/* e_log10f.c -- float version of e_log10.c. * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. */ /* * ==================================================== * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. * * Developed at SunPro, a Sun Microsystems, Inc. business. * Permission to use, copy, modify, and distribute this * software is freely granted, provided that this notice * is preserved. * ==================================================== */ #include <sys/cdefs.h> #if defined(LIBM_SCCS) && !defined(lint) __RCSID("$NetBSD: e_log10f.c,v 1.8 2002/05/26 22:01:51 wiz Exp $"); #endif #include "math.h" #include "math_private.h" static const float two25 = 3.3554432000e+07, /* 0x4c000000 */ ivln10 = 4.3429449201e-01, /* 0x3ede5bd9 */ log10_2hi = 3.0102920532e-01, /* 0x3e9a2080 */ log10_2lo = 7.9034151668e-07; /* 0x355427db */ static const float zero = 0.0; float __ieee754_log10f(float x) { float y,z; int32_t i,k,hx; GET_FLOAT_WORD(hx,x); k=0; if (hx < 0x00800000) { /* x < 2**-126 */ if ((hx&0x7fffffff)==0) return -two25/zero; /* log(+-0)=-inf */ if (hx<0) return (x-x)/zero; /* log(-#) = NaN */ k -= 25; x *= two25; /* subnormal number, scale up x */ GET_FLOAT_WORD(hx,x); } if (hx >= 0x7f800000) return x+x; k += (hx>>23)-127; i = ((u_int32_t)k&0x80000000)>>31; hx = (hx&0x007fffff)|((0x7f-i)<<23); y = (float)(k+i); SET_FLOAT_WORD(x,hx); z = y*log10_2lo + ivln10*__ieee754_logf(x); return z+y*log10_2hi; } |