[libcxx] <experimental/simd> Add ABI tags, class template simd/simd_mask implementations. Add related simd traits and tests.

[Joy12138]

Summary

[libcxx] <experimental/simd> Add ABI tags, class template simd/simd_mask implementations.
[libcxx] <experimental/simd> Add traits is_abi_tag[_v], is_simd[_v] and is_simd_mask[_v].
[libcxx] <experimental/simd> Add related tests.

[Joy12138]

Rebase

[Joy12138]

Fix rebase error

[Joy12138]

Update test structure with type_algorithms.h

[Joy12138]

try cxx03

[Joy12138]

Move traits to separate headers.

[Joy12138]

Reorder includes

[Joy12138]

Fix CI

[Joy12138]

Fix CI

[Joy12138]

Fix CI

[Joy12138]

Fix C++17

[Joy12138]

@philnik Hi! I have resolved most of the comments and marked them as done. Comments that have not yet been marked may require further discussion.

Do you have any other comments? If not, I will continue to organize and submit the remaining content based on this patch. That may also contribute to the discussion of the overall framework.

By the way, does CI need to be fixed? CI errors do not seem to be introduced by this patch.

[philnik]

In D144362#4277646, @Joy12138 wrote:

@philnik Hi! I have resolved most of the comments and marked them as done. Comments that have not yet been marked may require further discussion.

Do you have any other comments? If not, I will continue to organize and submit the remaining content based on this patch. That may also contribute to the discussion of the overall framework.

By the way, does CI need to be fixed? CI errors do not seem to be introduced by this patch.

The CI problems are unrelated.

libcxx/include/experimental/__simd/declarations.h

15–23 ↗

(On Diff #513524)

There can be a few more newlines throughout.

libcxx/include/experimental/simd

74

Then I'd like a TODO for this, just in case someone else continues the work.

85–93

Moving them into separate headers is for ease of maintenance and avoiding transitively including too many symbols.

96–99

You just specialize the traits in the header where the class is defined. No need to forward-declare anything.

[Joy12138]

libcxx/include/experimental/simd

96–99

Sorry, my previous description was not clear enough. The main issue is that in our design, for more code reuse and more flexible use of internal interfaces, the structure of the external interface layer and internal implementation layer is not consistent. And template specialization does not directly occur on external interfaces such as simd/simd_mask classes.

We have designed four modules, SIMD/MASK storage type and SIMD/MASK operations, for different ABI tags at the implementation layer, which will be used by various external interfaces, including simd/simd_mask, where_expression and non-member functions.

i.e.

// simd
template <class _Tp, class _Abi>
class simd {
  using _Impl    = __simd_operations<_Tp, _Abi>;
  using _Storage = __simd_storage<_Tp, _Abi>;
  
  _Storage __s_;
  
  simd operator+(const simd& __lhs, const simd& __rhs) {
    return _Impl::__plus(__lhs.__s_, __rhs.__s_);
  }
}

// scalar.h
template <class _Tp>
struct __simd_storage<_Tp, simd_abi::__scalar> {
	......
};

template <class _Tp>
struct __simd_operations<_Tp, simd_abi::__scalar> {
	......
};

// vec_ext.h
template <class _Tp, int _Np>
struct __simd_storage<_Tp, simd_abi::__vec_ext<_Np>> {
	......
};

template <class _Tp, int _Np>
struct __simd_operations<_Tp, simd_abi::__vec_ext<_Np>> {
	......
};

Since the specialization does not occur on external interfaces, the external interfaces is now directly placed in the simd header. if the implementation of simd traits is to be placed in a separate header, a forward declaration is required, and if it is placed together with the external interfaces, it will also be placed in the simd header.

Do you have any better suggestions for the current code structure?

[Joy12138]

libcxx/include/experimental/simd

96–99

In addition, most simd traits are platform independent, is it not necessary to specialize for all traits?

[Joy12138]

Add newlines and TODOs.

[Joy12138]

This comment was removed by Joy12138.

[Joy12138]

@philnik Just ping for the above discussion.

[philnik]

libcxx/include/experimental/simd

96–99

I'm a bit confused what exactly you are talking about. Was this meant for a different thread?

[Joy12138]

libcxx/include/experimental/simd

96–99

I'm sorry my description confused you. Maybe I shouldn't have put this content in this thread. I just want to discuss the overall structure and the use of template specialization. And they have some impact on the implementation of simd traits.

What I mainly want to express is that since we do not directly specialize templates on external user interfaces, there will not be directly definitions and implementations of such as
simd<_Tp, __vec_ext<_Np>>. It is basically composed of simd_storage<_Tp, __vec_ext<_Np>> and simd_operations<_Tp, __vec_ext<_Np>>. So we cannot directly define is_simd<simd<_Tp, __vec_ext<_Np>>> without forward-declare of simd class.

[philnik]

LGTM % nits. (and sorry for being so slow in reviewing this)

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

56

57

Couldn't the static_asserts be inlined here? The CheckIsAbiTag* could simply be tag types.

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

36

This doesn't really seem with it given that it already just ex.

[Joy12138]

Fix test

[Joy12138]

@philnik Hi! We rewrite the tests. Please review it again. Thank you!

[philnik]

The updated tests look really nice! Thanks!

You probably have to rebase on top of main to make the CI happy.

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

31–39

clang-format will be happy with this.

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

21–22

This is just integer_types, right?

[Joy12138]

Fix test format

[Joy12138]

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

21–22

No, it is not the same.

The first template parameter of the simd class does not accept input of bool type. And the vector type corresponding to bool type is defined by simd_mask class.

In "type_algorithms.h", integer_types has the following definition:

// libcxx/test/support/type_algorithms.h:98
using integral_types = concatenate_t<character_types, signed_integer_types, unsigned_integer_types, type_list<bool> >;

It contains type bool. And we need arithmetic types without bool to test class simd.

[Joy12138]

I encountered a problem in subsequent development that currently seems to need to be resolved in this patch.

In the previous comment, you suggested that I place all simd traits in a separate header file traits.h. During the process of adding the rest traits implementations, I found that most of them require the use of other interfaces placed in the simd header, similar to is_simd requires the use of simd classes. Therefore, I added declaration.h as forward declarations. However, there are too many interfaces that need to be referenced in the future, which is not suitable to add forward declarations for all.

I think there are two solutions.
One is to keep all external user interfaces under the simd header, just like our previous implementation.
Another is to categorize all external user interfaces into separate header files. No implementations in the simd header and only including other header files in order. Then we may need to add traits.h, simd.h, simd_mask.h, aligned_tag.h, abi_tag.h, simd_casts.h, where_expression.h, etc.
Which one do you prefer?

[philnik]

In D144362#4389779, @Joy12138 wrote:

I encountered a problem in subsequent development that currently seems to need to be resolved in this patch.

In the previous comment, you suggested that I place all simd traits in a separate header file traits.h. During the process of adding the rest traits implementations, I found that most of them require the use of other interfaces placed in the simd header, similar to is_simd requires the use of simd classes. Therefore, I added declaration.h as forward declarations. However, there are too many interfaces that need to be referenced in the future, which is not suitable to add forward declarations for all.

I think there are two solutions.
One is to keep all external user interfaces under the simd header, just like our previous implementation.
Another is to categorize all external user interfaces into separate header files. No implementations in the simd header and only including other header files in order. Then we may need to add traits.h, simd.h, simd_mask.h, aligned_tag.h, abi_tag.h, simd_casts.h, where_expression.h, etc.
Which one do you prefer?

I think it's easier to gollow the code when splitting up the headers, so I'd go for option 2.

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

21–22

You show the implementation of integral_types, not integer_types ;-)

[Joy12138]

Rebase, and reorganize file structure

[Joy12138]

Use integer_types in test_utils.h

[Joy12138]

Fix clang format

[Joy12138]

Fix transitive includes in cxx26

[Joy12138]

Fix order in CMakeList

[Joy12138]

Fix transitive includes in cxx03 and cxx11

[Joy12138]

Fix transitive includes in cxx14

[Joy12138]

Fix transitive includes in cxx23

[Joy12138]

@philnik Hi! Could you please help me check the CI errors?

Last time it prompted me to remove the following statement in transitive includes of cxx23 and cxx26.

*** 174,179 ****

--- 174,180 ----

  experimental/regexregex

  experimental/setexperimental/memory_resource

  experimental/setset

- experimental/simdcstddef

  experimental/stringexperimental/memory_resource

  experimental/stringstring

  experimental/type_traitsinitializer_list



error: command failed with exit status: 1

But this time after I removed, it prompted me to add.

*** 174,179 ****

--- 174,180 ----

  experimental/regexregex

  experimental/setexperimental/memory_resource

  experimental/setset

+ experimental/simdcstddef

  experimental/stringexperimental/memory_resource

  experimental/stringstring

  experimental/type_traitsinitializer_list



error: command failed with exit status: 1

[philnik]

In D144362#4402252, @Joy12138 wrote:

@philnik Hi! Could you please help me check the CI errors?

Last time it prompted me to remove the following statement in transitive includes of cxx23 and cxx26.

*** 174,179 ****

--- 174,180 ----

  experimental/regexregex

  experimental/setexperimental/memory_resource

  experimental/setset

- experimental/simdcstddef

  experimental/stringexperimental/memory_resource

  experimental/stringstring

  experimental/type_traitsinitializer_list



error: command failed with exit status: 1

But this time after I removed, it prompted me to add.

*** 174,179 ****

--- 174,180 ----

  experimental/regexregex

  experimental/setexperimental/memory_resource

  experimental/setset

+ experimental/simdcstddef

  experimental/stringexperimental/memory_resource

  experimental/stringstring

  experimental/type_traitsinitializer_list



error: command failed with exit status: 1

It looks to me like adding it is the correct thing. Do you know which bot didn't like the added line?

[Joy12138]

Add transitive includes in cxx23

[Joy12138]

@philnik I added it again, you can see the current CI errors.

[philnik]

libcxx/include/experimental/simd

61

This check should be done after including the detail headers.