mirror of
https://github.com/jart/cosmopolitan.git
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112 lines
4.7 KiB
C
112 lines
4.7 KiB
C
/*-*- mode:c;indent-tabs-mode:t;c-basic-offset:8;tab-width:8;coding:utf-8 -*-│
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│vi: set et ft=c ts=8 tw=8 fenc=utf-8 :vi│
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╚──────────────────────────────────────────────────────────────────────────────╝
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│ │
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│ Musl Libc │
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│ Copyright © 2005-2014 Rich Felker, et al. │
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│ │
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│ Permission is hereby granted, free of charge, to any person obtaining │
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│ a copy of this software and associated documentation files (the │
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│ "Software"), to deal in the Software without restriction, including │
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│ without limitation the rights to use, copy, modify, merge, publish, │
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│ distribute, sublicense, and/or sell copies of the Software, and to │
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│ permit persons to whom the Software is furnished to do so, subject to │
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│ the following conditions: │
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│ │
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│ The above copyright notice and this permission notice shall be │
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│ included in all copies or substantial portions of the Software. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, │
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│ EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF │
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│ MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. │
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│ IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY │
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│ CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, │
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│ TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE │
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│ SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. │
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│ │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/math.h"
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asm(".ident\t\"\\n\\n\
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fdlibm (fdlibm license)\\n\
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Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.\"");
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asm(".ident\t\"\\n\\n\
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Musl libc (MIT License)\\n\
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Copyright 2005-2014 Rich Felker, et. al.\"");
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asm(".include \"libc/disclaimer.inc\"");
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/* clang-format off */
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/* origin: FreeBSD /usr/src/lib/msun/src/e_log10f.c */
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/*
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* ====================================================
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunPro, a Sun Microsystems, Inc. business.
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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* is preserved.
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* ====================================================
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*/
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/*
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* See comments in log10.c.
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*/
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static const float
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ivln10hi = 4.3432617188e-01, /* 0x3ede6000 */
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ivln10lo = -3.1689971365e-05, /* 0xb804ead9 */
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log10_2hi = 3.0102920532e-01, /* 0x3e9a2080 */
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log10_2lo = 7.9034151668e-07, /* 0x355427db */
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/* |(log(1+s)-log(1-s))/s - Lg(s)| < 2**-34.24 (~[-4.95e-11, 4.97e-11]). */
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Lg1 = 0xaaaaaa.0p-24, /* 0.66666662693 */
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Lg2 = 0xccce13.0p-25, /* 0.40000972152 */
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Lg3 = 0x91e9ee.0p-25, /* 0.28498786688 */
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Lg4 = 0xf89e26.0p-26; /* 0.24279078841 */
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float log10f(float x)
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{
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union {float f; uint32_t i;} u = {x};
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float_t hfsq,f,s,z,R,w,t1,t2,dk,hi,lo;
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uint32_t ix;
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int k;
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ix = u.i;
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k = 0;
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if (ix < 0x00800000 || ix>>31) { /* x < 2**-126 */
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if (ix<<1 == 0)
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return -1/(x*x); /* log(+-0)=-inf */
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if (ix>>31)
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return (x-x)/0.0f; /* log(-#) = NaN */
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/* subnormal number, scale up x */
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k -= 25;
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x *= 0x1p25f;
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u.f = x;
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ix = u.i;
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} else if (ix >= 0x7f800000) {
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return x;
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} else if (ix == 0x3f800000)
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return 0;
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/* reduce x into [sqrt(2)/2, sqrt(2)] */
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ix += 0x3f800000 - 0x3f3504f3;
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k += (int)(ix>>23) - 0x7f;
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ix = (ix&0x007fffff) + 0x3f3504f3;
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u.i = ix;
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x = u.f;
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f = x - 1.0f;
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s = f/(2.0f + f);
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z = s*s;
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w = z*z;
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t1= w*(Lg2+w*Lg4);
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t2= z*(Lg1+w*Lg3);
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R = t2 + t1;
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hfsq = 0.5f*f*f;
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hi = f - hfsq;
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u.f = hi;
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u.i &= 0xfffff000;
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hi = u.f;
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lo = f - hi - hfsq + s*(hfsq+R);
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dk = k;
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return dk*log10_2lo + (lo+hi)*ivln10lo + lo*ivln10hi + hi*ivln10hi + dk*log10_2hi;
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}
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