[PATCH] D133020: [LAA] Fix ICE with scAddExpr in forked pointers

[Graham Hunter via Phabricator via llvm-commits]

huntergr marked an inline comment as done.
huntergr added inline comments.


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Comment at: llvm/test/Analysis/LoopAccessAnalysis/forked-pointers.ll:899
+; CHECK-NEXT:       Group [[G2]]:
+; CHECK-NEXT:         (Low: %0 High: %0)
+; CHECK-NEXT:           Member: {%0,+,8}<%for.body.us>
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fhahn wrote:
> huntergr wrote:
> > This concerns me a bit -- the lower bound is correct, but the upper bound seems wrong. But that isn't related to my forked pointers patch -- I get the same output if I comment out the forked pointer detection code entirely.
> This is probably because PSE a predicate for this. The loop has an IV that start at 0 and we only exit if `iv == 0`. This can only happen if `iv` overflows AFAICT. But the IV increment is ` add nuw nsw i64 %indvars.iv.us1, 1`, so if it overflows it is UB.
> 
> Can the issue be reproduced with a loop that doesn't have UB, e.g. replacing the existing exit check with something like `cmp eq i64 %indvars.iv.next.us,  %N`?
You're right, thanks. I see `(Low: %Base2 High: ((8 * %N) + %Base2))` if I add a parameter for iterations.


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  https://reviews.llvm.org/D133020/new/

https://reviews.llvm.org/D133020