Fix PR8161, in which an unreachable loop causes recursive instruction simplification to try

to replace an instruction with itself.  Add a predicate to the simplifier to prevent this case.

llvm-svn: 114097

1 files changed, 20 insertions, 0 deletions

diff --git a/llvm/test/Transforms/CorrelatedValuePropagation/crash.ll b/llvm/test/Transforms/CorrelatedValuePropagation/crash.ll
new file mode 100644
index 00000000000..8636788511e
--- /dev/null
+++ b/llvm/test/Transforms/CorrelatedValuePropagation/crash.ll
@@ -0,0 +1,20 @@
+; RUN: opt < %s -correlated-propagation
+
+; PR8161
+define void @test1() nounwind ssp {
+entry:
+  br label %for.end
+
+for.cond.us.us:                                   ; preds = %for.cond.us.us
+  %cmp6.i.us.us = icmp sgt i32 1, 0
+  %lor.ext.i.us.us = zext i1 %cmp6.i.us.us to i32
+  %lor.ext.add.i.us.us = select i1 %cmp6.i.us.us, i32 %lor.ext.i.us.us, i32 undef
+  %conv.i.us.us = trunc i32 %lor.ext.add.i.us.us to i16
+  %sext.us.us = shl i16 %conv.i.us.us, 8
+  %conv6.us.us = ashr i16 %sext.us.us, 8
+  %and.us.us = and i16 %conv6.us.us, %and.us.us
+  br i1 false, label %for.end, label %for.cond.us.us
+
+for.end:                                          ; preds = %for.cond.us, %for.cond.us.us, %entry
+  ret void
+}