[PATCH] D118090: [ScalarEvolution] Handle <= and >= in non infinite loops

[Philip Reames via Phabricator via llvm-commits]

reames added inline comments.


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Comment at: llvm/lib/Analysis/LoopInfo.cpp:1122
+  return L->getHeader()->getParent()->mustProgress() || hasMustProgress(L) ||
+         isFinite(L);
 }
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This is - in the current patch - a form of attribute inference.  We prefer inference be done once - either in the core API itself, or explicitly via materialization in IR - not duplicated for each consumer.

i.e. Calling code should assume that willreturn loops are mustprogress, not check for that case explicitly.  


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Comment at: llvm/lib/Analysis/ScalarEvolution.cpp:7020
   // side effects which are well defined in infinite loops.
-  return isMustProgress(L) && loopHasNoSideEffects(L);
+  return isFinite(L) || (isMustProgress(L) && loopHasNoSideEffects(L));
 }
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This change by itself should be testable and profitable.  I'd advise separating the SimplifyICmpOperands bits into a following change. 

Or said differently, a patch which causes loopIsFiniteByAssumption for loops in willreturn functions seems entirely reasonable on it's own without any new metadata.  


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D118090/new/

https://reviews.llvm.org/D118090