[PATCH] D156499: [InstCombine] Fold abs of known sign operand when source is sub
Nikita Popov via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Fri Jul 28 02:18:04 PDT 2023
nikic added inline comments.
================
Comment at: llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp:1032
+ isImpliedByDomCondition(ICmpInst::ICMP_SLE, X, Y, CxtI, DL))
+ return Known;
+ }
----------------
This looks incorrect from the perspective of the getKnownSign() API. You are returning sign 1 for value 0, which is incorrect. It does work out for the abs optimization because -0 == 0, but it may matter in other cases.
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D156499/new/
https://reviews.llvm.org/D156499
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