[libcxx] <experimental/simd> Added simd width functions, simd_size traits and related tests

[Mordante]

Thanks for working on this. Can you add the paper number in the commit message?

[philnik]

Could you rebase this?

[Joy12138]

Rebase

[Joy12138]

Fix CMakeLists order

[Joy12138]

Fix clang tidy

[Joy12138]

Update status paper

[Joy12138]

@philnik ready for review

[philnik]

The implementation itself looks good, but the tests need some work.

libcxx/docs/Status/ParallelismProjects.csv

11

This looks wrong. Should there have been two lines?

17

I'm a bit confused by this entry and the one below. What exactly are you trying to mark as completed?

libcxx/include/experimental/__simd/traits.h

55

This needs a SFINAE test. I'm also not sure this works on the _v version.

libcxx/include/experimental/__simd/utility.h

10–11

utility doesn't really seem like that nice of a name for a header. Do you have plans to add more functions? If yes, which ones?

13–16

Please includes the granularized headers instead.

23–24

Why isn't this simply a variable template?

libcxx/test/std/experimental/simd/simd.class/simd_width.pass.cpp

24–25

This way we make sure the functions is static and constexpr.

32

Why aren't you calling CheckSimdWidth directly?

libcxx/test/std/experimental/simd/simd.traits/simd_size.pass.cpp

63

The 16 here and _LIBCPP_NATIVE_SIMD_WIDTH_IN_BYTES are implementation-defined, so this should either be moved into a new test in test/libcxx or be a LIBCPP_STATIC_ASSERT.

86–121

This looks like a really complicated way to do this. For scalar, compatible and native it doesn't look like you make any use of the instantiation facility. They could instead just be in the main().

[Joy12138]

libcxx/docs/Status/ParallelismProjects.csv

11

This looks wrong. Should there have been two lines?

This line corresponds to traits simd_size and simd_size_v.

And traits is_abi_tag_v is the dependency because the implementation of simd_size_v used it for SFINAE check. Am I right?

17

I'm a bit confused by this entry and the one below. What exactly are you trying to mark as completed?

This line and the one below correspond to the function size() in class simd and class simd_mask. And the function size() in class simd is dependent on traits simd_size_v. The function size() in class simd_mask is dependent on the function size() in class simd.

libcxx/include/experimental/__simd/utility.h

10–11

Yes, this file is mainly used to implement some internal functions that are not easy to classify. You can see them here: https://reviews.llvm.org/D139421#change-93rWXSd8B8Z9

[Joy12138]

libcxx/include/experimental/__simd/utility.h

23–24

This is mainly used to give a flag for SFINAE check. I think it's better to use it as a function. WDYT?

[Joy12138]

Fix some comments

[Joy12138]

Fix simd_size test

[philnik]

This looks pretty good now. I have a few comments, but nothing major.

libcxx/docs/Status/ParallelismProjects.csv

11

Ahh, I missed that is_abi_tag is a dependency. Never mind then.

17

Ok. I think it would be clearer to use simd<>::size() and simd_mask<>::size()instead.

libcxx/include/experimental/__simd/simd.h

27

These aliases need tests too. Just check for a few instantiations that they exist and have the expected types.

libcxx/include/experimental/__simd/utility.h

10–11

Hmm, I can't come up with a good name for them right now. No action required right now.

23–24

Since this is a type trait, a variable template is the more canonical way to write it. It also avoids evaluating the same trait multiple times.

libcxx/test/libcxx/transitive_includes/cxx03.csv

265 ↗

(On Diff #535725)

These shouldn't be required anymore.

[Joy12138]

Fix CI

[Joy12138]

Fix status paper and variable template

[Joy12138]

Add SFINAE test and alias test

[Joy12138]

Add mask alias test

[Joy12138]

Add newline at end of file

[Joy12138]

@philnik Hi, we have added the SFINAE false test for simd_size. But the error messages seem not easy to read. Do you have any suggestions?

[philnik]

In D144363#4488881, @Joy12138 wrote:

@philnik Hi, we have added the SFINAE false test for simd_size. But the error messages seem not easy to read. Do you have any suggestions?

I think you did something wrong. You shouldn't need a .verify.cpp for SFINAE testing, and looking at the error message the types don't SFINAE away.

Something like

template <class T, class U, class = void>
struct check_sfinae : false_type {};

template <class T, class U>
struct check_sfinae<void_t<ex::simd_size<T, U>>> : true_type {};

static_assert(!check_sfinae<int , ex::native_simd<int>>::value);

should work just fine in a normal .pass.cpp. If you get an error, either I did something wrong in the SFINAE test, or the implementation of ex::simd_size is wrong (because it doesn't SFINAE away).

I'm pretty sure that variable templates can't SFINAE away.

[Joy12138]

Rewrite SFINAE tests

[Joy12138]

In D144363#4491370, @philnik wrote:

I think you did something wrong. You shouldn't need a .verify.cpp for SFINAE testing, and looking at the error message the types don't SFINAE away.

Something like

template <class T, class U, class = void>
struct check_sfinae : false_type {};

template <class T, class U>
struct check_sfinae<void_t<ex::simd_size<T, U>>> : true_type {};

static_assert(!check_sfinae<int , ex::native_simd<int>>::value);

should work just fine in a normal .pass.cpp. If you get an error, either I did something wrong in the SFINAE test, or the implementation of ex::simd_size is wrong (because it doesn't SFINAE away).

I'm pretty sure that variable templates can't SFINAE away.

@philnik Hi, we rewrite the SFINAE test as you given style. It seems no errors come out. Does it mean our implementations right?

[philnik]

In D144363#4496024, @Joy12138 wrote:

In D144363#4491370, @philnik wrote:

I think you did something wrong. You shouldn't need a .verify.cpp for SFINAE testing, and looking at the error message the types don't SFINAE away.

Something like

template <class T, class U, class = void>
struct check_sfinae : false_type {};

template <class T, class U>
struct check_sfinae<void_t<ex::simd_size<T, U>>> : true_type {};

static_assert(!check_sfinae<int , ex::native_simd<int>>::value);

should work just fine in a normal .pass.cpp. If you get an error, either I did something wrong in the SFINAE test, or the implementation of ex::simd_size is wrong (because it doesn't SFINAE away).

I'm pretty sure that variable templates can't SFINAE away.

@philnik Hi, we rewrite the SFINAE test as you given style. It seems no errors come out. Does it mean our implementations right?

Looks correct to me. TIL that variable templates can SFINAE away. I think we are missing some test coverage elsewhere...

LGTM % comment. Thanks! I'm really looking forward to having a great <experimental/simd> implementation.

libcxx/test/std/experimental/simd/simd.traits/simd_size.pass.cpp

59–63

Please also add tests for simd_size, and not just for simd_size_v.

[Joy12138]

Errors come out with SFINAE tests for simd_size. Same tests pass with simd_size_v.

You can see the situation in following URL and try the other parameters:

https://godbolt.org/z/EjWxz6P37

Do you have any solutions?

[Joy12138]

Add SFINAE test for simd_size

[Joy12138]

In D144363#4496566, @Joy12138 wrote:

Errors come out with SFINAE tests for simd_size. Same tests pass with simd_size_v.

You can see the situation in following URL and try the other parameters:

https://godbolt.org/z/EjWxz6P37

Do you have any solutions?

We add enable_if_t to simd_size implementation, too. It seems fixed.

[Joy12138]

Rebase

[philnik]

libcxx/include/experimental/__simd/traits.h

61

As discussed in D153319#inline-1502156, this needs to be updated.

[Joy12138]

Fix simd_size

[Joy12138]

[Joy12138]

@philnik Hi! We found that the current implementation might have an unexpected behavior. Because we do not check the template parameter of simd_size_v, it gives value with invalid first parameter.

https://godbolt.org/z/o8o4fWe7n

In the document, simd_size is implemented first and using simd_size_v as value of simd_size. Therefore, the template parameters of simd_size_v are checked by simd_size. Here is the behavior with GCC implementation: https://godbolt.org/z/1vYTsnbsd

I implement in the current form because you told me earlier that implementing variable first can avoid instantiating a class every time. But it seems to have some minor issues at the moment.

By the way, memory_alignment_v will also have the same issue. Do you have any suggestions for solving this?

[philnik]

In D144363#4504748, @Joy12138 wrote:

@philnik Hi! We found that the current implementation might have an unexpected behavior. Because we do not check the template parameter of simd_size_v, it gives value with invalid first parameter.

https://godbolt.org/z/o8o4fWe7n

In the document, simd_size is implemented first and using simd_size_v as value of simd_size. Therefore, the template parameters of simd_size_v are checked by simd_size. Here is the behavior with GCC implementation: https://godbolt.org/z/1vYTsnbsd

I implement in the current form because you told me earlier that implementing variable first can avoid instantiating a class every time. But it seems to have some minor issues at the moment.

By the way, memory_alignment_v will also have the same issue. Do you have any suggestions for solving this?

Good catch! I'm actually learning some really interesting things about template variables and how they interact with things. I think the easiest solution for now is to use the class to implement the _v version. It's probably not worth the effort to try to avoid the instantiation. That's more of a nice to have than an absolute need to have. Please also add a test for this. Something like

simd_size_v.verify.cpp

static_assert(!std::experimental::simd_size_v<...>); // expected-error {{no member named 'value'}}

should be good enough.

[Joy12138]

Fix simd_size_v

[Joy12138]

Add newline at end of file

[Joy12138]

In D144363#4504760, @philnik wrote:

In D144363#4504748, @Joy12138 wrote:

@philnik Hi! We found that the current implementation might have an unexpected behavior. Because we do not check the template parameter of simd_size_v, it gives value with invalid first parameter.

https://godbolt.org/z/o8o4fWe7n

In the document, simd_size is implemented first and using simd_size_v as value of simd_size. Therefore, the template parameters of simd_size_v are checked by simd_size. Here is the behavior with GCC implementation: https://godbolt.org/z/1vYTsnbsd

I implement in the current form because you told me earlier that implementing variable first can avoid instantiating a class every time. But it seems to have some minor issues at the moment.

By the way, memory_alignment_v will also have the same issue. Do you have any suggestions for solving this?

Good catch! I'm actually learning some really interesting things about template variables and how they interact with things. I think the easiest solution for now is to use the class to implement the _v version. It's probably not worth the effort to try to avoid the instantiation. That's more of a nice to have than an absolute need to have. Please also add a test for this. Something like

simd_size_v.verify.cpp

static_assert(!std::experimental::simd_size_v<...>); // expected-error {{no member named 'value'}}

should be good enough.

It seems CI not happy with

simd_size_v.verify.cpp

static_assert(!std::experimental::simd_size_v<...>); // expected-error {{no member named 'value'}}

Can I use

simd_size_v.verify.cpp

std::experimental::simd_size_v<...>; // expected-error {{no member named 'value'}}

instead? Or do you have any solutions?

[philnik]

In D144363#4508676, @Joy12138 wrote:

Can I use

simd_size_v.verify.cpp

std::experimental::simd_size_v<...>; // expected-error {{no member named 'value'}}

instead? Or do you have any solutions?

Yeah, of course. Not sure why I bothered putting it in a static_assert.

[Joy12138]

Fix CI

[Joy12138]

Fix CI

[Joy12138]

I'm not sure, but these CI errors with macOS don't seem like the issue with this patch, do they?

[philnik]

In D144363#4524542, @Joy12138 wrote:

I'm not sure, but these CI errors with macOS don't seem like the issue with this patch, do they?

They are probably unrelated. A rebase should fix them.

[Joy12138]

Rebase

[Joy12138]

Rebase

[Joy12138]

Rebase

[Joy12138]

Rebase

[mgorny]

I'm seeing a bunch of test failures with this (and the subsequent) changes on 32-bit x86. They all seem to be related to size assertions, e.g.:

$ ":" "COMPILED WITH"
$ "/usr/lib/ccache/bin/i686-pc-linux-gnu-clang++" "/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/libcxx/test/std/experimental/simd/simd.class/simd_alias.pass.cpp" "-pthread" "--target=i686-pc-linux-g
nu" "-nostdinc++" "-I" "/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/runtimes_build-abi_x86_32.x86/include/c++/v1" "-I" "/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/runtimes_build-abi_x
86_32.x86/include/c++/v1" "-I" "/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/libcxx/test/support" "-std=c++26" "-Werror" "-Wall" "-Wctad-maybe-unsupported" "-Wextra" "-Wshadow" "-Wundef" "-Wunused-t
emplate" "-Wno-unused-command-line-argument" "-Wno-attributes" "-Wno-pessimizing-move" "-Wno-noexcept-type" "-Wno-atomic-alignment" "-Wno-reserved-module-identifier" "-Wno-user-defined-literals" "-Wno-tautologi
cal-compare" "-Wsign-compare" "-Wunused-variable" "-Wunused-parameter" "-Wunreachable-code" "-Wno-unused-local-typedef" "-Wno-local-type-template-args" "-Wno-c++11-extensions" "-Wno-unknown-pragmas" "-Wno-pass-
failed" "-Wno-mismatched-new-delete" "-Wno-redundant-move" "-Wno-self-move" "-D_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER" "-D_LIBCPP_ENABLE_EXPERIMENTAL" "-Werror=thread-safety" "-Wuser-defined-warnings" "-lc++experi
mental" "-nostdlib++" "-L" "/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/runtimes_build-abi_x86_32.x86/lib" "-Wl,-rpath,/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/runtimes_build-abi_x8
6_32.x86/lib" "-lc++" "-o" "/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/runtimes_build-abi_x86_32.x86/test/std/experimental/simd/simd.class/Output/simd_alias.pass.cpp.dir/t.tmp.exe"
# command stderr:
In file included from /var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/libcxx/test/std/experimental/simd/simd.class/simd_alias.pass.cpp:19:
In file included from /var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/libcxx/test/std/experimental/simd/simd.class/../test_utils.h:17:
In file included from /var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/runtimes_build-abi_x86_32.x86/include/c++/v1/experimental/simd:81:
In file included from /var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/runtimes_build-abi_x86_32.x86/include/c++/v1/experimental/__simd/abi_tag.h:14:
/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/runtimes_build-abi_x86_32.x86/include/c++/v1/experimental/__simd/vec_ext.h:31:29: error: vector size not an integral multiple of component size
   31 |   _Tp __data __attribute__((__vector_size__(std::__bit_ceil((sizeof(_Tp) * _Np)))));
      |                             ^               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/runtimes_build-abi_x86_32.x86/include/c++/v1/experimental/__simd/simd.h:33:12: note: in instantiation of template class 'std::experimental::__simd_storag
e<long double, std::experimental::simd_abi::__vec_ext<1>>' requested here
   33 |   _Storage __s_;
      |            ^
/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/libcxx/test/std/experimental/simd/simd.class/simd_alias.pass.cpp:28:47: note: in instantiation of template class 'std::experimental::simd<long double, st
d::experimental::simd_abi::__vec_ext<1>>' requested here
   28 |     static_assert(std::is_same_v<typename ex::simd<T, SimdAbi>::value_type, T>);
      |                                               ^
/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/libcxx/test/support/type_algorithms.h:52:23: note: in instantiation of function template specialization 'CheckSimdAlias<long double, 1>::operator()<std::
experimental::simd_abi::__vec_ext<1>>' requested here
   52 |   swallow((f.template operator()<Types>(), 0)...);
      |                       ^
/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/libcxx/test/support/type_algorithms.h:52:23: note: in instantiation of function template specialization 'TestAllSimdAbiFunctor<CheckSimdAlias>::operator(
)<long double>' requested here
/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/libcxx/test/std/experimental/simd/simd.class/simd_alias.pass.cpp:35:3: note: in instantiation of function template specialization 'test_all_simd_abi<CheckSimdAlias>' requested here
   35 |   test_all_simd_abi<CheckSimdAlias>();
      |   ^
In file included from /var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/libcxx/test/std/experimental/simd/simd.class/simd_alias.pass.cpp:19:
In file included from /var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/libcxx/test/std/experimental/simd/simd.class/../test_utils.h:18:
/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/libcxx/test/support/type_algorithms.h:52:23: error: no matching member function for call to 'operator()'
   52 |   swallow((f.template operator()<Types>(), 0)...);
      |            ~~~~~~~~~~~^~~~~~~~~~~~~~~~~
/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/libcxx/test/std/experimental/simd/simd.class/../test_utils.h:31:13: note: in instantiation of function template specialization 'types::for_each<std::expe
rimental::simd_abi::__vec_ext<1>, std::experimental::simd_abi::__vec_ext<1>, CheckSimdAlias<long double, 1>>' requested here
   31 |     (types::for_each(sized_abis<T, Ns + 1>{}, F<T, Ns + 1>{}), ...);
      |             ^
/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/libcxx/test/std/experimental/simd/simd.class/../test_utils.h:39:5: note: in instantiation of function template specialization 'TestAllSimdAbiFunctor<Chec
kSimdAlias>::instantiate_with_n<long double, 0U, 1U, 2U, 3U, 4U, 5U, 6U, 7U, 8U, 9U, 10U, 11U, 12U, 13U, 14U, 15U, 16U, 17U, 18U, 19U, 20U, 21U, 22U, 23U, 24U, 25U, 26U, 27U, 28U, 29U, 30U>' requested here
   39 |     instantiate_with_n<T>(std::make_index_sequence<max_simd_size - 1>{});
      |     ^
/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/libcxx/test/support/type_algorithms.h:52:23: note: in instantiation of function template specialization 'TestAllSimdAbiFunctor<CheckSimdAlias>::operator()<long double>' requested here
   52 |   swallow((f.template operator()<Types>(), 0)...);
      |                       ^
/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/libcxx/test/std/experimental/simd/simd.class/simd_alias.pass.cpp:35:3: note: in instantiation of function template specialization 'test_all_simd_abi<Chec
kSimdAlias>' requested here
   35 |   test_all_simd_abi<CheckSimdAlias>();
      |   ^
/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/libcxx/test/std/experimental/simd/simd.class/simd_alias.pass.cpp:27:8: note: candidate template ignored: substitution failure [with SimdAbi = std::experi
mental::simd_abi::__vec_ext<1>]
   27 |   void operator()() {
      |        ^

----

$ ":" "COMPILED WITH"
$ "/usr/lib/ccache/bin/i686-pc-linux-gnu-clang++" "/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/libcxx/test/std/experimental/simd/simd.mask.class/simd_mask_alias.pass.cpp" "-pthread" "--target=i686-pc-linux-gnu" "-nostdinc++" "-I" "/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/runtimes_build-abi_x86_32.x86/include/c++/v1" "-I" "/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/runtimes_build-abi_x86_32.x86/include/c++/v1" "-I" "/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/libcxx/test/support" "-std=c++26" "-Werror" "-Wall" "-Wctad-maybe-unsupported" "-Wextra" "-Wshadow" "-Wundef" "-Wunused-template" "-Wno-unused-command-line-argument" "-Wno-attributes" "-Wno-pessimizing-move" "-Wno-noexcept-type" "-Wno-atomic-alignment" "-Wno-reserved-module-identifier" "-Wno-user-defined-literals" "-Wno-tautological-compare" "-Wsign-compare" "-Wunused-variable" "-Wunused-parameter" "-Wunreachable-code" "-Wno-unused-local-typedef" "-Wno-local-type-template-args" "-Wno-c++11-extensions" "-Wno-unknown-pragmas" "-Wno-pass-failed" "-Wno-mismatched-new-delete" "-Wno-redundant-move" "-Wno-self-move" "-D_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER" "-D_LIBCPP_ENABLE_EXPERIMENTAL" "-Werror=thread-safety" "-Wuser-defined-warnings" "-lc++experimental" "-nostdlib++" "-L" "/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/runtimes_build-abi_x86_32.x86/lib" "-Wl,-rpath,/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/runtimes_build-abi_x86_32.x86/lib" "-lc++" "-o" "/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/runtimes_build-abi_x86_32.x86/test/std/experimental/simd/simd.mask.class/Output/simd_mask_alias.pass.cpp.dir/t.tmp.exe"
# command stderr:
In file included from /var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/libcxx/test/std/experimental/simd/simd.mask.class/simd_mask_alias.pass.cpp:19:
In file included from /var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/libcxx/test/std/experimental/simd/simd.mask.class/../test_utils.h:17:
In file included from /var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/runtimes_build-abi_x86_32.x86/include/c++/v1/experimental/simd:81:
In file included from /var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/runtimes_build-abi_x86_32.x86/include/c++/v1/experimental/__simd/abi_tag.h:14:
In file included from /var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/runtimes_build-abi_x86_32.x86/include/c++/v1/experimental/__simd/vec_ext.h:16:
/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/runtimes_build-abi_x86_32.x86/include/c++/v1/experimental/__simd/utility.h:53:19: error: static assertion failed due to requirement 'sizeof(long double) == 0': Unexpected size
   53 |     static_assert(sizeof(_Tp) == 0, "Unexpected size");
      |                   ^~~~~~~~~~~~~~~~
/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/runtimes_build-abi_x86_32.x86/include/c++/v1/experimental/__simd/vec_ext.h:45:45: note: in instantiation of function template specialization 'std::experimental::__choose_mask_type<long double>' requested here
   45 |     : __simd_storage<decltype(experimental::__choose_mask_type<_Tp>()), simd_abi::__vec_ext<_Np>> {};
      |                                             ^
/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/runtimes_build-abi_x86_32.x86/include/c++/v1/experimental/__simd/simd_mask.h:31:12: note: in instantiation of template class 'std::experimental::__mask_storage<long double, std::experimental::simd_abi::__vec_ext<1>>' requested here
   31 |   _Storage __s_;
      |            ^
/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/libcxx/test/std/experimental/simd/simd.mask.class/simd_mask_alias.pass.cpp:28:47: note: in instantiation of template class 'std::experimental::simd_mask<long double, std::experimental::simd_abi::__vec_ext<1>>' requested here
   28 |     static_assert(std::is_same_v<typename ex::simd_mask<T, SimdAbi>::value_type, bool>);
      |                                               ^
/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/libcxx/test/support/type_algorithms.h:52:23: note: in instantiation of function template specialization 'CheckSimdMaskAlias<long double, 1>::operator()<std::experimental::simd_abi::__vec_ext<1>>' requested here
   52 |   swallow((f.template operator()<Types>(), 0)...);
      |                       ^
/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/libcxx/test/support/type_algorithms.h:52:23: note: in instantiation of function template specialization 'TestAllSimdAbiFunctor<CheckSimdMaskAlias>::operator()<long double>' requested here
/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/libcxx/test/std/experimental/simd/simd.mask.class/simd_mask_alias.pass.cpp:35:3: note: in instantiation of function template specialization 'test_all_simd_abi<CheckSimdMaskAlias>' requested here
   35 |   test_all_simd_abi<CheckSimdMaskAlias>();
      |   ^
/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/runtimes_build-abi_x86_32.x86/include/c++/v1/experimental/__simd/utility.h:53:31: note: expression evaluates to '12 == 0'
   53 |     static_assert(sizeof(_Tp) == 0, "Unexpected size");
      |                   ~~~~~~~~~~~~^~~~

Full log (.xz, 2.8M uncompressed):

sys-libs:libcxx-18.0.0_pre20230912:20230912-085749.log.xz113 KBDownload

[Joy12138]

Thank you very much for your reminder. I tried to fix this issue in revision https://reviews.llvm.org/D159509 and land this patch after CI passed.

[mgorny]

In D144363#4644854, @Joy12138 wrote:

Thank you very much for your reminder. I tried to fix this issue in revision https://reviews.llvm.org/D159509 and land this patch after CI passed.

I'm getting the same errors after this change (tested on 2f005df066e07d93e3d6aa04748c158f883197b7).

Note the specific errors are:

/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/runtimes_build-abi_x86_32.x86/include/c++/v1/experimental/__simd/vec_ext.h:31:29: error: vector size not an integral multiple of component size
   31 |   _Tp __data __attribute__((__vector_size__(std::__bit_ceil((sizeof(_Tp) * _Np)))));
      |                             ^               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

and:

/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/runtimes_build-abi_x86_32.x86/include/c++/v1/experimental/__simd/utility.h:53:19: error: static assertion failed due to requirement 'sizeof(long double) == 0': Unexpected size
   53 |     static_assert(sizeof(_Tp) == 0, "Unexpected size");
      |                   ^~~~~~~~~~~~~~~~

[Joy12138]

In D144363#4645309, @mgorny wrote:

In D144363#4644854, @Joy12138 wrote:

Thank you very much for your reminder. I tried to fix this issue in revision https://reviews.llvm.org/D159509 and land this patch after CI passed.

I'm getting the same errors after this change (tested on 2f005df066e07d93e3d6aa04748c158f883197b7).

Note the specific errors are:

/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/runtimes_build-abi_x86_32.x86/include/c++/v1/experimental/__simd/vec_ext.h:31:29: error: vector size not an integral multiple of component size
   31 |   _Tp __data __attribute__((__vector_size__(std::__bit_ceil((sizeof(_Tp) * _Np)))));
      |                             ^               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

and:

/var/tmp/portage/sys-libs/libcxx-18.0.0_pre20230912/work/runtimes_build-abi_x86_32.x86/include/c++/v1/experimental/__simd/utility.h:53:19: error: static assertion failed due to requirement 'sizeof(long double) == 0': Unexpected size
   53 |     static_assert(sizeof(_Tp) == 0, "Unexpected size");
      |                   ^~~~~~~~~~~~~~~~

Sorry. Because this issue did not appear in the CI of above revision, I presumed that it is related to another issue that appeared in the CI. But it does not seem like this. I am trying to reproduce and resolve it by https://reviews.llvm.org/D159514. This time, I will ensure that the modifications can pass the test on 2f005df066e07d93e3d6aa04748c158f883197b7

libcxx/docs/Status/ParallelismProjects.csv

 Section,Description,Dependencies,Assignee,Complete
 | `[parallel.exceptions] <https://wg21.link/N4808>`_, "Parallel Exceptions", None, unassigned, |Not Started|
 | `[parallel.execpol] <https://wg21.link/N4808>`_, "Execution policies", None, unassigned, |Not Started|
 | `[parallel.alg] <https://wg21.link/N4808>`_, "Parallel algorithms", None, unassigned, |Not Started|
 | `[parallel.taskblock] <https://wg21.link/N4808>`_, "Task Block", None, unassigned, |Not Started|
 | `[parallel.simd.abi] <https://wg21.link/N4808>`_, "`simd ABI tags <https://reviews.llvm.org/D144362>`_", [parallel.simd.class] [parallel.simd.mask.class] declarations and alias, Yin Zhang, |Complete|
 | `[parallel.simd.traits] <https://wg21.link/N4808>`_, "`simd type traits is_abi_tag[_v] <https://reviews.llvm.org/D144362>`_", [parallel.simd.abi], Yin Zhang, |Complete|
 | `[parallel.simd.traits] <https://wg21.link/N4808>`_, "`simd type traits is_simd[_v] <https://reviews.llvm.org/D144362>`_", [parallel.simd.class] declaration and alias, Yin Zhang, |Complete|
 | `[parallel.simd.traits] <https://wg21.link/N4808>`_, "`simd type traits is_simd_mask[_v] <https://reviews.llvm.org/D144362>`_", [parallel.simd.mask.class] declaration and alias, Yin Zhang, |Complete|
 | `[parallel.simd.traits] <https://wg21.link/N4808>`_, "simd type traits is_simd_flag_type", None, Yin Zhang, |In Progress|
-| `[parallel.simd.traits] <https://wg21.link/N4808>`_, "simd type traits simd_size", None, Yin Zhang, |In Progress|
+| `[parallel.simd.traits] <https://wg21.link/N4808>`_, "`simd type traits simd_size[_v] <https://reviews.llvm.org/D144363>`_", [parallel.simd.traits] is_abi_tag[_v], Yin Zhang, |Complete|
 | `[parallel.simd.traits] <https://wg21.link/N4808>`_, "simd type traits memory_alignment", None, Yin Zhang, |In Progress|
 | `[parallel.simd.traits] <https://wg21.link/N4808>`_, "simd type traits rebind_simd", None, Yin Zhang, |In Progress|
 | `[parallel.simd.traits] <https://wg21.link/N4808>`_, "simd type traits resize_simd", None, Yin Zhang, |In Progress|
 | `[parallel.simd.whereexpr] <https://wg21.link/N4808>`_, "Where expression class templates", None, Yin Zhang, |In Progress|
 | `[parallel.simd.class] <https://wg21.link/N4808>`_, "`Class template simd declaration and alias <https://reviews.llvm.org/D144362>`_", [parallel.simd.abi], Yin Zhang, |Complete|
+| `[parallel.simd.class] <https://wg21.link/N4808>`_, "`simd<>::size() <https://reviews.llvm.org/D144363>`_", [parallel.simd.traits] simd_size[_v], Yin Zhang, |Complete|
 | `[parallel.simd.class] <https://wg21.link/N4808>`_, "Class template simd implementation", None, Yin Zhang, |In Progress|
 | `[parallel.simd.nonmembers] <https://wg21.link/N4808>`_, "simd non-member operations", None, Yin Zhang, |In Progress|
 | `[parallel.simd.mask.class] <https://wg21.link/N4808>`_, "`Class template simd_mask declaration and alias <https://reviews.llvm.org/D144362>`_", [parallel.simd.abi], Yin Zhang, |Complete|
+| `[parallel.simd.mask.class] <https://wg21.link/N4808>`_, "`simd_mask<>::size() <https://reviews.llvm.org/D144363>`_", [parallel.simd.class] simd<>::size(), Yin Zhang, |Complete|
 | `[parallel.simd.mask.class] <https://wg21.link/N4808>`_, "Class template simd_mask implementation", None, Yin Zhang, |In Progress|
 | `[parallel.simd.mask.nonmembers] <https://wg21.link/N4808>`_, "simd_mask non-member operations", None, Yin Zhang, |In Progress|

libcxx/include/CMakeLists.txt

set(files
   deque
   errno.h
   exception
   execution
   expected
   experimental/__config
   experimental/__memory
   experimental/__simd/abi_tag.h
+  experimental/__simd/declaration.h
   experimental/__simd/scalar.h
   experimental/__simd/simd.h
   experimental/__simd/simd_mask.h
   experimental/__simd/traits.h
+  experimental/__simd/utility.h
   experimental/__simd/vec_ext.h
   experimental/deque
   experimental/forward_list
   experimental/iterator
   experimental/list
   experimental/map
   experimental/memory_resource
   experimental/propagate_const

libcxx/include/experimental/__simd/declaration.h

 // -*- C++ -*-
 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef _LIBCPP_EXPERIMENTAL___SIMD_SIMD_H
-#define _LIBCPP_EXPERIMENTAL___SIMD_SIMD_H
-
-#include <experimental/__simd/abi_tag.h>
+#ifndef _LIBCPP_EXPERIMENTAL___SIMD_DECLARATION_H
+#define _LIBCPP_EXPERIMENTAL___SIMD_DECLARATION_H
 
 #if _LIBCPP_STD_VER >= 17 && defined(_LIBCPP_ENABLE_EXPERIMENTAL)
 
 _LIBCPP_BEGIN_NAMESPACE_EXPERIMENTAL
 inline namespace parallelism_v2 {
 
-// class template simd [simd.class]
-// TODO: implement simd class
 template <class _Tp, class _Abi = simd_abi::compatible<_Tp>>
 class simd;
 
-template <class _Tp>
-using native_simd = simd<_Tp, simd_abi::native<_Tp>>;
-
-template <class _Tp, int _Np>
-using fixed_size_simd = simd<_Tp, simd_abi::fixed_size<_Np>>;
+template <class _Tp, class _Abi = simd_abi::compatible<_Tp>>
+class simd_mask;
 
 } // namespace parallelism_v2
 _LIBCPP_END_NAMESPACE_EXPERIMENTAL
 
 #endif // _LIBCPP_STD_VER >= 17 && defined(_LIBCPP_ENABLE_EXPERIMENTAL)
-#endif // _LIBCPP_EXPERIMENTAL___SIMD_SIMD_H
+#endif // _LIBCPP_EXPERIMENTAL___SIMD_DECLARATION_H

libcxx/include/experimental/__simd/simd.h

 // -*- C++ -*-
 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef _LIBCPP_EXPERIMENTAL___SIMD_SIMD_H
 #define _LIBCPP_EXPERIMENTAL___SIMD_SIMD_H
 
 #include <experimental/__simd/abi_tag.h>
+#include <experimental/__simd/declaration.h>
+#include <experimental/__simd/traits.h>
 
 #if _LIBCPP_STD_VER >= 17 && defined(_LIBCPP_ENABLE_EXPERIMENTAL)
 
 _LIBCPP_BEGIN_NAMESPACE_EXPERIMENTAL
 inline namespace parallelism_v2 {
 
 // class template simd [simd.class]
 // TODO: implement simd class
-template <class _Tp, class _Abi = simd_abi::compatible<_Tp>>
-class simd;
+template <class _Tp, class _Abi>
+class simd {
+public:
+  using value_type = _Tp;
+  using mask_type  = simd_mask<_Tp, _Abi>;
+  using abi_type   = _Abi;
+
+  static _LIBCPP_HIDE_FROM_ABI constexpr size_t size() noexcept { return simd_size_v<value_type, abi_type>; }
+};
 
 template <class _Tp>
 using native_simd = simd<_Tp, simd_abi::native<_Tp>>;
 
 template <class _Tp, int _Np>
 using fixed_size_simd = simd<_Tp, simd_abi::fixed_size<_Np>>;
 
 } // namespace parallelism_v2
 _LIBCPP_END_NAMESPACE_EXPERIMENTAL
 
 #endif // _LIBCPP_STD_VER >= 17 && defined(_LIBCPP_ENABLE_EXPERIMENTAL)
 #endif // _LIBCPP_EXPERIMENTAL___SIMD_SIMD_H

libcxx/include/experimental/__simd/simd_mask.h

 // -*- C++ -*-
 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef _LIBCPP_EXPERIMENTAL___SIMD_SIMD_MASK_H
 #define _LIBCPP_EXPERIMENTAL___SIMD_SIMD_MASK_H
 
 #include <experimental/__simd/abi_tag.h>
+#include <experimental/__simd/declaration.h>
 
 #if _LIBCPP_STD_VER >= 17 && defined(_LIBCPP_ENABLE_EXPERIMENTAL)
 
 _LIBCPP_BEGIN_NAMESPACE_EXPERIMENTAL
 inline namespace parallelism_v2 {
 
 // class template simd_mask [simd.mask.class]
 // TODO: implement simd_mask class
-template <class _Tp, class _Abi = simd_abi::compatible<_Tp>>
-class simd_mask;
+template <class _Tp, class _Abi>
+class simd_mask {
+public:
+  using value_type = bool;
+  using simd_type  = simd<_Tp, _Abi>;
+  using abi_type   = _Abi;
+
+  static _LIBCPP_HIDE_FROM_ABI constexpr size_t size() noexcept { return simd_type::size(); }
+};
 
 template <class _Tp>
 using native_simd_mask = simd_mask<_Tp, simd_abi::native<_Tp>>;
 
 template <class _Tp, int _Np>
 using fixed_size_simd_mask = simd_mask<_Tp, simd_abi::fixed_size<_Np>>;
 
 } // namespace parallelism_v2
 _LIBCPP_END_NAMESPACE_EXPERIMENTAL
 
 #endif // _LIBCPP_STD_VER >= 17 && defined(_LIBCPP_ENABLE_EXPERIMENTAL)
 #endif // _LIBCPP_EXPERIMENTAL___SIMD_SIMD_MASK_H

libcxx/include/experimental/__simd/traits.h

 // -*- C++ -*-
 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef _LIBCPP_EXPERIMENTAL___SIMD_TRAITS_H
 #define _LIBCPP_EXPERIMENTAL___SIMD_TRAITS_H
 
 #include <experimental/__simd/abi_tag.h>
-#include <experimental/__simd/simd.h>
-#include <experimental/__simd/simd_mask.h>
+#include <experimental/__simd/declaration.h>
+#include <experimental/__simd/utility.h>
 
 #if _LIBCPP_STD_VER >= 17 && defined(_LIBCPP_ENABLE_EXPERIMENTAL)
 
 _LIBCPP_BEGIN_NAMESPACE_EXPERIMENTAL
 inline namespace parallelism_v2 {
 
 // traits [simd.traits]
 template <class _Tp>

 inline constexpr bool is_simd_mask_v = false;
 
 template <class _Tp, class _Abi>
 inline constexpr bool is_simd_mask_v<simd_mask<_Tp, _Abi>> = true;
 
 template <class _Tp>
 struct is_simd_mask : bool_constant<is_simd_mask_v<_Tp>> {};
 
+template <class _Tp, class _Abi = simd_abi::compatible<_Tp>, bool = (__is_vectorizable_v<_Tp> && is_abi_tag_v<_Abi>)>
+struct simd_size : integral_constant<size_t, _Abi::__simd_size> {};
+
+template <class _Tp, class _Abi>
+struct simd_size<_Tp, _Abi, false> {};
+
+template <class _Tp, class _Abi = simd_abi::compatible<_Tp>>
+inline constexpr size_t simd_size_v = simd_size<_Tp, _Abi>::value;
+
 } // namespace parallelism_v2
 _LIBCPP_END_NAMESPACE_EXPERIMENTAL
 
 #endif // _LIBCPP_STD_VER >= 17 && defined(_LIBCPP_ENABLE_EXPERIMENTAL)
 #endif // _LIBCPP_EXPERIMENTAL___SIMD_TRAITS_H

libcxx/include/experimental/__simd/utility.h

 // -*- C++ -*-
 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef _LIBCPP_EXPERIMENTAL___SIMD_SIMD_H
-#define _LIBCPP_EXPERIMENTAL___SIMD_SIMD_H
+#ifndef _LIBCPP_EXPERIMENTAL___SIMD_UTILITY_H
+#define _LIBCPP_EXPERIMENTAL___SIMD_UTILITY_H
 
-#include <experimental/__simd/abi_tag.h>
+#include <__type_traits/is_arithmetic.h>
+#include <__type_traits/is_const.h>
+#include <__type_traits/is_same.h>
+#include <__type_traits/is_volatile.h>
 
 #if _LIBCPP_STD_VER >= 17 && defined(_LIBCPP_ENABLE_EXPERIMENTAL)
 
 _LIBCPP_BEGIN_NAMESPACE_EXPERIMENTAL
 inline namespace parallelism_v2 {
-
-// class template simd [simd.class]
-// TODO: implement simd class
-template <class _Tp, class _Abi = simd_abi::compatible<_Tp>>
-class simd;
-
 template <class _Tp>
-using native_simd = simd<_Tp, simd_abi::native<_Tp>>;
-
-template <class _Tp, int _Np>
-using fixed_size_simd = simd<_Tp, simd_abi::fixed_size<_Np>>;
-
+constexpr bool __is_vectorizable_v =
+    is_arithmetic_v<_Tp> && !is_const_v<_Tp> && !is_volatile_v<_Tp> && !is_same_v<_Tp, bool>;
 } // namespace parallelism_v2
 _LIBCPP_END_NAMESPACE_EXPERIMENTAL
 
 #endif // _LIBCPP_STD_VER >= 17 && defined(_LIBCPP_ENABLE_EXPERIMENTAL)
-#endif // _LIBCPP_EXPERIMENTAL___SIMD_SIMD_H
+#endif // _LIBCPP_EXPERIMENTAL___SIMD_UTILITY_H

libcxx/include/experimental/simd

inline namespace parallelism_v2 {
   template<class T> inline constexpr bool is_abi_tag_v = is_abi_tag<T>::value;
 
   template <class T> struct is_simd;
   template <class T> inline constexpr bool is_simd_v = is_simd<T>::value;
 
   template <class T> struct is_simd_mask;
   template <class T> inline constexpr bool is_simd_mask_v = is_simd_mask<T>::value;
 
+  template<class T, class Abi = simd_abi::compatible<T>> struct simd_size;
+  template<class T, class Abi = simd_abi::compatible<T>>
+    inline constexpr size_t simd_size_v = simd_size<T,Abi>::value;
+
 } // namespace parallelism_v2
 } // namespace std::experimental
 
 */
 
 #include <__assert> // all public C++ headers provide the assertion handler
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)

libcxx/test/std/experimental/simd/simd.class/simd_alias.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14
+
+// Test the alias.
+// template <class T, class Abi> class simd {
+// public:
+//   using value_type = T;
+//   using mask_type = simd_mask<T, Abi>;
+//   using abi_type = Abi;
+// };
+
+#include "../test_utils.h"
+#include <experimental/simd>
+
+namespace ex = std::experimental::parallelism_v2;
+
+template <class T, std::size_t>
+struct CheckSimdAlias {
+  template <class SimdAbi>
+  void operator()() {
+    static_assert(std::is_same_v<typename ex::simd<T, SimdAbi>::value_type, T>);
+    static_assert(std::is_same_v<typename ex::simd<T, SimdAbi>::mask_type, ex::simd_mask<T, SimdAbi>>);
+    static_assert(std::is_same_v<typename ex::simd<T, SimdAbi>::abi_type, SimdAbi>);
+  }
+};
+
+int main(int, char**) {
+  test_all_simd_abi<CheckSimdAlias>();
+  return 0;
+}

libcxx/test/std/experimental/simd/simd.class/simd_width.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14
+
+// <experimental/simd>
+//
+// [simd.class]
+// static constexpr std::size_t size() noexcept;
+
+#include "../test_utils.h"
+
+namespace ex = std::experimental::parallelism_v2;
+
+template <class T, std::size_t>
+struct CheckSimdWidth {
+  template <class SimdAbi>
+  void operator()() {
+    static_assert(ex::simd<T, SimdAbi>::size() == ex::simd_size_v<T, SimdAbi>);
+  }
+};
+
+int main(int, char**) {
+  test_all_simd_abi<CheckSimdWidth>();
+  return 0;
+}

libcxx/test/std/experimental/simd/simd.mask.class/simd_mask_alias.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14
+
+// Test the alias.
+// template <class T, class Abi> class simd_mask {
+// public:
+//   using value_type = bool;
+//   using simd_type = simd<T, Abi>;
+//   using abi_type = Abi;
+// };
+
+#include "../test_utils.h"
+#include <experimental/simd>
+
+namespace ex = std::experimental::parallelism_v2;
+
+template <class T, std::size_t>
+struct CheckSimdMaskAlias {
+  template <class SimdAbi>
+  void operator()() {
+    static_assert(std::is_same_v<typename ex::simd_mask<T, SimdAbi>::value_type, bool>);
+    static_assert(std::is_same_v<typename ex::simd_mask<T, SimdAbi>::simd_type, ex::simd<T, SimdAbi>>);
+    static_assert(std::is_same_v<typename ex::simd_mask<T, SimdAbi>::abi_type, SimdAbi>);
+  }
+};
+
+int main(int, char**) {
+  test_all_simd_abi<CheckSimdMaskAlias>();
+  return 0;
+}

libcxx/test/std/experimental/simd/simd.mask.class/simd_mask_width.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14
+
+// <experimental/simd>
+//
+// [simd.mask.class]
+// static constexpr std::size_t size() noexcept;
+
+#include "../test_utils.h"
+
+namespace ex = std::experimental::parallelism_v2;
+
+template <class T, std::size_t>
+struct CheckSimdMaskWidth {
+  template <class SimdAbi>
+  void operator()() {
+    static_assert(ex::simd_mask<T, SimdAbi>::size() == ex::simd_size_v<T, SimdAbi>);
+  }
+};
+
+int main(int, char**) {
+  test_all_simd_abi<CheckSimdMaskWidth>();
+  return 0;
+}

libcxx/test/std/experimental/simd/simd.traits/simd_size.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14
+
+// <experimental/simd>
+//
+// [simd.traits]
+//template <class T, class Abi = simd_abi::compatible<T>> struct simd_size;
+//template <class T, class Abi = simd_abi::compatible<T>>
+//inline constexpr std::size_t ex::simd_size_v = ex::simd_size<T, Abi>::value;
+
+#include "../test_utils.h"
+
+namespace ex = std::experimental::parallelism_v2;
+
+struct CheckSimdSizeFixedDeduce {
+  template <class T, std::size_t N>
+  void check() {
+    static_assert(ex::simd_size_v<T, ex::simd_abi::fixed_size<N>> == N, "Simd size mismatch with abi fixed_size");
+    static_assert(ex::simd_size<T, ex::simd_abi::fixed_size<N>>::value == N, "Simd size mismatch with abi fixed_size");
+
+    static_assert(ex::simd_size_v<T, ex::simd_abi::deduce_t<T, N>> == N, "Simd size mismatch with abi deduce");
+    static_assert(ex::simd_size<T, ex::simd_abi::deduce_t<T, N>>::value == N, "Simd size mismatch with abi deduce");
+  }
+
+  template <class T, std::size_t... N>
+  void performChecks(std::index_sequence<N...>) {
+    (check<T, N + 1>(), ...);
+  }
+
+  template <class T>
+  void operator()() {
+    performChecks<T>(std::make_index_sequence<max_simd_size>{});
+  }
+};
+
+struct CheckSimdSizeScalarNativeCompatible {
+  template <class T>
+  void operator()() {
+    static_assert(ex::simd_size_v<T, ex::simd_abi::scalar> == 1);
+    static_assert(ex::simd_size<T, ex::simd_abi::scalar>::value == 1);
+
+    LIBCPP_STATIC_ASSERT(ex::simd_size<T, ex::simd_abi::compatible<T>>::value == 16 / sizeof(T));
+    LIBCPP_STATIC_ASSERT(ex::simd_size_v<T, ex::simd_abi::compatible<T>> == 16 / sizeof(T));
+
+    LIBCPP_STATIC_ASSERT(
+        ex::simd_size<T, ex::simd_abi::native<T>>::value == _LIBCPP_NATIVE_SIMD_WIDTH_IN_BYTES / sizeof(T));
+    LIBCPP_STATIC_ASSERT(ex::simd_size_v<T, ex::simd_abi::native<T>> == _LIBCPP_NATIVE_SIMD_WIDTH_IN_BYTES / sizeof(T));
+  }
+};
+
+template <class T, class Abi = ex::simd_abi::compatible<T>, class = void>
+struct has_simd_size : std::false_type {};
+
+template <class T, class Abi>
+struct has_simd_size<T, Abi, std::void_t<decltype(ex::simd_size<T, Abi>::value)>> : std::true_type {};
+
+struct CheckSimdSizeTraits {
+  template <class T>
+  void operator()() {
+    static_assert(has_simd_size<T>::value);
+    static_assert(!has_simd_size<ex::native_simd<T>>::value);
+
+    static_assert(has_simd_size<T, ex::simd_abi::scalar>::value);
+    static_assert(has_simd_size<T, ex::simd_abi::fixed_size<4>>::value);
+    static_assert(has_simd_size<T, ex::simd_abi::native<T>>::value);
+    static_assert(has_simd_size<T, ex::simd_abi::compatible<T>>::value);
+
+    static_assert(!has_simd_size<ex::simd_abi::native<T>, ex::simd_abi::native<T>>::value);
+    static_assert(!has_simd_size<ex::native_simd<T>, ex::simd_abi::native<T>>::value);
+    static_assert(!has_simd_size<ex::fixed_size_simd<T, 3>, ex::simd_abi::native<T>>::value);
+    static_assert(!has_simd_size<ex::fixed_size_simd_mask<T, 4>, ex::simd_abi::native<T>>::value);
+
+    static_assert(!has_simd_size<T, T>::value);
+    static_assert(!has_simd_size<T, ex::native_simd<T>>::value);
+    static_assert(!has_simd_size<T, ex::fixed_size_simd<T, 3>>::value);
+    static_assert(!has_simd_size<T, ex::fixed_size_simd_mask<T, 4>>::value);
+  }
+};
+
+int main(int, char**) {
+  types::for_each(arithmetic_no_bool_types(), CheckSimdSizeFixedDeduce());
+  types::for_each(arithmetic_no_bool_types(), CheckSimdSizeScalarNativeCompatible());
+  types::for_each(arithmetic_no_bool_types(), CheckSimdSizeTraits());
+  return 0;
+}

libcxx/test/std/experimental/simd/simd.traits/simd_size.verify.cpp

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14
+
+// <experimental/simd>
+//
+// [simd.traits]
+//template <class T, class Abi = simd_abi::compatible<T>> struct simd_size;
+//template <class T, class Abi = simd_abi::compatible<T>>
+//inline constexpr std::size_t ex::simd_size_v = ex::simd_size<T, Abi>::value;
+
+#include <experimental/simd>
+
+namespace ex = std::experimental::parallelism_v2;
+
+int main(int, char**) {
+  (void)ex::simd_size<bool, ex::simd_abi::compatible<bool>>::value;
+  // expected-error-re@* {{no member named 'value' in {{.*}}}}
+  (void)ex::simd_size<ex::native_simd<int>, ex::simd_abi::native<int>>::value;
+  // expected-error-re@* {{no member named 'value' in {{.*}}}}
+  (void)ex::simd_size<int, int>::value;
+  // expected-error-re@* {{no member named 'value' in {{.*}}}}
+  (void)ex::simd_size<int, ex::native_simd<int>>::value;
+  // expected-error-re@* {{no member named 'value' in {{.*}}}}
+
+  (void)ex::simd_size_v<bool, ex::simd_abi::compatible<bool>>;
+  // expected-error-re@* {{no member named 'value' in {{.*}}}}
+  (void)ex::simd_size_v<ex::native_simd<int>, ex::simd_abi::native<int>>;
+  // expected-error-re@* {{no member named 'value' in {{.*}}}}
+  (void)ex::simd_size_v<int, int>;
+  // expected-error-re@* {{no member named 'value' in {{.*}}}}
+  (void)ex::simd_size_v<int, ex::native_simd<int>>;
+  // expected-error-re@* {{no member named 'value' in {{.*}}}}
+
+  return 0;
+}

libcxx/test/std/experimental/simd/test_utils.h

struct TestAllSimdAbiFunctor {
   void operator()() {
     using abis = types::type_list<ex::simd_abi::scalar, ex::simd_abi::native<T>, ex::simd_abi::compatible<T>>;
     types::for_each(abis{}, F<T, 1>());
 
     instantiate_with_n<T>(std::make_index_sequence<max_simd_size - 1>{});
   }
 };
 
+using arithmetic_no_bool_types = types::concatenate_t<types::integer_types, types::floating_point_types>;
+
 template <template <class T, std::size_t N> class Func>
 void test_all_simd_abi() {
-  using arithmetic_no_bool_types = types::concatenate_t<types::integer_types, types::floating_point_types>;
   types::for_each(arithmetic_no_bool_types(), TestAllSimdAbiFunctor<Func>());
 }
 
 #endif // TEST_UTIL_H