| File: | src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/lib/CodeGen/MachineLoopInfo.cpp |
| Warning: | line 143, column 33 Called C++ object pointer is null |
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| 1 | //===- MachineLoopInfo.cpp - Natural Loop Calculator ----------------------===// | |||
| 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 defines the MachineLoopInfo class that is used to identify natural | |||
| 10 | // loops and determine the loop depth of various nodes of the CFG. Note that | |||
| 11 | // the loops identified may actually be several natural loops that share the | |||
| 12 | // same header node... not just a single natural loop. | |||
| 13 | // | |||
| 14 | //===----------------------------------------------------------------------===// | |||
| 15 | ||||
| 16 | #include "llvm/CodeGen/MachineLoopInfo.h" | |||
| 17 | #include "llvm/Analysis/LoopInfoImpl.h" | |||
| 18 | #include "llvm/CodeGen/MachineDominators.h" | |||
| 19 | #include "llvm/CodeGen/MachineRegisterInfo.h" | |||
| 20 | #include "llvm/CodeGen/Passes.h" | |||
| 21 | #include "llvm/CodeGen/TargetSubtargetInfo.h" | |||
| 22 | #include "llvm/Config/llvm-config.h" | |||
| 23 | #include "llvm/InitializePasses.h" | |||
| 24 | #include "llvm/Support/Debug.h" | |||
| 25 | #include "llvm/Support/raw_ostream.h" | |||
| 26 | ||||
| 27 | using namespace llvm; | |||
| 28 | ||||
| 29 | // Explicitly instantiate methods in LoopInfoImpl.h for MI-level Loops. | |||
| 30 | template class llvm::LoopBase<MachineBasicBlock, MachineLoop>; | |||
| 31 | template class llvm::LoopInfoBase<MachineBasicBlock, MachineLoop>; | |||
| 32 | ||||
| 33 | char MachineLoopInfo::ID = 0; | |||
| 34 | MachineLoopInfo::MachineLoopInfo() : MachineFunctionPass(ID) { | |||
| 35 | initializeMachineLoopInfoPass(*PassRegistry::getPassRegistry()); | |||
| 36 | } | |||
| 37 | INITIALIZE_PASS_BEGIN(MachineLoopInfo, "machine-loops",static void *initializeMachineLoopInfoPassOnce(PassRegistry & Registry) { | |||
| 38 | "Machine Natural Loop Construction", true, true)static void *initializeMachineLoopInfoPassOnce(PassRegistry & Registry) { | |||
| 39 | INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)initializeMachineDominatorTreePass(Registry); | |||
| 40 | INITIALIZE_PASS_END(MachineLoopInfo, "machine-loops",PassInfo *PI = new PassInfo( "Machine Natural Loop Construction" , "machine-loops", &MachineLoopInfo::ID, PassInfo::NormalCtor_t (callDefaultCtor<MachineLoopInfo>), true, true); Registry .registerPass(*PI, true); return PI; } static llvm::once_flag InitializeMachineLoopInfoPassFlag; void llvm::initializeMachineLoopInfoPass (PassRegistry &Registry) { llvm::call_once(InitializeMachineLoopInfoPassFlag , initializeMachineLoopInfoPassOnce, std::ref(Registry)); } | |||
| 41 | "Machine Natural Loop Construction", true, true)PassInfo *PI = new PassInfo( "Machine Natural Loop Construction" , "machine-loops", &MachineLoopInfo::ID, PassInfo::NormalCtor_t (callDefaultCtor<MachineLoopInfo>), true, true); Registry .registerPass(*PI, true); return PI; } static llvm::once_flag InitializeMachineLoopInfoPassFlag; void llvm::initializeMachineLoopInfoPass (PassRegistry &Registry) { llvm::call_once(InitializeMachineLoopInfoPassFlag , initializeMachineLoopInfoPassOnce, std::ref(Registry)); } | |||
| 42 | ||||
| 43 | char &llvm::MachineLoopInfoID = MachineLoopInfo::ID; | |||
| 44 | ||||
| 45 | bool MachineLoopInfo::runOnMachineFunction(MachineFunction &) { | |||
| 46 | calculate(getAnalysis<MachineDominatorTree>()); | |||
| 47 | return false; | |||
| 48 | } | |||
| 49 | ||||
| 50 | void MachineLoopInfo::calculate(MachineDominatorTree &MDT) { | |||
| 51 | releaseMemory(); | |||
| 52 | LI.analyze(MDT.getBase()); | |||
| 53 | } | |||
| 54 | ||||
| 55 | void MachineLoopInfo::getAnalysisUsage(AnalysisUsage &AU) const { | |||
| 56 | AU.setPreservesAll(); | |||
| 57 | AU.addRequired<MachineDominatorTree>(); | |||
| 58 | MachineFunctionPass::getAnalysisUsage(AU); | |||
| 59 | } | |||
| 60 | ||||
| 61 | MachineBasicBlock *MachineLoop::getTopBlock() { | |||
| 62 | MachineBasicBlock *TopMBB = getHeader(); | |||
| 63 | MachineFunction::iterator Begin = TopMBB->getParent()->begin(); | |||
| 64 | if (TopMBB->getIterator() != Begin) { | |||
| 65 | MachineBasicBlock *PriorMBB = &*std::prev(TopMBB->getIterator()); | |||
| 66 | while (contains(PriorMBB)) { | |||
| 67 | TopMBB = PriorMBB; | |||
| 68 | if (TopMBB->getIterator() == Begin) | |||
| 69 | break; | |||
| 70 | PriorMBB = &*std::prev(TopMBB->getIterator()); | |||
| 71 | } | |||
| 72 | } | |||
| 73 | return TopMBB; | |||
| 74 | } | |||
| 75 | ||||
| 76 | MachineBasicBlock *MachineLoop::getBottomBlock() { | |||
| 77 | MachineBasicBlock *BotMBB = getHeader(); | |||
| 78 | MachineFunction::iterator End = BotMBB->getParent()->end(); | |||
| 79 | if (BotMBB->getIterator() != std::prev(End)) { | |||
| 80 | MachineBasicBlock *NextMBB = &*std::next(BotMBB->getIterator()); | |||
| 81 | while (contains(NextMBB)) { | |||
| 82 | BotMBB = NextMBB; | |||
| 83 | if (BotMBB == &*std::next(BotMBB->getIterator())) | |||
| 84 | break; | |||
| 85 | NextMBB = &*std::next(BotMBB->getIterator()); | |||
| 86 | } | |||
| 87 | } | |||
| 88 | return BotMBB; | |||
| 89 | } | |||
| 90 | ||||
| 91 | MachineBasicBlock *MachineLoop::findLoopControlBlock() { | |||
| 92 | if (MachineBasicBlock *Latch = getLoopLatch()) { | |||
| 93 | if (isLoopExiting(Latch)) | |||
| 94 | return Latch; | |||
| 95 | else | |||
| 96 | return getExitingBlock(); | |||
| 97 | } | |||
| 98 | return nullptr; | |||
| 99 | } | |||
| 100 | ||||
| 101 | DebugLoc MachineLoop::getStartLoc() const { | |||
| 102 | // Try the pre-header first. | |||
| 103 | if (MachineBasicBlock *PHeadMBB = getLoopPreheader()) | |||
| 104 | if (const BasicBlock *PHeadBB = PHeadMBB->getBasicBlock()) | |||
| 105 | if (DebugLoc DL = PHeadBB->getTerminator()->getDebugLoc()) | |||
| 106 | return DL; | |||
| 107 | ||||
| 108 | // If we have no pre-header or there are no instructions with debug | |||
| 109 | // info in it, try the header. | |||
| 110 | if (MachineBasicBlock *HeadMBB = getHeader()) | |||
| 111 | if (const BasicBlock *HeadBB = HeadMBB->getBasicBlock()) | |||
| 112 | return HeadBB->getTerminator()->getDebugLoc(); | |||
| 113 | ||||
| 114 | return DebugLoc(); | |||
| 115 | } | |||
| 116 | ||||
| 117 | MachineBasicBlock * | |||
| 118 | MachineLoopInfo::findLoopPreheader(MachineLoop *L, bool SpeculativePreheader, | |||
| 119 | bool FindMultiLoopPreheader) const { | |||
| 120 | if (MachineBasicBlock *PB = L->getLoopPreheader()) | |||
| ||||
| 121 | return PB; | |||
| 122 | ||||
| 123 | if (!SpeculativePreheader) | |||
| 124 | return nullptr; | |||
| 125 | ||||
| 126 | MachineBasicBlock *HB = L->getHeader(), *LB = L->getLoopLatch(); | |||
| 127 | if (HB->pred_size() != 2 || HB->hasAddressTaken()) | |||
| 128 | return nullptr; | |||
| 129 | // Find the predecessor of the header that is not the latch block. | |||
| 130 | MachineBasicBlock *Preheader = nullptr; | |||
| 131 | for (MachineBasicBlock *P : HB->predecessors()) { | |||
| 132 | if (P == LB) | |||
| 133 | continue; | |||
| 134 | // Sanity. | |||
| 135 | if (Preheader) | |||
| 136 | return nullptr; | |||
| 137 | Preheader = P; | |||
| 138 | } | |||
| 139 | ||||
| 140 | // Check if the preheader candidate is a successor of any other loop | |||
| 141 | // headers. We want to avoid having two loop setups in the same block. | |||
| 142 | if (!FindMultiLoopPreheader) { | |||
| 143 | for (MachineBasicBlock *S : Preheader->successors()) { | |||
| ||||
| 144 | if (S == HB) | |||
| 145 | continue; | |||
| 146 | MachineLoop *T = getLoopFor(S); | |||
| 147 | if (T && T->getHeader() == S) | |||
| 148 | return nullptr; | |||
| 149 | } | |||
| 150 | } | |||
| 151 | return Preheader; | |||
| 152 | } | |||
| 153 | ||||
| 154 | bool MachineLoop::isLoopInvariant(MachineInstr &I) const { | |||
| 155 | MachineFunction *MF = I.getParent()->getParent(); | |||
| 156 | MachineRegisterInfo *MRI = &MF->getRegInfo(); | |||
| 157 | const TargetRegisterInfo *TRI = MF->getSubtarget().getRegisterInfo(); | |||
| 158 | ||||
| 159 | // The instruction is loop invariant if all of its operands are. | |||
| 160 | for (const MachineOperand &MO : I.operands()) { | |||
| 161 | if (!MO.isReg()) | |||
| 162 | continue; | |||
| 163 | ||||
| 164 | Register Reg = MO.getReg(); | |||
| 165 | if (Reg == 0) continue; | |||
| 166 | ||||
| 167 | // An instruction that uses or defines a physical register can't e.g. be | |||
| 168 | // hoisted, so mark this as not invariant. | |||
| 169 | if (Register::isPhysicalRegister(Reg)) { | |||
| 170 | if (MO.isUse()) { | |||
| 171 | // If the physreg has no defs anywhere, it's just an ambient register | |||
| 172 | // and we can freely move its uses. Alternatively, if it's allocatable, | |||
| 173 | // it could get allocated to something with a def during allocation. | |||
| 174 | // However, if the physreg is known to always be caller saved/restored | |||
| 175 | // then this use is safe to hoist. | |||
| 176 | if (!MRI->isConstantPhysReg(Reg) && | |||
| 177 | !(TRI->isCallerPreservedPhysReg(Reg.asMCReg(), *I.getMF()))) | |||
| 178 | return false; | |||
| 179 | // Otherwise it's safe to move. | |||
| 180 | continue; | |||
| 181 | } else if (!MO.isDead()) { | |||
| 182 | // A def that isn't dead can't be moved. | |||
| 183 | return false; | |||
| 184 | } else if (getHeader()->isLiveIn(Reg)) { | |||
| 185 | // If the reg is live into the loop, we can't hoist an instruction | |||
| 186 | // which would clobber it. | |||
| 187 | return false; | |||
| 188 | } | |||
| 189 | } | |||
| 190 | ||||
| 191 | if (!MO.isUse()) | |||
| 192 | continue; | |||
| 193 | ||||
| 194 | assert(MRI->getVRegDef(Reg) &&((void)0) | |||
| 195 | "Machine instr not mapped for this vreg?!")((void)0); | |||
| 196 | ||||
| 197 | // If the loop contains the definition of an operand, then the instruction | |||
| 198 | // isn't loop invariant. | |||
| 199 | if (contains(MRI->getVRegDef(Reg))) | |||
| 200 | return false; | |||
| 201 | } | |||
| 202 | ||||
| 203 | // If we got this far, the instruction is loop invariant! | |||
| 204 | return true; | |||
| 205 | } | |||
| 206 | ||||
| 207 | #if !defined(NDEBUG1) || defined(LLVM_ENABLE_DUMP) | |||
| 208 | LLVM_DUMP_METHOD__attribute__((noinline)) void MachineLoop::dump() const { | |||
| 209 | print(dbgs()); | |||
| 210 | } | |||
| 211 | #endif |