sysdeps/libm-ieee754/s_ilogbl.c

   1 /* s_ilogbl.c -- long double version of s_ilogb.c.
   2  * Conversion to long double by Ulrich Drepper,
   3  * Cygnus Support, drepper@cygnus.com.
   4  */
   5
   6 /*
   7  * ====================================================
   8  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   9  *
  10  * Developed at SunPro, a Sun Microsystems, Inc. business.
  11  * Permission to use, copy, modify, and distribute this
  12  * software is freely granted, provided that this notice
  13  * is preserved.
  14  * ====================================================
  15  */
  16
  17 #if defined(LIBM_SCCS) && !defined(lint)
  18 static char rcsid[] = "$NetBSD: $";
  19 #endif
  20
  21 /* ilogbl(long double x)
  22  * return the binary exponent of non-zero x
  23  * ilogbl(0) = 0x80000001
  24  * ilogbl(inf/NaN) = 0x7fffffff (no signal is raised)
  25  */
  26
  27 #include "math.h"
  28 #include "math_private.h"
  29
  30 #ifdef __STDC__
  31         int __ilogbl(long double x)
  32 #else
  33         int __ilogbl(x)
  34         long double x;
  35 #endif
  36 {
  37         int32_t es,hx,lx,ix;
  38
  39         GET_LDOUBLE_EXP(es,x);
  40         es &= 0x7fff;
  41         if(es==0) {
  42             GET_LDOUBLE_WORDS(es,hx,lx,x);
  43             if((hx|lx)==0)
  44                 return 0x80000001;      /* ilogbl(0) = 0x80000001 */
  45             else                        /* subnormal x */
  46                 if(hx==0) {
  47                     for (ix = -16415; lx>0; lx<<=1) ix -=1;
  48                 } else {
  49                     for (ix = -16383; hx>0; hx<<=1) ix -=1;
  50                 }
  51             return ix;
  52         }
  53         else if (es<0x7fff) return es-0x3fff;
  54         else return 0x7fffffff;
  55 }
  56 weak_alias (__ilogbl, ilogbl)