12116Sjkh/* 22116Sjkh * ==================================================== 32116Sjkh * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 42116Sjkh * 52116Sjkh * Developed at SunPro, a Sun Microsystems, Inc. business. 62116Sjkh * Permission to use, copy, modify, and distribute this 78870Srgrimes * software is freely granted, provided that this notice 82116Sjkh * is preserved. 92116Sjkh * ==================================================== 102116Sjkh */ 112116Sjkh 12176451Sdas#include <sys/cdefs.h> 13176451Sdas__FBSDID("$FreeBSD$"); 142116Sjkh 15219361Sdas/* 16226375Sdas * Float version of e_log10.c. See the latter for most comments. 17219361Sdas */ 18219361Sdas 192116Sjkh#include "math.h" 202116Sjkh#include "math_private.h" 21219361Sdas#include "k_logf.h" 222116Sjkh 232116Sjkhstatic const float 242116Sjkhtwo25 = 3.3554432000e+07, /* 0x4c000000 */ 25219361Sdasivln10hi = 4.3432617188e-01, /* 0x3ede6000 */ 26219361Sdasivln10lo = -3.1689971365e-05, /* 0xb804ead9 */ 272116Sjkhlog10_2hi = 3.0102920532e-01, /* 0x3e9a2080 */ 282116Sjkhlog10_2lo = 7.9034151668e-07; /* 0x355427db */ 292116Sjkh 302116Sjkhstatic const float zero = 0.0; 31251024Sdasstatic volatile float vzero = 0.0; 322116Sjkh 3397413Salfredfloat 3497413Salfred__ieee754_log10f(float x) 352116Sjkh{ 36226411Sdas float f,hfsq,hi,lo,r,y; 372116Sjkh int32_t i,k,hx; 382116Sjkh 392116Sjkh GET_FLOAT_WORD(hx,x); 402116Sjkh 41226375Sdas k=0; 42226375Sdas if (hx < 0x00800000) { /* x < 2**-126 */ 43226375Sdas if ((hx&0x7fffffff)==0) 44251024Sdas return -two25/vzero; /* log(+-0)=-inf */ 45226375Sdas if (hx<0) return (x-x)/zero; /* log(-#) = NaN */ 46226375Sdas k -= 25; x *= two25; /* subnormal number, scale up x */ 472116Sjkh GET_FLOAT_WORD(hx,x); 48226375Sdas } 492116Sjkh if (hx >= 0x7f800000) return x+x; 50226376Sdas if (hx == 0x3f800000) 51226376Sdas return zero; /* log(1) = +0 */ 522116Sjkh k += (hx>>23)-127; 53219361Sdas hx &= 0x007fffff; 54219361Sdas i = (hx+(0x4afb0d))&0x800000; 55219361Sdas SET_FLOAT_WORD(x,hx|(i^0x3f800000)); /* normalize x or x/2 */ 56219361Sdas k += (i>>23); 57219361Sdas y = (float)k; 58226376Sdas f = x - (float)1.0; 59226376Sdas hfsq = (float)0.5*f*f; 60226376Sdas r = k_log1pf(f); 61226376Sdas 62226376Sdas /* See e_log2f.c and e_log2.c for details. */ 63226376Sdas if (sizeof(float_t) > sizeof(float)) 64226376Sdas return (r - hfsq + f) * ((float_t)ivln10lo + ivln10hi) + 65226376Sdas y * ((float_t)log10_2lo + log10_2hi); 66226376Sdas hi = f - hfsq; 67226376Sdas GET_FLOAT_WORD(hx,hi); 68219361Sdas SET_FLOAT_WORD(hi,hx&0xfffff000); 69226376Sdas lo = (f - hi) - hfsq + r; 70226376Sdas return y*log10_2lo + (lo+hi)*ivln10lo + lo*ivln10hi + hi*ivln10hi + 71226376Sdas y*log10_2hi; 722116Sjkh} 73