#include <stdio.h>
#include <time.h>
#include <stdlib.h>

__attribute__((noinline))
int cmpa(const unsigned int * x, const unsigned int * y, size_t size)
{
  return __builtin_memcmp(x,y,size);
}

__attribute__((noinline))
int cmpa2(const unsigned int * x, const unsigned int * y, size_t size)
{
  int i = 0;
  size_t s = size / 4;
  while (i < s && x[i] == y[i]) ++i;
  size -= i * 4;
  if (size == 0) return 0;
  unsigned int xx = x[i], yy = y[i];
  asm("bswap %0" : "+r"(xx));
  asm("bswap %0" : "+r"(yy));
  if (size >= 4) {
    return xx < yy ? -1 : 1;
  } else {
    unsigned int dis = 8*(4-size);
    xx >>= dis;
    yy >>= dis;
    return xx - yy;
  }
}

int main()
{
  unsigned int x,y,i;
  int xa[256] = {}, ya[256] = {};
  int s,f;
  clock_t t;

  printf("Memory compare 15 bytes:\n");
  xa[3] = 6;
  t = clock();
  for (i = 0; i != 0x1000000; ++i)
    cmpa(xa, ya, 15);
  s = clock() - t;
  printf("  %d\n", s);
  t = clock();
  for (i = 0; i != 0x1000000; ++i)
    cmpa2(xa, ya, 15);
  f = clock() - t;
  printf("  %d\n",f);
  printf("  Speed up: %f\n", (double)s/f);
  xa[3] = 0;

  printf("Memory compare 16 bytes:\n");
  xa[3] = 6;
  t = clock();
  for (i = 0; i != 0x1000000; ++i)
    cmpa(xa, ya, 16);
  s = clock() - t;
  printf("  %d\n", s);
  t = clock();
  for (i = 0; i != 0x1000000; ++i)
    cmpa2(xa, ya, 16);
  f = clock() - t;
  printf("  %d\n",f);
  printf("  Speed up: %f\n", (double)s/f);
  xa[3] = 0;

  printf("Memory compare 64 bytes:\n");
  xa[15] = 6;
  t = clock();
  for (i = 0; i != 0x1000000; ++i)
    cmpa(xa, ya, 64);
  s = clock() - t;
  printf("  %d\n", s);
  t = clock();
  for (i = 0; i != 0x1000000; ++i)
    cmpa2(xa, ya, 64);
  f = clock() - t;
  printf("  %d\n",f);
  printf("  Speed up: %f\n", (double)s/f);
  xa[15] = 0;

  printf("Memory compare 256 bytes:\n");
  xa[63] = 6;
  t = clock();
  for (i = 0; i != 0x1000000; ++i)
    cmpa(xa, ya, 256);
  s = clock() - t;
  printf("  %d\n", s);
  t = clock();
  for (i = 0; i != 0x1000000; ++i)
    cmpa2(xa, ya, 256);
  f = clock() - t;
  printf("  %d\n",f);
  printf("  Speed up: %f\n", (double)s/f);
}