cpu.c

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/*
 * This file is part of FFmpeg.
 *
 * FFmpeg 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.
 *
 * FFmpeg 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 FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */
 
#include "libavutil/cpu.h"
#include "libavutil/cpu_internal.h"
#include "config.h"
 
#if (defined(__linux__) || defined(__ANDROID__)) && HAVE_GETAUXVAL
#include <stdint.h>
#include <sys/auxv.h>
 
#define get_cpu_feature_reg(reg, val) \
        __asm__("mrs %0, " #reg : "=r" (val))
 
static int detect_flags(void)
{
    int flags = 0;
    unsigned long hwcap;
 
    hwcap = getauxval(AT_HWCAP);
 
#if defined(HWCAP_CPUID)
    // We can check for DOTPROD and I8MM using HWCAP_ASIMDDP and
    // HWCAP2_I8MM too, avoiding to read the CPUID registers (which triggers
    // a trap, handled by the kernel). However the HWCAP_* defines for these
    // extensions are added much later than HWCAP_CPUID, so the userland
    // headers might lack support for them even if the binary later is run
    // on hardware that does support it (and where the kernel might support
    // HWCAP_CPUID).
    // See https://www.kernel.org/doc/html/latest/arm64/cpu-feature-registers.html
    if (hwcap & HWCAP_CPUID) {
        uint64_t tmp;
 
        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;
    }
#else
    (void)hwcap;
#endif
 
    return flags;
}
 
#elif defined(__APPLE__) && HAVE_SYSCTLBYNAME
#include <sys/sysctl.h>
 
static int detect_flags(void)
{
    uint32_t value = 0;
    size_t size;
    int flags = 0;
 
    size = sizeof(value);
    if (!sysctlbyname("hw.optional.arm.FEAT_DotProd", &value, &size, NULL, 0)) {
        if (value)
            flags |= AV_CPU_FLAG_DOTPROD;
    }
    size = sizeof(value);
    if (!sysctlbyname("hw.optional.arm.FEAT_I8MM", &value, &size, NULL, 0)) {
        if (value)
            flags |= AV_CPU_FLAG_I8MM;
    }
    return flags;
}
 
#elif defined(_WIN32)
#include <windows.h>
 
static int detect_flags(void)
{
    int flags = 0;
#ifdef PF_ARM_V82_DP_INSTRUCTIONS_AVAILABLE
    if (IsProcessorFeaturePresent(PF_ARM_V82_DP_INSTRUCTIONS_AVAILABLE))
        flags |= AV_CPU_FLAG_DOTPROD;
#endif
    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 |
                AV_CPU_FLAG_NEON  * HAVE_NEON;
 
#ifdef __ARM_FEATURE_DOTPROD
    flags |= AV_CPU_FLAG_DOTPROD;
#endif
#ifdef __ARM_FEATURE_MATMUL_INT8
    flags |= AV_CPU_FLAG_I8MM;
#endif
 
    flags |= detect_flags();
 
    return flags;
}
 
size_t ff_get_cpu_max_align_aarch64(void)
{
    int flags = av_get_cpu_flags();
 
    if (flags & AV_CPU_FLAG_NEON)
        return 16;
 
    return 8;
}