[llvm] r330677 - [NFC] Add clarification comment

[Max Kazantsev via llvm-commits]

Author: mkazantsev
Date: Mon Apr 23 19:08:05 2018
New Revision: 330677

URL: http://llvm.org/viewvc/llvm-project?rev=330677&view=rev
Log:
[NFC] Add clarification comment

Modified:
    llvm/trunk/lib/Transforms/Utils/LoopRotationUtils.cpp

Modified: llvm/trunk/lib/Transforms/Utils/LoopRotationUtils.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/LoopRotationUtils.cpp?rev=330677&r1=330676&r2=330677&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/LoopRotationUtils.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/LoopRotationUtils.cpp Mon Apr 23 19:08:05 2018
@@ -259,8 +259,10 @@ bool LoopRotate::rotateLoop(Loop *L, boo
     return false;
 
   // Anything ScalarEvolution may know about this loop or the PHI nodes
-  // in its header will soon be invalidated, and it can also affect its parent
-  // loops as well.
+  // in its header will soon be invalidated. We should also invalidate
+  // all outer loops because insertion and deletion of blocks that happens
+  // during the rotation may violate invariants related to backedge taken
+  // infos in them.
   if (SE)
     SE->forgetTopmostLoop(L);