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Fold vector selects with undef elements in the condition. Fixes PR18319.

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Patch by Ilia Filippov!


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198267 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nick Lewycky
2013-12-31 19:30:47 +00:00
parent 5cbbd7e1a5
commit 99cebadb5c
3 changed files with 24 additions and 7 deletions
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21
lib/IR/ConstantFold.cpp
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@@ -705,12 +705,21 @@ Constant *llvm::ConstantFoldSelectInstruction(Constant *Cond,
SmallVector<Constant*, 16> Result;
Type *Ty = IntegerType::get(CondV->getContext(), 32);
for (unsigned i = 0, e = V1->getType()->getVectorNumElements(); i != e;++i){
ConstantInt *Cond = dyn_cast<ConstantInt>(CondV->getOperand(i));
if (Cond == 0) break;
Constant *V = Cond->isNullValue() ? V2 : V1;
Constant *Res = ConstantExpr::getExtractElement(V, ConstantInt::get(Ty, i));
Result.push_back(Res);
Constant *V;
Constant *V1Element = ConstantExpr::getExtractElement(V1,
ConstantInt::get(Ty, i));
Constant *V2Element = ConstantExpr::getExtractElement(V2,
ConstantInt::get(Ty, i));
Constant *Cond = dyn_cast<Constant>(CondV->getOperand(i));
if (V1Element == V2Element) {
V = V1Element;
} else if (isa<UndefValue>(Cond)) {
V = isa<UndefValue>(V1Element) ? V1Element : V2Element;
} else {
if (!isa<ConstantInt>(Cond)) break;
V = Cond->isNullValue() ? V2Element : V1Element;
}
Result.push_back(V);
}
// If we were able to build the vector, return it.