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Canonicalize shuffle(undef,x,mask) -> shuffle(x, undef,mask').

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@27727 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2006-04-16 00:03:56 +00:00
parent 730b45694b
commit 706126dac1
1 changed files with 22 additions and 2 deletions
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24
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -7046,8 +7046,6 @@ Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
if (isa<UndefValue>(Mask))
return ReplaceInstUsesWith(SVI, UndefValue::get(SVI.getType()));
// TODO: Canonicalize shuffle(undef,x) -> shuffle(x, undef).
// TODO: If we have shuffle(x, undef, mask) and any elements of mask refer to
// the undef, change them to undefs.
@ -7077,6 +7075,28 @@ Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
MadeChange = true;
}
// Canonicalize shuffle(undef,x,mask) -> shuffle(x, undef,mask').
if (isa<UndefValue>(LHS)) {
// shuffle(undef,x,<0,0,0,0>) -> undef.
if (isa<ConstantAggregateZero>(Mask))
return ReplaceInstUsesWith(SVI, UndefValue::get(SVI.getType()));
ConstantPacked *CPM = cast<ConstantPacked>(Mask);
std::vector<Constant*> Elts;
for (unsigned i = 0, e = CPM->getNumOperands(); i != e; ++i) {
if (isa<UndefValue>(CPM->getOperand(i)))
Elts.push_back(CPM->getOperand(i));
else {
unsigned EltNo = cast<ConstantUInt>(CPM->getOperand(i))->getRawValue();
if (EltNo >= e/2)
Elts.push_back(ConstantUInt::get(Type::UIntTy, EltNo-e/2));
else // Referring to the undef.
Elts.push_back(UndefValue::get(Type::UIntTy));
}
}
return new ShuffleVectorInst(RHS, LHS, ConstantPacked::get(Elts));
}
if (ConstantPacked *CP = dyn_cast<ConstantPacked>(Mask)) {
bool isLHSID = true, isRHSID = true;