조금더빠른형변환사용

~cpp 
// 테스트

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

#ifndef _WIN32
/* for linux/unix */
#include <time.h>
#include <sys/time.h>
static void printf_localtime()
{
   struct tm * ttt;
   struct timeval tv;
   gettimeofday(&tv, NULL);
   ttt = localtime(&tv);

   printf("%.4d-%.2d-%.2d  %.2d:%.2d:%.2d.%.3d", ttt->tm_year, ttt->tm_mon, ttt->tm_mday, ttt->tm_hour, ttt->tm_min, ttt->tm_sec, tv.tv_usec/1000);
}

static unsigned int get_clock()
{
        struct timeval tv;
        unsigned int t;

        gettimeofday(&tv, NULL);

        t = ((tv.tv_sec % 1000000) * 1000) + (tv.tv_usec / 1000);

        return t;
}

#else
/* for windows */
#define get_clock   clock
#endif

#ifdef __BIGENDIAN__
#   define FTOI_LONG reserved, l
#else
#   define FTOI_LONG l
#endif
#define USE_FTOI union{ double r; struct { long FTOI_LONG; } l; } __ftoitmp;
#define OP_FTOI(val) \
 ( ( (__ftoitmp.r=(val)+((((65536.*65536.*16.)+(65536.*.5))*65536.)) ), \
     __ftoitmp.l.l-0x80000000L ) )

#define USE_FTOI2 union{ double r; struct { long FTOI_LONG; } l; } __ftoitmp;

#define LOOPCNT1   10
#define LOOPCNT2   10000000

void conv1(double *dv, long *lv)
{
   *lv = *dv;
}

void test1()
{
   double dval = 123456789.12345678;
   long lval = 0;
   long total = 0;
   long start = 0, finish = 0;
   long avg = 0;
   long i=0, j=0;

   start = get_clock();
   for(j=0; j<LOOPCNT1; j++) {
      for(i=0; i<LOOPCNT2; i++) {
         conv1(&dval, &lval);
      }
   }
   finish = get_clock();
   total = finish - start;
   avg = total / LOOPCNT1 / LOOPCNT2;

   printf("1.... value %ld total %ld ms, avg %ld ms\n", lval, total, avg);
}

void conv2(double *dv, long *lv)
{
   USE_FTOI
   *lv = OP_FTOI(*dv);
}

void test2()
{
   double dval = 123456789.12345678;
   long lval = 0;
   long total = 0;
   long start = 0, finish = 0;
   long avg = 0;
   long i=0, j=0;

   start = get_clock();
   for(j=0; j<LOOPCNT1; j++) {
      for(i=0; i<LOOPCNT2; i++) {
         conv2(&dval, &lval);
      }
   }
   finish = get_clock();
   total = finish - start;
   avg = total / LOOPCNT1 / LOOPCNT2;

   printf("2.... value %ld total %ld ms, avg %ld ms\n", lval, total, avg);
}

void conv3(double *dv, long *lv)
{
   register USE_FTOI
   *lv = OP_FTOI(*dv);
}

void test3()
{
   double dval = 123456789.12345678;
   long lval = 0;
   long total = 0;
   long start = 0, finish = 0;
   long avg = 0;
   long i=0, j=0;

   start = get_clock();
   for(j=0; j<LOOPCNT1; j++) {
      for(i=0; i<LOOPCNT2; i++) {
         conv3(&dval, &lval);
      }
   }
   finish = get_clock();
   total = finish - start;
   avg = total / LOOPCNT1 / LOOPCNT2;

   printf("3.... value %ld total %ld ms, avg %ld ms\n", lval, total, avg);
}

int main(int argc, char *argv[])
{
   test1();
   test2();
   test3();

   return 0;
}

~cpp 
// 결과값

-O0
1.... value 123456789 total 1750 ms, avg 0 ms
2.... value 123456789 total 921 ms, avg 0 ms
3.... value 123456789 total 1579 ms, avg 0 ms

-O1
1.... value 123456789 total 1671 ms, avg 0 ms
2.... value 123456789 total 829 ms, avg 0 ms
3.... value 123456789 total 828 ms, avg 0 ms

-O2
1.... value 123456789 total 1656 ms, avg 0 ms
2.... value 123456789 total 1047 ms, avg 0 ms
3.... value 123456789 total 1031 ms, avg 0 ms

-O3
1.... value 123456789 total 62 ms, avg 0 ms
2.... value 123456789 total 203 ms, avg 0 ms
3.... value 123456789 total 188 ms, avg 0 ms