[all-commits] [llvm/llvm-project] 01e724: [MachineLICM] Let targets decide if copy-like inst...

[Guy David via All-commits]

  Branch: refs/heads/users/guy-david/licm-hoist-copy-like
  Home:   https://github.com/llvm/llvm-project
  Commit: 01e724e06be4d47d897cf6d3c96f92b741c951c2
      https://github.com/llvm/llvm-project/commit/01e724e06be4d47d897cf6d3c96f92b741c951c2
  Author: Guy David <guyda96 at gmail.com>
  Date:   2025-07-04 (Fri, 04 Jul 2025)

  Changed paths:
    M llvm/lib/CodeGen/MachineLICM.cpp
    M llvm/test/CodeGen/PowerPC/vsx-fma-m-early.ll
    R llvm/test/CodeGen/X86/memfold-mov32r0.ll
    A llvm/test/CodeGen/X86/memfold-mov32r0.mir
    M llvm/test/CodeGen/X86/pr57673.ll

  Log Message:
  -----------
  [MachineLICM] Let targets decide if copy-like instructions are cheap

When checking whether it is profitable to hoist an instruction, the pass
may override a target's ruling because it assumes that all COPY
instructions are cheap, and that may not be the case for all
micro-architectures.

On AArch64 there's 0% difference in performance in LLVM's test-suite.
Additionally, very few tests were affected by this change which shows
how useful it is to keep it.



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