MachineSSAUpdater.cpp [plain text]
#include "llvm/CodeGen/MachineSSAUpdater.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
typedef DenseMap<MachineBasicBlock*, unsigned> AvailableValsTy;
typedef std::vector<std::pair<MachineBasicBlock*, unsigned> >
IncomingPredInfoTy;
static AvailableValsTy &getAvailableVals(void *AV) {
return *static_cast<AvailableValsTy*>(AV);
}
static IncomingPredInfoTy &getIncomingPredInfo(void *IPI) {
return *static_cast<IncomingPredInfoTy*>(IPI);
}
MachineSSAUpdater::MachineSSAUpdater(MachineFunction &MF,
SmallVectorImpl<MachineInstr*> *NewPHI)
: AV(0), IPI(0), InsertedPHIs(NewPHI) {
TII = MF.getTarget().getInstrInfo();
MRI = &MF.getRegInfo();
}
MachineSSAUpdater::~MachineSSAUpdater() {
delete &getAvailableVals(AV);
delete &getIncomingPredInfo(IPI);
}
void MachineSSAUpdater::Initialize(unsigned V) {
if (AV == 0)
AV = new AvailableValsTy();
else
getAvailableVals(AV).clear();
if (IPI == 0)
IPI = new IncomingPredInfoTy();
else
getIncomingPredInfo(IPI).clear();
VR = V;
VRC = MRI->getRegClass(VR);
}
bool MachineSSAUpdater::HasValueForBlock(MachineBasicBlock *BB) const {
return getAvailableVals(AV).count(BB);
}
void MachineSSAUpdater::AddAvailableValue(MachineBasicBlock *BB, unsigned V) {
getAvailableVals(AV)[BB] = V;
}
unsigned MachineSSAUpdater::GetValueAtEndOfBlock(MachineBasicBlock *BB) {
return GetValueAtEndOfBlockInternal(BB);
}
static
unsigned LookForIdenticalPHI(MachineBasicBlock *BB,
SmallVector<std::pair<MachineBasicBlock*, unsigned>, 8> &PredValues) {
if (BB->empty())
return 0;
MachineBasicBlock::iterator I = BB->front();
if (!I->isPHI())
return 0;
AvailableValsTy AVals;
for (unsigned i = 0, e = PredValues.size(); i != e; ++i)
AVals[PredValues[i].first] = PredValues[i].second;
while (I != BB->end() && I->isPHI()) {
bool Same = true;
for (unsigned i = 1, e = I->getNumOperands(); i != e; i += 2) {
unsigned SrcReg = I->getOperand(i).getReg();
MachineBasicBlock *SrcBB = I->getOperand(i+1).getMBB();
if (AVals[SrcBB] != SrcReg) {
Same = false;
break;
}
}
if (Same)
return I->getOperand(0).getReg();
++I;
}
return 0;
}
static
MachineInstr *InsertNewDef(unsigned Opcode,
MachineBasicBlock *BB, MachineBasicBlock::iterator I,
const TargetRegisterClass *RC,
MachineRegisterInfo *MRI, const TargetInstrInfo *TII) {
unsigned NewVR = MRI->createVirtualRegister(RC);
return BuildMI(*BB, I, DebugLoc(), TII->get(Opcode), NewVR);
}
unsigned MachineSSAUpdater::GetValueInMiddleOfBlock(MachineBasicBlock *BB) {
if (!getAvailableVals(AV).count(BB))
return GetValueAtEndOfBlockInternal(BB);
if (BB->pred_empty()) {
MachineInstr *NewDef = InsertNewDef(TargetOpcode::IMPLICIT_DEF,
BB, BB->getFirstTerminator(),
VRC, MRI, TII);
return NewDef->getOperand(0).getReg();
}
SmallVector<std::pair<MachineBasicBlock*, unsigned>, 8> PredValues;
unsigned SingularValue = 0;
bool isFirstPred = true;
for (MachineBasicBlock::pred_iterator PI = BB->pred_begin(),
E = BB->pred_end(); PI != E; ++PI) {
MachineBasicBlock *PredBB = *PI;
unsigned PredVal = GetValueAtEndOfBlockInternal(PredBB);
PredValues.push_back(std::make_pair(PredBB, PredVal));
if (isFirstPred) {
SingularValue = PredVal;
isFirstPred = false;
} else if (PredVal != SingularValue)
SingularValue = 0;
}
if (SingularValue != 0)
return SingularValue;
unsigned DupPHI = LookForIdenticalPHI(BB, PredValues);
if (DupPHI)
return DupPHI;
MachineBasicBlock::iterator Loc = BB->empty() ? BB->end() : BB->front();
MachineInstr *InsertedPHI = InsertNewDef(TargetOpcode::PHI, BB,
Loc, VRC, MRI, TII);
MachineInstrBuilder MIB(InsertedPHI);
for (unsigned i = 0, e = PredValues.size(); i != e; ++i)
MIB.addReg(PredValues[i].second).addMBB(PredValues[i].first);
if (unsigned ConstVal = InsertedPHI->isConstantValuePHI()) {
InsertedPHI->eraseFromParent();
return ConstVal;
}
if (InsertedPHIs) InsertedPHIs->push_back(InsertedPHI);
DEBUG(dbgs() << " Inserted PHI: " << *InsertedPHI << "\n");
return InsertedPHI->getOperand(0).getReg();
}
static
MachineBasicBlock *findCorrespondingPred(const MachineInstr *MI,
MachineOperand *U) {
for (unsigned i = 1, e = MI->getNumOperands(); i != e; i += 2) {
if (&MI->getOperand(i) == U)
return MI->getOperand(i+1).getMBB();
}
llvm_unreachable("MachineOperand::getParent() failure?");
return 0;
}
void MachineSSAUpdater::RewriteUse(MachineOperand &U) {
MachineInstr *UseMI = U.getParent();
unsigned NewVR = 0;
if (UseMI->isPHI()) {
MachineBasicBlock *SourceBB = findCorrespondingPred(UseMI, &U);
NewVR = GetValueAtEndOfBlockInternal(SourceBB);
} else {
NewVR = GetValueInMiddleOfBlock(UseMI->getParent());
}
U.setReg(NewVR);
}
void MachineSSAUpdater::ReplaceRegWith(unsigned OldReg, unsigned NewReg) {
MRI->replaceRegWith(OldReg, NewReg);
AvailableValsTy &AvailableVals = getAvailableVals(AV);
for (DenseMap<MachineBasicBlock*, unsigned>::iterator
I = AvailableVals.begin(), E = AvailableVals.end(); I != E; ++I)
if (I->second == OldReg)
I->second = NewReg;
}
unsigned MachineSSAUpdater::GetValueAtEndOfBlockInternal(MachineBasicBlock *BB){
AvailableValsTy &AvailableVals = getAvailableVals(AV);
std::pair<AvailableValsTy::iterator, bool> InsertRes =
AvailableVals.insert(std::make_pair(BB, 0));
if (!InsertRes.second) {
if (InsertRes.first->second != 0)
return InsertRes.first->second;
MachineBasicBlock::iterator Loc = BB->empty() ? BB->end() : BB->front();
MachineInstr *NewPHI = InsertNewDef(TargetOpcode::PHI, BB, Loc,
VRC, MRI,TII);
unsigned NewVR = NewPHI->getOperand(0).getReg();
InsertRes.first->second = NewVR;
return NewVR;
}
if (BB->pred_empty()) {
MachineInstr *NewDef = InsertNewDef(TargetOpcode::IMPLICIT_DEF,
BB, BB->getFirstTerminator(),
VRC, MRI, TII);
return InsertRes.first->second = NewDef->getOperand(0).getReg();
}
IncomingPredInfoTy &IncomingPredInfo = getIncomingPredInfo(IPI);
unsigned FirstPredInfoEntry = IncomingPredInfo.size();
unsigned SingularValue = 0;
bool isFirstPred = true;
for (MachineBasicBlock::pred_iterator PI = BB->pred_begin(),
E = BB->pred_end(); PI != E; ++PI) {
MachineBasicBlock *PredBB = *PI;
unsigned PredVal = GetValueAtEndOfBlockInternal(PredBB);
IncomingPredInfo.push_back(std::make_pair(PredBB, PredVal));
if (isFirstPred) {
SingularValue = PredVal;
isFirstPred = false;
} else if (PredVal != SingularValue)
SingularValue = 0;
}
unsigned &InsertedVal = AvailableVals[BB];
if (SingularValue) {
if (InsertedVal) {
MachineInstr *OldVal = MRI->getVRegDef(InsertedVal);
assert(InsertedVal != SingularValue && "Dead loop?");
ReplaceRegWith(InsertedVal, SingularValue);
OldVal->eraseFromParent();
}
InsertedVal = SingularValue;
IncomingPredInfo.erase(IncomingPredInfo.begin()+FirstPredInfoEntry,
IncomingPredInfo.end());
return InsertedVal;
}
MachineInstr *InsertedPHI;
if (InsertedVal == 0) {
MachineBasicBlock::iterator Loc = BB->empty() ? BB->end() : BB->front();
InsertedPHI = InsertNewDef(TargetOpcode::PHI, BB, Loc,
VRC, MRI, TII);
InsertedVal = InsertedPHI->getOperand(0).getReg();
} else {
InsertedPHI = MRI->getVRegDef(InsertedVal);
}
MachineInstrBuilder MIB(InsertedPHI);
for (IncomingPredInfoTy::iterator I =
IncomingPredInfo.begin()+FirstPredInfoEntry,
E = IncomingPredInfo.end(); I != E; ++I)
MIB.addReg(I->second).addMBB(I->first);
IncomingPredInfo.erase(IncomingPredInfo.begin()+FirstPredInfoEntry,
IncomingPredInfo.end());
if (unsigned ConstVal = InsertedPHI->isConstantValuePHI()) {
MRI->replaceRegWith(InsertedVal, ConstVal);
InsertedPHI->eraseFromParent();
InsertedVal = ConstVal;
} else {
DEBUG(dbgs() << " Inserted PHI: " << *InsertedPHI << "\n");
if (InsertedPHIs) InsertedPHIs->push_back(InsertedPHI);
}
return InsertedVal;
}