+/// 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_iterator UI = MRI->use_begin(Reg),
+ UE = MRI->use_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
+/// 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)
+ continue;
+ DenseMap<MachineInstr*, unsigned>::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)
+ 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.
+static bool isCopyToReg(MachineInstr &MI, const TargetInstrInfo *TII,
+ unsigned &SrcReg, unsigned &DstReg,
+ bool &IsSrcPhys, bool &IsDstPhys) {
+ SrcReg = 0;
+ DstReg = 0;
+ unsigned SrcSubIdx, DstSubIdx;
+ if (!TII->isMoveInstr(MI, SrcReg, DstReg, SrcSubIdx, DstSubIdx)) {
+ if (MI.getOpcode() == TargetInstrInfo::EXTRACT_SUBREG) {
+ DstReg = MI.getOperand(0).getReg();
+ SrcReg = MI.getOperand(1).getReg();
+ } else if (MI.getOpcode() == TargetInstrInfo::INSERT_SUBREG) {
+ DstReg = MI.getOperand(0).getReg();
+ SrcReg = MI.getOperand(2).getReg();
+ } else if (MI.getOpcode() == TargetInstrInfo::SUBREG_TO_REG) {
+ DstReg = MI.getOperand(0).getReg();
+ SrcReg = MI.getOperand(2).getReg();
+ }
+ }
+
+ if (DstReg) {
+ IsSrcPhys = TargetRegisterInfo::isPhysicalRegister(SrcReg);
+ IsDstPhys = TargetRegisterInfo::isPhysicalRegister(DstReg);
+ return true;
+ }
+ return false;
+}
+
+/// 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<kill>
+/// %reg1036 = add %reg1034<kill>, %reg1035<kill>
+///
+/// %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.getOpcode() == TargetInstrInfo::INLINEASM)
+ ? 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) {
+ MachineRegisterInfo::use_iterator UI = MRI->use_begin(Reg);
+ if (UI == MRI->use_end())
+ return 0;
+ MachineInstr &UseMI = *UI;
+ if (++UI != MRI->use_end())
+ // More than one use.
+ return 0;
+ 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<unsigned, unsigned> &RegMap) {
+ while (TargetRegisterInfo::isVirtualRegister(Reg)) {
+ DenseMap<unsigned, unsigned>::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<def> = EXTRACT_SUBREG %reg1027<kill>, 1
+ // %reg1029<def> = MOV8rr %reg1028
+ // %reg1029<def> = SHR8ri %reg1029, 7, %EFLAGS<imp-def,dead>
+ // insert => %reg1030<def> = MOV8rr %reg1028
+ // %reg1030<def> = ADD8rr %reg1028<kill>, %reg1029<kill>, %EFLAGS<imp-def,dead>
+ // 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<def> = EXTRACT_SUBREG %reg1027<kill>, 1
+ // %reg1029<def> = MOV8rr %reg1028
+ // %reg1029<def> = SHR8ri %reg1029, 7, %EFLAGS<imp-def,dead>
+ // insert => %reg1030<def> = MOV8rr %reg1029
+ // %reg1030<def> = ADD8rr %reg1029<kill>, %reg1028<kill>, %EFLAGS<imp-def,dead>
+
+ if (!MI->killsRegister(regC))
+ return false;
+
+ // Ok, we have something like:
+ // %reg1030<def> = ADD8rr %reg1028<kill>, %reg1029<kill>, %EFLAGS<imp-def,dead>
+ // let's see if it's worth commuting it.
+
+ // Look for situations like this:
+ // %reg1024<def> = MOV r1
+ // %reg1025<def> = MOV r0
+ // %reg1026<def> = 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) &&
+ (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<def> = MOV r1
+ // %reg1025<def> = MOV r0
+ // %reg1026<def> = 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<MachineInstr*, 8> &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<unsigned, 4> 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<MachineInstr*, unsigned>::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<unsigned, 4> &Kills) {
+ const TargetInstrDesc &TID = MI->getDesc();
+ if (TID.mayStore() || TID.isCall())
+ return false;
+ if (TID.isTerminator() || TID.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->modifiesRegister(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;
+}
+
+/// 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.
+ }
+ }
+ }
+ return false;
+}
+