s_logbf.c revision 22993
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#ifndef lint 17static char rcsid[] = "$Id$"; 18#endif 19 20#include "math.h" 21#include "math_private.h" 22 23#ifdef __STDC__ 24 float logbf(float x) 25#else 26 float logbf(x) 27 float x; 28#endif 29{ 30 int32_t ix; 31 GET_FLOAT_WORD(ix,x); 32 ix &= 0x7fffffff; /* high |x| */ 33 if(ix==0) return (float)-1.0/fabsf(x); 34 if(ix>=0x7f800000) return x*x; 35 if((ix>>=23)==0) /* IEEE 754 logb */ 36 return -126.0; 37 else 38 return (float) (ix-127); 39} 40