diff options
Diffstat (limited to 'contrib/llvm/lib/CodeGen/PeepholeOptimizer.cpp')
| -rw-r--r-- | contrib/llvm/lib/CodeGen/PeepholeOptimizer.cpp | 519 |
1 files changed, 445 insertions, 74 deletions
diff --git a/contrib/llvm/lib/CodeGen/PeepholeOptimizer.cpp b/contrib/llvm/lib/CodeGen/PeepholeOptimizer.cpp index 28f2d2f..716cb1f 100644 --- a/contrib/llvm/lib/CodeGen/PeepholeOptimizer.cpp +++ b/contrib/llvm/lib/CodeGen/PeepholeOptimizer.cpp @@ -66,7 +66,6 @@ // C = copy A <-- same-bank copy //===----------------------------------------------------------------------===// -#define DEBUG_TYPE "peephole-opt" #include "llvm/CodeGen/Passes.h" #include "llvm/ADT/DenseMap.h" #include "llvm/ADT/SmallPtrSet.h" @@ -81,6 +80,8 @@ #include "llvm/Target/TargetRegisterInfo.h" using namespace llvm; +#define DEBUG_TYPE "peephole-opt" + // Optimize Extensions static cl::opt<bool> Aggressive("aggressive-ext-opt", cl::Hidden, @@ -90,6 +91,10 @@ static cl::opt<bool> DisablePeephole("disable-peephole", cl::Hidden, cl::init(false), cl::desc("Disable the peephole optimizer")); +static cl::opt<bool> +DisableAdvCopyOpt("disable-adv-copy-opt", cl::Hidden, cl::init(true), + cl::desc("Disable advanced copy optimization")); + STATISTIC(NumReuse, "Number of extension results reused"); STATISTIC(NumCmps, "Number of compares eliminated"); STATISTIC(NumImmFold, "Number of move immediate folded"); @@ -110,9 +115,9 @@ namespace { initializePeepholeOptimizerPass(*PassRegistry::getPassRegistry()); } - virtual bool runOnMachineFunction(MachineFunction &MF); + bool runOnMachineFunction(MachineFunction &MF) override; - virtual void getAnalysisUsage(AnalysisUsage &AU) const { + void getAnalysisUsage(AnalysisUsage &AU) const override { AU.setPreservesCFG(); MachineFunctionPass::getAnalysisUsage(AU); if (Aggressive) { @@ -133,7 +138,107 @@ namespace { bool foldImmediate(MachineInstr *MI, MachineBasicBlock *MBB, SmallSet<unsigned, 4> &ImmDefRegs, DenseMap<unsigned, MachineInstr*> &ImmDefMIs); - bool isLoadFoldable(MachineInstr *MI, unsigned &FoldAsLoadDefReg); + bool isLoadFoldable(MachineInstr *MI, + SmallSet<unsigned, 16> &FoldAsLoadDefCandidates); + }; + + /// \brief Helper class to track the possible sources of a value defined by + /// a (chain of) copy related instructions. + /// Given a definition (instruction and definition index), this class + /// follows the use-def chain to find successive suitable sources. + /// The given source can be used to rewrite the definition into + /// def = COPY src. + /// + /// For instance, let us consider the following snippet: + /// v0 = + /// v2 = INSERT_SUBREG v1, v0, sub0 + /// def = COPY v2.sub0 + /// + /// Using a ValueTracker for def = COPY v2.sub0 will give the following + /// suitable sources: + /// v2.sub0 and v0. + /// Then, def can be rewritten into def = COPY v0. + class ValueTracker { + private: + /// The current point into the use-def chain. + const MachineInstr *Def; + /// The index of the definition in Def. + unsigned DefIdx; + /// The sub register index of the definition. + unsigned DefSubReg; + /// The register where the value can be found. + unsigned Reg; + /// Specifiy whether or not the value tracking looks through + /// complex instructions. When this is false, the value tracker + /// bails on everything that is not a copy or a bitcast. + /// + /// Note: This could have been implemented as a specialized version of + /// the ValueTracker class but that would have complicated the code of + /// the users of this class. + bool UseAdvancedTracking; + /// Optional MachineRegisterInfo used to perform some complex + /// tracking. + const MachineRegisterInfo *MRI; + + /// \brief Dispatcher to the right underlying implementation of + /// getNextSource. + bool getNextSourceImpl(unsigned &SrcIdx, unsigned &SrcSubReg); + /// \brief Specialized version of getNextSource for Copy instructions. + bool getNextSourceFromCopy(unsigned &SrcIdx, unsigned &SrcSubReg); + /// \brief Specialized version of getNextSource for Bitcast instructions. + bool getNextSourceFromBitcast(unsigned &SrcIdx, unsigned &SrcSubReg); + /// \brief Specialized version of getNextSource for RegSequence + /// instructions. + bool getNextSourceFromRegSequence(unsigned &SrcIdx, unsigned &SrcSubReg); + /// \brief Specialized version of getNextSource for InsertSubreg + /// instructions. + bool getNextSourceFromInsertSubreg(unsigned &SrcIdx, unsigned &SrcSubReg); + /// \brief Specialized version of getNextSource for ExtractSubreg + /// instructions. + bool getNextSourceFromExtractSubreg(unsigned &SrcIdx, unsigned &SrcSubReg); + /// \brief Specialized version of getNextSource for SubregToReg + /// instructions. + bool getNextSourceFromSubregToReg(unsigned &SrcIdx, unsigned &SrcSubReg); + + public: + /// \brief Create a ValueTracker instance for the value defines by \p MI + /// at the operand index \p DefIdx. + /// \p DefSubReg represents the sub register index the value tracker will + /// track. It does not need to match the sub register index used in \p MI. + /// \p UseAdvancedTracking specifies whether or not the value tracker looks + /// through complex instructions. By default (false), it handles only copy + /// and bitcast instructions. + /// \p MRI useful to perform some complex checks. + ValueTracker(const MachineInstr &MI, unsigned DefIdx, unsigned DefSubReg, + bool UseAdvancedTracking = false, + const MachineRegisterInfo *MRI = nullptr) + : Def(&MI), DefIdx(DefIdx), DefSubReg(DefSubReg), + UseAdvancedTracking(UseAdvancedTracking), MRI(MRI) { + assert(Def->getOperand(DefIdx).isDef() && + Def->getOperand(DefIdx).isReg() && + "Definition does not match machine instruction"); + // Initially the value is in the defined register. + Reg = Def->getOperand(DefIdx).getReg(); + } + + /// \brief Following the use-def chain, get the next available source + /// for the tracked value. + /// When the returned value is not nullptr, getReg() gives the register + /// that contain the tracked value. + /// \note The sub register index returned in \p SrcSubReg must be used + /// on that getReg() to access the actual value. + /// \return Unless the returned value is nullptr (i.e., no source found), + /// \p SrcIdx gives the index of the next source in the returned + /// instruction and \p SrcSubReg the index to be used on that source to + /// get the tracked value. When nullptr is returned, no alternative source + /// has been found. + const MachineInstr *getNextSource(unsigned &SrcIdx, unsigned &SrcSubReg); + + /// \brief Get the last register where the initial value can be found. + /// Initially this is the register of the definition. + /// Then, after each successful call to getNextSource, this is the + /// register of the last source. + unsigned getReg() const { return Reg; } }; } @@ -182,15 +287,13 @@ optimizeExtInstr(MachineInstr *MI, MachineBasicBlock *MBB, // If UseSrcSubIdx is Set, SubIdx also applies to SrcReg, and only uses of // SrcReg:SubIdx should be replaced. bool UseSrcSubIdx = TM->getRegisterInfo()-> - getSubClassWithSubReg(MRI->getRegClass(SrcReg), SubIdx) != 0; + getSubClassWithSubReg(MRI->getRegClass(SrcReg), SubIdx) != nullptr; // The source has other uses. See if we can replace the other uses with use of // the result of the extension. SmallPtrSet<MachineBasicBlock*, 4> ReachedBBs; - for (MachineRegisterInfo::use_nodbg_iterator - UI = MRI->use_nodbg_begin(DstReg), UE = MRI->use_nodbg_end(); - UI != UE; ++UI) - ReachedBBs.insert(UI->getParent()); + for (MachineInstr &UI : MRI->use_nodbg_instructions(DstReg)) + ReachedBBs.insert(UI.getParent()); // Uses that are in the same BB of uses of the result of the instruction. SmallVector<MachineOperand*, 8> Uses; @@ -199,11 +302,8 @@ optimizeExtInstr(MachineInstr *MI, MachineBasicBlock *MBB, SmallVector<MachineOperand*, 8> ExtendedUses; bool ExtendLife = true; - for (MachineRegisterInfo::use_nodbg_iterator - UI = MRI->use_nodbg_begin(SrcReg), UE = MRI->use_nodbg_end(); - UI != UE; ++UI) { - MachineOperand &UseMO = UI.getOperand(); - MachineInstr *UseMI = &*UI; + for (MachineOperand &UseMO : MRI->use_nodbg_operands(SrcReg)) { + MachineInstr *UseMI = UseMO.getParent(); if (UseMI == MI) continue; @@ -270,11 +370,9 @@ optimizeExtInstr(MachineInstr *MI, MachineBasicBlock *MBB, // Look for PHI uses of the extended result, we don't want to extend the // liveness of a PHI input. It breaks all kinds of assumptions down // stream. A PHI use is expected to be the kill of its source values. - for (MachineRegisterInfo::use_nodbg_iterator - UI = MRI->use_nodbg_begin(DstReg), UE = MRI->use_nodbg_end(); - UI != UE; ++UI) - if (UI->isPHI()) - PHIBBs.insert(UI->getParent()); + for (MachineInstr &UI : MRI->use_nodbg_instructions(DstReg)) + if (UI.isPHI()) + PHIBBs.insert(UI.getParent()); const TargetRegisterClass *RC = MRI->getRegClass(SrcReg); for (unsigned i = 0, e = Uses.size(); i != e; ++i) { @@ -364,7 +462,7 @@ static bool shareSameRegisterFile(const TargetRegisterInfo &TRI, unsigned SrcIdx, DefIdx; if (SrcSubReg && DefSubReg) return TRI.getCommonSuperRegClass(SrcRC, SrcSubReg, DefRC, DefSubReg, - SrcIdx, DefIdx) != NULL; + SrcIdx, DefIdx) != nullptr; // At most one of the register is a sub register, make it Src to avoid // duplicating the test. if (!SrcSubReg) { @@ -374,9 +472,9 @@ static bool shareSameRegisterFile(const TargetRegisterInfo &TRI, // One of the register is a sub register, check if we can get a superclass. if (SrcSubReg) - return TRI.getMatchingSuperRegClass(SrcRC, DefRC, SrcSubReg) != NULL; + return TRI.getMatchingSuperRegClass(SrcRC, DefRC, SrcSubReg) != nullptr; // Plain copy. - return TRI.getCommonSubClass(DefRC, SrcRC) != NULL; + return TRI.getCommonSubClass(DefRC, SrcRC) != nullptr; } /// \brief Get the index of the definition and source for \p Copy @@ -448,31 +546,32 @@ bool PeepholeOptimizer::optimizeCopyOrBitcast(MachineInstr *MI) { unsigned Src; unsigned SrcSubReg; bool ShouldRewrite = false; - MachineInstr *Copy = MI; const TargetRegisterInfo &TRI = *TM->getRegisterInfo(); - // Follow the chain of copies until we reach the top or find a - // more suitable source. + // Follow the chain of copies until we reach the top of the use-def chain + // or find a more suitable source. + ValueTracker ValTracker(*MI, DefIdx, DefSubReg, !DisableAdvCopyOpt, MRI); do { - unsigned CopyDefIdx, CopySrcIdx; - if (!getCopyOrBitcastDefUseIdx(*Copy, CopyDefIdx, CopySrcIdx)) + unsigned CopySrcIdx, CopySrcSubReg; + if (!ValTracker.getNextSource(CopySrcIdx, CopySrcSubReg)) break; - const MachineOperand &MO = Copy->getOperand(CopySrcIdx); - assert(MO.isReg() && "Copies must be between registers."); - Src = MO.getReg(); - + Src = ValTracker.getReg(); + SrcSubReg = CopySrcSubReg; + + // Do not extend the live-ranges of physical registers as they add + // constraints to the register allocator. + // Moreover, if we want to extend the live-range of a physical register, + // unlike SSA virtual register, we will have to check that they are not + // redefine before the related use. if (TargetRegisterInfo::isPhysicalRegister(Src)) break; const TargetRegisterClass *SrcRC = MRI->getRegClass(Src); - SrcSubReg = MO.getSubReg(); // If this source does not incur a cross register bank copy, use it. ShouldRewrite = shareSameRegisterFile(TRI, DefRC, DefSubReg, SrcRC, SrcSubReg); - // Follow the chain of copies: get the definition of Src. - Copy = MRI->getVRegDef(Src); - } while (!ShouldRewrite && Copy && (Copy->isCopy() || Copy->isBitcast())); + } while (!ShouldRewrite); // If we did not find a more suitable source, there is nothing to optimize. if (!ShouldRewrite || Src == MI->getOperand(SrcIdx).getReg()) @@ -488,6 +587,9 @@ bool PeepholeOptimizer::optimizeCopyOrBitcast(MachineInstr *MI) { MRI->replaceRegWith(Def, NewVR); MRI->clearKillFlags(NewVR); + // We extended the lifetime of Src. + // Clear the kill flags to account for that. + MRI->clearKillFlags(Src); MI->eraseFromParent(); ++NumCopiesBitcasts; return true; @@ -496,8 +598,9 @@ bool PeepholeOptimizer::optimizeCopyOrBitcast(MachineInstr *MI) { /// isLoadFoldable - Check whether MI is a candidate for folding into a later /// instruction. We only fold loads to virtual registers and the virtual /// register defined has a single use. -bool PeepholeOptimizer::isLoadFoldable(MachineInstr *MI, - unsigned &FoldAsLoadDefReg) { +bool PeepholeOptimizer::isLoadFoldable( + MachineInstr *MI, + SmallSet<unsigned, 16> &FoldAsLoadDefCandidates) { if (!MI->canFoldAsLoad() || !MI->mayLoad()) return false; const MCInstrDesc &MCID = MI->getDesc(); @@ -505,13 +608,13 @@ bool PeepholeOptimizer::isLoadFoldable(MachineInstr *MI, return false; unsigned Reg = MI->getOperand(0).getReg(); - // To reduce compilation time, we check MRI->hasOneUse when inserting + // To reduce compilation time, we check MRI->hasOneNonDBGUse when inserting // loads. It should be checked when processing uses of the load, since // uses can be removed during peephole. if (!MI->getOperand(0).getSubReg() && TargetRegisterInfo::isVirtualRegister(Reg) && - MRI->hasOneUse(Reg)) { - FoldAsLoadDefReg = Reg; + MRI->hasOneNonDBGUse(Reg)) { + FoldAsLoadDefCandidates.insert(Reg); return true; } return false; @@ -561,6 +664,9 @@ bool PeepholeOptimizer::foldImmediate(MachineInstr *MI, MachineBasicBlock *MBB, } bool PeepholeOptimizer::runOnMachineFunction(MachineFunction &MF) { + if (skipOptnoneFunction(*MF.getFunction())) + return false; + DEBUG(dbgs() << "********** PEEPHOLE OPTIMIZER **********\n"); DEBUG(dbgs() << "********** Function: " << MF.getName() << '\n'); @@ -570,22 +676,18 @@ bool PeepholeOptimizer::runOnMachineFunction(MachineFunction &MF) { TM = &MF.getTarget(); TII = TM->getInstrInfo(); MRI = &MF.getRegInfo(); - DT = Aggressive ? &getAnalysis<MachineDominatorTree>() : 0; + DT = Aggressive ? &getAnalysis<MachineDominatorTree>() : nullptr; bool Changed = false; - SmallPtrSet<MachineInstr*, 8> LocalMIs; - SmallSet<unsigned, 4> ImmDefRegs; - DenseMap<unsigned, MachineInstr*> ImmDefMIs; - unsigned FoldAsLoadDefReg; for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) { MachineBasicBlock *MBB = &*I; bool SeenMoveImm = false; - LocalMIs.clear(); - ImmDefRegs.clear(); - ImmDefMIs.clear(); - FoldAsLoadDefReg = 0; + SmallPtrSet<MachineInstr*, 8> LocalMIs; + SmallSet<unsigned, 4> ImmDefRegs; + DenseMap<unsigned, MachineInstr*> ImmDefMIs; + SmallSet<unsigned, 16> FoldAsLoadDefCandidates; for (MachineBasicBlock::iterator MII = I->begin(), MIE = I->end(); MII != MIE; ) { @@ -594,16 +696,20 @@ bool PeepholeOptimizer::runOnMachineFunction(MachineFunction &MF) { ++MII; LocalMIs.insert(MI); + // Skip debug values. They should not affect this peephole optimization. + if (MI->isDebugValue()) + continue; + // If there exists an instruction which belongs to the following - // categories, we will discard the load candidate. - if (MI->isLabel() || MI->isPHI() || MI->isImplicitDef() || - MI->isKill() || MI->isInlineAsm() || MI->isDebugValue() || + // categories, we will discard the load candidates. + if (MI->isPosition() || MI->isPHI() || MI->isImplicitDef() || + MI->isKill() || MI->isInlineAsm() || MI->hasUnmodeledSideEffects()) { - FoldAsLoadDefReg = 0; + FoldAsLoadDefCandidates.clear(); continue; } if (MI->mayStore() || MI->isCall()) - FoldAsLoadDefReg = 0; + FoldAsLoadDefCandidates.clear(); if (((MI->isBitcast() || MI->isCopy()) && optimizeCopyOrBitcast(MI)) || (MI->isCompare() && optimizeCmpInstr(MI, MBB)) || @@ -630,26 +736,43 @@ bool PeepholeOptimizer::runOnMachineFunction(MachineFunction &MF) { // Check whether MI is a load candidate for folding into a later // instruction. If MI is not a candidate, check whether we can fold an // earlier load into MI. - if (!isLoadFoldable(MI, FoldAsLoadDefReg) && FoldAsLoadDefReg) { - // We need to fold load after optimizeCmpInstr, since optimizeCmpInstr - // can enable folding by converting SUB to CMP. - MachineInstr *DefMI = 0; - MachineInstr *FoldMI = TII->optimizeLoadInstr(MI, MRI, - FoldAsLoadDefReg, DefMI); - if (FoldMI) { - // Update LocalMIs since we replaced MI with FoldMI and deleted DefMI. - DEBUG(dbgs() << "Replacing: " << *MI); - DEBUG(dbgs() << " With: " << *FoldMI); - LocalMIs.erase(MI); - LocalMIs.erase(DefMI); - LocalMIs.insert(FoldMI); - MI->eraseFromParent(); - DefMI->eraseFromParent(); - ++NumLoadFold; - - // MI is replaced with FoldMI. - Changed = true; - continue; + if (!isLoadFoldable(MI, FoldAsLoadDefCandidates) && + !FoldAsLoadDefCandidates.empty()) { + const MCInstrDesc &MIDesc = MI->getDesc(); + for (unsigned i = MIDesc.getNumDefs(); i != MIDesc.getNumOperands(); + ++i) { + const MachineOperand &MOp = MI->getOperand(i); + if (!MOp.isReg()) + continue; + unsigned FoldAsLoadDefReg = MOp.getReg(); + if (FoldAsLoadDefCandidates.count(FoldAsLoadDefReg)) { + // We need to fold load after optimizeCmpInstr, since + // optimizeCmpInstr can enable folding by converting SUB to CMP. + // Save FoldAsLoadDefReg because optimizeLoadInstr() resets it and + // we need it for markUsesInDebugValueAsUndef(). + unsigned FoldedReg = FoldAsLoadDefReg; + MachineInstr *DefMI = nullptr; + MachineInstr *FoldMI = TII->optimizeLoadInstr(MI, MRI, + FoldAsLoadDefReg, + DefMI); + if (FoldMI) { + // Update LocalMIs since we replaced MI with FoldMI and deleted + // DefMI. + DEBUG(dbgs() << "Replacing: " << *MI); + DEBUG(dbgs() << " With: " << *FoldMI); + LocalMIs.erase(MI); + LocalMIs.erase(DefMI); + LocalMIs.insert(FoldMI); + MI->eraseFromParent(); + DefMI->eraseFromParent(); + MRI->markUsesInDebugValueAsUndef(FoldedReg); + FoldAsLoadDefCandidates.erase(FoldedReg); + ++NumLoadFold; + // MI is replaced with FoldMI. + Changed = true; + break; + } + } } } } @@ -657,3 +780,251 @@ bool PeepholeOptimizer::runOnMachineFunction(MachineFunction &MF) { return Changed; } + +bool ValueTracker::getNextSourceFromCopy(unsigned &SrcIdx, + unsigned &SrcSubReg) { + assert(Def->isCopy() && "Invalid definition"); + // Copy instruction are supposed to be: Def = Src. + // If someone breaks this assumption, bad things will happen everywhere. + assert(Def->getDesc().getNumOperands() == 2 && "Invalid number of operands"); + + if (Def->getOperand(DefIdx).getSubReg() != DefSubReg) + // If we look for a different subreg, it means we want a subreg of src. + // Bails as we do not support composing subreg yet. + return false; + // Otherwise, we want the whole source. + SrcIdx = 1; + SrcSubReg = Def->getOperand(SrcIdx).getSubReg(); + return true; +} + +bool ValueTracker::getNextSourceFromBitcast(unsigned &SrcIdx, + unsigned &SrcSubReg) { + assert(Def->isBitcast() && "Invalid definition"); + + // Bail if there are effects that a plain copy will not expose. + if (Def->hasUnmodeledSideEffects()) + return false; + + // Bitcasts with more than one def are not supported. + if (Def->getDesc().getNumDefs() != 1) + return false; + if (Def->getOperand(DefIdx).getSubReg() != DefSubReg) + // If we look for a different subreg, it means we want a subreg of the src. + // Bails as we do not support composing subreg yet. + return false; + + SrcIdx = Def->getDesc().getNumOperands(); + for (unsigned OpIdx = DefIdx + 1, EndOpIdx = SrcIdx; OpIdx != EndOpIdx; + ++OpIdx) { + const MachineOperand &MO = Def->getOperand(OpIdx); + if (!MO.isReg() || !MO.getReg()) + continue; + assert(!MO.isDef() && "We should have skipped all the definitions by now"); + if (SrcIdx != EndOpIdx) + // Multiple sources? + return false; + SrcIdx = OpIdx; + } + SrcSubReg = Def->getOperand(SrcIdx).getSubReg(); + return true; +} + +bool ValueTracker::getNextSourceFromRegSequence(unsigned &SrcIdx, + unsigned &SrcSubReg) { + assert(Def->isRegSequence() && "Invalid definition"); + + if (Def->getOperand(DefIdx).getSubReg()) + // If we are composing subreg, bails out. + // The case we are checking is Def.<subreg> = REG_SEQUENCE. + // This should almost never happen as the SSA property is tracked at + // the register level (as opposed to the subreg level). + // I.e., + // Def.sub0 = + // Def.sub1 = + // is a valid SSA representation for Def.sub0 and Def.sub1, but not for + // Def. Thus, it must not be generated. + // However, some code could theoretically generates a single + // Def.sub0 (i.e, not defining the other subregs) and we would + // have this case. + // If we can ascertain (or force) that this never happens, we could + // turn that into an assertion. + return false; + + // We are looking at: + // Def = REG_SEQUENCE v0, sub0, v1, sub1, ... + // Check if one of the operand defines the subreg we are interested in. + for (unsigned OpIdx = DefIdx + 1, EndOpIdx = Def->getNumOperands(); + OpIdx != EndOpIdx; OpIdx += 2) { + const MachineOperand &MOSubIdx = Def->getOperand(OpIdx + 1); + assert(MOSubIdx.isImm() && + "One of the subindex of the reg_sequence is not an immediate"); + if (MOSubIdx.getImm() == DefSubReg) { + assert(Def->getOperand(OpIdx).isReg() && + "One of the source of the reg_sequence is not a register"); + SrcIdx = OpIdx; + SrcSubReg = Def->getOperand(SrcIdx).getSubReg(); + return true; + } + } + + // If the subreg we are tracking is super-defined by another subreg, + // we could follow this value. However, this would require to compose + // the subreg and we do not do that for now. + return false; +} + +bool ValueTracker::getNextSourceFromInsertSubreg(unsigned &SrcIdx, + unsigned &SrcSubReg) { + assert(Def->isInsertSubreg() && "Invalid definition"); + if (Def->getOperand(DefIdx).getSubReg()) + // If we are composing subreg, bails out. + // Same remark as getNextSourceFromRegSequence. + // I.e., this may be turned into an assert. + return false; + + // We are looking at: + // Def = INSERT_SUBREG v0, v1, sub1 + // There are two cases: + // 1. DefSubReg == sub1, get v1. + // 2. DefSubReg != sub1, the value may be available through v0. + + // #1 Check if the inserted register matches the require sub index. + unsigned InsertedSubReg = Def->getOperand(3).getImm(); + if (InsertedSubReg == DefSubReg) { + SrcIdx = 2; + SrcSubReg = Def->getOperand(SrcIdx).getSubReg(); + return true; + } + // #2 Otherwise, if the sub register we are looking for is not partial + // defined by the inserted element, we can look through the main + // register (v0). + // To check the overlapping we need a MRI and a TRI. + if (!MRI) + return false; + + const MachineOperand &MODef = Def->getOperand(DefIdx); + const MachineOperand &MOBase = Def->getOperand(1); + // If the result register (Def) and the base register (v0) do not + // have the same register class or if we have to compose + // subregisters, bails out. + if (MRI->getRegClass(MODef.getReg()) != MRI->getRegClass(MOBase.getReg()) || + MOBase.getSubReg()) + return false; + + // Get the TRI and check if inserted sub register overlaps with the + // sub register we are tracking. + const TargetRegisterInfo *TRI = MRI->getTargetRegisterInfo(); + if (!TRI || + (TRI->getSubRegIndexLaneMask(DefSubReg) & + TRI->getSubRegIndexLaneMask(InsertedSubReg)) != 0) + return false; + // At this point, the value is available in v0 via the same subreg + // we used for Def. + SrcIdx = 1; + SrcSubReg = DefSubReg; + return true; +} + +bool ValueTracker::getNextSourceFromExtractSubreg(unsigned &SrcIdx, + unsigned &SrcSubReg) { + assert(Def->isExtractSubreg() && "Invalid definition"); + // We are looking at: + // Def = EXTRACT_SUBREG v0, sub0 + + // Bails if we have to compose sub registers. + // Indeed, if DefSubReg != 0, we would have to compose it with sub0. + if (DefSubReg) + return false; + + // Bails if we have to compose sub registers. + // Likewise, if v0.subreg != 0, we would have to compose v0.subreg with sub0. + if (Def->getOperand(1).getSubReg()) + return false; + // Otherwise, the value is available in the v0.sub0. + SrcIdx = 1; + SrcSubReg = Def->getOperand(2).getImm(); + return true; +} + +bool ValueTracker::getNextSourceFromSubregToReg(unsigned &SrcIdx, + unsigned &SrcSubReg) { + assert(Def->isSubregToReg() && "Invalid definition"); + // We are looking at: + // Def = SUBREG_TO_REG Imm, v0, sub0 + + // Bails if we have to compose sub registers. + // If DefSubReg != sub0, we would have to check that all the bits + // we track are included in sub0 and if yes, we would have to + // determine the right subreg in v0. + if (DefSubReg != Def->getOperand(3).getImm()) + return false; + // Bails if we have to compose sub registers. + // Likewise, if v0.subreg != 0, we would have to compose it with sub0. + if (Def->getOperand(2).getSubReg()) + return false; + + SrcIdx = 2; + SrcSubReg = Def->getOperand(3).getImm(); + return true; +} + +bool ValueTracker::getNextSourceImpl(unsigned &SrcIdx, unsigned &SrcSubReg) { + assert(Def && "This method needs a valid definition"); + + assert( + (DefIdx < Def->getDesc().getNumDefs() || Def->getDesc().isVariadic()) && + Def->getOperand(DefIdx).isDef() && "Invalid DefIdx"); + if (Def->isCopy()) + return getNextSourceFromCopy(SrcIdx, SrcSubReg); + if (Def->isBitcast()) + return getNextSourceFromBitcast(SrcIdx, SrcSubReg); + // All the remaining cases involve "complex" instructions. + // Bails if we did not ask for the advanced tracking. + if (!UseAdvancedTracking) + return false; + if (Def->isRegSequence()) + return getNextSourceFromRegSequence(SrcIdx, SrcSubReg); + if (Def->isInsertSubreg()) + return getNextSourceFromInsertSubreg(SrcIdx, SrcSubReg); + if (Def->isExtractSubreg()) + return getNextSourceFromExtractSubreg(SrcIdx, SrcSubReg); + if (Def->isSubregToReg()) + return getNextSourceFromSubregToReg(SrcIdx, SrcSubReg); + return false; +} + +const MachineInstr *ValueTracker::getNextSource(unsigned &SrcIdx, + unsigned &SrcSubReg) { + // If we reach a point where we cannot move up in the use-def chain, + // there is nothing we can get. + if (!Def) + return nullptr; + + const MachineInstr *PrevDef = nullptr; + // Try to find the next source. + if (getNextSourceImpl(SrcIdx, SrcSubReg)) { + // Update definition, definition index, and subregister for the + // next call of getNextSource. + const MachineOperand &MO = Def->getOperand(SrcIdx); + assert(MO.isReg() && !MO.isDef() && "Source is invalid"); + // Update the current register. + Reg = MO.getReg(); + // Update the return value before moving up in the use-def chain. + PrevDef = Def; + // If we can still move up in the use-def chain, move to the next + // defintion. + if (!TargetRegisterInfo::isPhysicalRegister(Reg)) { + Def = MRI->getVRegDef(Reg); + DefIdx = MRI->def_begin(Reg).getOperandNo(); + DefSubReg = SrcSubReg; + return PrevDef; + } + } + // If we end up here, this means we will not be able to find another source + // for the next iteration. + // Make sure any new call to getNextSource bails out early by cutting the + // use-def chain. + Def = nullptr; + return PrevDef; +} |
