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authorIan Moffett <ian@osmora.org>2024-03-07 17:28:52 -0500
committerIan Moffett <ian@osmora.org>2024-03-07 18:24:51 -0500
commitf5e48e94a2f4d4bbd6e5628c7f2afafc6dbcc459 (patch)
tree93b156621dc0303816b37f60ba88051b702d92f6 /lib/mlibc/options/ansi/musl-generic-math/log2.c
parentbd5969fc876a10b18613302db7087ef3c40f18e1 (diff)
build: Build mlibc + add distclean target
Signed-off-by: Ian Moffett <ian@osmora.org>
Diffstat (limited to 'lib/mlibc/options/ansi/musl-generic-math/log2.c')
-rw-r--r--lib/mlibc/options/ansi/musl-generic-math/log2.c122
1 files changed, 0 insertions, 122 deletions
diff --git a/lib/mlibc/options/ansi/musl-generic-math/log2.c b/lib/mlibc/options/ansi/musl-generic-math/log2.c
deleted file mode 100644
index 0aafad4..0000000
--- a/lib/mlibc/options/ansi/musl-generic-math/log2.c
+++ /dev/null
@@ -1,122 +0,0 @@
-/* origin: FreeBSD /usr/src/lib/msun/src/e_log2.c */
-/*
- * ====================================================
- * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
- *
- * Developed at SunSoft, a Sun Microsystems, Inc. business.
- * Permission to use, copy, modify, and distribute this
- * software is freely granted, provided that this notice
- * is preserved.
- * ====================================================
- */
-/*
- * Return the base 2 logarithm of x. See log.c for most comments.
- *
- * Reduce x to 2^k (1+f) and calculate r = log(1+f) - f + f*f/2
- * as in log.c, then combine and scale in extra precision:
- * log2(x) = (f - f*f/2 + r)/log(2) + k
- */
-
-#include <math.h>
-#include <stdint.h>
-
-static const double
-ivln2hi = 1.44269504072144627571e+00, /* 0x3ff71547, 0x65200000 */
-ivln2lo = 1.67517131648865118353e-10, /* 0x3de705fc, 0x2eefa200 */
-Lg1 = 6.666666666666735130e-01, /* 3FE55555 55555593 */
-Lg2 = 3.999999999940941908e-01, /* 3FD99999 9997FA04 */
-Lg3 = 2.857142874366239149e-01, /* 3FD24924 94229359 */
-Lg4 = 2.222219843214978396e-01, /* 3FCC71C5 1D8E78AF */
-Lg5 = 1.818357216161805012e-01, /* 3FC74664 96CB03DE */
-Lg6 = 1.531383769920937332e-01, /* 3FC39A09 D078C69F */
-Lg7 = 1.479819860511658591e-01; /* 3FC2F112 DF3E5244 */
-
-double log2(double x)
-{
- union {double f; uint64_t i;} u = {x};
- double_t hfsq,f,s,z,R,w,t1,t2,y,hi,lo,val_hi,val_lo;
- uint32_t hx;
- int k;
-
- hx = u.i>>32;
- k = 0;
- if (hx < 0x00100000 || hx>>31) {
- if (u.i<<1 == 0)
- return -1/(x*x); /* log(+-0)=-inf */
- if (hx>>31)
- return (x-x)/0.0; /* log(-#) = NaN */
- /* subnormal number, scale x up */
- k -= 54;
- x *= 0x1p54;
- u.f = x;
- hx = u.i>>32;
- } else if (hx >= 0x7ff00000) {
- return x;
- } else if (hx == 0x3ff00000 && u.i<<32 == 0)
- return 0;
-
- /* reduce x into [sqrt(2)/2, sqrt(2)] */
- hx += 0x3ff00000 - 0x3fe6a09e;
- k += (int)(hx>>20) - 0x3ff;
- hx = (hx&0x000fffff) + 0x3fe6a09e;
- u.i = (uint64_t)hx<<32 | (u.i&0xffffffff);
- x = u.f;
-
- f = x - 1.0;
- hfsq = 0.5*f*f;
- s = f/(2.0+f);
- z = s*s;
- w = z*z;
- t1 = w*(Lg2+w*(Lg4+w*Lg6));
- t2 = z*(Lg1+w*(Lg3+w*(Lg5+w*Lg7)));
- R = t2 + t1;
-
- /*
- * f-hfsq must (for args near 1) be evaluated in extra precision
- * to avoid a large cancellation when x is near sqrt(2) or 1/sqrt(2).
- * This is fairly efficient since f-hfsq only depends on f, so can
- * be evaluated in parallel with R. Not combining hfsq with R also
- * keeps R small (though not as small as a true `lo' term would be),
- * so that extra precision is not needed for terms involving R.
- *
- * Compiler bugs involving extra precision used to break Dekker's
- * theorem for spitting f-hfsq as hi+lo, unless double_t was used
- * or the multi-precision calculations were avoided when double_t
- * has extra precision. These problems are now automatically
- * avoided as a side effect of the optimization of combining the
- * Dekker splitting step with the clear-low-bits step.
- *
- * y must (for args near sqrt(2) and 1/sqrt(2)) be added in extra
- * precision to avoid a very large cancellation when x is very near
- * these values. Unlike the above cancellations, this problem is
- * specific to base 2. It is strange that adding +-1 is so much
- * harder than adding +-ln2 or +-log10_2.
- *
- * This uses Dekker's theorem to normalize y+val_hi, so the
- * compiler bugs are back in some configurations, sigh. And I
- * don't want to used double_t to avoid them, since that gives a
- * pessimization and the support for avoiding the pessimization
- * is not yet available.
- *
- * The multi-precision calculations for the multiplications are
- * routine.
- */
-
- /* hi+lo = f - hfsq + s*(hfsq+R) ~ log(1+f) */
- hi = f - hfsq;
- u.f = hi;
- u.i &= (uint64_t)-1<<32;
- hi = u.f;
- lo = f - hi - hfsq + s*(hfsq+R);
-
- val_hi = hi*ivln2hi;
- val_lo = (lo+hi)*ivln2lo + lo*ivln2hi;
-
- /* spadd(val_hi, val_lo, y), except for not using double_t: */
- y = k;
- w = y + val_hi;
- val_lo += (y - w) + val_hi;
- val_hi = w;
-
- return val_lo + val_hi;
-}