[all-commits] [llvm/llvm-project] d00b0a: RegisterCoalescer: Fix verifier error when merging...

[Matt Arsenault via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: d00b0aab31405432fad7bbaebccc0ae0956d6d39
      https://github.com/llvm/llvm-project/commit/d00b0aab31405432fad7bbaebccc0ae0956d6d39
  Author: Matt Arsenault <Matthew.Arsenault at amd.com>
  Date:   2022-09-13 (Tue, 13 Sep 2022)

  Changed paths:
    M llvm/lib/CodeGen/RegisterCoalescer.cpp
    A llvm/test/CodeGen/AMDGPU/coalesce-liveout-undef-copy.mir
    M llvm/test/CodeGen/AMDGPU/undef-subreg-use-after-coalesce.mir

  Log Message:
  -----------
  RegisterCoalescer: Fix verifier error when merging copy of undef

There's no real read of the register, so the copy introduced a new
live value. Make sure we introduce a replacement implicit_def instead
of just erasing the copy.

Found from llvm-reduce since it tries to set undef on everything.