Le perjantaina 26. toukokuuta 2023, 11.03.14 EEST Martin Storsjö a écrit :
> Based on code by Janne Grunau.
>
> Using HWCAP_CPUID for user space access to the CPU feature registers. See
> https://www.kernel.org/doc/html/latest/arm64/cpu-feature-registers.html.
> ---
> configure | 2 ++
> libavutil/aarch64/cpu.c | 38 ++++++++++++++++++++++++++++++++++++++
> 2 files changed, 40 insertions(+)
>
> diff --git a/configure b/configure
> index 3c7473efb2..b5357b8d27 100755
> --- a/configure
> +++ b/configure
> @@ -2207,6 +2207,7 @@ HAVE_LIST_PUB="
>
> HEADERS_LIST="
> arpa_inet_h
> + asm_hwcap_h
> asm_types_h
> cdio_paranoia_h
> cdio_paranoia_paranoia_h
> @@ -6422,6 +6423,7 @@ check_headers io.h
> enabled libdrm &&
> check_headers linux/dma-buf.h
>
> +check_headers asm/hwcap.h
> check_headers linux/perf_event.h
> check_headers libcrystalhd/libcrystalhd_if.h
> check_headers malloc.h
> diff --git a/libavutil/aarch64/cpu.c b/libavutil/aarch64/cpu.c
> index 42b33e4a2d..34c838c2f5 100644
> --- a/libavutil/aarch64/cpu.c
> +++ b/libavutil/aarch64/cpu.c
> @@ -20,6 +20,42 @@
> #include "libavutil/cpu_internal.h"
> #include "config.h"
>
> +#if (defined(__linux__) || defined(__ANDROID__)) && HAVE_GETAUXVAL &&
> HAVE_ASM_HWCAP_H +#include <stdint.h>
> +#include <asm/hwcap.h>
> +#include <sys/auxv.h>
> +
> +#define get_cpu_feature_reg(reg, val) \
> + __asm__("mrs %0, " #reg : "=r" (val))
Strictly speaking, this can read any system register. One way to prevent that
would be to include the ID_ prefix and _EL1 suffix in the macro. I would have
used a pure static inline instead, but that's just a matter of taste.
> +
> +static int detect_flags(void)
> +{
> + unsigned long ret = getauxval(AT_HWCAP);
> + int flags = 0;
> +#if defined(HWCAP_CPUID)
> + uint64_t tmp;
> + if (!(ret & HWCAP_CPUID))
> + return flags;
> + get_cpu_feature_reg(ID_AA64ISAR0_EL1, tmp);
> + if (((tmp >> 44) & 0xf) == 0x1)
> + flags |= AV_CPU_FLAG_DOTPROD;
> + get_cpu_feature_reg(ID_AA64ISAR1_EL1, tmp);
> + if (((tmp >> 52) & 0xf) == 0x1)
> + flags |= AV_CPU_FLAG_I8MM;
> +#endif
NEON detection could be added here, though I've yet to see an Armv8
implementation without AdvSIMD.
FWIW, DotProd is exposed as HWCAP_ASIMDDP and I8MM is exposed via HWCAP2_I8MM,
using trapped ID registers is not (yet) necessary.
> +
> + return flags;
> +}
> +
> +#else
> +
> +static int detect_flags(void)
> +{
> + return 0;
> +}
> +
> +#endif
> +
> int ff_get_cpu_flags_aarch64(void)
> {
> int flags = AV_CPU_FLAG_ARMV8 * HAVE_ARMV8 |
> @@ -33,6 +69,8 @@ int ff_get_cpu_flags_aarch64(void)
> flags |= AV_CPU_FLAG_I8MM;
> #endif
>
> + flags |= detect_flags();
> +
> return flags;
> }
--
レミ・デニ-クールモン
http://www.remlab.net/
_______________________________________________
ffmpeg-devel mailing list
ffmpeg-devel@ffmpeg.org
https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
To unsubscribe, visit link above, or email
ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
