[all-commits] [llvm/llvm-project] 63113c: [RISCV] Remove what appears to be an unnecessary c...

[Craig Topper via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 63113cfc985321432f266d801111117915ad1d72
      https://github.com/llvm/llvm-project/commit/63113cfc985321432f266d801111117915ad1d72
  Author: Craig Topper <craig.topper at sifive.com>
  Date:   2025-02-14 (Fri, 14 Feb 2025)

  Changed paths:
    M llvm/lib/Target/RISCV/RISCVISelLowering.cpp
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-shufflevector-vnsrl.ll

  Log Message:
  -----------
  [RISCV] Remove what appears to be an unnecessary check for LMUL_8 in getSingleShuffleSrc. (#127250)

I think this dates to a time when we used to use a type twice as large
as necessary for the input to the vnsrl. This was changed in #118509
when factor 4 and 8 were added.

The existing test for this regresses because it uses a lot of undef
elements and we previously figured out we could reduce its size and then
try the vnsrl again. We now match it before we try to reduce the width
so we miss this opportunity.

I've added a second test that doesn't have any undef elements in the
first half. Prior to this patch we used a vcompress lowering instead of
vnsrl.



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