sysdeps/ieee754/flt-32/e_ilogbf.c

   1 /* s_ilogbf.c -- float version of s_ilogb.c.
   2  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
   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: s_ilogbf.c,v 1.4 1995/05/10 20:47:31 jtc Exp $";
  18 #endif
  19
  20 #include <limits.h>
  21 #include <math.h>
  22 #include <math_private.h>
  23
  24 int __ieee754_ilogbf(float x)
  25 {
  26         int32_t hx,ix;
  27
  28         GET_FLOAT_WORD(hx,x);
  29         hx &= 0x7fffffff;
  30         if(hx<0x00800000) {
  31             if(hx==0)
  32                 return FP_ILOGB0;       /* ilogb(0) = FP_ILOGB0 */
  33             else                        /* subnormal x */
  34                 for (ix = -126,hx<<=8; hx>0; hx<<=1) ix -=1;
  35             return ix;
  36         }
  37         else if (hx<0x7f800000) return (hx>>23)-127;
  38         else if (FP_ILOGBNAN != INT_MAX) {
  39             /* ISO C99 requires ilogbf(+-Inf) == INT_MAX.  */
  40             if (hx==0x7f800000)
  41                 return INT_MAX;
  42         }
  43         return FP_ILOGBNAN;
  44 }