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

["Martin Storsjö" <martin@martin.st>]

On Thu, 11 Jul 2024, Martin Storsjö wrote:

> On Thu, 11 Jul 2024, James Almer wrote:
>
>> 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.
>
> That's quite possible, but those cases may be including intreadwrite.h 
> before that, do it's possible it might not trigger there.
>
> I'll see how many places need to be changed here.

huffyuvenc.c seems to be the only file that runs into the issue; it 
includes put_bits.h (which brings in libavutil/intreadwrite.h) after 
huffyuv.h.

// Martin
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