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  }