FFmpeg/libavutil/arm/cpu.c

/*
 * This file is part of Libav.
 *
 * Libav is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * Libav is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with Libav; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include "libavutil/cpu.h"
#include "config.h"

#define CORE_FLAG(f) \
    (AV_CPU_FLAG_ ## f * (HAVE_ ## f ## _EXTERNAL || HAVE_ ## f ## _INLINE))

#define CORE_CPU_FLAGS                          \
    (CORE_FLAG(ARMV5TE) |                       \
     CORE_FLAG(ARMV6)   |                       \
     CORE_FLAG(ARMV6T2) |                       \
     CORE_FLAG(VFP)     |                       \
     CORE_FLAG(VFPV3)   |                       \
     CORE_FLAG(NEON))

#if defined __linux__ || defined __ANDROID__

#include <stdint.h>
#include <stdio.h>

#define AT_HWCAP        16

/* Relevant HWCAP values from kernel headers */
#define HWCAP_VFP       (1 << 6)
#define HWCAP_EDSP      (1 << 7)
#define HWCAP_THUMBEE   (1 << 11)
#define HWCAP_NEON      (1 << 12)
#define HWCAP_VFPv3     (1 << 13)
#define HWCAP_TLS       (1 << 15)

static int get_hwcap(uint32_t *hwcap)
{
    struct { uint32_t a_type; uint32_t a_val; } auxv;
    FILE *f = fopen("/proc/self/auxv", "r");
    int err = -1;

    if (!f)
        return -1;

    while (fread(&auxv, sizeof(auxv), 1, f) > 0) {
        if (auxv.a_type == AT_HWCAP) {
            *hwcap = auxv.a_val;
            err = 0;
            break;
        }
    }

    fclose(f);
    return err;
}

int ff_get_cpu_flags_arm(void)
{
    int flags = CORE_CPU_FLAGS;
    uint32_t hwcap;

    if (get_hwcap(&hwcap) < 0)
        return flags;

#define check_cap(cap, flag) do {               \
        if (hwcap & HWCAP_ ## cap)              \
            flags |= AV_CPU_FLAG_ ## flag;      \
    } while (0)

    /* No flags explicitly indicate v6 or v6T2 so check others which
       imply support. */
    check_cap(EDSP,    ARMV5TE);
    check_cap(TLS,     ARMV6);
    check_cap(THUMBEE, ARMV6T2);
    check_cap(VFP,     VFP);
    check_cap(VFPv3,   VFPV3);
    check_cap(NEON,    NEON);

    /* The v6 checks above are not reliable so let higher flags
       trickle down. */
    if (flags & (AV_CPU_FLAG_VFPV3 | AV_CPU_FLAG_NEON))
        flags |= AV_CPU_FLAG_ARMV6T2;
    if (flags & AV_CPU_FLAG_ARMV6T2)
        flags |= AV_CPU_FLAG_ARMV6;

    return flags;
}

#else

int ff_get_cpu_flags_arm(void)
{
    return AV_CPU_FLAG_ARMV5TE * HAVE_ARMV5TE |
           AV_CPU_FLAG_ARMV6   * HAVE_ARMV6   |
           AV_CPU_FLAG_ARMV6T2 * HAVE_ARMV6T2 |
           AV_CPU_FLAG_VFP     * HAVE_VFP     |
           AV_CPU_FLAG_VFPV3   * HAVE_VFPV3   |
           AV_CPU_FLAG_NEON    * HAVE_NEON;
}

#endif