[PATCH] D98222: [SCEV] Use trip count information to improve shift recurrence ranges

[Philip Reames via Phabricator via llvm-commits]

reames added inline comments.


================
Comment at: llvm/lib/Analysis/ScalarEvolution.cpp:5655
+  if (!L || L->getHeader() != P->getParent())
+    return CR;
+
----------------
reames wrote:
> mkazantsev wrote:
> > `LI.isLoopHeader(P->getParent())`?
> > I also wonder why is that needed. The implementation of `matchSimpleRecurrence` cannot recognize something which is not a header phi, because there is no other way to have BO as operand of Phi and vice versa at the same time. I guess this may be turned into assert after `matchSimpleRecurrence`.
> You're right, this can become an assert.  It made since before some refactoring I did to the code before commit.   Not so much anymore.  Will fix.  
Hm, funny story.  It turns out this needs to be a bail out after all.  Not because it should be, but because asserting it exposes a bug in LoopFusion.  I'm putting a careful comment in the code and have filed PR49566 to track the issue.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D98222/new/

https://reviews.llvm.org/D98222