Re: [PATCH 7/14] [x86_64] Vector math functions (log and tests)

[Andrew Senkevich <andrew dot n dot senkevich at gmail dot com>]

2015-06-10 17:25 GMT+03:00 Andrew Senkevich <andrew.n.senkevich@gmail.com>:
> 2015-06-05 19:40 GMT+03:00 Joseph Myers <joseph@codesourcery.com>:
>> On Fri, 5 Jun 2015, Andrew Senkevich wrote:
>>
>>> 2015-06-04 20:44 GMT+03:00 Joseph Myers <joseph@codesourcery.com>:
>>> > On Thu, 4 Jun 2015, Andrew Senkevich wrote:
>>> >
>>> >> This patch adds vector implementations of log for x86_64 and tests.
>>> >
>>> > I see this patch adds e.g. both _ZGVbN2v_log and _ZGVbN2v___log_finite, as
>>> > aliases.
>>> >
>>> > That's the sort of thing that needs specifically explaining in the patch
>>> > write-up.  In general, it's a bad idea to add extra interfaces to any of
>>> > glibc's shared libraries unless they actually have some sort of semantic
>>> > difference (or unless the interfaces are required to be usable without
>>> > including any headers) - and since all these vector functions are only for
>>> > -ffast-math, I don't think there is any semantic difference in the _finite
>>> > case.
>>> >
>>> > My guess is that this is something to do with interaction of the pragmas
>>> > that cause these functions to be used and the asm redirection of e.g. log
>>> > to __log_finite (for -ffinite-math-only, which is implied by -ffast-math).
>>> > Now, I suppose you do want that redirection to be in effect for calls that
>>> > don't get vectorized.  So I think you should try to work something out in
>>> > the compiler context as a way to say "vector calls should have their names
>>> > based on log not __log_finite, notwithstanding the redirection for scalar
>>> > calls", so we can avoid adding redundant ABIs to libmvec that are never
>>> > going to do anything different from the non-__*_finite ABIs.
>>>
>>> Such aliases were added because GCC generates vector name based on
>>> scalar one already containing _finite redirection.
>>> May be stay only _ZGV*N*v___log_finite symbols?
>>
>> How about having only the non-_finite symbols (which seems cleaner), with
>> top-level __asm__ ("_ZGVbN2v___log_finite = _ZGVbN2v_log") etc. in the
>> headers as a workaround until a conclusion is reached in the compiler
>> context on a cleaner way to base the vector names on something other than
>> the scalar asm name?
>
> Attached patch contains such asm redirections in
> sysdeps/x86/fpu/bits/math-vector.h.
>
> Description and changelog:
>
> Vector log for x86_64 and tests.
>
> Here is implementation of vectorized log containing SSE, AVX,
> AVX2 and AVX512 versions according to Vector ABI
> <https://groups.google.com/forum/#!topic/x86-64-abi/LmppCfN1rZ4>.
>
>         * bits/libm-simd-decl-stubs.h: Added stubs for log.
>         * math/bits/mathcalls.h: Added log declaration with __MATHCALL_VEC.
>         * sysdeps/unix/sysv/linux/x86_64/libmvec.abilist: New versions added.
>         * sysdeps/x86/fpu/bits/math-vector.h: SIMD declaration and asm
>         redirections for log.
>         * sysdeps/x86_64/fpu/Makefile (libmvec-support): Added new files.
>         * sysdeps/x86_64/fpu/Versions: New versions added.
>         * sysdeps/x86_64/fpu/libm-test-ulps: Regenerated.
>         * sysdeps/x86_64/fpu/multiarch/Makefile (libmvec-sysdep_routines): Added
>         build of SSE, AVX2 and AVX512 IFUNC versions.
>         * sysdeps/x86_64/fpu/multiarch/svml_d_log2_core.S: New file.
>         * sysdeps/x86_64/fpu/multiarch/svml_d_log2_core_sse4.S: New file.
>         * sysdeps/x86_64/fpu/multiarch/svml_d_log4_core.S: New file.
>         * sysdeps/x86_64/fpu/multiarch/svml_d_log4_core_avx2.S: New file.
>         * sysdeps/x86_64/fpu/multiarch/svml_d_log8_core.S: New file.
>         * sysdeps/x86_64/fpu/multiarch/svml_d_log8_core_avx512.S: New file.
>         * sysdeps/x86_64/fpu/svml_d_log2_core.S: New file.
>         * sysdeps/x86_64/fpu/svml_d_log4_core.S: New file.
>         * sysdeps/x86_64/fpu/svml_d_log4_core_avx.S: New file.
>         * sysdeps/x86_64/fpu/svml_d_log8_core.S: New file.
>         * sysdeps/x86_64/fpu/svml_d_log_data.S: New file.
>         * sysdeps/x86_64/fpu/svml_d_log_data.h: New file.
>         * sysdeps/x86_64/fpu/test-double-vlen2-wrappers.c: Added
> vector log test.
>         * sysdeps/x86_64/fpu/test-double-vlen2.c: Likewise.
>         * sysdeps/x86_64/fpu/test-double-vlen4-avx2-wrappers.c: Likewise.
>         * sysdeps/x86_64/fpu/test-double-vlen4-avx2.c: Likewise.
>         * sysdeps/x86_64/fpu/test-double-vlen4-wrappers.c: Likewise.
>         * sysdeps/x86_64/fpu/test-double-vlen4.c: Likewise.
>         * sysdeps/x86_64/fpu/test-double-vlen8-wrappers.c: Likewise.
>         * sysdeps/x86_64/fpu/test-double-vlen8.c: Likewise.
>         * NEWS: Mention addition of x86_64 vector log.
>
> Is it ok?

Attached more correct patch.


--
WBR,
Andrew

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