bool StrongPHIElimination::runOnMachineFunction(MachineFunction &MF) {
MRI = &MF.getRegInfo();
TII = MF.getTarget().getInstrInfo();
DT = &getAnalysis<MachineDominatorTree>();
LI = &getAnalysis<LiveIntervals>();
for (MachineFunction::iterator I = MF.begin(), E = MF.end();
I != E; ++I) {
for (MachineBasicBlock::iterator BBI = I->begin(), BBE = I->end();
BBI != BBE && BBI->isPHI(); ++BBI) {
unsigned DestReg = BBI->getOperand(0).getReg();
addReg(DestReg);
PHISrcDefs[I].push_back(BBI);
for (unsigned i = 1; i < BBI->getNumOperands(); i += 2) {
MachineOperand &SrcMO = BBI->getOperand(i);
unsigned SrcReg = SrcMO.getReg();
addReg(SrcReg);
unionRegs(DestReg, SrcReg);
MachineInstr *DefMI = MRI->getVRegDef(SrcReg);
if (DefMI)
PHISrcDefs[DefMI->getParent()].push_back(DefMI);
}
}
}
// Perform a depth-first traversal of the dominator tree, splitting
// interferences amongst PHI-congruence classes.
DenseMap<unsigned, unsigned> CurrentDominatingParent;
DenseMap<unsigned, unsigned> ImmediateDominatingParent;
for (df_iterator<MachineDomTreeNode*> DI = df_begin(DT->getRootNode()),
DE = df_end(DT->getRootNode()); DI != DE; ++DI) {
SplitInterferencesForBasicBlock(*DI->getBlock(),
CurrentDominatingParent,
ImmediateDominatingParent);
}
// Insert copies for all PHI source and destination registers.
for (MachineFunction::iterator I = MF.begin(), E = MF.end();
I != E; ++I) {
for (MachineBasicBlock::iterator BBI = I->begin(), BBE = I->end();
BBI != BBE && BBI->isPHI(); ++BBI) {
InsertCopiesForPHI(BBI, I);
}
}
// FIXME: Preserve the equivalence classes during copy insertion and use
// the preversed equivalence classes instead of recomputing them.
RegNodeMap.clear();
for (MachineFunction::iterator I = MF.begin(), E = MF.end();
I != E; ++I) {
for (MachineBasicBlock::iterator BBI = I->begin(), BBE = I->end();
BBI != BBE && BBI->isPHI(); ++BBI) {
unsigned DestReg = BBI->getOperand(0).getReg();
addReg(DestReg);
for (unsigned i = 1; i < BBI->getNumOperands(); i += 2) {
unsigned SrcReg = BBI->getOperand(i).getReg();
addReg(SrcReg);
unionRegs(DestReg, SrcReg);
}
}
}
DenseMap<unsigned, unsigned> RegRenamingMap;
bool Changed = false;
for (MachineFunction::iterator I = MF.begin(), E = MF.end();
I != E; ++I) {
MachineBasicBlock::iterator BBI = I->begin(), BBE = I->end();
while (BBI != BBE && BBI->isPHI()) {
MachineInstr *PHI = BBI;
assert(PHI->getNumOperands() > 0);
unsigned SrcReg = PHI->getOperand(1).getReg();
unsigned SrcColor = getRegColor(SrcReg);
unsigned NewReg = RegRenamingMap[SrcColor];
if (!NewReg) {
NewReg = SrcReg;
RegRenamingMap[SrcColor] = SrcReg;
}
MergeLIsAndRename(SrcReg, NewReg);
unsigned DestReg = PHI->getOperand(0).getReg();
if (!InsertedDestCopies.count(DestReg))
MergeLIsAndRename(DestReg, NewReg);
for (unsigned i = 3; i < PHI->getNumOperands(); i += 2) {
unsigned SrcReg = PHI->getOperand(i).getReg();
MergeLIsAndRename(SrcReg, NewReg);
}
++BBI;
LI->RemoveMachineInstrFromMaps(PHI);
PHI->eraseFromParent();
Changed = true;
}
}
// Due to the insertion of copies to split live ranges, the live intervals are
// guaranteed to not overlap, except in one case: an original PHI source and a
// PHI destination copy. In this case, they have the same value and thus don't
// truly intersect, so we merge them into the value live at that point.
// FIXME: Is there some better way we can handle this?
for (DestCopyMap::iterator I = InsertedDestCopies.begin(),
E = InsertedDestCopies.end(); I != E; ++I) {
unsigned DestReg = I->first;
unsigned DestColor = getRegColor(DestReg);
unsigned NewReg = RegRenamingMap[DestColor];
LiveInterval &DestLI = LI->getInterval(DestReg);
LiveInterval &NewLI = LI->getInterval(NewReg);
assert(DestLI.ranges.size() == 1
&& "PHI destination copy's live interval should be a single live "
"range from the beginning of the BB to the copy instruction.");
LiveRange *DestLR = DestLI.begin();
VNInfo *NewVNI = NewLI.getVNInfoAt(DestLR->start);
if (!NewVNI) {
NewVNI = NewLI.createValueCopy(DestLR->valno, LI->getVNInfoAllocator());
MachineInstr *CopyInstr = I->second;
CopyInstr->getOperand(1).setIsKill(true);
}
LiveRange NewLR(DestLR->start, DestLR->end, NewVNI);
NewLI.addRange(NewLR);
LI->removeInterval(DestReg);
MRI->replaceRegWith(DestReg, NewReg);
}
// Adjust the live intervals of all PHI source registers to handle the case
// where the PHIs in successor blocks were the only later uses of the source
// register.
for (SrcCopySet::iterator I = InsertedSrcCopySet.begin(),
E = InsertedSrcCopySet.end(); I != E; ++I) {
MachineBasicBlock *MBB = I->first;
unsigned SrcReg = I->second;
if (unsigned RenamedRegister = RegRenamingMap[getRegColor(SrcReg)])
SrcReg = RenamedRegister;
LiveInterval &SrcLI = LI->getInterval(SrcReg);
bool isLiveOut = false;
for (MachineBasicBlock::succ_iterator SI = MBB->succ_begin(),
SE = MBB->succ_end(); SI != SE; ++SI) {
if (SrcLI.liveAt(LI->getMBBStartIdx(*SI))) {
isLiveOut = true;
break;
}
}
if (isLiveOut)
continue;
MachineOperand *LastUse = findLastUse(MBB, SrcReg);
assert(LastUse);
SlotIndex LastUseIndex = LI->getInstructionIndex(LastUse->getParent());
SrcLI.removeRange(LastUseIndex.getDefIndex(), LI->getMBBEndIdx(MBB));
LastUse->setIsKill(true);
}
LI->renumber();
Allocator.Reset();
RegNodeMap.clear();
PHISrcDefs.clear();
InsertedSrcCopySet.clear();
InsertedSrcCopyMap.clear();
InsertedDestCopies.clear();
return Changed;
}
/// replaceFrameIndices - Replace all MO_FrameIndex operands with physical
/// register references and actual offsets.
///
void PEI::replaceFrameIndices(MachineFunction &Fn) {
if (!Fn.getFrameInfo()->hasStackObjects()) return; // Nothing to do?
const TargetMachine &TM = Fn.getTarget();
assert(TM.getRegisterInfo() && "TM::getRegisterInfo() must be implemented!");
const TargetInstrInfo &TII = *Fn.getTarget().getInstrInfo();
const TargetRegisterInfo &TRI = *TM.getRegisterInfo();
const TargetFrameLowering *TFI = TM.getFrameLowering();
bool StackGrowsDown =
TFI->getStackGrowthDirection() == TargetFrameLowering::StackGrowsDown;
int FrameSetupOpcode = TII.getCallFrameSetupOpcode();
int FrameDestroyOpcode = TII.getCallFrameDestroyOpcode();
for (MachineFunction::iterator BB = Fn.begin(),
E = Fn.end(); BB != E; ++BB) {
#ifndef NDEBUG
int SPAdjCount = 0; // frame setup / destroy count.
#endif
int SPAdj = 0; // SP offset due to call frame setup / destroy.
if (RS && !FrameIndexVirtualScavenging) RS->enterBasicBlock(BB);
for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ) {
if (I->getOpcode() == FrameSetupOpcode ||
I->getOpcode() == FrameDestroyOpcode) {
#ifndef NDEBUG
// Track whether we see even pairs of them
SPAdjCount += I->getOpcode() == FrameSetupOpcode ? 1 : -1;
#endif
// Remember how much SP has been adjusted to create the call
// frame.
int Size = I->getOperand(0).getImm();
if ((!StackGrowsDown && I->getOpcode() == FrameSetupOpcode) ||
(StackGrowsDown && I->getOpcode() == FrameDestroyOpcode))
Size = -Size;
SPAdj += Size;
MachineBasicBlock::iterator PrevI = BB->end();
if (I != BB->begin()) PrevI = prior(I);
TRI.eliminateCallFramePseudoInstr(Fn, *BB, I);
// Visit the instructions created by eliminateCallFramePseudoInstr().
if (PrevI == BB->end())
I = BB->begin(); // The replaced instr was the first in the block.
else
I = llvm::next(PrevI);
continue;
}
MachineInstr *MI = I;
bool DoIncr = true;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i)
if (MI->getOperand(i).isFI()) {
// Some instructions (e.g. inline asm instructions) can have
// multiple frame indices and/or cause eliminateFrameIndex
// to insert more than one instruction. We need the register
// scavenger to go through all of these instructions so that
// it can update its register information. We keep the
// iterator at the point before insertion so that we can
// revisit them in full.
bool AtBeginning = (I == BB->begin());
if (!AtBeginning) --I;
// If this instruction has a FrameIndex operand, we need to
// use that target machine register info object to eliminate
// it.
TRI.eliminateFrameIndex(MI, SPAdj,
FrameIndexVirtualScavenging ? NULL : RS);
// Reset the iterator if we were at the beginning of the BB.
if (AtBeginning) {
I = BB->begin();
DoIncr = false;
}
MI = 0;
break;
}
if (DoIncr && I != BB->end()) ++I;
// Update register states.
if (RS && !FrameIndexVirtualScavenging && MI) RS->forward(MI);
}
// If we have evenly matched pairs of frame setup / destroy instructions,
// make sure the adjustments come out to zero. If we don't have matched
// pairs, we can't be sure the missing bit isn't in another basic block
// due to a custom inserter playing tricks, so just asserting SPAdj==0
// isn't sufficient. See tMOVCC on Thumb1, for example.
assert((SPAdjCount || SPAdj == 0) &&
"Unbalanced call frame setup / destroy pairs?");
}
}
bool GCMachineCodeFixup::runOnMachineFunction(MachineFunction &MF) {
// Quick exit for functions that do not use GC.
if (!MF.getFunction()->hasGC())
return false;
const TargetMachine &TM = MF.getTarget();
const TargetInstrInfo *TII = TM.getInstrInfo();
GCModuleInfo &GMI = getAnalysis<GCModuleInfo>();
GCFunctionInfo &GCFI = GMI.getFunctionInfo(*MF.getFunction());
for (MachineFunction::iterator MBBI = MF.begin(),
MBBE = MF.end(); MBBI != MBBE; ++MBBI) {
for (MachineBasicBlock::iterator MII = MBBI->begin(),
MIE = MBBI->end(); MII != MIE;) {
if (!MII->isGCRegRoot() || !MII->getOperand(0).isReg()) {
++MII;
continue;
}
// Trace the register back to its location at the site of the call (either
// a physical reg or a frame index).
bool TracingReg = true;
unsigned TracedReg = MII->getOperand(0).getReg();
int FrameIndex;
MachineBasicBlock::iterator PrevII = MII;
for (--PrevII;; --PrevII) {
if (PrevII->isGCRegRoot() && PrevII->getOperand(0).isReg())
break;
if (PrevII->isCall())
break;
int FI;
// Trace back through register reloads.
unsigned Reg =
TM.getInstrInfo()->isLoadFromStackSlotPostFE(&*PrevII, FI);
if (Reg) {
// This is a reload. If we're tracing this register, start tracing the
// frame index instead.
if (TracingReg && TracedReg == Reg) {
TracingReg = false;
FrameIndex = FI;
}
continue;
}
// Trace back through spills.
if (TM.getInstrInfo()->isStoreToStackSlotPostFE(&*PrevII, FI))
continue;
// Trace back through register-to-register copies.
if (PrevII->isCopy()) {
if (TracingReg && TracedReg == PrevII->getOperand(0).getReg())
TracedReg = PrevII->getOperand(1).getReg();
continue;
}
// Trace back through non-register GC_REG_ROOT instructions.
if (PrevII->isGCRegRoot() && !PrevII->getOperand(0).isReg())
continue;
DEBUG(dbgs() << "Bad instruction: " << *PrevII);
llvm_unreachable("GC_REG_ROOT found in an unexpected location!");
}
// Now we've reached either a call or another GC_REG_ROOT instruction.
// Move the GC_REG_ROOT instruction we're considering to the right place,
// and rewrite it if necessary.
//
// Also, tell the GCFunctionInfo about the frame index, since this is
// our only chance -- the frame indices will be deleted by the time
// GCMachineCodeAnalysis runs.
++PrevII;
unsigned RootIndex = MII->getOperand(1).getImm();
MachineInstr *NewMI;
if (TracingReg) {
MachineInstrBuilder MIB = BuildMI(MF, MII->getDebugLoc(),
TII->get(TargetOpcode::GC_REG_ROOT));
MIB.addReg(TracedReg).addImm(RootIndex);
NewMI = MIB;
} else {
NewMI = TII->emitFrameIndexGCRegRoot(MF, FrameIndex, RootIndex,
MII->getDebugLoc());
GCFI.spillRegRoot(RootIndex, FrameIndex);
}
MBBI->insert(PrevII, NewMI);
MachineBasicBlock::iterator NextII = MII;
++NextII;
MII->eraseFromParent();
MII = NextII;
}
}
return true;
}
/// scavengeFrameVirtualRegs - Replace all frame index virtual registers
/// with physical registers. Use the register scavenger to find an
/// appropriate register to use.
///
/// FIXME: Iterating over the instruction stream is unnecessary. We can simply
/// iterate over the vreg use list, which at this point only contains machine
/// operands for which eliminateFrameIndex need a new scratch reg.
void
PEI::scavengeFrameVirtualRegs(MachineFunction &Fn) {
// Run through the instructions and find any virtual registers.
for (MachineFunction::iterator BB = Fn.begin(),
E = Fn.end(); BB != E; ++BB) {
RS->enterBasicBlock(BB);
int SPAdj = 0;
// The instruction stream may change in the loop, so check BB->end()
// directly.
for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ) {
// We might end up here again with a NULL iterator if we scavenged a
// register for which we inserted spill code for definition by what was
// originally the first instruction in BB.
if (I == MachineBasicBlock::iterator(nullptr))
I = BB->begin();
MachineInstr *MI = I;
MachineBasicBlock::iterator J = std::next(I);
MachineBasicBlock::iterator P =
I == BB->begin() ? MachineBasicBlock::iterator(nullptr)
: std::prev(I);
// RS should process this instruction before we might scavenge at this
// location. This is because we might be replacing a virtual register
// defined by this instruction, and if so, registers killed by this
// instruction are available, and defined registers are not.
RS->forward(I);
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
if (MI->getOperand(i).isReg()) {
MachineOperand &MO = MI->getOperand(i);
unsigned Reg = MO.getReg();
if (Reg == 0)
continue;
if (!TargetRegisterInfo::isVirtualRegister(Reg))
continue;
// When we first encounter a new virtual register, it
// must be a definition.
assert(MI->getOperand(i).isDef() &&
"frame index virtual missing def!");
// Scavenge a new scratch register
const TargetRegisterClass *RC = Fn.getRegInfo().getRegClass(Reg);
unsigned ScratchReg = RS->scavengeRegister(RC, J, SPAdj);
++NumScavengedRegs;
// Replace this reference to the virtual register with the
// scratch register.
assert (ScratchReg && "Missing scratch register!");
MachineRegisterInfo &MRI = Fn.getRegInfo();
Fn.getRegInfo().replaceRegWith(Reg, ScratchReg);
// Make sure MRI now accounts this register as used.
MRI.setPhysRegUsed(ScratchReg);
// Because this instruction was processed by the RS before this
// register was allocated, make sure that the RS now records the
// register as being used.
RS->setRegUsed(ScratchReg);
}
}
// If the scavenger needed to use one of its spill slots, the
// spill code will have been inserted in between I and J. This is a
// problem because we need the spill code before I: Move I to just
// prior to J.
if (I != std::prev(J)) {
BB->splice(J, BB, I);
// Before we move I, we need to prepare the RS to visit I again.
// Specifically, RS will assert if it sees uses of registers that
// it believes are undefined. Because we have already processed
// register kills in I, when it visits I again, it will believe that
// those registers are undefined. To avoid this situation, unprocess
// the instruction I.
assert(RS->getCurrentPosition() == I &&
"The register scavenger has an unexpected position");
I = P;
RS->unprocess(P);
} else
++I;
}
}
}
/// runOnMachineFunction - Reduce two-address instructions to two operands.
///
bool TwoAddressInstructionPass::runOnMachineFunction(MachineFunction &MF) {
DEBUG(errs() << "Machine Function\n");
const TargetMachine &TM = MF.getTarget();
MRI = &MF.getRegInfo();
TII = TM.getInstrInfo();
TRI = TM.getRegisterInfo();
LV = getAnalysisIfAvailable<LiveVariables>();
AA = &getAnalysis<AliasAnalysis>();
bool MadeChange = false;
DEBUG(errs() << "********** REWRITING TWO-ADDR INSTRS **********\n");
DEBUG(errs() << "********** Function: "
<< MF.getFunction()->getName() << '\n');
// ReMatRegs - Keep track of the registers whose def's are remat'ed.
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) {
unsigned Dist = 0;
DistanceMap.clear();
SrcRegMap.clear();
DstRegMap.clear();
Processed.clear();
for (MachineBasicBlock::iterator mi = mbbi->begin(), me = mbbi->end();
mi != me; ) {
MachineBasicBlock::iterator nmi = next(mi);
const TargetInstrDesc &TID = mi->getDesc();
bool FirstTied = true;
DistanceMap.insert(std::make_pair(mi, ++Dist));
ProcessCopy(&*mi, &*mbbi, Processed);
// First scan through all the tied register uses in this instruction
// and record a list of pairs of tied operands for each register.
unsigned NumOps = (mi->getOpcode() == TargetInstrInfo::INLINEASM)
? mi->getNumOperands() : TID.getNumOperands();
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);
}
assert(mi->getOperand(SrcIdx).isReg() &&
mi->getOperand(SrcIdx).getReg() &&
mi->getOperand(SrcIdx).isUse() &&
"two address instruction invalid");
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));
}
// 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.
}
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");
#ifndef NDEBUG
// First, verify that we don't have a use of "a" in the instruction
// (a = b + a for example) because our transformation will not
// work. This should never occur because we are in SSA form.
for (unsigned i = 0; i != mi->getNumOperands(); ++i)
assert(i == DstIdx ||
!mi->getOperand(i).isReg() ||
mi->getOperand(i).getReg() != regA);
#endif
// Emit a copy or rematerialize the definition.
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, AA) &&
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, TRI);
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;
DEBUG(errs() << "\t\tprepend:\t" << *prevMI);
MachineOperand &MO = mi->getOperand(SrcIdx);
assert(MO.isReg() && MO.getReg() == regB && MO.isUse() &&
"inconsistent operand info for 2-reg pass");
if (MO.isKill()) {
MO.setIsKill(false);
RemovedKillFlag = true;
}
MO.setReg(regA);
}
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);
}
}
// 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;
}
}
}
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;
}
}
// Some remat'ed instructions are dead.
int VReg = ReMatRegs.find_first();
while (VReg != -1) {
if (MRI->use_empty(VReg)) {
MachineInstr *DefMI = MRI->getVRegDef(VReg);
DefMI->eraseFromParent();
}
VReg = ReMatRegs.find_next(VReg);
}
return MadeChange;
}
bool PeepholeOptimizer::runOnMachineFunction(MachineFunction &MF) {
if (DisablePeephole)
return false;
TM = &MF.getTarget();
TII = TM->getInstrInfo();
MRI = &MF.getRegInfo();
DT = Aggressive ? &getAnalysis<MachineDominatorTree>() : 0;
bool Changed = false;
SmallPtrSet<MachineInstr*, 8> LocalMIs;
SmallSet<unsigned, 4> ImmDefRegs;
DenseMap<unsigned, MachineInstr*> ImmDefMIs;
for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
MachineBasicBlock *MBB = &*I;
bool SeenMoveImm = false;
LocalMIs.clear();
ImmDefRegs.clear();
ImmDefMIs.clear();
bool First = true;
MachineBasicBlock::iterator PMII;
for (MachineBasicBlock::iterator
MII = I->begin(), MIE = I->end(); MII != MIE; ) {
MachineInstr *MI = &*MII;
LocalMIs.insert(MI);
if (MI->isLabel() || MI->isPHI() || MI->isImplicitDef() ||
MI->isKill() || MI->isInlineAsm() || MI->isDebugValue() ||
MI->hasUnmodeledSideEffects()) {
++MII;
continue;
}
if (MI->isBitcast()) {
if (OptimizeBitcastInstr(MI, MBB)) {
// MI is deleted.
LocalMIs.erase(MI);
Changed = true;
MII = First ? I->begin() : llvm::next(PMII);
continue;
}
} else if (MI->isCompare()) {
if (OptimizeCmpInstr(MI, MBB)) {
// MI is deleted.
LocalMIs.erase(MI);
Changed = true;
MII = First ? I->begin() : llvm::next(PMII);
continue;
}
}
if (isMoveImmediate(MI, ImmDefRegs, ImmDefMIs)) {
SeenMoveImm = true;
} else {
Changed |= OptimizeExtInstr(MI, MBB, LocalMIs);
if (SeenMoveImm)
Changed |= FoldImmediate(MI, MBB, ImmDefRegs, ImmDefMIs);
}
First = false;
PMII = MII;
++MII;
}
}
return Changed;
}
bool PeepholeOptimizer::runOnMachineFunction(MachineFunction &MF) {
if (skipOptnoneFunction(*MF.getFunction()))
return false;
DEBUG(dbgs() << "********** PEEPHOLE OPTIMIZER **********\n");
DEBUG(dbgs() << "********** Function: " << MF.getName() << '\n');
if (DisablePeephole)
return false;
TM = &MF.getTarget();
TII = TM->getInstrInfo();
MRI = &MF.getRegInfo();
DT = Aggressive ? &getAnalysis<MachineDominatorTree>() : nullptr;
bool Changed = false;
for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
MachineBasicBlock *MBB = &*I;
bool SeenMoveImm = false;
SmallPtrSet<MachineInstr*, 8> LocalMIs;
SmallSet<unsigned, 4> ImmDefRegs;
DenseMap<unsigned, MachineInstr*> ImmDefMIs;
SmallSet<unsigned, 16> FoldAsLoadDefCandidates;
for (MachineBasicBlock::iterator
MII = I->begin(), MIE = I->end(); MII != MIE; ) {
MachineInstr *MI = &*MII;
// We may be erasing MI below, increment MII now.
++MII;
LocalMIs.insert(MI);
// Skip debug values. They should not affect this peephole optimization.
if (MI->isDebugValue())
continue;
// If there exists an instruction which belongs to the following
// categories, we will discard the load candidates.
if (MI->isPosition() || MI->isPHI() || MI->isImplicitDef() ||
MI->isKill() || MI->isInlineAsm() ||
MI->hasUnmodeledSideEffects()) {
FoldAsLoadDefCandidates.clear();
continue;
}
if (MI->mayStore() || MI->isCall())
FoldAsLoadDefCandidates.clear();
if (((MI->isBitcast() || MI->isCopy()) && optimizeCopyOrBitcast(MI)) ||
(MI->isCompare() && optimizeCmpInstr(MI, MBB)) ||
(MI->isSelect() && optimizeSelect(MI))) {
// MI is deleted.
LocalMIs.erase(MI);
Changed = true;
continue;
}
if (isMoveImmediate(MI, ImmDefRegs, ImmDefMIs)) {
SeenMoveImm = true;
} else {
Changed |= optimizeExtInstr(MI, MBB, LocalMIs);
// optimizeExtInstr might have created new instructions after MI
// and before the already incremented MII. Adjust MII so that the
// next iteration sees the new instructions.
MII = MI;
++MII;
if (SeenMoveImm)
Changed |= foldImmediate(MI, MBB, ImmDefRegs, ImmDefMIs);
}
// Check whether MI is a load candidate for folding into a later
// instruction. If MI is not a candidate, check whether we can fold an
// earlier load into MI.
if (!isLoadFoldable(MI, FoldAsLoadDefCandidates) &&
!FoldAsLoadDefCandidates.empty()) {
const MCInstrDesc &MIDesc = MI->getDesc();
for (unsigned i = MIDesc.getNumDefs(); i != MIDesc.getNumOperands();
++i) {
const MachineOperand &MOp = MI->getOperand(i);
if (!MOp.isReg())
continue;
unsigned FoldAsLoadDefReg = MOp.getReg();
if (FoldAsLoadDefCandidates.count(FoldAsLoadDefReg)) {
// We need to fold load after optimizeCmpInstr, since
// optimizeCmpInstr can enable folding by converting SUB to CMP.
// Save FoldAsLoadDefReg because optimizeLoadInstr() resets it and
// we need it for markUsesInDebugValueAsUndef().
unsigned FoldedReg = FoldAsLoadDefReg;
MachineInstr *DefMI = nullptr;
MachineInstr *FoldMI = TII->optimizeLoadInstr(MI, MRI,
FoldAsLoadDefReg,
DefMI);
if (FoldMI) {
// Update LocalMIs since we replaced MI with FoldMI and deleted
// DefMI.
DEBUG(dbgs() << "Replacing: " << *MI);
DEBUG(dbgs() << " With: " << *FoldMI);
LocalMIs.erase(MI);
LocalMIs.erase(DefMI);
LocalMIs.insert(FoldMI);
MI->eraseFromParent();
DefMI->eraseFromParent();
MRI->markUsesInDebugValueAsUndef(FoldedReg);
FoldAsLoadDefCandidates.erase(FoldedReg);
++NumLoadFold;
// MI is replaced with FoldMI.
Changed = true;
break;
}
}
}
}
}
}
return Changed;
}
/// scavengeFrameVirtualRegs - Replace all frame index virtual registers
/// with physical registers. Use the register scavenger to find an
/// appropriate register to use.
void PEI::scavengeFrameVirtualRegs(MachineFunction &Fn) {
// Run through the instructions and find any virtual registers.
for (MachineFunction::iterator BB = Fn.begin(),
E = Fn.end(); BB != E; ++BB) {
RS->enterBasicBlock(BB);
// FIXME: The logic flow in this function is still too convoluted.
// It needs a cleanup refactoring. Do that in preparation for tracking
// more than one scratch register value and using ranges to find
// available scratch registers.
unsigned CurrentVirtReg = 0;
unsigned CurrentScratchReg = 0;
bool havePrevValue = false;
int PrevValue = 0;
MachineInstr *PrevLastUseMI = NULL;
unsigned PrevLastUseOp = 0;
bool trackingCurrentValue = false;
int SPAdj = 0;
int Value = 0;
// The instruction stream may change in the loop, so check BB->end()
// directly.
for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ) {
MachineInstr *MI = I;
bool isDefInsn = false;
bool isKillInsn = false;
bool clobbersScratchReg = false;
bool DoIncr = true;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
if (MI->getOperand(i).isReg()) {
MachineOperand &MO = MI->getOperand(i);
unsigned Reg = MO.getReg();
if (Reg == 0)
continue;
if (!TargetRegisterInfo::isVirtualRegister(Reg)) {
// If we have a previous scratch reg, check and see if anything
// here kills whatever value is in there.
if (Reg == CurrentScratchReg) {
if (MO.isUse()) {
// Two-address operands implicitly kill
if (MO.isKill() || MI->isRegTiedToDefOperand(i))
clobbersScratchReg = true;
} else {
assert (MO.isDef());
clobbersScratchReg = true;
}
}
continue;
}
// If this is a def, remember that this insn defines the value.
// This lets us properly consider insns which re-use the scratch
// register, such as r2 = sub r2, #imm, in the middle of the
// scratch range.
if (MO.isDef())
isDefInsn = true;
// Have we already allocated a scratch register for this virtual?
if (Reg != CurrentVirtReg) {
// When we first encounter a new virtual register, it
// must be a definition.
assert(MI->getOperand(i).isDef() &&
"frame index virtual missing def!");
// We can't have nested virtual register live ranges because
// there's only a guarantee of one scavenged register at a time.
assert (CurrentVirtReg == 0 &&
"overlapping frame index virtual registers!");
// If the target gave us information about what's in the register,
// we can use that to re-use scratch regs.
DenseMap<unsigned, FrameConstantEntry>::iterator Entry =
FrameConstantRegMap.find(Reg);
trackingCurrentValue = Entry != FrameConstantRegMap.end();
if (trackingCurrentValue) {
SPAdj = (*Entry).second.second;
Value = (*Entry).second.first;
} else
SPAdj = Value = 0;
// If the scratch register from the last allocation is still
// available, see if the value matches. If it does, just re-use it.
if (trackingCurrentValue && havePrevValue && PrevValue == Value) {
// FIXME: This assumes that the instructions in the live range
// for the virtual register are exclusively for the purpose
// of populating the value in the register. That's reasonable
// for these frame index registers, but it's still a very, very
// strong assumption. rdar://7322732. Better would be to
// explicitly check each instruction in the range for references
// to the virtual register. Only delete those insns that
// touch the virtual register.
// Find the last use of the new virtual register. Remove all
// instruction between here and there, and update the current
// instruction to reference the last use insn instead.
MachineBasicBlock::iterator LastUseMI =
findLastUseReg(I, BB->end(), Reg);
// Remove all instructions up 'til the last use, since they're
// just calculating the value we already have.
BB->erase(I, LastUseMI);
MI = I = LastUseMI;
// Extend the live range of the scratch register
PrevLastUseMI->getOperand(PrevLastUseOp).setIsKill(false);
RS->setUsed(CurrentScratchReg);
CurrentVirtReg = Reg;
// We deleted the instruction we were scanning the operands of.
// Jump back to the instruction iterator loop. Don't increment
// past this instruction since we updated the iterator already.
DoIncr = false;
break;
}
// Scavenge a new scratch register
CurrentVirtReg = Reg;
const TargetRegisterClass *RC = Fn.getRegInfo().getRegClass(Reg);
CurrentScratchReg = RS->FindUnusedReg(RC);
if (CurrentScratchReg == 0)
// No register is "free". Scavenge a register.
CurrentScratchReg = RS->scavengeRegister(RC, I, SPAdj);
PrevValue = Value;
}
// replace this reference to the virtual register with the
// scratch register.
assert (CurrentScratchReg && "Missing scratch register!");
MI->getOperand(i).setReg(CurrentScratchReg);
if (MI->getOperand(i).isKill()) {
isKillInsn = true;
PrevLastUseOp = i;
PrevLastUseMI = MI;
}
}
}
// If this is the last use of the scratch, stop tracking it. The
// last use will be a kill operand in an instruction that does
// not also define the scratch register.
if (isKillInsn && !isDefInsn) {
CurrentVirtReg = 0;
havePrevValue = trackingCurrentValue;
}
// Similarly, notice if instruction clobbered the value in the
// register we're tracking for possible later reuse. This is noted
// above, but enforced here since the value is still live while we
// process the rest of the operands of the instruction.
if (clobbersScratchReg) {
havePrevValue = false;
CurrentScratchReg = 0;
}
if (DoIncr) {
RS->forward(I);
++I;
}
}
}
}
/// replaceFrameIndices - Replace all MO_FrameIndex operands with physical
/// register references and actual offsets.
///
void PEI::replaceFrameIndices(MachineFunction &Fn) {
if (!Fn.getFrameInfo()->hasStackObjects()) return; // Nothing to do?
const TargetMachine &TM = Fn.getTarget();
assert(TM.getRegisterInfo() && "TM::getRegisterInfo() must be implemented!");
const TargetRegisterInfo &TRI = *TM.getRegisterInfo();
const TargetFrameInfo *TFI = TM.getFrameInfo();
bool StackGrowsDown =
TFI->getStackGrowthDirection() == TargetFrameInfo::StackGrowsDown;
int FrameSetupOpcode = TRI.getCallFrameSetupOpcode();
int FrameDestroyOpcode = TRI.getCallFrameDestroyOpcode();
for (MachineFunction::iterator BB = Fn.begin(),
E = Fn.end(); BB != E; ++BB) {
int SPAdj = 0; // SP offset due to call frame setup / destroy.
if (RS && !FrameIndexVirtualScavenging) RS->enterBasicBlock(BB);
for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ) {
if (I->getOpcode() == FrameSetupOpcode ||
I->getOpcode() == FrameDestroyOpcode) {
// Remember how much SP has been adjusted to create the call
// frame.
int Size = I->getOperand(0).getImm();
if ((!StackGrowsDown && I->getOpcode() == FrameSetupOpcode) ||
(StackGrowsDown && I->getOpcode() == FrameDestroyOpcode))
Size = -Size;
SPAdj += Size;
MachineBasicBlock::iterator PrevI = BB->end();
if (I != BB->begin()) PrevI = prior(I);
TRI.eliminateCallFramePseudoInstr(Fn, *BB, I);
// Visit the instructions created by eliminateCallFramePseudoInstr().
if (PrevI == BB->end())
I = BB->begin(); // The replaced instr was the first in the block.
else
I = next(PrevI);
continue;
}
MachineInstr *MI = I;
bool DoIncr = true;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i)
if (MI->getOperand(i).isFI()) {
// Some instructions (e.g. inline asm instructions) can have
// multiple frame indices and/or cause eliminateFrameIndex
// to insert more than one instruction. We need the register
// scavenger to go through all of these instructions so that
// it can update its register information. We keep the
// iterator at the point before insertion so that we can
// revisit them in full.
bool AtBeginning = (I == BB->begin());
if (!AtBeginning) --I;
// If this instruction has a FrameIndex operand, we need to
// use that target machine register info object to eliminate
// it.
int Value;
unsigned VReg =
TRI.eliminateFrameIndex(MI, SPAdj, &Value,
FrameIndexVirtualScavenging ? NULL : RS);
if (VReg) {
assert (FrameIndexVirtualScavenging &&
"Not scavenging, but virtual returned from "
"eliminateFrameIndex()!");
FrameConstantRegMap[VReg] = FrameConstantEntry(Value, SPAdj);
}
// Reset the iterator if we were at the beginning of the BB.
if (AtBeginning) {
I = BB->begin();
DoIncr = false;
}
MI = 0;
break;
}
if (DoIncr && I != BB->end()) ++I;
// Update register states.
if (RS && !FrameIndexVirtualScavenging && MI) RS->forward(MI);
}
assert(SPAdj == 0 && "Unbalanced call frame setup / destroy pairs?");
}
}
