sysdeps/ieee754/ldbl-128/e_ilogbl.c

   1 /* s_ilogbl.c -- long double version of s_ilogb.c.
   2  */
   3
   4 /*
   5  * ====================================================
   6  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   7  *
   8  * Developed at SunPro, a Sun Microsystems, Inc. business.
   9  * Permission to use, copy, modify, and distribute this
  10  * software is freely granted, provided that this notice
  11  * is preserved.
  12  * ====================================================
  13  */
  14
  15 #if defined(LIBM_SCCS) && !defined(lint)
  16 static char rcsid[] = "$NetBSD: $";
  17 #endif
  18
  19 /* ilogbl(long double x)
  20  * return the binary exponent of non-zero x
  21  * ilogbl(0) = FP_ILOGB0
  22  * ilogbl(NaN) = FP_ILOGBNAN (no signal is raised)
  23  * ilogbl(+-Inf) = INT_MAX (no signal is raised)
  24  */
  25
  26 #include <limits.h>
  27 #include <math.h>
  28 #include <math_private.h>
  29
  30 int __ieee754_ilogbl (_Float128 x)
  31 {
  32         int64_t hx,lx;
  33         int ix;
  34
  35         GET_LDOUBLE_WORDS64(hx,lx,x);
  36         hx &= 0x7fffffffffffffffLL;
  37         if(hx <= 0x0001000000000000LL) {
  38             if((hx|lx)==0)
  39                 return FP_ILOGB0;       /* ilogbl(0) = FP_ILOGB0 */
  40             else                        /* subnormal x */
  41                 if(hx==0) {
  42                     for (ix = -16431; lx>0; lx<<=1) ix -=1;
  43                 } else {
  44                     for (ix = -16382, hx<<=15; hx>0; hx<<=1) ix -=1;
  45                 }
  46             return ix;
  47         }
  48         else if (hx<0x7fff000000000000LL) return (hx>>48)-0x3fff;
  49         else if (FP_ILOGBNAN != INT_MAX) {
  50             /* ISO C99 requires ilogbl(+-Inf) == INT_MAX.  */
  51             if (((hx^0x7fff000000000000LL)|lx) == 0)
  52                 return INT_MAX;
  53         }
  54         return FP_ILOGBNAN;
  55 }