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 "math.h"
  17 #include "math_private.h"
  18
  19 int
  20 ilogbf(float x)
  21 {
  22         int32_t hx,ix;
  23
  24         GET_FLOAT_WORD(hx,x);
  25         hx &= 0x7fffffff;
  26         if(hx<0x00800000) {
  27             if(hx==0)
  28                 return 0x80000001;      /* ilogb(0) = 0x80000001 */
  29             else                        /* subnormal x */
  30                 for (ix = -126,hx<<=8; hx>0; hx<<=1) ix -=1;
  31             return ix;
  32         }
  33         else if (hx<0x7f800000) return (hx>>23)-127;
  34         else return 0x7fffffff;
  35 }