Re: [FFmpeg-devel] [PATCH] aarch64: Add OpenBSD runtime detection of dotprod and i8mm using sysctl

["Martin Storsjö" <martin@martin.st>]

On Sat, 22 Jun 2024, Brad Smith wrote:

> [PATCH] aarch64: Add OpenBSD runtime detection of dotprod and i8mm using sysctl
>
> Signed-off-by: Brad Smith <brad@comstyle.com>
> ---
> libavutil/aarch64/cpu.c | 35 +++++++++++++++++++++++++++++++++++
> 1 file changed, 35 insertions(+)
>
> diff --git a/libavutil/aarch64/cpu.c b/libavutil/aarch64/cpu.c
> index 196bdaf6b0..40fcc8d1ff 100644
> --- a/libavutil/aarch64/cpu.c
> +++ b/libavutil/aarch64/cpu.c
> @@ -65,6 +65,41 @@ static int detect_flags(void)
>     return flags;
> }
>
> +#elif defined(__OpenBSD__)
> +#include <machine/armreg.h>
> +#include <machine/cpu.h>
> +#include <sys/types.h>
> +#include <sys/sysctl.h>
> +
> +static int detect_flags(void)
> +{
> +    int flags = 0;
> +    int mib[2];
> +    uint64_t isar0;
> +    uint64_t isar1;
> +    size_t len;
> +
> +    mib[0] = CTL_MACHDEP;
> +    mib[1] = CPU_ID_AA64ISAR0;
> +    len = sizeof(isar0);
> +    if (sysctl(mib, 2, &isar0, &len, NULL, 0) != -1) {
> +        if (ID_AA64ISAR0_DP(isar0) >= ID_AA64ISAR0_DP_IMPL)
> +            flags |= AV_CPU_FLAG_DOTPROD;
> +    }
> +
> +    mib[0] = CTL_MACHDEP;
> +    mib[1] = CPU_ID_AA64ISAR1;
> +    len = sizeof(isar1);
> +    if (sysctl(mib, 2, &isar1, &len, NULL, 0) != -1) {
> +#ifdef ID_AA64ISAR1_I8MM_IMPL
> +        if (ID_AA64ISAR1_I8MM(isar1) >= ID_AA64ISAR1_I8MM_IMPL)
> +            flags |= AV_CPU_FLAG_I8MM;
> +#endif
> +    }
> +
> +    return flags;
> +}
> +
> #elif defined(_WIN32)
> #include <windows.h>

This LGTM. Although, in 
https://code.videolan.org/videolan/dav1d/-/merge_requests/1673 you wrapped 
most of this in an #ifdef CPU_ID_AA64ISAR0, so would that be useful here 
too?

Feel free to push either with or without that.

// Martin

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