compiler/mlib/s_rintf.c

   1 /* s_rintf.c -- float version of s_rint.c.
   2  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
   3  */
   4
   5 /*
   6  * ====================================================
   7  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   8  *
   9  * Developed at SunPro, a Sun Microsystems, Inc. business.
  10  * Permission to use, copy, modify, and distribute this
  11  * software is freely granted, provided that this notice
  12  * is preserved.
  13  * ====================================================
  14  */
  15
  16 #ifndef lint
  17 static char rcsid[] = "$FreeBSD: src/lib/msun/src/s_rintf.c,v 1.10 2005/12/03 09:00:29 bde Exp $";
  18 #endif
  19
  20 #include "math.h"
  21 #include "math_private.h"
  22
  23 static const float
  24 TWO23[2]={
  25   8.3886080000e+06, /* 0x4b000000 */
  26  -8.3886080000e+06, /* 0xcb000000 */
  27 };
  28
  29 float
  30 rintf(float x)
  31 {
  32         int32_t i0,j0,sx;
  33         volatile float w; /* N.b. - gcc optimises "w" away so use volatile to work around*/
  34         float t;
  35         GET_FLOAT_WORD(i0,x);
  36         sx = (i0>>31)&1;
  37         j0 = ((i0>>23)&0xff)-0x7f;
  38         if(j0<23) {
  39             if(j0<0) {
  40                 if((i0&0x7fffffff)==0) return x;
  41                 w = TWO23[sx]+x;
  42                 t =  w-TWO23[sx];
  43                 GET_FLOAT_WORD(i0,t);
  44                 SET_FLOAT_WORD(t,(i0&0x7fffffff)|(sx<<31));
  45                 return t;
  46         }
  47         w = TWO23[sx]+x;
  48         return w-TWO23[sx];
  49         }
  50         if(j0==0x80) return x+x;        /* inf or NaN */
  51         else return x;                  /* x is integral */
  52 }