Re: [PATCH 1/2] Add std::experimental::simd from the Parallelism TS 2

[Jonathan Wakely <jwakely@redhat.com>]

On 18/12/20 16:49 +0100, Matthias Kretz wrote:
>Resending this patch with proper commit message and rebased on master.
>
>From: Matthias Kretz <kretz@kde.org>
>
>Adds <experimental/simd>.
>
>This implements the simd and simd_mask class templates via
>[[gnu::vector_size(N)]] data members. It implements overloads for all of
><cmath> for simd. Explicit vectorization of the <cmath> functions is not
>finished.
>The majority of functions are marked as [[gnu::always_inline]] to enable
>quasi-ODR-conforming linking of TUs with different -m flags.
>Performance optimization was done for x86_64. ARM, Aarch64, and POWER
>rely on the compiler to recognize reduction, conversion, and shuffle
>patterns.
>Besides verification using many different machine flages, the code was
>also verified with different fast-math flags.
>
>libstdc++-v3/ChangeLog:
>	* doc/xml/manual/status_cxx2017.xml: Add implementation status
>	of the Parallelism TS 2. Document implementation-defined types
>	and behavior.
>	* include/Makefile.am: Add new headers.
>	* include/Makefile.in: Regenerate.
>	* include/experimental/simd: New file. New header for
>	Parallelism TS 2.
>	* include/experimental/bits/numeric_traits.h: New file.
>	Implementation of P1841R1 using internal naming. Addition of
>	missing IEC559 functionality query.
>	* include/experimental/bits/simd.h: New file. Definition of the
>	public simd interfaces and general implementation helpers.
>	* include/experimental/bits/simd_builtin.h: New file.
>	Implementation of the _VecBuiltin simd_abi.
>	* include/experimental/bits/simd_converter.h: New file. Generic
>	simd conversions.
>	* include/experimental/bits/simd_detail.h: New file. Internal
>	macros for the simd implementation.
>	* include/experimental/bits/simd_fixed_size.h: New file. Simd
>	fixed_size ABI specific implementations.
>	* include/experimental/bits/simd_math.h: New file. Math
>	overloads for simd.
>	* include/experimental/bits/simd_neon.h: New file. Simd NEON
>	specific implementations.
>	* include/experimental/bits/simd_ppc.h: New file. Implement bit
>	shifts to avoid invalid results for integral types smaller than
>	int.
>	* include/experimental/bits/simd_scalar.h: New file. Simd scalar
>	ABI specific implementations.
>	* include/experimental/bits/simd_x86.h: New file. Simd x86
>	specific implementations.
>	* include/experimental/bits/simd_x86_conversions.h: New file.
>	x86 specific conversion optimizations. The conversion patterns
>	work around missing conversion patterns in the compiler and
>	should be removed as soon as PR85048 is resolved.
>	* testsuite/experimental/simd/standard_abi_usable.cc: New file.
>	Test that all (not all fixed_size<N>, though) standard simd and
>	simd_mask types are usable.
>	* testsuite/experimental/simd/standard_abi_usable_2.cc: New
>	file. As above but with -ffast-math.
>	* testsuite/libstdc++-dg/conformance.exp: Don't build simd tests
>	from the standard test loop. Instead use
>	check_vect_support_and_set_flags to build simd tests with the
>	relevant machine flags.
>---
> .../doc/xml/manual/status_cxx2017.xml         |  216 +
> libstdc++-v3/include/Makefile.am              |   13 +
> libstdc++-v3/include/Makefile.in              |   13 +
> .../experimental/bits/numeric_traits.h        |  567 ++
> libstdc++-v3/include/experimental/bits/simd.h | 5051 ++++++++++++++++
> .../include/experimental/bits/simd_builtin.h  | 2949 ++++++++++
> .../experimental/bits/simd_converter.h        |  354 ++
> .../include/experimental/bits/simd_detail.h   |  306 +
> .../experimental/bits/simd_fixed_size.h       | 2066 +++++++
> .../include/experimental/bits/simd_math.h     | 1500 +++++
> .../include/experimental/bits/simd_neon.h     |  519 ++
> .../include/experimental/bits/simd_ppc.h      |  123 +
> .../include/experimental/bits/simd_scalar.h   |  772 +++
> .../include/experimental/bits/simd_x86.h      | 5169 +++++++++++++++++
> .../experimental/bits/simd_x86_conversions.h  | 2029 +++++++
> libstdc++-v3/include/experimental/simd        |   70 +
> .../experimental/simd/standard_abi_usable.cc  |   64 +
> .../simd/standard_abi_usable_2.cc             |    4 +
> .../testsuite/libstdc++-dg/conformance.exp    |   18 +-
> 19 files changed, 21802 insertions(+), 1 deletion(-)
> create mode 100644 libstdc++-v3/include/experimental/bits/numeric_traits.h
> create mode 100644 libstdc++-v3/include/experimental/bits/simd.h
> create mode 100644 libstdc++-v3/include/experimental/bits/simd_builtin.h
> create mode 100644 libstdc++-v3/include/experimental/bits/simd_converter.h
> create mode 100644 libstdc++-v3/include/experimental/bits/simd_detail.h
> create mode 100644 libstdc++-v3/include/experimental/bits/simd_fixed_size.h
> create mode 100644 libstdc++-v3/include/experimental/bits/simd_math.h
> create mode 100644 libstdc++-v3/include/experimental/bits/simd_neon.h
> create mode 100644 libstdc++-v3/include/experimental/bits/simd_ppc.h
> create mode 100644 libstdc++-v3/include/experimental/bits/simd_scalar.h
> create mode 100644 libstdc++-v3/include/experimental/bits/simd_x86.h
> create mode 100644 libstdc++-v3/include/experimental/bits/
>simd_x86_conversions.h
> create mode 100644 libstdc++-v3/include/experimental/simd
> create mode 100644 libstdc++-v3/testsuite/experimental/simd/
>standard_abi_usable.cc
> create mode 100644 libstdc++-v3/testsuite/experimental/simd/
>standard_abi_usable_2.cc


I have pushed this to master, after a week of testing on x86_64 and
powerpc64 and powerpc64le.

I know it's stage 4 now, but this only adds a new experimental
implementation of a TS, it doesn't touch any existing code. The new
tests (which were in a separate patch) are all skipped by default, so
shouldn't cause any new failures for testers.