#define DEBUG_TYPE "twoaddrinstr"
#include "llvm/CodeGen/Passes.h"
#include "llvm/Function.h"
+#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/LiveVariables.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
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");
STATISTIC(NumReSchedUps, "Number of instructions re-scheduled up");
STATISTIC(NumReSchedDowns, "Number of instructions re-scheduled down");
namespace {
class TwoAddressInstructionPass : public MachineFunctionPass {
+ MachineFunction *MF;
const TargetInstrInfo *TII;
const TargetRegisterInfo *TRI;
const InstrItineraryData *InstrItins;
MachineRegisterInfo *MRI;
LiveVariables *LV;
+ SlotIndexes *Indexes;
+ LiveIntervals *LIS;
AliasAnalysis *AA;
CodeGenOpt::Level OptLevel;
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 regA, unsigned regB, unsigned regC,
MachineInstr *MI, MachineBasicBlock *MBB,
unsigned Dist);
MachineFunction::iterator &mbbi,
unsigned RegA, unsigned RegB, unsigned Dist);
- typedef std::pair<std::pair<unsigned, bool>, MachineInstr*> NewKill;
- bool canUpdateDeletedKills(SmallVector<unsigned, 4> &Kills,
- SmallVector<NewKill, 4> &NewKills,
- MachineBasicBlock *MBB, unsigned Dist);
- bool DeleteUnusedInstr(MachineBasicBlock::iterator &mi,
- MachineBasicBlock::iterator &nmi,
- MachineFunction::iterator &mbbi, unsigned Dist);
-
bool isDefTooClose(unsigned Reg, unsigned Dist,
MachineInstr *MI, MachineBasicBlock *MBB);
void ProcessCopy(MachineInstr *MI, MachineBasicBlock *MBB,
SmallPtrSet<MachineInstr*, 8> &Processed);
+ typedef SmallVector<std::pair<unsigned, unsigned>, 4> TiedPairList;
+ typedef SmallDenseMap<unsigned, TiedPairList> TiedOperandMap;
+ bool collectTiedOperands(MachineInstr *MI, TiedOperandMap&);
+ void processTiedPairs(MachineInstr *MI, TiedPairList&, unsigned &Dist);
+
void CoalesceExtSubRegs(SmallVector<unsigned,4> &Srcs, unsigned DstReg);
/// EliminateRegSequences - Eliminate REG_SEQUENCE instructions as part
AU.setPreservesCFG();
AU.addRequired<AliasAnalysis>();
AU.addPreserved<LiveVariables>();
+ AU.addPreserved<SlotIndexes>();
+ AU.addPreserved<LiveIntervals>();
AU.addPreservedID(MachineLoopInfoID);
AU.addPreservedID(MachineDominatorsID);
MachineFunctionPass::getAnalysisUsage(AU);
// appropriate location, we can try to sink the current instruction
// past it.
if (!KillMI || KillMI->getParent() != MBB || KillMI == MI ||
- KillMI->isTerminator())
+ KillMI == OldPos || KillMI->isTerminator())
return false;
// If any of the definitions are used by another instruction between the
}
}
}
+ assert(KillMO && "Didn't find kill");
// Update kill and LV information.
KillMO->setIsKill(false);
MBB->remove(MI);
MBB->insert(KillPos, MI);
+ if (LIS)
+ LIS->handleMove(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 MCInstrDesc &MCID = UseMI->getDesc();
- for (unsigned i = 0, e = MCID.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<MachineInstr*, unsigned>::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
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<MachineInstr*, unsigned>::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.
}
-/// isProfitableToReMat - Return true if it's potentially profitable to commute
+/// isProfitableToCommute - Return true if it's potentially profitable to commute
/// the two-address instruction that's being processed.
bool
TwoAddressInstructionPass::isProfitableToCommute(unsigned regA, unsigned regB,
if (LV)
// Update live variables
LV->replaceKillInstruction(RegC, MI, NewMI);
+ if (Indexes)
+ Indexes->replaceMachineInstrInMaps(MI, NewMI);
mbbi->insert(mi, NewMI); // Insert the new inst
mbbi->erase(mi); // Nuke the old inst.
DEBUG(dbgs() << "2addr: TO 3-ADDR: " << *NewMI);
bool Sunk = false;
+ if (Indexes)
+ Indexes->replaceMachineInstrInMaps(mi, NewMI);
+
if (NewMI->findRegisterUseOperand(RegB, false, TRI))
// FIXME: Temporary workaround. If the new instruction doesn't
// uses RegB, convertToThreeAddress must have created more
return;
}
-/// 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<unsigned, 4> &Kills) {
- if (MI->mayStore() || MI->isCall())
- return false;
- if (MI->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<unsigned, 4> &Kills,
- SmallVector<NewKill, 4> &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<unsigned, 4> 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<NewKill, 4> 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;
-}
-
/// RescheduleMIBelowKill - If there is one more local instruction that reads
/// 'Reg' and it kills 'Reg, consider moving the instruction below the kill
/// instruction in order to eliminate the need for the copy.
return false;
MachineInstr *KillMI = LV->getVarInfo(Reg).findKill(MBB);
- if (!KillMI || KillMI->isCopy() || KillMI->isCopyLike())
+ if (!KillMI || MI == KillMI || KillMI->isCopy() || KillMI->isCopyLike())
// Don't mess with copies, they may be coalesced later.
return false;
((MO.isKill() && Uses.count(MOReg)) || Kills.count(MOReg)))
// Don't want to extend other live ranges and update kills.
return false;
+ if (MOReg == Reg && !MO.isKill())
+ // We can't schedule across a use of the register in question.
+ return false;
+ // Ensure that if this is register in question, its the kill we expect.
+ assert((MOReg != Reg || OtherMI == KillMI) &&
+ "Found multiple kills of a register in a basic block");
}
}
}
// Update live variables
LV->removeVirtualRegisterKilled(Reg, KillMI);
LV->addVirtualRegisterKilled(Reg, MI);
+ if (LIS)
+ LIS->handleMove(MI);
+ DEBUG(dbgs() << "\trescheduled below kill: " << *KillMI);
return true;
}
return false;
MachineInstr *KillMI = LV->getVarInfo(Reg).findKill(MBB);
- if (!KillMI || KillMI->isCopy() || KillMI->isCopyLike())
+ if (!KillMI || MI == KillMI || KillMI->isCopy() || KillMI->isCopyLike())
// Don't mess with copies, they may be coalesced later.
return false;
continue;
if (isDefTooClose(MOReg, DI->second, MI, MBB))
return false;
+ if (MOReg == Reg && !MO.isKill())
+ return false;
Uses.insert(MOReg);
if (MO.isKill() && MOReg != Reg)
Kills.insert(MOReg);
if (Kills.count(MOReg))
// Don't want to extend other live ranges and update kills.
return false;
+ if (OtherMI != MI && MOReg == Reg && !MO.isKill())
+ // We can't schedule across a use of the register in question.
+ return false;
} else {
OtherDefs.push_back(MOReg);
}
// Update live variables
LV->removeVirtualRegisterKilled(Reg, KillMI);
LV->addVirtualRegisterKilled(Reg, MI);
+ if (LIS)
+ LIS->handleMove(KillMI);
+ DEBUG(dbgs() << "\trescheduled kill: " << *KillMI);
return true;
}
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.
- }
if (TargetRegisterInfo::isVirtualRegister(regA))
ScanUses(regA, &*mbbi, Processed);
if (NewOpc != 0) {
const MCInstrDesc &UnfoldMCID = TII->get(NewOpc);
if (UnfoldMCID.getNumDefs() == 1) {
- MachineFunction &MF = *mbbi->getParent();
-
// Unfold the load.
DEBUG(dbgs() << "2addr: UNFOLDING: " << MI);
const TargetRegisterClass *RC =
TRI->getAllocatableClass(
- TII->getRegClass(UnfoldMCID, LoadRegIndex, TRI, MF));
+ TII->getRegClass(UnfoldMCID, LoadRegIndex, TRI, *MF));
unsigned Reg = MRI->createVirtualRegister(RC);
SmallVector<MachineInstr *, 2> NewMIs;
- if (!TII->unfoldMemoryOperand(MF, &MI, Reg,
+ if (!TII->unfoldMemoryOperand(*MF, &MI, Reg,
/*UnfoldLoad=*/true,/*UnfoldStore=*/false,
NewMIs)) {
DEBUG(dbgs() << "2addr: ABANDONING UNFOLD\n");
return false;
}
+// Collect tied operands of MI that need to be handled.
+// Rewrite trivial cases immediately.
+// Return true if any tied operands where found, including the trivial ones.
+bool TwoAddressInstructionPass::
+collectTiedOperands(MachineInstr *MI, TiedOperandMap &TiedOperands) {
+ const MCInstrDesc &MCID = MI->getDesc();
+ bool AnyOps = false;
+ unsigned NumOps = MI->getNumOperands();
+
+ for (unsigned SrcIdx = 0; SrcIdx < NumOps; ++SrcIdx) {
+ unsigned DstIdx = 0;
+ if (!MI->isRegTiedToDefOperand(SrcIdx, &DstIdx))
+ continue;
+ AnyOps = true;
+ MachineOperand &SrcMO = MI->getOperand(SrcIdx);
+ MachineOperand &DstMO = MI->getOperand(DstIdx);
+ unsigned SrcReg = SrcMO.getReg();
+ unsigned DstReg = DstMO.getReg();
+ // Tied constraint already satisfied?
+ if (SrcReg == DstReg)
+ continue;
+
+ assert(SrcReg && SrcMO.isUse() && "two address instruction invalid");
+
+ // Deal with <undef> uses immediately - simply rewrite the src operand.
+ if (SrcMO.isUndef()) {
+ // Constrain the DstReg register class if required.
+ if (TargetRegisterInfo::isVirtualRegister(DstReg))
+ if (const TargetRegisterClass *RC = TII->getRegClass(MCID, SrcIdx,
+ TRI, *MF))
+ MRI->constrainRegClass(DstReg, RC);
+ SrcMO.setReg(DstReg);
+ DEBUG(dbgs() << "\t\trewrite undef:\t" << *MI);
+ continue;
+ }
+ TiedOperands[SrcReg].push_back(std::make_pair(SrcIdx, DstIdx));
+ }
+ return AnyOps;
+}
+
+// Process a list of tied MI operands that all use the same source register.
+// The tied pairs are of the form (SrcIdx, DstIdx).
+void
+TwoAddressInstructionPass::processTiedPairs(MachineInstr *MI,
+ TiedPairList &TiedPairs,
+ unsigned &Dist) {
+ bool IsEarlyClobber = false;
+ bool RemovedKillFlag = false;
+ bool AllUsesCopied = true;
+ unsigned LastCopiedReg = 0;
+ unsigned RegB = 0;
+ for (unsigned tpi = 0, tpe = TiedPairs.size(); tpi != tpe; ++tpi) {
+ unsigned SrcIdx = TiedPairs[tpi].first;
+ unsigned DstIdx = TiedPairs[tpi].second;
+
+ const MachineOperand &DstMO = MI->getOperand(DstIdx);
+ unsigned RegA = DstMO.getReg();
+ IsEarlyClobber |= DstMO.isEarlyClobber();
+
+ // 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.
+ BuildMI(*MI->getParent(), MI, MI->getDebugLoc(),
+ TII->get(TargetOpcode::COPY), RegA).addReg(RegB);
+
+ // Update DistanceMap.
+ MachineBasicBlock::iterator PrevMI = MI;
+ --PrevMI;
+ DistanceMap.insert(std::make_pair(PrevMI, Dist));
+ DistanceMap[MI] = ++Dist;
+
+ SlotIndex CopyIdx;
+ if (Indexes)
+ CopyIdx = Indexes->insertMachineInstrInMaps(PrevMI).getRegSlot();
+
+ 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;
+ }
+
+ // Make sure regA is a legal regclass for the SrcIdx operand.
+ if (TargetRegisterInfo::isVirtualRegister(RegA) &&
+ TargetRegisterInfo::isVirtualRegister(RegB))
+ MRI->constrainRegClass(RegA, MRI->getRegClass(RegB));
+
+ MO.setReg(RegA);
+
+ // Propagate SrcRegMap.
+ SrcRegMap[RegA] = RegB;
+ }
+
+
+ if (AllUsesCopied) {
+ if (!IsEarlyClobber) {
+ // 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)) {
+ MachineBasicBlock::iterator PrevMI = MI;
+ --PrevMI;
+ LV->addVirtualRegisterKilled(RegB, PrevMI);
+ }
+
+ } 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;
+ }
+ }
+ }
+}
+
/// runOnMachineFunction - Reduce two-address instructions to two operands.
///
-bool TwoAddressInstructionPass::runOnMachineFunction(MachineFunction &MF) {
- const TargetMachine &TM = MF.getTarget();
- MRI = &MF.getRegInfo();
+bool TwoAddressInstructionPass::runOnMachineFunction(MachineFunction &Func) {
+ MF = &Func;
+ const TargetMachine &TM = MF->getTarget();
+ MRI = &MF->getRegInfo();
TII = TM.getInstrInfo();
TRI = TM.getRegisterInfo();
InstrItins = TM.getInstrItineraryData();
+ Indexes = getAnalysisIfAvailable<SlotIndexes>();
LV = getAnalysisIfAvailable<LiveVariables>();
+ LIS = getAnalysisIfAvailable<LiveIntervals>();
AA = &getAnalysis<AliasAnalysis>();
OptLevel = TM.getOptLevel();
DEBUG(dbgs() << "********** REWRITING TWO-ADDR INSTRS **********\n");
DEBUG(dbgs() << "********** Function: "
- << MF.getFunction()->getName() << '\n');
+ << MF->getName() << '\n');
// This pass takes the function out of SSA form.
MRI->leaveSSA();
- // ReMatRegs - Keep track of the registers whose def's are remat'ed.
- BitVector ReMatRegs(MRI->getNumVirtRegs());
-
- typedef DenseMap<unsigned, SmallVector<std::pair<unsigned, unsigned>, 4> >
- TiedOperandMap;
- TiedOperandMap TiedOperands(4);
+ TiedOperandMap TiedOperands;
SmallPtrSet<MachineInstr*, 8> Processed;
- for (MachineFunction::iterator mbbi = MF.begin(), mbbe = MF.end();
+ for (MachineFunction::iterator mbbi = MF->begin(), mbbe = MF->end();
mbbi != mbbe; ++mbbi) {
unsigned Dist = 0;
DistanceMap.clear();
if (mi->isRegSequence())
RegSequences.push_back(&*mi);
- const MCInstrDesc &MCID = 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() : MCID.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();
-
- // Deal with <undef> uses immediately - simply rewrite the src operand.
- if (mi->getOperand(SrcIdx).isUndef()) {
- unsigned DstReg = mi->getOperand(DstIdx).getReg();
- // Constrain the DstReg register class if required.
- if (TargetRegisterInfo::isVirtualRegister(DstReg))
- if (const TargetRegisterClass *RC = TII->getRegClass(MCID, SrcIdx,
- TRI, MF))
- MRI->constrainRegClass(DstReg, RC);
- mi->getOperand(SrcIdx).setReg(DstReg);
- DEBUG(dbgs() << "\t\trewrite undef:\t" << *mi);
- continue;
- }
- TiedOperands[regB].push_back(std::make_pair(SrcIdx, DstIdx));
+ if (!collectTiedOperands(mi, TiedOperands)) {
+ mi = nmi;
+ continue;
}
- // Now iterate over the information collected above.
- for (TiedOperandMap::iterator OI = TiedOperands.begin(),
- OE = TiedOperands.end(); OI != OE; ++OI) {
- SmallVector<std::pair<unsigned, unsigned>, 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) {
+ ++NumTwoAddressInstrs;
+ MadeChange = true;
+ DEBUG(dbgs() << '\t' << *mi);
+
+ // 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) {
+ SmallVector<std::pair<unsigned, unsigned>, 4> &TiedPairs
+ = TiedOperands.begin()->second;
+ if (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,
- Processed))
- break; // The tied operands have been eliminated.
- }
-
- bool IsEarlyClobber = false;
- 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;
-
- const MachineOperand &DstMO = mi->getOperand(DstIdx);
- unsigned regA = DstMO.getReg();
- IsEarlyClobber |= DstMO.isEarlyClobber();
-
- // 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;
+ unsigned SrcReg = mi->getOperand(SrcIdx).getReg();
+ unsigned DstReg = mi->getOperand(DstIdx).getReg();
+ if (SrcReg != DstReg &&
+ TryInstructionTransform(mi, nmi, mbbi, SrcIdx, DstIdx, Dist,
+ Processed)) {
+ // The tied operands have been eliminated or shifted further down the
+ // block to ease elimination. Continue processing with 'nmi'.
+ TiedOperands.clear();
+ mi = nmi;
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.
- bool isCopy = false;
- const TargetRegisterClass *rc = MRI->getRegClass(regB);
- MachineInstr *DefMI = MRI->getUniqueVRegDef(regB);
- // If it's safe and profitable, remat the definition instead of
- // copying it.
- if (DefMI &&
- DefMI->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);
- isCopy = true;
- }
-
- // Update DistanceMap.
- MachineBasicBlock::iterator prevMI = prior(mi);
- 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;
- }
-
- // Make sure regA is a legal regclass for the SrcIdx operand.
- if (TargetRegisterInfo::isVirtualRegister(regA) &&
- TargetRegisterInfo::isVirtualRegister(regB))
- MRI->constrainRegClass(regA, MRI->getRegClass(regB));
-
- MO.setReg(regA);
-
- if (isCopy)
- // Propagate SrcRegMap.
- SrcRegMap[regA] = regB;
}
+ }
- if (AllUsesCopied) {
- if (!IsEarlyClobber) {
- // 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;
-
+ // Now iterate over the information collected above.
+ for (TiedOperandMap::iterator OI = TiedOperands.begin(),
+ OE = TiedOperands.end(); OI != OE; ++OI) {
+ processTiedPairs(mi, OI->second, Dist);
DEBUG(dbgs() << "\t\trewrite to:\t" << *mi);
}
}
}
- // 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();
if (MO.isReg() && MO.isDef() && MO.getReg() == DstReg)
MO.setIsUndef();
}
- // Make sure there is a full non-subreg imp-def operand on the
- // instruction. This shouldn't be necessary, but it seems that at least
- // RAFast requires it.
- Def->addRegisterDefined(DstReg, TRI);
DEBUG(dbgs() << "First def: " << *Def);
}
projects / oota-llvm.git / blobdiff