sysdeps/libm-ieee754/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 #if defined(LIBM_SCCS) && !defined(lint)
  17 static char rcsid[] = "$NetBSD: s_logbf.c,v 1.4 1995/05/10 20:47:51 jtc Exp $";
  18 #endif
  19
  20 #include "math.h"
  21 #include "math_private.h"
  22
  23 #ifdef __STDC__
  24         float __logbf(float x)
  25 #else
  26         float __logbf(x)
  27         float x;
  28 #endif
  29 {
  30         int32_t ix;
  31         GET_FLOAT_WORD(ix,x);
  32         ix &= 0x7fffffff;                       /* high |x| */
  33         if(ix==0) return (float)-1.0/fabsf(x);
  34         if(ix>=0x7f800000) return x*x;
  35         if((ix>>=23)==0)                        /* IEEE 754 logb */
  36                 return -126.0;
  37         else
  38                 return (float) (ix-127);
  39 }
  40 weak_alias (__logbf, logbf)