[all-commits] [llvm/llvm-project] 434369: [LICM] Don't try to constant fold instructions

[Nikita Popov via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 43436993f48b1d75d9d80796cb0889ce7d191888
      https://github.com/llvm/llvm-project/commit/43436993f48b1d75d9d80796cb0889ce7d191888
  Author: Nikita Popov <npopov at redhat.com>
  Date:   2023-04-26 (Wed, 26 Apr 2023)

  Changed paths:
    M llvm/lib/Transforms/Scalar/LICM.cpp
    M llvm/test/Transforms/LICM/hoisting.ll
    M llvm/test/Transforms/LICM/pr32129.ll
    M llvm/test/Transforms/LICM/scalar-promote.ll

  Log Message:
  -----------
  [LICM] Don't try to constant fold instructions

This was introduced in 030f02021b6359ec5641622cf1aa63d873ecf55a as
an alleged compile-time optimization. In reality, trying to constant
fold instructions is more expensive than just hoisting them. In a
standard pipeline, LICM tends to run either after a run of
LoopInstSimplify or InstCombine, so LICM doesn't really see constant
foldable instructions in the first place, and the attempted fold
is futile.

This makes for a very minor compile-time improvement.

Differential Revision: https://reviews.llvm.org/D149134