[all-commits] [llvm/llvm-project] 0111da: [GlobalISel] Add re-association combine for G_PTR_...

[Amara Emerson via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 0111da2ef80adc516f13d7c7f4125eb9eea6c08f
      https://github.com/llvm/llvm-project/commit/0111da2ef80adc516f13d7c7f4125eb9eea6c08f
  Author: Amara Emerson <amara at apple.com>
  Date:   2021-07-02 (Fri, 02 Jul 2021)

  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
    A llvm/test/CodeGen/AArch64/GlobalISel/combine-ptradd-reassociation.mir

  Log Message:
  -----------
  [GlobalISel] Add re-association combine for G_PTR_ADD to allow better addressing mode usage.

We're trying to match a few pointer computation patterns here for
re-association opportunities.
1) Isolating a constant operand to be on the RHS, e.g.:
   G_PTR_ADD(BASE, G_ADD(X, C)) -> G_PTR_ADD(G_PTR_ADD(BASE, X), C)

2) Folding two constants in each sub-tree as long as such folding
   doesn't break a legal addressing mode.
   G_PTR_ADD(G_PTR_ADD(BASE, C1), C2) -> G_PTR_ADD(BASE, C1+C2)

AArch64 code size improvements on CTMark with -Os:
Program              before  after   diff
 pairlocalalign      251048  251044 -0.0%
 consumer-typeset    421820  421812 -0.0%
 kc                  431348  431320 -0.0%
 SPASS               413404  413300 -0.0%
 clamscan            384396  384220 -0.0%
 tramp3d-v4          370640  370412 -0.1%
 lencod              432096  431772 -0.1%
 bullet              479400  478796 -0.1%
 sqlite3             288504  288072 -0.1%
 7zip-benchmark      573796  570768 -0.5%
 Geomean difference                 -0.1%

Differential Revision: https://reviews.llvm.org/D105069