[PATCH] D56837: [IRCE] Support narrow latch condition for wide range checks

[Philip Reames via Phabricator via llvm-commits]

reames accepted this revision.
reames added a comment.
This revision is now accepted and ready to land.

Please land w/flag disabled.  Wait until bots cycle, then enable flag separately.



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Comment at: lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp:1071
     return None;
 
   LoopConstrainer::SubRanges Result;
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mkazantsev wrote:
> reames wrote:
> > I can't convince myself this is correct when the IV would overflow.  Can you explain why we don't need some form of overflow check here?  Note that in LoopPredication in isSafeToTruncate, we *do* have an overflow check.
> We should not be doing IRCE if IV overflows its type. This is guaranteed by functions `isSafeIncreasingBound`, `isSafeDecreasingBound`. I will add some more tests to ensure that, but I'm pretty sure that we already have plenty.
> 
I followed through the code, questions answered.


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