1 files changed, 80 insertions, 0 deletions
diff --git a/modules/fdlibm/src/e_cosh.cpp b/modules/fdlibm/src/e_cosh.cpp
new file mode 100644
index 000000000..42cb277d4
--- /dev/null
+++ b/modules/fdlibm/src/e_cosh.cpp
@@ -0,0 +1,80 @@
+
+/* @(#)e_cosh.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("$FreeBSD$");
+
+/* __ieee754_cosh(x)
+ * Method : 
+ * mathematically cosh(x) if defined to be (exp(x)+exp(-x))/2
+ *	1. Replace x by |x| (cosh(x) = cosh(-x)). 
+ *	2. 
+ *		                                        [ exp(x) - 1 ]^2 
+ *	    0        <= x <= ln2/2  :  cosh(x) := 1 + -------------------
+ *			       			           2*exp(x)
+ *
+ *		                                  exp(x) +  1/exp(x)
+ *	    ln2/2    <= x <= 22     :  cosh(x) := -------------------
+ *			       			          2
+ *	    22       <= x <= lnovft :  cosh(x) := exp(x)/2 
+ *	    lnovft   <= x <= ln2ovft:  cosh(x) := exp(x/2)/2 * exp(x/2)
+ *	    ln2ovft  <  x	    :  cosh(x) := huge*huge (overflow)
+ *
+ * Special cases:
+ *	cosh(x) is |x| if x is +INF, -INF, or NaN.
+ *	only cosh(0)=1 is exact for finite x.
+ */
+
+#include <float.h>
+
+#include "math_private.h"
+
+static const double one = 1.0, half=0.5, huge = 1.0e300;
+
+double
+__ieee754_cosh(double x)
+{
+	double t,w;
+	int32_t ix;
+
+    /* High word of |x|. */
+	GET_HIGH_WORD(ix,x);
+	ix &= 0x7fffffff;
+
+    /* x is INF or NaN */
+	if(ix>=0x7ff00000) return x*x;	
+
+    /* |x| in [0,0.5*ln2], return 1+expm1(|x|)^2/(2*exp(|x|)) */
+	if(ix<0x3fd62e43) {
+	    t = expm1(fabs(x));
+	    w = one+t;
+	    if (ix<0x3c800000) 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 (ix < 0x40360000) {
+		t = __ieee754_exp(fabs(x));
+		return half*t+half/t;
+	}
+
+    /* |x| in [22, log(maxdouble)] return half*exp(|x|) */
+	if (ix < 0x40862E42)  return half*__ieee754_exp(fabs(x));
+
+    /* |x| in [log(maxdouble), overflowthresold] */
+	if (ix<=0x408633CE)
+	    return __ldexp_exp(fabs(x), -1);
+
+    /* |x| > overflowthresold, cosh(x) overflow */
+	return huge*huge;
+}