From b69f695acedd4ce2798ef9ea28d834ceccc789bd Mon Sep 17 00:00:00 2001
From: Rich Felker <dalias@aerifal.cx>
Date: Tue, 13 Mar 2012 01:17:53 -0400
Subject: first commit of the new libm!

thanks to the hard work of Szabolcs Nagy (nsz), identifying the best
(from correctness and license standpoint) implementations from freebsd
and openbsd and cleaning them up! musl should now fully support c99
float and long double math functions, and has near-complete complex
math support. tgmath should also work (fully on gcc-compatible
compilers, and mostly on any c99 compiler).

based largely on commit 0376d44a890fea261506f1fc63833e7a686dca19 from
nsz's libm git repo, with some additions (dummy versions of a few
missing long double complex functions, etc.) by me.

various cleanups still need to be made, including re-adding (if
they're correct) some asm functions that were dropped.
---
 src/math/tanl.c | 84 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 84 insertions(+)
 create mode 100644 src/math/tanl.c

(limited to 'src/math/tanl.c')

diff --git a/src/math/tanl.c b/src/math/tanl.c
new file mode 100644
index 00000000..462ead91
--- /dev/null
+++ b/src/math/tanl.c
@@ -0,0 +1,84 @@
+/* origin: FreeBSD /usr/src/lib/msun/src/s_tanl.c */
+/*-
+ * Copyright (c) 2007 Steven G. Kargl
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice unmodified, this list of conditions, and the following
+ *    disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+/*
+ * Limited testing on pseudorandom numbers drawn within [0:4e8] shows
+ * an accuracy of <= 1.5 ULP where 247024 values of x out of 40 million
+ * possibles resulted in tan(x) that exceeded 0.5 ULP (ie., 0.6%).
+ */
+
+#include "libm.h"
+
+#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
+long double tanl(long double x)
+{
+	return tan(x);
+}
+#elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384
+#include "__rem_pio2l.h"
+
+long double tanl(long double x)
+{
+	union IEEEl2bits z;
+	int e0, s;
+	long double y[2];
+	long double hi, lo;
+
+	z.e = x;
+	s = z.bits.sign;
+	z.bits.sign = 0;
+
+	/* If x = +-0 or x is subnormal, then tan(x) = x. */
+	if (z.bits.exp == 0)
+		return x;
+
+	/* If x = NaN or Inf, then tan(x) = NaN. */
+	if (z.bits.exp == 32767)
+		return (x - x) / (x - x);
+
+	/* Optimize the case where x is already within range. */
+	if (z.e < M_PI_4) {
+		hi = __tanl(z.e, 0, 0);
+		return s ? -hi : hi;
+	}
+
+	e0 = __rem_pio2l(x, y);
+	hi = y[0];
+	lo = y[1];
+
+	switch (e0 & 3) {
+	case 0:
+	case 2:
+		hi = __tanl(hi, lo, 0);
+		break;
+	case 1:
+	case 3:
+		hi = __tanl(hi, lo, 1);
+		break;
+	}
+	return hi;
+}
+#endif
-- 
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