sysdeps/ieee754/ldbl-96/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) = FP_ILOGB0
  24  * ilogbl(NaN) = FP_ILOGBNAN (no signal is raised)
  25  * ilogbl(+-Inf) = INT_MAX (no signal is raised)
  26  */
  27
  28 #include <limits.h>
  29 #include <math.h>
  30 #include <math_private.h>
  31
  32 int __ilogbl(long double x)
  33 {
  34         int32_t es,hx,lx,ix;
  35
  36         GET_LDOUBLE_EXP(es,x);
  37         es &= 0x7fff;
  38         if(es==0) {
  39             GET_LDOUBLE_WORDS(es,hx,lx,x);
  40             if((hx|lx)==0)
  41                 return FP_ILOGB0;       /* ilogbl(0) = FP_ILOGB0 */
  42             else                        /* subnormal x */
  43                 if(hx==0) {
  44                     for (ix = -16415; lx>0; lx<<=1) ix -=1;
  45                 } else {
  46                     for (ix = -16383; hx>0; hx<<=1) ix -=1;
  47                 }
  48             return ix;
  49         }
  50         else if (es<0x7fff) return es-0x3fff;
  51         else if (FP_ILOGBNAN != INT_MAX)
  52         {
  53             GET_LDOUBLE_WORDS(es,hx,lx,x);
  54             if (((hx & 0x7fffffff)|lx) == 0)
  55               /* ISO C99 requires ilogbl(+-Inf) == INT_MAX.  */
  56               return INT_MAX;
  57         }
  58         return FP_ILOGBNAN;
  59 }
  60 weak_alias (__ilogbl, ilogbl)