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Reapply r237520 with another fix for infinite looping

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SimplifyDemandedBits was "simplifying" a constant by removing just sign bits.
This caused a canonicalization race between different parts of instcombine.

Fix and regression test added - third time lucky?

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@237539 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
James Molloy
2015-05-17 08:27:27 +00:00
parent a0eb803376
commit 2bb2ea8105
6 changed files with 162 additions and 7 deletions
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24
lib/Transforms/InstCombine/InstCombineSelect.cpp
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@@ -1154,18 +1154,30 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
}
// See if we can fold the select into one of our operands.
if (SI.getType()->isIntegerTy()) {
if (SI.getType()->isIntOrIntVectorTy()) {
if (Instruction *FoldI = FoldSelectIntoOp(SI, TrueVal, FalseVal))
return FoldI;
Value *LHS, *RHS, *LHS2, *RHS2;
SelectPatternFlavor SPF = matchSelectPattern(&SI, LHS, RHS);
Instruction::CastOps CastOp;
SelectPatternFlavor SPF = matchSelectPattern(&SI, LHS, RHS, &CastOp);
// MAX(MAX(a, b), a) -> MAX(a, b)
// MIN(MIN(a, b), a) -> MIN(a, b)
// MAX(MIN(a, b), a) -> a
// MIN(MAX(a, b), a) -> a
if (SPF) {
// Canonicalize so that type casts are outside select patterns.
if (LHS->getType()->getPrimitiveSizeInBits() !=
SI.getType()->getPrimitiveSizeInBits()) {
CmpInst::Predicate Pred = getICmpPredicateForMinMax(SPF);
Value *Cmp = Builder->CreateICmp(Pred, LHS, RHS);
Value *NewSI = Builder->CreateCast(CastOp,
Builder->CreateSelect(Cmp, LHS, RHS),
SI.getType());
return ReplaceInstUsesWith(SI, NewSI);
}
// MAX(MAX(a, b), a) -> MAX(a, b)
// MIN(MIN(a, b), a) -> MIN(a, b)
// MAX(MIN(a, b), a) -> a
// MIN(MAX(a, b), a) -> a
if (SelectPatternFlavor SPF2 = matchSelectPattern(LHS, LHS2, RHS2))
if (Instruction *R = FoldSPFofSPF(cast<Instruction>(LHS),SPF2,LHS2,RHS2,
SI, SPF, RHS))