Add a description to the test from r211433 explaining why it's written that way.

llvm-svn: 211465
2014-06-22 12:22:04 +00:00 · 2014-06-22 12:22:04 +00:00 · f504ec2298
parent c5f3963bcb
commit f504ec2298
1 changed files with 6 additions and 0 deletions
--- a/llvm/test/Transforms/IndVarSimplify/2014-06-21-congruent-constant.ll
+++ b/llvm/test/Transforms/IndVarSimplify/2014-06-21-congruent-constant.ll
@ -1,5 +1,11 @@
 ; RUN: opt -S -loop-unswitch -instcombine -indvars < %s | FileCheck %s

+; This used to crash in SCEVExpander when there were congruent phis with and
+; undef incoming value from the loop header. The -loop-unswitch -instcombine is
+; necessary to create just this pattern, which is essentially a nop and gets
+; folded away aggressively if spelled out in IR directly.
+; PR 20093
+
@c = external global i32**, align 8

 define void @test1() {