[all-commits] [llvm/llvm-project] 6fdc77: [RISCV] Don't reduce vslidedown's VL in rotations

[Luke Lau via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 6fdc77e4884ba22453c0042ab6b11cf43499958d
      https://github.com/llvm/llvm-project/commit/6fdc77e4884ba22453c0042ab6b11cf43499958d
  Author: Luke Lau <luke at igalia.com>
  Date:   2023-05-25 (Thu, 25 May 2023)

  Changed paths:
    M llvm/lib/Target/RISCV/RISCVISelLowering.cpp
    M llvm/test/CodeGen/RISCV/rvv/fixed-vector-shuffle-reverse.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-fp-shuffles.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-int-shuffles.ll
    M llvm/test/CodeGen/RISCV/rvv/shuffle-reverse.ll

  Log Message:
  -----------
  [RISCV] Don't reduce vslidedown's VL in rotations

Even though we only need to write to the bottom NumElts - Rotation
elements for the vslidedown.vi, we can save an extra vsetivli toggle if
we just keep the wide VL.

(I may be missing something here: is there a reason why we want to explicitly keep the vslidedown narrow?)

Reviewed By: craig.topper

Differential Revision: https://reviews.llvm.org/D151390