[all-commits] [llvm/llvm-project] 43d923: [RISCV][P-Ext] Prefer pack/ppairo.h over pncvt.h/p...

[Craig Topper via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 43d9238a7f79d0a6714b9ffa4af97484fed8429e
      https://github.com/llvm/llvm-project/commit/43d9238a7f79d0a6714b9ffa4af97484fed8429e
  Author: Craig Topper <craig.topper at sifive.com>
  Date:   2026-09-29 (Tue, 29 Sep 2026)

  Changed paths:
    M cross-project-tests/intrinsic-header-tests/riscv_packed_simd.c
    M llvm/lib/Target/RISCV/RISCVISelLowering.cpp
    M llvm/test/CodeGen/RISCV/rvp-simd-32.ll
    M llvm/test/CodeGen/RISCV/rvp-zip.ll

  Log Message:
  -----------
  [RISCV][P-Ext] Prefer pack/ppairo.h over pncvt.h/pncvth.h in shuffle lowering (#227105)

These have equivalent behavior, but pncvt.h/pncvth.h requires the input
to be a register pair. Shuffle lowering doesn't know if the sources came
from the same 64-bit value so using pncvt.h/pncvth.h may overconstrain
register allocation and require copies.

If some hardware has better performance for pncvt.h/pncvth.h we
can consider ways to intelligently pick the two alternatives. For
now just pick pack/ppairo.h.



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