[all-commits] [llvm/llvm-project] 0748f4: [AArch64][GlobalISel] Legalize 128-bit types for F...

[Him188 via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 0748f4227cd6a4a32b155d4bb9ad3f07e1b54bfe
      https://github.com/llvm/llvm-project/commit/0748f4227cd6a4a32b155d4bb9ad3f07e1b54bfe
  Author: Him188 <tguan at nvidia.com>
  Date:   2024-09-03 (Tue, 03 Sep 2024)

  Changed paths:
    M llvm/include/llvm/CodeGen/GlobalISel/LegalizerHelper.h
    M llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
    M llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.cpp
    M llvm/test/CodeGen/AArch64/GlobalISel/legalizer-info-validation.mir
    A llvm/test/CodeGen/AArch64/fabs-fp128.ll

  Log Message:
  -----------
  [AArch64][GlobalISel] Legalize 128-bit types for FABS (#104753)

This patch adds a common lower action for `G_FABS`, which generates `and
x8, x8, #0x7fffffffffffffff` to reset the sign bit. The action does not
support vectors since `G_AND` does not support fp128.


This approach is different than what SDAG is doing. SDAG stores the
value onto stack, clears the sign bit in the most significant byte, and
loads the value back into register. This involves multiple memory ops
and sounds slower.



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