[all-commits] [llvm/llvm-project] c59f9e: [MCP] Optimize copies from undef

[Pierre van Houtryve via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: c59f9eada1abe369c0470aa2dad8b20ac5269020
      https://github.com/llvm/llvm-project/commit/c59f9eada1abe369c0470aa2dad8b20ac5269020
  Author: pvanhout <pierre.vanhoutryve at amd.com>
  Date:   2023-06-29 (Thu, 29 Jun 2023)

  Changed paths:
    M llvm/lib/CodeGen/MachineCopyPropagation.cpp
    M llvm/test/CodeGen/X86/machine-copy-prop.mir

  Log Message:
  -----------
  [MCP] Optimize copies from undef

Revert D152502 and instead optimize away copy from undefs, but clear the undef flag on the original copy.
Apparently, not optimizing the COPY can cause performance issues in some cases.

Fixes SWDEV-405813, SWDEV-405899

Reviewed By: arsenm

Differential Revision: https://reviews.llvm.org/D153838