X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FCodeGen%2FTwoAddressInstructionPass.cpp;h=52a54eb5bd86876a418700207816dfb11edfa874;hb=253174bf50c932abaa680f465e2888c0e5272267;hp=977a8ff54ad7b9a72c2d3ab4b058966d2e59edae;hpb=875357d213ab1830efa1e3e9de0fcde95df7eefc;p=oota-llvm.git diff --git a/lib/CodeGen/TwoAddressInstructionPass.cpp b/lib/CodeGen/TwoAddressInstructionPass.cpp index 977a8ff54ad..52a54eb5bd8 100644 --- a/lib/CodeGen/TwoAddressInstructionPass.cpp +++ b/lib/CodeGen/TwoAddressInstructionPass.cpp @@ -37,9 +37,12 @@ #include "llvm/Target/TargetRegisterInfo.h" #include "llvm/Target/TargetInstrInfo.h" #include "llvm/Target/TargetMachine.h" -#include "llvm/Support/CommandLine.h" +#include "llvm/Target/TargetOptions.h" #include "llvm/Support/Compiler.h" #include "llvm/Support/Debug.h" +#include "llvm/ADT/BitVector.h" +#include "llvm/ADT/DenseMap.h" +#include "llvm/ADT/SmallPtrSet.h" #include "llvm/ADT/Statistic.h" #include "llvm/ADT/STLExtras.h" using namespace llvm; @@ -48,55 +51,54 @@ STATISTIC(NumTwoAddressInstrs, "Number of two-address instructions"); STATISTIC(NumCommuted , "Number of instructions commuted to coalesce"); STATISTIC(NumConvertedTo3Addr, "Number of instructions promoted to 3-address"); STATISTIC(Num3AddrSunk, "Number of 3-address instructions sunk"); +STATISTIC(NumReMats, "Number of instructions re-materialized"); namespace { - static cl::opt - SinkLimit("two-addr-sink-limit", cl::init(-1), cl::Hidden); -} - -namespace { - struct VISIBILITY_HIDDEN TwoAddressInstructionPass - : public MachineFunctionPass { + class VISIBILITY_HIDDEN TwoAddressInstructionPass + : public MachineFunctionPass { const TargetInstrInfo *TII; const TargetRegisterInfo *TRI; MachineRegisterInfo *MRI; LiveVariables *LV; + 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, + DenseMap &DistanceMap); public: static char ID; // Pass identification, replacement for typeid - TwoAddressInstructionPass() : MachineFunctionPass((intptr_t)&ID) {} - - virtual void getAnalysisUsage(AnalysisUsage &AU) const; + TwoAddressInstructionPass() : MachineFunctionPass(&ID) {} + + virtual void getAnalysisUsage(AnalysisUsage &AU) const { + AU.addPreserved(); + AU.addPreservedID(MachineLoopInfoID); + AU.addPreservedID(MachineDominatorsID); + if (StrongPHIElim) + AU.addPreservedID(StrongPHIEliminationID); + else + AU.addPreservedID(PHIEliminationID); + MachineFunctionPass::getAnalysisUsage(AU); + } - /// runOnMachineFunction - pass entry point + /// runOnMachineFunction - Pass entry point. bool runOnMachineFunction(MachineFunction&); - - private: - bool Sink3AddrInstruction(MachineBasicBlock *MBB, MachineInstr *MI, - unsigned Reg, - MachineBasicBlock::iterator OldPos); }; - - char TwoAddressInstructionPass::ID = 0; - RegisterPass - X("twoaddressinstruction", "Two-Address instruction pass"); } -const PassInfo *llvm::TwoAddressInstructionPassID = X.getPassInfo(); +char TwoAddressInstructionPass::ID = 0; +static RegisterPass +X("twoaddressinstruction", "Two-Address instruction pass"); -void TwoAddressInstructionPass::getAnalysisUsage(AnalysisUsage &AU) const { - AU.addRequired(); - AU.addPreserved(); - AU.addPreservedID(MachineLoopInfoID); - AU.addPreservedID(MachineDominatorsID); - AU.addPreservedID(PHIEliminationID); - MachineFunctionPass::getAnalysisUsage(AU); -} +const PassInfo *const llvm::TwoAddressInstructionPassID = &X; /// 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. +/// 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) { @@ -107,9 +109,10 @@ bool TwoAddressInstructionPass::Sink3AddrInstruction(MachineBasicBlock *MBB, unsigned DefReg = 0; SmallSet UseRegs; + for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { const MachineOperand &MO = MI->getOperand(i); - if (!MO.isRegister()) + if (!MO.isReg()) continue; unsigned MOReg = MO.getReg(); if (!MOReg) @@ -137,32 +140,40 @@ bool TwoAddressInstructionPass::Sink3AddrInstruction(MachineBasicBlock *MBB, KillMI = UseMO.getParent(); break; } + if (!KillMI || KillMI->getParent() != MBB) 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 if before or after another instruction. Then we can - // use MachineRegisterInfo def / use instead. + // 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 = next(OldPos); I != KillPos; ++I) { MachineInstr *OtherMI = I; + 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.isRegister()) + 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 unset the kill - // marker is we can sink MI past it. + // 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. @@ -171,16 +182,13 @@ bool TwoAddressInstructionPass::Sink3AddrInstruction(MachineBasicBlock *MBB, } } - if (SinkLimit != -1 && Num3AddrSunk == (unsigned)SinkLimit) - return false; - // Update kill and LV information. KillMO->setIsKill(false); KillMO = MI->findRegisterUseOperand(SavedReg, false, TRI); KillMO->setIsKill(true); - LiveVariables::VarInfo& VarInfo = LV->getVarInfo(SavedReg); - VarInfo.removeKill(KillMI); - VarInfo.Kills.push_back(MI); + + if (LV) + LV->replaceKillInstruction(SavedReg, KillMI, MI); // Move instruction to its destination. MBB->remove(MI); @@ -190,8 +198,59 @@ bool TwoAddressInstructionPass::Sink3AddrInstruction(MachineBasicBlock *MBB, return true; } -/// runOnMachineFunction - Reduce two-address instructions to two -/// operands. +/// 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() || TID.getOperandConstraint(i, TOI::TIED_TO) != -1)) + // 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, + DenseMap &DistanceMap){ + bool OtherUse = false; + for (MachineRegisterInfo::use_iterator UI = MRI->use_begin(Reg), + UE = MRI->use_end(); UI != UE; ++UI) { + MachineOperand &UseMO = UI.getOperand(); + if (!UseMO.isUse()) + continue; + 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(); +} + +/// runOnMachineFunction - Reduce two-address instructions to two operands. /// bool TwoAddressInstructionPass::runOnMachineFunction(MachineFunction &MF) { DOUT << "Machine Function\n"; @@ -199,20 +258,32 @@ bool TwoAddressInstructionPass::runOnMachineFunction(MachineFunction &MF) { MRI = &MF.getRegInfo(); TII = TM.getInstrInfo(); TRI = TM.getRegisterInfo(); - LV = &getAnalysis(); + LV = getAnalysisToUpdate(); bool MadeChange = false; DOUT << "********** REWRITING TWO-ADDR INSTRS **********\n"; DOUT << "********** Function: " << MF.getFunction()->getName() << '\n'; + // ReMatRegs - Keep track of the registers whose def's are remat'ed. + BitVector ReMatRegs; + ReMatRegs.resize(MRI->getLastVirtReg()+1); + + // DistanceMap - Keep track the distance of a MI from the start of the + // current basic block. + DenseMap DistanceMap; + for (MachineFunction::iterator mbbi = MF.begin(), mbbe = MF.end(); mbbi != mbbe; ++mbbi) { + unsigned Dist = 0; + DistanceMap.clear(); for (MachineBasicBlock::iterator mi = mbbi->begin(), me = mbbi->end(); - mi != me; ++mi) { + mi != me; ) { + MachineBasicBlock::iterator nmi = next(mi); const TargetInstrDesc &TID = mi->getDesc(); - bool FirstTied = true; + + DistanceMap.insert(std::make_pair(mi, ++Dist)); for (unsigned si = 1, e = TID.getNumOperands(); si < e; ++si) { int ti = TID.getOperandConstraint(si, TOI::TIED_TO); if (ti == -1) @@ -222,15 +293,16 @@ bool TwoAddressInstructionPass::runOnMachineFunction(MachineFunction &MF) { ++NumTwoAddressInstrs; DOUT << '\t'; DEBUG(mi->print(*cerr.stream(), &TM)); } + FirstTied = false; - assert(mi->getOperand(si).isRegister() && mi->getOperand(si).getReg() && + assert(mi->getOperand(si).isReg() && mi->getOperand(si).getReg() && mi->getOperand(si).isUse() && "two address instruction invalid"); - // if the two operands are the same we just remove the use + // If the two operands are the same we just remove the use // and mark the def as def&use, otherwise we have to insert a copy. if (mi->getOperand(ti).getReg() != mi->getOperand(si).getReg()) { - // rewrite: + // Rewrite: // a = b op c // to: // a = b @@ -248,7 +320,7 @@ bool TwoAddressInstructionPass::runOnMachineFunction(MachineFunction &MF) { // should never occur because we are in SSA form. for (unsigned i = 0; i != mi->getNumOperands(); ++i) assert((int)i == ti || - !mi->getOperand(i).isRegister() || + !mi->getOperand(i).isReg() || mi->getOperand(i).getReg() != regA); #endif @@ -262,22 +334,28 @@ bool TwoAddressInstructionPass::runOnMachineFunction(MachineFunction &MF) { // and C joinable. // FIXME: This code also works for A := B op C instructions. if (TID.isCommutable() && mi->getNumOperands() >= 3) { - assert(mi->getOperand(3-si).isRegister() && + assert(mi->getOperand(3-si).isReg() && "Not a proper commutative instruction!"); unsigned regC = mi->getOperand(3-si).getReg(); + if (mi->killsRegister(regC)) { DOUT << "2addr: COMMUTING : " << *mi; MachineInstr *NewMI = TII->commuteInstruction(mi); + if (NewMI == 0) { DOUT << "2addr: COMMUTING FAILED!\n"; } else { DOUT << "2addr: COMMUTED TO: " << *NewMI; // If the instruction changed to commute it, update livevar. if (NewMI != mi) { - LV->instructionChanged(mi, NewMI); // Update live variables + 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)); } ++NumCommuted; @@ -293,43 +371,74 @@ bool TwoAddressInstructionPass::runOnMachineFunction(MachineFunction &MF) { // FIXME: This assumes there are no more operands which are tied // to another register. #ifndef NDEBUG - for (unsigned i = si+1, e = TID.getNumOperands(); i < e; ++i) + for (unsigned i = si + 1, e = TID.getNumOperands(); i < e; ++i) assert(TID.getOperandConstraint(i, TOI::TIED_TO) == -1); #endif - if (MachineInstr *New=TII->convertToThreeAddress(mbbi, mi, *LV)) { + MachineInstr *NewMI = TII->convertToThreeAddress(mbbi, mi, LV); + if (NewMI) { DOUT << "2addr: CONVERTING 2-ADDR: " << *mi; - DOUT << "2addr: TO 3-ADDR: " << *New; - bool Sunk = Sink3AddrInstruction(mbbi, New, regB, mi); - mbbi->erase(mi); // Nuke the old inst. - if (!Sunk) mi = New; + DOUT << "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 = next(mi); + } + ++NumConvertedTo3Addr; - // Done with this instruction. - break; + break; // Done with this instruction. } } } InstructionRearranged: - const TargetRegisterClass* rc = MF.getRegInfo().getRegClass(regA); - TII->copyRegToReg(*mbbi, mi, regA, regB, rc, rc); + const TargetRegisterClass* rc = MRI->getRegClass(regA); + 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, regB) && + isProfitableToReMat(regB, rc, mi, DefMI, mbbi, Dist,DistanceMap)){ + DEBUG(cerr << "2addr: REMATTING : " << *DefMI << "\n"); + TII->reMaterialize(*mbbi, mi, regA, DefMI); + ReMatRegs.set(regB); + ++NumReMats; + } else { + TII->copyRegToReg(*mbbi, mi, regA, regB, rc, rc); + } MachineBasicBlock::iterator prevMi = prior(mi); - DOUT << "\t\tprepend:\t"; DEBUG(prevMi->print(*cerr.stream(), &TM)); - // update live variables for regB - LiveVariables::VarInfo& varInfoB = LV->getVarInfo(regB); - // regB is used in this BB. - varInfoB.UsedBlocks[mbbi->getNumber()] = true; - if (LV->removeVirtualRegisterKilled(regB, mbbi, mi)) - LV->addVirtualRegisterKilled(regB, prevMi); + // Update live variables for regB. + if (LV) { + LiveVariables::VarInfo& varInfoB = LV->getVarInfo(regB); + + // regB is used in this BB. + varInfoB.UsedBlocks[mbbi->getNumber()] = true; - if (LV->removeVirtualRegisterDead(regB, mbbi, mi)) - LV->addVirtualRegisterDead(regB, prevMi); + if (LV->removeVirtualRegisterKilled(regB, mi)) + LV->addVirtualRegisterKilled(regB, prevMi); - // replace all occurences of regB with regA + if (LV->removeVirtualRegisterDead(regB, mi)) + LV->addVirtualRegisterDead(regB, prevMi); + } + + DOUT << "\t\tprepend:\t"; DEBUG(prevMi->print(*cerr.stream(), &TM)); + + // Replace all occurences of regB with regA. for (unsigned i = 0, e = mi->getNumOperands(); i != e; ++i) { - if (mi->getOperand(i).isRegister() && + if (mi->getOperand(i).isReg() && mi->getOperand(i).getReg() == regB) mi->getOperand(i).setReg(regA); } @@ -341,7 +450,19 @@ bool TwoAddressInstructionPass::runOnMachineFunction(MachineFunction &MF) { DOUT << "\t\trewrite to:\t"; DEBUG(mi->print(*cerr.stream(), &TM)); } + + mi = nmi; + } + } + + // Some remat'ed instructions are dead. + int VReg = ReMatRegs.find_first(); + while (VReg != -1) { + if (MRI->use_empty(VReg)) { + MachineInstr *DefMI = MRI->getVRegDef(VReg); + DefMI->eraseFromParent(); } + VReg = ReMatRegs.find_next(VReg); } return MadeChange;