[all-commits] [llvm/llvm-project] aad3a1: [ValueTracking] Respect `samesign` flag in `isKnow...

[Yingwei Zheng via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: aad3a1630e385a6834f92a5f1d6045451ba21e4e
      https://github.com/llvm/llvm-project/commit/aad3a1630e385a6834f92a5f1d6045451ba21e4e
  Author: Yingwei Zheng <dtcxzyw2333 at gmail.com>
  Date:   2024-10-17 (Thu, 17 Oct 2024)

  Changed paths:
    M llvm/lib/Analysis/ValueTracking.cpp
    M llvm/test/Transforms/InstCombine/select-cmp.ll

  Log Message:
  -----------
  [ValueTracking] Respect `samesign` flag in `isKnownInversion` (#112390)

In https://github.com/llvm/llvm-project/pull/93591 we introduced
`isKnownInversion` and assumes `X` is poison implies `Y` is poison
because they share common operands. But after introducing `samesign`
this assumption no longer hold if `X` is an icmp has `samesign` flag.

Alive2 link: https://alive2.llvm.org/ce/z/rj3EwQ (Please run it locally
with this patch and https://github.com/AliveToolkit/alive2/pull/1098).

This approach is the most conservative way in my mind to address this
problem. If `X` has `samesign` flag, it will check if `Y` also has this
flag and make sure constant RHS operands have the same sign.

Fixes https://github.com/llvm/llvm-project/issues/112350.



To unsubscribe from these emails, change your notification settings at https://github.com/llvm/llvm-project/settings/notifications