/// isDead returns true if the instruction is dead
/// (this was essentially copied from DeadMachineInstructionElim::isDead, but
/// with special cases for inline asm, physical registers and instructions with
/// side effects removed)
bool PPCCTRLoops::isDead(const MachineInstr *MI,
SmallVector<MachineInstr *, 1> &DeadPhis) const {
// Examine each operand.
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = MI->getOperand(i);
if (MO.isReg() && MO.isDef()) {
unsigned Reg = MO.getReg();
if (!MRI->use_nodbg_empty(Reg)) {
// This instruction has users, but if the only user is the phi node for
// the parent block, and the only use of that phi node is this
// instruction, then this instruction is dead: both it (and the phi
// node) can be removed.
MachineRegisterInfo::use_iterator I = MRI->use_begin(Reg);
if (llvm::next(I) == MRI->use_end() &&
I.getOperand().getParent()->isPHI()) {
MachineInstr *OnePhi = I.getOperand().getParent();
for (unsigned j = 0, f = OnePhi->getNumOperands(); j != f; ++j) {
const MachineOperand &OPO = OnePhi->getOperand(j);
if (OPO.isReg() && OPO.isDef()) {
unsigned OPReg = OPO.getReg();
MachineRegisterInfo::use_iterator nextJ;
for (MachineRegisterInfo::use_iterator J = MRI->use_begin(OPReg),
E = MRI->use_end(); J!=E; J=nextJ) {
nextJ = llvm::next(J);
MachineOperand& Use = J.getOperand();
MachineInstr *UseMI = Use.getParent();
if (MI != UseMI) {
// The phi node has a user that is not MI, bail...
return false;
}
}
}
}
DeadPhis.push_back(OnePhi);
} else {
// This def has a non-debug use. Don't delete the instruction!
return false;
}
}
}
}
// If there are no defs with uses, the instruction is dead.
return true;
}
void PPCCTRLoops::removeIfDead(MachineInstr *MI) {
// This procedure was essentially copied from DeadMachineInstructionElim
SmallVector<MachineInstr *, 1> DeadPhis;
if (isDead(MI, DeadPhis)) {
DEBUG(dbgs() << "CTR looping will remove: " << *MI);
// It is possible that some DBG_VALUE instructions refer to this
// instruction. Examine each def operand for such references;
// if found, mark the DBG_VALUE as undef (but don't delete it).
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg() || !MO.isDef())
continue;
unsigned Reg = MO.getReg();
MachineRegisterInfo::use_iterator nextI;
for (MachineRegisterInfo::use_iterator I = MRI->use_begin(Reg),
E = MRI->use_end(); I!=E; I=nextI) {
nextI = llvm::next(I); // I is invalidated by the setReg
MachineOperand& Use = I.getOperand();
MachineInstr *UseMI = Use.getParent();
if (UseMI==MI)
continue;
if (Use.isDebug()) // this might also be a instr -> phi -> instr case
// which can also be removed.
UseMI->getOperand(0).setReg(0U);
}
}
MI->eraseFromParent();
for (unsigned i = 0; i < DeadPhis.size(); ++i) {
DeadPhis[i]->eraseFromParent();
}
}
}
/// isLiveInButUnusedBefore - Return true if register is livein the MBB not
/// not used before it reaches the MI that defines register.
static bool isLiveInButUnusedBefore(unsigned Reg, MachineInstr *MI,
MachineBasicBlock *MBB,
const TargetRegisterInfo *TRI,
MachineRegisterInfo* MRI) {
// First check if register is livein.
bool isLiveIn = false;
for (MachineBasicBlock::const_livein_iterator I = MBB->livein_begin(),
E = MBB->livein_end(); I != E; ++I)
if (Reg == *I || TRI->isSuperRegister(Reg, *I)) {
isLiveIn = true;
break;
}
if (!isLiveIn)
return false;
// Is there any use of it before the specified MI?
SmallPtrSet<MachineInstr*, 4> UsesInMBB;
for (MachineRegisterInfo::use_iterator UI = MRI->use_begin(Reg),
UE = MRI->use_end(); UI != UE; ++UI) {
MachineOperand &UseMO = UI.getOperand();
if (UseMO.isReg() && UseMO.isUndef())
continue;
MachineInstr *UseMI = &*UI;
if (UseMI->getParent() == MBB)
UsesInMBB.insert(UseMI);
}
if (UsesInMBB.empty())
return true;
for (MachineBasicBlock::iterator I = MBB->begin(), E = MI; I != E; ++I)
if (UsesInMBB.count(&*I))
return false;
return true;
}
bool MipsDAGToDAGISel::ReplaceUsesWithZeroReg(MachineRegisterInfo *MRI,
const MachineInstr& MI) {
unsigned DstReg = 0, ZeroReg = 0;
// Check if MI is "addiu $dst, $zero, 0" or "daddiu $dst, $zero, 0".
if ((MI.getOpcode() == Mips::ADDiu) &&
(MI.getOperand(1).getReg() == Mips::ZERO) &&
(MI.getOperand(2).getImm() == 0)) {
DstReg = MI.getOperand(0).getReg();
ZeroReg = Mips::ZERO;
} else if ((MI.getOpcode() == Mips::DADDiu) &&
(MI.getOperand(1).getReg() == Mips::ZERO_64) &&
(MI.getOperand(2).getImm() == 0)) {
DstReg = MI.getOperand(0).getReg();
ZeroReg = Mips::ZERO_64;
}
if (!DstReg)
return false;
// Replace uses with ZeroReg.
for (MachineRegisterInfo::use_iterator U = MRI->use_begin(DstReg),
E = MRI->use_end(); U != E; ++U) {
MachineOperand &MO = U.getOperand();
MachineInstr *MI = MO.getParent();
// Do not replace if it is a phi's operand or is tied to def operand.
if (MI->isPHI() || MI->isRegTiedToDefOperand(U.getOperandNo()))
continue;
MO.setReg(ZeroReg);
}
return true;
}
/// 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();
}
void BitLevelInfo::propagateBitWidth(MachineOperand &MO) {
assert(MO.isReg() && "Wrong operand type!");
unsigned RegNo = MO.getReg();
unsigned char BitWidth = VInstrInfo::getBitWidth(MO);
assert(BitWidth && "Bit width not available!");
for (MachineRegisterInfo::use_iterator I = MRI->use_begin(RegNo),
E = MRI->use_end(); I != E; ++I) {
MachineOperand &MO = I.getOperand();
// Propagate bit width information through the def-use chain.
if (updateBitWidth(MO, BitWidth) && (I->isCopy() || I->isPHI()))
computeBitWidth(&*I);
}
}
/// TailDuplicateBlocks - Look for small blocks that are unconditionally
/// branched to and do not fall through. Tail-duplicate their instructions
/// into their predecessors to eliminate (dynamic) branches.
bool TailDuplicatePass::TailDuplicateBlocks(MachineFunction &MF) {
bool MadeChange = false;
if (PreRegAlloc && TailDupVerify) {
DEBUG(dbgs() << "\n*** Before tail-duplicating\n");
VerifyPHIs(MF, true);
}
SmallVector<MachineInstr*, 8> NewPHIs;
MachineSSAUpdater SSAUpdate(MF, &NewPHIs);
for (MachineFunction::iterator I = ++MF.begin(), E = MF.end(); I != E; ) {
MachineBasicBlock *MBB = I++;
if (NumTails == TailDupLimit)
break;
// Save the successors list.
SmallSetVector<MachineBasicBlock*, 8> Succs(MBB->succ_begin(),
MBB->succ_end());
SmallVector<MachineBasicBlock*, 8> TDBBs;
SmallVector<MachineInstr*, 16> Copies;
if (TailDuplicate(MBB, MF, TDBBs, Copies)) {
++NumTails;
// TailBB's immediate successors are now successors of those predecessors
// which duplicated TailBB. Add the predecessors as sources to the PHI
// instructions.
bool isDead = MBB->pred_empty();
if (PreRegAlloc)
UpdateSuccessorsPHIs(MBB, isDead, TDBBs, Succs);
// If it is dead, remove it.
if (isDead) {
NumInstrDups -= MBB->size();
RemoveDeadBlock(MBB);
++NumDeadBlocks;
}
// Update SSA form.
if (!SSAUpdateVRs.empty()) {
for (unsigned i = 0, e = SSAUpdateVRs.size(); i != e; ++i) {
unsigned VReg = SSAUpdateVRs[i];
SSAUpdate.Initialize(VReg);
// If the original definition is still around, add it as an available
// value.
MachineInstr *DefMI = MRI->getVRegDef(VReg);
MachineBasicBlock *DefBB = 0;
if (DefMI) {
DefBB = DefMI->getParent();
SSAUpdate.AddAvailableValue(DefBB, VReg);
}
// Add the new vregs as available values.
DenseMap<unsigned, AvailableValsTy>::iterator LI =
SSAUpdateVals.find(VReg);
for (unsigned j = 0, ee = LI->second.size(); j != ee; ++j) {
MachineBasicBlock *SrcBB = LI->second[j].first;
unsigned SrcReg = LI->second[j].second;
SSAUpdate.AddAvailableValue(SrcBB, SrcReg);
}
// Rewrite uses that are outside of the original def's block.
MachineRegisterInfo::use_iterator UI = MRI->use_begin(VReg);
while (UI != MRI->use_end()) {
MachineOperand &UseMO = UI.getOperand();
MachineInstr *UseMI = &*UI;
++UI;
if (UseMI->isDebugValue()) {
// SSAUpdate can replace the use with an undef. That creates
// a debug instruction that is a kill.
// FIXME: Should it SSAUpdate job to delete debug instructions
// instead of replacing the use with undef?
UseMI->eraseFromParent();
continue;
}
if (UseMI->getParent() == DefBB && !UseMI->isPHI())
continue;
SSAUpdate.RewriteUse(UseMO);
}
}
SSAUpdateVRs.clear();
SSAUpdateVals.clear();
}
// Eliminate some of the copies inserted by tail duplication to maintain
// SSA form.
for (unsigned i = 0, e = Copies.size(); i != e; ++i) {
MachineInstr *Copy = Copies[i];
if (!Copy->isCopy())
continue;
unsigned Dst = Copy->getOperand(0).getReg();
unsigned Src = Copy->getOperand(1).getReg();
MachineRegisterInfo::use_iterator UI = MRI->use_begin(Src);
if (++UI == MRI->use_end()) {
// Copy is the only use. Do trivial copy propagation here.
MRI->replaceRegWith(Dst, Src);
Copy->eraseFromParent();
}
}
if (PreRegAlloc && TailDupVerify)
VerifyPHIs(MF, false);
MadeChange = true;
}
}
NumAddedPHIs += NewPHIs.size();
return MadeChange;
}
bool A15SDOptimizer::runOnInstruction(MachineInstr *MI) {
// We look for instructions that write S registers that are then read as
// D/Q registers. These can only be caused by COPY, INSERT_SUBREG and
// REG_SEQUENCE pseudos that insert an SPR value into a DPR register or
// merge two SPR values to form a DPR register. In order avoid false
// positives we make sure that there is an SPR producer so we look past
// COPY and PHI nodes to find it.
//
// The best code pattern for when an SPR producer is going to be used by a
// DPR or QPR consumer depends on whether the other lanes of the
// corresponding DPR/QPR are currently defined.
//
// We can handle these efficiently, depending on the type of
// pseudo-instruction that is producing the pattern
//
// * COPY: * VDUP all lanes and merge the results together
// using VEXTs.
//
// * INSERT_SUBREG: * If the SPR value was originally in another DPR/QPR
// lane, and the other lane(s) of the DPR/QPR register
// that we are inserting in are undefined, use the
// original DPR/QPR value.
// * Otherwise, fall back on the same stategy as COPY.
//
// * REG_SEQUENCE: * If all except one of the input operands are
// IMPLICIT_DEFs, insert the VDUP pattern for just the
// defined input operand
// * Otherwise, fall back on the same stategy as COPY.
//
// First, get all the reads of D-registers done by this instruction.
SmallVector<unsigned, 8> Defs = getReadDPRs(MI);
bool Modified = false;
for (SmallVectorImpl<unsigned>::iterator I = Defs.begin(), E = Defs.end();
I != E; ++I) {
// Follow the def-use chain for this DPR through COPYs, and also through
// PHIs (which are essentially multi-way COPYs). It is because of PHIs that
// we can end up with multiple defs of this DPR.
SmallVector<MachineInstr *, 8> DefSrcs;
if (!TRI->isVirtualRegister(*I))
continue;
MachineInstr *Def = MRI->getVRegDef(*I);
if (!Def)
continue;
elideCopiesAndPHIs(Def, DefSrcs);
for (SmallVectorImpl<MachineInstr *>::iterator II = DefSrcs.begin(),
EE = DefSrcs.end(); II != EE; ++II) {
MachineInstr *MI = *II;
// If we've already analyzed and replaced this operand, don't do
// anything.
if (Replacements.find(MI) != Replacements.end())
continue;
// Now, work out if the instruction causes a SPR->DPR dependency.
if (!hasPartialWrite(MI))
continue;
// Collect all the uses of this MI's DPR def for updating later.
SmallVector<MachineOperand*, 8> Uses;
unsigned DPRDefReg = MI->getOperand(0).getReg();
for (MachineRegisterInfo::use_iterator I = MRI->use_begin(DPRDefReg),
E = MRI->use_end(); I != E; ++I)
Uses.push_back(&I.getOperand());
// We can optimize this.
unsigned NewReg = optimizeSDPattern(MI);
if (NewReg != 0) {
Modified = true;
for (SmallVectorImpl<MachineOperand *>::const_iterator I = Uses.begin(),
E = Uses.end(); I != E; ++I) {
// Make sure to constrain the register class of the new register to
// match what we're replacing. Otherwise we can optimize a DPR_VFP2
// reference into a plain DPR, and that will end poorly. NewReg is
// always virtual here, so there will always be a matching subclass
// to find.
MRI->constrainRegClass(NewReg, MRI->getRegClass((*I)->getReg()));
DEBUG(dbgs() << "Replacing operand "
<< **I << " with "
<< PrintReg(NewReg) << "\n");
(*I)->substVirtReg(NewReg, 0, *TRI);
}
}
Replacements[MI] = NewReg;
}
}
return Modified;
}
bool DeadMachineInstructionElim::runOnMachineFunction(MachineFunction &MF) {
bool AnyChanges = false;
MRI = &MF.getRegInfo();
TRI = MF.getTarget().getRegisterInfo();
TII = MF.getTarget().getInstrInfo();
// Treat reserved registers as always live.
BitVector ReservedRegs = TRI->getReservedRegs(MF);
// Loop over all instructions in all blocks, from bottom to top, so that it's
// more likely that chains of dependent but ultimately dead instructions will
// be cleaned up.
for (MachineFunction::reverse_iterator I = MF.rbegin(), E = MF.rend();
I != E; ++I) {
MachineBasicBlock *MBB = &*I;
// Start out assuming that reserved registers are live out of this block.
LivePhysRegs = ReservedRegs;
// Also add any explicit live-out physregs for this block.
if (!MBB->empty() && MBB->back().getDesc().isReturn())
for (MachineRegisterInfo::liveout_iterator LOI = MRI->liveout_begin(),
LOE = MRI->liveout_end(); LOI != LOE; ++LOI) {
unsigned Reg = *LOI;
if (TargetRegisterInfo::isPhysicalRegister(Reg))
LivePhysRegs.set(Reg);
}
// FIXME: Add live-ins from sucessors to LivePhysRegs. Normally, physregs
// are not live across blocks, but some targets (x86) can have flags live
// out of a block.
// Now scan the instructions and delete dead ones, tracking physreg
// liveness as we go.
for (MachineBasicBlock::reverse_iterator MII = MBB->rbegin(),
MIE = MBB->rend(); MII != MIE; ) {
MachineInstr *MI = &*MII;
// If the instruction is dead, delete it!
if (isDead(MI)) {
DEBUG(dbgs() << "DeadMachineInstructionElim: DELETING: " << *MI);
// It is possible that some DBG_VALUE instructions refer to this
// instruction. Examine each def operand for such references;
// if found, mark the DBG_VALUE as undef (but don't delete it).
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg() || !MO.isDef())
continue;
unsigned Reg = MO.getReg();
if (!TargetRegisterInfo::isVirtualRegister(Reg))
continue;
MachineRegisterInfo::use_iterator nextI;
for (MachineRegisterInfo::use_iterator I = MRI->use_begin(Reg),
E = MRI->use_end(); I!=E; I=nextI) {
nextI = llvm::next(I); // I is invalidated by the setReg
MachineOperand& Use = I.getOperand();
MachineInstr *UseMI = Use.getParent();
if (UseMI==MI)
continue;
assert(Use.isDebug());
UseMI->getOperand(0).setReg(0U);
}
}
AnyChanges = true;
MI->eraseFromParent();
++NumDeletes;
MIE = MBB->rend();
// MII is now pointing to the next instruction to process,
// so don't increment it.
continue;
}
// Record the physreg defs.
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = MI->getOperand(i);
if (MO.isReg() && MO.isDef()) {
unsigned Reg = MO.getReg();
if (Reg != 0 && TargetRegisterInfo::isPhysicalRegister(Reg)) {
LivePhysRegs.reset(Reg);
// Check the subreg set, not the alias set, because a def
// of a super-register may still be partially live after
// this def.
for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
*SubRegs; ++SubRegs)
LivePhysRegs.reset(*SubRegs);
}
}
}
// Record the physreg uses, after the defs, in case a physreg is
// both defined and used in the same instruction.
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = MI->getOperand(i);
if (MO.isReg() && MO.isUse()) {
unsigned Reg = MO.getReg();
if (Reg != 0 && TargetRegisterInfo::isPhysicalRegister(Reg)) {
LivePhysRegs.set(Reg);
for (const unsigned *AliasSet = TRI->getAliasSet(Reg);
*AliasSet; ++AliasSet)
LivePhysRegs.set(*AliasSet);
}
}
}
// We didn't delete the current instruction, so increment MII to
// the next one.
++MII;
}
}
LivePhysRegs.clear();
return AnyChanges;
}
/// processImplicitDefs - Process IMPLICIT_DEF instructions and make sure
/// there is one implicit_def for each use. Add isUndef marker to
/// implicit_def defs and their uses.
bool ProcessImplicitDefs::runOnMachineFunction(MachineFunction &fn) {
DEBUG(dbgs() << "********** PROCESS IMPLICIT DEFS **********\n"
<< "********** Function: "
<< ((Value*)fn.getFunction())->getName() << '\n');
bool Changed = false;
TII = fn.getTarget().getInstrInfo();
TRI = fn.getTarget().getRegisterInfo();
MRI = &fn.getRegInfo();
LV = &getAnalysis<LiveVariables>();
SmallSet<unsigned, 8> ImpDefRegs;
SmallVector<MachineInstr*, 8> ImpDefMIs;
SmallVector<MachineInstr*, 4> RUses;
SmallPtrSet<MachineBasicBlock*,16> Visited;
SmallPtrSet<MachineInstr*, 8> ModInsts;
MachineBasicBlock *Entry = fn.begin();
for (df_ext_iterator<MachineBasicBlock*, SmallPtrSet<MachineBasicBlock*,16> >
DFI = df_ext_begin(Entry, Visited), E = df_ext_end(Entry, Visited);
DFI != E; ++DFI) {
MachineBasicBlock *MBB = *DFI;
for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end();
I != E; ) {
MachineInstr *MI = &*I;
++I;
if (MI->isImplicitDef()) {
ImpDefMIs.push_back(MI);
// Is this a sub-register read-modify-write?
if (MI->getOperand(0).readsReg())
continue;
unsigned Reg = MI->getOperand(0).getReg();
ImpDefRegs.insert(Reg);
if (TargetRegisterInfo::isPhysicalRegister(Reg)) {
for (const unsigned *SS = TRI->getSubRegisters(Reg); *SS; ++SS)
ImpDefRegs.insert(*SS);
}
continue;
}
// Eliminate %reg1032:sub<def> = COPY undef.
if (MI->isCopy() && MI->getOperand(0).readsReg()) {
MachineOperand &MO = MI->getOperand(1);
if (MO.isUndef() || ImpDefRegs.count(MO.getReg())) {
if (MO.isKill()) {
LiveVariables::VarInfo& vi = LV->getVarInfo(MO.getReg());
vi.removeKill(MI);
}
unsigned Reg = MI->getOperand(0).getReg();
MI->eraseFromParent();
Changed = true;
// A REG_SEQUENCE may have been expanded into partial definitions.
// If this was the last one, mark Reg as implicitly defined.
if (TargetRegisterInfo::isVirtualRegister(Reg) && MRI->def_empty(Reg))
ImpDefRegs.insert(Reg);
continue;
}
}
bool ChangedToImpDef = false;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand& MO = MI->getOperand(i);
if (!MO.isReg() || !MO.readsReg())
continue;
unsigned Reg = MO.getReg();
if (!Reg)
continue;
if (!ImpDefRegs.count(Reg))
continue;
// Use is a copy, just turn it into an implicit_def.
if (CanTurnIntoImplicitDef(MI, Reg, i, ImpDefRegs)) {
bool isKill = MO.isKill();
MI->setDesc(TII->get(TargetOpcode::IMPLICIT_DEF));
for (int j = MI->getNumOperands() - 1, ee = 0; j > ee; --j)
MI->RemoveOperand(j);
if (isKill) {
ImpDefRegs.erase(Reg);
LiveVariables::VarInfo& vi = LV->getVarInfo(Reg);
vi.removeKill(MI);
}
ChangedToImpDef = true;
Changed = true;
break;
}
Changed = true;
MO.setIsUndef();
// This is a partial register redef of an implicit def.
// Make sure the whole register is defined by the instruction.
if (MO.isDef()) {
MI->addRegisterDefined(Reg);
continue;
}
if (MO.isKill() || MI->isRegTiedToDefOperand(i)) {
// Make sure other reads of Reg are also marked <undef>.
for (unsigned j = i+1; j != e; ++j) {
MachineOperand &MOJ = MI->getOperand(j);
if (MOJ.isReg() && MOJ.getReg() == Reg && MOJ.readsReg())
MOJ.setIsUndef();
}
ImpDefRegs.erase(Reg);
}
}
if (ChangedToImpDef) {
// Backtrack to process this new implicit_def.
--I;
} else {
for (unsigned i = 0; i != MI->getNumOperands(); ++i) {
MachineOperand& MO = MI->getOperand(i);
if (!MO.isReg() || !MO.isDef())
continue;
ImpDefRegs.erase(MO.getReg());
}
}
}
// Any outstanding liveout implicit_def's?
for (unsigned i = 0, e = ImpDefMIs.size(); i != e; ++i) {
MachineInstr *MI = ImpDefMIs[i];
unsigned Reg = MI->getOperand(0).getReg();
if (TargetRegisterInfo::isPhysicalRegister(Reg) ||
!ImpDefRegs.count(Reg)) {
// Delete all "local" implicit_def's. That include those which define
// physical registers since they cannot be liveout.
MI->eraseFromParent();
Changed = true;
continue;
}
// If there are multiple defs of the same register and at least one
// is not an implicit_def, do not insert implicit_def's before the
// uses.
bool Skip = false;
SmallVector<MachineInstr*, 4> DeadImpDefs;
for (MachineRegisterInfo::def_iterator DI = MRI->def_begin(Reg),
DE = MRI->def_end(); DI != DE; ++DI) {
MachineInstr *DeadImpDef = &*DI;
if (!DeadImpDef->isImplicitDef()) {
Skip = true;
break;
}
DeadImpDefs.push_back(DeadImpDef);
}
if (Skip)
continue;
// The only implicit_def which we want to keep are those that are live
// out of its block.
for (unsigned j = 0, ee = DeadImpDefs.size(); j != ee; ++j)
DeadImpDefs[j]->eraseFromParent();
Changed = true;
// Process each use instruction once.
for (MachineRegisterInfo::use_iterator UI = MRI->use_begin(Reg),
UE = MRI->use_end(); UI != UE; ++UI) {
if (UI.getOperand().isUndef())
continue;
MachineInstr *RMI = &*UI;
if (ModInsts.insert(RMI))
RUses.push_back(RMI);
}
for (unsigned i = 0, e = RUses.size(); i != e; ++i) {
MachineInstr *RMI = RUses[i];
// Turn a copy use into an implicit_def.
if (isUndefCopy(RMI, Reg, ImpDefRegs)) {
RMI->setDesc(TII->get(TargetOpcode::IMPLICIT_DEF));
bool isKill = false;
SmallVector<unsigned, 4> Ops;
for (unsigned j = 0, ee = RMI->getNumOperands(); j != ee; ++j) {
MachineOperand &RRMO = RMI->getOperand(j);
if (RRMO.isReg() && RRMO.getReg() == Reg) {
Ops.push_back(j);
if (RRMO.isKill())
isKill = true;
}
}
// Leave the other operands along.
for (unsigned j = 0, ee = Ops.size(); j != ee; ++j) {
unsigned OpIdx = Ops[j];
RMI->RemoveOperand(OpIdx-j);
}
// Update LiveVariables varinfo if the instruction is a kill.
if (isKill) {
LiveVariables::VarInfo& vi = LV->getVarInfo(Reg);
vi.removeKill(RMI);
}
continue;
}
// Replace Reg with a new vreg that's marked implicit.
const TargetRegisterClass* RC = MRI->getRegClass(Reg);
unsigned NewVReg = MRI->createVirtualRegister(RC);
bool isKill = true;
for (unsigned j = 0, ee = RMI->getNumOperands(); j != ee; ++j) {
MachineOperand &RRMO = RMI->getOperand(j);
if (RRMO.isReg() && RRMO.getReg() == Reg) {
RRMO.setReg(NewVReg);
RRMO.setIsUndef();
if (isKill) {
// Only the first operand of NewVReg is marked kill.
RRMO.setIsKill();
isKill = false;
}
}
}
}
RUses.clear();
ModInsts.clear();
}
ImpDefRegs.clear();
ImpDefMIs.clear();
}
return Changed;
}
/// Sink3AddrInstruction - A two-address instruction has been converted to a
/// three-address instruction to avoid clobbering a register. Try to sink it
/// past the instruction that would kill the above mentioned register to reduce
/// register pressure.
bool TwoAddressInstructionPass::Sink3AddrInstruction(MachineBasicBlock *MBB,
MachineInstr *MI, unsigned SavedReg,
MachineBasicBlock::iterator OldPos) {
// Check if it's safe to move this instruction.
bool SeenStore = true; // Be conservative.
if (!MI->isSafeToMove(TII, SeenStore, AA))
return false;
unsigned DefReg = 0;
SmallSet<unsigned, 4> UseRegs;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg())
continue;
unsigned MOReg = MO.getReg();
if (!MOReg)
continue;
if (MO.isUse() && MOReg != SavedReg)
UseRegs.insert(MO.getReg());
if (!MO.isDef())
continue;
if (MO.isImplicit())
// Don't try to move it if it implicitly defines a register.
return false;
if (DefReg)
// For now, don't move any instructions that define multiple registers.
return false;
DefReg = MO.getReg();
}
// Find the instruction that kills SavedReg.
MachineInstr *KillMI = NULL;
for (MachineRegisterInfo::use_iterator UI = MRI->use_begin(SavedReg),
UE = MRI->use_end(); UI != UE; ++UI) {
MachineOperand &UseMO = UI.getOperand();
if (!UseMO.isKill())
continue;
KillMI = UseMO.getParent();
break;
}
if (!KillMI || KillMI->getParent() != MBB || KillMI == MI)
return false;
// If any of the definitions are used by another instruction between the
// position and the kill use, then it's not safe to sink it.
//
// FIXME: This can be sped up if there is an easy way to query whether an
// instruction is before or after another instruction. Then we can use
// MachineRegisterInfo def / use instead.
MachineOperand *KillMO = NULL;
MachineBasicBlock::iterator KillPos = KillMI;
++KillPos;
unsigned NumVisited = 0;
for (MachineBasicBlock::iterator I = next(OldPos); I != KillPos; ++I) {
MachineInstr *OtherMI = I;
if (NumVisited > 30) // FIXME: Arbitrary limit to reduce compile time cost.
return false;
++NumVisited;
for (unsigned i = 0, e = OtherMI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = OtherMI->getOperand(i);
if (!MO.isReg())
continue;
unsigned MOReg = MO.getReg();
if (!MOReg)
continue;
if (DefReg == MOReg)
return false;
if (MO.isKill()) {
if (OtherMI == KillMI && MOReg == SavedReg)
// Save the operand that kills the register. We want to unset the kill
// marker if we can sink MI past it.
KillMO = &MO;
else if (UseRegs.count(MOReg))
// One of the uses is killed before the destination.
return false;
}
}
}
// Update kill and LV information.
KillMO->setIsKill(false);
KillMO = MI->findRegisterUseOperand(SavedReg, false, TRI);
KillMO->setIsKill(true);
if (LV)
LV->replaceKillInstruction(SavedReg, KillMI, MI);
// Move instruction to its destination.
MBB->remove(MI);
MBB->insert(KillPos, MI);
++Num3AddrSunk;
return true;
}