libquadmath/math/ilogbq.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 "quadmath-imp.h"
  30
  31 #ifndef FP_ILOGB0
  32 # define FP_ILOGB0 INT_MIN
  33 #endif
  34 #ifndef FP_ILOGBNAN
  35 # define FP_ILOGBNAN INT_MAX
  36 #endif
  37
  38 int
  39 ilogbq (__float128 x)
  40 {
  41         int64_t hx,lx;
  42         int ix;
  43
  44         GET_FLT128_WORDS64(hx,lx,x);
  45         hx &= 0x7fffffffffffffffLL;
  46         if(hx <= 0x0001000000000000LL) {
  47             if((hx|lx)==0)
  48                 return FP_ILOGB0;       /* ilogbl(0) = FP_ILOGB0 */
  49             else                        /* subnormal x */
  50                 if(hx==0) {
  51                     for (ix = -16431; lx>0; lx<<=1) ix -=1;
  52                 } else {
  53                     for (ix = -16382, hx<<=15; hx>0; hx<<=1) ix -=1;
  54                 }
  55             return ix;
  56         }
  57         else if (hx<0x7fff000000000000LL) return (hx>>48)-0x3fff;
  58         else if (FP_ILOGBNAN != INT_MAX) {
  59             /* ISO C99 requires ilogbl(+-Inf) == INT_MAX.  */
  60             if (((hx^0x7fff000000000000LL)|lx) == 0)
  61                 return INT_MAX;
  62         }
  63         return FP_ILOGBNAN;
  64 }