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Constfold insertelement to undef when index is out-of-bounds

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Summary:
This patch adds constant folding of insertelement instruction to undef value when index operand is constant and is not less than vector size or is undef.

InstCombine does not support this case, but I'm happy to add it there also if this change is accepted.

Test Plan: Unittests and regression tests for ConstProp pass.

Reviewers: majnemer

Reviewed By: majnemer

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D9287

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@235854 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Pawel Bylica
2015-04-27 09:30:49 +00:00
parent 6df35e7844
commit 59764b94a7
3 changed files with 48 additions and 12 deletions
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21
lib/IR/ConstantFold.cpp
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@@ -800,23 +800,30 @@ Constant *llvm::ConstantFoldExtractElementInstruction(Constant *Val,
Constant *llvm::ConstantFoldInsertElementInstruction(Constant *Val,
Constant *Elt,
Constant *Idx) {
if (isa<UndefValue>(Idx))
return UndefValue::get(Val->getType());
ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx);
if (!CIdx) return nullptr;
const APInt &IdxVal = CIdx->getValue();
unsigned NumElts = Val->getType()->getVectorNumElements();
if (CIdx->uge(NumElts))
return UndefValue::get(Val->getType());
SmallVector<Constant*, 16> Result;
Type *Ty = IntegerType::get(Val->getContext(), 32);
for (unsigned i = 0, e = Val->getType()->getVectorNumElements(); i != e; ++i){
Result.reserve(NumElts);
auto *Ty = Type::getInt32Ty(Val->getContext());
uint64_t IdxVal = CIdx->getZExtValue();
for (unsigned i = 0; i != NumElts; ++i) {
if (i == IdxVal) {
Result.push_back(Elt);
continue;
}
Constant *C =
ConstantExpr::getExtractElement(Val, ConstantInt::get(Ty, i));
Constant *C = ConstantExpr::getExtractElement(Val, ConstantInt::get(Ty, i));
Result.push_back(C);
}
return ConstantVector::get(Result);
}