Re: [FFmpeg-devel] [FFmpeg-cvslog] x86/intreadwrite: use intrinsics instead of inline asm for AV_COPY128

[James Almer <jamrial@gmail.com>]

On 7/11/2024 10:08 AM, Martin Storsjö wrote:
> On Wed, 10 Jul 2024, James Almer wrote:
> 
>> ffmpeg | branch: master | James Almer <jamrial@gmail.com> | Wed Jul 10 
>> 13:00:20 2024 -0300| [bd1bcb07e0f29c135103a402d71b343a09ad1690] | 
>> committer: James Almer
>>
>> x86/intreadwrite: use intrinsics instead of inline asm for AV_COPY128
>>
>> This has the benefit of removing any SSE -> AVX penalty that may 
>> happen when
>> the compiler emits VEX encoded instructions.
>>
>> Signed-off-by: James Almer <jamrial@gmail.com>
>>
>>> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=bd1bcb07e0f29c135103a402d71b343a09ad1690
>> ---
>>
>> configure                    |  5 ++++-
>> libavutil/x86/intreadwrite.h | 20 +++++++-------------
>> 2 files changed, 11 insertions(+), 14 deletions(-)
>>
>> diff --git a/configure b/configure
>> index f84fefeaab..7151ed1de3 100755
>> --- a/configure
>> +++ b/configure
>> @@ -2314,6 +2314,7 @@ HEADERS_LIST="
>>
>> INTRINSICS_LIST="
>>     intrinsics_neon
>> +    intrinsics_sse
>>     intrinsics_sse2
>> "
>>
>> @@ -2744,7 +2745,8 @@ armv6t2_deps="arm"
>> armv8_deps="aarch64"
>> neon_deps_any="aarch64 arm"
>> intrinsics_neon_deps="neon"
>> -intrinsics_sse2_deps="sse2"
>> +intrinsics_sse_deps="sse"
>> +intrinsics_sse2_deps="sse2 intrinsics_sse"
>> vfp_deps="arm"
>> vfpv3_deps="vfp"
>> setend_deps="arm"
>> @@ -6446,6 +6448,7 @@ elif enabled loongarch; then
>> fi
>>
>> check_cc intrinsics_neon arm_neon.h "int16x8_t test = vdupq_n_s16(0)"
>> +check_cc intrinsics_sse immintrin.h "__m128 test = _mm_setzero_ps()"
>> check_cc intrinsics_sse2 emmintrin.h "__m128i test = _mm_setzero_si128()"
>>
>> check_ldflags -Wl,--as-needed
>> diff --git a/libavutil/x86/intreadwrite.h b/libavutil/x86/intreadwrite.h
>> index 9bbef00dba..6546eb016c 100644
>> --- a/libavutil/x86/intreadwrite.h
>> +++ b/libavutil/x86/intreadwrite.h
>> @@ -22,29 +22,25 @@
>> #define AVUTIL_X86_INTREADWRITE_H
>>
>> #include <stdint.h>
>> +#if HAVE_INTRINSICS_SSE
>> +#include <immintrin.h>
>> +#endif
> 
> This change seems to have broken builds for x86 with Clang 16 or newer. 
> (Clang 15 and lower seems to be fine.)
> 
> See e.g. 
> http://fate.ffmpeg.org/log.cgi?slot=i686-mingw32-clang-trunk&time=20240711035948&log=compile for an example of the error. The issue is that a clang internal intrinsics header contains "_mm_comige_sh(__m128h A,", i.e. a parameter with the name "A" (which toolchain provided headers shouldn't use). This clashes with libavcodec/huffuyv.h, which has a "#define A 3".
> 
> This is obviously a Clang intrinsics header bug, but we can't fix the 
> existing Clang 16-18 releases that are out there, so I guess what we can 
> do is change our "define A" to something more elaborate. (IIRC there are 
> some similar issues with names with ncurses and/or android headers too.)
> 
> // Martin

We also do "#define A AV_OPT_FLAG_AUDIO_PARAM" in options_table.h and 
probably other places, so changing huffyuv.h may not be enough.
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