/// Changes operand OpNum in MI the refer the PhysReg, considering subregs. This
/// may invalidate any operand pointers. Return true if the operand kills its
/// register.
bool RegAllocFast::setPhysReg(MachineInstr &MI, MachineOperand &MO,
MCPhysReg PhysReg) {
bool Dead = MO.isDead();
if (!MO.getSubReg()) {
MO.setReg(PhysReg);
MO.setIsRenamable(true);
return MO.isKill() || Dead;
}
// Handle subregister index.
MO.setReg(PhysReg ? TRI->getSubReg(PhysReg, MO.getSubReg()) : 0);
MO.setIsRenamable(true);
MO.setSubReg(0);
// A kill flag implies killing the full register. Add corresponding super
// register kill.
if (MO.isKill()) {
MI.addRegisterKilled(PhysReg, TRI, true);
return true;
}
// A <def,read-undef> of a sub-register requires an implicit def of the full
// register.
if (MO.isDef() && MO.isUndef())
MI.addRegisterDefined(PhysReg, TRI);
return Dead;
}
// Split MI into the comparison given by CompareOpcode followed
// a BRCL on the result.
void SystemZLongBranch::splitCompareBranch(MachineInstr *MI,
unsigned CompareOpcode) {
MachineBasicBlock *MBB = MI->getParent();
DebugLoc DL = MI->getDebugLoc();
BuildMI(*MBB, MI, DL, TII->get(CompareOpcode))
.addOperand(MI->getOperand(0))
.addOperand(MI->getOperand(1));
MachineInstr *BRCL = BuildMI(*MBB, MI, DL, TII->get(SystemZ::BRCL))
.addImm(SystemZ::CCMASK_ICMP)
.addOperand(MI->getOperand(2))
.addOperand(MI->getOperand(3));
// The implicit use of CC is a killing use.
BRCL->addRegisterKilled(SystemZ::CC, &TII->getRegisterInfo());
MI->eraseFromParent();
}
void VirtRegRewriter::rewrite() {
bool NoSubRegLiveness = !MRI->subRegLivenessEnabled();
SmallVector<unsigned, 8> SuperDeads;
SmallVector<unsigned, 8> SuperDefs;
SmallVector<unsigned, 8> SuperKills;
for (MachineFunction::iterator MBBI = MF->begin(), MBBE = MF->end();
MBBI != MBBE; ++MBBI) {
DEBUG(MBBI->print(dbgs(), Indexes));
for (MachineBasicBlock::instr_iterator
MII = MBBI->instr_begin(), MIE = MBBI->instr_end(); MII != MIE;) {
MachineInstr *MI = &*MII;
++MII;
for (MachineInstr::mop_iterator MOI = MI->operands_begin(),
MOE = MI->operands_end(); MOI != MOE; ++MOI) {
MachineOperand &MO = *MOI;
// Make sure MRI knows about registers clobbered by regmasks.
if (MO.isRegMask())
MRI->addPhysRegsUsedFromRegMask(MO.getRegMask());
if (!MO.isReg() || !TargetRegisterInfo::isVirtualRegister(MO.getReg()))
continue;
unsigned VirtReg = MO.getReg();
unsigned PhysReg = VRM->getPhys(VirtReg);
assert(PhysReg != VirtRegMap::NO_PHYS_REG &&
"Instruction uses unmapped VirtReg");
assert(!MRI->isReserved(PhysReg) && "Reserved register assignment");
// Preserve semantics of sub-register operands.
unsigned SubReg = MO.getSubReg();
if (SubReg != 0) {
if (NoSubRegLiveness) {
// A virtual register kill refers to the whole register, so we may
// have to add <imp-use,kill> operands for the super-register. A
// partial redef always kills and redefines the super-register.
if (MO.readsReg() && (MO.isDef() || MO.isKill()))
SuperKills.push_back(PhysReg);
if (MO.isDef()) {
// Also add implicit defs for the super-register.
if (MO.isDead())
SuperDeads.push_back(PhysReg);
else
SuperDefs.push_back(PhysReg);
}
} else {
if (MO.isUse()) {
if (readsUndefSubreg(MO))
// We need to add an <undef> flag if the subregister is
// completely undefined (and we are not adding super-register
// defs).
MO.setIsUndef(true);
} else if (!MO.isDead()) {
assert(MO.isDef());
}
}
// The <def,undef> flag only makes sense for sub-register defs, and
// we are substituting a full physreg. An <imp-use,kill> operand
// from the SuperKills list will represent the partial read of the
// super-register.
if (MO.isDef())
MO.setIsUndef(false);
// PhysReg operands cannot have subregister indexes.
PhysReg = TRI->getSubReg(PhysReg, SubReg);
assert(PhysReg && "Invalid SubReg for physical register");
MO.setSubReg(0);
}
// Rewrite. Note we could have used MachineOperand::substPhysReg(), but
// we need the inlining here.
MO.setReg(PhysReg);
}
// Add any missing super-register kills after rewriting the whole
// instruction.
while (!SuperKills.empty())
MI->addRegisterKilled(SuperKills.pop_back_val(), TRI, true);
while (!SuperDeads.empty())
MI->addRegisterDead(SuperDeads.pop_back_val(), TRI, true);
while (!SuperDefs.empty())
MI->addRegisterDefined(SuperDefs.pop_back_val(), TRI);
DEBUG(dbgs() << "> " << *MI);
// Finally, remove any identity copies.
if (MI->isIdentityCopy()) {
++NumIdCopies;
DEBUG(dbgs() << "Deleting identity copy.\n");
if (Indexes)
Indexes->removeMachineInstrFromMaps(*MI);
// It's safe to erase MI because MII has already been incremented.
MI->eraseFromParent();
}
}
}
}
void LiveIntervals::addKillFlags(const VirtRegMap *VRM) {
// Keep track of regunit ranges.
SmallVector<std::pair<const LiveRange*, LiveRange::const_iterator>, 8> RU;
// Keep track of subregister ranges.
SmallVector<std::pair<const LiveInterval::SubRange*,
LiveRange::const_iterator>, 4> SRs;
for (unsigned i = 0, e = MRI->getNumVirtRegs(); i != e; ++i) {
unsigned Reg = TargetRegisterInfo::index2VirtReg(i);
if (MRI->reg_nodbg_empty(Reg))
continue;
const LiveInterval &LI = getInterval(Reg);
if (LI.empty())
continue;
// Find the regunit intervals for the assigned register. They may overlap
// the virtual register live range, cancelling any kills.
RU.clear();
for (MCRegUnitIterator Units(VRM->getPhys(Reg), TRI); Units.isValid();
++Units) {
const LiveRange &RURange = getRegUnit(*Units);
if (RURange.empty())
continue;
RU.push_back(std::make_pair(&RURange, RURange.find(LI.begin()->end)));
}
if (MRI->tracksSubRegLiveness()) {
SRs.clear();
for (const LiveInterval::SubRange &SR : LI.subranges()) {
SRs.push_back(std::make_pair(&SR, SR.find(LI.begin()->end)));
}
}
// Every instruction that kills Reg corresponds to a segment range end
// point.
for (LiveInterval::const_iterator RI = LI.begin(), RE = LI.end(); RI != RE;
++RI) {
// A block index indicates an MBB edge.
if (RI->end.isBlock())
continue;
MachineInstr *MI = getInstructionFromIndex(RI->end);
if (!MI)
continue;
// Check if any of the regunits are live beyond the end of RI. That could
// happen when a physreg is defined as a copy of a virtreg:
//
// %EAX = COPY %vreg5
// FOO %vreg5 <--- MI, cancel kill because %EAX is live.
// BAR %EAX<kill>
//
// There should be no kill flag on FOO when %vreg5 is rewritten as %EAX.
for (auto &RUP : RU) {
const LiveRange &RURange = *RUP.first;
LiveRange::const_iterator &I = RUP.second;
if (I == RURange.end())
continue;
I = RURange.advanceTo(I, RI->end);
if (I == RURange.end() || I->start >= RI->end)
continue;
// I is overlapping RI.
goto CancelKill;
}
if (MRI->tracksSubRegLiveness()) {
// When reading a partial undefined value we must not add a kill flag.
// The regalloc might have used the undef lane for something else.
// Example:
// %vreg1 = ... ; R32: %vreg1
// %vreg2:high16 = ... ; R64: %vreg2
// = read %vreg2<kill> ; R64: %vreg2
// = read %vreg1 ; R32: %vreg1
// The <kill> flag is correct for %vreg2, but the register allocator may
// assign R0L to %vreg1, and R0 to %vreg2 because the low 32bits of R0
// are actually never written by %vreg2. After assignment the <kill>
// flag at the read instruction is invalid.
unsigned DefinedLanesMask;
if (!SRs.empty()) {
// Compute a mask of lanes that are defined.
DefinedLanesMask = 0;
for (auto &SRP : SRs) {
const LiveInterval::SubRange &SR = *SRP.first;
LiveRange::const_iterator &I = SRP.second;
if (I == SR.end())
continue;
I = SR.advanceTo(I, RI->end);
if (I == SR.end() || I->start >= RI->end)
continue;
// I is overlapping RI
DefinedLanesMask |= SR.LaneMask;
}
} else
DefinedLanesMask = ~0u;
bool IsFullWrite = false;
for (const MachineOperand &MO : MI->operands()) {
if (!MO.isReg() || MO.getReg() != Reg)
continue;
if (MO.isUse()) {
// Reading any undefined lanes?
unsigned UseMask = TRI->getSubRegIndexLaneMask(MO.getSubReg());
if ((UseMask & ~DefinedLanesMask) != 0)
goto CancelKill;
} else if (MO.getSubReg() == 0) {
// Writing to the full register?
assert(MO.isDef());
IsFullWrite = true;
}
}
// If an instruction writes to a subregister, a new segment starts in
// the LiveInterval. But as this is only overriding part of the register
// adding kill-flags is not correct here after registers have been
// assigned.
if (!IsFullWrite) {
// Next segment has to be adjacent in the subregister write case.
LiveRange::const_iterator N = std::next(RI);
if (N != LI.end() && N->start == RI->end)
goto CancelKill;
}
}
MI->addRegisterKilled(Reg, nullptr);
continue;
CancelKill:
MI->clearRegisterKills(Reg, nullptr);
}
}
}
void VirtRegRewriter::rewrite() {
SmallVector<unsigned, 8> SuperDeads;
SmallVector<unsigned, 8> SuperDefs;
SmallVector<unsigned, 8> SuperKills;
SmallPtrSet<const MachineInstr *, 4> NoReturnInsts;
// Here we have a SparseSet to hold which PhysRegs are actually encountered
// in the MF we are about to iterate over so that later when we call
// setPhysRegUsed, we are only doing it for physRegs that were actually found
// in the program and not for all of the possible physRegs for the given
// target architecture. If the target has a lot of physRegs, then for a small
// program there will be a significant compile time reduction here.
PhysRegs.clear();
PhysRegs.setUniverse(TRI->getNumRegs());
// The function with uwtable should guarantee that the stack unwinder
// can unwind the stack to the previous frame. Thus, we can't apply the
// noreturn optimization if the caller function has uwtable attribute.
bool HasUWTable = MF->getFunction()->hasFnAttribute(Attribute::UWTable);
for (MachineFunction::iterator MBBI = MF->begin(), MBBE = MF->end();
MBBI != MBBE; ++MBBI) {
DEBUG(MBBI->print(dbgs(), Indexes));
bool IsExitBB = MBBI->succ_empty();
for (MachineBasicBlock::instr_iterator
MII = MBBI->instr_begin(), MIE = MBBI->instr_end(); MII != MIE;) {
MachineInstr *MI = MII;
++MII;
// Check if this instruction is a call to a noreturn function. If this
// is a call to noreturn function and we don't need the stack unwinding
// functionality (i.e. this function does not have uwtable attribute and
// the callee function has the nounwind attribute), then we can ignore
// the definitions set by this instruction.
if (!HasUWTable && IsExitBB && MI->isCall()) {
for (MachineInstr::mop_iterator MOI = MI->operands_begin(),
MOE = MI->operands_end(); MOI != MOE; ++MOI) {
MachineOperand &MO = *MOI;
if (!MO.isGlobal())
continue;
const Function *Func = dyn_cast<Function>(MO.getGlobal());
if (!Func || !Func->hasFnAttribute(Attribute::NoReturn) ||
// We need to keep correct unwind information
// even if the function will not return, since the
// runtime may need it.
!Func->hasFnAttribute(Attribute::NoUnwind))
continue;
NoReturnInsts.insert(MI);
break;
}
}
for (MachineInstr::mop_iterator MOI = MI->operands_begin(),
MOE = MI->operands_end(); MOI != MOE; ++MOI) {
MachineOperand &MO = *MOI;
// Make sure MRI knows about registers clobbered by regmasks.
if (MO.isRegMask())
MRI->addPhysRegsUsedFromRegMask(MO.getRegMask());
// If we encounter a VirtReg or PhysReg then get at the PhysReg and add
// it to the physreg bitset. Later we use only the PhysRegs that were
// actually encountered in the MF to populate the MRI's used physregs.
if (MO.isReg() && MO.getReg())
PhysRegs.insert(
TargetRegisterInfo::isVirtualRegister(MO.getReg()) ?
VRM->getPhys(MO.getReg()) :
MO.getReg());
if (!MO.isReg() || !TargetRegisterInfo::isVirtualRegister(MO.getReg()))
continue;
unsigned VirtReg = MO.getReg();
unsigned PhysReg = VRM->getPhys(VirtReg);
assert(PhysReg != VirtRegMap::NO_PHYS_REG &&
"Instruction uses unmapped VirtReg");
assert(!MRI->isReserved(PhysReg) && "Reserved register assignment");
// Preserve semantics of sub-register operands.
if (MO.getSubReg()) {
// A virtual register kill refers to the whole register, so we may
// have to add <imp-use,kill> operands for the super-register. A
// partial redef always kills and redefines the super-register.
if (MO.readsReg() && (MO.isDef() || MO.isKill()))
SuperKills.push_back(PhysReg);
if (MO.isDef()) {
// The <def,undef> flag only makes sense for sub-register defs, and
// we are substituting a full physreg. An <imp-use,kill> operand
// from the SuperKills list will represent the partial read of the
// super-register.
MO.setIsUndef(false);
// Also add implicit defs for the super-register.
if (MO.isDead())
SuperDeads.push_back(PhysReg);
else
SuperDefs.push_back(PhysReg);
}
// PhysReg operands cannot have subregister indexes.
PhysReg = TRI->getSubReg(PhysReg, MO.getSubReg());
assert(PhysReg && "Invalid SubReg for physical register");
MO.setSubReg(0);
}
// Rewrite. Note we could have used MachineOperand::substPhysReg(), but
// we need the inlining here.
MO.setReg(PhysReg);
}
// Add any missing super-register kills after rewriting the whole
// instruction.
while (!SuperKills.empty())
MI->addRegisterKilled(SuperKills.pop_back_val(), TRI, true);
while (!SuperDeads.empty())
MI->addRegisterDead(SuperDeads.pop_back_val(), TRI, true);
while (!SuperDefs.empty())
MI->addRegisterDefined(SuperDefs.pop_back_val(), TRI);
DEBUG(dbgs() << "> " << *MI);
// Finally, remove any identity copies.
if (MI->isIdentityCopy()) {
++NumIdCopies;
if (MI->getNumOperands() == 2) {
DEBUG(dbgs() << "Deleting identity copy.\n");
if (Indexes)
Indexes->removeMachineInstrFromMaps(MI);
// It's safe to erase MI because MII has already been incremented.
MI->eraseFromParent();
} else {
// Transform identity copy to a KILL to deal with subregisters.
MI->setDesc(TII->get(TargetOpcode::KILL));
DEBUG(dbgs() << "Identity copy: " << *MI);
}
}
}
}
// Tell MRI about physical registers in use.
if (NoReturnInsts.empty()) {
for (SparseSet<unsigned>::iterator
RegI = PhysRegs.begin(), E = PhysRegs.end(); RegI != E; ++RegI)
if (!MRI->reg_nodbg_empty(*RegI))
MRI->setPhysRegUsed(*RegI);
} else {
for (SparseSet<unsigned>::iterator
I = PhysRegs.begin(), E = PhysRegs.end(); I != E; ++I) {
unsigned Reg = *I;
if (MRI->reg_nodbg_empty(Reg))
continue;
// Check if this register has a use that will impact the rest of the
// code. Uses in debug and noreturn instructions do not impact the
// generated code.
for (MachineInstr &It : MRI->reg_nodbg_instructions(Reg)) {
if (!NoReturnInsts.count(&It)) {
MRI->setPhysRegUsed(Reg);
break;
}
}
}
}
}
bool LiveVariables::HandlePhysRegKill(unsigned Reg, MachineInstr *MI) {
MachineInstr *LastDef = PhysRegDef[Reg];
MachineInstr *LastUse = PhysRegUse[Reg];
if (!LastDef && !LastUse)
return false;
MachineInstr *LastRefOrPartRef = LastUse ? LastUse : LastDef;
unsigned LastRefOrPartRefDist = DistanceMap[LastRefOrPartRef];
// The whole register is used.
// AL =
// AH =
//
// = AX
// = AL, AX<imp-use, kill>
// AX =
//
// Or whole register is defined, but not used at all.
// AX<dead> =
// ...
// AX =
//
// Or whole register is defined, but only partly used.
// AX<dead> = AL<imp-def>
// = AL<kill>
// AX =
MachineInstr *LastPartDef = nullptr;
unsigned LastPartDefDist = 0;
SmallSet<unsigned, 8> PartUses;
for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs) {
unsigned SubReg = *SubRegs;
MachineInstr *Def = PhysRegDef[SubReg];
if (Def && Def != LastDef) {
// There was a def of this sub-register in between. This is a partial
// def, keep track of the last one.
unsigned Dist = DistanceMap[Def];
if (Dist > LastPartDefDist) {
LastPartDefDist = Dist;
LastPartDef = Def;
}
continue;
}
if (MachineInstr *Use = PhysRegUse[SubReg]) {
for (MCSubRegIterator SS(SubReg, TRI, /*IncludeSelf=*/true); SS.isValid();
++SS)
PartUses.insert(*SS);
unsigned Dist = DistanceMap[Use];
if (Dist > LastRefOrPartRefDist) {
LastRefOrPartRefDist = Dist;
LastRefOrPartRef = Use;
}
}
}
if (!PhysRegUse[Reg]) {
// Partial uses. Mark register def dead and add implicit def of
// sub-registers which are used.
// EAX<dead> = op AL<imp-def>
// That is, EAX def is dead but AL def extends pass it.
PhysRegDef[Reg]->addRegisterDead(Reg, TRI, true);
for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs) {
unsigned SubReg = *SubRegs;
if (!PartUses.count(SubReg))
continue;
bool NeedDef = true;
if (PhysRegDef[Reg] == PhysRegDef[SubReg]) {
MachineOperand *MO = PhysRegDef[Reg]->findRegisterDefOperand(SubReg);
if (MO) {
NeedDef = false;
assert(!MO->isDead());
}
}
if (NeedDef)
PhysRegDef[Reg]->addOperand(MachineOperand::CreateReg(SubReg,
true/*IsDef*/, true/*IsImp*/));
MachineInstr *LastSubRef = FindLastRefOrPartRef(SubReg);
if (LastSubRef)
LastSubRef->addRegisterKilled(SubReg, TRI, true);
else {
LastRefOrPartRef->addRegisterKilled(SubReg, TRI, true);
for (MCSubRegIterator SS(SubReg, TRI, /*IncludeSelf=*/true);
SS.isValid(); ++SS)
PhysRegUse[*SS] = LastRefOrPartRef;
}
for (MCSubRegIterator SS(SubReg, TRI); SS.isValid(); ++SS)
PartUses.erase(*SS);
}
} else if (LastRefOrPartRef == PhysRegDef[Reg] && LastRefOrPartRef != MI) {
if (LastPartDef)
// The last partial def kills the register.
LastPartDef->addOperand(MachineOperand::CreateReg(Reg, false/*IsDef*/,
true/*IsImp*/, true/*IsKill*/));
else {
MachineOperand *MO =
LastRefOrPartRef->findRegisterDefOperand(Reg, false, TRI);
bool NeedEC = MO->isEarlyClobber() && MO->getReg() != Reg;
// If the last reference is the last def, then it's not used at all.
// That is, unless we are currently processing the last reference itself.
LastRefOrPartRef->addRegisterDead(Reg, TRI, true);
if (NeedEC) {
// If we are adding a subreg def and the superreg def is marked early
// clobber, add an early clobber marker to the subreg def.
MO = LastRefOrPartRef->findRegisterDefOperand(Reg);
if (MO)
MO->setIsEarlyClobber();
}
}
} else
LastRefOrPartRef->addRegisterKilled(Reg, TRI, true);
return true;
}
void LiveIntervals::addKillFlags(const VirtRegMap *VRM) {
// Keep track of regunit ranges.
SmallVector<std::pair<LiveInterval*, LiveInterval::iterator>, 8> RU;
for (unsigned i = 0, e = MRI->getNumVirtRegs(); i != e; ++i) {
unsigned Reg = TargetRegisterInfo::index2VirtReg(i);
if (MRI->reg_nodbg_empty(Reg))
continue;
LiveInterval *LI = &getInterval(Reg);
if (LI->empty())
continue;
// Find the regunit intervals for the assigned register. They may overlap
// the virtual register live range, cancelling any kills.
RU.clear();
for (MCRegUnitIterator Units(VRM->getPhys(Reg), TRI); Units.isValid();
++Units) {
LiveInterval *RUInt = &getRegUnit(*Units);
if (RUInt->empty())
continue;
RU.push_back(std::make_pair(RUInt, RUInt->find(LI->begin()->end)));
}
// Every instruction that kills Reg corresponds to a live range end point.
for (LiveInterval::iterator RI = LI->begin(), RE = LI->end(); RI != RE;
++RI) {
// A block index indicates an MBB edge.
if (RI->end.isBlock())
continue;
MachineInstr *MI = getInstructionFromIndex(RI->end);
if (!MI)
continue;
// Check if any of the regunits are live beyond the end of RI. That could
// happen when a physreg is defined as a copy of a virtreg:
//
// %EAX = COPY %vreg5
// FOO %vreg5 <--- MI, cancel kill because %EAX is live.
// BAR %EAX<kill>
//
// There should be no kill flag on FOO when %vreg5 is rewritten as %EAX.
bool CancelKill = false;
for (unsigned u = 0, e = RU.size(); u != e; ++u) {
LiveInterval *RInt = RU[u].first;
LiveInterval::iterator &I = RU[u].second;
if (I == RInt->end())
continue;
I = RInt->advanceTo(I, RI->end);
if (I == RInt->end() || I->start >= RI->end)
continue;
// I is overlapping RI.
CancelKill = true;
break;
}
if (CancelKill)
MI->clearRegisterKills(Reg, NULL);
else
MI->addRegisterKilled(Reg, NULL);
}
}
}
/// isSafeToMoveTogether - Returns true if it is safe to move I1 next to I2 such
/// that the two instructions can be paired in a combine.
bool HexagonCopyToCombine::isSafeToMoveTogether(MachineInstr *I1,
MachineInstr *I2,
unsigned I1DestReg,
unsigned I2DestReg,
bool &DoInsertAtI1) {
unsigned I2UseReg = UseReg(I2->getOperand(1));
// It is not safe to move I1 and I2 into one combine if I2 has a true
// dependence on I1.
if (I2UseReg && I1->modifiesRegister(I2UseReg, TRI))
return false;
bool isSafe = true;
// First try to move I2 towards I1.
{
// A reverse_iterator instantiated like below starts before I2, and I1
// respectively.
// Look at instructions I in between I2 and (excluding) I1.
MachineBasicBlock::reverse_iterator I(I2),
End = --(MachineBasicBlock::reverse_iterator(I1));
// At 03 we got better results (dhrystone!) by being more conservative.
if (!ShouldCombineAggressively)
End = MachineBasicBlock::reverse_iterator(I1);
// If I2 kills its operand and we move I2 over an instruction that also
// uses I2's use reg we need to modify that (first) instruction to now kill
// this reg.
unsigned KilledOperand = 0;
if (I2->killsRegister(I2UseReg))
KilledOperand = I2UseReg;
MachineInstr *KillingInstr = nullptr;
for (; I != End; ++I) {
// If the intervening instruction I:
// * modifies I2's use reg
// * modifies I2's def reg
// * reads I2's def reg
// * or has unmodelled side effects
// we can't move I2 across it.
if (isUnsafeToMoveAcross(&*I, I2UseReg, I2DestReg, TRI)) {
isSafe = false;
break;
}
// Update first use of the killed operand.
if (!KillingInstr && KilledOperand &&
I->readsRegister(KilledOperand, TRI))
KillingInstr = &*I;
}
if (isSafe) {
// Update the intermediate instruction to with the kill flag.
if (KillingInstr) {
bool Added = KillingInstr->addRegisterKilled(KilledOperand, TRI, true);
(void)Added; // suppress compiler warning
assert(Added && "Must successfully update kill flag");
removeKillInfo(I2, KilledOperand);
}
DoInsertAtI1 = true;
return true;
}
}
// Try to move I1 towards I2.
{
// Look at instructions I in between I1 and (excluding) I2.
MachineBasicBlock::iterator I(I1), End(I2);
// At O3 we got better results (dhrystone) by being more conservative here.
if (!ShouldCombineAggressively)
End = std::next(MachineBasicBlock::iterator(I2));
unsigned I1UseReg = UseReg(I1->getOperand(1));
// Track killed operands. If we move across an instruction that kills our
// operand, we need to update the kill information on the moved I1. It kills
// the operand now.
MachineInstr *KillingInstr = nullptr;
unsigned KilledOperand = 0;
while(++I != End) {
// If the intervening instruction I:
// * modifies I1's use reg
// * modifies I1's def reg
// * reads I1's def reg
// * or has unmodelled side effects
// We introduce this special case because llvm has no api to remove a
// kill flag for a register (a removeRegisterKilled() analogous to
// addRegisterKilled) that handles aliased register correctly.
// * or has a killed aliased register use of I1's use reg
// %D4<def> = TFRI64 16
// %R6<def> = TFR %R9
// %R8<def> = KILL %R8, %D4<imp-use,kill>
// If we want to move R6 = across the KILL instruction we would have
// to remove the %D4<imp-use,kill> operand. For now, we are
// conservative and disallow the move.
// we can't move I1 across it.
if (isUnsafeToMoveAcross(I, I1UseReg, I1DestReg, TRI) ||
// Check for an aliased register kill. Bail out if we see one.
(!I->killsRegister(I1UseReg) && I->killsRegister(I1UseReg, TRI)))
return false;
// Check for an exact kill (registers match).
if (I1UseReg && I->killsRegister(I1UseReg)) {
assert(!KillingInstr && "Should only see one killing instruction");
KilledOperand = I1UseReg;
KillingInstr = &*I;
}
}
if (KillingInstr) {
removeKillInfo(KillingInstr, KilledOperand);
// Update I1 to set the kill flag. This flag will later be picked up by
// the new COMBINE instruction.
bool Added = I1->addRegisterKilled(KilledOperand, TRI);
(void)Added; // suppress compiler warning
assert(Added && "Must successfully update kill flag");
}
DoInsertAtI1 = false;
}
return true;
}
bool LiveVariables::HandlePhysRegKill(unsigned Reg, MachineInstr *MI) {
if (!PhysRegUse[Reg] && !PhysRegDef[Reg])
return false;
MachineInstr *LastRefOrPartRef = PhysRegUse[Reg]
? PhysRegUse[Reg] : PhysRegDef[Reg];
unsigned LastRefOrPartRefDist = DistanceMap[LastRefOrPartRef];
// The whole register is used.
// AL =
// AH =
//
// = AX
// = AL, AX<imp-use, kill>
// AX =
//
// Or whole register is defined, but not used at all.
// AX<dead> =
// ...
// AX =
//
// Or whole register is defined, but only partly used.
// AX<dead> = AL<imp-def>
// = AL<kill>
// AX =
SmallSet<unsigned, 8> PartUses;
for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
unsigned SubReg = *SubRegs; ++SubRegs) {
if (MachineInstr *Use = PhysRegUse[SubReg]) {
PartUses.insert(SubReg);
for (const unsigned *SS = TRI->getSubRegisters(SubReg); *SS; ++SS)
PartUses.insert(*SS);
unsigned Dist = DistanceMap[Use];
if (Dist > LastRefOrPartRefDist) {
LastRefOrPartRefDist = Dist;
LastRefOrPartRef = Use;
}
}
}
if (LastRefOrPartRef == PhysRegDef[Reg] && LastRefOrPartRef != MI)
// If the last reference is the last def, then it's not used at all.
// That is, unless we are currently processing the last reference itself.
LastRefOrPartRef->addRegisterDead(Reg, TRI, true);
/* Partial uses. Mark register def dead and add implicit def of
sub-registers which are used.
FIXME: LiveIntervalAnalysis can't handle this yet!
EAX<dead> = op AL<imp-def>
That is, EAX def is dead but AL def extends pass it.
Enable this after live interval analysis is fixed to improve codegen!
else if (!PhysRegUse[Reg]) {
PhysRegDef[Reg]->addRegisterDead(Reg, TRI, true);
for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
unsigned SubReg = *SubRegs; ++SubRegs) {
if (PartUses.count(SubReg)) {
PhysRegDef[Reg]->addOperand(MachineOperand::CreateReg(SubReg,
true, true));
LastRefOrPartRef->addRegisterKilled(SubReg, TRI, true);
for (const unsigned *SS = TRI->getSubRegisters(SubReg); *SS; ++SS)
PartUses.erase(*SS);
}
}
} */
else
LastRefOrPartRef->addRegisterKilled(Reg, TRI, true);
return true;
}
void Mos6502InstrInfo::copyPhysReg(MachineBasicBlock &MBB,
MachineBasicBlock::iterator I, DebugLoc DL,
unsigned DestReg, unsigned SrcReg,
bool KillSrc) const {
unsigned numSubRegs = 0;
unsigned movOpc = 0;
const unsigned *subRegIdx = nullptr;
const unsigned DFP_FP_SubRegsIdx[] = { M6502::sub_even, M6502::sub_odd };
const unsigned QFP_DFP_SubRegsIdx[] = { M6502::sub_even64, M6502::sub_odd64 };
const unsigned QFP_FP_SubRegsIdx[] = { M6502::sub_even, M6502::sub_odd,
M6502::sub_odd64_then_sub_even,
M6502::sub_odd64_then_sub_odd };
if (M6502::IntRegsRegClass.contains(DestReg, SrcReg))
BuildMI(MBB, I, DL, get(M6502::ORrr), DestReg).addReg(M6502::G0)
.addReg(SrcReg, getKillRegState(KillSrc));
else if (M6502::FPRegsRegClass.contains(DestReg, SrcReg))
BuildMI(MBB, I, DL, get(M6502::FMOVS), DestReg)
.addReg(SrcReg, getKillRegState(KillSrc));
else if (M6502::DFPRegsRegClass.contains(DestReg, SrcReg)) {
if (Subtarget.isV9()) {
BuildMI(MBB, I, DL, get(M6502::FMOVD), DestReg)
.addReg(SrcReg, getKillRegState(KillSrc));
} else {
// Use two FMOVS instructions.
subRegIdx = DFP_FP_SubRegsIdx;
numSubRegs = 2;
movOpc = M6502::FMOVS;
}
} else if (M6502::QFPRegsRegClass.contains(DestReg, SrcReg)) {
if (Subtarget.isV9()) {
if (Subtarget.hasHardQuad()) {
BuildMI(MBB, I, DL, get(M6502::FMOVQ), DestReg)
.addReg(SrcReg, getKillRegState(KillSrc));
} else {
// Use two FMOVD instructions.
subRegIdx = QFP_DFP_SubRegsIdx;
numSubRegs = 2;
movOpc = M6502::FMOVD;
}
} else {
// Use four FMOVS instructions.
subRegIdx = QFP_FP_SubRegsIdx;
numSubRegs = 4;
movOpc = M6502::FMOVS;
}
} else if (M6502::ASRRegsRegClass.contains(DestReg) &&
M6502::IntRegsRegClass.contains(SrcReg)) {
BuildMI(MBB, I, DL, get(M6502::WRASRrr), DestReg)
.addReg(M6502::G0)
.addReg(SrcReg, getKillRegState(KillSrc));
} else if (M6502::IntRegsRegClass.contains(DestReg) &&
M6502::ASRRegsRegClass.contains(SrcReg)) {
BuildMI(MBB, I, DL, get(M6502::RDASR), DestReg)
.addReg(SrcReg, getKillRegState(KillSrc));
} else
llvm_unreachable("Impossible reg-to-reg copy");
if (numSubRegs == 0 || subRegIdx == nullptr || movOpc == 0)
return;
const TargetRegisterInfo *TRI = &getRegisterInfo();
MachineInstr *MovMI = nullptr;
for (unsigned i = 0; i != numSubRegs; ++i) {
unsigned Dst = TRI->getSubReg(DestReg, subRegIdx[i]);
unsigned Src = TRI->getSubReg(SrcReg, subRegIdx[i]);
assert(Dst && Src && "Bad sub-register");
MovMI = BuildMI(MBB, I, DL, get(movOpc), Dst).addReg(Src);
}
// Add implicit super-register defs and kills to the last MovMI.
MovMI->addRegisterDefined(DestReg, TRI);
if (KillSrc)
MovMI->addRegisterKilled(SrcReg, TRI);
}
void VirtRegMap::rewrite(SlotIndexes *Indexes) {
DEBUG(dbgs() << "********** REWRITE VIRTUAL REGISTERS **********\n"
<< "********** Function: "
<< MF->getFunction()->getName() << '\n');
DEBUG(dump());
SmallVector<unsigned, 8> SuperDeads;
SmallVector<unsigned, 8> SuperDefs;
SmallVector<unsigned, 8> SuperKills;
for (MachineFunction::iterator MBBI = MF->begin(), MBBE = MF->end();
MBBI != MBBE; ++MBBI) {
DEBUG(MBBI->print(dbgs(), Indexes));
for (MachineBasicBlock::iterator MII = MBBI->begin(), MIE = MBBI->end();
MII != MIE;) {
MachineInstr *MI = MII;
++MII;
for (MachineInstr::mop_iterator MOI = MI->operands_begin(),
MOE = MI->operands_end(); MOI != MOE; ++MOI) {
MachineOperand &MO = *MOI;
if (!MO.isReg() || !TargetRegisterInfo::isVirtualRegister(MO.getReg()))
continue;
unsigned VirtReg = MO.getReg();
unsigned PhysReg = getPhys(VirtReg);
assert(PhysReg != NO_PHYS_REG && "Instruction uses unmapped VirtReg");
// Preserve semantics of sub-register operands.
if (MO.getSubReg()) {
// A virtual register kill refers to the whole register, so we may
// have to add <imp-use,kill> operands for the super-register. A
// partial redef always kills and redefines the super-register.
if (MO.readsReg() && (MO.isDef() || MO.isKill()))
SuperKills.push_back(PhysReg);
if (MO.isDef()) {
// The <def,undef> flag only makes sense for sub-register defs, and
// we are substituting a full physreg. An <imp-use,kill> operand
// from the SuperKills list will represent the partial read of the
// super-register.
MO.setIsUndef(false);
// Also add implicit defs for the super-register.
if (MO.isDead())
SuperDeads.push_back(PhysReg);
else
SuperDefs.push_back(PhysReg);
}
// PhysReg operands cannot have subregister indexes.
PhysReg = TRI->getSubReg(PhysReg, MO.getSubReg());
assert(PhysReg && "Invalid SubReg for physical register");
MO.setSubReg(0);
}
// Rewrite. Note we could have used MachineOperand::substPhysReg(), but
// we need the inlining here.
MO.setReg(PhysReg);
}
// Add any missing super-register kills after rewriting the whole
// instruction.
while (!SuperKills.empty())
MI->addRegisterKilled(SuperKills.pop_back_val(), TRI, true);
while (!SuperDeads.empty())
MI->addRegisterDead(SuperDeads.pop_back_val(), TRI, true);
while (!SuperDefs.empty())
MI->addRegisterDefined(SuperDefs.pop_back_val(), TRI);
DEBUG(dbgs() << "> " << *MI);
// Finally, remove any identity copies.
if (MI->isIdentityCopy()) {
++NumIdCopies;
if (MI->getNumOperands() == 2) {
DEBUG(dbgs() << "Deleting identity copy.\n");
RemoveMachineInstrFromMaps(MI);
if (Indexes)
Indexes->removeMachineInstrFromMaps(MI);
// It's safe to erase MI because MII has already been incremented.
MI->eraseFromParent();
} else {
// Transform identity copy to a KILL to deal with subregisters.
MI->setDesc(TII->get(TargetOpcode::KILL));
DEBUG(dbgs() << "Identity copy: " << *MI);
}
}
}
}
// Tell MRI about physical registers in use.
for (unsigned Reg = 1, RegE = TRI->getNumRegs(); Reg != RegE; ++Reg)
if (!MRI->reg_nodbg_empty(Reg))
MRI->setPhysRegUsed(Reg);
}
void RAFast::AllocateBasicBlock() {
DEBUG(dbgs() << "\nAllocating " << *MBB);
// FIXME: This should probably be added by instruction selection instead?
// If the last instruction in the block is a return, make sure to mark it as
// using all of the live-out values in the function. Things marked both call
// and return are tail calls; do not do this for them. The tail callee need
// not take the same registers as input that it produces as output, and there
// are dependencies for its input registers elsewhere.
if (!MBB->empty() && MBB->back().getDesc().isReturn() &&
!MBB->back().getDesc().isCall()) {
MachineInstr *Ret = &MBB->back();
for (MachineRegisterInfo::liveout_iterator
I = MF->getRegInfo().liveout_begin(),
E = MF->getRegInfo().liveout_end(); I != E; ++I) {
assert(TargetRegisterInfo::isPhysicalRegister(*I) &&
"Cannot have a live-out virtual register.");
// Add live-out registers as implicit uses.
Ret->addRegisterKilled(*I, TRI, true);
}
}
PhysRegState.assign(TRI->getNumRegs(), regDisabled);
assert(LiveVirtRegs.empty() && "Mapping not cleared form last block?");
MachineBasicBlock::iterator MII = MBB->begin();
// Add live-in registers as live.
for (MachineBasicBlock::livein_iterator I = MBB->livein_begin(),
E = MBB->livein_end(); I != E; ++I)
if (Allocatable.test(*I))
definePhysReg(MII, *I, regReserved);
SmallVector<unsigned, 8> VirtDead;
SmallVector<MachineInstr*, 32> Coalesced;
// Otherwise, sequentially allocate each instruction in the MBB.
while (MII != MBB->end()) {
MachineInstr *MI = MII++;
const TargetInstrDesc &TID = MI->getDesc();
DEBUG({
dbgs() << "\n>> " << *MI << "Regs:";
for (unsigned Reg = 1, E = TRI->getNumRegs(); Reg != E; ++Reg) {
if (PhysRegState[Reg] == regDisabled) continue;
dbgs() << " " << TRI->getName(Reg);
switch(PhysRegState[Reg]) {
case regFree:
break;
case regReserved:
dbgs() << "*";
break;
default:
dbgs() << '=' << PrintReg(PhysRegState[Reg]);
if (LiveVirtRegs[PhysRegState[Reg]].Dirty)
dbgs() << "*";
assert(LiveVirtRegs[PhysRegState[Reg]].PhysReg == Reg &&
"Bad inverse map");
break;
}
}
dbgs() << '\n';
// Check that LiveVirtRegs is the inverse.
for (LiveRegMap::iterator i = LiveVirtRegs.begin(),
e = LiveVirtRegs.end(); i != e; ++i) {
assert(TargetRegisterInfo::isVirtualRegister(i->first) &&
"Bad map key");
assert(TargetRegisterInfo::isPhysicalRegister(i->second.PhysReg) &&
"Bad map value");
assert(PhysRegState[i->second.PhysReg] == i->first &&
"Bad inverse map");
}
});
// Debug values are not allowed to change codegen in any way.
if (MI->isDebugValue()) {
bool ScanDbgValue = true;
while (ScanDbgValue) {
ScanDbgValue = false;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg()) continue;
unsigned Reg = MO.getReg();
if (!TargetRegisterInfo::isVirtualRegister(Reg)) continue;
LiveDbgValueMap[Reg] = MI;
LiveRegMap::iterator LRI = LiveVirtRegs.find(Reg);
if (LRI != LiveVirtRegs.end())
setPhysReg(MI, i, LRI->second.PhysReg);
else {
int SS = StackSlotForVirtReg[Reg];
if (SS == -1) {
// We can't allocate a physreg for a DebugValue, sorry!
DEBUG(dbgs() << "Unable to allocate vreg used by DBG_VALUE");
MO.setReg(0);
}
else {
// Modify DBG_VALUE now that the value is in a spill slot.
int64_t Offset = MI->getOperand(1).getImm();
const MDNode *MDPtr =
MI->getOperand(MI->getNumOperands()-1).getMetadata();
DebugLoc DL = MI->getDebugLoc();
if (MachineInstr *NewDV =
TII->emitFrameIndexDebugValue(*MF, SS, Offset, MDPtr, DL)) {
DEBUG(dbgs() << "Modifying debug info due to spill:" <<
"\t" << *MI);
MachineBasicBlock *MBB = MI->getParent();
MBB->insert(MBB->erase(MI), NewDV);
// Scan NewDV operands from the beginning.
MI = NewDV;
ScanDbgValue = true;
break;
} else {
// We can't allocate a physreg for a DebugValue; sorry!
DEBUG(dbgs() << "Unable to allocate vreg used by DBG_VALUE");
MO.setReg(0);
}
}
}
}
}
// Next instruction.
continue;
}
// If this is a copy, we may be able to coalesce.
unsigned CopySrc = 0, CopyDst = 0, CopySrcSub = 0, CopyDstSub = 0;
if (MI->isCopy()) {
CopyDst = MI->getOperand(0).getReg();
CopySrc = MI->getOperand(1).getReg();
CopyDstSub = MI->getOperand(0).getSubReg();
CopySrcSub = MI->getOperand(1).getSubReg();
}
// Track registers used by instruction.
UsedInInstr.reset();
// First scan.
// Mark physreg uses and early clobbers as used.
// Find the end of the virtreg operands
unsigned VirtOpEnd = 0;
bool hasTiedOps = false;
bool hasEarlyClobbers = false;
bool hasPartialRedefs = false;
bool hasPhysDefs = false;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg()) continue;
unsigned Reg = MO.getReg();
if (!Reg) continue;
if (TargetRegisterInfo::isVirtualRegister(Reg)) {
VirtOpEnd = i+1;
if (MO.isUse()) {
hasTiedOps = hasTiedOps ||
TID.getOperandConstraint(i, TOI::TIED_TO) != -1;
} else {
if (MO.isEarlyClobber())
hasEarlyClobbers = true;
if (MO.getSubReg() && MI->readsVirtualRegister(Reg))
hasPartialRedefs = true;
}
continue;
}
if (!Allocatable.test(Reg)) continue;
if (MO.isUse()) {
usePhysReg(MO);
} else if (MO.isEarlyClobber()) {
definePhysReg(MI, Reg, (MO.isImplicit() || MO.isDead()) ?
regFree : regReserved);
hasEarlyClobbers = true;
} else
hasPhysDefs = true;
}
// The instruction may have virtual register operands that must be allocated
// the same register at use-time and def-time: early clobbers and tied
// operands. If there are also physical defs, these registers must avoid
// both physical defs and uses, making them more constrained than normal
// operands.
// Similarly, if there are multiple defs and tied operands, we must make
// sure the same register is allocated to uses and defs.
// We didn't detect inline asm tied operands above, so just make this extra
// pass for all inline asm.
if (MI->isInlineAsm() || hasEarlyClobbers || hasPartialRedefs ||
(hasTiedOps && (hasPhysDefs || TID.getNumDefs() > 1))) {
handleThroughOperands(MI, VirtDead);
// Don't attempt coalescing when we have funny stuff going on.
CopyDst = 0;
// Pretend we have early clobbers so the use operands get marked below.
// This is not necessary for the common case of a single tied use.
hasEarlyClobbers = true;
}
// Second scan.
// Allocate virtreg uses.
for (unsigned i = 0; i != VirtOpEnd; ++i) {
MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg()) continue;
unsigned Reg = MO.getReg();
if (!TargetRegisterInfo::isVirtualRegister(Reg)) continue;
if (MO.isUse()) {
LiveRegMap::iterator LRI = reloadVirtReg(MI, i, Reg, CopyDst);
unsigned PhysReg = LRI->second.PhysReg;
CopySrc = (CopySrc == Reg || CopySrc == PhysReg) ? PhysReg : 0;
if (setPhysReg(MI, i, PhysReg))
killVirtReg(LRI);
}
}
MRI->addPhysRegsUsed(UsedInInstr);
// Track registers defined by instruction - early clobbers and tied uses at
// this point.
UsedInInstr.reset();
if (hasEarlyClobbers) {
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg()) continue;
unsigned Reg = MO.getReg();
if (!Reg || !TargetRegisterInfo::isPhysicalRegister(Reg)) continue;
// Look for physreg defs and tied uses.
if (!MO.isDef() && !MI->isRegTiedToDefOperand(i)) continue;
UsedInInstr.set(Reg);
for (const unsigned *AS = TRI->getAliasSet(Reg); *AS; ++AS)
UsedInInstr.set(*AS);
}
}
unsigned DefOpEnd = MI->getNumOperands();
if (TID.isCall()) {
// Spill all virtregs before a call. This serves two purposes: 1. If an
// exception is thrown, the landing pad is going to expect to find
// registers in their spill slots, and 2. we don't have to wade through
// all the <imp-def> operands on the call instruction.
DefOpEnd = VirtOpEnd;
DEBUG(dbgs() << " Spilling remaining registers before call.\n");
spillAll(MI);
// The imp-defs are skipped below, but we still need to mark those
// registers as used by the function.
SkippedInstrs.insert(&TID);
}
// Third scan.
// Allocate defs and collect dead defs.
for (unsigned i = 0; i != DefOpEnd; ++i) {
MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg() || !MO.isDef() || !MO.getReg() || MO.isEarlyClobber())
continue;
unsigned Reg = MO.getReg();
if (TargetRegisterInfo::isPhysicalRegister(Reg)) {
if (!Allocatable.test(Reg)) continue;
definePhysReg(MI, Reg, (MO.isImplicit() || MO.isDead()) ?
regFree : regReserved);
continue;
}
LiveRegMap::iterator LRI = defineVirtReg(MI, i, Reg, CopySrc);
unsigned PhysReg = LRI->second.PhysReg;
if (setPhysReg(MI, i, PhysReg)) {
VirtDead.push_back(Reg);
CopyDst = 0; // cancel coalescing;
} else
CopyDst = (CopyDst == Reg || CopyDst == PhysReg) ? PhysReg : 0;
}
// Kill dead defs after the scan to ensure that multiple defs of the same
// register are allocated identically. We didn't need to do this for uses
// because we are crerating our own kill flags, and they are always at the
// last use.
for (unsigned i = 0, e = VirtDead.size(); i != e; ++i)
killVirtReg(VirtDead[i]);
VirtDead.clear();
MRI->addPhysRegsUsed(UsedInInstr);
if (CopyDst && CopyDst == CopySrc && CopyDstSub == CopySrcSub) {
DEBUG(dbgs() << "-- coalescing: " << *MI);
Coalesced.push_back(MI);
} else {
DEBUG(dbgs() << "<< " << *MI);
}
}
// Replace uses of FromReg with ToReg if they are dominated by MI.
static bool ReplaceDominatedUses(MachineBasicBlock &MBB, MachineInstr &MI,
unsigned FromReg, unsigned ToReg,
const MachineRegisterInfo &MRI,
MachineDominatorTree &MDT,
LiveIntervals &LIS) {
bool Changed = false;
LiveInterval *FromLI = &LIS.getInterval(FromReg);
LiveInterval *ToLI = &LIS.getInterval(ToReg);
SlotIndex FromIdx = LIS.getInstructionIndex(MI).getRegSlot();
VNInfo *FromVNI = FromLI->getVNInfoAt(FromIdx);
SmallVector<SlotIndex, 4> Indices;
for (auto I = MRI.use_nodbg_begin(FromReg), E = MRI.use_nodbg_end();
I != E;) {
MachineOperand &O = *I++;
MachineInstr *Where = O.getParent();
// Check that MI dominates the instruction in the normal way.
if (&MI == Where || !MDT.dominates(&MI, Where))
continue;
// If this use gets a different value, skip it.
SlotIndex WhereIdx = LIS.getInstructionIndex(*Where);
VNInfo *WhereVNI = FromLI->getVNInfoAt(WhereIdx);
if (WhereVNI && WhereVNI != FromVNI)
continue;
// Make sure ToReg isn't clobbered before it gets there.
VNInfo *ToVNI = ToLI->getVNInfoAt(WhereIdx);
if (ToVNI && ToVNI != FromVNI)
continue;
Changed = true;
LLVM_DEBUG(dbgs() << "Setting operand " << O << " in " << *Where << " from "
<< MI << "\n");
O.setReg(ToReg);
// If the store's def was previously dead, it is no longer.
if (!O.isUndef()) {
MI.getOperand(0).setIsDead(false);
Indices.push_back(WhereIdx.getRegSlot());
}
}
if (Changed) {
// Extend ToReg's liveness.
LIS.extendToIndices(*ToLI, Indices);
// Shrink FromReg's liveness.
LIS.shrinkToUses(FromLI);
// If we replaced all dominated uses, FromReg is now killed at MI.
if (!FromLI->liveAt(FromIdx.getDeadSlot()))
MI.addRegisterKilled(FromReg, MBB.getParent()
->getSubtarget<WebAssemblySubtarget>()
.getRegisterInfo());
}
return Changed;
}