//===-- TwoAddressInstructionPass.cpp - Two-Address instruction pass ------===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This file implements the TwoAddress instruction pass which is used // by most register allocators. Two-Address instructions are rewritten // from: // // A = B op C // // to: // // A = B // A op= C // // Note that if a register allocator chooses to use this pass, that it // has to be capable of handling the non-SSA nature of these rewritten // virtual registers. // // It is also worth noting that the duplicate operand of the two // address instruction is removed. // //===----------------------------------------------------------------------===// #define DEBUG_TYPE "twoaddrinstr" #include "llvm/CodeGen/Passes.h" #include "llvm/Function.h" #include "llvm/CodeGen/LiveVariables.h" #include "llvm/CodeGen/MachineFunctionPass.h" #include "llvm/CodeGen/MachineInstr.h" #include "llvm/CodeGen/MachineInstrBuilder.h" #include "llvm/CodeGen/MachineRegisterInfo.h" #include "llvm/Analysis/AliasAnalysis.h" #include "llvm/Target/TargetRegisterInfo.h" #include "llvm/Target/TargetInstrInfo.h" #include "llvm/Target/TargetMachine.h" #include "llvm/Target/TargetOptions.h" #include "llvm/Support/Debug.h" #include "llvm/Support/ErrorHandling.h" #include "llvm/ADT/BitVector.h" #include "llvm/ADT/DenseMap.h" #include "llvm/ADT/SmallSet.h" #include "llvm/ADT/Statistic.h" #include "llvm/ADT/STLExtras.h" using namespace llvm; STATISTIC(NumTwoAddressInstrs, "Number of two-address instructions"); STATISTIC(NumCommuted , "Number of instructions commuted to coalesce"); STATISTIC(NumAggrCommuted , "Number of instructions aggressively commuted"); STATISTIC(NumConvertedTo3Addr, "Number of instructions promoted to 3-address"); STATISTIC(Num3AddrSunk, "Number of 3-address instructions sunk"); STATISTIC(NumReMats, "Number of instructions re-materialized"); STATISTIC(NumDeletes, "Number of dead instructions deleted"); namespace { class TwoAddressInstructionPass : public MachineFunctionPass { const TargetInstrInfo *TII; const TargetRegisterInfo *TRI; MachineRegisterInfo *MRI; LiveVariables *LV; AliasAnalysis *AA; // DistanceMap - Keep track the distance of a MI from the start of the // current basic block. DenseMap DistanceMap; // SrcRegMap - A map from virtual registers to physical registers which // are likely targets to be coalesced to due to copies from physical // registers to virtual registers. e.g. v1024 = move r0. DenseMap SrcRegMap; // DstRegMap - A map from virtual registers to physical registers which // are likely targets to be coalesced to due to copies to physical // registers from virtual registers. e.g. r1 = move v1024. DenseMap DstRegMap; /// RegSequences - Keep track the list of REG_SEQUENCE instructions seen /// during the initial walk of the machine function. SmallVector RegSequences; bool Sink3AddrInstruction(MachineBasicBlock *MBB, MachineInstr *MI, unsigned Reg, MachineBasicBlock::iterator OldPos); bool isProfitableToReMat(unsigned Reg, const TargetRegisterClass *RC, MachineInstr *MI, MachineInstr *DefMI, MachineBasicBlock *MBB, unsigned Loc); bool NoUseAfterLastDef(unsigned Reg, MachineBasicBlock *MBB, unsigned Dist, unsigned &LastDef); MachineInstr *FindLastUseInMBB(unsigned Reg, MachineBasicBlock *MBB, unsigned Dist); bool isProfitableToCommute(unsigned regB, unsigned regC, MachineInstr *MI, MachineBasicBlock *MBB, unsigned Dist); bool CommuteInstruction(MachineBasicBlock::iterator &mi, MachineFunction::iterator &mbbi, unsigned RegB, unsigned RegC, unsigned Dist); bool isProfitableToConv3Addr(unsigned RegA); bool ConvertInstTo3Addr(MachineBasicBlock::iterator &mi, MachineBasicBlock::iterator &nmi, MachineFunction::iterator &mbbi, unsigned RegB, unsigned Dist); typedef std::pair, MachineInstr*> NewKill; bool canUpdateDeletedKills(SmallVector &Kills, SmallVector &NewKills, MachineBasicBlock *MBB, unsigned Dist); bool DeleteUnusedInstr(MachineBasicBlock::iterator &mi, MachineBasicBlock::iterator &nmi, MachineFunction::iterator &mbbi, unsigned Dist); bool TryInstructionTransform(MachineBasicBlock::iterator &mi, MachineBasicBlock::iterator &nmi, MachineFunction::iterator &mbbi, unsigned SrcIdx, unsigned DstIdx, unsigned Dist); void ProcessCopy(MachineInstr *MI, MachineBasicBlock *MBB, SmallPtrSet &Processed); void CoalesceExtSubRegs(SmallVector &Srcs, unsigned DstReg); /// EliminateRegSequences - Eliminate REG_SEQUENCE instructions as part /// of the de-ssa process. This replaces sources of REG_SEQUENCE as /// sub-register references of the register defined by REG_SEQUENCE. bool EliminateRegSequences(); public: static char ID; // Pass identification, replacement for typeid TwoAddressInstructionPass() : MachineFunctionPass(ID) { initializeTwoAddressInstructionPassPass(*PassRegistry::getPassRegistry()); } virtual void getAnalysisUsage(AnalysisUsage &AU) const { AU.setPreservesCFG(); AU.addRequired(); AU.addPreserved(); AU.addPreservedID(MachineLoopInfoID); AU.addPreservedID(MachineDominatorsID); AU.addPreservedID(PHIEliminationID); MachineFunctionPass::getAnalysisUsage(AU); } /// runOnMachineFunction - Pass entry point. bool runOnMachineFunction(MachineFunction&); }; } char TwoAddressInstructionPass::ID = 0; INITIALIZE_PASS_BEGIN(TwoAddressInstructionPass, "twoaddressinstruction", "Two-Address instruction pass", false, false) INITIALIZE_AG_DEPENDENCY(AliasAnalysis) INITIALIZE_PASS_END(TwoAddressInstructionPass, "twoaddressinstruction", "Two-Address instruction pass", false, false) char &llvm::TwoAddressInstructionPassID = TwoAddressInstructionPass::ID; /// Sink3AddrInstruction - A two-address instruction has been converted to a /// three-address instruction to avoid clobbering a register. Try to sink it /// past the instruction that would kill the above mentioned register to reduce /// register pressure. bool TwoAddressInstructionPass::Sink3AddrInstruction(MachineBasicBlock *MBB, MachineInstr *MI, unsigned SavedReg, MachineBasicBlock::iterator OldPos) { // Check if it's safe to move this instruction. bool SeenStore = true; // Be conservative. if (!MI->isSafeToMove(TII, AA, SeenStore)) return false; unsigned DefReg = 0; SmallSet UseRegs; for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { const MachineOperand &MO = MI->getOperand(i); if (!MO.isReg()) continue; unsigned MOReg = MO.getReg(); if (!MOReg) continue; if (MO.isUse() && MOReg != SavedReg) UseRegs.insert(MO.getReg()); if (!MO.isDef()) continue; if (MO.isImplicit()) // Don't try to move it if it implicitly defines a register. return false; if (DefReg) // For now, don't move any instructions that define multiple registers. return false; DefReg = MO.getReg(); } // Find the instruction that kills SavedReg. MachineInstr *KillMI = NULL; for (MachineRegisterInfo::use_nodbg_iterator UI = MRI->use_nodbg_begin(SavedReg), UE = MRI->use_nodbg_end(); UI != UE; ++UI) { MachineOperand &UseMO = UI.getOperand(); if (!UseMO.isKill()) continue; KillMI = UseMO.getParent(); break; } if (!KillMI || KillMI->getParent() != MBB || KillMI == MI) return false; // If any of the definitions are used by another instruction between the // position and the kill use, then it's not safe to sink it. // // FIXME: This can be sped up if there is an easy way to query whether an // instruction is before or after another instruction. Then we can use // MachineRegisterInfo def / use instead. MachineOperand *KillMO = NULL; MachineBasicBlock::iterator KillPos = KillMI; ++KillPos; unsigned NumVisited = 0; for (MachineBasicBlock::iterator I = llvm::next(OldPos); I != KillPos; ++I) { MachineInstr *OtherMI = I; // DBG_VALUE cannot be counted against the limit. if (OtherMI->isDebugValue()) continue; if (NumVisited > 30) // FIXME: Arbitrary limit to reduce compile time cost. return false; ++NumVisited; for (unsigned i = 0, e = OtherMI->getNumOperands(); i != e; ++i) { MachineOperand &MO = OtherMI->getOperand(i); if (!MO.isReg()) continue; unsigned MOReg = MO.getReg(); if (!MOReg) continue; if (DefReg == MOReg) return false; if (MO.isKill()) { if (OtherMI == KillMI && MOReg == SavedReg) // Save the operand that kills the register. We want to unset the kill // marker if we can sink MI past it. KillMO = &MO; else if (UseRegs.count(MOReg)) // One of the uses is killed before the destination. return false; } } } // Update kill and LV information. KillMO->setIsKill(false); KillMO = MI->findRegisterUseOperand(SavedReg, false, TRI); KillMO->setIsKill(true); if (LV) LV->replaceKillInstruction(SavedReg, KillMI, MI); // Move instruction to its destination. MBB->remove(MI); MBB->insert(KillPos, MI); ++Num3AddrSunk; return true; } /// isTwoAddrUse - Return true if the specified MI is using the specified /// register as a two-address operand. static bool isTwoAddrUse(MachineInstr *UseMI, unsigned Reg) { const TargetInstrDesc &TID = UseMI->getDesc(); for (unsigned i = 0, e = TID.getNumOperands(); i != e; ++i) { MachineOperand &MO = UseMI->getOperand(i); if (MO.isReg() && MO.getReg() == Reg && (MO.isDef() || UseMI->isRegTiedToDefOperand(i))) // Earlier use is a two-address one. return true; } return false; } /// isProfitableToReMat - Return true if the heuristics determines it is likely /// to be profitable to re-materialize the definition of Reg rather than copy /// the register. bool TwoAddressInstructionPass::isProfitableToReMat(unsigned Reg, const TargetRegisterClass *RC, MachineInstr *MI, MachineInstr *DefMI, MachineBasicBlock *MBB, unsigned Loc) { bool OtherUse = false; for (MachineRegisterInfo::use_nodbg_iterator UI = MRI->use_nodbg_begin(Reg), UE = MRI->use_nodbg_end(); UI != UE; ++UI) { MachineOperand &UseMO = UI.getOperand(); MachineInstr *UseMI = UseMO.getParent(); MachineBasicBlock *UseMBB = UseMI->getParent(); if (UseMBB == MBB) { DenseMap::iterator DI = DistanceMap.find(UseMI); if (DI != DistanceMap.end() && DI->second == Loc) continue; // Current use. OtherUse = true; // There is at least one other use in the MBB that will clobber the // register. if (isTwoAddrUse(UseMI, Reg)) return true; } } // If other uses in MBB are not two-address uses, then don't remat. if (OtherUse) return false; // No other uses in the same block, remat if it's defined in the same // block so it does not unnecessarily extend the live range. return MBB == DefMI->getParent(); } /// NoUseAfterLastDef - Return true if there are no intervening uses between the /// last instruction in the MBB that defines the specified register and the /// two-address instruction which is being processed. It also returns the last /// def location by reference bool TwoAddressInstructionPass::NoUseAfterLastDef(unsigned Reg, MachineBasicBlock *MBB, unsigned Dist, unsigned &LastDef) { LastDef = 0; unsigned LastUse = Dist; for (MachineRegisterInfo::reg_iterator I = MRI->reg_begin(Reg), E = MRI->reg_end(); I != E; ++I) { MachineOperand &MO = I.getOperand(); MachineInstr *MI = MO.getParent(); if (MI->getParent() != MBB || MI->isDebugValue()) continue; DenseMap::iterator DI = DistanceMap.find(MI); if (DI == DistanceMap.end()) continue; if (MO.isUse() && DI->second < LastUse) LastUse = DI->second; if (MO.isDef() && DI->second > LastDef) LastDef = DI->second; } return !(LastUse > LastDef && LastUse < Dist); } MachineInstr *TwoAddressInstructionPass::FindLastUseInMBB(unsigned Reg, MachineBasicBlock *MBB, unsigned Dist) { unsigned LastUseDist = 0; MachineInstr *LastUse = 0; for (MachineRegisterInfo::reg_iterator I = MRI->reg_begin(Reg), E = MRI->reg_end(); I != E; ++I) { MachineOperand &MO = I.getOperand(); MachineInstr *MI = MO.getParent(); if (MI->getParent() != MBB || MI->isDebugValue()) continue; DenseMap::iterator DI = DistanceMap.find(MI); if (DI == DistanceMap.end()) continue; if (DI->second >= Dist) continue; if (MO.isUse() && DI->second > LastUseDist) { LastUse = DI->first; LastUseDist = DI->second; } } return LastUse; } /// isCopyToReg - Return true if the specified MI is a copy instruction or /// a extract_subreg instruction. It also returns the source and destination /// registers and whether they are physical registers by reference. static bool isCopyToReg(MachineInstr &MI, const TargetInstrInfo *TII, unsigned &SrcReg, unsigned &DstReg, bool &IsSrcPhys, bool &IsDstPhys) { SrcReg = 0; DstReg = 0; if (MI.isCopy()) { DstReg = MI.getOperand(0).getReg(); SrcReg = MI.getOperand(1).getReg(); } else if (MI.isInsertSubreg() || MI.isSubregToReg()) { DstReg = MI.getOperand(0).getReg(); SrcReg = MI.getOperand(2).getReg(); } else return false; IsSrcPhys = TargetRegisterInfo::isPhysicalRegister(SrcReg); IsDstPhys = TargetRegisterInfo::isPhysicalRegister(DstReg); return true; } /// isKilled - Test if the given register value, which is used by the given /// instruction, is killed by the given instruction. This looks through /// coalescable copies to see if the original value is potentially not killed. /// /// For example, in this code: /// /// %reg1034 = copy %reg1024 /// %reg1035 = copy %reg1025 /// %reg1036 = add %reg1034, %reg1035 /// /// %reg1034 is not considered to be killed, since it is copied from a /// register which is not killed. Treating it as not killed lets the /// normal heuristics commute the (two-address) add, which lets /// coalescing eliminate the extra copy. /// static bool isKilled(MachineInstr &MI, unsigned Reg, const MachineRegisterInfo *MRI, const TargetInstrInfo *TII) { MachineInstr *DefMI = &MI; for (;;) { if (!DefMI->killsRegister(Reg)) return false; if (TargetRegisterInfo::isPhysicalRegister(Reg)) return true; MachineRegisterInfo::def_iterator Begin = MRI->def_begin(Reg); // If there are multiple defs, we can't do a simple analysis, so just // go with what the kill flag says. if (llvm::next(Begin) != MRI->def_end()) return true; DefMI = &*Begin; bool IsSrcPhys, IsDstPhys; unsigned SrcReg, DstReg; // If the def is something other than a copy, then it isn't going to // be coalesced, so follow the kill flag. if (!isCopyToReg(*DefMI, TII, SrcReg, DstReg, IsSrcPhys, IsDstPhys)) return true; Reg = SrcReg; } } /// isTwoAddrUse - Return true if the specified MI uses the specified register /// as a two-address use. If so, return the destination register by reference. static bool isTwoAddrUse(MachineInstr &MI, unsigned Reg, unsigned &DstReg) { const TargetInstrDesc &TID = MI.getDesc(); unsigned NumOps = MI.isInlineAsm() ? MI.getNumOperands():TID.getNumOperands(); for (unsigned i = 0; i != NumOps; ++i) { const MachineOperand &MO = MI.getOperand(i); if (!MO.isReg() || !MO.isUse() || MO.getReg() != Reg) continue; unsigned ti; if (MI.isRegTiedToDefOperand(i, &ti)) { DstReg = MI.getOperand(ti).getReg(); return true; } } return false; } /// findOnlyInterestingUse - Given a register, if has a single in-basic block /// use, return the use instruction if it's a copy or a two-address use. static MachineInstr *findOnlyInterestingUse(unsigned Reg, MachineBasicBlock *MBB, MachineRegisterInfo *MRI, const TargetInstrInfo *TII, bool &IsCopy, unsigned &DstReg, bool &IsDstPhys) { if (!MRI->hasOneNonDBGUse(Reg)) // None or more than one use. return 0; MachineInstr &UseMI = *MRI->use_nodbg_begin(Reg); if (UseMI.getParent() != MBB) return 0; unsigned SrcReg; bool IsSrcPhys; if (isCopyToReg(UseMI, TII, SrcReg, DstReg, IsSrcPhys, IsDstPhys)) { IsCopy = true; return &UseMI; } IsDstPhys = false; if (isTwoAddrUse(UseMI, Reg, DstReg)) { IsDstPhys = TargetRegisterInfo::isPhysicalRegister(DstReg); return &UseMI; } return 0; } /// getMappedReg - Return the physical register the specified virtual register /// might be mapped to. static unsigned getMappedReg(unsigned Reg, DenseMap &RegMap) { while (TargetRegisterInfo::isVirtualRegister(Reg)) { DenseMap::iterator SI = RegMap.find(Reg); if (SI == RegMap.end()) return 0; Reg = SI->second; } if (TargetRegisterInfo::isPhysicalRegister(Reg)) return Reg; return 0; } /// regsAreCompatible - Return true if the two registers are equal or aliased. /// static bool regsAreCompatible(unsigned RegA, unsigned RegB, const TargetRegisterInfo *TRI) { if (RegA == RegB) return true; if (!RegA || !RegB) return false; return TRI->regsOverlap(RegA, RegB); } /// isProfitableToReMat - Return true if it's potentially profitable to commute /// the two-address instruction that's being processed. bool TwoAddressInstructionPass::isProfitableToCommute(unsigned regB, unsigned regC, MachineInstr *MI, MachineBasicBlock *MBB, unsigned Dist) { // Determine if it's profitable to commute this two address instruction. In // general, we want no uses between this instruction and the definition of // the two-address register. // e.g. // %reg1028 = EXTRACT_SUBREG %reg1027, 1 // %reg1029 = MOV8rr %reg1028 // %reg1029 = SHR8ri %reg1029, 7, %EFLAGS // insert => %reg1030 = MOV8rr %reg1028 // %reg1030 = ADD8rr %reg1028, %reg1029, %EFLAGS // In this case, it might not be possible to coalesce the second MOV8rr // instruction if the first one is coalesced. So it would be profitable to // commute it: // %reg1028 = EXTRACT_SUBREG %reg1027, 1 // %reg1029 = MOV8rr %reg1028 // %reg1029 = SHR8ri %reg1029, 7, %EFLAGS // insert => %reg1030 = MOV8rr %reg1029 // %reg1030 = ADD8rr %reg1029, %reg1028, %EFLAGS if (!MI->killsRegister(regC)) return false; // Ok, we have something like: // %reg1030 = ADD8rr %reg1028, %reg1029, %EFLAGS // let's see if it's worth commuting it. // Look for situations like this: // %reg1024 = MOV r1 // %reg1025 = MOV r0 // %reg1026 = ADD %reg1024, %reg1025 // r0 = MOV %reg1026 // Commute the ADD to hopefully eliminate an otherwise unavoidable copy. unsigned FromRegB = getMappedReg(regB, SrcRegMap); unsigned FromRegC = getMappedReg(regC, SrcRegMap); unsigned ToRegB = getMappedReg(regB, DstRegMap); unsigned ToRegC = getMappedReg(regC, DstRegMap); if (!regsAreCompatible(FromRegB, ToRegB, TRI) && ((!FromRegC && !ToRegC) || regsAreCompatible(FromRegB, ToRegC, TRI) || regsAreCompatible(FromRegC, ToRegB, TRI))) return true; // If there is a use of regC between its last def (could be livein) and this // instruction, then bail. unsigned LastDefC = 0; if (!NoUseAfterLastDef(regC, MBB, Dist, LastDefC)) return false; // If there is a use of regB between its last def (could be livein) and this // instruction, then go ahead and make this transformation. unsigned LastDefB = 0; if (!NoUseAfterLastDef(regB, MBB, Dist, LastDefB)) return true; // Since there are no intervening uses for both registers, then commute // if the def of regC is closer. Its live interval is shorter. return LastDefB && LastDefC && LastDefC > LastDefB; } /// CommuteInstruction - Commute a two-address instruction and update the basic /// block, distance map, and live variables if needed. Return true if it is /// successful. bool TwoAddressInstructionPass::CommuteInstruction(MachineBasicBlock::iterator &mi, MachineFunction::iterator &mbbi, unsigned RegB, unsigned RegC, unsigned Dist) { MachineInstr *MI = mi; DEBUG(dbgs() << "2addr: COMMUTING : " << *MI); MachineInstr *NewMI = TII->commuteInstruction(MI); if (NewMI == 0) { DEBUG(dbgs() << "2addr: COMMUTING FAILED!\n"); return false; } DEBUG(dbgs() << "2addr: COMMUTED TO: " << *NewMI); // If the instruction changed to commute it, update livevar. if (NewMI != MI) { if (LV) // Update live variables LV->replaceKillInstruction(RegC, MI, NewMI); mbbi->insert(mi, NewMI); // Insert the new inst mbbi->erase(mi); // Nuke the old inst. mi = NewMI; DistanceMap.insert(std::make_pair(NewMI, Dist)); } // Update source register map. unsigned FromRegC = getMappedReg(RegC, SrcRegMap); if (FromRegC) { unsigned RegA = MI->getOperand(0).getReg(); SrcRegMap[RegA] = FromRegC; } return true; } /// isProfitableToConv3Addr - Return true if it is profitable to convert the /// given 2-address instruction to a 3-address one. bool TwoAddressInstructionPass::isProfitableToConv3Addr(unsigned RegA) { // Look for situations like this: // %reg1024 = MOV r1 // %reg1025 = MOV r0 // %reg1026 = ADD %reg1024, %reg1025 // r2 = MOV %reg1026 // Turn ADD into a 3-address instruction to avoid a copy. unsigned FromRegA = getMappedReg(RegA, SrcRegMap); unsigned ToRegA = getMappedReg(RegA, DstRegMap); return (FromRegA && ToRegA && !regsAreCompatible(FromRegA, ToRegA, TRI)); } /// ConvertInstTo3Addr - Convert the specified two-address instruction into a /// three address one. Return true if this transformation was successful. bool TwoAddressInstructionPass::ConvertInstTo3Addr(MachineBasicBlock::iterator &mi, MachineBasicBlock::iterator &nmi, MachineFunction::iterator &mbbi, unsigned RegB, unsigned Dist) { MachineInstr *NewMI = TII->convertToThreeAddress(mbbi, mi, LV); if (NewMI) { DEBUG(dbgs() << "2addr: CONVERTING 2-ADDR: " << *mi); DEBUG(dbgs() << "2addr: TO 3-ADDR: " << *NewMI); bool Sunk = false; if (NewMI->findRegisterUseOperand(RegB, false, TRI)) // FIXME: Temporary workaround. If the new instruction doesn't // uses RegB, convertToThreeAddress must have created more // then one instruction. Sunk = Sink3AddrInstruction(mbbi, NewMI, RegB, mi); mbbi->erase(mi); // Nuke the old inst. if (!Sunk) { DistanceMap.insert(std::make_pair(NewMI, Dist)); mi = NewMI; nmi = llvm::next(mi); } return true; } return false; } /// ProcessCopy - If the specified instruction is not yet processed, process it /// if it's a copy. For a copy instruction, we find the physical registers the /// source and destination registers might be mapped to. These are kept in /// point-to maps used to determine future optimizations. e.g. /// v1024 = mov r0 /// v1025 = mov r1 /// v1026 = add v1024, v1025 /// r1 = mov r1026 /// If 'add' is a two-address instruction, v1024, v1026 are both potentially /// coalesced to r0 (from the input side). v1025 is mapped to r1. v1026 is /// potentially joined with r1 on the output side. It's worthwhile to commute /// 'add' to eliminate a copy. void TwoAddressInstructionPass::ProcessCopy(MachineInstr *MI, MachineBasicBlock *MBB, SmallPtrSet &Processed) { if (Processed.count(MI)) return; bool IsSrcPhys, IsDstPhys; unsigned SrcReg, DstReg; if (!isCopyToReg(*MI, TII, SrcReg, DstReg, IsSrcPhys, IsDstPhys)) return; if (IsDstPhys && !IsSrcPhys) DstRegMap.insert(std::make_pair(SrcReg, DstReg)); else if (!IsDstPhys && IsSrcPhys) { bool isNew = SrcRegMap.insert(std::make_pair(DstReg, SrcReg)).second; if (!isNew) assert(SrcRegMap[DstReg] == SrcReg && "Can't map to two src physical registers!"); SmallVector VirtRegPairs; bool IsCopy = false; unsigned NewReg = 0; while (MachineInstr *UseMI = findOnlyInterestingUse(DstReg, MBB, MRI,TII, IsCopy, NewReg, IsDstPhys)) { if (IsCopy) { if (!Processed.insert(UseMI)) break; } DenseMap::iterator DI = DistanceMap.find(UseMI); if (DI != DistanceMap.end()) // Earlier in the same MBB.Reached via a back edge. break; if (IsDstPhys) { VirtRegPairs.push_back(NewReg); break; } bool isNew = SrcRegMap.insert(std::make_pair(NewReg, DstReg)).second; if (!isNew) assert(SrcRegMap[NewReg] == DstReg && "Can't map to two src physical registers!"); VirtRegPairs.push_back(NewReg); DstReg = NewReg; } if (!VirtRegPairs.empty()) { unsigned ToReg = VirtRegPairs.back(); VirtRegPairs.pop_back(); while (!VirtRegPairs.empty()) { unsigned FromReg = VirtRegPairs.back(); VirtRegPairs.pop_back(); bool isNew = DstRegMap.insert(std::make_pair(FromReg, ToReg)).second; if (!isNew) assert(DstRegMap[FromReg] == ToReg && "Can't map to two dst physical registers!"); ToReg = FromReg; } } } Processed.insert(MI); } /// isSafeToDelete - If the specified instruction does not produce any side /// effects and all of its defs are dead, then it's safe to delete. static bool isSafeToDelete(MachineInstr *MI, const TargetInstrInfo *TII, SmallVector &Kills) { const TargetInstrDesc &TID = MI->getDesc(); if (TID.mayStore() || TID.isCall()) return false; if (TID.isTerminator() || MI->hasUnmodeledSideEffects()) return false; for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { MachineOperand &MO = MI->getOperand(i); if (!MO.isReg()) continue; if (MO.isDef() && !MO.isDead()) return false; if (MO.isUse() && MO.isKill()) Kills.push_back(MO.getReg()); } return true; } /// canUpdateDeletedKills - Check if all the registers listed in Kills are /// killed by instructions in MBB preceding the current instruction at /// position Dist. If so, return true and record information about the /// preceding kills in NewKills. bool TwoAddressInstructionPass:: canUpdateDeletedKills(SmallVector &Kills, SmallVector &NewKills, MachineBasicBlock *MBB, unsigned Dist) { while (!Kills.empty()) { unsigned Kill = Kills.back(); Kills.pop_back(); if (TargetRegisterInfo::isPhysicalRegister(Kill)) return false; MachineInstr *LastKill = FindLastUseInMBB(Kill, MBB, Dist); if (!LastKill) return false; bool isModRef = LastKill->definesRegister(Kill); NewKills.push_back(std::make_pair(std::make_pair(Kill, isModRef), LastKill)); } return true; } /// DeleteUnusedInstr - If an instruction with a tied register operand can /// be safely deleted, just delete it. bool TwoAddressInstructionPass::DeleteUnusedInstr(MachineBasicBlock::iterator &mi, MachineBasicBlock::iterator &nmi, MachineFunction::iterator &mbbi, unsigned Dist) { // Check if the instruction has no side effects and if all its defs are dead. SmallVector Kills; if (!isSafeToDelete(mi, TII, Kills)) return false; // If this instruction kills some virtual registers, we need to // update the kill information. If it's not possible to do so, // then bail out. SmallVector NewKills; if (!canUpdateDeletedKills(Kills, NewKills, &*mbbi, Dist)) return false; if (LV) { while (!NewKills.empty()) { MachineInstr *NewKill = NewKills.back().second; unsigned Kill = NewKills.back().first.first; bool isDead = NewKills.back().first.second; NewKills.pop_back(); if (LV->removeVirtualRegisterKilled(Kill, mi)) { if (isDead) LV->addVirtualRegisterDead(Kill, NewKill); else LV->addVirtualRegisterKilled(Kill, NewKill); } } } mbbi->erase(mi); // Nuke the old inst. mi = nmi; return true; } /// TryInstructionTransform - For the case where an instruction has a single /// pair of tied register operands, attempt some transformations that may /// either eliminate the tied operands or improve the opportunities for /// coalescing away the register copy. Returns true if the tied operands /// are eliminated altogether. bool TwoAddressInstructionPass:: TryInstructionTransform(MachineBasicBlock::iterator &mi, MachineBasicBlock::iterator &nmi, MachineFunction::iterator &mbbi, unsigned SrcIdx, unsigned DstIdx, unsigned Dist) { const TargetInstrDesc &TID = mi->getDesc(); unsigned regA = mi->getOperand(DstIdx).getReg(); unsigned regB = mi->getOperand(SrcIdx).getReg(); assert(TargetRegisterInfo::isVirtualRegister(regB) && "cannot make instruction into two-address form"); // If regA is dead and the instruction can be deleted, just delete // it so it doesn't clobber regB. bool regBKilled = isKilled(*mi, regB, MRI, TII); if (!regBKilled && mi->getOperand(DstIdx).isDead() && DeleteUnusedInstr(mi, nmi, mbbi, Dist)) { ++NumDeletes; return true; // Done with this instruction. } // Check if it is profitable to commute the operands. unsigned SrcOp1, SrcOp2; unsigned regC = 0; unsigned regCIdx = ~0U; bool TryCommute = false; bool AggressiveCommute = false; if (TID.isCommutable() && mi->getNumOperands() >= 3 && TII->findCommutedOpIndices(mi, SrcOp1, SrcOp2)) { if (SrcIdx == SrcOp1) regCIdx = SrcOp2; else if (SrcIdx == SrcOp2) regCIdx = SrcOp1; if (regCIdx != ~0U) { regC = mi->getOperand(regCIdx).getReg(); if (!regBKilled && isKilled(*mi, regC, MRI, TII)) // If C dies but B does not, swap the B and C operands. // This makes the live ranges of A and C joinable. TryCommute = true; else if (isProfitableToCommute(regB, regC, mi, mbbi, Dist)) { TryCommute = true; AggressiveCommute = true; } } } // If it's profitable to commute, try to do so. if (TryCommute && CommuteInstruction(mi, mbbi, regB, regC, Dist)) { ++NumCommuted; if (AggressiveCommute) ++NumAggrCommuted; return false; } if (TID.isConvertibleTo3Addr()) { // This instruction is potentially convertible to a true // three-address instruction. Check if it is profitable. if (!regBKilled || isProfitableToConv3Addr(regA)) { // Try to convert it. if (ConvertInstTo3Addr(mi, nmi, mbbi, regB, Dist)) { ++NumConvertedTo3Addr; return true; // Done with this instruction. } } } // If this is an instruction with a load folded into it, try unfolding // the load, e.g. avoid this: // movq %rdx, %rcx // addq (%rax), %rcx // in favor of this: // movq (%rax), %rcx // addq %rdx, %rcx // because it's preferable to schedule a load than a register copy. if (TID.mayLoad() && !regBKilled) { // Determine if a load can be unfolded. unsigned LoadRegIndex; unsigned NewOpc = TII->getOpcodeAfterMemoryUnfold(mi->getOpcode(), /*UnfoldLoad=*/true, /*UnfoldStore=*/false, &LoadRegIndex); if (NewOpc != 0) { const TargetInstrDesc &UnfoldTID = TII->get(NewOpc); if (UnfoldTID.getNumDefs() == 1) { MachineFunction &MF = *mbbi->getParent(); // Unfold the load. DEBUG(dbgs() << "2addr: UNFOLDING: " << *mi); const TargetRegisterClass *RC = UnfoldTID.OpInfo[LoadRegIndex].getRegClass(TRI); unsigned Reg = MRI->createVirtualRegister(RC); SmallVector NewMIs; if (!TII->unfoldMemoryOperand(MF, mi, Reg, /*UnfoldLoad=*/true,/*UnfoldStore=*/false, NewMIs)) { DEBUG(dbgs() << "2addr: ABANDONING UNFOLD\n"); return false; } assert(NewMIs.size() == 2 && "Unfolded a load into multiple instructions!"); // The load was previously folded, so this is the only use. NewMIs[1]->addRegisterKilled(Reg, TRI); // Tentatively insert the instructions into the block so that they // look "normal" to the transformation logic. mbbi->insert(mi, NewMIs[0]); mbbi->insert(mi, NewMIs[1]); DEBUG(dbgs() << "2addr: NEW LOAD: " << *NewMIs[0] << "2addr: NEW INST: " << *NewMIs[1]); // Transform the instruction, now that it no longer has a load. unsigned NewDstIdx = NewMIs[1]->findRegisterDefOperandIdx(regA); unsigned NewSrcIdx = NewMIs[1]->findRegisterUseOperandIdx(regB); MachineBasicBlock::iterator NewMI = NewMIs[1]; bool TransformSuccess = TryInstructionTransform(NewMI, mi, mbbi, NewSrcIdx, NewDstIdx, Dist); if (TransformSuccess || NewMIs[1]->getOperand(NewSrcIdx).isKill()) { // Success, or at least we made an improvement. Keep the unfolded // instructions and discard the original. if (LV) { for (unsigned i = 0, e = mi->getNumOperands(); i != e; ++i) { MachineOperand &MO = mi->getOperand(i); if (MO.isReg() && TargetRegisterInfo::isVirtualRegister(MO.getReg())) { if (MO.isUse()) { if (MO.isKill()) { if (NewMIs[0]->killsRegister(MO.getReg())) LV->replaceKillInstruction(MO.getReg(), mi, NewMIs[0]); else { assert(NewMIs[1]->killsRegister(MO.getReg()) && "Kill missing after load unfold!"); LV->replaceKillInstruction(MO.getReg(), mi, NewMIs[1]); } } } else if (LV->removeVirtualRegisterDead(MO.getReg(), mi)) { if (NewMIs[1]->registerDefIsDead(MO.getReg())) LV->addVirtualRegisterDead(MO.getReg(), NewMIs[1]); else { assert(NewMIs[0]->registerDefIsDead(MO.getReg()) && "Dead flag missing after load unfold!"); LV->addVirtualRegisterDead(MO.getReg(), NewMIs[0]); } } } } LV->addVirtualRegisterKilled(Reg, NewMIs[1]); } mi->eraseFromParent(); mi = NewMIs[1]; if (TransformSuccess) return true; } else { // Transforming didn't eliminate the tie and didn't lead to an // improvement. Clean up the unfolded instructions and keep the // original. DEBUG(dbgs() << "2addr: ABANDONING UNFOLD\n"); NewMIs[0]->eraseFromParent(); NewMIs[1]->eraseFromParent(); } } } } return false; } /// runOnMachineFunction - Reduce two-address instructions to two operands. /// bool TwoAddressInstructionPass::runOnMachineFunction(MachineFunction &MF) { DEBUG(dbgs() << "Machine Function\n"); const TargetMachine &TM = MF.getTarget(); MRI = &MF.getRegInfo(); TII = TM.getInstrInfo(); TRI = TM.getRegisterInfo(); LV = getAnalysisIfAvailable(); AA = &getAnalysis(); bool MadeChange = false; DEBUG(dbgs() << "********** REWRITING TWO-ADDR INSTRS **********\n"); DEBUG(dbgs() << "********** Function: " << MF.getFunction()->getName() << '\n'); // ReMatRegs - Keep track of the registers whose def's are remat'ed. BitVector ReMatRegs(MRI->getNumVirtRegs()); typedef DenseMap, 4> > TiedOperandMap; TiedOperandMap TiedOperands(4); SmallPtrSet Processed; for (MachineFunction::iterator mbbi = MF.begin(), mbbe = MF.end(); mbbi != mbbe; ++mbbi) { unsigned Dist = 0; DistanceMap.clear(); SrcRegMap.clear(); DstRegMap.clear(); Processed.clear(); for (MachineBasicBlock::iterator mi = mbbi->begin(), me = mbbi->end(); mi != me; ) { MachineBasicBlock::iterator nmi = llvm::next(mi); if (mi->isDebugValue()) { mi = nmi; continue; } // Remember REG_SEQUENCE instructions, we'll deal with them later. if (mi->isRegSequence()) RegSequences.push_back(&*mi); const TargetInstrDesc &TID = mi->getDesc(); bool FirstTied = true; DistanceMap.insert(std::make_pair(mi, ++Dist)); ProcessCopy(&*mi, &*mbbi, Processed); // First scan through all the tied register uses in this instruction // and record a list of pairs of tied operands for each register. unsigned NumOps = mi->isInlineAsm() ? mi->getNumOperands() : TID.getNumOperands(); for (unsigned SrcIdx = 0; SrcIdx < NumOps; ++SrcIdx) { unsigned DstIdx = 0; if (!mi->isRegTiedToDefOperand(SrcIdx, &DstIdx)) continue; if (FirstTied) { FirstTied = false; ++NumTwoAddressInstrs; DEBUG(dbgs() << '\t' << *mi); } assert(mi->getOperand(SrcIdx).isReg() && mi->getOperand(SrcIdx).getReg() && mi->getOperand(SrcIdx).isUse() && "two address instruction invalid"); unsigned regB = mi->getOperand(SrcIdx).getReg(); TiedOperandMap::iterator OI = TiedOperands.find(regB); if (OI == TiedOperands.end()) { SmallVector, 4> TiedPair; OI = TiedOperands.insert(std::make_pair(regB, TiedPair)).first; } OI->second.push_back(std::make_pair(SrcIdx, DstIdx)); } // Now iterate over the information collected above. for (TiedOperandMap::iterator OI = TiedOperands.begin(), OE = TiedOperands.end(); OI != OE; ++OI) { SmallVector, 4> &TiedPairs = OI->second; // If the instruction has a single pair of tied operands, try some // transformations that may either eliminate the tied operands or // improve the opportunities for coalescing away the register copy. if (TiedOperands.size() == 1 && TiedPairs.size() == 1) { unsigned SrcIdx = TiedPairs[0].first; unsigned DstIdx = TiedPairs[0].second; // If the registers are already equal, nothing needs to be done. if (mi->getOperand(SrcIdx).getReg() == mi->getOperand(DstIdx).getReg()) break; // Done with this instruction. if (TryInstructionTransform(mi, nmi, mbbi, SrcIdx, DstIdx, Dist)) break; // The tied operands have been eliminated. } bool RemovedKillFlag = false; bool AllUsesCopied = true; unsigned LastCopiedReg = 0; unsigned regB = OI->first; for (unsigned tpi = 0, tpe = TiedPairs.size(); tpi != tpe; ++tpi) { unsigned SrcIdx = TiedPairs[tpi].first; unsigned DstIdx = TiedPairs[tpi].second; unsigned regA = mi->getOperand(DstIdx).getReg(); // Grab regB from the instruction because it may have changed if the // instruction was commuted. regB = mi->getOperand(SrcIdx).getReg(); if (regA == regB) { // The register is tied to multiple destinations (or else we would // not have continued this far), but this use of the register // already matches the tied destination. Leave it. AllUsesCopied = false; continue; } LastCopiedReg = regA; assert(TargetRegisterInfo::isVirtualRegister(regB) && "cannot make instruction into two-address form"); #ifndef NDEBUG // First, verify that we don't have a use of "a" in the instruction // (a = b + a for example) because our transformation will not // work. This should never occur because we are in SSA form. for (unsigned i = 0; i != mi->getNumOperands(); ++i) assert(i == DstIdx || !mi->getOperand(i).isReg() || mi->getOperand(i).getReg() != regA); #endif // Emit a copy or rematerialize the definition. const TargetRegisterClass *rc = MRI->getRegClass(regB); MachineInstr *DefMI = MRI->getVRegDef(regB); // If it's safe and profitable, remat the definition instead of // copying it. if (DefMI && DefMI->getDesc().isAsCheapAsAMove() && DefMI->isSafeToReMat(TII, AA, regB) && isProfitableToReMat(regB, rc, mi, DefMI, mbbi, Dist)){ DEBUG(dbgs() << "2addr: REMATTING : " << *DefMI << "\n"); unsigned regASubIdx = mi->getOperand(DstIdx).getSubReg(); TII->reMaterialize(*mbbi, mi, regA, regASubIdx, DefMI, *TRI); ReMatRegs.set(TargetRegisterInfo::virtReg2Index(regB)); ++NumReMats; } else { BuildMI(*mbbi, mi, mi->getDebugLoc(), TII->get(TargetOpcode::COPY), regA).addReg(regB); } MachineBasicBlock::iterator prevMI = prior(mi); // Update DistanceMap. DistanceMap.insert(std::make_pair(prevMI, Dist)); DistanceMap[mi] = ++Dist; DEBUG(dbgs() << "\t\tprepend:\t" << *prevMI); MachineOperand &MO = mi->getOperand(SrcIdx); assert(MO.isReg() && MO.getReg() == regB && MO.isUse() && "inconsistent operand info for 2-reg pass"); if (MO.isKill()) { MO.setIsKill(false); RemovedKillFlag = true; } MO.setReg(regA); } if (AllUsesCopied) { // Replace other (un-tied) uses of regB with LastCopiedReg. for (unsigned i = 0, e = mi->getNumOperands(); i != e; ++i) { MachineOperand &MO = mi->getOperand(i); if (MO.isReg() && MO.getReg() == regB && MO.isUse()) { if (MO.isKill()) { MO.setIsKill(false); RemovedKillFlag = true; } MO.setReg(LastCopiedReg); } } // Update live variables for regB. if (RemovedKillFlag && LV && LV->getVarInfo(regB).removeKill(mi)) LV->addVirtualRegisterKilled(regB, prior(mi)); } else if (RemovedKillFlag) { // Some tied uses of regB matched their destination registers, so // regB is still used in this instruction, but a kill flag was // removed from a different tied use of regB, so now we need to add // a kill flag to one of the remaining uses of regB. for (unsigned i = 0, e = mi->getNumOperands(); i != e; ++i) { MachineOperand &MO = mi->getOperand(i); if (MO.isReg() && MO.getReg() == regB && MO.isUse()) { MO.setIsKill(true); break; } } } // Schedule the source copy / remat inserted to form two-address // instruction. FIXME: Does it matter the distance map may not be // accurate after it's scheduled? TII->scheduleTwoAddrSource(prior(mi), mi, *TRI); MadeChange = true; DEBUG(dbgs() << "\t\trewrite to:\t" << *mi); } // Rewrite INSERT_SUBREG as COPY now that we no longer need SSA form. if (mi->isInsertSubreg()) { // From %reg = INSERT_SUBREG %reg, %subreg, subidx // To %reg:subidx = COPY %subreg unsigned SubIdx = mi->getOperand(3).getImm(); mi->RemoveOperand(3); assert(mi->getOperand(0).getSubReg() == 0 && "Unexpected subreg idx"); mi->getOperand(0).setSubReg(SubIdx); mi->RemoveOperand(1); mi->setDesc(TII->get(TargetOpcode::COPY)); DEBUG(dbgs() << "\t\tconvert to:\t" << *mi); } // Clear TiedOperands here instead of at the top of the loop // since most instructions do not have tied operands. TiedOperands.clear(); mi = nmi; } } // Some remat'ed instructions are dead. for (int i = ReMatRegs.find_first(); i != -1; i = ReMatRegs.find_next(i)) { unsigned VReg = TargetRegisterInfo::index2VirtReg(i); if (MRI->use_nodbg_empty(VReg)) { MachineInstr *DefMI = MRI->getVRegDef(VReg); DefMI->eraseFromParent(); } } // Eliminate REG_SEQUENCE instructions. Their whole purpose was to preseve // SSA form. It's now safe to de-SSA. MadeChange |= EliminateRegSequences(); return MadeChange; } static void UpdateRegSequenceSrcs(unsigned SrcReg, unsigned DstReg, unsigned SubIdx, MachineRegisterInfo *MRI, const TargetRegisterInfo &TRI) { for (MachineRegisterInfo::reg_iterator RI = MRI->reg_begin(SrcReg), RE = MRI->reg_end(); RI != RE; ) { MachineOperand &MO = RI.getOperand(); ++RI; MO.substVirtReg(DstReg, SubIdx, TRI); } } /// CoalesceExtSubRegs - If a number of sources of the REG_SEQUENCE are /// EXTRACT_SUBREG from the same register and to the same virtual register /// with different sub-register indices, attempt to combine the /// EXTRACT_SUBREGs and pre-coalesce them. e.g. /// %reg1026 = VLDMQ %reg1025, 260, pred:14, pred:%reg0 /// %reg1029:6 = EXTRACT_SUBREG %reg1026, 6 /// %reg1029:5 = EXTRACT_SUBREG %reg1026, 5 /// Since D subregs 5, 6 can combine to a Q register, we can coalesce /// reg1026 to reg1029. void TwoAddressInstructionPass::CoalesceExtSubRegs(SmallVector &Srcs, unsigned DstReg) { SmallSet Seen; for (unsigned i = 0, e = Srcs.size(); i != e; ++i) { unsigned SrcReg = Srcs[i]; if (!Seen.insert(SrcReg)) continue; // Check that the instructions are all in the same basic block. MachineInstr *SrcDefMI = MRI->getVRegDef(SrcReg); MachineInstr *DstDefMI = MRI->getVRegDef(DstReg); if (SrcDefMI->getParent() != DstDefMI->getParent()) continue; // If there are no other uses than copies which feed into // the reg_sequence, then we might be able to coalesce them. bool CanCoalesce = true; SmallVector SrcSubIndices, DstSubIndices; for (MachineRegisterInfo::use_nodbg_iterator UI = MRI->use_nodbg_begin(SrcReg), UE = MRI->use_nodbg_end(); UI != UE; ++UI) { MachineInstr *UseMI = &*UI; if (!UseMI->isCopy() || UseMI->getOperand(0).getReg() != DstReg) { CanCoalesce = false; break; } SrcSubIndices.push_back(UseMI->getOperand(1).getSubReg()); DstSubIndices.push_back(UseMI->getOperand(0).getSubReg()); } if (!CanCoalesce || SrcSubIndices.size() < 2) continue; // Check that the source subregisters can be combined. std::sort(SrcSubIndices.begin(), SrcSubIndices.end()); unsigned NewSrcSubIdx = 0; if (!TRI->canCombineSubRegIndices(MRI->getRegClass(SrcReg), SrcSubIndices, NewSrcSubIdx)) continue; // Check that the destination subregisters can also be combined. std::sort(DstSubIndices.begin(), DstSubIndices.end()); unsigned NewDstSubIdx = 0; if (!TRI->canCombineSubRegIndices(MRI->getRegClass(DstReg), DstSubIndices, NewDstSubIdx)) continue; // If neither source nor destination can be combined to the full register, // just give up. This could be improved if it ever matters. if (NewSrcSubIdx != 0 && NewDstSubIdx != 0) continue; // Now that we know that all the uses are extract_subregs and that those // subregs can somehow be combined, scan all the extract_subregs again to // make sure the subregs are in the right order and can be composed. MachineInstr *SomeMI = 0; CanCoalesce = true; for (MachineRegisterInfo::use_nodbg_iterator UI = MRI->use_nodbg_begin(SrcReg), UE = MRI->use_nodbg_end(); UI != UE; ++UI) { MachineInstr *UseMI = &*UI; assert(UseMI->isCopy()); unsigned DstSubIdx = UseMI->getOperand(0).getSubReg(); unsigned SrcSubIdx = UseMI->getOperand(1).getSubReg(); assert(DstSubIdx != 0 && "missing subreg from RegSequence elimination"); if ((NewDstSubIdx == 0 && TRI->composeSubRegIndices(NewSrcSubIdx, DstSubIdx) != SrcSubIdx) || (NewSrcSubIdx == 0 && TRI->composeSubRegIndices(NewDstSubIdx, SrcSubIdx) != DstSubIdx)) { CanCoalesce = false; break; } // Keep track of one of the uses. SomeMI = UseMI; } if (!CanCoalesce) continue; // Insert a copy to replace the original. MachineInstr *CopyMI = BuildMI(*SomeMI->getParent(), SomeMI, SomeMI->getDebugLoc(), TII->get(TargetOpcode::COPY)) .addReg(DstReg, RegState::Define, NewDstSubIdx) .addReg(SrcReg, 0, NewSrcSubIdx); // Remove all the old extract instructions. for (MachineRegisterInfo::use_nodbg_iterator UI = MRI->use_nodbg_begin(SrcReg), UE = MRI->use_nodbg_end(); UI != UE; ) { MachineInstr *UseMI = &*UI; ++UI; if (UseMI == CopyMI) continue; assert(UseMI->isCopy()); // Move any kills to the new copy or extract instruction. if (UseMI->getOperand(1).isKill()) { CopyMI->getOperand(1).setIsKill(); if (LV) // Update live variables LV->replaceKillInstruction(SrcReg, UseMI, &*CopyMI); } UseMI->eraseFromParent(); } } } static bool HasOtherRegSequenceUses(unsigned Reg, MachineInstr *RegSeq, MachineRegisterInfo *MRI) { for (MachineRegisterInfo::use_iterator UI = MRI->use_begin(Reg), UE = MRI->use_end(); UI != UE; ++UI) { MachineInstr *UseMI = &*UI; if (UseMI != RegSeq && UseMI->isRegSequence()) return true; } return false; } /// EliminateRegSequences - Eliminate REG_SEQUENCE instructions as part /// of the de-ssa process. This replaces sources of REG_SEQUENCE as /// sub-register references of the register defined by REG_SEQUENCE. e.g. /// /// %reg1029, %reg1030 = VLD1q16 %reg1024, ... /// %reg1031 = REG_SEQUENCE %reg1029, 5, %reg1030, 6 /// => /// %reg1031:5, %reg1031:6 = VLD1q16 %reg1024, ... bool TwoAddressInstructionPass::EliminateRegSequences() { if (RegSequences.empty()) return false; for (unsigned i = 0, e = RegSequences.size(); i != e; ++i) { MachineInstr *MI = RegSequences[i]; unsigned DstReg = MI->getOperand(0).getReg(); if (MI->getOperand(0).getSubReg() || TargetRegisterInfo::isPhysicalRegister(DstReg) || !(MI->getNumOperands() & 1)) { DEBUG(dbgs() << "Illegal REG_SEQUENCE instruction:" << *MI); llvm_unreachable(0); } bool IsImpDef = true; SmallVector RealSrcs; SmallSet Seen; for (unsigned i = 1, e = MI->getNumOperands(); i < e; i += 2) { unsigned SrcReg = MI->getOperand(i).getReg(); unsigned SubIdx = MI->getOperand(i+1).getImm(); if (MI->getOperand(i).getSubReg() || TargetRegisterInfo::isPhysicalRegister(SrcReg)) { DEBUG(dbgs() << "Illegal REG_SEQUENCE instruction:" << *MI); llvm_unreachable(0); } MachineInstr *DefMI = MRI->getVRegDef(SrcReg); if (DefMI->isImplicitDef()) { DefMI->eraseFromParent(); continue; } IsImpDef = false; // Remember COPY sources. These might be candidate for coalescing. if (DefMI->isCopy() && DefMI->getOperand(1).getSubReg()) RealSrcs.push_back(DefMI->getOperand(1).getReg()); bool isKill = MI->getOperand(i).isKill(); if (!Seen.insert(SrcReg) || MI->getParent() != DefMI->getParent() || !isKill || HasOtherRegSequenceUses(SrcReg, MI, MRI) || !TRI->getMatchingSuperRegClass(MRI->getRegClass(DstReg), MRI->getRegClass(SrcReg), SubIdx)) { // REG_SEQUENCE cannot have duplicated operands, add a copy. // Also add an copy if the source is live-in the block. We don't want // to end up with a partial-redef of a livein, e.g. // BB0: // reg1051:10 = // ... // BB1: // ... = reg1051:10 // BB2: // reg1051:9 = // LiveIntervalAnalysis won't like it. // // If the REG_SEQUENCE doesn't kill its source, keeping live variables // correctly up to date becomes very difficult. Insert a copy. // Defer any kill flag to the last operand using SrcReg. Otherwise, we // might insert a COPY that uses SrcReg after is was killed. if (isKill) for (unsigned j = i + 2; j < e; j += 2) if (MI->getOperand(j).getReg() == SrcReg) { MI->getOperand(j).setIsKill(); isKill = false; break; } MachineBasicBlock::iterator InsertLoc = MI; MachineInstr *CopyMI = BuildMI(*MI->getParent(), InsertLoc, MI->getDebugLoc(), TII->get(TargetOpcode::COPY)) .addReg(DstReg, RegState::Define, SubIdx) .addReg(SrcReg, getKillRegState(isKill)); MI->getOperand(i).setReg(0); if (LV && isKill) LV->replaceKillInstruction(SrcReg, MI, CopyMI); DEBUG(dbgs() << "Inserted: " << *CopyMI); } } for (unsigned i = 1, e = MI->getNumOperands(); i < e; i += 2) { unsigned SrcReg = MI->getOperand(i).getReg(); if (!SrcReg) continue; unsigned SubIdx = MI->getOperand(i+1).getImm(); UpdateRegSequenceSrcs(SrcReg, DstReg, SubIdx, MRI, *TRI); } if (IsImpDef) { DEBUG(dbgs() << "Turned: " << *MI << " into an IMPLICIT_DEF"); MI->setDesc(TII->get(TargetOpcode::IMPLICIT_DEF)); for (int j = MI->getNumOperands() - 1, ee = 0; j > ee; --j) MI->RemoveOperand(j); } else { DEBUG(dbgs() << "Eliminated: " << *MI); MI->eraseFromParent(); } // Try coalescing some EXTRACT_SUBREG instructions. This can create // INSERT_SUBREG instructions that must have flags added by // LiveIntervalAnalysis, so only run it when LiveVariables is available. if (LV) CoalesceExtSubRegs(RealSrcs, DstReg); } RegSequences.clear(); return true; }