[FFmpeg-devel] [PATCH 05/11] avcodec: add stride alignment needed for AVX-512

[James Almer]

On 11/9/2017 8:58 AM, James Darnley wrote:
> ---
>  configure             | 2 ++
>  libavcodec/internal.h | 4 +++-
>  2 files changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/configure b/configure
> index 146a87324c..fce8030d91 100755
> --- a/configure
> +++ b/configure
> @@ -1886,6 +1886,7 @@ ARCH_FEATURES="
>      local_aligned
>      simd_align_16
>      simd_align_32
> +    simd_align_64
>  "
>  
>  BUILTIN_LIST="
> @@ -2385,6 +2386,7 @@ fast_clz_if_any="aarch64 alpha avr32 mips ppc x86"
>  fast_unaligned_if_any="aarch64 ppc x86"
>  simd_align_16_if_any="altivec neon sse"
>  simd_align_32_if_any="avx"
> +simd_align_64_if_any="avx512"
>  
>  # system capabilities
>  symver_if_any="symver_asm_label symver_gnu_asm"
> diff --git a/libavcodec/internal.h b/libavcodec/internal.h
> index 7748f09f54..84070431ed 100644
> --- a/libavcodec/internal.h
> +++ b/libavcodec/internal.h
> @@ -87,7 +87,9 @@
>  
>  #define FF_SIGNBIT(x) ((x) >> CHAR_BIT * sizeof(x) - 1)
>  
> -#if HAVE_SIMD_ALIGN_32
> +#if HAVE_SIMD_ALIGN_64
> +#   define STRIDE_ALIGN 64 /* AVX-512 */
> +#elif HAVE_SIMD_ALIGN_32
>  #   define STRIDE_ALIGN 32
>  #elif HAVE_SIMD_ALIGN_16
>  #   define STRIDE_ALIGN 16
> 

LGTM, but I'd really like to find a way to start using
av_get_cpu_max_align() as it was meant to be done when it was
introduced, instead of keeping hardcoding alignment based on configure
time options.

Maybe adding a line to the av_force_cpu_flags() and
av_set_cpu_flags_mask() doxy stating you should reinit all your decoder
and encoder contexts after calling them or similar.