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This optimization makes MANY phi nodes that all have the same incoming value.

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If this happens, detect it early instead of relying on instcombine to notice
it later.  This can be a big speedup, because PHI nodes can have many
incoming values.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@17741 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2004-11-14 19:29:34 +00:00
parent bac32866a7
commit b58934484b
1 changed files with 23 additions and 7 deletions
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30
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -3456,21 +3456,37 @@ Instruction *InstCombiner::FoldPHIArgOpIntoPHI(PHINode &PN) {
PHINode *NewPN = new PHINode(FirstInst->getOperand(0)->getType(),
PN.getName()+".in");
NewPN->op_reserve(PN.getNumOperands());
InsertNewInstBefore(NewPN, PN);
Value *InVal = FirstInst->getOperand(0);
NewPN->addIncoming(InVal, PN.getIncomingBlock(0));
// Add all operands to the new PHI.
for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
NewPN->addIncoming(cast<Instruction>(PN.getIncomingValue(i))->getOperand(0),
PN.getIncomingBlock(i));
for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i) {
Value *NewInVal = cast<Instruction>(PN.getIncomingValue(i))->getOperand(0);
if (NewInVal != InVal)
InVal = 0;
NewPN->addIncoming(NewInVal, PN.getIncomingBlock(i));
}
Value *PhiVal;
if (InVal) {
// The new PHI unions all of the same values together. This is really
// common, so we handle it intelligently here for compile-time speed.
PhiVal = InVal;
delete NewPN;
} else {
InsertNewInstBefore(NewPN, PN);
PhiVal = NewPN;
}
// Insert and return the new operation.
if (isa<CastInst>(FirstInst))
return new CastInst(NewPN, PN.getType());
return new CastInst(PhiVal, PN.getType());
else if (BinaryOperator *BinOp = dyn_cast<BinaryOperator>(FirstInst))
return BinaryOperator::create(BinOp->getOpcode(), NewPN, ConstantOp);
return BinaryOperator::create(BinOp->getOpcode(), PhiVal, ConstantOp);
else
return new ShiftInst(cast<ShiftInst>(FirstInst)->getOpcode(),
NewPN, ConstantOp);
PhiVal, ConstantOp);
}
// PHINode simplification