compiler/stdc/math/s_ilogb.c

   1 /* @(#)s_ilogb.c 5.1 93/09/24 */
   2 /*
   3  * ====================================================
   4  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   5  *
   6  * Developed at SunPro, a Sun Microsystems, Inc. business.
   7  * Permission to use, copy, modify, and distribute this
   8  * software is freely granted, provided that this notice
   9  * is preserved.
  10  * ====================================================
  11  */
  12
  13 #ifndef lint
  14 static char rcsid[] = "$FreeBSD: src/lib/msun/src/s_ilogb.c,v 1.10 2008/02/22 02:30:35 das Exp $";
  15 #endif
  16
  17 /* ilogb(double x)
  18  * return the binary exponent of non-zero x
  19  * ilogb(0) = FP_ILOGB0
  20  * ilogb(NaN) = FP_ILOGBNAN (no signal is raised)
  21  * ilogb(inf) = INT_MAX (no signal is raised)
  22  */
  23
  24 #include <float.h>
  25 #include <limits.h>
  26
  27 #include "math.h"
  28 #include "math_private.h"
  29
  30         int ilogb(double x)
  31 {
  32         int32_t hx,lx,ix;
  33
  34         EXTRACT_WORDS(hx,lx,x);
  35         hx &= 0x7fffffff;
  36         if(hx<0x00100000) {
  37             if((hx|lx)==0)
  38                 return FP_ILOGB0;
  39             else                        /* subnormal x */
  40                 if(hx==0) {
  41                     for (ix = -1043; lx>0; lx<<=1) ix -=1;
  42                 } else {
  43                     for (ix = -1022,hx<<=11; hx>0; hx<<=1) ix -=1;
  44                 }
  45             return ix;
  46         }
  47         else if (hx<0x7ff00000) return (hx>>20)-1023;
  48         else if (hx>0x7ff00000 || lx!=0) return FP_ILOGBNAN;
  49         else return INT_MAX;
  50 }
  51
  52 #if     LDBL_MANT_DIG == DBL_MANT_DIG
  53 AROS_MAKE_ASM_SYM(typeof(ilogbl), ilogbl, AROS_CSYM_FROM_ASM_NAME(ilogbl), AROS_CSYM_FROM_ASM_NAME(ilogb));
  54 AROS_EXPORT_ASM_SYM(AROS_CSYM_FROM_ASM_NAME(ilogbl));
  55 #endif