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 #ifdef __STDC__
  33         int __ilogbl(long double x)
  34 #else
  35         int __ilogbl(x)
  36         long double x;
  37 #endif
  38 {
  39         int32_t es,hx,lx,ix;
  40
  41         GET_LDOUBLE_EXP(es,x);
  42         es &= 0x7fff;
  43         if(es==0) {
  44             GET_LDOUBLE_WORDS(es,hx,lx,x);
  45             if((hx|lx)==0)
  46                 return FP_ILOGB0;       /* ilogbl(0) = FP_ILOGB0 */
  47             else                        /* subnormal x */
  48                 if(hx==0) {
  49                     for (ix = -16415; lx>0; lx<<=1) ix -=1;
  50                 } else {
  51                     for (ix = -16383; hx>0; hx<<=1) ix -=1;
  52                 }
  53             return ix;
  54         }
  55         else if (es<0x7fff) return es-0x3fff;
  56         else if (FP_ILOGBNAN != INT_MAX)
  57         {
  58             GET_LDOUBLE_WORDS(es,hx,lx,x);
  59             if (((hx & 0x7fffffff)|lx) == 0)
  60               /* ISO C99 requires ilogbl(+-Inf) == INT_MAX.  */
  61               return INT_MAX;
  62         }
  63         return FP_ILOGBNAN;
  64 }
  65 weak_alias (__ilogbl, ilogbl)