1 /* 2 * ==================================================== 3 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 4 * 5 * Developed at SunPro, a Sun Microsystems, Inc. business. 6 * Permission to use, copy, modify, and distribute this 7 * software is freely granted, provided that this notice 8 * is preserved. 9 * ==================================================== 10 */ 11 12 #include "cdefs-compat.h" 13 //__FBSDID("$FreeBSD: src/lib/msun/src/e_log10f.c,v 1.13 2011/10/16 05:36:23 das Exp $"); 14 15 /* 16 * Float version of e_log10.c. See the latter for most comments. 17 */ 18 19 #include <openlibm_math.h> 20 21 #include "math_private.h" 22 #include "k_logf.h" 23 24 // VBS 25 #define float_t float 26 27 static const float 28 two25 = 3.3554432000e+07, /* 0x4c000000 */ 29 ivln10hi = 4.3432617188e-01, /* 0x3ede6000 */ 30 ivln10lo = -3.1689971365e-05, /* 0xb804ead9 */ 31 log10_2hi = 3.0102920532e-01, /* 0x3e9a2080 */ 32 log10_2lo = 7.9034151668e-07; /* 0x355427db */ 33 34 static const float zero = 0.0; 35 36 DLLEXPORT float 37 __ieee754_log10f(float x) 38 { 39 float f,hfsq,hi,lo,r,y; 40 int32_t i,k,hx; 41 42 GET_FLOAT_WORD(hx,x); 43 44 k=0; 45 if (hx < 0x00800000) { /* x < 2**-126 */ 46 if ((hx&0x7fffffff)==0) 47 return -two25/zero; /* log(+-0)=-inf */ 48 if (hx<0) return (x-x)/zero; /* log(-#) = NaN */ 49 k -= 25; x *= two25; /* subnormal number, scale up x */ 50 GET_FLOAT_WORD(hx,x); 51 } 52 if (hx >= 0x7f800000) return x+x; 53 if (hx == 0x3f800000) 54 return zero; /* log(1) = +0 */ 55 k += (hx>>23)-127; 56 hx &= 0x007fffff; 57 i = (hx+(0x4afb0d))&0x800000; 58 SET_FLOAT_WORD(x,hx|(i^0x3f800000)); /* normalize x or x/2 */ 59 k += (i>>23); 60 y = (float)k; 61 f = x - (float)1.0; 62 hfsq = (float)0.5*f*f; 63 r = k_log1pf(f); 64 65 /* See e_log2f.c and e_log2.c for details. */ 66 if (sizeof(float_t) > sizeof(float)) 67 return (r - hfsq + f) * ((float_t)ivln10lo + ivln10hi) + 68 y * ((float_t)log10_2lo + log10_2hi); 69 hi = f - hfsq; 70 GET_FLOAT_WORD(hx,hi); 71 SET_FLOAT_WORD(hi,hx&0xfffff000); 72 lo = (f - hi) - hfsq + r; 73 return y*log10_2lo + (lo+hi)*ivln10lo + lo*ivln10hi + hi*ivln10hi + 74 y*log10_2hi; 75 } 76