lib/libm/src/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 #include <sys/cdefs.h>
  17 #if defined(LIBM_SCCS) && !defined(lint)
  18 __RCSID("$NetBSD: s_rintf.c,v 1.9 2008/04/25 22:21:53 christos Exp $");
  19 #endif
  20
  21 #include "math.h"
  22 #include "math_private.h"
  23
  24 static const float
  25 TWO23[2]={
  26   8.3886080000e+06, /* 0x4b000000 */
  27  -8.3886080000e+06, /* 0xcb000000 */
  28 };
  29
  30 float
  31 rintf(float x)
  32 {
  33         int32_t i0,jj0,sx;
  34         u_int32_t i,i1;
  35 #ifdef __i386__ /* XXX gcc4 will omit the rounding otherwise */
  36         volatile
  37 #endif
  38                 float w;
  39         float t;
  40         GET_FLOAT_WORD(i0,x);
  41         sx = (i0>>31)&1;
  42         jj0 = ((i0>>23)&0xff)-0x7f;
  43         if(jj0<23) {
  44             if(jj0<0) {
  45                 if((i0&0x7fffffff)==0) return x;
  46                 i1 = (i0&0x07fffff);
  47                 i0 &= 0xfff00000;
  48                 i0 |= ((i1|-i1)>>9)&0x400000;
  49                 SET_FLOAT_WORD(x,i0);
  50                 w = TWO23[sx]+x;
  51                 t =  w-TWO23[sx];
  52                 GET_FLOAT_WORD(i0,t);
  53                 SET_FLOAT_WORD(t,(i0&0x7fffffff)|(sx<<31));
  54                 return t;
  55             } else {
  56                 i = (0x007fffff)>>jj0;
  57                 if((i0&i)==0) return x; /* x is integral */
  58                 i>>=1;
  59                 if((i0&i)!=0) i0 = (i0&(~i))|((0x100000)>>jj0);
  60             }
  61         } else {
  62             if(jj0==0x80) return x+x;   /* inf or NaN */
  63             else return x;              /* x is integral */
  64         }
  65         SET_FLOAT_WORD(x,i0);
  66         w = TWO23[sx]+x;
  67         return w-TWO23[sx];
  68 }