[all-commits] [llvm/llvm-project] ffe05d: [InstCombine] usub.sat(a, b) + b => umax(a, b) (PR...

[Nikita Popov via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: ffe05dd12593f979f235cd34fd467a4c30e051f8
      https://github.com/llvm/llvm-project/commit/ffe05dd12593f979f235cd34fd467a4c30e051f8
  Author: Nikita Popov <nikita.ppv at gmail.com>
  Date:   2020-08-28 (Fri, 28 Aug 2020)

  Changed paths:
    M llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
    M llvm/test/Transforms/InstCombine/saturating-add-sub.ll

  Log Message:
  -----------
  [InstCombine] usub.sat(a, b) + b => umax(a, b) (PR42178)

Fixes https://bugs.llvm.org/show_bug.cgi?id=42178 by folding
usub.sat(a, b) + b to umax(a, b). The backend will expand umax
back to usubsat if that is profitable.

We may also want to handle uadd.sat(a, b) - b in the future.

Differential Revision: https://reviews.llvm.org/D63060