cpu-features.c

/*
 * Copyright (C) 2010 The Android Open Source Project
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *  * Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *  * Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */
 
/* ChangeLog for this library:
 *
 * NDK r10e?: Add MIPS MSA feature.
 *
 * NDK r10: Support for 64-bit CPUs (Intel, ARM & MIPS).
 *
 * NDK r8d: Add android_setCpu().
 *
 * NDK r8c: Add new ARM CPU features: VFPv2, VFP_D32, VFP_FP16,
 *          VFP_FMA, NEON_FMA, IDIV_ARM, IDIV_THUMB2 and iWMMXt.
 *
 *          Rewrite the code to parse /proc/self/auxv instead of
 *          the "Features" field in /proc/cpuinfo.
 *
 *          Dynamically allocate the buffer that hold the content
 *          of /proc/cpuinfo to deal with newer hardware.
 *
 * NDK r7c: Fix CPU count computation. The old method only reported the
 *           number of _active_ CPUs when the library was initialized,
 *           which could be less than the real total.
 *
 * NDK r5: Handle buggy kernels which report a CPU Architecture number of 7
 *         for an ARMv6 CPU (see below).
 *
 *         Handle kernels that only report 'neon', and not 'vfpv3'
 *         (VFPv3 is mandated by the ARM architecture is Neon is implemented)
 *
 *         Handle kernels that only report 'vfpv3d16', and not 'vfpv3'
 *
 *         Fix x86 compilation. Report ANDROID_CPU_FAMILY_X86 in
 *         android_getCpuFamily().
 *
 * NDK r4: Initial release
 */
 
#include "cpu-features.h"
 
#include <dlfcn.h>
#include <errno.h>
#include <fcntl.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/system_properties.h>
#include <unistd.h>
#include <winpr/wtypes.h>
#include <winpr/debug.h>
 
static pthread_once_t g_once;
static int g_inited;
static AndroidCpuFamily g_cpuFamily;
static uint64_t g_cpuFeatures;
static int g_cpuCount;
 
#ifdef __arm__
static uint32_t g_cpuIdArm;
#endif
 
static const int android_cpufeatures_debug = 0;
 
#define D(...)                         \
  do                                 \
  {                                  \
    if (android_cpufeatures_debug) \
    {                              \
      printf(__VA_ARGS__);       \
      fflush(stdout);            \
    }                              \
  } while (0)
 
#ifdef __i386__
static __inline__ void x86_cpuid(int func, int values[4])
{
  int a, b, c, d;
  /* We need to preserve ebx since we're compiling PIC code */
  /* this means we can't use "=b" for the second output register */
  __asm__ __volatile__("push %%ebx\n"
                       "cpuid\n"
                       "mov %%ebx, %1\n"
                       "pop %%ebx\n"
                       : "=a"(a), "=r"(b), "=c"(c), "=d"(d)
                       : "a"(func));
  values[0] = a;
  values[1] = b;
  values[2] = c;
  values[3] = d;
}
#elif defined(__x86_64__)
static __inline__ void x86_cpuid(int func, int values[4])
{
  int64_t a, b, c, d;
  /* We need to preserve ebx since we're compiling PIC code */
  /* this means we can't use "=b" for the second output register */
  __asm__ __volatile__("push %%rbx\n"
                       "cpuid\n"
                       "mov %%rbx, %1\n"
                       "pop %%rbx\n"
                       : "=a"(a), "=r"(b), "=c"(c), "=d"(d)
                       : "a"(func));
  values[0] = a;
  values[1] = b;
  values[2] = c;
  values[3] = d;
}
#endif
 
/* Get the size of a file by reading it until the end. This is needed
 * because files under /proc do not always return a valid size when
 * using fseek(0, SEEK_END) + ftell(). Nor can they be mmap()-ed.
 */
static int get_file_size(const char* pathname)
{
  int fd, result = 0;
  char buffer[256];
  fd = open(pathname, O_RDONLY);
 
  if (fd < 0)
  {
    char ebuffer[256] = { 0 };
    D("Can't open %s: %s\n", pathname, winpr_strerror(errno, ebuffer, sizeof(ebuffer)));
    return -1;
  }
 
  for (;;)
  {
    int ret = read(fd, buffer, sizeof buffer);
 
    if (ret < 0)
    {
      char ebuffer[256] = { 0 };
      if (errno == EINTR)
        continue;
 
      D("Error while reading %s: %s\n", pathname,
        winpr_strerror(errno, ebuffer, sizeof(ebuffer)));
      break;
    }
 
    if (ret == 0)
      break;
 
    result += ret;
  }
 
  close(fd);
  return result;
}
 
/* Read the content of /proc/cpuinfo into a user-provided buffer.
 * Return the length of the data, or -1 on error. Does *not*
 * zero-terminate the content. Will not read more
 * than 'buffsize' bytes.
 */
static int read_file(const char* pathname, char* buffer, size_t buffsize)
{
  int fd, count;
  fd = open(pathname, O_RDONLY);
 
  if (fd < 0)
  {
    char ebuffer[256] = { 0 };
    D("Could not open %s: %s\n", pathname, winpr_strerror(errno, ebuffer, sizeof(ebuffer)));
    return -1;
  }
 
  count = 0;
 
  while (count < (int)buffsize)
  {
    int ret = read(fd, buffer + count, buffsize - count);
 
    if (ret < 0)
    {
      char ebuffer[256] = { 0 };
      if (errno == EINTR)
        continue;
 
      D("Error while reading from %s: %s\n", pathname,
        winpr_strerror(errno, ebuffer, sizeof(ebuffer)));
 
      if (count == 0)
        count = -1;
 
      break;
    }
 
    if (ret == 0)
      break;
 
    count += ret;
  }
 
  close(fd);
  return count;
}
 
#ifdef __arm__
/* Extract the content of a the first occurrence of a given field in
 * the content of /proc/cpuinfo and return it as a heap-allocated
 * string that must be freed by the caller.
 *
 * Return NULL if not found
 */
static char* extract_cpuinfo_field(const char* buffer, int buflen, const char* field)
{
  int fieldlen = strlen(field);
  const char* bufend = buffer + buflen;
  char* result = NULL;
  int len;
  const char *p, *q;
  /* Look for first field occurrence, and ensures it starts the line. */
  p = buffer;
 
  for (;;)
  {
    p = memmem(p, bufend - p, field, fieldlen);
 
    if (p == NULL)
      goto EXIT;
 
    if (p == buffer || p[-1] == '\n')
      break;
 
    p += fieldlen;
  }
 
  /* Skip to the first column followed by a space */
  p += fieldlen;
  p = memchr(p, ':', bufend - p);
 
  if (p == NULL || p[1] != ' ')
    goto EXIT;
 
  /* Find the end of the line */
  p += 2;
  q = memchr(p, '\n', bufend - p);
 
  if (q == NULL)
    q = bufend;
 
  /* Copy the line into a heap-allocated buffer */
  len = q - p;
  result = malloc(len + 1);
 
  if (result == NULL)
    goto EXIT;
 
  memcpy(result, p, len);
  result[len] = '\0';
EXIT:
  return result;
}
 
/* Checks that a space-separated list of items contains one given 'item'.
 * Returns 1 if found, 0 otherwise.
 */
static int has_list_item(const char* list, const char* item)
{
  const char* p = list;
  int itemlen = strlen(item);
 
  if (list == NULL)
    return 0;
 
  while (*p)
  {
    const char* q;
 
    /* skip spaces */
    while (*p == ' ' || *p == '\t')
      p++;
 
    /* find end of current list item */
    q = p;
 
    while (*q && *q != ' ' && *q != '\t')
      q++;
 
    if (itemlen == q - p && !memcmp(p, item, itemlen))
      return 1;
 
    /* skip to next item */
    p = q;
  }
 
  return 0;
}
#endif /* __arm__ */
 
/* Parse a number starting from 'input', but not going further
 * than 'limit'. Return the value into '*result'.
 *
 * NOTE: Does not skip over leading spaces, or deal with sign characters.
 * NOTE: Ignores overflows.
 *
 * The function returns NULL in case of error (bad format), or the new
 * position after the decimal number in case of success (which will always
 * be <= 'limit').
 */
static const char* parse_number(const char* input, const char* limit, int base, int* result)
{
  const char* p = input;
  int val = 0;
 
  while (p < limit)
  {
    int d = (*p - '0');
 
    if ((unsigned)d >= 10U)
    {
      d = (*p - 'a');
 
      if ((unsigned)d >= 6U)
        d = (*p - 'A');
 
      if ((unsigned)d >= 6U)
        break;
 
      d += 10;
    }
 
    if (d >= base)
      break;
 
    val = val * base + d;
    p++;
  }
 
  if (p == input)
    return NULL;
 
  *result = val;
  return p;
}
 
static const char* parse_decimal(const char* input, const char* limit, int* result)
{
  return parse_number(input, limit, 10, result);
}
 
#ifdef __arm__
static const char* parse_hexadecimal(const char* input, const char* limit, int* result)
{
  return parse_number(input, limit, 16, result);
}
#endif /* __arm__ */
 
/* This small data type is used to represent a CPU list / mask, as read
 * from sysfs on Linux. See http://www.kernel.org/doc/Documentation/cputopology.txt
 *
 * For now, we don't expect more than 32 cores on mobile devices, so keep
 * everything simple.
 */
typedef struct
{
  uint32_t mask;
} CpuList;
 
static __inline__ void cpulist_init(CpuList* list)
{
  list->mask = 0;
}
 
static __inline__ void cpulist_and(CpuList* list1, CpuList* list2)
{
  list1->mask &= list2->mask;
}
 
static __inline__ void cpulist_set(CpuList* list, int index)
{
  if ((unsigned)index < 32)
  {
    list->mask |= (uint32_t)(1U << index);
  }
}
 
static __inline__ int cpulist_count(CpuList* list)
{
  return __builtin_popcount(list->mask);
}
 
/* Parse a textual list of cpus and store the result inside a CpuList object.
 * Input format is the following:
 * - comma-separated list of items (no spaces)
 * - each item is either a single decimal number (cpu index), or a range made
 *   of two numbers separated by a single dash (-). Ranges are inclusive.
 *
 * Examples:   0
 *             2,4-127,128-143
 *             0-1
 */
static void cpulist_parse(CpuList* list, const char* line, int line_len)
{
  const char* p = line;
  const char* end = p + line_len;
  const char* q;
 
  /* NOTE: the input line coming from sysfs typically contains a
   * trailing newline, so take care of it in the code below
   */
  while (p < end && *p != '\n')
  {
    int start_value = 0;
    int end_value = 0;
    /* Find the end of current item, and put it into 'q' */
    q = memchr(p, ',', end - p);
 
    if (q == NULL)
    {
      q = end;
    }
 
    /* Get first value */
    p = parse_decimal(p, q, &start_value);
 
    if (p == NULL)
      goto BAD_FORMAT;
 
    end_value = start_value;
 
    /* If we're not at the end of the item, expect a dash and
     * and integer; extract end value.
     */
    if (p < q && *p == '-')
    {
      p = parse_decimal(p + 1, q, &end_value);
 
      if (p == NULL)
        goto BAD_FORMAT;
    }
 
    /* Set bits CPU list bits */
    for (int val = start_value; val <= end_value; val++)
    {
      cpulist_set(list, val);
    }
 
    /* Jump to next item */
    p = q;
 
    if (p < end)
      p++;
  }
 
BAD_FORMAT:;
}
 
/* Read a CPU list from one sysfs file */
static void cpulist_read_from(CpuList* list, const char* filename)
{
  char file[64];
  int filelen;
  cpulist_init(list);
  filelen = read_file(filename, file, sizeof file);
 
  if (filelen < 0)
  {
    char ebuffer[256] = { 0 };
    D("Could not read %s: %s\n", filename, winpr_strerror(errno, ebuffer, sizeof(ebuffer)));
    return;
  }
 
  cpulist_parse(list, file, filelen);
}
#if defined(__aarch64__)
// see <uapi/asm/hwcap.h> kernel header
#define HWCAP_FP (1 << 0)
#define HWCAP_ASIMD (1 << 1)
#define HWCAP_AES (1 << 3)
#define HWCAP_PMULL (1 << 4)
#define HWCAP_SHA1 (1 << 5)
#define HWCAP_SHA2 (1 << 6)
#define HWCAP_CRC32 (1 << 7)
#endif
 
#if defined(__arm__)
 
// See <asm/hwcap.h> kernel header.
#define HWCAP_VFP (1 << 6)
#define HWCAP_IWMMXT (1 << 9)
#define HWCAP_NEON (1 << 12)
#define HWCAP_VFPv3 (1 << 13)
#define HWCAP_VFPv3D16 (1 << 14)
#define HWCAP_VFPv4 (1 << 16)
#define HWCAP_IDIVA (1 << 17)
#define HWCAP_IDIVT (1 << 18)
 
// see <uapi/asm/hwcap.h> kernel header
#define HWCAP2_AES (1 << 0)
#define HWCAP2_PMULL (1 << 1)
#define HWCAP2_SHA1 (1 << 2)
#define HWCAP2_SHA2 (1 << 3)
#define HWCAP2_CRC32 (1 << 4)
 
// This is the list of 32-bit ARMv7 optional features that are _always_
// supported by ARMv8 CPUs, as mandated by the ARM Architecture Reference
// Manual.
#define HWCAP_SET_FOR_ARMV8 \
  (HWCAP_VFP | HWCAP_NEON | HWCAP_VFPv3 | HWCAP_VFPv4 | HWCAP_IDIVA | HWCAP_IDIVT)
#endif
 
#if defined(__mips__)
// see <uapi/asm/hwcap.h> kernel header
#define HWCAP_MIPS_R6 (1 << 0)
#define HWCAP_MIPS_MSA (1 << 1)
#endif
 
#if defined(__arm__) || defined(__aarch64__) || defined(__mips__)
 
#define AT_HWCAP 16
#define AT_HWCAP2 26
 
// Probe the system's C library for a 'getauxval' function and call it if
// it exits, or return 0 for failure. This function is available since API
// level 20.
//
// This code does *NOT* check for '__ANDROID_API__ >= 20' to support the
// edge case where some NDK developers use headers for a platform that is
// newer than the one really targeted by their application.
// This is typically done to use newer native APIs only when running on more
// recent Android versions, and requires careful symbol management.
//
// Note that getauxval() can't really be re-implemented here, because
// its implementation does not parse /proc/self/auxv. Instead it depends
// on values  that are passed by the kernel at process-init time to the
// C runtime initialization layer.
static uint32_t get_elf_hwcap_from_getauxval(int hwcap_type)
{
  typedef unsigned long getauxval_func_t(unsigned long);
  dlerror();
  void* libc_handle = dlopen("libc.so", RTLD_NOW);
 
  if (!libc_handle)
  {
    D("Could not dlopen() C library: %s\n", dlerror());
    return 0;
  }
 
  uint32_t ret = 0;
  getauxval_func_t* func = (getauxval_func_t*)dlsym(libc_handle, "getauxval");
 
  if (!func)
  {
    D("Could not find getauxval() in C library\n");
  }
  else
  {
    // Note: getauxval() returns 0 on failure. Doesn't touch errno.
    ret = (uint32_t)(*func)(hwcap_type);
  }
 
  dlclose(libc_handle);
  return ret;
}
#endif
 
#if defined(__arm__)
// Parse /proc/self/auxv to extract the ELF HW capabilities bitmap for the
// current CPU. Note that this file is not accessible from regular
// application processes on some Android platform releases.
// On success, return new ELF hwcaps, or 0 on failure.
static uint32_t get_elf_hwcap_from_proc_self_auxv(void)
{
  const char filepath[] = "/proc/self/auxv";
  int fd = TEMP_FAILURE_RETRY(open(filepath, O_RDONLY));
 
  if (fd < 0)
  {
    char ebuffer[256] = { 0 };
    D("Could not open %s: %s\n", filepath, winpr_strerror(errno, ebuffer, sizeof(ebuffer)));
    return 0;
  }
 
  struct
  {
    uint32_t tag;
    uint32_t value;
  } entry;
 
  uint32_t result = 0;
 
  for (;;)
  {
    int ret = TEMP_FAILURE_RETRY(read(fd, (char*)&entry, sizeof entry));
 
    if (ret < 0)
    {
      char ebuffer[256] = { 0 };
      D("Error while reading %s: %s\n", filepath,
        winpr_strerror(errno, ebuffer, sizeof(ebuffer)));
      break;
    }
 
    // Detect end of list.
    if (ret == 0 || (entry.tag == 0 && entry.value == 0))
      break;
 
    if (entry.tag == AT_HWCAP)
    {
      result = entry.value;
      break;
    }
  }
 
  close(fd);
  return result;
}
 
/* Compute the ELF HWCAP flags from the content of /proc/cpuinfo.
 * This works by parsing the 'Features' line, which lists which optional
 * features the device's CPU supports, on top of its reference
 * architecture.
 */
static uint32_t get_elf_hwcap_from_proc_cpuinfo(const char* cpuinfo, int cpuinfo_len)
{
  uint32_t hwcaps = 0;
  long architecture = 0;
  char* cpuArch = extract_cpuinfo_field(cpuinfo, cpuinfo_len, "CPU architecture");
 
  if (cpuArch)
  {
    architecture = strtol(cpuArch, NULL, 10);
    free(cpuArch);
 
    if (architecture >= 8L)
    {
      // This is a 32-bit ARM binary running on a 64-bit ARM64 kernel.
      // The 'Features' line only lists the optional features that the
      // device's CPU supports, compared to its reference architecture
      // which are of no use for this process.
      D("Faking 32-bit ARM HWCaps on ARMv%ld CPU\n", architecture);
      return HWCAP_SET_FOR_ARMV8;
    }
  }
 
  char* cpuFeatures = extract_cpuinfo_field(cpuinfo, cpuinfo_len, "Features");
 
  if (cpuFeatures != NULL)
  {
    D("Found cpuFeatures = '%s'\n", cpuFeatures);
 
    if (has_list_item(cpuFeatures, "vfp"))
      hwcaps |= HWCAP_VFP;
 
    if (has_list_item(cpuFeatures, "vfpv3"))
      hwcaps |= HWCAP_VFPv3;
 
    if (has_list_item(cpuFeatures, "vfpv3d16"))
      hwcaps |= HWCAP_VFPv3D16;
 
    if (has_list_item(cpuFeatures, "vfpv4"))
      hwcaps |= HWCAP_VFPv4;
 
    if (has_list_item(cpuFeatures, "neon"))
      hwcaps |= HWCAP_NEON;
 
    if (has_list_item(cpuFeatures, "idiva"))
      hwcaps |= HWCAP_IDIVA;
 
    if (has_list_item(cpuFeatures, "idivt"))
      hwcaps |= HWCAP_IDIVT;
 
    if (has_list_item(cpuFeatures, "idiv"))
      hwcaps |= HWCAP_IDIVA | HWCAP_IDIVT;
 
    if (has_list_item(cpuFeatures, "iwmmxt"))
      hwcaps |= HWCAP_IWMMXT;
 
    free(cpuFeatures);
  }
 
  return hwcaps;
}
#endif /* __arm__ */
 
/* Return the number of cpus present on a given device.
 *
 * To handle all weird kernel configurations, we need to compute the
 * intersection of the 'present' and 'possible' CPU lists and count
 * the result.
 */
static int get_cpu_count(void)
{
  CpuList cpus_present[1];
  CpuList cpus_possible[1];
  cpulist_read_from(cpus_present, "/sys/devices/system/cpu/present");
  cpulist_read_from(cpus_possible, "/sys/devices/system/cpu/possible");
  /* Compute the intersection of both sets to get the actual number of
   * CPU cores that can be used on this device by the kernel.
   */
  cpulist_and(cpus_present, cpus_possible);
  return cpulist_count(cpus_present);
}
 
static void android_cpuInitFamily(void)
{
#if defined(__arm__)
  g_cpuFamily = ANDROID_CPU_FAMILY_ARM;
#elif defined(__i386__)
  g_cpuFamily = ANDROID_CPU_FAMILY_X86;
#elif defined(__mips64)
  /* Needs to be before __mips__ since the compiler defines both */
  g_cpuFamily = ANDROID_CPU_FAMILY_MIPS64;
#elif defined(__mips__)
  g_cpuFamily = ANDROID_CPU_FAMILY_MIPS;
#elif defined(__aarch64__)
  g_cpuFamily = ANDROID_CPU_FAMILY_ARM64;
#elif defined(__x86_64__)
  g_cpuFamily = ANDROID_CPU_FAMILY_X86_64;
#else
  g_cpuFamily = ANDROID_CPU_FAMILY_UNKNOWN;
#endif
}
 
static void android_cpuInit(void)
{
  char* cpuinfo = NULL;
  int cpuinfo_len;
  android_cpuInitFamily();
  g_cpuFeatures = 0;
  g_cpuCount = 1;
  g_inited = 1;
  cpuinfo_len = get_file_size("/proc/cpuinfo");
 
  if (cpuinfo_len < 0)
  {
    D("cpuinfo_len cannot be computed!");
    return;
  }
 
  cpuinfo = malloc(cpuinfo_len);
 
  if (cpuinfo == NULL)
  {
    D("cpuinfo buffer could not be allocated");
    return;
  }
 
  cpuinfo_len = read_file("/proc/cpuinfo", cpuinfo, cpuinfo_len);
  D("cpuinfo_len is (%d):\n%.*s\n", cpuinfo_len, cpuinfo_len >= 0 ? cpuinfo_len : 0, cpuinfo);
 
  if (cpuinfo_len < 0) /* should not happen */
  {
    free(cpuinfo);
    return;
  }
 
  /* Count the CPU cores, the value may be 0 for single-core CPUs */
  g_cpuCount = get_cpu_count();
 
  if (g_cpuCount == 0)
  {
    g_cpuCount = 1;
  }
 
  D("found cpuCount = %d\n", g_cpuCount);
#ifdef __arm__
  {
    /* Extract architecture from the "CPU Architecture" field.
     * The list is well-known, unlike the the output of
     * the 'Processor' field which can vary greatly.
     *
     * See the definition of the 'proc_arch' array in
     * $KERNEL/arch/arm/kernel/setup.c and the 'c_show' function in
     * same file.
     */
    char* cpuArch = extract_cpuinfo_field(cpuinfo, cpuinfo_len, "CPU architecture");
 
    if (cpuArch != NULL)
    {
      char* end;
      long archNumber;
      int hasARMv7 = 0;
      D("found cpuArch = '%s'\n", cpuArch);
      /* read the initial decimal number, ignore the rest */
      archNumber = strtol(cpuArch, &end, 10);
 
      /* Note that ARMv8 is upwards compatible with ARMv7. */
      if (end > cpuArch && archNumber >= 7)
      {
        hasARMv7 = 1;
      }
 
      /* Unfortunately, it seems that certain ARMv6-based CPUs
       * report an incorrect architecture number of 7!
       *
       * See http://code.google.com/p/android/issues/detail?id=10812
       *
       * We try to correct this by looking at the 'elf_format'
       * field reported by the 'Processor' field, which is of the
       * form of "(v7l)" for an ARMv7-based CPU, and "(v6l)" for
       * an ARMv6-one.
       */
      if (hasARMv7)
      {
        char* cpuProc = extract_cpuinfo_field(cpuinfo, cpuinfo_len, "Processor");
 
        if (cpuProc != NULL)
        {
          D("found cpuProc = '%s'\n", cpuProc);
 
          if (has_list_item(cpuProc, "(v6l)"))
          {
            D("CPU processor and architecture mismatch!!\n");
            hasARMv7 = 0;
          }
 
          free(cpuProc);
        }
      }
 
      if (hasARMv7)
      {
        g_cpuFeatures |= ANDROID_CPU_ARM_FEATURE_ARMv7;
      }
 
      /* The LDREX / STREX instructions are available from ARMv6 */
      if (archNumber >= 6)
      {
        g_cpuFeatures |= ANDROID_CPU_ARM_FEATURE_LDREX_STREX;
      }
 
      free(cpuArch);
    }
 
    /* Extract the list of CPU features from ELF hwcaps */
    uint32_t hwcaps = 0;
    hwcaps = get_elf_hwcap_from_getauxval(AT_HWCAP);
 
    if (!hwcaps)
    {
      D("Parsing /proc/self/auxv to extract ELF hwcaps!\n");
      hwcaps = get_elf_hwcap_from_proc_self_auxv();
    }
 
    if (!hwcaps)
    {
      // Parsing /proc/self/auxv will fail from regular application
      // processes on some Android platform versions, when this happens
      // parse proc/cpuinfo instead.
      D("Parsing /proc/cpuinfo to extract ELF hwcaps!\n");
      hwcaps = get_elf_hwcap_from_proc_cpuinfo(cpuinfo, cpuinfo_len);
    }
 
    if (hwcaps != 0)
    {
      int has_vfp = (hwcaps & HWCAP_VFP);
      int has_vfpv3 = (hwcaps & HWCAP_VFPv3);
      int has_vfpv3d16 = (hwcaps & HWCAP_VFPv3D16);
      int has_vfpv4 = (hwcaps & HWCAP_VFPv4);
      int has_neon = (hwcaps & HWCAP_NEON);
      int has_idiva = (hwcaps & HWCAP_IDIVA);
      int has_idivt = (hwcaps & HWCAP_IDIVT);
      int has_iwmmxt = (hwcaps & HWCAP_IWMMXT);
 
      // The kernel does a poor job at ensuring consistency when
      // describing CPU features. So lots of guessing is needed.
 
      // 'vfpv4' implies VFPv3|VFP_FMA|FP16
      if (has_vfpv4)
        g_cpuFeatures |= ANDROID_CPU_ARM_FEATURE_VFPv3 | ANDROID_CPU_ARM_FEATURE_VFP_FP16 |
                         ANDROID_CPU_ARM_FEATURE_VFP_FMA;
 
      // 'vfpv3' or 'vfpv3d16' imply VFPv3. Note that unlike GCC,
      // a value of 'vfpv3' doesn't necessarily mean that the D32
      // feature is present, so be conservative. All CPUs in the
      // field that support D32 also support NEON, so this should
      // not be a problem in practice.
      if (has_vfpv3 || has_vfpv3d16)
        g_cpuFeatures |= ANDROID_CPU_ARM_FEATURE_VFPv3;
 
      // 'vfp' is super ambiguous. Depending on the kernel, it can
      // either mean VFPv2 or VFPv3. Make it depend on ARMv7.
      if (has_vfp)
      {
        if (g_cpuFeatures & ANDROID_CPU_ARM_FEATURE_ARMv7)
          g_cpuFeatures |= ANDROID_CPU_ARM_FEATURE_VFPv3;
        else
          g_cpuFeatures |= ANDROID_CPU_ARM_FEATURE_VFPv2;
      }
 
      // Neon implies VFPv3|D32, and if vfpv4 is detected, NEON_FMA
      if (has_neon)
      {
        g_cpuFeatures |= ANDROID_CPU_ARM_FEATURE_VFPv3 | ANDROID_CPU_ARM_FEATURE_NEON |
                         ANDROID_CPU_ARM_FEATURE_VFP_D32;
 
        if (has_vfpv4)
          g_cpuFeatures |= ANDROID_CPU_ARM_FEATURE_NEON_FMA;
      }
 
      // VFPv3 implies VFPv2 and ARMv7
      if (g_cpuFeatures & ANDROID_CPU_ARM_FEATURE_VFPv3)
        g_cpuFeatures |= ANDROID_CPU_ARM_FEATURE_VFPv2 | ANDROID_CPU_ARM_FEATURE_ARMv7;
 
      if (has_idiva)
        g_cpuFeatures |= ANDROID_CPU_ARM_FEATURE_IDIV_ARM;
 
      if (has_idivt)
        g_cpuFeatures |= ANDROID_CPU_ARM_FEATURE_IDIV_THUMB2;
 
      if (has_iwmmxt)
        g_cpuFeatures |= ANDROID_CPU_ARM_FEATURE_iWMMXt;
    }
 
    /* Extract the list of CPU features from ELF hwcaps2 */
    uint32_t hwcaps2 = 0;
    hwcaps2 = get_elf_hwcap_from_getauxval(AT_HWCAP2);
 
    if (hwcaps2 != 0)
    {
      int has_aes = (hwcaps2 & HWCAP2_AES);
      int has_pmull = (hwcaps2 & HWCAP2_PMULL);
      int has_sha1 = (hwcaps2 & HWCAP2_SHA1);
      int has_sha2 = (hwcaps2 & HWCAP2_SHA2);
      int has_crc32 = (hwcaps2 & HWCAP2_CRC32);
 
      if (has_aes)
        g_cpuFeatures |= ANDROID_CPU_ARM_FEATURE_AES;
 
      if (has_pmull)
        g_cpuFeatures |= ANDROID_CPU_ARM_FEATURE_PMULL;
 
      if (has_sha1)
        g_cpuFeatures |= ANDROID_CPU_ARM_FEATURE_SHA1;
 
      if (has_sha2)
        g_cpuFeatures |= ANDROID_CPU_ARM_FEATURE_SHA2;
 
      if (has_crc32)
        g_cpuFeatures |= ANDROID_CPU_ARM_FEATURE_CRC32;
    }
 
    /* Extract the cpuid value from various fields */
    // The CPUID value is broken up in several entries in /proc/cpuinfo.
    // This table is used to rebuild it from the entries.
    static const struct CpuIdEntry
    {
      const char* field;
      char format;
      char bit_lshift;
      char bit_length;
    } cpu_id_entries[] = {
      { "CPU implementer", 'x', 24, 8 },
      { "CPU variant", 'x', 20, 4 },
      { "CPU part", 'x', 4, 12 },
      { "CPU revision", 'd', 0, 4 },
    };
    D("Parsing /proc/cpuinfo to recover CPUID\n");
 
    for (size_t i = 0; i < sizeof(cpu_id_entries) / sizeof(cpu_id_entries[0]); ++i)
    {
      const struct CpuIdEntry* entry = &cpu_id_entries[i];
      char* value = extract_cpuinfo_field(cpuinfo, cpuinfo_len, entry->field);
 
      if (value == NULL)
        continue;
 
      D("field=%s value='%s'\n", entry->field, value);
      char* value_end = value + strlen(value);
      int val = 0;
      const char* start = value;
      const char* p;
 
      if (value[0] == '0' && (value[1] == 'x' || value[1] == 'X'))
      {
        start += 2;
        p = parse_hexadecimal(start, value_end, &val);
      }
      else if (entry->format == 'x')
        p = parse_hexadecimal(value, value_end, &val);
      else
        p = parse_decimal(value, value_end, &val);
 
      if (p > (const char*)start)
      {
        val &= ((1 << entry->bit_length) - 1);
        val <<= entry->bit_lshift;
        g_cpuIdArm |= (uint32_t)val;
      }
 
      free(value);
    }
 
    // Handle kernel configuration bugs that prevent the correct
    // reporting of CPU features.
    static const struct CpuFix
    {
      uint32_t cpuid;
      uint64_t or_flags;
    } cpu_fixes[] = {
      /* The Nexus 4 (Qualcomm Krait) kernel configuration
       * forgets to report IDIV support. */
      { 0x510006f2, ANDROID_CPU_ARM_FEATURE_IDIV_ARM | ANDROID_CPU_ARM_FEATURE_IDIV_THUMB2 },
      { 0x510006f3, ANDROID_CPU_ARM_FEATURE_IDIV_ARM | ANDROID_CPU_ARM_FEATURE_IDIV_THUMB2 },
    };
 
    for (size_t n = 0; n < sizeof(cpu_fixes) / sizeof(cpu_fixes[0]); ++n)
    {
      const struct CpuFix* entry = &cpu_fixes[n];
 
      if (g_cpuIdArm == entry->cpuid)
        g_cpuFeatures |= entry->or_flags;
    }
 
    // Special case: The emulator-specific Android 4.2 kernel fails
    // to report support for the 32-bit ARM IDIV instruction.
    // Technically, this is a feature of the virtual CPU implemented
    // by the emulator. Note that it could also support Thumb IDIV
    // in the future, and this will have to be slightly updated.
    char* hardware = extract_cpuinfo_field(cpuinfo, cpuinfo_len, "Hardware");
 
    if (hardware)
    {
      if (!strcmp(hardware, "Goldfish") && g_cpuIdArm == 0x4100c080 &&
          (g_cpuFamily & ANDROID_CPU_ARM_FEATURE_ARMv7) != 0)
      {
        g_cpuFeatures |= ANDROID_CPU_ARM_FEATURE_IDIV_ARM;
      }
 
      free(hardware);
    }
  }
#endif /* __arm__ */
#ifdef __aarch64__
  {
    /* Extract the list of CPU features from ELF hwcaps */
    uint32_t hwcaps = 0;
    hwcaps = get_elf_hwcap_from_getauxval(AT_HWCAP);
 
    if (hwcaps != 0)
    {
      int has_fp = (hwcaps & HWCAP_FP);
      int has_asimd = (hwcaps & HWCAP_ASIMD);
      int has_aes = (hwcaps & HWCAP_AES);
      int has_pmull = (hwcaps & HWCAP_PMULL);
      int has_sha1 = (hwcaps & HWCAP_SHA1);
      int has_sha2 = (hwcaps & HWCAP_SHA2);
      int has_crc32 = (hwcaps & HWCAP_CRC32);
 
      if (has_fp == 0)
      {
        D("ERROR: Floating-point unit missing, but is required by Android on AArch64 "
          "CPUs\n");
      }
 
      if (has_asimd == 0)
      {
        D("ERROR: ASIMD unit missing, but is required by Android on AArch64 CPUs\n");
      }
 
      if (has_fp)
        g_cpuFeatures |= ANDROID_CPU_ARM64_FEATURE_FP;
 
      if (has_asimd)
        g_cpuFeatures |= ANDROID_CPU_ARM64_FEATURE_ASIMD;
 
      if (has_aes)
        g_cpuFeatures |= ANDROID_CPU_ARM64_FEATURE_AES;
 
      if (has_pmull)
        g_cpuFeatures |= ANDROID_CPU_ARM64_FEATURE_PMULL;
 
      if (has_sha1)
        g_cpuFeatures |= ANDROID_CPU_ARM64_FEATURE_SHA1;
 
      if (has_sha2)
        g_cpuFeatures |= ANDROID_CPU_ARM64_FEATURE_SHA2;
 
      if (has_crc32)
        g_cpuFeatures |= ANDROID_CPU_ARM64_FEATURE_CRC32;
    }
  }
#endif /* __aarch64__ */
#if defined(__i386__) || defined(__x86_64__)
  int regs[4];
  /* According to http://en.wikipedia.org/wiki/CPUID */
#define VENDOR_INTEL_b 0x756e6547
#define VENDOR_INTEL_c 0x6c65746e
#define VENDOR_INTEL_d 0x49656e69
  x86_cpuid(0, regs);
  int vendorIsIntel =
      (regs[1] == VENDOR_INTEL_b && regs[2] == VENDOR_INTEL_c && regs[3] == VENDOR_INTEL_d);
  x86_cpuid(1, regs);
 
  if ((regs[2] & (1 << 9)) != 0)
  {
    g_cpuFeatures |= ANDROID_CPU_X86_FEATURE_SSSE3;
  }
 
  if ((regs[2] & (1 << 23)) != 0)
  {
    g_cpuFeatures |= ANDROID_CPU_X86_FEATURE_POPCNT;
  }
 
  if ((regs[2] & (1 << 19)) != 0)
  {
    g_cpuFeatures |= ANDROID_CPU_X86_FEATURE_SSE4_1;
  }
 
  if ((regs[2] & (1 << 20)) != 0)
  {
    g_cpuFeatures |= ANDROID_CPU_X86_FEATURE_SSE4_2;
  }
 
  if (vendorIsIntel && (regs[2] & (1 << 22)) != 0)
  {
    g_cpuFeatures |= ANDROID_CPU_X86_FEATURE_MOVBE;
  }
 
  if ((regs[2] & (1 << 25)) != 0)
  {
    g_cpuFeatures |= ANDROID_CPU_X86_FEATURE_AES_NI;
  }
 
  if ((regs[2] & (1 << 28)) != 0)
  {
    g_cpuFeatures |= ANDROID_CPU_X86_FEATURE_AVX;
  }
 
  if ((regs[2] & (1 << 30)) != 0)
  {
    g_cpuFeatures |= ANDROID_CPU_X86_FEATURE_RDRAND;
  }
 
  x86_cpuid(7, regs);
 
  if ((regs[1] & (1 << 5)) != 0)
  {
    g_cpuFeatures |= ANDROID_CPU_X86_FEATURE_AVX2;
  }
 
  if ((regs[1] & (1 << 29)) != 0)
  {
    g_cpuFeatures |= ANDROID_CPU_X86_FEATURE_SHA_NI;
  }
 
#endif
#if defined(__mips__)
  {
    /* MIPS and MIPS64 */
    /* Extract the list of CPU features from ELF hwcaps */
    uint32_t hwcaps = 0;
    hwcaps = get_elf_hwcap_from_getauxval(AT_HWCAP);
 
    if (hwcaps != 0)
    {
      int has_r6 = (hwcaps & HWCAP_MIPS_R6);
      int has_msa = (hwcaps & HWCAP_MIPS_MSA);
 
      if (has_r6)
        g_cpuFeatures |= ANDROID_CPU_MIPS_FEATURE_R6;
 
      if (has_msa)
        g_cpuFeatures |= ANDROID_CPU_MIPS_FEATURE_MSA;
    }
  }
#endif /* __mips__ */
  free(cpuinfo);
}
 
AndroidCpuFamily android_getCpuFamily(void)
{
  pthread_once(&g_once, android_cpuInit);
  return g_cpuFamily;
}
 
uint64_t android_getCpuFeatures(void)
{
  pthread_once(&g_once, android_cpuInit);
  return g_cpuFeatures;
}
 
int android_getCpuCount(void)
{
  pthread_once(&g_once, android_cpuInit);
  return g_cpuCount;
}
 
static void android_cpuInitDummy(void)
{
  g_inited = 1;
}
 
int android_setCpu(int cpu_count, uint64_t cpu_features)
{
  /* Fail if the library was already initialized. */
  if (g_inited)
    return 0;
 
  android_cpuInitFamily();
  g_cpuCount = (cpu_count <= 0 ? 1 : cpu_count);
  g_cpuFeatures = cpu_features;
  pthread_once(&g_once, android_cpuInitDummy);
  return 1;
}
 
#ifdef __arm__
uint32_t android_getCpuIdArm(void)
{
  pthread_once(&g_once, android_cpuInit);
  return g_cpuIdArm;
}
 
int android_setCpuArm(int cpu_count, uint64_t cpu_features, uint32_t cpu_id)
{
  if (!android_setCpu(cpu_count, cpu_features))
    return 0;
 
  g_cpuIdArm = cpu_id;
  return 1;
}
#endif /* __arm__ */
 
/*
 * Technical note: Making sense of ARM's FPU architecture versions.
 *
 * FPA was ARM's first attempt at an FPU architecture. There is no Android
 * device that actually uses it since this technology was already obsolete
 * when the project started. If you see references to FPA instructions
 * somewhere, you can be sure that this doesn't apply to Android at all.
 *
 * FPA was followed by "VFP", soon renamed "VFPv1" due to the emergence of
 * new versions / additions to it. ARM considers this obsolete right now,
 * and no known Android device implements it either.
 *
 * VFPv2 added a few instructions to VFPv1, and is an *optional* extension
 * supported by some ARMv5TE, ARMv6 and ARMv6T2 CPUs. Note that a device
 * supporting the 'armeabi' ABI doesn't necessarily support these.
 *
 * VFPv3-D16 adds a few instructions on top of VFPv2 and is typically used
 * on ARMv7-A CPUs which implement a FPU. Note that it is also mandated
 * by the Android 'armeabi-v7a' ABI. The -D16 suffix in its name means
 * that it provides 16 double-precision FPU registers (d0-d15) and 32
 * single-precision ones (s0-s31) which happen to be mapped to the same
 * register banks.
 *
 * VFPv3-D32 is the name of an extension to VFPv3-D16 that provides 16
 * additional double precision registers (d16-d31). Note that there are
 * still only 32 single precision registers.
 *
 * VFPv3xD is a *subset* of VFPv3-D16 that only provides single-precision
 * registers. It is only used on ARMv7-M (i.e. on micro-controllers) which
 * are not supported by Android. Note that it is not compatible with VFPv2.
 *
 * NOTE: The term 'VFPv3' usually designate either VFPv3-D16 or VFPv3-D32
 *       depending on context. For example GCC uses it for VFPv3-D32, but
 *       the Linux kernel code uses it for VFPv3-D16 (especially in
 *       /proc/cpuinfo). Always try to use the full designation when
 *       possible.
 *
 * NEON, a.k.a. "ARM Advanced SIMD" is an extension that provides
 * instructions to perform parallel computations on vectors of 8, 16,
 * 32, 64 and 128 bit quantities. NEON requires VFPv32-D32 since all
 * NEON registers are also mapped to the same register banks.
 *
 * VFPv4-D16, adds a few instructions on top of VFPv3-D16 in order to
 * perform fused multiply-accumulate on VFP registers, as well as
 * half-precision (16-bit) conversion operations.
 *
 * VFPv4-D32 is VFPv4-D16 with 32, instead of 16, FPU double precision
 * registers.
 *
 * VPFv4-NEON is VFPv4-D32 with NEON instructions. It also adds fused
 * multiply-accumulate instructions that work on the NEON registers.
 *
 * NOTE: Similarly, "VFPv4" might either reference VFPv4-D16 or VFPv4-D32
 *       depending on context.
 *
 * The following information was determined by scanning the binutils-2.22
 * sources:
 *
 * Basic VFP instruction subsets:
 *
 * #define FPU_VFP_EXT_V1xD 0x08000000     // Base VFP instruction set.
 * #define FPU_VFP_EXT_V1   0x04000000     // Double-precision insns.
 * #define FPU_VFP_EXT_V2   0x02000000     // ARM10E VFPr1.
 * #define FPU_VFP_EXT_V3xD 0x01000000     // VFPv3 single-precision.
 * #define FPU_VFP_EXT_V3   0x00800000     // VFPv3 double-precision.
 * #define FPU_NEON_EXT_V1  0x00400000     // Neon (SIMD) insns.
 * #define FPU_VFP_EXT_D32  0x00200000     // Registers D16-D31.
 * #define FPU_VFP_EXT_FP16 0x00100000     // Half-precision extensions.
 * #define FPU_NEON_EXT_FMA 0x00080000     // Neon fused multiply-add
 * #define FPU_VFP_EXT_FMA  0x00040000     // VFP fused multiply-add
 *
 * FPU types (excluding NEON)
 *
 * FPU_VFP_V1xD (EXT_V1xD)
 *    |
 *    +--------------------------+
 *    |                          |
 * FPU_VFP_V1 (+EXT_V1)       FPU_VFP_V3xD (+EXT_V2+EXT_V3xD)
 *    |                          |
 *    |                          |
 * FPU_VFP_V2 (+EXT_V2)       FPU_VFP_V4_SP_D16 (+EXT_FP16+EXT_FMA)
 *    |
 * FPU_VFP_V3D16 (+EXT_Vx3D+EXT_V3)
 *    |
 *    +--------------------------+
 *    |                          |
 * FPU_VFP_V3 (+EXT_D32)     FPU_VFP_V4D16 (+EXT_FP16+EXT_FMA)
 *    |                          |
 *    |                      FPU_VFP_V4 (+EXT_D32)
 *    |
 * FPU_VFP_HARD (+EXT_FMA+NEON_EXT_FMA)
 *
 * VFP architectures:
 *
 * ARCH_VFP_V1xD  (EXT_V1xD)
 *   |
 *   +------------------+
 *   |                  |
 *   |             ARCH_VFP_V3xD (+EXT_V2+EXT_V3xD)
 *   |                  |
 *   |             ARCH_VFP_V3xD_FP16 (+EXT_FP16)
 *   |                  |
 *   |             ARCH_VFP_V4_SP_D16 (+EXT_FMA)
 *   |
 * ARCH_VFP_V1 (+EXT_V1)
 *   |
 * ARCH_VFP_V2 (+EXT_V2)
 *   |
 * ARCH_VFP_V3D16 (+EXT_V3xD+EXT_V3)
 *   |
 *   +-------------------+
 *   |                   |
 *   |         ARCH_VFP_V3D16_FP16  (+EXT_FP16)
 *   |
 *   +-------------------+
 *   |                   |
 *   |         ARCH_VFP_V4_D16 (+EXT_FP16+EXT_FMA)
 *   |                   |
 *   |         ARCH_VFP_V4 (+EXT_D32)
 *   |                   |
 *   |         ARCH_NEON_VFP_V4 (+EXT_NEON+EXT_NEON_FMA)
 *   |
 * ARCH_VFP_V3 (+EXT_D32)
 *   |
 *   +-------------------+
 *   |                   |
 *   |         ARCH_VFP_V3_FP16 (+EXT_FP16)
 *   |
 * ARCH_VFP_V3_PLUS_NEON_V1 (+EXT_NEON)
 *   |
 * ARCH_NEON_FP16 (+EXT_FP16)
 *
 * -fpu=<name> values and their correspondence with FPU architectures above:
 *
 *   {"vfp",               FPU_ARCH_VFP_V2},
 *   {"vfp9",              FPU_ARCH_VFP_V2},
 *   {"vfp3",              FPU_ARCH_VFP_V3}, // For backwards compatibility.
 *   {"vfp10",             FPU_ARCH_VFP_V2},
 *   {"vfp10-r0",          FPU_ARCH_VFP_V1},
 *   {"vfpxd",             FPU_ARCH_VFP_V1xD},
 *   {"vfpv2",             FPU_ARCH_VFP_V2},
 *   {"vfpv3",             FPU_ARCH_VFP_V3},
 *   {"vfpv3-fp16",        FPU_ARCH_VFP_V3_FP16},
 *   {"vfpv3-d16",         FPU_ARCH_VFP_V3D16},
 *   {"vfpv3-d16-fp16",    FPU_ARCH_VFP_V3D16_FP16},
 *   {"vfpv3xd",           FPU_ARCH_VFP_V3xD},
 *   {"vfpv3xd-fp16",      FPU_ARCH_VFP_V3xD_FP16},
 *   {"neon",              FPU_ARCH_VFP_V3_PLUS_NEON_V1},
 *   {"neon-fp16",         FPU_ARCH_NEON_FP16},
 *   {"vfpv4",             FPU_ARCH_VFP_V4},
 *   {"vfpv4-d16",         FPU_ARCH_VFP_V4D16},
 *   {"fpv4-sp-d16",       FPU_ARCH_VFP_V4_SP_D16},
 *   {"neon-vfpv4",        FPU_ARCH_NEON_VFP_V4},
 *
 *
 * Simplified diagram that only includes FPUs supported by Android:
 * Only ARCH_VFP_V3D16 is actually mandated by the armeabi-v7a ABI,
 * all others are optional and must be probed at runtime.
 *
 * ARCH_VFP_V3D16 (EXT_V1xD+EXT_V1+EXT_V2+EXT_V3xD+EXT_V3)
 *   |
 *   +-------------------+
 *   |                   |
 *   |         ARCH_VFP_V3D16_FP16  (+EXT_FP16)
 *   |
 *   +-------------------+
 *   |                   |
 *   |         ARCH_VFP_V4_D16 (+EXT_FP16+EXT_FMA)
 *   |                   |
 *   |         ARCH_VFP_V4 (+EXT_D32)
 *   |                   |
 *   |         ARCH_NEON_VFP_V4 (+EXT_NEON+EXT_NEON_FMA)
 *   |
 * ARCH_VFP_V3 (+EXT_D32)
 *   |
 *   +-------------------+
 *   |                   |
 *   |         ARCH_VFP_V3_FP16 (+EXT_FP16)
 *   |
 * ARCH_VFP_V3_PLUS_NEON_V1 (+EXT_NEON)
 *   |
 * ARCH_NEON_FP16 (+EXT_FP16)
 *
 */