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Don't try to be cute with undef optimization here. Let ProcessImplicitDefs handle it. 

llvm-svn: 90566
This commit is contained in:
Evan Cheng 2009-12-04 09:23:37 +00:00
parent 65d87222b2
commit 0f1cc35c65
1 changed files with 17 additions and 27 deletions
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44
llvm/lib/CodeGen/MachineSSAUpdater.cpp
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@ -94,7 +94,7 @@ MachineInstr *InsertNewDef(unsigned Opcode,
const TargetRegisterClass *RC,
MachineRegisterInfo *MRI, const TargetInstrInfo *TII) {
unsigned NewVR = MRI->createVirtualRegister(RC);
return BuildMI(*BB, I, I->getDebugLoc(), TII->get(Opcode), NewVR);
return BuildMI(*BB, I, DebugLoc::getUnknownLoc(), TII->get(Opcode), NewVR);
}
@ -124,8 +124,13 @@ unsigned MachineSSAUpdater::GetValueInMiddleOfBlock(MachineBasicBlock *BB) {
return GetValueAtEndOfBlock(BB);
// If there are no predecessors, just return undef.
if (BB->pred_empty())
return ~0U; // Sentinel value representing undef.
if (BB->pred_empty()) {
// Insert an implicit_def to represent an undef value.
MachineInstr *NewDef = InsertNewDef(TargetInstrInfo::IMPLICIT_DEF,
BB, BB->getFirstTerminator(),
VRC, MRI, TII);
return NewDef->getOperand(0).getReg();
}
// Otherwise, we have the hard case. Get the live-in values for each
// predecessor.
@ -194,20 +199,8 @@ void MachineSSAUpdater::RewriteUse(MachineOperand &U) {
if (UseMI->getOpcode() == TargetInstrInfo::PHI) {
MachineBasicBlock *SourceBB = findCorrespondingPred(UseMI, &U);
NewVR = GetValueAtEndOfBlock(SourceBB);
// Insert an implicit_def to represent an undef value.
MachineInstr *NewDef = InsertNewDef(TargetInstrInfo::IMPLICIT_DEF,
SourceBB,SourceBB->getFirstTerminator(),
VRC, MRI, TII);
NewVR = NewDef->getOperand(0).getReg();
} else {
NewVR = GetValueInMiddleOfBlock(UseMI->getParent());
if (NewVR == ~0U) {
// Insert an implicit_def to represent an undef value.
MachineInstr *NewDef = InsertNewDef(TargetInstrInfo::IMPLICIT_DEF,
UseMI->getParent(), UseMI,
VRC, MRI, TII);
NewVR = NewDef->getOperand(0).getReg();
}
}
U.setReg(NewVR);
@ -248,8 +241,13 @@ unsigned MachineSSAUpdater::GetValueAtEndOfBlockInternal(MachineBasicBlock *BB){
// If there are no predecessors, then we must have found an unreachable block
// just return 'undef'. Since there are no predecessors, InsertRes must not
// be invalidated.
if (BB->pred_empty())
return InsertRes.first->second = ~0U; // Sentinel value representing undef.
if (BB->pred_empty()) {
// Insert an implicit_def to represent an undef value.
MachineInstr *NewDef = InsertNewDef(TargetInstrInfo::IMPLICIT_DEF,
BB, BB->getFirstTerminator(),
VRC, MRI, TII);
return InsertRes.first->second = NewDef->getOperand(0).getReg();
}
// Okay, the value isn't in the map and we just inserted a null in the entry
// to indicate that we're processing the block. Since we have no idea what
@ -321,16 +319,11 @@ unsigned MachineSSAUpdater::GetValueAtEndOfBlockInternal(MachineBasicBlock *BB){
}
// Fill in all the predecessors of the PHI.
bool IsUndef = true;
MachineInstrBuilder MIB(InsertedPHI);
for (IncomingPredInfoTy::iterator I =
IncomingPredInfo.begin()+FirstPredInfoEntry,
E = IncomingPredInfo.end(); I != E; ++I) {
if (I->second == ~0U)
continue;
IsUndef = false;
E = IncomingPredInfo.end(); I != E; ++I)
MIB.addReg(I->second).addMBB(I->first);
}
// Drop the entries we added in IncomingPredInfo to restore the stack.
IncomingPredInfo.erase(IncomingPredInfo.begin()+FirstPredInfoEntry,
@ -338,10 +331,7 @@ unsigned MachineSSAUpdater::GetValueAtEndOfBlockInternal(MachineBasicBlock *BB){
// See if the PHI node can be merged to a single value. This can happen in
// loop cases when we get a PHI of itself and one other value.
if (IsUndef) {
InsertedPHI->eraseFromParent();
InsertedVal = ~0U;
} else if (unsigned ConstVal = InsertedPHI->isConstantValuePHI()) {
if (unsigned ConstVal = InsertedPHI->isConstantValuePHI()) {
MRI->replaceRegWith(InsertedVal, ConstVal);
InsertedPHI->eraseFromParent();
InsertedVal = ConstVal;