[all-commits] [llvm/llvm-project] 49a4f3: [AArch64][GlobalISel] Add a post-legalizer combine...

[Jessica Paquette via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 49a4f3f7d88f61a81279de3d4e1c734ab0363228
      https://github.com/llvm/llvm-project/commit/49a4f3f7d88f61a81279de3d4e1c734ab0363228
  Author: Jessica Paquette <jpaquette at apple.com>
  Date:   2020-05-21 (Thu, 21 May 2020)

  Changed paths:
    M llvm/include/llvm/CodeGen/GlobalISel/CombinerHelper.h
    M llvm/include/llvm/Target/GlobalISel/Combine.td
    M llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
    M llvm/lib/Target/AArch64/AArch64.h
    M llvm/lib/Target/AArch64/AArch64Combine.td
    A llvm/lib/Target/AArch64/AArch64PostLegalizerCombiner.cpp
    M llvm/lib/Target/AArch64/AArch64PreLegalizerCombiner.cpp
    M llvm/lib/Target/AArch64/AArch64TargetMachine.cpp
    M llvm/lib/Target/AArch64/CMakeLists.txt
    M llvm/test/CodeGen/AArch64/GlobalISel/gisel-commandline-option.ll
    A llvm/test/CodeGen/AArch64/GlobalISel/postlegalizer-combiner-store-undef.mir

  Log Message:
  -----------
  [AArch64][GlobalISel] Add a post-legalizer combiner with a very simple combine.

(This patch is by Jessica, I'm just committing it on her behalf because I need
a post-legalizer combiner for something else).

This supersedes D77250, which did equivalent work in the selector. This can be
done pre-legalization or post-legalization. Post-legalization is more likely to
hit, since G_IMPLICIT_DEFs tend to appear during legalization. There's no reason
to not do it pre-legalization though-- if it can be caught earlier, great.

(I also think that it might be worth reimplementing D78769 using a
target-specific post-legalization combine too after thinking about it for a
while.)

Differential Revision: https://reviews.llvm.org/D78852