[PATCH] D104634: [SCEV] Generalize MatchBinaryAddToConst to support non-add expressions.
Max Kazantsev via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Mon Jun 21 06:04:47 PDT 2021
mkazantsev added inline comments.
================
Comment at: llvm/lib/Analysis/ScalarEvolution.cpp:10106
case ICmpInst::ICMP_SLE:
- // X s<= (X + C)<nsw> if C >= 0
- if (MatchBinaryAddToConst(RHS, LHS, C, SCEV::FlagNSW) && C.isNonNegative())
+ // (X + C1)<nsw> s<= (X + C2) if C1 s<= C2.
+ if (MatchBinaryAddToConst(LHS, RHS, C1, C2, SCEV::FlagNSW) && C1.sle(C2))
----------------
mkazantsev wrote:
> Is lack of `nsw` in `(X + C2)` intentional? If yes, the counter-example to this is
>
> ```
> X = SINT_MIN
> C1 = 1
> C2 = -1
> ```
> `(X + C1)<nsw> = SINT_MIN + 1 <= (X - 1) = SINT_MAX`, but obviously `C1 > C2`.
>
>
I'm not sure whether two-ways implication is required here, or one way implication is enough. It was two-ways in old code. If I'm wrong here, please let me know.
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CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D104634/new/
https://reviews.llvm.org/D104634
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