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InstCombine: Fix infinite loop when encountering switch on trivial icmp.

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The test case feeds the following into InstCombine's visitSelect:
%tobool8 = icmp ne i32 0, 0
%phitmp = select i1 %tobool8, i32 3, i32 0
Then instcombine replaces the right side of the switch with 0, doesn't notice
that nothing changes and tries again indefinitely.

This fixes PR12897.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@157587 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Benjamin Kramer
2012-05-28 19:18:16 +00:00
parent 21280e48c0
commit 37fa1c81ac
2 changed files with 40 additions and 1 deletions
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2
lib/Transforms/InstCombine/InstCombineSelect.cpp
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@@ -498,7 +498,7 @@ Instruction *InstCombiner::visitSelectInstWithICmp(SelectInst &SI,
// NOTE: if we wanted to, this is where to detect integer MIN/MAX
if (isa<Constant>(CmpRHS)) {
if (CmpRHS != CmpLHS && isa<Constant>(CmpRHS)) {
if (CmpLHS == TrueVal && Pred == ICmpInst::ICMP_EQ) {
// Transform (X == C) ? X : Y -> (X == C) ? C : Y
SI.setOperand(1, CmpRHS);