Re: [FFmpeg-devel] [PATCH v2] arm: Check the build time constants in av_clip_*intp2

["Martin Storsjö" <martin@martin.st>]

On Fri, 26 Aug 2022, Martin Storsjö wrote:

> This fixes building for arm targets with optimizations disabled.
> ---
> libavutil/arm/intmath.h | 24 ++++++++++++++++++------
> 1 file changed, 18 insertions(+), 6 deletions(-)
>
> diff --git a/libavutil/arm/intmath.h b/libavutil/arm/intmath.h
> index 5311a7d52b..f19b21e98d 100644
> --- a/libavutil/arm/intmath.h
> +++ b/libavutil/arm/intmath.h
> @@ -65,17 +65,29 @@ static av_always_inline av_const int av_clip_int16_arm(int a)
> #define av_clip_intp2 av_clip_intp2_arm
> static av_always_inline av_const int av_clip_intp2_arm(int a, int p)
> {
> -    unsigned x;
> -    __asm__ ("ssat %0, %2, %1" : "=r"(x) : "r"(a), "i"(p+1));
> -    return x;
> +    if (av_builtin_constant_p(p)) {
> +        unsigned x;
> +        __asm__ ("ssat %0, %2, %1" : "=r"(x) : "r"(a), "i"(p+1));
> +        return x;
> +    } else {
> +        if (((unsigned)a + (1 << p)) & ~((2 << p) - 1))
> +            return (a >> 31) ^ ((1 << p) - 1);
> +        else
> +            return a;
> +    }
> }
>
> #define av_clip_uintp2 av_clip_uintp2_arm
> static av_always_inline av_const unsigned av_clip_uintp2_arm(int a, int p)
> {
> -    unsigned x;
> -    __asm__ ("usat %0, %2, %1" : "=r"(x) : "r"(a), "i"(p));
> -    return x;
> +    if (av_builtin_constant_p(p)) {
> +        unsigned x;
> +        __asm__ ("usat %0, %2, %1" : "=r"(x) : "r"(a), "i"(p));
> +        return x;
> +    } else {
> +        if (a & ~((1<<p) - 1)) return (~a) >> 31 & ((1<<p) - 1);
> +        else                   return  a;
> +    }
> }
>
> #define av_sat_add32 av_sat_add32_arm
> -- 
> 2.25.1

OK'd by James on irc, will push later today.

// Martin
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