first commit of the new libm!

[musl] / src / math / tanhf.c

diff --git a/src/math/tanhf.c b/src/math/tanhf.c
new file mode 100644 (file)
index 0000000..97d0eb5
--- /dev/null
+++ b/src/math/tanhf.c
@@ -0,0 +1,53 @@
+/* origin: FreeBSD /usr/src/lib/msun/src/s_tanhf.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, two = 2.0, tiny = 1.0e-30, huge = 1.0e30;
+
+float tanhf(float x)
+{
+       float t,z;
+       int32_t jx,ix;
+
+       GET_FLOAT_WORD(jx, x);
+       ix = jx & 0x7fffffff;
+
+       /* x is INF or NaN */
+       if(ix >= 0x7f800000) {
+               if (jx >= 0)
+                       return one/x + one;  /* tanh(+-inf)=+-1 */
+               else
+                       return one/x - one;  /* tanh(NaN) = NaN */
+       }
+
+       if (ix < 0x41100000) {  /* |x| < 9 */
+               if (ix < 0x39800000) {  /* |x| < 2**-12 */
+                       /* tanh(tiny) = tiny with inexact */
+                       if (huge+x > one)
+                               return x;
+               }
+               if (ix >= 0x3f800000) {  /* |x|>=1  */
+                       t = expm1f(two*fabsf(x));
+                       z = one - two/(t+two);
+               } else {
+                       t = expm1f(-two*fabsf(x));
+                       z = -t/(t+two);
+               }
+       } else {  /* |x| >= 9, return +-1 */
+               z = one - tiny;  /* raise inexact */
+       }
+       return jx >= 0 ? z : -z;
+}