1 files changed, 84 insertions, 0 deletions
diff --git a/src/math/tanl.c b/src/math/tanl.c
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+/* 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