sysdeps/ieee754/flt-32/e_ilogbf.c

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