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fix infinite loop in instcombine in the presence of a (malformed) self-referencing select inst.

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This can happen as long as the instruction is not reachable. Instcombine does generate these unreachable malformed selects when doing RAUW

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@160874 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nuno Lopes 2012-07-27 18:03:57 +00:00
parent 2e319870f1
commit 75564e3514
2 changed files with 21 additions and 0 deletions
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4
lib/Transforms/InstCombine/InstCombineSelect.cpp
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@ -881,12 +881,16 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
if (SelectInst *TrueSI = dyn_cast<SelectInst>(TrueVal)) {
if (TrueSI->getCondition() == CondVal) {
if (SI.getTrueValue() == TrueSI->getTrueValue())
return 0;
SI.setOperand(1, TrueSI->getTrueValue());
return &SI;
}
}
if (SelectInst *FalseSI = dyn_cast<SelectInst>(FalseVal)) {
if (FalseSI->getCondition() == CondVal) {
if (SI.getFalseValue() == FalseSI->getFalseValue())
return 0;
SI.setOperand(2, FalseSI->getFalseValue());
return &SI;
}

17
test/Transforms/InstCombine/select-crash.ll
View File

@ -30,3 +30,20 @@ define <4 x float> @foo(i1 %b, <4 x float> %x, <4 x float> %y, <4 x float> %z) {
%sel = select i1 %b, <4 x float> %a, <4 x float> %sub
ret <4 x float> %sel
}
; CHECK: @test3
define i32 @test3(i1 %bool, i32 %a) {
entry:
%cond = or i1 %bool, true
br i1 %cond, label %return, label %xpto
; technically reachable, but this malformed IR may appear as a result of constant propagation
xpto:
%select = select i1 %bool, i32 %a, i32 %select
%select2 = select i1 %bool, i32 %select2, i32 %a
%sum = add i32 %select, %select2
ret i32 %sum
return:
ret i32 7
}