[PATCH] D103844: [SCEV] Cache wrap facts for positive IVs w/LT exits

[Nikita Popov via Phabricator via llvm-commits]

nikic added inline comments.


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Comment at: llvm/lib/Analysis/ScalarEvolution.cpp:11518
+    // We have proven that IV can not overflow, remember that fact.
+    setNoWrapFlags(const_cast<SCEVAddRecExpr *>(IV), WrapType);
   }
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If we consider the `canIVOverflowOnLT()` case, the only thin this guarantees is that `RHS + Stride - 1` does not overflow, it doesn't make a direct statement about the addrec.

If the loop exits before reaching this exit (for simplicity: abnormal exit on first iteration), then I don't think we can really make any statement about the nowrap behavior of the addrec.


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  https://reviews.llvm.org/D103844/new/

https://reviews.llvm.org/D103844