[llvm] r211465 - Add a description to the test from r211433 explaining why it's written that way.

[Benjamin Kramer]

Author: d0k
Date: Sun Jun 22 07:22:04 2014
New Revision: 211465

URL: http://llvm.org/viewvc/llvm-project?rev=211465&view=rev
Log:
Add a description to the test from r211433 explaining why it's written that way.

Modified:
    llvm/trunk/test/Transforms/IndVarSimplify/2014-06-21-congruent-constant.ll

Modified: llvm/trunk/test/Transforms/IndVarSimplify/2014-06-21-congruent-constant.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IndVarSimplify/2014-06-21-congruent-constant.ll?rev=211465&r1=211464&r2=211465&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/IndVarSimplify/2014-06-21-congruent-constant.ll (original)
+++ llvm/trunk/test/Transforms/IndVarSimplify/2014-06-21-congruent-constant.ll Sun Jun 22 07:22:04 2014
@@ -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() {