[all-commits] [llvm/llvm-project] 2906fc: [GlobalISel] Combine G_MERGE_VALUES of x and zero ...

[Thorsten Schütt via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 2906fcadb8563a02949f852867cebc63e0539cb7
      https://github.com/llvm/llvm-project/commit/2906fcadb8563a02949f852867cebc63e0539cb7
  Author: Thorsten Schütt <schuett at gmail.com>
  Date:   2024-11-16 (Sat, 16 Nov 2024)

  Changed paths:
    M llvm/include/llvm/CodeGen/GlobalISel/CombinerHelper.h
    M llvm/include/llvm/Target/GlobalISel/Combine.td
    M llvm/lib/CodeGen/GlobalISel/CombinerHelperArtifacts.cpp
    M llvm/test/CodeGen/AArch64/GlobalISel/combine-unmerge.mir
    M llvm/test/CodeGen/AMDGPU/GlobalISel/atomic_optimizations_mul_one.ll
    M llvm/test/CodeGen/AMDGPU/GlobalISel/combine-lshr-narrow.mir
    M llvm/test/CodeGen/AMDGPU/GlobalISel/fp64-atomics-gfx90a.ll
    M llvm/test/CodeGen/AMDGPU/GlobalISel/global-atomic-fadd.f32-no-rtn.ll
    M llvm/test/CodeGen/AMDGPU/GlobalISel/global-atomic-fadd.f32-rtn.ll
    M llvm/test/CodeGen/AMDGPU/GlobalISel/sdiv.i64.ll
    M llvm/test/CodeGen/AMDGPU/GlobalISel/srem.i64.ll
    M llvm/test/CodeGen/AMDGPU/div_i128.ll

  Log Message:
  -----------
  [GlobalISel] Combine G_MERGE_VALUES of x and zero (#116283)

into zext x

LegalizerHelper has two padding strategies: undef or zero.

see LegalizerHelper:273
see LegalizerHelper:315

This PR is about zero sugar and Coke Zero.

; CHECK-NEXT: [[MV2:%[0-9]+]]:_(s64) = G_MERGE_VALUES %a(s32),
[[C]](s32)

Please continue padding merge values.

// %bits_8_15:(s8) = G_CONSTANT i8 0
// %0:(s16) = G_MERGE_VALUES %bits_0_7:(s8), %bits_8_15:(s8)

%bits_8_15 is defined by zero. For optimization, we pick zext.

// %0:_(s16) = G_ZEXT %bits_0_7:(s8)

The upper bits of %0 are zero and the lower bits come from %bits_0_7.



To unsubscribe from these emails, change your notification settings at https://github.com/llvm/llvm-project/settings/notifications