposes other optimizations.
4428 !A->hasOneUse()) {
4429 unsigned ASize = cast<IntegerType>(A->getType())->getPrimitiveSizeInBits();
4430
4431 if (ShAmt < ASize) {
4432 APInt MaskV =
4433 APInt::getLowBitsSet(ASize, Op0->getType()->getPrimitiveSizeInBits());
4434 MaskV <<= ShAmt;
4435
4436 APInt CmpV = Cst1->getValue().zext(ASize);
4437 CmpV <<= ShAmt;
4438
4439 Value *Mask = Builder.CreateAnd(A, Builder.getInt(MaskV));
4440 return new ICmpInst(Pred, Mask, Builder.getInt(CmpV));
4441 }
4442 }
4443
4444 // If both operands are byte-swapped or bit-reversed, just compare the
4445 // original values.
4446 // TODO: Move this to a function similar to foldICmpIntrinsicWithConstant()
4447 // and handle more intrinsics.
4448 if ((match(Op0, m_BSwap(m_Value(A))) && match(Op1, m_BSwap(m_Value(B)))) ||
4449 (match(Op0, m_BitReverse(m_Value(A))) &&
4450 match(Op1, m_BitReverse(m_Value(B)))))
4451 return new ICmpInst(Pred, A, B);
4452
4453 // Canonicalize checking for a power-of-2-or-zero value:
4454 // (A & (A-1)) == 0 --> ctpop(A) < 2 (two commuted variants)
4455 // ((A-1) & A) != 0 --> ctpop(A) > 1 (two commuted variants)
4456 if (!match(Op0, m_OneUse(m_c_And(m_Add(m_Value(A), m_AllOnes()),
4457 m_Deferred(A)))) ||
4458 !match(Op1, m_ZeroInt()))
4459 A = nullptr;
4460
4461 // (A & -A) == A --> ctpop(A) < 2 (four commuted variants)
4462 // (-A & A) != A --> ctpop(A) > 1 (four commuted variants)
4463 if (match(Op0, m_OneUse(m_c_And(m_Neg(m_Specific(Op1)), m_Specific(Op1)))))
4464 A = Op1;
4465 else if (match(Op1,
4466 m_OneUse(m_c_And(m_Neg(m_Specific(Op0)), m_Specific(Op0)))))
4467 A = Op0;
4468
4469 if (A) {
4470 Type *Ty = A->getType();
4471 CallInst *CtPop = Builder.CreateUnaryIntrinsic(Intrinsic::ctpop, A);
4472 return Pred == ICmpInst::ICMP_EQ
4473 ? new ICmpInst(ICmpInst::ICMP_ULT, CtPop, ConstantInt::get(Ty, 2))
4474 : new ICmpInst(ICmpInst::ICMP_UGT, CtPop, ConstantInt::get(Ty, 1));
4475 }
4476
4477 return nullptr;
4478}
4479
4480static Instruction *foldICmpWithZextOrSext(ICmpInst &ICmp,
4481 InstCombiner::BuilderTy &Builder) {
4482 assert(isa<CastInst>(ICmp.getOperand(0)) && "Expected cast for operand 0")((void)0);
4483 auto *CastOp0 = cast<CastInst>(ICmp.getOperand(0));
4484 Value *X;
4485 if (!match(CastOp0, m_ZExtOrSExt(m_Value(X))))
4486 return nullptr;
4487
4488 bool IsSignedExt = CastOp0->getOpcode() == Instruction::SExt;
4489 bool IsSignedCmp = ICmp.isSigned();
4490 if (auto *CastOp1 = dyn_cast<CastInst>(ICmp.getOperand(1))) {
4491 // If the signedness of the two casts doesn't agree (i.e. one is a sext
4492 // and the other is a zext), then we can't handle this.
4493 // TODO: This is too strict. We can handle some predicates (equality?).
4494 if (CastOp0->getOpcode() != CastOp1->getOpcode())
4495 return nullptr;
4496
4497 // Not an extension from the same type?
4498 Value *Y = CastOp1->getOperand(0);
4499 Type *XTy = X->getType(), *YTy = Y->getType();
4500 if (XTy != YTy) {
4501 // One of the casts must have one use because we are creating a new cast.
4502 if (!CastOp0->hasOneUse() && !CastOp1->hasOneUse())
4503 return nullptr;
4504 // Extend the narrower operand to the type of the wider operand.
4505 if (XTy->getScalarSizeInBits() < YTy->getScalarSizeInBits())
4506 X = Builder.CreateCast(CastOp0->getOpcode(), X, YTy);
4507 else if (YTy->getScalarSizeInBits() < XTy->getScalarSizeInBits())
4508 Y = Builder.CreateCast(CastOp0->getOpcode(), Y, XTy);
4509 else
4510 return nullptr;
4511 }
4512
4513 // (zext X) == (zext Y) --> X == Y
4514 // (sext X) == (sext Y) --> X == Y
4515 if (ICmp.isEquality())
4516 return new ICmpInst(ICmp.getPredicate(), X, Y);
4517
4518 // A signed comparison of sign extended values simplifies into a
4519 // signed comparison.
4520 if (IsSignedCmp && IsSignedExt)
4521 return new ICmpInst(ICmp.getPredicate(), X, Y);
4522
4523 // The other three cases all fold into an unsigned comparison.
4524 return new ICmpInst(ICmp.getUnsignedPredicate(), X, Y);
4525 }
4526
4527 // Below here, we are only folding a compare with constant.
4528 auto *C = dyn_cast<Constant>(ICmp.getOperand(1));
4529 if (!C)
4530 return nullptr;
4531
4532 // Compute the constant that would happen if we truncated to SrcTy then
4533 // re-extended to DestTy.
4534 Type *SrcTy = CastOp0->getSrcTy();
4535 Type *DestTy = CastOp0->getDestTy();
4536 Constant *Res1 = ConstantExpr::getTrunc(C, SrcTy);
4537 Constant *Res2 = ConstantExpr::getCast(CastOp0->getOpcode(), Res1, DestTy);
4538
4539 // If the re-extended constant didn't change...
4540 if (Res2 == C) {
4541 if (ICmp.isEquality())
4542 return new ICmpInst(ICmp.getPredicate(), X, Res1);
4543
4544 // A signed comparison of sign extended values simplifies into a
4545 // signed comparison.
4546 if (IsSignedExt && IsSignedCmp)
4547 return new ICmpInst(ICmp.getPredicate(), X, Res1);
4548
4549 // The other three cases all fold into an unsigned comparison.
4550 return new ICmpInst(ICmp.getUnsignedPredicate(), X, Res1);
4551 }
4552
4553 // The re-extended constant changed, partly changed (in the case of a vector),
4554 // or could not be determined to be equal (in the case of a constant
4555 // expression), so the constant cannot be represented in the shorter type.
4556 // All the cases that fold to true or false will have already been handled
4557 // by SimplifyICmpInst, so only deal with the tricky case.
4558 if (IsSignedCmp || !IsSignedExt || !isa<ConstantInt>(C))
4559 return nullptr;
4560
4561 // Is source op positive?
4562 // icmp ult (sext X), C --> icmp sgt X, -1
4563 if (ICmp.getPredicate() == ICmpInst::ICMP_ULT)
4564 return new ICmpInst(CmpInst::ICMP_SGT, X, Constant::getAllOnesValue(SrcTy));
4565
4566 // Is source op negative?
4567 // icmp ugt (sext X), C --> icmp slt X, 0
4568 assert(ICmp.getPredicate() == ICmpInst::ICMP_UGT && "ICmp should be folded!")((void)0);
4569 return new ICmpInst(CmpInst::ICMP_SLT, X, Constant::getNullValue(SrcTy));
4570}
4571
4572/// Handle icmp (cast x), (cast or constant).
4573Instruction *InstCombinerImpl::foldICmpWithCastOp(ICmpInst &ICmp) {
4574 // If any operand of ICmp is a inttoptr roundtrip cast then remove it as
4575 // icmp compares only pointer's value.
4576 // icmp (inttoptr (ptrtoint p1)), p2 --> icmp p1, p2.
4577 Value *SimplifiedOp0 = simplifyIntToPtrRoundTripCast(ICmp.getOperand(0));
4578 Value *SimplifiedOp1 = simplifyIntToPtrRoundTripCast(ICmp.getOperand(1));
4579 if (SimplifiedOp0 || SimplifiedOp1)
4580 return new ICmpInst(ICmp.getPredicate(),
4581 SimplifiedOp0 ? SimplifiedOp0 : ICmp.getOperand(0),
4582 SimplifiedOp1 ? SimplifiedOp1 : ICmp.getOperand(1));
4583
4584 auto *CastOp0 = dyn_cast<CastInst>(ICmp.getOperand(0));
4585 if (!CastOp0)
4586 return nullptr;
4587 if (!isa<Constant>(ICmp.getOperand(1)) && !isa<CastInst>(ICmp.getOperand(1)))
4588 return nullptr;
4589
4590 Value *Op0Src = CastOp0->getOperand(0);
4591 Type *SrcTy = CastOp0->getSrcTy();
4592 Type *DestTy = CastOp0->getDestTy();
4593
4594 // Turn icmp (ptrtoint x), (ptrtoint/c) into a compare of the input if the
4595 // integer type is the same size as the pointer type.
4596 auto CompatibleSizes = [&](Type *SrcTy, Type *DestTy) {
4597 if (isa<VectorType>(SrcTy)) {
4598 SrcTy = cast<VectorType>(SrcTy)->getElementType();
4599 DestTy = cast<VectorType>(DestTy)->getElementType();
4600 }
4601 return DL.getPointerTypeSizeInBits(SrcTy) == DestTy->getIntegerBitWidth();
4602 };
4603 if (CastOp0->getOpcode() == Instruction::PtrToInt &&
4604 CompatibleSizes(SrcTy, DestTy)) {
4605 Value *NewOp1 = nullptr;
4606 if (auto *PtrToIntOp1 = dyn_cast<PtrToIntOperator>(ICmp.getOperand(1))) {
4607 Value *PtrSrc = PtrToIntOp1->getOperand(0);
4608 if (PtrSrc->getType()->getPointerAddressSpace() ==
4609 Op0Src->getType()->getPointerAddressSpace()) {
4610 NewOp1 = PtrToIntOp1->getOperand(0);
4611 // If the pointer types don't match, insert a bitcast.
4612 if (Op0Src->getType() != NewOp1->getType())
4613 NewOp1 = Builder.CreateBitCast(NewOp1, Op0Src->getType());
4614 }
4615 } else if (auto *RHSC = dyn_cast<Constant>(ICmp.getOperand(1))) {
4616 NewOp1 = ConstantExpr::getIntToPtr(RHSC, SrcTy);
4617 }
4618
4619 if (NewOp1)
4620 return new ICmpInst(ICmp.getPredicate(), Op0Src, NewOp1);
4621 }
4622
4623 return foldICmpWithZextOrSext(ICmp, Builder);
4624}
4625
4626static bool isNeutralValue(Instruction::BinaryOps BinaryOp, Value *RHS) {
4627 switch (BinaryOp) {
4628 default:
4629 llvm_unreachable("Unsupported binary op")__builtin_unreachable();
4630 case Instruction::Add:
4631 case Instruction::Sub:
4632 return match(RHS, m_Zero());
4633 case Instruction::Mul:
4634 return match(RHS, m_One());
4635 }
4636}
4637
4638OverflowResult
4639InstCombinerImpl::computeOverflow(Instruction::BinaryOps BinaryOp,
4640 bool IsSigned, Value *LHS, Value *RHS,
4641 Instruction *CxtI) const {
4642 switch (BinaryOp) {
4643 default:
4644 llvm_unreachable("Unsupported binary op")__builtin_unreachable();
4645 case Instruction::Add:
4646 if (IsSigned)
4647 return computeOverflowForSignedAdd(LHS, RHS, CxtI);
4648 else
4649 return computeOverflowForUnsignedAdd(LHS, RHS, CxtI);
4650 case Instruction::Sub:
4651 if (IsSigned)
4652 return computeOverflowForSignedSub(LHS, RHS, CxtI);
4653 else
4654 return computeOverflowForUnsignedSub(LHS, RHS, CxtI);
4655 case Instruction::Mul:
4656 if (IsSigned)
4657 return computeOverflowForSignedMul(LHS, RHS, CxtI);
4658 else
4659 return computeOverflowForUnsignedMul(LHS, RHS, CxtI);
4660 }
4661}
4662
4663bool InstCombinerImpl::OptimizeOverflowCheck(Instruction::BinaryOps BinaryOp,
4664 bool IsSigned, Value *LHS,
4665 Value *RHS, Instruction &OrigI,
4666 Value *&Result,
4667 Constant *&Overflow) {
4668 if (OrigI.isCommutative() && isa<Constant>(LHS) && !isa<Constant>(RHS))
4669 std::swap(LHS, RHS);
4670
4671 // If the overflow check was an add followed by a compare, the insertion point
4672 // may be pointing to the compare. We want to insert the new instructions
4673 // before the add in case there are uses of the add between the add and the
4674 // compare.
4675 Builder.SetInsertPoint(&OrigI);
4676
4677 Type *OverflowTy = Type::getInt1Ty(LHS->getContext());
4678 if (auto *LHSTy = dyn_cast<VectorType>(LHS->getType()))
4679 OverflowTy = VectorType::get(OverflowTy, LHSTy->getElementCount());
4680
4681 if (isNeutralValue(BinaryOp, RHS)) {
4682 Result = LHS;
4683 Overflow = ConstantInt::getFalse(OverflowTy);
4684 return true;
4685 }
4686
4687 switch (computeOverflow(BinaryOp, IsSigned, LHS, RHS, &OrigI)) {
4688 case OverflowResult::MayOverflow:
4689 return false;
4690 case OverflowResult::AlwaysOverflowsLow:
4691 case OverflowResult::AlwaysOverflowsHigh:
4692 Result = Builder.CreateBinOp(BinaryOp, LHS, RHS);
4693 Result->takeName(&OrigI);
4694 Overflow = ConstantInt::getTrue(OverflowTy);
4695 return true;
4696 case OverflowResult::NeverOverflows:
4697 Result = Builder.CreateBinOp(BinaryOp, LHS, RHS);
4698 Result->takeName(&OrigI);
4699 Overflow = ConstantInt::getFalse(OverflowTy);
4700 if (auto *Inst = dyn_cast<Instruction>(Result)) {
4701 if (IsSigned)
4702 Inst->setHasNoSignedWrap();
4703 else
4704 Inst->setHasNoUnsignedWrap();
4705 }
4706 return true;
4707 }
4708
4709 llvm_unreachable("Unexpected overflow result")__builtin_unreachable();
4710}
4711
4712/// Recognize and process idiom involving test for multiplication
4713/// overflow.
4714///
4715/// The caller has matched a pattern of the form:
4716/// I = cmp u (mul(zext A, zext B), V
4717/// The function checks if this is a test for overflow and if so replaces
4718/// multiplication with call to 'mul.with.overflow' intrinsic.
4719///
4720/// \param I Compare instruction.
4721/// \param MulVal Result of 'mult' instruction. It is one of the arguments of
4722/// the compare instruction. Must be of integer type.
4723/// \param OtherVal The other argument of compare instruction.
4724/// \returns Instruction which must replace the compare instruction, NULL if no
4725/// replacement required.
4726static Instruction *processUMulZExtIdiom(ICmpInst &I, Value *MulVal,
4727 Value *OtherVal,
4728 InstCombinerImpl &IC) {
4729 // Don't bother doing this transformation for pointers, don't do it for
4730 // vectors.
4731 if (!isa<IntegerType>(MulVal->getType()))
4732 return nullptr;
4733
4734 assert(I.getOperand(0) == MulVal || I.getOperand(1) == MulVal)((void)0);
4735 assert(I.getOperand(0) == OtherVal || I.getOperand(1) == OtherVal)((void)0);
4736 auto *MulInstr = dyn_cast<Instruction>(MulVal);
4737 if (!MulInstr)
4738 return nullptr;
4739 assert(MulInstr->getOpcode() == Instruction::Mul)((void)0);
4740
4741 auto *LHS = cast<ZExtOperator>(MulInstr->getOperand(0)),
4742 *RHS = cast<ZExtOperator>(MulInstr->getOperand(1));
4743 assert(LHS->getOpcode() == Instruction::ZExt)((void)0);
4744 assert(RHS->getOpcode() == Instruction::ZExt)((void)0);
4745 Value *A = LHS->getOperand(0), *B = RHS->getOperand(0);
4746
4747 // Calculate type and width of the result produced by mul.with.overflow.
4748 Type *TyA = A->getType(), *TyB = B->getType();
4749 unsigned WidthA = TyA->getPrimitiveSizeInBits(),
4750 WidthB = TyB->getPrimitiveSizeInBits();
4751 unsigned MulWidth;
4752 Type *MulType;
4753 if (WidthB > WidthA) {
4754 MulWidth = WidthB;
4755 MulType = TyB;
4756 } else {
4757 MulWidth = WidthA;
4758 MulType = TyA;
4759 }
4760
4761 // In order to replace the original mul with a narrower mul.with.overflow,
4762 // all uses must ignore upper bits of the product. The number of used low
4763 // bits must be not greater than the width of mul.with.overflow.
4764 if (MulVal->hasNUsesOrMore(2))
4765 for (User *U : MulVal->users()) {
4766 if (U == &I)
4767 continue;
4768 if (TruncInst *TI = dyn_cast<TruncInst>(U)) {
4769 // Check if truncation ignores bits above MulWidth.
4770 unsigned TruncWidth = TI->getType()->getPrimitiveSizeInBits();
4771 if (TruncWidth > MulWidth)
4772 return nullptr;
4773 } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U)) {
4774 // Check if AND ignores bits above MulWidth.
4775 if (BO->getOpcode() != Instruction::And)
4776 return nullptr;
4777 if (ConstantInt *CI = dyn_cast<ConstantInt>(BO->getOperand(1))) {
4778 const APInt &CVal = CI->getValue();
4779 if (CVal.getBitWidth() - CVal.countLeadingZeros() > MulWidth)
4780 return nullptr;
4781 } else {
4782 // In this case we could have the operand of the binary operation
4783 // being defined in another block, and performing the replacement
4784 // could break the dominance relation.
4785 return nullptr;
4786 }
4787 } else {
4788 // Other uses prohibit this transformation.
4789 return nullptr;
4790 }
4791 }
4792
4793 // Recognize patterns
4794 switch (I.getPredicate()) {
4795 case ICmpInst::ICMP_EQ:
4796 case ICmpInst::ICMP_NE:
4797 // Recognize pattern:
4798 // mulval = mul(zext A, zext B)
4799 // cmp eq/neq mulval, and(mulval, mask), mask selects low MulWidth bits.
4800 ConstantInt *CI;
4801 Value *ValToMask;
4802 if (match(OtherVal, m_And(m_Value(ValToMask), m_ConstantInt(CI)))) {
4803 if (ValToMask != MulVal)
4804 return nullptr;
4805 const APInt &CVal = CI->getValue() + 1;
4806 if (CVal.isPowerOf2()) {
4807 unsigned MaskWidth = CVal.logBase2();
4808 if (MaskWidth == MulWidth)
4809 break; // Recognized
4810 }
4811 }
4812 return nullptr;
4813
4814 case ICmpInst::ICMP_UGT:
4815 // Recognize pattern:
4816 // mulval = mul(zext A, zext B)
4817 // cmp ugt mulval, max
4818 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
4819 APInt MaxVal = APInt::getMaxValue(MulWidth);
4820 MaxVal = MaxVal.zext(CI->getBitWidth());
4821 if (MaxVal.eq(CI->getValue()))
4822 break; // Recognized
4823 }
4824 return nullptr;
4825
4826 case ICmpInst::ICMP_UGE:
4827 // Recognize pattern:
4828 // mulval = mul(zext A, zext B)
4829 // cmp uge mulval, max+1
4830 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
4831 APInt MaxVal = APInt::getOneBitSet(CI->getBitWidth(), MulWidth);
4832 if (MaxVal.eq(CI->getValue()))
4833 break; // Recognized
4834 }
4835 return nullptr;
4836
4837 case ICmpInst::ICMP_ULE:
4838 // Recognize pattern:
4839 // mulval = mul(zext A, zext B)
4840 // cmp ule mulval, max
4841 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
4842 APInt MaxVal = APInt::getMaxValue(MulWidth);
4843 MaxVal = MaxVal.zext(CI->getBitWidth());
4844 if (MaxVal.eq(CI->getValue()))
4845 break; // Recognized
4846 }
4847 return nullptr;
4848
4849 case ICmpInst::ICMP_ULT:
4850 // Recognize pattern:
4851 // mulval = mul(zext A, zext B)
4852 // cmp ule mulval, max + 1
4853 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
4854 APInt MaxVal = APInt::getOneBitSet(CI->getBitWidth(), MulWidth);
4855 if (MaxVal.eq(CI->getValue()))
4856 break; // Recognized
4857 }
4858 return nullptr;
4859
4860 default:
4861 return nullptr;
4862 }
4863
4864 InstCombiner::BuilderTy &Builder = IC.Builder;
4865 Builder.SetInsertPoint(MulInstr);
4866
4867 // Replace: mul(zext A, zext B) --> mul.with.overflow(A, B)
4868 Value *MulA = A, *MulB = B;
4869 if (WidthA < MulWidth)
4870 MulA = Builder.CreateZExt(A, MulType);
4871 if (WidthB < MulWidth)
4872 MulB = Builder.CreateZExt(B, MulType);
4873 Function *F = Intrinsic::getDeclaration(
4874 I.getModule(), Intrinsic::umul_with_overflow, MulType);
4875 CallInst *Call = Builder.CreateCall(F, {MulA, MulB}, "umul");
4876 IC.addToWorklist(MulInstr);
4877
4878 // If there are uses of mul result other than the comparison, we know that
4879 // they are truncation or binary AND. Change them to use result of
4880 // mul.with.overflow and adjust properly mask/size.
4881 if (MulVal->hasNUsesOrMore(2)) {
4882 Value *Mul = Builder.CreateExtractValue(Call, 0, "umul.value");
4883 for (User *U : make_early_inc_range(MulVal->users())) {
4884 if (U == &I || U == OtherVal)
4885 continue;
4886 if (TruncInst *TI = dyn_cast<TruncInst>(U)) {
4887 if (TI->getType()->getPrimitiveSizeInBits() == MulWidth)
4888 IC.replaceInstUsesWith(*TI, Mul);
4889 else
4890 TI->setOperand(0, Mul);
4891 } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U)) {
4892 assert(BO->getOpcode() == Instruction::And)((void)0);
4893 // Replace (mul & mask) --> zext (mul.with.overflow & short_mask)
4894 ConstantInt *CI = cast<ConstantInt>(BO->getOperand(1));
4895 APInt ShortMask = CI->getValue().trunc(MulWidth);
4896 Value *ShortAnd = Builder.CreateAnd(Mul, ShortMask);
4897 Value *Zext = Builder.CreateZExt(ShortAnd, BO->getType());
4898 IC.replaceInstUsesWith(*BO, Zext);
4899 } else {
4900 llvm_unreachable("Unexpected Binary operation")__builtin_unreachable();
4901 }
4902 IC.addToWorklist(cast<Instruction>(U));
4903 }
4904 }
4905 if (isa<Instruction>(OtherVal))
4906 IC.addToWorklist(cast<Instruction>(OtherVal));
4907
4908 // The original icmp gets replaced with the overflow value, maybe inverted
4909 // depending on predicate.
4910 bool Inverse = false;
4911 switch (I.getPredicate()) {
4912 case ICmpInst::ICMP_NE:
4913 break;
4914 case ICmpInst::ICMP_EQ:
4915 Inverse = true;
4916 break;
4917 case ICmpInst::ICMP_UGT:
4918 case ICmpInst::ICMP_UGE:
4919 if (I.getOperand(0) == MulVal)
4920 break;
4921 Inverse = true;
4922 break;
4923 case ICmpInst::ICMP_ULT:
4924 case ICmpInst::ICMP_ULE:
4925 if (I.getOperand(1) == MulVal)
4926 break;
4927 Inverse = true;
4928 break;
4929 default:
4930 llvm_unreachable("Unexpected predicate")__builtin_unreachable();
4931 }
4932 if (Inverse) {
4933 Value *Res = Builder.CreateExtractValue(Call, 1);
4934 return BinaryOperator::CreateNot(Res);
4935 }
4936
4937 return ExtractValueInst::Create(Call, 1);
4938}
4939
4940/// When performing a comparison against a constant, it is possible that not all
4941/// the bits in the LHS are demanded. This helper method computes the mask that
4942/// IS demanded.
4943static APInt getDemandedBitsLHSMask(ICmpInst &I, unsigned BitWidth) {
4944 const APInt *RHS;
4945 if (!match(I.getOperand(1), m_APInt(RHS)))
4946 return APInt::getAllOnesValue(BitWidth);
4947
4948 // If this is a normal comparison, it demands all bits. If it is a sign bit
4949 // comparison, it only demands the sign bit.
4950 bool UnusedBit;
4951 if (InstCombiner::isSignBitCheck(I.getPredicate(), *RHS, UnusedBit))
4952 return APInt::getSignMask(BitWidth);
4953
4954 switch (I.getPredicate()) {
4955 // For a UGT comparison, we don't care about any bits that
4956 // correspond to the trailing ones of the comparand. The value of these
4957 // bits doesn't impact the outcome of the comparison, because any value
4958 // greater than the RHS must differ in a bit higher than these due to carry.
4959 case ICmpInst::ICMP_UGT:
4960 return APInt::getBitsSetFrom(BitWidth, RHS->countTrailingOnes());
4961
4962 // Similarly, for a ULT comparison, we don't care about the trailing zeros.
4963 // Any value less than the RHS must differ in a higher bit because of carries.
4964 case ICmpInst::ICMP_ULT:
4965 return APInt::getBitsSetFrom(BitWidth, RHS->countTrailingZeros());
4966
4967 default:
4968 return APInt::getAllOnesValue(BitWidth);
4969 }
4970}
4971
4972/// Check if the order of \p Op0 and \p Op1 as operands in an ICmpInst
4973/// should be swapped.
4974/// The decision is based on how many times these two operands are reused
4975/// as subtract operands and their positions in those instructions.
4976/// The rationale is that several architectures use the same instruction for
4977/// both subtract and cmp. Thus, it is better if the order of those operands
4978/// match.
4979/// \return true if Op0 and Op1 should be swapped.
4980static bool swapMayExposeCSEOpportunities(const Value *Op0, const Value *Op1) {
4981 // Filter out pointer values as those cannot appear directly in subtract.
4982 // FIXME: we may want to go through inttoptrs or bitcasts.
4983 if (Op0->getType()->isPointerTy())
4984 return false;
4985 // If a subtract already has the same operands as a compare, swapping would be
4986 // bad. If a subtract has the same operands as a compare but in reverse order,
4987 // then swapping is good.
4988 int GoodToSwap = 0;
4989 for (const User *U : Op0->users()) {
4990 if (match(U, m_Sub(m_Specific(Op1), m_Specific(Op0))))
4991 GoodToSwap++;
4992 else if (match(U, m_Sub(m_Specific(Op0), m_Specific(Op1))))
4993 GoodToSwap--;
4994 }
4995 return GoodToSwap > 0;
4996}
4997
4998/// Check that one use is in the same block as the definition and all
4999/// other uses are in blocks dominated by a given block.
5000///
5001/// \param DI Definition
5002/// \param UI Use
5003/// \param DB Block that must dominate all uses of \p DI outside
5004/// the parent block
5005/// \return true when \p UI is the only use of \p DI in the parent block
5006/// and all other uses of \p DI are in blocks dominated by \p DB.
5007///
5008bool InstCombinerImpl::dominatesAllUses(const Instruction *DI,
5009 const Instruction *UI,
5010 const BasicBlock *DB) const {
5011 assert(DI && UI && "Instruction not defined\n")((void)0);
5012 // Ignore incomplete definitions.
5013 if (!DI->getParent())
5014 return false;
5015 // DI and UI must be in the same block.
5016 if (DI->getParent() != UI->getParent())
5017 return false;
5018 // Protect from self-referencing blocks.
5019 if (DI->getParent() == DB)
5020 return false;
5021 for (const User *U : DI->users()) {
5022 auto *Usr = cast<Instruction>(U);
5023 if (Usr != UI && !DT.dominates(DB, Usr->getParent()))
5024 return false;
5025 }
5026 return true;
5027}
5028
5029/// Return true when the instruction sequence within a block is select-cmp-br.
5030static bool isChainSelectCmpBranch(const SelectInst *SI) {
5031 const BasicBlock *BB = SI->getParent();
5032 if (!BB)
5033 return false;
5034 auto *BI = dyn_cast_or_null<BranchInst>(BB->getTerminator());
5035 if (!BI || BI->getNumSuccessors() != 2)
5036 return false;
5037 auto *IC = dyn_cast<ICmpInst>(BI->getCondition());
5038 if (!IC || (IC->getOperand(0) != SI && IC->getOperand(1) != SI))
5039 return false;
5040 return true;
5041}
5042
5043/// True when a select result is replaced by one of its operands
5044/// in select-icmp sequence. This will eventually result in the elimination
5045/// of the select.
5046///
5047/// \param SI Select instruction
5048/// \param Icmp Compare instruction
5049/// \param SIOpd Operand that replaces the select
5050///
5051/// Notes:
5052/// - The replacement is global and requires dominator information
5053/// - The caller is responsible for the actual replacement
5054///
5055/// Example:
5056///
5057/// entry:
5058/// %4 = select i1 %3, %C* %0, %C* null
5059/// %5 = icmp eq %C* %4, null
5060/// br i1 %5, label %9, label %7
5061/// ...
5062/// ; <label>:7 ; preds = %entry
5063/// %8 = getelementptr inbounds %C* %4, i64 0, i32 0
5064/// ...
5065///
5066/// can be transformed to
5067///
5068/// %5 = icmp eq %C* %0, null
5069/// %6 = select i1 %3, i1 %5, i1 true
5070/// br i1 %6, label %9, label %7
5071/// ...
5072/// ; <label>:7 ; preds = %entry
5073/// %8 = getelementptr inbounds %C* %0, i64 0, i32 0 // replace by %0!
5074///
5075/// Similar when the first operand of the select is a constant or/and
5076/// the compare is for not equal rather than equal.
5077///
5078/// NOTE: The function is only called when the select and compare constants
5079/// are equal, the optimization can work only for EQ predicates. This is not a
5080/// major restriction since a NE compare should be 'normalized' to an equal
5081/// compare, which usually happens in the combiner and test case
5082/// select-cmp-br.ll checks for it.
5083bool InstCombinerImpl::replacedSelectWithOperand(SelectInst *SI,
5084 const ICmpInst *Icmp,
5085 const unsigned SIOpd) {
5086 assert((SIOpd == 1 || SIOpd == 2) && "Invalid select operand!")((void)0);
5087 if (isChainSelectCmpBranch(SI) && Icmp->getPredicate() == ICmpInst::ICMP_EQ) {
5088 BasicBlock *Succ = SI->getParent()->getTerminator()->getSuccessor(1);
5089 // The check for the single predecessor is not the best that can be
5090 // done. But it protects efficiently against cases like when SI's
5091 // home block has two successors, Succ and Succ1, and Succ1 predecessor
5092 // of Succ. Then SI can't be replaced by SIOpd because the use that gets
5093 // replaced can be reached on either path. So the uniqueness check
5094 // guarantees that the path all uses of SI (outside SI's parent) are on
5095 // is disjoint from all other paths out of SI. But that information
5096 // is more expensive to compute, and the trade-off here is in favor
5097 // of compile-time. It should also be noticed that we check for a single
5098 // predecessor and not only uniqueness. This to handle the situation when
5099 // Succ and Succ1 points to the same basic block.
5100 if (Succ->getSinglePredecessor() && dominatesAllUses(SI, Icmp, Succ)) {
5101 NumSel++;
5102 SI->replaceUsesOutsideBlock(SI->getOperand(SIOpd), SI->getParent());
5103 return true;
5104 }
5105 }
5106 return false;
5107}
5108
5109/// Try to fold the comparison based on range information we can get by checking
5110/// whether bits are known to be zero or one in the inputs.
5111Instruction *InstCombinerImpl::foldICmpUsingKnownBits(ICmpInst &I) {
5112 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
5113 Type *Ty = Op0->getType();
5114 ICmpInst::Predicate Pred = I.getPredicate();
5115
5116 // Get scalar or pointer size.
5117 unsigned BitWidth = Ty->isIntOrIntVectorTy()
5118 ? Ty->getScalarSizeInBits()
5119 : DL.getPointerTypeSizeInBits(Ty->getScalarType());
5120
5121 if (!BitWidth)
5122 return nullptr;
5123
5124 KnownBits Op0Known(BitWidth);
5125 KnownBits Op1Known(BitWidth);
5126
5127 if (SimplifyDemandedBits(&I, 0,
5128 getDemandedBitsLHSMask(I, BitWidth),
5129 Op0Known, 0))
5130 return &I;
5131
5132 if (SimplifyDemandedBits(&I, 1, APInt::getAllOnesValue(BitWidth),
5133 Op1Known, 0))
5134 return &I;
5135
5136 // Given the known and unknown bits, compute a range that the LHS could be
5137 // in. Compute the Min, Max and RHS values based on the known bits. For the
5138 // EQ and NE we use unsigned values.
5139 APInt Op0Min(BitWidth, 0), Op0Max(BitWidth, 0);
5140 APInt Op1Min(BitWidth, 0), Op1Max(BitWidth, 0);
5141 if (I.isSigned()) {
5142 Op0Min = Op0Known.getSignedMinValue();
5143 Op0Max = Op0Known.getSignedMaxValue();
5144 Op1Min = Op1Known.getSignedMinValue();
5145 Op1Max = Op1Known.getSignedMaxValue();
5146 } else {
5147 Op0Min = Op0Known.getMinValue();
5148 Op0Max = Op0Known.getMaxValue();
5149 Op1Min = Op1Known.getMinValue();
5150 Op1Max = Op1Known.getMaxValue();
5151 }
5152
5153 // If Min and Max are known to be the same, then SimplifyDemandedBits figured
5154 // out that the LHS or RHS is a constant. Constant fold this now, so that
5155 // code below can assume that Min != Max.
5156 if (!isa<Constant>(Op0) && Op0Min == Op0Max)
5157 return new ICmpInst(Pred, ConstantExpr::getIntegerValue(Ty, Op0Min), Op1);
5158 if (!isa<Constant>(Op1) && Op1Min == Op1Max)
5159 return new ICmpInst(Pred, Op0, ConstantExpr::getIntegerValue(Ty, Op1Min));
5160
5161 // Don't break up a clamp pattern -- (min(max X, Y), Z) -- by replacing a
5162 // min/max canonical compare with some other compare. That could lead to
5163 // conflict with select canonicalization and infinite looping.
5164 // FIXME: This constraint may go away if min/max intrinsics are canonical.
5165 auto isMinMaxCmp = [&](Instruction &Cmp) {
5166 if (!Cmp.hasOneUse())
5167 return false;
5168 Value *A, *B;
5169 SelectPatternFlavor SPF = matchSelectPattern(Cmp.user_back(), A, B).Flavor;
5170 if (!SelectPatternResult::isMinOrMax(SPF))
5171 return false;
5172 return match(Op0, m_MaxOrMin(m_Value(), m_Value())) ||
5173 match(Op1, m_MaxOrMin(m_Value(), m_Value()));
5174 };
5175 if (!isMinMaxCmp(I)) {
5176 switch (Pred) {
5177 default:
5178 break;
5179 case ICmpInst::ICMP_ULT: {
5180 if (Op1Min == Op0Max) // A <u B -> A != B if max(A) == min(B)
5181 return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
5182 const APInt *CmpC;
5183 if (match(Op1, m_APInt(CmpC))) {
5184 // A <u C -> A == C-1 if min(A)+1 == C
5185 if (*CmpC == Op0Min + 1)
5186 return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
5187 ConstantInt::get(Op1->getType(), *CmpC - 1));
5188 // X <u C --> X == 0, if the number of zero bits in the bottom of X
5189 // exceeds the log2 of C.
5190 if (Op0Known.countMinTrailingZeros() >= CmpC->ceilLogBase2())
5191 return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
5192 Constant::getNullValue(Op1->getType()));
5193 }
5194 break;
5195 }
5196 case ICmpInst::ICMP_UGT: {
5197 if (Op1Max == Op0Min) // A >u B -> A != B if min(A) == max(B)
5198 return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
5199 const APInt *CmpC;
5200 if (match(Op1, m_APInt(CmpC))) {
5201 // A >u C -> A == C+1 if max(a)-1 == C
5202 if (*CmpC == Op0Max - 1)
5203 return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
5204 ConstantInt::get(Op1->getType(), *CmpC + 1));
5205 // X >u C --> X != 0, if the number of zero bits in the bottom of X
5206 // exceeds the log2 of C.
5207 if (Op0Known.countMinTrailingZeros() >= CmpC->getActiveBits())
5208 return new ICmpInst(ICmpInst::ICMP_NE, Op0,
5209 Constant::getNullValue(Op1->getType()));
5210 }
5211 break;
5212 }
5213 case ICmpInst::ICMP_SLT: {
5214 if (Op1Min == Op0Max) // A <s B -> A != B if max(A) == min(B)
5215 return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
5216 const APInt *CmpC;
5217 if (match(Op1, m_APInt(CmpC))) {
5218 if (*CmpC == Op0Min + 1) // A <s C -> A == C-1 if min(A)+1 == C
5219 return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
5220 ConstantInt::get(Op1->getType(), *CmpC - 1));
5221 }
5222 break;
5223 }
5224 case ICmpInst::ICMP_SGT: {
5225 if (Op1Max == Op0Min) // A >s B -> A != B if min(A) == max(B)
5226 return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
5227 const APInt *CmpC;
5228 if (match(Op1, m_APInt(CmpC))) {
5229 if (*CmpC == Op0Max - 1) // A >s C -> A == C+1 if max(A)-1 == C
5230 return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
5231 ConstantInt::get(Op1->getType(), *CmpC + 1));
5232 }
5233 break;
5234 }
5235 }
5236 }
5237
5238 // Based on the range information we know about the LHS, see if we can
5239 // simplify this comparison. For example, (x&4) < 8 is always true.
5240 switch (Pred) {
5241 default:
5242 llvm_unreachable("Unknown icmp opcode!")__builtin_unreachable();
5243 case ICmpInst::ICMP_EQ:
5244 case ICmpInst::ICMP_NE: {
5245 if (Op0Max.ult(Op1Min) || Op0Min.ugt(Op1Max))
5246 return replaceInstUsesWith(
5247 I, ConstantInt::getBool(I.getType(), Pred == CmpInst::ICMP_NE));
5248
5249 // If all bits are known zero except for one, then we know at most one bit
5250 // is set. If the comparison is against zero, then this is a check to see if
5251 // *that* bit is set.
5252 APInt Op0KnownZeroInverted = ~Op0Known.Zero;
5253 if (Op1Known.isZero()) {
5254 // If the LHS is an AND with the same constant, look through it.
5255 Value *LHS = nullptr;
5256 const APInt *LHSC;
5257 if (!match(Op0, m_And(m_Value(LHS), m_APInt(LHSC))) ||
5258 *LHSC != Op0KnownZeroInverted)
5259 LHS = Op0;
5260
5261 Value *X;
5262 if (match(LHS, m_Shl(m_One(), m_Value(X)))) {
5263 APInt ValToCheck = Op0KnownZeroInverted;
5264 Type *XTy = X->getType();
5265 if (ValToCheck.isPowerOf2()) {
5266 // ((1 << X) & 8) == 0 -> X != 3
5267 // ((1 << X) & 8) != 0 -> X == 3
5268 auto *CmpC = ConstantInt::get(XTy, ValToCheck.countTrailingZeros());
5269 auto NewPred = ICmpInst::getInversePredicate(Pred);
5270 return new ICmpInst(NewPred, X, CmpC);
5271 } else if ((++ValToCheck).isPowerOf2()) {
5272 // ((1 << X) & 7) == 0 -> X >= 3
5273 // ((1 << X) & 7) != 0 -> X < 3
5274 auto *CmpC = ConstantInt::get(XTy, ValToCheck.countTrailingZeros());
5275 auto NewPred =
5276 Pred == CmpInst::ICMP_EQ ? CmpInst::ICMP_UGE : CmpInst::ICMP_ULT;
5277 return new ICmpInst(NewPred, X, CmpC);
5278 }
5279 }
5280
5281 // Check if the LHS is 8 >>u x and the result is a power of 2 like 1.
5282 const APInt *CI;
5283 if (Op0KnownZeroInverted.isOneValue() &&
5284 match(LHS, m_LShr(m_Power2(CI), m_Value(X)))) {
5285 // ((8 >>u X) & 1) == 0 -> X != 3
5286 // ((8 >>u X) & 1) != 0 -> X == 3
5287 unsigned CmpVal = CI->countTrailingZeros();
5288 auto NewPred = ICmpInst::getInversePredicate(Pred);
5289 return new ICmpInst(NewPred, X, ConstantInt::get(X->getType(), CmpVal));
5290 }
5291 }
5292 break;
5293 }
5294 case ICmpInst::ICMP_ULT: {
5295 if (Op0Max.ult(Op1Min)) // A <u B -> true if max(A) < min(B)
5296 return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
5297 if (Op0Min.uge(Op1Max)) // A <u B -> false if min(A) >= max(B)
5298 return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
5299 break;
5300 }
5301 case ICmpInst::ICMP_UGT: {
5302 if (Op0Min.ugt(Op1Max)) // A >u B -> true if min(A) > max(B)
5303 return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
5304 if (Op0Max.ule(Op1Min)) // A >u B -> false if max(A) <= max(B)
5305 return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
5306 break;
5307 }
5308 case ICmpInst::ICMP_SLT: {
5309 if (Op0Max.slt(Op1Min)) // A <s B -> true if max(A) < min(C)
5310 return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
5311 if (Op0Min.sge(Op1Max)) // A <s B -> false if min(A) >= max(C)
5312 return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
5313 break;
5314 }
5315 case ICmpInst::ICMP_SGT: {
5316 if (Op0Min.sgt(Op1Max)) // A >s B -> true if min(A) > max(B)
5317 return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
5318 if (Op0Max.sle(Op1Min)) // A >s B -> false if max(A) <= min(B)
5319 return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
5320 break;
5321 }
5322 case ICmpInst::ICMP_SGE:
5323 assert(!isa<ConstantInt>(Op1) && "ICMP_SGE with ConstantInt not folded!")((void)0);
5324 if (Op0Min.sge(Op1Max)) // A >=s B -> true if min(A) >= max(B)
5325 return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
5326 if (Op0Max.slt(Op1Min)) // A >=s B -> false if max(A) < min(B)
5327 return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
5328 if (Op1Min == Op0Max) // A >=s B -> A == B if max(A) == min(B)
5329 return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
5330 break;
5331 case ICmpInst::ICMP_SLE:
5332 assert(!isa<ConstantInt>(Op1) && "ICMP_SLE with ConstantInt not folded!")((void)0);
5333 if (Op0Max.sle(Op1Min)) // A <=s B -> true if max(A) <= min(B)
5334 return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
5335 if (Op0Min.sgt(Op1Max)) // A <=s B -> false if min(A) > max(B)
5336 return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
5337 if (Op1Max == Op0Min) // A <=s B -> A == B if min(A) == max(B)
5338 return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
5339 break;
5340 case ICmpInst::ICMP_UGE:
5341 assert(!isa<ConstantInt>(Op1) && "ICMP_UGE with ConstantInt not folded!")((void)0);
5342 if (Op0Min.uge(Op1Max)) // A >=u B -> true if min(A) >= max(B)
5343 return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
5344 if (Op0Max.ult(Op1Min)) // A >=u B -> false if max(A) < min(B)
5345 return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
5346 if (Op1Min == Op0Max) // A >=u B -> A == B if max(A) == min(B)
5347 return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
5348 break;
5349 case ICmpInst::ICMP_ULE:
5350 assert(!isa<ConstantInt>(Op1) && "ICMP_ULE with ConstantInt not folded!")((void)0);
5351 if (Op0Max.ule(Op1Min)) // A <=u B -> true if max(A) <= min(B)
5352 return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
5353 if (Op0Min.ugt(Op1Max)) // A <=u B -> false if min(A) > max(B)
5354 return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
5355 if (Op1Max == Op0Min) // A <=u B -> A == B if min(A) == max(B)
5356 return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
5357 break;
5358 }
5359
5360 // Turn a signed comparison into an unsigned one if both operands are known to
5361 // have the same sign.
5362 if (I.isSigned() &&
5363 ((Op0Known.Zero.isNegative() && Op1Known.Zero.isNegative()) ||
5364 (Op0Known.One.isNegative() && Op1Known.One.isNegative())))
5365 return new ICmpInst(I.getUnsignedPredicate(), Op0, Op1);
5366
5367 return nullptr;
5368}
5369
5370llvm::Optional<std::pair<CmpInst::Predicate, Constant *>>
5371InstCombiner::getFlippedStrictnessPredicateAndConstant(CmpInst::Predicate Pred,
5372 Constant *C) {
5373 assert(ICmpInst::isRelational(Pred) && ICmpInst::isIntPredicate(Pred) &&((void)0)
5374 "Only for relational integer predicates.")((void)0);
5375
5376 Type *Type = C->getType();
5377 bool IsSigned = ICmpInst::isSigned(Pred);
5378
5379 CmpInst::Predicate UnsignedPred = ICmpInst::getUnsignedPredicate(Pred);
5380 bool WillIncrement =
5381 UnsignedPred == ICmpInst::ICMP_ULE || UnsignedPred == ICmpInst::ICMP_UGT;
5382
5383 // Check if the constant operand can be safely incremented/decremented
5384 // without overflowing/underflowing.
5385 auto ConstantIsOk = [WillIncrement, IsSigned](ConstantInt *C) {
5386 return WillIncrement ? !C->isMaxValue(IsSigned) : !C->isMinValue(IsSigned);
5387 };
5388
5389 Constant *SafeReplacementConstant = nullptr;
5390 if (auto *CI = dyn_cast<ConstantInt>(C)) {
5391 // Bail out if the constant can't be safely incremented/decremented.
5392 if (!ConstantIsOk(CI))
5393 return llvm::None;
5394 } else if (auto *FVTy = dyn_cast<FixedVectorType>(Type)) {
5395 unsigned NumElts = FVTy->getNumElements();
5396 for (unsigned i = 0; i != NumElts; ++i) {
5397 Constant *Elt = C->getAggregateElement(i);
5398 if (!Elt)
5399 return llvm::None;
5400
5401 if (isa<UndefValue>(Elt))
5402 continue;
5403
5404 // Bail out if we can't determine if this constant is min/max or if we
5405 // know that this constant is min/max.
5406 auto *CI = dyn_cast<ConstantInt>(Elt);
5407 if (!CI || !ConstantIsOk(CI))
5408 return llvm::None;
5409
5410 if (!SafeReplacementConstant)
5411 SafeReplacementConstant = CI;
5412 }
5413 } else {
5414 // ConstantExpr?
5415 return llvm::None;
5416 }
5417
5418 // It may not be safe to change a compare predicate in the presence of
5419 // undefined elements, so replace those elements with the first safe constant
5420 // that we found.
5421 // TODO: in case of poison, it is safe; let's replace undefs only.
5422 if (C->containsUndefOrPoisonElement()) {
5423 assert(SafeReplacementConstant && "Replacement constant not set")((void)0);
5424 C = Constant::replaceUndefsWith(C, SafeReplacementConstant);
5425 }
5426
5427 CmpInst::Predicate NewPred = CmpInst::getFlippedStrictnessPredicate(Pred);
5428
5429 // Increment or decrement the constant.
5430 Constant *OneOrNegOne = ConstantInt::get(Type, WillIncrement ? 1 : -1, true);
5431 Constant *NewC = ConstantExpr::getAdd(C, OneOrNegOne);
5432
5433 return std::make_pair(NewPred, NewC);
5434}
5435
5436/// If we have an icmp le or icmp ge instruction with a constant operand, turn
5437/// it into the appropriate icmp lt or icmp gt instruction. This transform
5438/// allows them to be folded in visitICmpInst.
5439static ICmpInst *canonicalizeCmpWithConstant(ICmpInst &I) {
5440 ICmpInst::Predicate Pred = I.getPredicate();
5441 if (ICmpInst::isEquality(Pred) || !ICmpInst::isIntPredicate(Pred) ||
5442 InstCombiner::isCanonicalPredicate(Pred))
5443 return nullptr;
5444
5445 Value *Op0 = I.getOperand(0);
5446 Value *Op1 = I.getOperand(1);
5447 auto *Op1C = dyn_cast<Constant>(Op1);
5448 if (!Op1C)
5449 return nullptr;
5450
5451 auto FlippedStrictness =
5452 InstCombiner::getFlippedStrictnessPredicateAndConstant(Pred, Op1C);
5453 if (!FlippedStrictness)
5454 return nullptr;
5455
5456 return new ICmpInst(FlippedStrictness->first, Op0, FlippedStrictness->second);
5457}
5458
5459/// If we have a comparison with a non-canonical predicate, if we can update
5460/// all the users, invert the predicate and adjust all the users.
5461CmpInst *InstCombinerImpl::canonicalizeICmpPredicate(CmpInst &I) {
5462 // Is the predicate already canonical?
5463 CmpInst::Predicate Pred = I.getPredicate();
5464 if (InstCombiner::isCanonicalPredicate(Pred))
5465 return nullptr;
5466
5467 // Can all users be adjusted to predicate inversion?
5468 if (!InstCombiner::canFreelyInvertAllUsersOf(&I, /*IgnoredUser=*/nullptr))
5469 return nullptr;
5470
5471 // Ok, we can canonicalize comparison!
5472 // Let's first invert the comparison's predicate.
5473 I.setPredicate(CmpInst::getInversePredicate(Pred));
5474 I.setName(I.getName() + ".not");
5475
5476 // And, adapt users.
5477 freelyInvertAllUsersOf(&I);
5478
5479 return &I;
5480}
5481
5482/// Integer compare with boolean values can always be turned into bitwise ops.
5483static Instruction *canonicalizeICmpBool(ICmpInst &I,
5484 InstCombiner::BuilderTy &Builder) {
5485 Value *A = I.getOperand(0), *B = I.getOperand(1);
5486 assert(A->getType()->isIntOrIntVectorTy(1) && "Bools only")((void)0);
5487
5488 // A boolean compared to true/false can be simplified to Op0/true/false in
5489 // 14 out of the 20 (10 predicates * 2 constants) possible combinations.
5490 // Cases not handled by InstSimplify are always 'not' of Op0.
5491 if (match(B, m_Zero())) {
5492 switch (I.getPredicate()) {
5493 case CmpInst::ICMP_EQ: // A == 0 -> !A
5494 case CmpInst::ICMP_ULE: // A <=u 0 -> !A
5495 case CmpInst::ICMP_SGE: // A >=s 0 -> !A
5496 return BinaryOperator::CreateNot(A);
5497 default:
5498 llvm_unreachable("ICmp i1 X, C not simplified as expected.")__builtin_unreachable();
5499 }
5500 } else if (match(B, m_One())) {
5501 switch (I.getPredicate()) {
5502 case CmpInst::ICMP_NE: // A != 1 -> !A
5503 case CmpInst::ICMP_ULT: // A <u 1 -> !A
5504 case CmpInst::ICMP_SGT: // A >s -1 -> !A
5505 return BinaryOperator::CreateNot(A);
5506 default:
5507 llvm_unreachable("ICmp i1 X, C not simplified as expected.")__builtin_unreachable();
5508 }
5509 }
5510
5511 switch (I.getPredicate()) {
5512 default:
5513 llvm_unreachable("Invalid icmp instruction!")__builtin_unreachable();
5514 case ICmpInst::ICMP_EQ:
5515 // icmp eq i1 A, B -> ~(A ^ B)
5516 return BinaryOperator::CreateNot(Builder.CreateXor(A, B));
5517
5518 case ICmpInst::ICMP_NE:
5519 // icmp ne i1 A, B -> A ^ B
5520 return BinaryOperator::CreateXor(A, B);
5521
5522 case ICmpInst::ICMP_UGT:
5523 // icmp ugt -> icmp ult
5524 std::swap(A, B);
5525 LLVM_FALLTHROUGH[[gnu::fallthrough]];
5526 case ICmpInst::ICMP_ULT:
5527 // icmp ult i1 A, B -> ~A & B
5528 return BinaryOperator::CreateAnd(Builder.CreateNot(A), B);
5529
5530 case ICmpInst::ICMP_SGT:
5531 // icmp sgt -> icmp slt
5532 std::swap(A, B);
5533 LLVM_FALLTHROUGH[[gnu::fallthrough]];
5534 case ICmpInst::ICMP_SLT:
5535 // icmp slt i1 A, B -> A & ~B
5536 return BinaryOperator::CreateAnd(Builder.CreateNot(B), A);
5537
5538 case ICmpInst::ICMP_UGE:
5539 // icmp uge -> icmp ule
5540 std::swap(A, B);
5541 LLVM_FALLTHROUGH[[gnu::fallthrough]];
5542 case ICmpInst::ICMP_ULE:
5543 // icmp ule i1 A, B -> ~A | B
5544 return BinaryOperator::CreateOr(Builder.CreateNot(A), B);
5545
5546 case ICmpInst::ICMP_SGE:
5547 // icmp sge -> icmp sle
5548 std::swap(A, B);
5549 LLVM_FALLTHROUGH[[gnu::fallthrough]];
5550 case ICmpInst::ICMP_SLE:
5551 // icmp sle i1 A, B -> A | ~B
5552 return BinaryOperator::CreateOr(Builder.CreateNot(B), A);
5553 }
5554}
5555
5556// Transform pattern like:
5557// (1 << Y) u<= X or ~(-1 << Y) u< X or ((1 << Y)+(-1)) u< X
5558// (1 << Y) u> X or ~(-1 << Y) u>= X or ((1 << Y)+(-1)) u>= X
5559// Into:
5560// (X l>> Y) != 0
5561// (X l>> Y) == 0
5562static Instruction *foldICmpWithHighBitMask(ICmpInst &Cmp,
5563 InstCombiner::BuilderTy &Builder) {
5564 ICmpInst::Predicate Pred, NewPred;
5565 Value *X, *Y;
5566 if (match(&Cmp,
5567 m_c_ICmp(Pred, m_OneUse(m_Shl(m_One(), m_Value(Y))), m_Value(X)))) {
5568 switch (Pred) {
5569 case ICmpInst::ICMP_ULE:
5570 NewPred = ICmpInst::ICMP_NE;
5571 break;
5572 case ICmpInst::ICMP_UGT:
5573 NewPred = ICmpInst::ICMP_EQ;
5574 break;
5575 default:
5576 return nullptr;
5577 }
5578 } else if (match(&Cmp, m_c_ICmp(Pred,
5579 m_OneUse(m_CombineOr(
5580 m_Not(m_Shl(m_AllOnes(), m_Value(Y))),
5581 m_Add(m_Shl(m_One(), m_Value(Y)),
5582 m_AllOnes()))),
5583 m_Value(X)))) {
5584 // The variant with 'add' is not canonical, (the variant with 'not' is)
5585 // we only get it because it has extra uses, and can't be canonicalized,
5586
5587 switch (Pred) {
5588 case ICmpInst::ICMP_ULT:
5589 NewPred = ICmpInst::ICMP_NE;
5590 break;
5591 case ICmpInst::ICMP_UGE:
5592 NewPred = ICmpInst::ICMP_EQ;
5593 break;
5594 default:
5595 return nullptr;
5596 }
5597 } else
5598 return nullptr;
5599
5600 Value *NewX = Builder.CreateLShr(X, Y, X->getName() + ".highbits");
5601 Constant *Zero = Constant::getNullValue(NewX->getType());
5602 return CmpInst::Create(Instruction::ICmp, NewPred, NewX, Zero);
5603}
5604
5605static Instruction *foldVectorCmp(CmpInst &Cmp,
5606 InstCombiner::BuilderTy &Builder) {
5607 const CmpInst::Predicate Pred = Cmp.getPredicate();
5608 Value *LHS = Cmp.getOperand(0), *RHS = Cmp.getOperand(1);
5609 Value *V1, *V2;
5610 ArrayRef<int> M;
5611 if (!match(LHS, m_Shuffle(m_Value(V1), m_Undef(), m_Mask(M))))
5612 return nullptr;
5613
5614 // If both arguments of the cmp are shuffles that use the same mask and
5615 // shuffle within a single vector, move the shuffle after the cmp:
5616 // cmp (shuffle V1, M), (shuffle V2, M) --> shuffle (cmp V1, V2), M
5617 Type *V1Ty = V1->getType();
5618 if (match(RHS, m_Shuffle(m_Value(V2), m_Undef(), m_SpecificMask(M))) &&
5619 V1Ty == V2->getType() && (LHS->hasOneUse() || RHS->hasOneUse())) {
5620 Value *NewCmp = Builder.CreateCmp(Pred, V1, V2);
5621 return new ShuffleVectorInst(NewCmp, UndefValue::get(NewCmp->getType()), M);
5622 }
5623
5624 // Try to canonicalize compare with splatted operand and splat constant.
5625 // TODO: We could generalize this for more than splats. See/use the code in
5626 // InstCombiner::foldVectorBinop().
5627 Constant *C;
5628 if (!LHS->hasOneUse() || !match(RHS, m_Constant(C)))
5629 return nullptr;
5630
5631 // Length-changing splats are ok, so adjust the constants as needed:
5632 // cmp (shuffle V1, M), C --> shuffle (cmp V1, C'), M
5633 Constant *ScalarC = C->getSplatValue(/* AllowUndefs */ true);
5634 int MaskSplatIndex;
5635 if (ScalarC && match(M, m_SplatOrUndefMask(MaskSplatIndex))) {
5636 // We allow undefs in matching, but this transform removes those for safety.
5637 // Demanded elements analysis should be able to recover some/all of that.
5638 C = ConstantVector::getSplat(cast<VectorType>(V1Ty)->getElementCount(),
5639 ScalarC);
5640 SmallVector<int, 8> NewM(M.size(), MaskSplatIndex);
5641 Value *NewCmp = Builder.CreateCmp(Pred, V1, C);
5642 return new ShuffleVectorInst(NewCmp, UndefValue::get(NewCmp->getType()),
5643 NewM);
5644 }
5645
5646 return nullptr;
5647}
5648
5649// extract(uadd.with.overflow(A, B), 0) ult A
5650// -> extract(uadd.with.overflow(A, B), 1)
5651static Instruction *foldICmpOfUAddOv(ICmpInst &I) {
5652 CmpInst::Predicate Pred = I.getPredicate();
5653 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
5654
5655 Value *UAddOv;
5656 Value *A, *B;
5657 auto UAddOvResultPat = m_ExtractValue<0>(
5658 m_Intrinsic<Intrinsic::uadd_with_overflow>(m_Value(A), m_Value(B)));
5659 if (match(Op0, UAddOvResultPat) &&
5660 ((Pred == ICmpInst::ICMP_ULT && (Op1 == A || Op1 == B)) ||
5661 (Pred == ICmpInst::ICMP_EQ && match(Op1, m_ZeroInt()) &&
5662 (match(A, m_One()) || match(B, m_One()))) ||
5663 (Pred == ICmpInst::ICMP_NE && match(Op1, m_AllOnes()) &&
5664 (match(A, m_AllOnes()) || match(B, m_AllOnes())))))
5665 // extract(uadd.with.overflow(A, B), 0) < A
5666 // extract(uadd.with.overflow(A, 1), 0) == 0
5667 // extract(uadd.with.overflow(A, -1), 0) != -1
5668 UAddOv = cast<ExtractValueInst>(Op0)->getAggregateOperand();
5669 else if (match(Op1, UAddOvResultPat) &&
5670 Pred == ICmpInst::ICMP_UGT && (Op0 == A || Op0 == B))
5671 // A > extract(uadd.with.overflow(A, B), 0)
5672 UAddOv = cast<ExtractValueInst>(Op1)->getAggregateOperand();
5673 else
5674 return nullptr;
5675
5676 return ExtractValueInst::Create(UAddOv, 1);
5677}
5678
5679Instruction *InstCombinerImpl::visitICmpInst(ICmpInst &I) {
5680 bool Changed = false;
5681 const SimplifyQuery Q = SQ.getWithInstruction(&I);
5682 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
5683 unsigned Op0Cplxity = getComplexity(Op0);
5684 unsigned Op1Cplxity = getComplexity(Op1);
5685
5686 /// Orders the operands of the compare so that they are listed from most
5687 /// complex to least complex. This puts constants before unary operators,
5688 /// before binary operators.
5689 if (Op0Cplxity < Op1Cplxity ||
5690 (Op0Cplxity == Op1Cplxity && swapMayExposeCSEOpportunities(Op0, Op1))) {
5691 I.swapOperands();
5692 std::swap(Op0, Op1);
5693 Changed = true;
5694 }
5695
5696 if (Value *V = SimplifyICmpInst(I.getPredicate(), Op0, Op1, Q))
5697 return replaceInstUsesWith(I, V);
5698
5699 // Comparing -val or val with non-zero is the same as just comparing val
5700 // ie, abs(val) != 0 -> val != 0
5701 if (I.getPredicate() == ICmpInst::ICMP_NE && match(Op1, m_Zero())) {
5702 Value *Cond, *SelectTrue, *SelectFalse;
5703 if (match(Op0, m_Select(m_Value(Cond), m_Value(SelectTrue),
5704 m_Value(SelectFalse)))) {
5705 if (Value *V = dyn_castNegVal(SelectTrue)) {
5706 if (V == SelectFalse)
5707 return CmpInst::Create(Instruction::ICmp, I.getPredicate(), V, Op1);
5708 }
5709 else if (Value *V = dyn_castNegVal(SelectFalse)) {
5710 if (V == SelectTrue)
5711 return CmpInst::Create(Instruction::ICmp, I.getPredicate(), V, Op1);
5712 }