Upgrade libm.
This brings us up to date with FreeBSD HEAD, fixes various bugs, unifies
the set of functions we support on ARM, MIPS, and x86, fixes "long double",
adds ISO C99 support, and adds basic unit tests.
It turns out that our "long double" functions have always been broken
for non-normal numbers. This patch fixes that by not using the upstream
implementations and just forwarding to the regular "double" implementation
instead (since "long double" on Android is just "double" anyway, which is
what BSD doesn't support).
All the tests pass on ARM, MIPS, and x86, plus glibc on x86-64.
Bug: 3169850
Bug: 8012787
Bug: https://code.google.com/p/android/issues/detail?id=6697
Change-Id: If0c343030959c24bfc50d4d21c9530052c581837
diff --git a/libm/upstream-freebsd/lib/msun/src/e_log2.c b/libm/upstream-freebsd/lib/msun/src/e_log2.c
new file mode 100644
index 0000000..1fc44a5
--- /dev/null
+++ b/libm/upstream-freebsd/lib/msun/src/e_log2.c
@@ -0,0 +1,110 @@
+
+/* @(#)e_log10.c 1.3 95/01/18 */
+/*
+ * ====================================================
+ * 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.
+ * ====================================================
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+/*
+ * Return the base 2 logarithm of x. See e_log.c and k_log.h for most
+ * comments.
+ *
+ * This reduces x to {k, 1+f} exactly as in e_log.c, then calls the kernel,
+ * then does the combining and scaling steps
+ * log2(x) = (f - 0.5*f*f + k_log1p(f)) / ln2 + k
+ * in not-quite-routine extra precision.
+ */
+
+#include "math.h"
+#include "math_private.h"
+#include "k_log.h"
+
+static const double
+two54 = 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */
+ivln2hi = 1.44269504072144627571e+00, /* 0x3ff71547, 0x65200000 */
+ivln2lo = 1.67517131648865118353e-10; /* 0x3de705fc, 0x2eefa200 */
+
+static const double zero = 0.0;
+
+double
+__ieee754_log2(double x)
+{
+ double f,hfsq,hi,lo,r,val_hi,val_lo,w,y;
+ int32_t i,k,hx;
+ u_int32_t lx;
+
+ EXTRACT_WORDS(hx,lx,x);
+
+ k=0;
+ if (hx < 0x00100000) { /* x < 2**-1022 */
+ if (((hx&0x7fffffff)|lx)==0)
+ return -two54/zero; /* log(+-0)=-inf */
+ if (hx<0) return (x-x)/zero; /* log(-#) = NaN */
+ k -= 54; x *= two54; /* subnormal number, scale up x */
+ GET_HIGH_WORD(hx,x);
+ }
+ if (hx >= 0x7ff00000) return x+x;
+ if (hx == 0x3ff00000 && lx == 0)
+ return zero; /* log(1) = +0 */
+ k += (hx>>20)-1023;
+ hx &= 0x000fffff;
+ i = (hx+0x95f64)&0x100000;
+ SET_HIGH_WORD(x,hx|(i^0x3ff00000)); /* normalize x or x/2 */
+ k += (i>>20);
+ y = (double)k;
+ f = x - 1.0;
+ hfsq = 0.5*f*f;
+ r = k_log1p(f);
+
+ /*
+ * 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 = f - hfsq;
+ SET_LOW_WORD(hi,0);
+ lo = (f - hi) - 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: */
+ w = y + val_hi;
+ val_lo += (y - w) + val_hi;
+ val_hi = w;
+
+ return val_lo + val_hi;
+}