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

[Brad Smith <brad-at-comstyle.com@ffmpeg.org>]

On 2024-06-24 4:15 a.m., Martin Storsjö wrote:
> 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?


That would be a good idea. I will do the same. Thanks.

> Feel free to push either with or without that.
>
> // Martin
>
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