1 /* s_logbf.c -- float version of s_logb.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 static const float 20 two25 = 3.355443200e+07; /* 0x4c000000 */ 21 22 float 23 logbf(float x) 24 { 25 int32_t ix; 26 GET_FLOAT_WORD(ix,x); 27 ix &= 0x7fffffff; /* high |x| */ 28 if(ix==0) return (float)-1.0/fabsf(x); 29 if(ix>=0x7f800000) return x*x; 30 if(ix<0x00800000) { 31 x *= two25; /* convert subnormal x to normal */ 32 GET_FLOAT_WORD(ix,x); 33 ix &= 0x7fffffff; 34 return (float) ((ix>>23)-127-25); 35 } else 36 return (float) ((ix>>23)-127); 37 } 38