Bug Summary

File:src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/lib/CodeGen/RegisterClassInfo.cpp
Warning:line 94, column 26
Called C++ object pointer is null

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 RegisterClassInfo.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 pic -pic-level 1 -fhalf-no-semantic-interposition -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" -D PIC -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 -D_RET_PROTECTOR -ret-protector -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/CodeGen/RegisterClassInfo.cpp
1//===- RegisterClassInfo.cpp - Dynamic Register Class Info ----------------===//
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 RegisterClassInfo class which provides dynamic
10// information about target register classes. Callee-saved vs. caller-saved and
11// reserved registers depend on calling conventions and other dynamic
12// information, so some things cannot be determined statically.
13//
14//===----------------------------------------------------------------------===//
15
16#include "llvm/CodeGen/RegisterClassInfo.h"
17#include "llvm/ADT/ArrayRef.h"
18#include "llvm/ADT/BitVector.h"
19#include "llvm/ADT/SmallVector.h"
20#include "llvm/CodeGen/MachineFunction.h"
21#include "llvm/CodeGen/MachineRegisterInfo.h"
22#include "llvm/CodeGen/TargetFrameLowering.h"
23#include "llvm/CodeGen/TargetRegisterInfo.h"
24#include "llvm/CodeGen/TargetSubtargetInfo.h"
25#include "llvm/MC/MCRegisterInfo.h"
26#include "llvm/Support/CommandLine.h"
27#include "llvm/Support/Debug.h"
28#include "llvm/Support/raw_ostream.h"
29#include <algorithm>
30#include <cassert>
31#include <cstdint>
32
33using namespace llvm;
34
35#define DEBUG_TYPE"regalloc" "regalloc"
36
37static cl::opt<unsigned>
38StressRA("stress-regalloc", cl::Hidden, cl::init(0), cl::value_desc("N"),
39 cl::desc("Limit all regclasses to N registers"));
40
41RegisterClassInfo::RegisterClassInfo() = default;
42
43void RegisterClassInfo::runOnMachineFunction(const MachineFunction &mf) {
44 bool Update = false;
45 MF = &mf;
46
47 // Allocate new array the first time we see a new target.
48 if (MF->getSubtarget().getRegisterInfo() != TRI) {
49 TRI = MF->getSubtarget().getRegisterInfo();
50 RegClass.reset(new RCInfo[TRI->getNumRegClasses()]);
51 Update = true;
52 }
53
54 // Does this MF have different CSRs?
55 assert(TRI && "no register info set")((void)0);
56
57 // Get the callee saved registers.
58 const MCPhysReg *CSR = MF->getRegInfo().getCalleeSavedRegs();
59 if (Update || CSR != CalleeSavedRegs) {
60 // Build a CSRAlias map. Every CSR alias saves the last
61 // overlapping CSR.
62 CalleeSavedAliases.assign(TRI->getNumRegs(), 0);
63 for (const MCPhysReg *I = CSR; *I; ++I)
64 for (MCRegAliasIterator AI(*I, TRI, true); AI.isValid(); ++AI)
65 CalleeSavedAliases[*AI] = *I;
66
67 Update = true;
68 }
69 CalleeSavedRegs = CSR;
70
71 RegCosts = TRI->getRegisterCosts(*MF);
72
73 // Different reserved registers?
74 const BitVector &RR = MF->getRegInfo().getReservedRegs();
75 if (Reserved.size() != RR.size() || RR != Reserved) {
76 Update = true;
77 Reserved = RR;
78 }
79
80 // Invalidate cached information from previous function.
81 if (Update) {
82 unsigned NumPSets = TRI->getNumRegPressureSets();
83 PSetLimits.reset(new unsigned[NumPSets]);
84 std::fill(&PSetLimits[0], &PSetLimits[NumPSets], 0);
85 ++Tag;
86 }
87}
88
89/// compute - Compute the preferred allocation order for RC with reserved
90/// registers filtered out. Volatile registers come first followed by CSR
91/// aliases ordered according to the CSR order specified by the target.
92void RegisterClassInfo::compute(const TargetRegisterClass *RC) const {
93 assert(RC && "no register class given")((void)0);
94 RCInfo &RCI = RegClass[RC->getID()];
5
←
Called C++ object pointer is null
95 auto &STI = MF->getSubtarget();
96
97 // Raw register count, including all reserved regs.
98 unsigned NumRegs = RC->getNumRegs();
99
100 if (!RCI.Order)
101 RCI.Order.reset(new MCPhysReg[NumRegs]);
102
103 unsigned N = 0;
104 SmallVector<MCPhysReg, 16> CSRAlias;
105 uint8_t MinCost = uint8_t(~0u);
106 uint8_t LastCost = uint8_t(~0u);
107 unsigned LastCostChange = 0;
108
109 // FIXME: Once targets reserve registers instead of removing them from the
110 // allocation order, we can simply use begin/end here.
111 ArrayRef<MCPhysReg> RawOrder = RC->getRawAllocationOrder(*MF);
112 for (unsigned i = 0; i != RawOrder.size(); ++i) {
113 unsigned PhysReg = RawOrder[i];
114 // Remove reserved registers from the allocation order.
115 if (Reserved.test(PhysReg))
116 continue;
117 uint8_t Cost = RegCosts[PhysReg];
118 MinCost = std::min(MinCost, Cost);
119
120 if (CalleeSavedAliases[PhysReg] &&
121 !STI.ignoreCSRForAllocationOrder(*MF, PhysReg))
122 // PhysReg aliases a CSR, save it for later.
123 CSRAlias.push_back(PhysReg);
124 else {
125 if (Cost != LastCost)
126 LastCostChange = N;
127 RCI.Order[N++] = PhysReg;
128 LastCost = Cost;
129 }
130 }
131 RCI.NumRegs = N + CSRAlias.size();
132 assert(RCI.NumRegs <= NumRegs && "Allocation order larger than regclass")((void)0);
133
134 // CSR aliases go after the volatile registers, preserve the target's order.
135 for (unsigned i = 0, e = CSRAlias.size(); i != e; ++i) {
136 unsigned PhysReg = CSRAlias[i];
137 uint8_t Cost = RegCosts[PhysReg];
138 if (Cost != LastCost)
139 LastCostChange = N;
140 RCI.Order[N++] = PhysReg;
141 LastCost = Cost;
142 }
143
144 // Register allocator stress test. Clip register class to N registers.
145 if (StressRA && RCI.NumRegs > StressRA)
146 RCI.NumRegs = StressRA;
147
148 // Check if RC is a proper sub-class.
149 if (const TargetRegisterClass *Super =
150 TRI->getLargestLegalSuperClass(RC, *MF))
151 if (Super != RC && getNumAllocatableRegs(Super) > RCI.NumRegs)
152 RCI.ProperSubClass = true;
153
154 RCI.MinCost = MinCost;
155 RCI.LastCostChange = LastCostChange;
156
157 LLVM_DEBUG({do { } while (false)
158 dbgs() << "AllocationOrder(" << TRI->getRegClassName(RC) << ") = [";do { } while (false)
159 for (unsigned I = 0; I != RCI.NumRegs; ++I)do { } while (false)
160 dbgs() << ' ' << printReg(RCI.Order[I], TRI);do { } while (false)
161 dbgs() << (RCI.ProperSubClass ? " ] (sub-class)\n" : " ]\n");do { } while (false)
162 })do { } while (false);
163
164 // RCI is now up-to-date.
165 RCI.Tag = Tag;
166}
167
168/// This is not accurate because two overlapping register sets may have some
169/// nonoverlapping reserved registers. However, computing the allocation order
170/// for all register classes would be too expensive.
171unsigned RegisterClassInfo::computePSetLimit(unsigned Idx) const {
172 const TargetRegisterClass *RC = nullptr;
1
'RC' initialized to a null pointer value
→
173 unsigned NumRCUnits = 0;
174 for (const TargetRegisterClass *C : TRI->regclasses()) {
2
←
Assuming '__begin1' is equal to '__end1'
→
175 const int *PSetID = TRI->getRegClassPressureSets(C);
176 for (; *PSetID != -1; ++PSetID) {
177 if ((unsigned)*PSetID == Idx)
178 break;
179 }
180 if (*PSetID == -1)
181 continue;
182
183 // Found a register class that counts against this pressure set.
184 // For efficiency, only compute the set order for the largest set.
185 unsigned NUnits = TRI->getRegClassWeight(C).WeightLimit;
186 if (!RC || NUnits > NumRCUnits) {
187 RC = C;
188 NumRCUnits = NUnits;
189 }
190 }
191 assert(RC && "Failed to find register class")((void)0);
192 compute(RC);
3
←
Passing null pointer value via 1st parameter 'RC'
→
4
←
Calling 'RegisterClassInfo::compute'
→
193 unsigned NAllocatableRegs = getNumAllocatableRegs(RC);
194 unsigned RegPressureSetLimit = TRI->getRegPressureSetLimit(*MF, Idx);
195 // If all the regs are reserved, return raw RegPressureSetLimit.
196 // One example is VRSAVERC in PowerPC.
197 // Avoid returning zero, getRegPressureSetLimit(Idx) assumes computePSetLimit
198 // return non-zero value.
199 if (NAllocatableRegs == 0)
200 return RegPressureSetLimit;
201 unsigned NReserved = RC->getNumRegs() - NAllocatableRegs;
202 return RegPressureSetLimit - TRI->getRegClassWeight(RC).RegWeight * NReserved;
203}