[PATCH] D104066: [SCEV] Use knowledge of stride to prove loops finite for LT exit count computation

[Max Kazantsev via Phabricator via llvm-commits]

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

Looks fine, but agreed with Eli. Please don't land it for some more days to find and fix miscompiles from underlying patches (if any).



================
Comment at: llvm/lib/Analysis/ScalarEvolution.cpp:11479
+
+    if (PredicatedIV || !NoWrap || isKnownNonPositive(Stride) || !StrideNonZero)
       return getCouldNotCompute();
----------------
Please refactor as
```
 if (PredicatedIV || !NoWrap || isKnownNonPositive(Stride))
      return getCouldNotCompute();
 bool StrideNonZero = loopIsFiniteByAssumption || isLoopEntryGuardedByCond ...
  if (!StrideNonZero )
      return getCouldNotCompute();
```

The dom tree walking is expensive, let's only do it if easy checks failed.


Repository:
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https://reviews.llvm.org/D104066