[PATCH] libstdc++: Use __builtin_shufflevector for simd split and concat

[Jonathan Wakely]

On Tue, 7 May 2024 at 14:42, Matthias Kretz <m.kretz@gsi.de> wrote:
>
> Tested on x86_64-linux-gnu and aarch64-linux-gnu and with Clang 18 on x86_64-
> linux-gnu.
>
> OK for trunk and backport(s)?

OK for all.


>
> ---------------------- 8< ----------------------------
>
> Signed-off-by: Matthias Kretz <m.kretz@gsi.de>
>
> libstdc++-v3/ChangeLog:
>
>         PR libstdc++/114958
>         * include/experimental/bits/simd.h (__as_vector): Return scalar
>         simd as one-element vector. Return vector from single-vector
>         fixed_size simd.
>         (__vec_shuffle): New.
>         (__extract_part): Adjust return type signature.
>         (split): Use __extract_part for any split into non-fixed_size
>         simds.
>         (concat): If the return type stores a single vector, use
>         __vec_shuffle (which calls __builtin_shufflevector) to produce
>         the return value.
>         * include/experimental/bits/simd_builtin.h
>         (__shift_elements_right): Removed.
>         (__extract_part): Return single elements directly. Use
>         __vec_shuffle (which calls __builtin_shufflevector) to for all
>         non-trivial cases.
>         * include/experimental/bits/simd_fixed_size.h (__extract_part):
>         Return single elements directly.
>         * testsuite/experimental/simd/pr114958.cc: New test.
> ---
>  libstdc++-v3/include/experimental/bits/simd.h | 161 +++++++++++++-----
>  .../include/experimental/bits/simd_builtin.h  | 152 +----------------
>  .../experimental/bits/simd_fixed_size.h       |   4 +-
>  .../testsuite/experimental/simd/pr114958.cc   |  20 +++
>  4 files changed, 145 insertions(+), 192 deletions(-)
>  create mode 100644 libstdc++-v3/testsuite/experimental/simd/pr114958.cc
>
>
> --
> ──────────────────────────────────────────────────────────────────────────
>  Dr. Matthias Kretz                           https://mattkretz.github.io
>  GSI Helmholtz Centre for Heavy Ion Research               https://gsi.de
>  stdₓ::simd
> ──────────────────────────────────────────────────────────────────────────