lib/libm/src/s_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 #include <sys/cdefs.h>
  17 #if defined(LIBM_SCCS) && !defined(lint)
  18 __RCSID("$NetBSD: s_ilogbf.c,v 1.7 2002/05/26 22:01:56 wiz Exp $");
  19 #endif
  20
  21 #include "math.h"
  22 #include "math_private.h"
  23
  24 int
  25 ilogbf(float x)
  26 {
  27         int32_t hx,ix;
  28
  29         GET_FLOAT_WORD(hx,x);
  30         hx &= 0x7fffffff;
  31         if(hx<0x00800000) {
  32             if(hx==0)
  33                 return 0x80000001;      /* ilogb(0) = 0x80000001 */
  34             else                        /* subnormal x */
  35                 for (ix = -126,hx<<=8; hx>0; hx<<=1) ix -=1;
  36             return ix;
  37         }
  38         else if (hx<0x7f800000) return (hx>>23)-127;
  39         else return 0x7fffffff;
  40 }