[all-commits] [llvm/llvm-project] 24d521: [InstCombine] add tests for add with not-of-mul co...

[Sanjay Patel via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 24d521815f6cf34944b0f6d3fa1acd1a881737f6
      https://github.com/llvm/llvm-project/commit/24d521815f6cf34944b0f6d3fa1acd1a881737f6
  Author: Sanjay Patel <spatel at rotateright.com>
  Date:   2022-08-24 (Wed, 24 Aug 2022)

  Changed paths:
    M llvm/test/Transforms/InstCombine/add.ll

  Log Message:
  -----------
  [InstCombine] add tests for add with not-of-mul common operand; NFC

Negator can create non-obvious math while trying hard to avoid subtraction.
issue #57255


  Commit: f7ab70cf8df6117312a2b76588269b9a1269a620
      https://github.com/llvm/llvm-project/commit/f7ab70cf8df6117312a2b76588269b9a1269a620
  Author: Sanjay Patel <spatel at rotateright.com>
  Date:   2022-08-24 (Wed, 24 Aug 2022)

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

  Log Message:
  -----------
  [InstCombine] reduce disguised mul+add factorization

~(A * C1) + A --> (A * (1 - C1)) - 1

This is a non-obvious mix of bitwise logic and math:
https://alive2.llvm.org/ce/z/U7ACVT

The pattern may be produced by Negator from the more typical
code seen in issue #57255.


Compare: https://github.com/llvm/llvm-project/compare/2c29268bfcc8...f7ab70cf8df6