+
+ // 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.
+ if (CurSrcPair.Reg == Reg)
+ return false;
+
+ return true;
+}
+
+/// \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.