[FFmpeg-devel] [PATCH] get_cabac_inline_x86: Don't inline the assembly function on 32 bit

[Martin Storsjö]

On Tue, 28 Mar 2023, Martin Storsjö wrote:

> From: Christopher Degawa <ccom at randomderp.com>
>
> While the inline cabac assembly has worked correctly in i386 builds
> historically, modern compiler updates has started showing issues
> with it, when the function gets inlined into larger contexts that
> fail to provide the amount of free registers as this function
> requires.
>
> This was an issue with Clang on Windows on i386, which was fixed
> in c6d284b945324a7bc70ea8b9056040c8148aa835. However, recently
> the same issues also have started showing up with GCC (both for
> Windows and Linux). Whether the issue appears seems dependent on
> a lot of optimizer tuning (e.g. the issue appears or goes away
> depenent on the combinaton of -march= and -mtune= options),
> potentially due to the compiler making different decisions on
> how much to inline.
>
> Fixes: https://trac.ffmpeg.org/ticket/8903
>
> Signed-off-by: Martin Storsjö <martin at martin.st>
> ---
> libavcodec/x86/cabac.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/libavcodec/x86/cabac.h b/libavcodec/x86/cabac.h
> index b046a56a6b..ce2aefcbac 100644
> --- a/libavcodec/x86/cabac.h
> +++ b/libavcodec/x86/cabac.h
> @@ -178,7 +178,7 @@
> #if HAVE_7REGS && !BROKEN_COMPILER
> #define get_cabac_inline get_cabac_inline_x86
> static
> -#if defined(_WIN32) && !defined(_WIN64) && defined(__clang__)
> +#if ARCH_X86_32
> av_noinline
> #else
> av_always_inline
> -- 
> 2.37.1 (Apple Git-137.1)

Will push this today if there's no objections.

// Martin