libjava/java/lang/s_rint.c

   1
   2 /* @(#)s_rint.c 5.1 93/09/24 */
   3 /*
   4  * ====================================================
   5  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   6  *
   7  * Developed at SunPro, a Sun Microsystems, Inc. business.
   8  * Permission to use, copy, modify, and distribute this
   9  * software is freely granted, provided that this notice
  10  * is preserved.
  11  * ====================================================
  12  */
  13
  14 /*
  15  * rint(x)
  16  * Return x rounded to integral value according to the prevailing
  17  * rounding mode.
  18  * Method:
  19  *      Using floating addition.
  20  * Exception:
  21  *      Inexact flag raised if x not equal to rint(x).
  22  */
  23
  24 #include "fdlibm.h"
  25
  26 #ifndef _DOUBLE_IS_32BITS
  27
  28 #ifdef __STDC__
  29 static const double
  30 #else
  31 static double
  32 #endif
  33 TWO52[2]={
  34   4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
  35  -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
  36 };
  37
  38 #ifdef __STDC__
  39         double rint(double x)
  40 #else
  41         double rint(x)
  42         double x;
  43 #endif
  44 {
  45         int32_t i0,j0,sx;
  46         uint32_t i,i1;
  47         double t;
  48         volatile double w;
  49         EXTRACT_WORDS(i0,i1,x);
  50         sx = (i0>>31)&1;
  51         j0 = ((i0>>20)&0x7ff)-0x3ff;
  52         if(j0<20) {
  53             if(j0<0) {
  54                 if(((i0&0x7fffffff)|i1)==0) return x;
  55                 i1 |= (i0&0x0fffff);
  56                 i0 &= 0xfffe0000;
  57                 i0 |= ((i1|-i1)>>12)&0x80000;
  58                 SET_HIGH_WORD(x,i0);
  59                 w = TWO52[sx]+x;
  60                 t =  w-TWO52[sx];
  61                 GET_HIGH_WORD(i0,t);
  62                 SET_HIGH_WORD(t,(i0&0x7fffffff)|(sx<<31));
  63                 return t;
  64             } else {
  65                 i = (0x000fffff)>>j0;
  66                 if(((i0&i)|i1)==0) return x; /* x is integral */
  67                 i>>=1;
  68                 if(((i0&i)|i1)!=0) {
  69                     if(j0==19) i1 = 0x40000000; else
  70                     i0 = (i0&(~i))|((0x20000)>>j0);
  71                 }
  72             }
  73         } else if (j0>51) {
  74             if(j0==0x400) return x+x;   /* inf or NaN */
  75             else return x;              /* x is integral */
  76         } else {
  77             i = ((uint32_t)(0xffffffff))>>(j0-20);
  78             if((i1&i)==0) return x;     /* x is integral */
  79             i>>=1;
  80             if((i1&i)!=0) i1 = (i1&(~i))|((0x40000000)>>(j0-20));
  81         }
  82         INSERT_WORDS(x,i0,i1);
  83         w = TWO52[sx]+x;
  84         return w-TWO52[sx];
  85 }
  86
  87 #endif /* _DOUBLE_IS_32BITS */