sysdeps/ieee754/ldbl-128ibm/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 #include <math_ldbl_opt.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         int64_t hx,lx;
  40         int ix;
  41
  42         GET_LDOUBLE_WORDS64(hx,lx,x);
  43         hx &= 0x7fffffffffffffffLL;
  44         if(hx <= 0x0010000000000000LL) {
  45             if((hx|(lx&0x7fffffffffffffffLL))==0)
  46                 return FP_ILOGB0;       /* ilogbl(0) = FP_ILOGB0 */
  47             else                        /* subnormal x */
  48                 if(hx==0) {
  49                     for (ix = -1043; lx>0; lx<<=1) ix -=1;
  50                 } else {
  51                     for (ix = -1022, hx<<=11; hx>0; hx<<=1) ix -=1;
  52                 }
  53             return ix;
  54         }
  55         else if (hx<0x7ff0000000000000LL) return (hx>>52)-0x3ff;
  56         else if (FP_ILOGBNAN != INT_MAX) {
  57             /* ISO C99 requires ilogbl(+-Inf) == INT_MAX.  */
  58             if (((hx^0x7ff0000000000000LL)|lx) == 0)
  59                 return INT_MAX;
  60         }
  61         return FP_ILOGBNAN;
  62 }
  63 long_double_symbol (libm, __ilogbl, ilogbl);