sysdeps/libm-ieee754/s_ilogbf.c

   1 /* s_ilogbf.c -- float version of s_ilogb.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_ilogbf.c,v 1.4 1995/05/10 20:47:31 jtc Exp $";
  18 #endif
  19
  20 #include "math.h"
  21 #include "math_private.h"
  22
  23 #ifdef __STDC__
  24         int __ilogbf(float x)
  25 #else
  26         int __ilogbf(x)
  27         float x;
  28 #endif
  29 {
  30         int32_t hx,ix;
  31
  32         GET_FLOAT_WORD(hx,x);
  33         hx &= 0x7fffffff;
  34         if(hx<0x00800000) {
  35             if(hx==0)
  36                 return FP_ILOGB0;       /* ilogb(0) = FP_ILOGB0 */
  37             else                        /* subnormal x */
  38                 for (ix = -126,hx<<=8; hx>0; hx<<=1) ix -=1;
  39             return ix;
  40         }
  41         else if (hx<0x7f800000) return (hx>>23)-127;
  42         else return FP_ILOGBNAN;
  43 }
  44 weak_alias (__ilogbf, ilogbf)