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Diffstat (limited to 'contrib/llvm/lib/CodeGen/PeepholeOptimizer.cpp')
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diff --git a/contrib/llvm/lib/CodeGen/PeepholeOptimizer.cpp b/contrib/llvm/lib/CodeGen/PeepholeOptimizer.cpp new file mode 100644 index 0000000..52b42b6 --- /dev/null +++ b/contrib/llvm/lib/CodeGen/PeepholeOptimizer.cpp @@ -0,0 +1,1947 @@ +//===-- PeepholeOptimizer.cpp - Peephole Optimizations --------------------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// Perform peephole optimizations on the machine code: +// +// - Optimize Extensions +// +// Optimization of sign / zero extension instructions. It may be extended to +// handle other instructions with similar properties. +// +// On some targets, some instructions, e.g. X86 sign / zero extension, may +// leave the source value in the lower part of the result. This optimization +// will replace some uses of the pre-extension value with uses of the +// sub-register of the results. +// +// - Optimize Comparisons +// +// Optimization of comparison instructions. For instance, in this code: +// +// sub r1, 1 +// cmp r1, 0 +// bz L1 +// +// If the "sub" instruction all ready sets (or could be modified to set) the +// same flag that the "cmp" instruction sets and that "bz" uses, then we can +// eliminate the "cmp" instruction. +// +// Another instance, in this code: +// +// sub r1, r3 | sub r1, imm +// cmp r3, r1 or cmp r1, r3 | cmp r1, imm +// bge L1 +// +// If the branch instruction can use flag from "sub", then we can replace +// "sub" with "subs" and eliminate the "cmp" instruction. +// +// - Optimize Loads: +// +// Loads that can be folded into a later instruction. A load is foldable +// if it loads to virtual registers and the virtual register defined has +// a single use. +// +// - Optimize Copies and Bitcast (more generally, target specific copies): +// +// Rewrite copies and bitcasts to avoid cross register bank copies +// when possible. +// E.g., Consider the following example, where capital and lower +// letters denote different register file: +// b = copy A <-- cross-bank copy +// C = copy b <-- cross-bank copy +// => +// b = copy A <-- cross-bank copy +// C = copy A <-- same-bank copy +// +// E.g., for bitcast: +// b = bitcast A <-- cross-bank copy +// C = bitcast b <-- cross-bank copy +// => +// b = bitcast A <-- cross-bank copy +// C = copy A <-- same-bank copy +//===----------------------------------------------------------------------===// + +#include "llvm/CodeGen/Passes.h" +#include "llvm/ADT/DenseMap.h" +#include "llvm/ADT/SmallPtrSet.h" +#include "llvm/ADT/SmallSet.h" +#include "llvm/ADT/Statistic.h" +#include "llvm/CodeGen/MachineDominators.h" +#include "llvm/CodeGen/MachineInstrBuilder.h" +#include "llvm/CodeGen/MachineRegisterInfo.h" +#include "llvm/Support/CommandLine.h" +#include "llvm/Support/Debug.h" +#include "llvm/Support/raw_ostream.h" +#include "llvm/Target/TargetInstrInfo.h" +#include "llvm/Target/TargetRegisterInfo.h" +#include "llvm/Target/TargetSubtargetInfo.h" +#include <utility> +using namespace llvm; + +#define DEBUG_TYPE "peephole-opt" + +// Optimize Extensions +static cl::opt<bool> +Aggressive("aggressive-ext-opt", cl::Hidden, + cl::desc("Aggressive extension optimization")); + +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(false), + cl::desc("Disable advanced copy optimization")); + +static cl::opt<bool> DisableNAPhysCopyOpt( + "disable-non-allocatable-phys-copy-opt", cl::Hidden, cl::init(false), + cl::desc("Disable non-allocatable physical register copy optimization")); + +// Limit the number of PHI instructions to process +// in PeepholeOptimizer::getNextSource. +static cl::opt<unsigned> RewritePHILimit( + "rewrite-phi-limit", cl::Hidden, cl::init(10), + cl::desc("Limit the length of PHI chains to lookup")); + +STATISTIC(NumReuse, "Number of extension results reused"); +STATISTIC(NumCmps, "Number of compares eliminated"); +STATISTIC(NumImmFold, "Number of move immediate folded"); +STATISTIC(NumLoadFold, "Number of loads folded"); +STATISTIC(NumSelects, "Number of selects optimized"); +STATISTIC(NumUncoalescableCopies, "Number of uncoalescable copies optimized"); +STATISTIC(NumRewrittenCopies, "Number of copies rewritten"); +STATISTIC(NumNAPhysCopies, "Number of non-allocatable physical copies removed"); + +namespace { + class ValueTrackerResult; + + class PeepholeOptimizer : public MachineFunctionPass { + const TargetInstrInfo *TII; + const TargetRegisterInfo *TRI; + MachineRegisterInfo *MRI; + MachineDominatorTree *DT; // Machine dominator tree + + public: + static char ID; // Pass identification + PeepholeOptimizer() : MachineFunctionPass(ID) { + initializePeepholeOptimizerPass(*PassRegistry::getPassRegistry()); + } + + bool runOnMachineFunction(MachineFunction &MF) override; + + void getAnalysisUsage(AnalysisUsage &AU) const override { + AU.setPreservesCFG(); + MachineFunctionPass::getAnalysisUsage(AU); + if (Aggressive) { + AU.addRequired<MachineDominatorTree>(); + AU.addPreserved<MachineDominatorTree>(); + } + } + + /// \brief Track Def -> Use info used for rewriting copies. + typedef SmallDenseMap<TargetInstrInfo::RegSubRegPair, ValueTrackerResult> + RewriteMapTy; + + private: + bool optimizeCmpInstr(MachineInstr *MI, MachineBasicBlock *MBB); + bool optimizeExtInstr(MachineInstr *MI, MachineBasicBlock *MBB, + SmallPtrSetImpl<MachineInstr*> &LocalMIs); + bool optimizeSelect(MachineInstr *MI, + SmallPtrSetImpl<MachineInstr *> &LocalMIs); + bool optimizeCondBranch(MachineInstr *MI); + bool optimizeCoalescableCopy(MachineInstr *MI); + bool optimizeUncoalescableCopy(MachineInstr *MI, + SmallPtrSetImpl<MachineInstr *> &LocalMIs); + bool findNextSource(unsigned Reg, unsigned SubReg, + RewriteMapTy &RewriteMap); + bool isMoveImmediate(MachineInstr *MI, + SmallSet<unsigned, 4> &ImmDefRegs, + DenseMap<unsigned, MachineInstr*> &ImmDefMIs); + bool foldImmediate(MachineInstr *MI, MachineBasicBlock *MBB, + SmallSet<unsigned, 4> &ImmDefRegs, + DenseMap<unsigned, MachineInstr*> &ImmDefMIs); + + /// \brief If copy instruction \p MI is a virtual register copy, track it in + /// the set \p CopySrcRegs and \p CopyMIs. If this virtual register was + /// previously seen as a copy, replace the uses of this copy with the + /// previously seen copy's destination register. + bool foldRedundantCopy(MachineInstr *MI, + SmallSet<unsigned, 4> &CopySrcRegs, + DenseMap<unsigned, MachineInstr *> &CopyMIs); + + /// \brief Is the register \p Reg a non-allocatable physical register? + bool isNAPhysCopy(unsigned Reg); + + /// \brief If copy instruction \p MI is a non-allocatable virtual<->physical + /// register copy, track it in the \p NAPhysToVirtMIs map. If this + /// non-allocatable physical register was previously copied to a virtual + /// registered and hasn't been clobbered, the virt->phys copy can be + /// deleted. + bool foldRedundantNAPhysCopy( + MachineInstr *MI, + DenseMap<unsigned, MachineInstr *> &NAPhysToVirtMIs); + + bool isLoadFoldable(MachineInstr *MI, + SmallSet<unsigned, 16> &FoldAsLoadDefCandidates); + + /// \brief Check whether \p MI is understood by the register coalescer + /// but may require some rewriting. + bool isCoalescableCopy(const MachineInstr &MI) { + // SubregToRegs are not interesting, because they are already register + // coalescer friendly. + return MI.isCopy() || (!DisableAdvCopyOpt && + (MI.isRegSequence() || MI.isInsertSubreg() || + MI.isExtractSubreg())); + } + + /// \brief Check whether \p MI is a copy like instruction that is + /// not recognized by the register coalescer. + bool isUncoalescableCopy(const MachineInstr &MI) { + return MI.isBitcast() || + (!DisableAdvCopyOpt && + (MI.isRegSequenceLike() || MI.isInsertSubregLike() || + MI.isExtractSubregLike())); + } + }; + + /// \brief Helper class to hold a reply for ValueTracker queries. Contains the + /// returned sources for a given search and the instructions where the sources + /// were tracked from. + class ValueTrackerResult { + private: + /// Track all sources found by one ValueTracker query. + SmallVector<TargetInstrInfo::RegSubRegPair, 2> RegSrcs; + + /// Instruction using the sources in 'RegSrcs'. + const MachineInstr *Inst; + + public: + ValueTrackerResult() : Inst(nullptr) {} + ValueTrackerResult(unsigned Reg, unsigned SubReg) : Inst(nullptr) { + addSource(Reg, SubReg); + } + + bool isValid() const { return getNumSources() > 0; } + + void setInst(const MachineInstr *I) { Inst = I; } + const MachineInstr *getInst() const { return Inst; } + + void clear() { + RegSrcs.clear(); + Inst = nullptr; + } + + void addSource(unsigned SrcReg, unsigned SrcSubReg) { + RegSrcs.push_back(TargetInstrInfo::RegSubRegPair(SrcReg, SrcSubReg)); + } + + void setSource(int Idx, unsigned SrcReg, unsigned SrcSubReg) { + assert(Idx < getNumSources() && "Reg pair source out of index"); + RegSrcs[Idx] = TargetInstrInfo::RegSubRegPair(SrcReg, SrcSubReg); + } + + int getNumSources() const { return RegSrcs.size(); } + + unsigned getSrcReg(int Idx) const { + assert(Idx < getNumSources() && "Reg source out of index"); + return RegSrcs[Idx].Reg; + } + + unsigned getSrcSubReg(int Idx) const { + assert(Idx < getNumSources() && "SubReg source out of index"); + return RegSrcs[Idx].SubReg; + } + + bool operator==(const ValueTrackerResult &Other) { + if (Other.getInst() != getInst()) + return false; + + if (Other.getNumSources() != getNumSources()) + return false; + + for (int i = 0, e = Other.getNumSources(); i != e; ++i) + if (Other.getSrcReg(i) != getSrcReg(i) || + Other.getSrcSubReg(i) != getSrcSubReg(i)) + return false; + return true; + } + }; + + /// \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; + /// MachineRegisterInfo used to perform tracking. + const MachineRegisterInfo &MRI; + /// Optional TargetInstrInfo used to perform some complex + /// tracking. + const TargetInstrInfo *TII; + + /// \brief Dispatcher to the right underlying implementation of + /// getNextSource. + ValueTrackerResult getNextSourceImpl(); + /// \brief Specialized version of getNextSource for Copy instructions. + ValueTrackerResult getNextSourceFromCopy(); + /// \brief Specialized version of getNextSource for Bitcast instructions. + ValueTrackerResult getNextSourceFromBitcast(); + /// \brief Specialized version of getNextSource for RegSequence + /// instructions. + ValueTrackerResult getNextSourceFromRegSequence(); + /// \brief Specialized version of getNextSource for InsertSubreg + /// instructions. + ValueTrackerResult getNextSourceFromInsertSubreg(); + /// \brief Specialized version of getNextSource for ExtractSubreg + /// instructions. + ValueTrackerResult getNextSourceFromExtractSubreg(); + /// \brief Specialized version of getNextSource for SubregToReg + /// instructions. + ValueTrackerResult getNextSourceFromSubregToReg(); + /// \brief Specialized version of getNextSource for PHI instructions. + ValueTrackerResult getNextSourceFromPHI(); + + public: + /// \brief Create a ValueTracker instance for the value defined by \p Reg. + /// \p DefSubReg represents the sub register index the value tracker will + /// track. It does not need to match the sub register index used in the + /// definition of \p Reg. + /// \p UseAdvancedTracking specifies whether or not the value tracker looks + /// through complex instructions. By default (false), it handles only copy + /// and bitcast instructions. + /// If \p Reg is a physical register, a value tracker constructed with + /// this constructor will not find any alternative source. + /// Indeed, when \p Reg is a physical register that constructor does not + /// know which definition of \p Reg it should track. + /// Use the next constructor to track a physical register. + ValueTracker(unsigned Reg, unsigned DefSubReg, + const MachineRegisterInfo &MRI, + bool UseAdvancedTracking = false, + const TargetInstrInfo *TII = nullptr) + : Def(nullptr), DefIdx(0), DefSubReg(DefSubReg), Reg(Reg), + UseAdvancedTracking(UseAdvancedTracking), MRI(MRI), TII(TII) { + if (!TargetRegisterInfo::isPhysicalRegister(Reg)) { + Def = MRI.getVRegDef(Reg); + DefIdx = MRI.def_begin(Reg).getOperandNo(); + } + } + + /// \brief Create a ValueTracker instance for the value defined by + /// the pair \p MI, \p DefIdx. + /// Unlike the other constructor, the value tracker produced by this one + /// may be able to find a new source when the definition is a physical + /// register. + /// This could be useful to rewrite target specific instructions into + /// generic copy instructions. + ValueTracker(const MachineInstr &MI, unsigned DefIdx, unsigned DefSubReg, + const MachineRegisterInfo &MRI, + bool UseAdvancedTracking = false, + const TargetInstrInfo *TII = nullptr) + : Def(&MI), DefIdx(DefIdx), DefSubReg(DefSubReg), + UseAdvancedTracking(UseAdvancedTracking), MRI(MRI), TII(TII) { + assert(DefIdx < Def->getDesc().getNumDefs() && + Def->getOperand(DefIdx).isReg() && "Invalid definition"); + Reg = Def->getOperand(DefIdx).getReg(); + } + + /// \brief Following the use-def chain, get the next available source + /// for the tracked value. + /// \return A ValueTrackerResult containing a set of registers + /// and sub registers with tracked values. A ValueTrackerResult with + /// an empty set of registers means no source was found. + ValueTrackerResult getNextSource(); + + /// \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; } + }; +} + +char PeepholeOptimizer::ID = 0; +char &llvm::PeepholeOptimizerID = PeepholeOptimizer::ID; +INITIALIZE_PASS_BEGIN(PeepholeOptimizer, "peephole-opts", + "Peephole Optimizations", false, false) +INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree) +INITIALIZE_PASS_END(PeepholeOptimizer, "peephole-opts", + "Peephole Optimizations", false, false) + +/// If instruction is a copy-like instruction, i.e. it reads a single register +/// and writes a single register and it does not modify the source, and if the +/// source value is preserved as a sub-register of the result, then replace all +/// reachable uses of the source with the subreg of the result. +/// +/// Do not generate an EXTRACT that is used only in a debug use, as this changes +/// the code. Since this code does not currently share EXTRACTs, just ignore all +/// debug uses. +bool PeepholeOptimizer:: +optimizeExtInstr(MachineInstr *MI, MachineBasicBlock *MBB, + SmallPtrSetImpl<MachineInstr*> &LocalMIs) { + unsigned SrcReg, DstReg, SubIdx; + if (!TII->isCoalescableExtInstr(*MI, SrcReg, DstReg, SubIdx)) + return false; + + if (TargetRegisterInfo::isPhysicalRegister(DstReg) || + TargetRegisterInfo::isPhysicalRegister(SrcReg)) + return false; + + if (MRI->hasOneNonDBGUse(SrcReg)) + // No other uses. + return false; + + // Ensure DstReg can get a register class that actually supports + // sub-registers. Don't change the class until we commit. + const TargetRegisterClass *DstRC = MRI->getRegClass(DstReg); + DstRC = TRI->getSubClassWithSubReg(DstRC, SubIdx); + if (!DstRC) + return false; + + // The ext instr may be operating on a sub-register of SrcReg as well. + // PPC::EXTSW is a 32 -> 64-bit sign extension, but it reads a 64-bit + // register. + // If UseSrcSubIdx is Set, SubIdx also applies to SrcReg, and only uses of + // SrcReg:SubIdx should be replaced. + bool UseSrcSubIdx = + TRI->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 (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; + + // Uses that the result of the instruction can reach. + SmallVector<MachineOperand*, 8> ExtendedUses; + + bool ExtendLife = true; + for (MachineOperand &UseMO : MRI->use_nodbg_operands(SrcReg)) { + MachineInstr *UseMI = UseMO.getParent(); + if (UseMI == MI) + continue; + + if (UseMI->isPHI()) { + ExtendLife = false; + continue; + } + + // Only accept uses of SrcReg:SubIdx. + if (UseSrcSubIdx && UseMO.getSubReg() != SubIdx) + continue; + + // It's an error to translate this: + // + // %reg1025 = <sext> %reg1024 + // ... + // %reg1026 = SUBREG_TO_REG 0, %reg1024, 4 + // + // into this: + // + // %reg1025 = <sext> %reg1024 + // ... + // %reg1027 = COPY %reg1025:4 + // %reg1026 = SUBREG_TO_REG 0, %reg1027, 4 + // + // The problem here is that SUBREG_TO_REG is there to assert that an + // implicit zext occurs. It doesn't insert a zext instruction. If we allow + // the COPY here, it will give us the value after the <sext>, not the + // original value of %reg1024 before <sext>. + if (UseMI->getOpcode() == TargetOpcode::SUBREG_TO_REG) + continue; + + MachineBasicBlock *UseMBB = UseMI->getParent(); + if (UseMBB == MBB) { + // Local uses that come after the extension. + if (!LocalMIs.count(UseMI)) + Uses.push_back(&UseMO); + } else if (ReachedBBs.count(UseMBB)) { + // Non-local uses where the result of the extension is used. Always + // replace these unless it's a PHI. + Uses.push_back(&UseMO); + } else if (Aggressive && DT->dominates(MBB, UseMBB)) { + // We may want to extend the live range of the extension result in order + // to replace these uses. + ExtendedUses.push_back(&UseMO); + } else { + // Both will be live out of the def MBB anyway. Don't extend live range of + // the extension result. + ExtendLife = false; + break; + } + } + + if (ExtendLife && !ExtendedUses.empty()) + // Extend the liveness of the extension result. + Uses.append(ExtendedUses.begin(), ExtendedUses.end()); + + // Now replace all uses. + bool Changed = false; + if (!Uses.empty()) { + SmallPtrSet<MachineBasicBlock*, 4> PHIBBs; + + // 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 (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) { + MachineOperand *UseMO = Uses[i]; + MachineInstr *UseMI = UseMO->getParent(); + MachineBasicBlock *UseMBB = UseMI->getParent(); + if (PHIBBs.count(UseMBB)) + continue; + + // About to add uses of DstReg, clear DstReg's kill flags. + if (!Changed) { + MRI->clearKillFlags(DstReg); + MRI->constrainRegClass(DstReg, DstRC); + } + + unsigned NewVR = MRI->createVirtualRegister(RC); + MachineInstr *Copy = BuildMI(*UseMBB, UseMI, UseMI->getDebugLoc(), + TII->get(TargetOpcode::COPY), NewVR) + .addReg(DstReg, 0, SubIdx); + // SubIdx applies to both SrcReg and DstReg when UseSrcSubIdx is set. + if (UseSrcSubIdx) { + Copy->getOperand(0).setSubReg(SubIdx); + Copy->getOperand(0).setIsUndef(); + } + UseMO->setReg(NewVR); + ++NumReuse; + Changed = true; + } + } + + return Changed; +} + +/// If the instruction is a compare and the previous instruction it's comparing +/// against already sets (or could be modified to set) the same flag as the +/// compare, then we can remove the comparison and use the flag from the +/// previous instruction. +bool PeepholeOptimizer::optimizeCmpInstr(MachineInstr *MI, + MachineBasicBlock *MBB) { + // If this instruction is a comparison against zero and isn't comparing a + // physical register, we can try to optimize it. + unsigned SrcReg, SrcReg2; + int CmpMask, CmpValue; + if (!TII->analyzeCompare(MI, SrcReg, SrcReg2, CmpMask, CmpValue) || + TargetRegisterInfo::isPhysicalRegister(SrcReg) || + (SrcReg2 != 0 && TargetRegisterInfo::isPhysicalRegister(SrcReg2))) + return false; + + // Attempt to optimize the comparison instruction. + if (TII->optimizeCompareInstr(MI, SrcReg, SrcReg2, CmpMask, CmpValue, MRI)) { + ++NumCmps; + return true; + } + + return false; +} + +/// Optimize a select instruction. +bool PeepholeOptimizer::optimizeSelect(MachineInstr *MI, + SmallPtrSetImpl<MachineInstr *> &LocalMIs) { + unsigned TrueOp = 0; + unsigned FalseOp = 0; + bool Optimizable = false; + SmallVector<MachineOperand, 4> Cond; + if (TII->analyzeSelect(MI, Cond, TrueOp, FalseOp, Optimizable)) + return false; + if (!Optimizable) + return false; + if (!TII->optimizeSelect(MI, LocalMIs)) + return false; + MI->eraseFromParent(); + ++NumSelects; + return true; +} + +/// \brief Check if a simpler conditional branch can be +// generated +bool PeepholeOptimizer::optimizeCondBranch(MachineInstr *MI) { + return TII->optimizeCondBranch(MI); +} + +/// \brief Try to find the next source that share the same register file +/// for the value defined by \p Reg and \p SubReg. +/// When true is returned, the \p RewriteMap can be used by the client to +/// retrieve all Def -> Use along the way up to the next source. Any found +/// Use that is not itself a key for another entry, is the next source to +/// use. During the search for the next source, multiple sources can be found +/// given multiple incoming sources of a PHI instruction. In this case, we +/// look in each PHI source for the next source; all found next sources must +/// share the same register file as \p Reg and \p SubReg. The client should +/// then be capable to rewrite all intermediate PHIs to get the next source. +/// \return False if no alternative sources are available. True otherwise. +bool PeepholeOptimizer::findNextSource(unsigned Reg, unsigned SubReg, + RewriteMapTy &RewriteMap) { + // Do not try to find a new source for a physical register. + // So far we do not have any motivating example for doing that. + // Thus, instead of maintaining untested code, we will revisit that if + // that changes at some point. + if (TargetRegisterInfo::isPhysicalRegister(Reg)) + return false; + const TargetRegisterClass *DefRC = MRI->getRegClass(Reg); + + SmallVector<TargetInstrInfo::RegSubRegPair, 4> SrcToLook; + TargetInstrInfo::RegSubRegPair CurSrcPair(Reg, SubReg); + SrcToLook.push_back(CurSrcPair); + + unsigned PHICount = 0; + while (!SrcToLook.empty() && PHICount < RewritePHILimit) { + TargetInstrInfo::RegSubRegPair Pair = SrcToLook.pop_back_val(); + // As explained above, do not handle physical registers + if (TargetRegisterInfo::isPhysicalRegister(Pair.Reg)) + return false; + + CurSrcPair = Pair; + ValueTracker ValTracker(CurSrcPair.Reg, CurSrcPair.SubReg, *MRI, + !DisableAdvCopyOpt, TII); + ValueTrackerResult Res; + bool ShouldRewrite = false; + + do { + // Follow the chain of copies until we reach the top of the use-def chain + // or find a more suitable source. + Res = ValTracker.getNextSource(); + if (!Res.isValid()) + break; + + // Insert the Def -> Use entry for the recently found source. + ValueTrackerResult CurSrcRes = RewriteMap.lookup(CurSrcPair); + if (CurSrcRes.isValid()) { + assert(CurSrcRes == Res && "ValueTrackerResult found must match"); + // An existent entry with multiple sources is a PHI cycle we must avoid. + // Otherwise it's an entry with a valid next source we already found. + if (CurSrcRes.getNumSources() > 1) { + DEBUG(dbgs() << "findNextSource: found PHI cycle, aborting...\n"); + return false; + } + break; + } + RewriteMap.insert(std::make_pair(CurSrcPair, Res)); + + // ValueTrackerResult usually have one source unless it's the result from + // a PHI instruction. Add the found PHI edges to be looked up further. + unsigned NumSrcs = Res.getNumSources(); + if (NumSrcs > 1) { + PHICount++; + for (unsigned i = 0; i < NumSrcs; ++i) + SrcToLook.push_back(TargetInstrInfo::RegSubRegPair( + Res.getSrcReg(i), Res.getSrcSubReg(i))); + break; + } + + CurSrcPair.Reg = Res.getSrcReg(0); + CurSrcPair.SubReg = Res.getSrcSubReg(0); + // 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 aren't redefine before the related use. + if (TargetRegisterInfo::isPhysicalRegister(CurSrcPair.Reg)) + return false; + + const TargetRegisterClass *SrcRC = MRI->getRegClass(CurSrcPair.Reg); + ShouldRewrite = TRI->shouldRewriteCopySrc(DefRC, SubReg, SrcRC, + CurSrcPair.SubReg); + } while (!ShouldRewrite); + + // Continue looking for new sources... + if (Res.isValid()) + continue; + + // Do not continue searching for a new source if the there's at least + // one use-def which cannot be rewritten. + if (!ShouldRewrite) + return false; + } + + if (PHICount >= RewritePHILimit) { + DEBUG(dbgs() << "findNextSource: PHI limit reached\n"); + return false; + } + + // If we did not find a more suitable source, there is nothing to optimize. + return CurSrcPair.Reg != Reg; +} + +/// \brief Insert a PHI instruction with incoming edges \p SrcRegs that are +/// guaranteed to have the same register class. This is necessary whenever we +/// successfully traverse a PHI instruction and find suitable sources coming +/// from its edges. By inserting a new PHI, we provide a rewritten PHI def +/// suitable to be used in a new COPY instruction. +static MachineInstr * +insertPHI(MachineRegisterInfo *MRI, const TargetInstrInfo *TII, + const SmallVectorImpl<TargetInstrInfo::RegSubRegPair> &SrcRegs, + MachineInstr *OrigPHI) { + assert(!SrcRegs.empty() && "No sources to create a PHI instruction?"); + + const TargetRegisterClass *NewRC = MRI->getRegClass(SrcRegs[0].Reg); + unsigned NewVR = MRI->createVirtualRegister(NewRC); + MachineBasicBlock *MBB = OrigPHI->getParent(); + MachineInstrBuilder MIB = BuildMI(*MBB, OrigPHI, OrigPHI->getDebugLoc(), + TII->get(TargetOpcode::PHI), NewVR); + + unsigned MBBOpIdx = 2; + for (auto RegPair : SrcRegs) { + MIB.addReg(RegPair.Reg, 0, RegPair.SubReg); + MIB.addMBB(OrigPHI->getOperand(MBBOpIdx).getMBB()); + // Since we're extended the lifetime of RegPair.Reg, clear the + // kill flags to account for that and make RegPair.Reg reaches + // the new PHI. + MRI->clearKillFlags(RegPair.Reg); + MBBOpIdx += 2; + } + + return MIB; +} + +namespace { +/// \brief Helper class to rewrite the arguments of a copy-like instruction. +class CopyRewriter { +protected: + /// The copy-like instruction. + MachineInstr &CopyLike; + /// The index of the source being rewritten. + unsigned CurrentSrcIdx; + +public: + CopyRewriter(MachineInstr &MI) : CopyLike(MI), CurrentSrcIdx(0) {} + + virtual ~CopyRewriter() {} + + /// \brief Get the next rewritable source (SrcReg, SrcSubReg) and + /// the related value that it affects (TrackReg, TrackSubReg). + /// A source is considered rewritable if its register class and the + /// register class of the related TrackReg may not be register + /// coalescer friendly. In other words, given a copy-like instruction + /// not all the arguments may be returned at rewritable source, since + /// some arguments are none to be register coalescer friendly. + /// + /// Each call of this method moves the current source to the next + /// rewritable source. + /// For instance, let CopyLike be the instruction to rewrite. + /// CopyLike has one definition and one source: + /// dst.dstSubIdx = CopyLike src.srcSubIdx. + /// + /// The first call will give the first rewritable source, i.e., + /// the only source this instruction has: + /// (SrcReg, SrcSubReg) = (src, srcSubIdx). + /// This source defines the whole definition, i.e., + /// (TrackReg, TrackSubReg) = (dst, dstSubIdx). + /// + /// The second and subsequent calls will return false, as there is only one + /// rewritable source. + /// + /// \return True if a rewritable source has been found, false otherwise. + /// The output arguments are valid if and only if true is returned. + virtual bool getNextRewritableSource(unsigned &SrcReg, unsigned &SrcSubReg, + unsigned &TrackReg, + unsigned &TrackSubReg) { + // If CurrentSrcIdx == 1, this means this function has already been called + // once. CopyLike has one definition and one argument, thus, there is + // nothing else to rewrite. + if (!CopyLike.isCopy() || CurrentSrcIdx == 1) + return false; + // This is the first call to getNextRewritableSource. + // Move the CurrentSrcIdx to remember that we made that call. + CurrentSrcIdx = 1; + // The rewritable source is the argument. + const MachineOperand &MOSrc = CopyLike.getOperand(1); + SrcReg = MOSrc.getReg(); + SrcSubReg = MOSrc.getSubReg(); + // What we track are the alternative sources of the definition. + const MachineOperand &MODef = CopyLike.getOperand(0); + TrackReg = MODef.getReg(); + TrackSubReg = MODef.getSubReg(); + return true; + } + + /// \brief Rewrite the current source with \p NewReg and \p NewSubReg + /// if possible. + /// \return True if the rewriting was possible, false otherwise. + virtual bool RewriteCurrentSource(unsigned NewReg, unsigned NewSubReg) { + if (!CopyLike.isCopy() || CurrentSrcIdx != 1) + return false; + MachineOperand &MOSrc = CopyLike.getOperand(CurrentSrcIdx); + MOSrc.setReg(NewReg); + MOSrc.setSubReg(NewSubReg); + return true; + } + + /// \brief Given a \p Def.Reg and Def.SubReg pair, use \p RewriteMap to find + /// the new source to use for rewrite. If \p HandleMultipleSources is true and + /// multiple sources for a given \p Def are found along the way, we found a + /// PHI instructions that needs to be rewritten. + /// TODO: HandleMultipleSources should be removed once we test PHI handling + /// with coalescable copies. + TargetInstrInfo::RegSubRegPair + getNewSource(MachineRegisterInfo *MRI, const TargetInstrInfo *TII, + TargetInstrInfo::RegSubRegPair Def, + PeepholeOptimizer::RewriteMapTy &RewriteMap, + bool HandleMultipleSources = true) { + + TargetInstrInfo::RegSubRegPair LookupSrc(Def.Reg, Def.SubReg); + do { + ValueTrackerResult Res = RewriteMap.lookup(LookupSrc); + // If there are no entries on the map, LookupSrc is the new source. + if (!Res.isValid()) + return LookupSrc; + + // There's only one source for this definition, keep searching... + unsigned NumSrcs = Res.getNumSources(); + if (NumSrcs == 1) { + LookupSrc.Reg = Res.getSrcReg(0); + LookupSrc.SubReg = Res.getSrcSubReg(0); + continue; + } + + // TODO: Remove once multiple srcs w/ coalescable copies are supported. + if (!HandleMultipleSources) + break; + + // Multiple sources, recurse into each source to find a new source + // for it. Then, rewrite the PHI accordingly to its new edges. + SmallVector<TargetInstrInfo::RegSubRegPair, 4> NewPHISrcs; + for (unsigned i = 0; i < NumSrcs; ++i) { + TargetInstrInfo::RegSubRegPair PHISrc(Res.getSrcReg(i), + Res.getSrcSubReg(i)); + NewPHISrcs.push_back( + getNewSource(MRI, TII, PHISrc, RewriteMap, HandleMultipleSources)); + } + + // Build the new PHI node and return its def register as the new source. + MachineInstr *OrigPHI = const_cast<MachineInstr *>(Res.getInst()); + MachineInstr *NewPHI = insertPHI(MRI, TII, NewPHISrcs, OrigPHI); + DEBUG(dbgs() << "-- getNewSource\n"); + DEBUG(dbgs() << " Replacing: " << *OrigPHI); + DEBUG(dbgs() << " With: " << *NewPHI); + const MachineOperand &MODef = NewPHI->getOperand(0); + return TargetInstrInfo::RegSubRegPair(MODef.getReg(), MODef.getSubReg()); + + } while (1); + + return TargetInstrInfo::RegSubRegPair(0, 0); + } + + /// \brief Rewrite the source found through \p Def, by using the \p RewriteMap + /// and create a new COPY instruction. More info about RewriteMap in + /// PeepholeOptimizer::findNextSource. Right now this is only used to handle + /// Uncoalescable copies, since they are copy like instructions that aren't + /// recognized by the register allocator. + virtual MachineInstr * + RewriteSource(TargetInstrInfo::RegSubRegPair Def, + PeepholeOptimizer::RewriteMapTy &RewriteMap) { + return nullptr; + } +}; + +/// \brief Helper class to rewrite uncoalescable copy like instructions +/// into new COPY (coalescable friendly) instructions. +class UncoalescableRewriter : public CopyRewriter { +protected: + const TargetInstrInfo &TII; + MachineRegisterInfo &MRI; + /// The number of defs in the bitcast + unsigned NumDefs; + +public: + UncoalescableRewriter(MachineInstr &MI, const TargetInstrInfo &TII, + MachineRegisterInfo &MRI) + : CopyRewriter(MI), TII(TII), MRI(MRI) { + NumDefs = MI.getDesc().getNumDefs(); + } + + /// \brief Get the next rewritable def source (TrackReg, TrackSubReg) + /// All such sources need to be considered rewritable in order to + /// rewrite a uncoalescable copy-like instruction. This method return + /// each definition that must be checked if rewritable. + /// + bool getNextRewritableSource(unsigned &SrcReg, unsigned &SrcSubReg, + unsigned &TrackReg, + unsigned &TrackSubReg) override { + // Find the next non-dead definition and continue from there. + if (CurrentSrcIdx == NumDefs) + return false; + + while (CopyLike.getOperand(CurrentSrcIdx).isDead()) { + ++CurrentSrcIdx; + if (CurrentSrcIdx == NumDefs) + return false; + } + + // What we track are the alternative sources of the definition. + const MachineOperand &MODef = CopyLike.getOperand(CurrentSrcIdx); + TrackReg = MODef.getReg(); + TrackSubReg = MODef.getSubReg(); + + CurrentSrcIdx++; + return true; + } + + /// \brief Rewrite the source found through \p Def, by using the \p RewriteMap + /// and create a new COPY instruction. More info about RewriteMap in + /// PeepholeOptimizer::findNextSource. Right now this is only used to handle + /// Uncoalescable copies, since they are copy like instructions that aren't + /// recognized by the register allocator. + MachineInstr * + RewriteSource(TargetInstrInfo::RegSubRegPair Def, + PeepholeOptimizer::RewriteMapTy &RewriteMap) override { + assert(!TargetRegisterInfo::isPhysicalRegister(Def.Reg) && + "We do not rewrite physical registers"); + + // Find the new source to use in the COPY rewrite. + TargetInstrInfo::RegSubRegPair NewSrc = + getNewSource(&MRI, &TII, Def, RewriteMap); + + // Insert the COPY. + const TargetRegisterClass *DefRC = MRI.getRegClass(Def.Reg); + unsigned NewVR = MRI.createVirtualRegister(DefRC); + + MachineInstr *NewCopy = + BuildMI(*CopyLike.getParent(), &CopyLike, CopyLike.getDebugLoc(), + TII.get(TargetOpcode::COPY), NewVR) + .addReg(NewSrc.Reg, 0, NewSrc.SubReg); + + NewCopy->getOperand(0).setSubReg(Def.SubReg); + if (Def.SubReg) + NewCopy->getOperand(0).setIsUndef(); + + DEBUG(dbgs() << "-- RewriteSource\n"); + DEBUG(dbgs() << " Replacing: " << CopyLike); + DEBUG(dbgs() << " With: " << *NewCopy); + MRI.replaceRegWith(Def.Reg, NewVR); + MRI.clearKillFlags(NewVR); + + // We extended the lifetime of NewSrc.Reg, clear the kill flags to + // account for that. + MRI.clearKillFlags(NewSrc.Reg); + + return NewCopy; + } +}; + +/// \brief Specialized rewriter for INSERT_SUBREG instruction. +class InsertSubregRewriter : public CopyRewriter { +public: + InsertSubregRewriter(MachineInstr &MI) : CopyRewriter(MI) { + assert(MI.isInsertSubreg() && "Invalid instruction"); + } + + /// \brief See CopyRewriter::getNextRewritableSource. + /// Here CopyLike has the following form: + /// dst = INSERT_SUBREG Src1, Src2.src2SubIdx, subIdx. + /// Src1 has the same register class has dst, hence, there is + /// nothing to rewrite. + /// Src2.src2SubIdx, may not be register coalescer friendly. + /// Therefore, the first call to this method returns: + /// (SrcReg, SrcSubReg) = (Src2, src2SubIdx). + /// (TrackReg, TrackSubReg) = (dst, subIdx). + /// + /// Subsequence calls will return false. + bool getNextRewritableSource(unsigned &SrcReg, unsigned &SrcSubReg, + unsigned &TrackReg, + unsigned &TrackSubReg) override { + // If we already get the only source we can rewrite, return false. + if (CurrentSrcIdx == 2) + return false; + // We are looking at v2 = INSERT_SUBREG v0, v1, sub0. + CurrentSrcIdx = 2; + const MachineOperand &MOInsertedReg = CopyLike.getOperand(2); + SrcReg = MOInsertedReg.getReg(); + SrcSubReg = MOInsertedReg.getSubReg(); + const MachineOperand &MODef = CopyLike.getOperand(0); + + // We want to track something that is compatible with the + // partial definition. + TrackReg = MODef.getReg(); + if (MODef.getSubReg()) + // Bail if we have to compose sub-register indices. + return false; + TrackSubReg = (unsigned)CopyLike.getOperand(3).getImm(); + return true; + } + bool RewriteCurrentSource(unsigned NewReg, unsigned NewSubReg) override { + if (CurrentSrcIdx != 2) + return false; + // We are rewriting the inserted reg. + MachineOperand &MO = CopyLike.getOperand(CurrentSrcIdx); + MO.setReg(NewReg); + MO.setSubReg(NewSubReg); + return true; + } +}; + +/// \brief Specialized rewriter for EXTRACT_SUBREG instruction. +class ExtractSubregRewriter : public CopyRewriter { + const TargetInstrInfo &TII; + +public: + ExtractSubregRewriter(MachineInstr &MI, const TargetInstrInfo &TII) + : CopyRewriter(MI), TII(TII) { + assert(MI.isExtractSubreg() && "Invalid instruction"); + } + + /// \brief See CopyRewriter::getNextRewritableSource. + /// Here CopyLike has the following form: + /// dst.dstSubIdx = EXTRACT_SUBREG Src, subIdx. + /// There is only one rewritable source: Src.subIdx, + /// which defines dst.dstSubIdx. + bool getNextRewritableSource(unsigned &SrcReg, unsigned &SrcSubReg, + unsigned &TrackReg, + unsigned &TrackSubReg) override { + // If we already get the only source we can rewrite, return false. + if (CurrentSrcIdx == 1) + return false; + // We are looking at v1 = EXTRACT_SUBREG v0, sub0. + CurrentSrcIdx = 1; + const MachineOperand &MOExtractedReg = CopyLike.getOperand(1); + SrcReg = MOExtractedReg.getReg(); + // If we have to compose sub-register indices, bail out. + if (MOExtractedReg.getSubReg()) + return false; + + SrcSubReg = CopyLike.getOperand(2).getImm(); + + // We want to track something that is compatible with the definition. + const MachineOperand &MODef = CopyLike.getOperand(0); + TrackReg = MODef.getReg(); + TrackSubReg = MODef.getSubReg(); + return true; + } + + bool RewriteCurrentSource(unsigned NewReg, unsigned NewSubReg) override { + // The only source we can rewrite is the input register. + if (CurrentSrcIdx != 1) + return false; + + CopyLike.getOperand(CurrentSrcIdx).setReg(NewReg); + + // If we find a source that does not require to extract something, + // rewrite the operation with a copy. + if (!NewSubReg) { + // Move the current index to an invalid position. + // We do not want another call to this method to be able + // to do any change. + CurrentSrcIdx = -1; + // Rewrite the operation as a COPY. + // Get rid of the sub-register index. + CopyLike.RemoveOperand(2); + // Morph the operation into a COPY. + CopyLike.setDesc(TII.get(TargetOpcode::COPY)); + return true; + } + CopyLike.getOperand(CurrentSrcIdx + 1).setImm(NewSubReg); + return true; + } +}; + +/// \brief Specialized rewriter for REG_SEQUENCE instruction. +class RegSequenceRewriter : public CopyRewriter { +public: + RegSequenceRewriter(MachineInstr &MI) : CopyRewriter(MI) { + assert(MI.isRegSequence() && "Invalid instruction"); + } + + /// \brief See CopyRewriter::getNextRewritableSource. + /// Here CopyLike has the following form: + /// dst = REG_SEQUENCE Src1.src1SubIdx, subIdx1, Src2.src2SubIdx, subIdx2. + /// Each call will return a different source, walking all the available + /// source. + /// + /// The first call returns: + /// (SrcReg, SrcSubReg) = (Src1, src1SubIdx). + /// (TrackReg, TrackSubReg) = (dst, subIdx1). + /// + /// The second call returns: + /// (SrcReg, SrcSubReg) = (Src2, src2SubIdx). + /// (TrackReg, TrackSubReg) = (dst, subIdx2). + /// + /// And so on, until all the sources have been traversed, then + /// it returns false. + bool getNextRewritableSource(unsigned &SrcReg, unsigned &SrcSubReg, + unsigned &TrackReg, + unsigned &TrackSubReg) override { + // We are looking at v0 = REG_SEQUENCE v1, sub1, v2, sub2, etc. + + // If this is the first call, move to the first argument. + if (CurrentSrcIdx == 0) { + CurrentSrcIdx = 1; + } else { + // Otherwise, move to the next argument and check that it is valid. + CurrentSrcIdx += 2; + if (CurrentSrcIdx >= CopyLike.getNumOperands()) + return false; + } + const MachineOperand &MOInsertedReg = CopyLike.getOperand(CurrentSrcIdx); + SrcReg = MOInsertedReg.getReg(); + // If we have to compose sub-register indices, bail out. + if ((SrcSubReg = MOInsertedReg.getSubReg())) + return false; + + // We want to track something that is compatible with the related + // partial definition. + TrackSubReg = CopyLike.getOperand(CurrentSrcIdx + 1).getImm(); + + const MachineOperand &MODef = CopyLike.getOperand(0); + TrackReg = MODef.getReg(); + // If we have to compose sub-registers, bail. + return MODef.getSubReg() == 0; + } + + bool RewriteCurrentSource(unsigned NewReg, unsigned NewSubReg) override { + // We cannot rewrite out of bound operands. + // Moreover, rewritable sources are at odd positions. + if ((CurrentSrcIdx & 1) != 1 || CurrentSrcIdx > CopyLike.getNumOperands()) + return false; + + MachineOperand &MO = CopyLike.getOperand(CurrentSrcIdx); + MO.setReg(NewReg); + MO.setSubReg(NewSubReg); + return true; + } +}; +} // End namespace. + +/// \brief Get the appropriated CopyRewriter for \p MI. +/// \return A pointer to a dynamically allocated CopyRewriter or nullptr +/// if no rewriter works for \p MI. +static CopyRewriter *getCopyRewriter(MachineInstr &MI, + const TargetInstrInfo &TII, + MachineRegisterInfo &MRI) { + // Handle uncoalescable copy-like instructions. + if (MI.isBitcast() || (MI.isRegSequenceLike() || MI.isInsertSubregLike() || + MI.isExtractSubregLike())) + return new UncoalescableRewriter(MI, TII, MRI); + + switch (MI.getOpcode()) { + default: + return nullptr; + case TargetOpcode::COPY: + return new CopyRewriter(MI); + case TargetOpcode::INSERT_SUBREG: + return new InsertSubregRewriter(MI); + case TargetOpcode::EXTRACT_SUBREG: + return new ExtractSubregRewriter(MI, TII); + case TargetOpcode::REG_SEQUENCE: + return new RegSequenceRewriter(MI); + } + llvm_unreachable(nullptr); +} + +/// \brief Optimize generic copy instructions to avoid cross +/// register bank copy. The optimization looks through a chain of +/// copies and tries to find a source that has a compatible register +/// class. +/// Two register classes are considered to be compatible if they share +/// the same register bank. +/// New copies issued by this optimization are register allocator +/// friendly. This optimization does not remove any copy as it may +/// overconstrain the register allocator, but replaces some operands +/// when possible. +/// \pre isCoalescableCopy(*MI) is true. +/// \return True, when \p MI has been rewritten. False otherwise. +bool PeepholeOptimizer::optimizeCoalescableCopy(MachineInstr *MI) { + assert(MI && isCoalescableCopy(*MI) && "Invalid argument"); + assert(MI->getDesc().getNumDefs() == 1 && + "Coalescer can understand multiple defs?!"); + const MachineOperand &MODef = MI->getOperand(0); + // Do not rewrite physical definitions. + if (TargetRegisterInfo::isPhysicalRegister(MODef.getReg())) + return false; + + bool Changed = false; + // Get the right rewriter for the current copy. + std::unique_ptr<CopyRewriter> CpyRewriter(getCopyRewriter(*MI, *TII, *MRI)); + // If none exists, bail out. + if (!CpyRewriter) + return false; + // Rewrite each rewritable source. + unsigned SrcReg, SrcSubReg, TrackReg, TrackSubReg; + while (CpyRewriter->getNextRewritableSource(SrcReg, SrcSubReg, TrackReg, + TrackSubReg)) { + // Keep track of PHI nodes and its incoming edges when looking for sources. + RewriteMapTy RewriteMap; + // Try to find a more suitable source. If we failed to do so, or get the + // actual source, move to the next source. + if (!findNextSource(TrackReg, TrackSubReg, RewriteMap)) + continue; + + // Get the new source to rewrite. TODO: Only enable handling of multiple + // sources (PHIs) once we have a motivating example and testcases for it. + TargetInstrInfo::RegSubRegPair TrackPair(TrackReg, TrackSubReg); + TargetInstrInfo::RegSubRegPair NewSrc = CpyRewriter->getNewSource( + MRI, TII, TrackPair, RewriteMap, false /* multiple sources */); + if (SrcReg == NewSrc.Reg || NewSrc.Reg == 0) + continue; + + // Rewrite source. + if (CpyRewriter->RewriteCurrentSource(NewSrc.Reg, NewSrc.SubReg)) { + // We may have extended the live-range of NewSrc, account for that. + MRI->clearKillFlags(NewSrc.Reg); + Changed = true; + } + } + // TODO: We could have a clean-up method to tidy the instruction. + // E.g., v0 = INSERT_SUBREG v1, v1.sub0, sub0 + // => v0 = COPY v1 + // Currently we haven't seen motivating example for that and we + // want to avoid untested code. + NumRewrittenCopies += Changed; + return Changed; +} + +/// \brief Optimize copy-like instructions to create +/// register coalescer friendly instruction. +/// The optimization tries to kill-off the \p MI by looking +/// through a chain of copies to find a source that has a compatible +/// register class. +/// If such a source is found, it replace \p MI by a generic COPY +/// operation. +/// \pre isUncoalescableCopy(*MI) is true. +/// \return True, when \p MI has been optimized. In that case, \p MI has +/// been removed from its parent. +/// All COPY instructions created, are inserted in \p LocalMIs. +bool PeepholeOptimizer::optimizeUncoalescableCopy( + MachineInstr *MI, SmallPtrSetImpl<MachineInstr *> &LocalMIs) { + assert(MI && isUncoalescableCopy(*MI) && "Invalid argument"); + + // Check if we can rewrite all the values defined by this instruction. + SmallVector<TargetInstrInfo::RegSubRegPair, 4> RewritePairs; + // Get the right rewriter for the current copy. + std::unique_ptr<CopyRewriter> CpyRewriter(getCopyRewriter(*MI, *TII, *MRI)); + // If none exists, bail out. + if (!CpyRewriter) + return false; + + // Rewrite each rewritable source by generating new COPYs. This works + // differently from optimizeCoalescableCopy since it first makes sure that all + // definitions can be rewritten. + RewriteMapTy RewriteMap; + unsigned Reg, SubReg, CopyDefReg, CopyDefSubReg; + while (CpyRewriter->getNextRewritableSource(Reg, SubReg, CopyDefReg, + CopyDefSubReg)) { + // If a physical register is here, this is probably for a good reason. + // Do not rewrite that. + if (TargetRegisterInfo::isPhysicalRegister(CopyDefReg)) + return false; + + // If we do not know how to rewrite this definition, there is no point + // in trying to kill this instruction. + TargetInstrInfo::RegSubRegPair Def(CopyDefReg, CopyDefSubReg); + if (!findNextSource(Def.Reg, Def.SubReg, RewriteMap)) + return false; + + RewritePairs.push_back(Def); + } + + // The change is possible for all defs, do it. + for (const auto &Def : RewritePairs) { + // Rewrite the "copy" in a way the register coalescer understands. + MachineInstr *NewCopy = CpyRewriter->RewriteSource(Def, RewriteMap); + assert(NewCopy && "Should be able to always generate a new copy"); + LocalMIs.insert(NewCopy); + } + + // MI is now dead. + MI->eraseFromParent(); + ++NumUncoalescableCopies; + return true; +} + +/// 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, SmallSet<unsigned, 16> &FoldAsLoadDefCandidates) { + if (!MI->canFoldAsLoad() || !MI->mayLoad()) + return false; + const MCInstrDesc &MCID = MI->getDesc(); + if (MCID.getNumDefs() != 1) + return false; + + unsigned Reg = MI->getOperand(0).getReg(); + // 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->hasOneNonDBGUse(Reg)) { + FoldAsLoadDefCandidates.insert(Reg); + return true; + } + return false; +} + +bool PeepholeOptimizer::isMoveImmediate( + MachineInstr *MI, SmallSet<unsigned, 4> &ImmDefRegs, + DenseMap<unsigned, MachineInstr *> &ImmDefMIs) { + const MCInstrDesc &MCID = MI->getDesc(); + if (!MI->isMoveImmediate()) + return false; + if (MCID.getNumDefs() != 1) + return false; + unsigned Reg = MI->getOperand(0).getReg(); + if (TargetRegisterInfo::isVirtualRegister(Reg)) { + ImmDefMIs.insert(std::make_pair(Reg, MI)); + ImmDefRegs.insert(Reg); + return true; + } + + return false; +} + +/// Try folding register operands that are defined by move immediate +/// instructions, i.e. a trivial constant folding optimization, if +/// and only if the def and use are in the same BB. +bool PeepholeOptimizer::foldImmediate( + MachineInstr *MI, MachineBasicBlock *MBB, SmallSet<unsigned, 4> &ImmDefRegs, + DenseMap<unsigned, MachineInstr *> &ImmDefMIs) { + for (unsigned i = 0, e = MI->getDesc().getNumOperands(); i != e; ++i) { + MachineOperand &MO = MI->getOperand(i); + if (!MO.isReg() || MO.isDef()) + continue; + // Ignore dead implicit defs. + if (MO.isImplicit() && MO.isDead()) + continue; + unsigned Reg = MO.getReg(); + if (!TargetRegisterInfo::isVirtualRegister(Reg)) + continue; + if (ImmDefRegs.count(Reg) == 0) + continue; + DenseMap<unsigned, MachineInstr*>::iterator II = ImmDefMIs.find(Reg); + assert(II != ImmDefMIs.end() && "couldn't find immediate definition"); + if (TII->FoldImmediate(MI, II->second, Reg, MRI)) { + ++NumImmFold; + return true; + } + } + return false; +} + +// FIXME: This is very simple and misses some cases which should be handled when +// motivating examples are found. +// +// The copy rewriting logic should look at uses as well as defs and be able to +// eliminate copies across blocks. +// +// Later copies that are subregister extracts will also not be eliminated since +// only the first copy is considered. +// +// e.g. +// %vreg1 = COPY %vreg0 +// %vreg2 = COPY %vreg0:sub1 +// +// Should replace %vreg2 uses with %vreg1:sub1 +bool PeepholeOptimizer::foldRedundantCopy( + MachineInstr *MI, SmallSet<unsigned, 4> &CopySrcRegs, + DenseMap<unsigned, MachineInstr *> &CopyMIs) { + assert(MI->isCopy() && "expected a COPY machine instruction"); + + unsigned SrcReg = MI->getOperand(1).getReg(); + if (!TargetRegisterInfo::isVirtualRegister(SrcReg)) + return false; + + unsigned DstReg = MI->getOperand(0).getReg(); + if (!TargetRegisterInfo::isVirtualRegister(DstReg)) + return false; + + if (CopySrcRegs.insert(SrcReg).second) { + // First copy of this reg seen. + CopyMIs.insert(std::make_pair(SrcReg, MI)); + return false; + } + + MachineInstr *PrevCopy = CopyMIs.find(SrcReg)->second; + + unsigned SrcSubReg = MI->getOperand(1).getSubReg(); + unsigned PrevSrcSubReg = PrevCopy->getOperand(1).getSubReg(); + + // Can't replace different subregister extracts. + if (SrcSubReg != PrevSrcSubReg) + return false; + + unsigned PrevDstReg = PrevCopy->getOperand(0).getReg(); + + // Only replace if the copy register class is the same. + // + // TODO: If we have multiple copies to different register classes, we may want + // to track multiple copies of the same source register. + if (MRI->getRegClass(DstReg) != MRI->getRegClass(PrevDstReg)) + return false; + + MRI->replaceRegWith(DstReg, PrevDstReg); + + // Lifetime of the previous copy has been extended. + MRI->clearKillFlags(PrevDstReg); + return true; +} + +bool PeepholeOptimizer::isNAPhysCopy(unsigned Reg) { + return TargetRegisterInfo::isPhysicalRegister(Reg) && + !MRI->isAllocatable(Reg); +} + +bool PeepholeOptimizer::foldRedundantNAPhysCopy( + MachineInstr *MI, DenseMap<unsigned, MachineInstr *> &NAPhysToVirtMIs) { + assert(MI->isCopy() && "expected a COPY machine instruction"); + + if (DisableNAPhysCopyOpt) + return false; + + unsigned DstReg = MI->getOperand(0).getReg(); + unsigned SrcReg = MI->getOperand(1).getReg(); + if (isNAPhysCopy(SrcReg) && TargetRegisterInfo::isVirtualRegister(DstReg)) { + // %vreg = COPY %PHYSREG + // Avoid using a datastructure which can track multiple live non-allocatable + // phys->virt copies since LLVM doesn't seem to do this. + NAPhysToVirtMIs.insert({SrcReg, MI}); + return false; + } + + if (!(TargetRegisterInfo::isVirtualRegister(SrcReg) && isNAPhysCopy(DstReg))) + return false; + + // %PHYSREG = COPY %vreg + auto PrevCopy = NAPhysToVirtMIs.find(DstReg); + if (PrevCopy == NAPhysToVirtMIs.end()) { + // We can't remove the copy: there was an intervening clobber of the + // non-allocatable physical register after the copy to virtual. + DEBUG(dbgs() << "NAPhysCopy: intervening clobber forbids erasing " << *MI + << '\n'); + return false; + } + + unsigned PrevDstReg = PrevCopy->second->getOperand(0).getReg(); + if (PrevDstReg == SrcReg) { + // Remove the virt->phys copy: we saw the virtual register definition, and + // the non-allocatable physical register's state hasn't changed since then. + DEBUG(dbgs() << "NAPhysCopy: erasing " << *MI << '\n'); + ++NumNAPhysCopies; + return true; + } + + // Potential missed optimization opportunity: we saw a different virtual + // register get a copy of the non-allocatable physical register, and we only + // track one such copy. Avoid getting confused by this new non-allocatable + // physical register definition, and remove it from the tracked copies. + DEBUG(dbgs() << "NAPhysCopy: missed opportunity " << *MI << '\n'); + NAPhysToVirtMIs.erase(PrevCopy); + return false; +} + +bool PeepholeOptimizer::runOnMachineFunction(MachineFunction &MF) { + if (skipOptnoneFunction(*MF.getFunction())) + return false; + + DEBUG(dbgs() << "********** PEEPHOLE OPTIMIZER **********\n"); + DEBUG(dbgs() << "********** Function: " << MF.getName() << '\n'); + + if (DisablePeephole) + return false; + + TII = MF.getSubtarget().getInstrInfo(); + TRI = MF.getSubtarget().getRegisterInfo(); + MRI = &MF.getRegInfo(); + DT = Aggressive ? &getAnalysis<MachineDominatorTree>() : nullptr; + + bool Changed = false; + + for (MachineBasicBlock &MBB : MF) { + bool SeenMoveImm = false; + + // During this forward scan, at some point it needs to answer the question + // "given a pointer to an MI in the current BB, is it located before or + // after the current instruction". + // To perform this, the following set keeps track of the MIs already seen + // during the scan, if a MI is not in the set, it is assumed to be located + // after. Newly created MIs have to be inserted in the set as well. + SmallPtrSet<MachineInstr*, 16> LocalMIs; + SmallSet<unsigned, 4> ImmDefRegs; + DenseMap<unsigned, MachineInstr*> ImmDefMIs; + SmallSet<unsigned, 16> FoldAsLoadDefCandidates; + + // Track when a non-allocatable physical register is copied to a virtual + // register so that useless moves can be removed. + // + // %PHYSREG is the map index; MI is the last valid `%vreg = COPY %PHYSREG` + // without any intervening re-definition of %PHYSREG. + DenseMap<unsigned, MachineInstr *> NAPhysToVirtMIs; + + // Set of virtual registers that are copied from. + SmallSet<unsigned, 4> CopySrcRegs; + DenseMap<unsigned, MachineInstr *> CopySrcMIs; + + for (MachineBasicBlock::iterator MII = MBB.begin(), MIE = MBB.end(); + MII != MIE; ) { + MachineInstr *MI = &*MII; + // We may be erasing MI below, increment MII now. + ++MII; + LocalMIs.insert(MI); + + // Skip debug values. They should not affect this peephole optimization. + if (MI->isDebugValue()) + continue; + + // If we run into an instruction we can't fold across, discard + // the load candidates. + if (MI->isLoadFoldBarrier()) + FoldAsLoadDefCandidates.clear(); + + if (MI->isPosition() || MI->isPHI()) + continue; + + if (!MI->isCopy()) { + for (const auto &Op : MI->operands()) { + // Visit all operands: definitions can be implicit or explicit. + if (Op.isReg()) { + unsigned Reg = Op.getReg(); + if (Op.isDef() && isNAPhysCopy(Reg)) { + const auto &Def = NAPhysToVirtMIs.find(Reg); + if (Def != NAPhysToVirtMIs.end()) { + // A new definition of the non-allocatable physical register + // invalidates previous copies. + DEBUG(dbgs() << "NAPhysCopy: invalidating because of " << *MI + << '\n'); + NAPhysToVirtMIs.erase(Def); + } + } + } else if (Op.isRegMask()) { + const uint32_t *RegMask = Op.getRegMask(); + for (auto &RegMI : NAPhysToVirtMIs) { + unsigned Def = RegMI.first; + if (MachineOperand::clobbersPhysReg(RegMask, Def)) { + DEBUG(dbgs() << "NAPhysCopy: invalidating because of " << *MI + << '\n'); + NAPhysToVirtMIs.erase(Def); + } + } + } + } + } + + if (MI->isImplicitDef() || MI->isKill()) + continue; + + if (MI->isInlineAsm() || MI->hasUnmodeledSideEffects()) { + // Blow away all non-allocatable physical registers knowledge since we + // don't know what's correct anymore. + // + // FIXME: handle explicit asm clobbers. + DEBUG(dbgs() << "NAPhysCopy: blowing away all info due to " << *MI + << '\n'); + NAPhysToVirtMIs.clear(); + continue; + } + + if ((isUncoalescableCopy(*MI) && + optimizeUncoalescableCopy(MI, LocalMIs)) || + (MI->isCompare() && optimizeCmpInstr(MI, &MBB)) || + (MI->isSelect() && optimizeSelect(MI, LocalMIs))) { + // MI is deleted. + LocalMIs.erase(MI); + Changed = true; + continue; + } + + if (MI->isConditionalBranch() && optimizeCondBranch(MI)) { + Changed = true; + continue; + } + + if (isCoalescableCopy(*MI) && optimizeCoalescableCopy(MI)) { + // MI is just rewritten. + Changed = true; + continue; + } + + if (MI->isCopy() && + (foldRedundantCopy(MI, CopySrcRegs, CopySrcMIs) || + foldRedundantNAPhysCopy(MI, NAPhysToVirtMIs))) { + LocalMIs.erase(MI); + MI->eraseFromParent(); + Changed = true; + continue; + } + + if (isMoveImmediate(MI, ImmDefRegs, ImmDefMIs)) { + SeenMoveImm = true; + } else { + Changed |= optimizeExtInstr(MI, &MBB, LocalMIs); + // optimizeExtInstr might have created new instructions after MI + // and before the already incremented MII. Adjust MII so that the + // next iteration sees the new instructions. + MII = MI; + ++MII; + if (SeenMoveImm) + Changed |= foldImmediate(MI, &MBB, ImmDefRegs, ImmDefMIs); + } + + // 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, 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; + } + } + } + } + } + } + + return Changed; +} + +ValueTrackerResult ValueTracker::getNextSourceFromCopy() { + 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->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 subregs yet. + return ValueTrackerResult(); + // Otherwise, we want the whole source. + const MachineOperand &Src = Def->getOperand(1); + return ValueTrackerResult(Src.getReg(), Src.getSubReg()); +} + +ValueTrackerResult ValueTracker::getNextSourceFromBitcast() { + assert(Def->isBitcast() && "Invalid definition"); + + // Bail if there are effects that a plain copy will not expose. + if (Def->hasUnmodeledSideEffects()) + return ValueTrackerResult(); + + // Bitcasts with more than one def are not supported. + if (Def->getDesc().getNumDefs() != 1) + return ValueTrackerResult(); + 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 subregs yet. + return ValueTrackerResult(); + + unsigned SrcIdx = Def->getNumOperands(); + for (unsigned OpIdx = DefIdx + 1, EndOpIdx = SrcIdx; OpIdx != EndOpIdx; + ++OpIdx) { + const MachineOperand &MO = Def->getOperand(OpIdx); + if (!MO.isReg() || !MO.getReg()) + continue; + // Ignore dead implicit defs. + if (MO.isImplicit() && MO.isDead()) + continue; + assert(!MO.isDef() && "We should have skipped all the definitions by now"); + if (SrcIdx != EndOpIdx) + // Multiple sources? + return ValueTrackerResult(); + SrcIdx = OpIdx; + } + const MachineOperand &Src = Def->getOperand(SrcIdx); + return ValueTrackerResult(Src.getReg(), Src.getSubReg()); +} + +ValueTrackerResult ValueTracker::getNextSourceFromRegSequence() { + assert((Def->isRegSequence() || Def->isRegSequenceLike()) && + "Invalid definition"); + + if (Def->getOperand(DefIdx).getSubReg()) + // If we are composing subregs, bail 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 ValueTrackerResult(); + + if (!TII) + // We could handle the REG_SEQUENCE here, but we do not want to + // duplicate the code from the generic TII. + return ValueTrackerResult(); + + SmallVector<TargetInstrInfo::RegSubRegPairAndIdx, 8> RegSeqInputRegs; + if (!TII->getRegSequenceInputs(*Def, DefIdx, RegSeqInputRegs)) + return ValueTrackerResult(); + + // 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 (auto &RegSeqInput : RegSeqInputRegs) { + if (RegSeqInput.SubIdx == DefSubReg) { + if (RegSeqInput.SubReg) + // Bail if we have to compose sub registers. + return ValueTrackerResult(); + + return ValueTrackerResult(RegSeqInput.Reg, RegSeqInput.SubReg); + } + } + + // 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 ValueTrackerResult(); +} + +ValueTrackerResult ValueTracker::getNextSourceFromInsertSubreg() { + assert((Def->isInsertSubreg() || Def->isInsertSubregLike()) && + "Invalid definition"); + + if (Def->getOperand(DefIdx).getSubReg()) + // If we are composing subreg, bail out. + // Same remark as getNextSourceFromRegSequence. + // I.e., this may be turned into an assert. + return ValueTrackerResult(); + + if (!TII) + // We could handle the REG_SEQUENCE here, but we do not want to + // duplicate the code from the generic TII. + return ValueTrackerResult(); + + TargetInstrInfo::RegSubRegPair BaseReg; + TargetInstrInfo::RegSubRegPairAndIdx InsertedReg; + if (!TII->getInsertSubregInputs(*Def, DefIdx, BaseReg, InsertedReg)) + return ValueTrackerResult(); + + // 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 required sub index. + if (InsertedReg.SubIdx == DefSubReg) { + return ValueTrackerResult(InsertedReg.Reg, InsertedReg.SubReg); + } + // #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). + const MachineOperand &MODef = Def->getOperand(DefIdx); + // If the result register (Def) and the base register (v0) do not + // have the same register class or if we have to compose + // subregisters, bail out. + if (MRI.getRegClass(MODef.getReg()) != MRI.getRegClass(BaseReg.Reg) || + BaseReg.SubReg) + return ValueTrackerResult(); + + // Get the TRI and check if the inserted sub-register overlaps with the + // sub-register we are tracking. + const TargetRegisterInfo *TRI = MRI.getTargetRegisterInfo(); + if (!TRI || + (TRI->getSubRegIndexLaneMask(DefSubReg) & + TRI->getSubRegIndexLaneMask(InsertedReg.SubIdx)) != 0) + return ValueTrackerResult(); + // At this point, the value is available in v0 via the same subreg + // we used for Def. + return ValueTrackerResult(BaseReg.Reg, DefSubReg); +} + +ValueTrackerResult ValueTracker::getNextSourceFromExtractSubreg() { + assert((Def->isExtractSubreg() || + Def->isExtractSubregLike()) && "Invalid definition"); + // We are looking at: + // Def = EXTRACT_SUBREG v0, sub0 + + // Bail if we have to compose sub registers. + // Indeed, if DefSubReg != 0, we would have to compose it with sub0. + if (DefSubReg) + return ValueTrackerResult(); + + if (!TII) + // We could handle the EXTRACT_SUBREG here, but we do not want to + // duplicate the code from the generic TII. + return ValueTrackerResult(); + + TargetInstrInfo::RegSubRegPairAndIdx ExtractSubregInputReg; + if (!TII->getExtractSubregInputs(*Def, DefIdx, ExtractSubregInputReg)) + return ValueTrackerResult(); + + // Bail if we have to compose sub registers. + // Likewise, if v0.subreg != 0, we would have to compose v0.subreg with sub0. + if (ExtractSubregInputReg.SubReg) + return ValueTrackerResult(); + // Otherwise, the value is available in the v0.sub0. + return ValueTrackerResult(ExtractSubregInputReg.Reg, + ExtractSubregInputReg.SubIdx); +} + +ValueTrackerResult ValueTracker::getNextSourceFromSubregToReg() { + assert(Def->isSubregToReg() && "Invalid definition"); + // We are looking at: + // Def = SUBREG_TO_REG Imm, v0, sub0 + + // Bail 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 ValueTrackerResult(); + // Bail 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 ValueTrackerResult(); + + return ValueTrackerResult(Def->getOperand(2).getReg(), + Def->getOperand(3).getImm()); +} + +/// \brief Explore each PHI incoming operand and return its sources +ValueTrackerResult ValueTracker::getNextSourceFromPHI() { + assert(Def->isPHI() && "Invalid definition"); + ValueTrackerResult Res; + + // If we look for a different subreg, bail as we do not support composing + // subregs yet. + if (Def->getOperand(0).getSubReg() != DefSubReg) + return ValueTrackerResult(); + + // Return all register sources for PHI instructions. + for (unsigned i = 1, e = Def->getNumOperands(); i < e; i += 2) { + auto &MO = Def->getOperand(i); + assert(MO.isReg() && "Invalid PHI instruction"); + Res.addSource(MO.getReg(), MO.getSubReg()); + } + + return Res; +} + +ValueTrackerResult ValueTracker::getNextSourceImpl() { + 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(); + if (Def->isBitcast()) + return getNextSourceFromBitcast(); + // All the remaining cases involve "complex" instructions. + // Bail if we did not ask for the advanced tracking. + if (!UseAdvancedTracking) + return ValueTrackerResult(); + if (Def->isRegSequence() || Def->isRegSequenceLike()) + return getNextSourceFromRegSequence(); + if (Def->isInsertSubreg() || Def->isInsertSubregLike()) + return getNextSourceFromInsertSubreg(); + if (Def->isExtractSubreg() || Def->isExtractSubregLike()) + return getNextSourceFromExtractSubreg(); + if (Def->isSubregToReg()) + return getNextSourceFromSubregToReg(); + if (Def->isPHI()) + return getNextSourceFromPHI(); + return ValueTrackerResult(); +} + +ValueTrackerResult ValueTracker::getNextSource() { + // If we reach a point where we cannot move up in the use-def chain, + // there is nothing we can get. + if (!Def) + return ValueTrackerResult(); + + ValueTrackerResult Res = getNextSourceImpl(); + if (Res.isValid()) { + // Update definition, definition index, and subregister for the + // next call of getNextSource. + // Update the current register. + bool OneRegSrc = Res.getNumSources() == 1; + if (OneRegSrc) + Reg = Res.getSrcReg(0); + // Update the result before moving up in the use-def chain + // with the instruction containing the last found sources. + Res.setInst(Def); + + // If we can still move up in the use-def chain, move to the next + // definition. + if (!TargetRegisterInfo::isPhysicalRegister(Reg) && OneRegSrc) { + Def = MRI.getVRegDef(Reg); + DefIdx = MRI.def_begin(Reg).getOperandNo(); + DefSubReg = Res.getSrcSubReg(0); + return Res; + } + } + // 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 Res; +} |
