compiler/stdc/math/s_logbf.c

   1 /* s_logbf.c -- float version of s_logb.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_logbf.c,v 1.8 2005/12/03 11:57:19 bde Exp $";
  18 #endif
  19
  20 #include "math.h"
  21 #include "math_private.h"
  22
  23 static const float
  24 two25 = 3.355443200e+07;                /* 0x4c000000 */
  25
  26 float
  27 logbf(float x)
  28 {
  29         int32_t ix;
  30         GET_FLOAT_WORD(ix,x);
  31         ix &= 0x7fffffff;                       /* high |x| */
  32         if(ix==0) return (float)-1.0/fabsf(x);
  33         if(ix>=0x7f800000) return x*x;
  34         if(ix<0x00800000) {
  35                 x *= two25;              /* convert subnormal x to normal */
  36                 GET_FLOAT_WORD(ix,x);
  37                 ix &= 0x7fffffff;
  38                 return (float) ((ix>>23)-127-25);
  39         } else
  40                 return (float) ((ix>>23)-127);
  41 }