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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>
63 lines
1.8 KiB
C++
63 lines
1.8 KiB
C++
// { dg-do compile { target c++26 } }
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// { dg-require-effective-target x86 }
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#include <simd>
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#include <stdfloat>
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namespace simd = std::simd;
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// vec.math ///////////////////////////////////////
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namespace math_tests
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{
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using simd::__deduced_vec_t;
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using simd::__math_floating_point;
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using std::is_same_v;
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using vf2 = simd::vec<float, 2>;
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using vf4 = simd::vec<float, 4>;
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template <typename T0, typename T1>
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concept has_common_type = requires { typename std::common_type<T0, T1>::type; };
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template <typename T>
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concept has_deduced_vec = requires { typename simd::__deduced_vec_t<T>; };
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static_assert(!has_common_type<vf2, vf4>);
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static_assert( has_common_type<int, vf2>);
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template <typename T, bool Strict = false>
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struct holder
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{
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T value;
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constexpr
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operator const T&() const
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{ return value; }
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template <typename U>
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requires (!std::same_as<T, U>) && Strict
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operator U() const = delete;
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};
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// The next always has a common_type because the UDT is convertible_to<float> and is not an
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// arithmetic type:
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static_assert( has_common_type<holder<int>, vf2>);
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// It's up to the UDT to constrain itself better:
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static_assert(!has_common_type<holder<int, true>, vf2>);
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// However, a strict UDT can still work
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static_assert( has_common_type<holder<float, true>, vf2>);
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// Except if it needs any kind of conversion, even if it's value-preserving. Again the semantics
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// are what the UDT defined.
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static_assert(!has_common_type<holder<short, true>, vf2>);
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static_assert(!has_deduced_vec<int>);
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static_assert(!__math_floating_point<int>);
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static_assert(!__math_floating_point<float>);
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static_assert(!__math_floating_point<simd::vec<int>>);
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static_assert( __math_floating_point<simd::vec<float>>);
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}
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