fix infinite loop in instcombine in the presence of a (malformed) self-referencing select inst.
This can happen as long as the instruction is not reachable. Instcombine does generate these unreachable malformed selects when doing RAUW
llvm-svn: 160874
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
index bdd97a8..291e800 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -881,12 +881,16 @@
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;
}
diff --git a/llvm/test/Transforms/InstCombine/select-crash.ll b/llvm/test/Transforms/InstCombine/select-crash.ll
index 18af152..946ea2b 100644
--- a/llvm/test/Transforms/InstCombine/select-crash.ll
+++ b/llvm/test/Transforms/InstCombine/select-crash.ll
@@ -30,3 +30,20 @@
%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
+}