vpx/vpx_ports/arm_cpudetect.c

/*
 *  Copyright (c) 2010 The WebM project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */

#include <stdlib.h>
#include <string.h>
#include "arm.h"

static int arm_cpu_env_flags(int *flags)
{
    char *env;
    env = getenv("VPX_SIMD_CAPS");
    if (env && *env)
    {
        *flags = (int)strtol(env, NULL, 0);
        return 0;
    }
    *flags = 0;
    return -1;
}

static int arm_cpu_env_mask(void)
{
    char *env;
    env = getenv("VPX_SIMD_CAPS_MASK");
    return env && *env ? (int)strtol(env, NULL, 0) : ~0;
}


#if defined(_MSC_VER)
/*For GetExceptionCode() and EXCEPTION_ILLEGAL_INSTRUCTION.*/
#define WIN32_LEAN_AND_MEAN
#define WIN32_EXTRA_LEAN
#include <windows.h>

int arm_cpu_caps(void)
{
    int flags;
    int mask;
    if (!arm_cpu_env_flags(&flags))
    {
        return flags;
    }
    mask = arm_cpu_env_mask();
    /* MSVC has no inline __asm support for ARM, but it does let you __emit
     *  instructions via their assembled hex code.
     * All of these instructions should be essentially nops.
     */
#if defined(HAVE_ARMV5TE)
    if (mask & HAS_EDSP)
    {
        __try
        {
            /*PLD [r13]*/
            __emit(0xF5DDF000);
            flags |= HAS_EDSP;
        }
        __except(GetExceptionCode() == EXCEPTION_ILLEGAL_INSTRUCTION)
        {
            /*Ignore exception.*/
        }
    }
#if defined(HAVE_ARMV6)
    if (mask & HAS_MEDIA)
        __try
        {
            /*SHADD8 r3,r3,r3*/
            __emit(0xE6333F93);
            flags |= HAS_MEDIA;
        }
        __except(GetExceptionCode() == EXCEPTION_ILLEGAL_INSTRUCTION)
        {
            /*Ignore exception.*/
        }
    }
#if defined(HAVE_ARMV7)
    if (mask & HAS_NEON)
    {
        __try
        {
            /*VORR q0,q0,q0*/
            __emit(0xF2200150);
            flags |= HAS_NEON;
        }
        __except(GetExceptionCode() == EXCEPTION_ILLEGAL_INSTRUCTION)
        {
            /*Ignore exception.*/
        }
    }
#endif
#endif
#endif
    return flags & mask;
}

#elif defined(__linux__)
#include <stdio.h>

int arm_cpu_caps(void)
{
    FILE *fin;
    int flags;
    int mask;
    if (!arm_cpu_env_flags(&flags))
    {
        return flags;
    }
    mask = arm_cpu_env_mask();
    /* Reading /proc/self/auxv would be easier, but that doesn't work reliably
     *  on Android.
     * This also means that detection will fail in Scratchbox.
     */
    fin = fopen("/proc/cpuinfo","r");
    if(fin != NULL)
    {
        /* 512 should be enough for anybody (it's even enough for all the flags
         * that x86 has accumulated... so far).
         */
        char buf[512];
        while (fgets(buf, 511, fin) != NULL)
        {
#if defined(HAVE_ARMV5TE) || defined(HAVE_ARMV7)
            if (memcmp(buf, "Features", 8) == 0)
            {
                char *p;
#if defined(HAVE_ARMV5TE)
                p=strstr(buf, " edsp");
                if (p != NULL && (p[5] == ' ' || p[5] == '\n'))
                {
                    flags |= HAS_EDSP;
                }
#if defined(HAVE_ARMV7)
                p = strstr(buf, " neon");
                if (p != NULL && (p[5] == ' ' || p[5] == '\n'))
                {
                    flags |= HAS_NEON;
                }
#endif
#endif
            }
#endif
#if defined(HAVE_ARMV6)
            if (memcmp(buf, "CPU architecture:",17) == 0){
                int version;
                version = atoi(buf+17);
                if (version >= 6)
                {
                    flags |= HAS_MEDIA;
                }
            }
#endif
        }
        fclose(fin);
    }
    return flags & mask;
}

#elif !CONFIG_RUNTIME_CPU_DETECT

int arm_cpu_caps(void)
{
    int flags;
    int mask;
    if (!arm_cpu_env_flags(&flags))
    {
        return flags;
    }
    mask = arm_cpu_env_mask();
#if defined(HAVE_ARMV5TE)
    flags |= HAS_EDSP;
#endif
#if defined(HAVE_ARMV6)
    flags |= HAS_MEDIA;
#endif
#if defined(HAVE_ARMV7)
    flags |= HAS_NEON;
#endif
    return flags & mask;
}

#else
#error "--enable-runtime-cpu-detect selected, but no CPU detection method " \
 "available for your platform. Reconfigure without --enable-runtime-cpu-detect."
#endif