newlib/libm/common/s_llround.c

   1 /* lround adapted to be llround for Newlib, 2009 by Craig Howland.  */
   2 /*
   3  * ====================================================
   4  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   5  *
   6  * Developed at SunPro, a Sun Microsystems, Inc. business.
   7  * Permission to use, copy, modify, and distribute this
   8  * software is freely granted, provided that this notice
   9  * is preserved.
  10  * ====================================================
  11  */
  12
  13 #include "fdlibm.h"
  14
  15 #ifndef _DOUBLE_IS_32BITS
  16
  17 long long int
  18 llround(double x)
  19 {
  20   __int32_t sign, exponent_less_1023;
  21   /* Most significant word, least significant word. */
  22   __uint32_t msw, lsw;
  23   long long int result;
  24
  25   EXTRACT_WORDS(msw, lsw, x);
  26
  27   /* Extract sign. */
  28   sign = ((msw & 0x80000000) ? -1 : 1);
  29   /* Extract exponent field. */
  30   exponent_less_1023 = ((msw & 0x7ff00000) >> 20) - 1023;
  31   msw &= 0x000fffff;
  32   msw |= 0x00100000;
  33
  34   /* exponent_less_1023 in [-1023,1024] */
  35   if (exponent_less_1023 < 20)
  36     {
  37       /* exponent_less_1023 in [-1023,19] */
  38       if (exponent_less_1023 < 0)
  39         {
  40           if (exponent_less_1023 < -1)
  41             return 0;
  42           else
  43             return sign;
  44         }
  45       else
  46         {
  47           /* exponent_less_1023 in [0,19] */
  48           /* shift amt in [0,19] */
  49           msw += 0x80000 >> exponent_less_1023;
  50           /* shift amt in [20,1] */
  51           result = msw >> (20 - exponent_less_1023);
  52         }
  53     }
  54   else if (exponent_less_1023 < (8 * sizeof (long long int)) - 1)
  55     {
  56       /* 64bit longlong: exponent_less_1023 in [20,62] */
  57       if (exponent_less_1023 >= 52)
  58         /* 64bit longlong: exponent_less_1023 in [52,62] */
  59         /* 64bit longlong: shift amt in [32,42] */
  60         result = ((long long int) msw << (exponent_less_1023 - 20))
  61                     /* 64bit longlong: shift amt in [0,10] */
  62                     | (lsw << (exponent_less_1023 - 52));
  63       else
  64         {
  65           /* 64bit longlong: exponent_less_1023 in [20,51] */
  66           unsigned int tmp = lsw
  67                     /* 64bit longlong: shift amt in [0,31] */
  68                     + (0x80000000 >> (exponent_less_1023 - 20));
  69           if (tmp < lsw)
  70             ++msw;
  71           /* 64bit longlong: shift amt in [0,31] */
  72           result = ((long long int) msw << (exponent_less_1023 - 20))
  73                     /* ***64bit longlong: shift amt in [32,1] */
  74                     | SAFE_RIGHT_SHIFT (tmp, (52 - exponent_less_1023));
  75         }
  76     }
  77   else
  78     /* Result is too large to be represented by a long long int. */
  79     return (long long int)x;
  80
  81   return sign * result;
  82 }
  83
  84 #endif /* _DOUBLE_IS_32BITS */