sysdeps/ieee754/ldbl-128/s_ilogbl.c

   1 /* s_ilogbl.c -- long double version of s_ilogb.c.
   2  * Conversion to IEEE quad long double by Jakub Jelinek, jj@ultra.linux.cz.
   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: $";
  18 #endif
  19
  20 /* ilogbl(long double x)
  21  * return the binary exponent of non-zero x
  22  * ilogbl(0) = FP_ILOGB0
  23  * ilogbl(NaN) = FP_ILOGBNAN (no signal is raised)
  24  * ilogbl(+-Inf) = INT_MAX (no signal is raised)
  25  */
  26
  27 #include <limits.h>
  28 #include "math.h"
  29 #include "math_private.h"
  30
  31 #ifdef __STDC__
  32         int __ilogbl(long double x)
  33 #else
  34         int __ilogbl(x)
  35         long double x;
  36 #endif
  37 {
  38         int64_t hx,lx;
  39         int ix;
  40
  41         GET_LDOUBLE_WORDS64(hx,lx,x);
  42         hx &= 0x7fffffffffffffffLL;
  43         if(hx <= 0x0001000000000000LL) {
  44             if((hx|lx)==0)
  45                 return FP_ILOGB0;       /* ilogbl(0) = FP_ILOGB0 */
  46             else                        /* subnormal x */
  47                 if(hx==0) {
  48                     for (ix = -16431; lx>0; lx<<=1) ix -=1;
  49                 } else {
  50                     for (ix = -16382, hx<<=15; hx>0; hx<<=1) ix -=1;
  51                 }
  52             return ix;
  53         }
  54         else if (hx<0x7fff000000000000LL) return (hx>>48)-0x3fff;
  55         else if (FP_ILOGBNAN != INT_MAX) {
  56             /* ISO C99 requires ilogbl(+-Inf) == INT_MAX.  */
  57             if (((hx^0x7fff000000000000LL)|lx) == 0)
  58                 return INT_MAX;
  59         }
  60         return FP_ILOGBNAN;
  61 }
  62 weak_alias (__ilogbl, ilogbl)