[all-commits] [llvm/llvm-project] 05a237: [RISCV][GlobalISel] Lower i8 bitreverse using brev...

[Bogdan Vetrenko via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 05a237293730ce2e83718037d7addabd6c15b238
      https://github.com/llvm/llvm-project/commit/05a237293730ce2e83718037d7addabd6c15b238
  Author: Bogdan Vetrenko <b.vetrenko at yandex.ru>
  Date:   2026-05-26 (Tue, 26 May 2026)

  Changed paths:
    M llvm/lib/Target/RISCV/GISel/RISCVLegalizerInfo.cpp
    M llvm/lib/Target/RISCV/GISel/RISCVLegalizerInfo.h
    M llvm/lib/Target/RISCV/RISCVISelLowering.cpp
    M llvm/lib/Target/RISCV/RISCVISelLowering.h
    M llvm/lib/Target/RISCV/RISCVInstrGISel.td
    A llvm/test/CodeGen/RISCV/GlobalISel/bitreverse-zbkb.ll

  Log Message:
  -----------
  [RISCV][GlobalISel] Lower i8 bitreverse using brev8 with Zbkb (#199469)

This teaches RISC-V GlobalISel to custom-lower scalar i8 G_BITREVERSE
using brev8 when Zbkb is available.

The i8 source is zero-extended to XLEN before applying the riscv_brev8
intrinsic. Since brev8 reverses bits independently within each byte, the
high zero bytes remain zero, so the result can be truncated back to i8.



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