[all-commits] [llvm/llvm-project] 4b7383: [CodeGen] Do not use subsituteRegister to update i...

[Peiming Liu via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 4b738387aeba477aa3c7c7d688fa9982cf1f2722
      https://github.com/llvm/llvm-project/commit/4b738387aeba477aa3c7c7d688fa9982cf1f2722
  Author: Peiming Liu <geticliu at gmail.com>
  Date:   2025-07-11 (Fri, 11 Jul 2025)

  Changed paths:
    M llvm/lib/CodeGen/TargetInstrInfo.cpp
    M llvm/test/CodeGen/X86/coalesce-commutative-implicit-def.mir

  Log Message:
  -----------
  [CodeGen] Do not use subsituteRegister to update implicit def (#148068)

It seems `subsituteRegister` checks `FromReg == ToReg` instead of
`TRI->isSubRegisterEq`.

This PR simply reverts the original PR
(https://github.com/llvm/llvm-project/pull/131361) to its initial
implementation (without using `subsituteRegister`).

Not sure whether it is a desired fix (and by no means that I am an
expert on LLVM backend), but it does fix a numeric error on our internal
workload.

Original author: @sdesmalen-arm



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