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remove some harmful code that would turn an insertelement on an undef

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into a shuffle even if it was used by another insertelement.  If the
visitation order of instcombine was wrong, this would turn a chain of
insertelements into a chain of shufflevectors, which was quite painful.

Since CollectShuffleElements handles these cases, the code can just
be nuked.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@83810 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2009-10-11 23:02:46 +00:00
parent aca471f3a5
commit 2ad8cf5555
1 changed files with 0 additions and 22 deletions
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22
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -12472,28 +12472,6 @@ Instruction *InstCombiner::visitInsertElementInst(InsertElementInst &IE) {
if (EI->getOperand(0) == VecOp && ExtractedIdx == InsertedIdx)
return ReplaceInstUsesWith(IE, VecOp);
// We could theoretically do this for ANY input. However, doing so could
// turn chains of insertelement instructions into a chain of shufflevector
// instructions, and right now we do not merge shufflevectors. As such,
// only do this in a situation where it is clear that there is benefit.
if (isa<UndefValue>(VecOp) || isa<ConstantAggregateZero>(VecOp)) {
// Turn this into shuffle(EIOp0, VecOp, Mask). The result has all of
// the values of VecOp, except then one read from EIOp0.
// Build a new shuffle mask.
std::vector<Constant*> Mask;
if (isa<UndefValue>(VecOp))
Mask.assign(NumVectorElts, UndefValue::get(Type::getInt32Ty(*Context)));
else {
assert(isa<ConstantAggregateZero>(VecOp) && "Unknown thing");
Mask.assign(NumVectorElts, ConstantInt::get(Type::getInt32Ty(*Context),
NumVectorElts));
}
Mask[InsertedIdx] =
ConstantInt::get(Type::getInt32Ty(*Context), ExtractedIdx);
return new ShuffleVectorInst(EI->getOperand(0), VecOp,
ConstantVector::get(Mask));
}
// If this insertelement isn't used by some other insertelement, turn it
// (and any insertelements it points to), into one big shuffle.
if (!IE.hasOneUse() || !isa<InsertElementInst>(IE.use_back())) {