MachineFunction::iterator &mbbi,
unsigned regB, unsigned regBIdx, 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<MachineInstr*, 8> &Processed);
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, regB, SrcIdx, 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.
+ }
+ }
+ }
+ return false;
+}
+
/// runOnMachineFunction - Reduce two-address instructions to two operands.
///
bool TwoAddressInstructionPass::runOnMachineFunction(MachineFunction &MF) {
BitVector ReMatRegs;
ReMatRegs.resize(MRI->getLastVirtReg()+1);
+ typedef DenseMap<unsigned, SmallVector<std::pair<unsigned, unsigned>, 4> >
+ TiedOperandMap;
+ TiedOperandMap TiedOperands(4);
+
SmallPtrSet<MachineInstr*, 8> Processed;
for (MachineFunction::iterator mbbi = MF.begin(), mbbe = MF.end();
mbbi != mbbe; ++mbbi) {
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->getOpcode() == TargetInstrInfo::INLINEASM)
? mi->getNumOperands() : TID.getNumOperands();
- for (unsigned si = 0; si < NumOps; ++si) {
- unsigned ti = 0;
- if (!mi->isRegTiedToDefOperand(si, &ti))
+ for (unsigned SrcIdx = 0; SrcIdx < NumOps; ++SrcIdx) {
+ unsigned DstIdx = 0;
+ if (!mi->isRegTiedToDefOperand(SrcIdx, &DstIdx))
continue;
if (FirstTied) {
+ FirstTied = false;
++NumTwoAddressInstrs;
DEBUG(errs() << '\t' << *mi);
}
- FirstTied = false;
-
- assert(mi->getOperand(si).isReg() && mi->getOperand(si).getReg() &&
- mi->getOperand(si).isUse() && "two address instruction invalid");
-
- // If the two operands are the same, nothing needs to be done.
- if (mi->getOperand(ti).getReg() == mi->getOperand(si).getReg())
- continue;
-
- // Rewrite:
- // a = b op c
- // to:
- // a = b
- // a = a op c
- unsigned regA = mi->getOperand(ti).getReg();
- unsigned regB = mi->getOperand(si).getReg();
- unsigned regASubIdx = mi->getOperand(ti).getSubReg();
-
- assert(TargetRegisterInfo::isVirtualRegister(regB) &&
- "cannot make instruction into two-address form");
+ assert(mi->getOperand(SrcIdx).isReg() &&
+ mi->getOperand(SrcIdx).getReg() &&
+ mi->getOperand(SrcIdx).isUse() &&
+ "two address instruction invalid");
-#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 == ti ||
- !mi->getOperand(i).isReg() ||
- mi->getOperand(i).getReg() != regA);
-#endif
+ unsigned regB = mi->getOperand(SrcIdx).getReg();
+ TiedOperandMap::iterator OI = TiedOperands.find(regB);
+ if (OI == TiedOperands.end()) {
+ SmallVector<std::pair<unsigned, unsigned>, 4> TiedPair;
+ OI = TiedOperands.insert(std::make_pair(regB, TiedPair)).first;
+ }
+ OI->second.push_back(std::make_pair(SrcIdx, DstIdx));
+ }
- // 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(ti).isDead() &&
- DeleteUnusedInstr(mi, nmi, mbbi, regB, si, Dist)) {
- ++NumDeletes;
- break; // Done with this instruction.
+ // 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) {
+ 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.
}
- // Check if it is profitable to commute the operands.
- unsigned SrcOp1, SrcOp2;
- unsigned regC = 0;
- bool TryCommute = false;
- bool AggressiveCommute = false;
- if (TID.isCommutable() && mi->getNumOperands() >= 3 &&
- TII->findCommutedOpIndices(mi, SrcOp1, SrcOp2)) {
- if (si == SrcOp1)
- regC = mi->getOperand(SrcOp2).getReg();
- else if (si == SrcOp2)
- regC = mi->getOperand(SrcOp1).getReg();
-
- if (regC) {
- 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;
- }
+ 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");
- // If it's profitable to commute, try to do so.
- if (TryCommute && CommuteInstruction(mi, mbbi, regB, regC, Dist)) {
- ++NumCommuted;
- if (AggressiveCommute)
- ++NumAggrCommuted;
- regB = regC;
- } else if (TID.isConvertibleTo3Addr()) {
- // This instruction is potentially convertible to a true
- // three-address instruction. Check if it is profitable.
- if (!regBKilled || isProfitableToConv3Addr(regA)) {
- // 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)
- assert(TID.getOperandConstraint(i, TOI::TIED_TO) == -1);
+ // 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
- // Try to convert it.
- if (ConvertInstTo3Addr(mi, nmi, mbbi, regB, Dist)) {
- ++NumConvertedTo3Addr;
- break; // Done with this instruction.
- }
+
+ // 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, regB) &&
+ isProfitableToReMat(regB, rc, mi, DefMI, mbbi, Dist)){
+ DEBUG(errs() << "2addr: REMATTING : " << *DefMI << "\n");
+ unsigned regASubIdx = mi->getOperand(DstIdx).getSubReg();
+ TII->reMaterialize(*mbbi, mi, regA, regASubIdx, DefMI);
+ ReMatRegs.set(regB);
+ ++NumReMats;
+ } else {
+ bool Emitted = TII->copyRegToReg(*mbbi, mi, regA, regB, rc, rc);
+ (void)Emitted;
+ assert(Emitted && "Unable to issue a copy instruction!\n");
}
- }
- 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, regB) &&
- isProfitableToReMat(regB, rc, mi, DefMI, mbbi, Dist)){
- DEBUG(errs() << "2addr: REMATTING : " << *DefMI << "\n");
- TII->reMaterialize(*mbbi, mi, regA, regASubIdx, DefMI);
- ReMatRegs.set(regB);
- ++NumReMats;
- } else {
- bool Emitted = TII->copyRegToReg(*mbbi, mi, regA, regB, rc, rc);
- (void)Emitted;
- assert(Emitted && "Unable to issue a copy instruction!\n");
- }
+ MachineBasicBlock::iterator prevMI = prior(mi);
+ // Update DistanceMap.
+ DistanceMap.insert(std::make_pair(prevMI, Dist));
+ DistanceMap[mi] = ++Dist;
- MachineBasicBlock::iterator prevMI = prior(mi);
- // Update DistanceMap.
- DistanceMap.insert(std::make_pair(prevMI, Dist));
- DistanceMap[mi] = ++Dist;
-
- // Scan the operands to find: (1) the use operand that kills regB (if
- // any); (2) whether the kill operand is being replaced by regA on
- // this iteration; and (3) the first use of regB that is not being
- // replaced on this iteration. A use of regB will not replaced if it
- // is tied to a different destination register and will be handled on
- // a later iteration.
- MachineOperand *KillMO = NULL;
- MachineOperand *FirstKeptMO = NULL;
- bool KillMOKept = false;
- for (unsigned i = 0, e = mi->getNumOperands(); i != e; ++i) {
- MachineOperand &MO = mi->getOperand(i);
- if (MO.isReg() && MO.getReg() == regB && MO.isUse()) {
-
- // Check if this operand is tied to a different destination.
- bool isKept = false;
- unsigned dsti = 0;
- if (mi->isRegTiedToDefOperand(i, &dsti) && dsti != ti) {
- isKept = true;
- if (!FirstKeptMO)
- FirstKeptMO = &MO;
- }
+ DEBUG(errs() << "\t\tprepend:\t" << *prevMI);
- if (MO.isKill()) {
- KillMO = &MO;
- KillMOKept = isKept;
- }
+ 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);
}
- // Update live variables for regB.
- if (KillMO) {
- if (!FirstKeptMO) {
- // All uses of regB are being replaced; move the kill to prevMI.
- KillMO->setIsKill(false);
- if (LV && LV->getVarInfo(regB).removeKill(mi))
- LV->addVirtualRegisterKilled(regB, prevMI);
- } else {
- if (!KillMOKept) {
- // The kill marker is on an operand being replaced, but there
- // are other uses of regB remaining. Move the kill marker to
- // one of them.
- KillMO->setIsKill(false);
- FirstKeptMO->setIsKill(true);
+ 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);
}
}
- }
-
- DEBUG(errs() << "\t\tprepend:\t" << *prevMI);
- // Replace uses of regB with regA.
- for (unsigned i = 0, e = mi->getNumOperands(); i != e; ++i) {
- MachineOperand &MO = mi->getOperand(i);
- if (MO.isReg() && MO.getReg() == regB && MO.isUse()) {
-
- // Skip operands that are tied to other register definitions.
- unsigned dsti = 0;
- if (mi->isRegTiedToDefOperand(i, &dsti) && dsti != ti)
- continue;
-
- MO.setReg(regA);
+ // 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;
+ }
}
}
-
- assert(mi->getOperand(ti).isDef() && mi->getOperand(si).isUse());
- mi->getOperand(ti).setReg(mi->getOperand(si).getReg());
+
MadeChange = true;
DEBUG(errs() << "\t\trewrite 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;
}
}
projects / oota-llvm.git / commitdiff