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[Reassociate] Don't propogate flags when creating negations

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Reassociate mutated existing instructions in order to form negations
which would create additional reassociate opportunities.

This fixes PR23926.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@240593 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Majnemer
2015-06-24 21:27:36 +00:00
parent 613afa1372
commit 95a741163f
3 changed files with 27 additions and 2 deletions
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10
lib/Transforms/Scalar/Reassociate.cpp
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@@ -936,6 +936,10 @@ static Value *NegateValue(Value *V, Instruction *BI) {
// Push the negates through the add.
I->setOperand(0, NegateValue(I->getOperand(0), BI));
I->setOperand(1, NegateValue(I->getOperand(1), BI));
if (I->getOpcode() == Instruction::Add) {
I->setHasNoUnsignedWrap(false);
I->setHasNoSignedWrap(false);
}
// We must move the add instruction here, because the neg instructions do
// not dominate the old add instruction in general. By moving it, we are
@@ -976,6 +980,12 @@ static Value *NegateValue(Value *V, Instruction *BI) {
InsertPt = TheNeg->getParent()->getParent()->getEntryBlock().begin();
}
TheNeg->moveBefore(InsertPt);
if (TheNeg->getOpcode() == Instruction::Sub) {
TheNeg->setHasNoUnsignedWrap(false);
TheNeg->setHasNoSignedWrap(false);
} else {
TheNeg->andIRFlags(BI);
}
return TheNeg;
}