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If we can look through vector operations to find the scalar version of an

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extract_element'd value, do so.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@27323 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2006-03-31 23:01:56 +00:00
parent 348ba3f9bf
commit 6e6b0da303
1 changed files with 40 additions and 0 deletions
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40
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -6654,7 +6654,41 @@ static bool CheapToScalarize(Value *V, bool isConstant) {
return false;
}
/// FindScalarElement - Given a vector and an element number, see if the scalar
/// value is already around as a register, for example if it were inserted then
/// extracted from the vector.
static Value *FindScalarElement(Value *V, unsigned EltNo) {
assert(isa<PackedType>(V->getType()) && "Not looking at a vector?");
const PackedType *PTy = cast<PackedType>(V->getType());
if (EltNo >= PTy->getNumElements()) // Out of range access.
return UndefValue::get(PTy->getElementType());
if (isa<UndefValue>(V))
return UndefValue::get(PTy->getElementType());
else if (isa<ConstantAggregateZero>(V))
return Constant::getNullValue(PTy->getElementType());
else if (ConstantPacked *CP = dyn_cast<ConstantPacked>(V))
return CP->getOperand(EltNo);
else if (InsertElementInst *III = dyn_cast<InsertElementInst>(V)) {
// If this is an insert to a variable element, we don't know what it is.
if (!isa<ConstantUInt>(III->getOperand(2))) return 0;
unsigned IIElt = cast<ConstantUInt>(III->getOperand(2))->getValue();
// If this is an insert to the element we are looking for, return the
// inserted value.
if (EltNo == IIElt) return III->getOperand(1);
// Otherwise, the insertelement doesn't modify the value, recurse on its
// vector input.
return FindScalarElement(III->getOperand(0), EltNo);
}
// Otherwise, we don't know.
return 0;
}
Instruction *InstCombiner::visitExtractElementInst(ExtractElementInst &EI) {
// If packed val is undef, replace extract with scalar undef.
if (isa<UndefValue>(EI.getOperand(0)))
return ReplaceInstUsesWith(EI, UndefValue::get(EI.getType()));
@ -6676,6 +6710,12 @@ Instruction *InstCombiner::visitExtractElementInst(ExtractElementInst &EI) {
return ReplaceInstUsesWith(EI, op0);
}
// If extracting a specified index from the vector, see if we can recursively
// find a previously computed scalar that was inserted into the vector.
if (ConstantUInt *IdxC = dyn_cast<ConstantUInt>(EI.getOperand(1)))
if (Value *Elt = FindScalarElement(EI.getOperand(0), IdxC->getValue()))
return ReplaceInstUsesWith(EI, Elt);
if (Instruction *I = dyn_cast<Instruction>(EI.getOperand(0)))
if (I->hasOneUse()) {
// Push extractelement into predecessor operation if legal and