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 1.6 1999/08/28 00:06:54 peter Exp $";
  18 #endif
  19
  20 #include "math.h"
  21 #include "math_private.h"
  22
  23 /*
  24  * TWO23 is double instead of float to avoid a bug in gcc.  Without
  25  * this, gcc thinks that TWO23[sx]+x and w-TWO23[sx] already have float
  26  * precision and doesn't clip them to float precision when they are
  27  * assigned and returned.
  28  */
  29 static const double
  30 TWO23[2]={
  31   8.3886080000e+06, /* 0x4b000000 */
  32  -8.3886080000e+06, /* 0xcb000000 */
  33 };
  34
  35 float
  36 rintf(float x)
  37 {
  38         int32_t i0,j0,sx;
  39         u_int32_t i,i1;
  40         float w,t;
  41         GET_FLOAT_WORD(i0,x);
  42         sx = (i0>>31)&1;
  43         j0 = ((i0>>23)&0xff)-0x7f;
  44         if(j0<23) {
  45             if(j0<0) {
  46                 if((i0&0x7fffffff)==0) return x;
  47                 i1 = (i0&0x07fffff);
  48                 i0 &= 0xfff00000;
  49                 i0 |= ((i1|-i1)>>9)&0x400000;
  50                 SET_FLOAT_WORD(x,i0);
  51                 w = TWO23[sx]+x;
  52                 t =  w-TWO23[sx];
  53                 GET_FLOAT_WORD(i0,t);
  54                 SET_FLOAT_WORD(t,(i0&0x7fffffff)|(sx<<31));
  55                 return t;
  56             } else {
  57                 i = (0x007fffff)>>j0;
  58                 if((i0&i)==0) return x; /* x is integral */
  59                 i>>=1;
  60                 if((i0&i)!=0) i0 = (i0&(~i))|((0x100000)>>j0);
  61             }
  62         } else {
  63             if(j0==0x80) return x+x;    /* inf or NaN */
  64             else return x;              /* x is integral */
  65         }
  66         SET_FLOAT_WORD(x,i0);
  67         w = TWO23[sx]+x;
  68         return w-TWO23[sx];
  69 }