[all-commits] [llvm/llvm-project] 240512: [LoongArch] Add a pass to rewrite rd to r0 for non...

[hev via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 240512c43234f58b3924cd90fe0781445d97e98d
      https://github.com/llvm/llvm-project/commit/240512c43234f58b3924cd90fe0781445d97e98d
  Author: hev <wangrui at loongson.cn>
  Date:   2024-06-07 (Fri, 07 Jun 2024)

  Changed paths:
    M llvm/lib/Target/LoongArch/CMakeLists.txt
    M llvm/lib/Target/LoongArch/LoongArch.h
    A llvm/lib/Target/LoongArch/LoongArchDeadRegisterDefinitions.cpp
    M llvm/lib/Target/LoongArch/LoongArchTargetMachine.cpp
    M llvm/test/CodeGen/LoongArch/global-address.ll
    M llvm/test/CodeGen/LoongArch/intrinsic-la64.ll
    M llvm/test/CodeGen/LoongArch/intrinsic.ll
    M llvm/test/CodeGen/LoongArch/ir-instruction/br.ll
    M llvm/test/CodeGen/LoongArch/ir-instruction/load-store.ll
    M llvm/test/CodeGen/LoongArch/psabi-restricted-scheduling.ll
    M llvm/utils/gn/secondary/llvm/lib/Target/LoongArch/BUILD.gn

  Log Message:
  -----------
  [LoongArch] Add a pass to rewrite rd to r0 for non-computational instrs whose return values are unused (#94590)

This patch adds a peephole pass `LoongArchDeadRegisterDefinitions`. It
rewrites `rd` to `r0` when `rd` is marked as dead. It may improve the
register allocation and reduce pipeline hazards on CPUs without register
renaming and OOO.



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