first commit of the new libm!

[musl] / src / math / tanhl.c

diff --git a/src/math/tanhl.c b/src/math/tanhl.c
new file mode 100644 (file)
index 0000000..e62be59
--- /dev/null
+++ b/src/math/tanhl.c
@@ -0,0 +1,83 @@
+/* origin: OpenBSD /usr/src/lib/libm/src/ld80/s_tanhl.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.
+ * ====================================================
+ */
+/* tanhl(x)
+ * Return the Hyperbolic Tangent of x
+ *
+ * Method :
+ *                                      x    -x
+ *                                     e  - e
+ *      0. tanhl(x) is defined to be -----------
+ *                                      x    -x
+ *                                     e  + e
+ *      1. reduce x to non-negative by tanhl(-x) = -tanhl(x).
+ *      2.  0      <= x <= 2**-55 : tanhl(x) := x*(one+x)
+ *                                               -t
+ *          2**-55 <  x <=  1     : tanhl(x) := -----; t = expm1l(-2x)
+ *                                              t + 2
+ *                                                    2
+ *          1      <= x <=  23.0  : tanhl(x) := 1-  ----- ; t=expm1l(2x)
+ *                                                  t + 2
+ *          23.0   <  x <= INF    : tanhl(x) := 1.
+ *
+ * Special cases:
+ *      tanhl(NaN) is NaN;
+ *      only tanhl(0)=0 is exact for finite argument.
+ */
+
+#include "libm.h"
+
+#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
+long double tanhl(long double x)
+{
+       return tanh(x);
+}
+#elif LDBL_MANT_DIG == 64 && LDBL_MAX_EXP == 16384
+static const long double one=1.0, two=2.0, tiny = 1.0e-4900L;
+
+long double tanhl(long double x)
+{
+       long double t,z;
+       int32_t se;
+       uint32_t jj0,jj1,ix;
+
+       /* High word of |x|. */
+       GET_LDOUBLE_WORDS(se, jj0, jj1, x);
+       ix = se & 0x7fff;
+
+       /* x is INF or NaN */
+       if (ix == 0x7fff) {
+               /* for NaN it's not important which branch: tanhl(NaN) = NaN */
+               if (se & 0x8000)
+                       return one/x-one;  /* tanhl(-inf)= -1; */
+               return one/x+one;          /* tanhl(+inf)= +1 */
+       }
+
+       /* |x| < 23 */
+       if (ix < 0x4003 || (ix == 0x4003 && jj0 < 0xb8000000u)) {
+               if ((ix|jj0|jj1) == 0) /* x == +- 0 */
+                       return x;
+               if (ix < 0x3fc8)       /* |x| < 2**-55 */
+                       return x*(one+tiny);  /* tanh(small) = small */
+               if (ix >= 0x3fff) {    /* |x| >= 1  */
+                       t = expm1l(two*fabsl(x));
+                       z = one - two/(t+two);
+               } else {
+                       t = expm1l(-two*fabsl(x));
+                       z = -t/(t+two);
+               }
+       /* |x| > 23, return +-1 */
+       } else {
+               z = one - tiny;  /* raise inexact flag */
+       }
+       return se & 0x8000 ? -z : z;
+}
+#endif