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Implement InstCombine/vec_shuffle.ll:%test7, simplifying shuffles with 

undef operands.

llvm-svn: 32899
This commit is contained in:
Chris Lattner 2007-01-05 07:36:08 +00:00
parent e4f7c5cf35
commit d7b6ea166d
1 changed files with 23 additions and 1 deletions
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24
llvm/lib/Transforms/Scalar/InstructionCombining.cpp
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@ -8833,8 +8833,30 @@ Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
if (isa<UndefValue>(SVI.getOperand(2)))
return ReplaceInstUsesWith(SVI, UndefValue::get(SVI.getType()));
// TODO: If we have shuffle(x, undef, mask) and any elements of mask refer to
// If we have shuffle(x, undef, mask) and any elements of mask refer to
// the undef, change them to undefs.
if (isa<UndefValue>(SVI.getOperand(1))) {
// Scan to see if there are any references to the RHS. If so, replace them
// with undef element refs and set MadeChange to true.
for (unsigned i = 0, e = Mask.size(); i != e; ++i) {
if (Mask[i] >= e && Mask[i] != 2*e) {
Mask[i] = 2*e;
MadeChange = true;
}
}
if (MadeChange) {
// Remap any references to RHS to use LHS.
std::vector<Constant*> Elts;
for (unsigned i = 0, e = Mask.size(); i != e; ++i) {
if (Mask[i] == 2*e)
Elts.push_back(UndefValue::get(Type::Int32Ty));
else
Elts.push_back(ConstantInt::get(Type::Int32Ty, Mask[i]));
}
SVI.setOperand(2, ConstantPacked::get(Elts));
}
}
// Canonicalize shuffle(x ,x,mask) -> shuffle(x, undef,mask')
// Canonicalize shuffle(undef,x,mask) -> shuffle(x, undef,mask').