sysdeps/libm-ieee754/s_nearbyintf.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 /* Adapted for use as nearbyint by Ulrich Drepper <drepper@cygnus.com>.  */
   5
   6 /*
   7  * ====================================================
   8  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   9  *
  10  * Developed at SunPro, a Sun Microsystems, Inc. business.
  11  * Permission to use, copy, modify, and distribute this
  12  * software is freely granted, provided that this notice
  13  * is preserved.
  14  * ====================================================
  15  */
  16
  17
  18 #include <fenv.h>
  19 #include "math.h"
  20 #include "math_private.h"
  21
  22 #ifdef __STDC__
  23 static const float
  24 #else
  25 static float
  26 #endif
  27 TWO23[2]={
  28   8.3886080000e+06, /* 0x4b000000 */
  29  -8.3886080000e+06, /* 0xcb000000 */
  30 };
  31
  32 #ifdef __STDC__
  33         float __nearbyintf(float x)
  34 #else
  35         float __nearbyintf(x)
  36         float x;
  37 #endif
  38 {
  39         fenv_t env;
  40         int32_t i0,j0,sx;
  41         u_int32_t i,i1;
  42         float w,t;
  43         GET_FLOAT_WORD(i0,x);
  44         sx = (i0>>31)&1;
  45         j0 = ((i0>>23)&0xff)-0x7f;
  46         if(j0<23) {
  47             if(j0<0) {
  48                 if((i0&0x7fffffff)==0) return x;
  49                 i1 = (i0&0x07fffff);
  50                 i0 &= 0xfff00000;
  51                 i0 |= ((i1|-i1)>>9)&0x400000;
  52                 SET_FLOAT_WORD(x,i0);
  53                 feholdexcept (&env);
  54                 w = TWO23[sx]+x;
  55                 t =  w-TWO23[sx];
  56                 fesetenv (&env);
  57                 GET_FLOAT_WORD(i0,t);
  58                 SET_FLOAT_WORD(t,(i0&0x7fffffff)|(sx<<31));
  59                 return t;
  60             } else {
  61                 i = (0x007fffff)>>j0;
  62                 if((i0&i)==0) return x; /* x is integral */
  63                 i>>=1;
  64                 if((i0&i)!=0) i0 = (i0&(~i))|((0x100000)>>j0);
  65             }
  66         } else {
  67             if(j0==0x80) return x+x;    /* inf or NaN */
  68             else return x;              /* x is integral */
  69         }
  70         SET_FLOAT_WORD(x,i0);
  71         feholdexcept (&env);
  72         w = TWO23[sx]+x;
  73         t = w-TWO23[sx];
  74         fesetenv (&env);
  75         return t;
  76 }
  77 weak_alias (__nearbyintf, nearbyintf)