1 /* e_log10f.c -- float version of e_log10.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 <sys/cdefs.h> 17 __FBSDID("$FreeBSD$"); 18 19 #include "math.h" 20 #include "math_private.h" 21 22 static const float 23 two25 = 3.3554432000e+07, /* 0x4c000000 */ 24 ivln10 = 4.3429449201e-01, /* 0x3ede5bd9 */ 25 log10_2hi = 3.0102920532e-01, /* 0x3e9a2080 */ 26 log10_2lo = 7.9034151668e-07; /* 0x355427db */ 27 28 static const float zero = 0.0; 29 30 float 31 __ieee754_log10f(float x) 32 { 33 float y,z; 34 int32_t i,k,hx; 35 36 GET_FLOAT_WORD(hx,x); 37 38 k=0; 39 if (hx < 0x00800000) { /* x < 2**-126 */ 40 if ((hx&0x7fffffff)==0) 41 return -two25/zero; /* log(+-0)=-inf */ 42 if (hx<0) return (x-x)/zero; /* log(-#) = NaN */ 43 k -= 25; x *= two25; /* subnormal number, scale up x */ 44 GET_FLOAT_WORD(hx,x); 45 } 46 if (hx >= 0x7f800000) return x+x; 47 k += (hx>>23)-127; 48 i = ((u_int32_t)k&0x80000000)>>31; 49 hx = (hx&0x007fffff)|((0x7f-i)<<23); 50 y = (float)(k+i); 51 SET_FLOAT_WORD(x,hx); 52 z = y*log10_2lo + ivln10*__ieee754_logf(x); 53 return z+y*log10_2hi; 54 } 55