[all-commits] [llvm/llvm-project] 0cfc65: [InstCombine] ease use constraint in tryFactorizat...

[Sanjay Patel via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 0cfc6510323fbb5a56a5de23cbc65f7cc30fd34c
      https://github.com/llvm/llvm-project/commit/0cfc6510323fbb5a56a5de23cbc65f7cc30fd34c
  Author: Sanjay Patel <spatel at rotateright.com>
  Date:   2022-08-24 (Wed, 24 Aug 2022)

  Changed paths:
    M llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
    M llvm/test/Transforms/InstCombine/add.ll
    M llvm/test/Transforms/InstCombine/and-or.ll
    M llvm/test/Transforms/InstCombine/ctpop.ll
    M llvm/test/Transforms/InstCombine/sub.ll

  Log Message:
  -----------
  [InstCombine] ease use constraint in tryFactorization()

The stronger one-use checks prevented transforms like this:
(x * y) + x --> x * (y + 1)
(x * y) - x --> x * (y - 1)

https://alive2.llvm.org/ce/z/eMhvQa

This is one of the IR transforms suggested in issue #57255.

This should be better in IR because it removes a use of a
variable operand (we already fold the case with a constant
multiply operand).
The backend should be able to re-distribute the multiply if
that's better for the target.

Differential Revision: https://reviews.llvm.org/D132412