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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@160874 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 17 insertions, 0 deletions

diff --git a/test/Transforms/InstCombine/select-crash.ll b/test/Transforms/InstCombine/select-crash.ll
index 18af152..946ea2b 100644
--- a/test/Transforms/InstCombine/select-crash.ll
+++ b/test/Transforms/InstCombine/select-crash.ll
@@ -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
+}