[all-commits] [llvm/llvm-project] dc72ec: [RISCV] Custom legalize vp.merge for mask vectors....

[Craig Topper via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: dc72ec808d97a83fe9d3c1889302067cbee24c91
      https://github.com/llvm/llvm-project/commit/dc72ec808d97a83fe9d3c1889302067cbee24c91
  Author: Craig Topper <craig.topper at sifive.com>
  Date:   2024-12-18 (Wed, 18 Dec 2024)

  Changed paths:
    M llvm/lib/Target/RISCV/RISCVISelLowering.cpp
    M llvm/lib/Target/RISCV/RISCVISelLowering.h
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-vpmerge.ll
    M llvm/test/CodeGen/RISCV/rvv/vpmerge-sdnode.ll

  Log Message:
  -----------
  [RISCV] Custom legalize vp.merge for mask vectors. (#120479)

The default legalization uses vmslt with a vector of XLen to compute a
mask. This doesn't work if the type isn't legal. For fixed vectors it
will scalarize. For scalable vectors it crashes the compiler.

This patch uses an alternate strategy that promotes the i1 vector to an
i8 vector and does the merge. I don't claim this to be the best
lowering. I wrote it quickly almost 3 years ago when a crash was
reported in our downstream.

Fixes #120405.



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