libquadmath/math/ilogbq.c

   1 /* ilogbq.c -- __float128 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(__float128 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 <errno.h>
  30 #include "quadmath-imp.h"
  31
  32 #ifndef FP_ILOGB0
  33 # define FP_ILOGB0 INT_MIN
  34 #endif
  35 #ifndef FP_ILOGBNAN
  36 # define FP_ILOGBNAN INT_MAX
  37 #endif
  38
  39 int
  40 ilogbq (__float128 x)
  41 {
  42         int64_t hx,lx;
  43         int ix;
  44
  45         GET_FLT128_WORDS64(hx,lx,x);
  46         hx &= 0x7fffffffffffffffLL;
  47         if(hx <= 0x0001000000000000LL) {
  48             if((hx|lx)==0)
  49               {
  50                 errno = EDOM;
  51 #ifdef USE_FENV_H
  52                 feraiseexcept (FE_INVALID);
  53 #endif
  54                 return FP_ILOGB0;       /* ilogbl(0) = FP_ILOGB0 */
  55               }
  56             else                        /* subnormal x */
  57                 if(hx==0) {
  58                     for (ix = -16431; lx>0; lx<<=1) ix -=1;
  59                 } else {
  60                     for (ix = -16382, hx<<=15; hx>0; hx<<=1) ix -=1;
  61                 }
  62             return ix;
  63         }
  64         else if (hx<0x7fff000000000000LL) return (hx>>48)-0x3fff;
  65         else if (FP_ILOGBNAN != INT_MAX) {
  66             /* ISO C99 requires ilogbl(+-Inf) == INT_MAX.  */
  67             if (((hx^0x7fff000000000000LL)|lx) == 0)
  68               {
  69                 errno = EDOM;
  70 #ifdef USE_FENV_H
  71                 feraiseexcept (FE_INVALID);
  72 #endif
  73                 return INT_MAX;
  74               }
  75         }
  76
  77         errno = EDOM;
  78 #ifdef USE_FENV_H
  79         feraiseexcept (FE_INVALID);
  80 #endif
  81         return FP_ILOGBNAN;
  82 }