1 files changed, 86 insertions, 0 deletions
diff --git a/src/math/coshl.c b/src/math/coshl.c
new file mode 100644
index 00000000..bcc9128a
--- /dev/null
+++ b/src/math/coshl.c
@@ -0,0 +1,86 @@
+/* origin: OpenBSD /usr/src/lib/libm/src/ld80/e_coshl.c */
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunPro, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice
+ * is preserved.
+ * ====================================================
+ */
+/* coshl(x)
+ * Method :
+ * mathematically coshl(x) if defined to be (exp(x)+exp(-x))/2
+ *      1. Replace x by |x| (coshl(x) = coshl(-x)).
+ *      2.
+ *                                                      [ exp(x) - 1 ]^2
+ *          0        <= x <= ln2/2  :  coshl(x) := 1 + -------------------
+ *                                                         2*exp(x)
+ *
+ *                                                 exp(x) +  1/exp(x)
+ *          ln2/2    <= x <= 22     :  coshl(x) := -------------------
+ *                                                         2
+ *          22       <= x <= lnovft :  coshl(x) := expl(x)/2
+ *          lnovft   <= x <= ln2ovft:  coshl(x) := expl(x/2)/2 * expl(x/2)
+ *          ln2ovft  <  x           :  coshl(x) := huge*huge (overflow)
+ *
+ * Special cases:
+ *      coshl(x) is |x| if x is +INF, -INF, or NaN.
+ *      only coshl(0)=1 is exact for finite x.
+ */
+
+#include "libm.h"
+
+#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
+long double coshl(long double x)
+{
+	return cosh(x);
+}
+#elif LDBL_MANT_DIG == 64 && LDBL_MAX_EXP == 16384
+static const long double one = 1.0, half = 0.5, huge = 1.0e4900L;
+
+long double coshl(long double x)
+{
+	long double t,w;
+	int32_t ex;
+	uint32_t mx,lx;
+
+	/* High word of |x|. */
+	GET_LDOUBLE_WORDS(ex, mx, lx, x);
+	ex &= 0x7fff;
+
+	/* x is INF or NaN */
+	if (ex == 0x7fff) return x*x;
+
+	/* |x| in [0,0.5*ln2], return 1+expm1l(|x|)^2/(2*expl(|x|)) */
+	if (ex < 0x3ffd || (ex == 0x3ffd && mx < 0xb17217f7u)) {
+		t = expm1l(fabsl(x));
+		w = one + t;
+		if (ex < 0x3fbc) return w;    /* cosh(tiny) = 1 */
+		return one+(t*t)/(w+w);
+	}
+
+	/* |x| in [0.5*ln2,22], return (exp(|x|)+1/exp(|x|)/2; */
+	if (ex < 0x4003 || (ex == 0x4003 && mx < 0xb0000000u)) {
+		t = expl(fabsl(x));
+		return half*t + half/t;
+	}
+
+	/* |x| in [22, ln(maxdouble)] return half*exp(|x|) */
+	if (ex < 0x400c || (ex == 0x400c && mx < 0xb1700000u))
+		return half*expl(fabsl(x));
+
+	/* |x| in [log(maxdouble), log(2*maxdouble)) */
+	if (ex == 0x400c && (mx < 0xb174ddc0u ||
+	     (mx == 0xb174ddc0u && lx < 0x31aec0ebu)))
+	{
+		w = expl(half*fabsl(x));
+		t = half*w;
+		return t*w;
+	}
+
+	/* |x| >= log(2*maxdouble), cosh(x) overflow */
+	return huge*huge;
+}
+#endif