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This implementation differs significantly from the
std::experimental::simd implementation. One goal was a reduction in
template instantiations wrt. what std::experimental::simd did.
Design notes:
- bits/vec_ops.h contains concepts, traits, and functions for working
with GNU vector builtins that are mostly independent from std::simd.
These could move from std::simd:: to std::__vec (or similar). However,
we would then need to revisit naming. For now we kept everything in
the std::simd namespace with __vec_ prefix in the names. The __vec_*
functions can be called unqualified because they can never be called
on user-defined types (no ADL). If we ever get simd<UDT> support this
will be implemented via bit_cast to/from integral vector
builtins/intrinsics.
- bits/simd_x86.h extends vec_ops.h with calls to __builtin_ia32_* that
can only be used after uttering the right GCC target pragma.
- basic_vec and basic_mask are built on top of register-size GNU vector
builtins (for now / x86). Any larger vec/mask is a tree of power-of-2
#elements on the "first" branch. Anything non-power-of-2 that is
smaller than register size uses padding elements that participate in
element-wise operations. The library ensures that padding elements
lead to no side effects. The implementation makes no assumption on the
values of these padding elements since the user can bit_cast to
basic_vec/basic_mask.
Implementation status:
- The implementation is prepared for more than x86 but is x86-only for
now.
- Parts of [simd] *not* implemented in this patch:
- std::complex<floating-point> as vectorizable types
- [simd.permute.dynamic]
- [simd.permute.mask]
- [simd.permute.memory]
- [simd.bit]
- [simd.math]
- mixed operations with vec-mask and bit-mask types
- some conversion optimizations (open questions wrt. missed
optimizations in the compiler)
- This patch implements P3844R3 "Restore simd::vec broadcast from int",
which is not part of the C++26 WD draft yet. If the paper does not get
accepted the feature will be reverted.
- This patch implements D4042R0 "incorrect cast between simd::vec and
simd::mask via conversion to and from impl-defined vector types" (to be
published once the reported LWG issue gets a number).
- The standard feature test macro __cpp_lib_simd is not defined yet.
Tests:
- Full coverage requires testing
1. constexpr,
2. constant-propagating inputs, and
3. unknown (to the optimizer) inputs
- for all vectorizable types
* for every supported width (1–64 and higher)
+ for all possible ISA extensions (combinations)
= with different fast-math flags
... leading to a test matrix that's far out of reach for regular
testsuite builds.
- The tests in testsuite/std/simd/ try to cover all of the API. The
tests can be build in every combination listed above. Per default only
a small subset is built and tested.
- Use GCC_TEST_RUN_EXPENSIVE=something to compile the more expensive
tests (constexpr and const-prop testing) and to enable more /
different widths for the test type.
- Tests can still emit bogus -Wpsabi warnings (see PR98734) which are
filtered out via dg-prune-output.
Benchmarks:
- The current implementation has been benchmarked in some aspects on
x86_64 hardware. There is more optimization potential. However, it is
not always clear whether optimizations should be part of the library
if they can be implemented in the compiler.
- No benchmark code is included in this patch.
libstdc++-v3/ChangeLog:
* include/Makefile.am: Add simd headers.
* include/Makefile.in: Regenerate.
* include/bits/version.def (simd): New.
* include/bits/version.h: Regenerate.
* include/bits/simd_alg.h: New file.
* include/bits/simd_details.h: New file.
* include/bits/simd_flags.h: New file.
* include/bits/simd_iterator.h: New file.
* include/bits/simd_loadstore.h: New file.
* include/bits/simd_mask.h: New file.
* include/bits/simd_mask_reductions.h: New file.
* include/bits/simd_reductions.h: New file.
* include/bits/simd_vec.h: New file.
* include/bits/simd_x86.h: New file.
* include/bits/vec_ops.h: New file.
* include/std/simd: New file.
* testsuite/std/simd/arithmetic.cc: New test.
* testsuite/std/simd/arithmetic_expensive.cc: New test.
* testsuite/std/simd/create_tests.h: New file.
* testsuite/std/simd/creation.cc: New test.
* testsuite/std/simd/creation_expensive.cc: New test.
* testsuite/std/simd/loads.cc: New test.
* testsuite/std/simd/loads_expensive.cc: New test.
* testsuite/std/simd/mask2.cc: New test.
* testsuite/std/simd/mask2_expensive.cc: New test.
* testsuite/std/simd/mask.cc: New test.
* testsuite/std/simd/mask_expensive.cc: New test.
* testsuite/std/simd/reductions.cc: New test.
* testsuite/std/simd/reductions_expensive.cc: New test.
* testsuite/std/simd/shift_left.cc: New test.
* testsuite/std/simd/shift_left_expensive.cc: New test.
* testsuite/std/simd/shift_right.cc: New test.
* testsuite/std/simd/shift_right_expensive.cc: New test.
* testsuite/std/simd/simd_alg.cc: New test.
* testsuite/std/simd/simd_alg_expensive.cc: New test.
* testsuite/std/simd/sse_intrin.cc: New test.
* testsuite/std/simd/stores.cc: New test.
* testsuite/std/simd/stores_expensive.cc: New test.
* testsuite/std/simd/test_setup.h: New file.
* testsuite/std/simd/traits_common.cc: New test.
* testsuite/std/simd/traits_impl.cc: New test.
* testsuite/std/simd/traits_math.cc: New test.
Signed-off-by: Matthias Kretz <m.kretz@gsi.de>
99 lines
3.3 KiB
C++
99 lines
3.3 KiB
C++
// Implementation of <simd> -*- C++ -*-
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// Copyright The GNU Toolchain Authors.
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//
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// This file is part of the GNU ISO C++ Library. This library is free
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// software; you can redistribute it and/or modify it under the
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// terms of the GNU General Public License as published by the
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// Free Software Foundation; either version 3, or (at your option)
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// any later version.
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// Under Section 7 of GPL version 3, you are granted additional
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// permissions described in the GCC Runtime Library Exception, version
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// 3.1, as published by the Free Software Foundation.
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// You should have received a copy of the GNU General Public License and
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// a copy of the GCC Runtime Library Exception along with this program;
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// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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// <http://www.gnu.org/licenses/>.
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#ifndef _GLIBCXX_SIMD_ALG_H
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#define _GLIBCXX_SIMD_ALG_H 1
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#ifdef _GLIBCXX_SYSHDR
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#pragma GCC system_header
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#endif
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#if __cplusplus >= 202400L
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#include "simd_vec.h"
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// psabi warnings are bogus because the ABI of the internal types never leaks into user code
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#pragma GCC diagnostic push
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#pragma GCC diagnostic ignored "-Wpsabi"
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// [simd.alg] -----------------------------------------------------------------
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namespace std _GLIBCXX_VISIBILITY(default)
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{
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_GLIBCXX_BEGIN_NAMESPACE_VERSION
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namespace simd
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{
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template<typename _Tp, typename _Ap>
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[[__gnu__::__always_inline__]]
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constexpr basic_vec<_Tp, _Ap>
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min(const basic_vec<_Tp, _Ap>& __a, const basic_vec<_Tp, _Ap>& __b) noexcept
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{ return __select_impl(__a < __b, __a, __b); }
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template<typename _Tp, typename _Ap>
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[[__gnu__::__always_inline__]]
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constexpr basic_vec<_Tp, _Ap>
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max(const basic_vec<_Tp, _Ap>& __a, const basic_vec<_Tp, _Ap>& __b) noexcept
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{ return __select_impl(__a < __b, __b, __a); }
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template<typename _Tp, typename _Ap>
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[[__gnu__::__always_inline__]]
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constexpr pair<basic_vec<_Tp, _Ap>, basic_vec<_Tp, _Ap>>
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minmax(const basic_vec<_Tp, _Ap>& __a, const basic_vec<_Tp, _Ap>& __b) noexcept
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{ return {min(__a, __b), max(__a, __b)}; }
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template<typename _Tp, typename _Ap>
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[[__gnu__::__always_inline__]]
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constexpr basic_vec<_Tp, _Ap>
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clamp(const basic_vec<_Tp, _Ap>& __v, const basic_vec<_Tp, _Ap>& __lo,
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const basic_vec<_Tp, _Ap>& __hi)
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{
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__glibcxx_simd_precondition(none_of(__lo > __hi), "lower bound is larger than upper bound");
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return max(__lo, min(__hi, __v));
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}
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template<typename _Tp, typename _Up>
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constexpr auto
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select(bool __c, const _Tp& __a, const _Up& __b)
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-> remove_cvref_t<decltype(__c ? __a : __b)>
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{ return __c ? __a : __b; }
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template<size_t _Bytes, typename _Ap, typename _Tp, typename _Up>
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[[__gnu__::__always_inline__]]
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constexpr auto
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select(const basic_mask<_Bytes, _Ap>& __c, const _Tp& __a, const _Up& __b)
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noexcept -> decltype(__select_impl(__c, __a, __b))
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{ return __select_impl(__c, __a, __b); }
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} // namespace simd
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using simd::min;
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using simd::max;
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using simd::minmax;
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using simd::clamp;
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_GLIBCXX_END_NAMESPACE_VERSION
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} // namespace std
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#pragma GCC diagnostic pop
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#endif // C++26
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#endif // _GLIBCXX_SIMD_ALG_H
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