first commit of the new libm!

[musl] / src / math / coshf.c

diff --git a/src/math/coshf.c b/src/math/coshf.c
new file mode 100644 (file)
index 0000000..9e87afc
--- /dev/null
+++ b/src/math/coshf.c
@@ -0,0 +1,57 @@
+/* origin: FreeBSD /usr/src/lib/msun/src/e_coshf.c */
+/*
+ * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
+ */
+/*
+ * ====================================================
+ * 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.
+ * ====================================================
+ */
+
+#include "libm.h"
+
+static const float one = 1.0, half = 0.5, huge = 1.0e30;
+
+float coshf(float x)
+{
+       float t, w;
+       int32_t ix;
+
+       GET_FLOAT_WORD(ix, x);
+       ix &= 0x7fffffff;
+
+       /* x is INF or NaN */
+       if (ix >= 0x7f800000)
+               return x*x;
+
+       /* |x| in [0,0.5*ln2], return 1+expm1(|x|)^2/(2*exp(|x|)) */
+       if (ix < 0x3eb17218) {
+               t = expm1f(fabsf(x));
+               w = one+t;
+               if (ix<0x39800000)
+                       return one;  /* cosh(tiny) = 1 */
+               return one + (t*t)/(w+w);
+       }
+
+       /* |x| in [0.5*ln2,9], return (exp(|x|)+1/exp(|x|))/2; */
+       if (ix < 0x41100000) {
+               t = expf(fabsf(x));
+               return half*t + half/t;
+       }
+
+       /* |x| in [9, log(maxfloat)] return half*exp(|x|) */
+       if (ix < 0x42b17217)
+               return half*expf(fabsf(x));
+
+       /* |x| in [log(maxfloat), overflowthresold] */
+       if (ix <= 0x42b2d4fc)
+               return __expo2f(fabsf(x));
+
+       /* |x| > overflowthresold, cosh(x) overflow */
+       return huge*huge;
+}