[all-commits] [llvm/llvm-project] c42c32: [InstCombine] Add reverse of ((X << nuw Z) sub nuw...

[AtariDreams via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: c42c32088bdb03e39ed24f4800a447d4cbb788f2
      https://github.com/llvm/llvm-project/commit/c42c32088bdb03e39ed24f4800a447d4cbb788f2
  Author: AtariDreams <gfunni234 at gmail.com>
  Date:   2024-05-26 (Sun, 26 May 2024)

  Changed paths:
    M llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
    M llvm/test/Transforms/InstCombine/lshr.ll

  Log Message:
  -----------
  [InstCombine] Add reverse of ((X << nuw Z) sub nuw Y) >>u exact Z --> X sub nuw (Y >>u exact Z) (#91386)

This is the same fold as ((X << nuw Z) sub nuw Y) >>u exact Z --> X sub
nuw (Y >>u exact Z), which we already have and approved in the codebase, but with the sub operands
swapped.

Proof it works in reverse, so we could have a wider generalization of this pattern: https://alive2.llvm.org/ce/z/2cRcdx



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