Meta: Add OpenLibm

src/openlibm/ld80/e_atanhl.c

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+/* @(#)e_atanh.c 5.1 93/09/24 */
+/*
+ * ====================================================
+ * 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.
+ * ====================================================
+ */
+
+/* atanhl(x)
+ * Method :
+ *    1.Reduced x to positive by atanh(-x) = -atanh(x)
+ *    2.For x>=0.5
+ *                   1              2x                          x
+ *	atanhl(x) = --- * log(1 + -------) = 0.5 * log1p(2 * --------)
+ *                   2             1 - x                      1 - x
+ *
+ * 	For x<0.5
+ *	atanhl(x) = 0.5*log1pl(2x+2x*x/(1-x))
+ *
+ * Special cases:
+ *	atanhl(x) is NaN if |x| > 1 with signal;
+ *	atanhl(NaN) is that NaN with no signal;
+ *	atanhl(+-1) is +-INF with signal.
+ *
+ */
+
+#include <openlibm_math.h>
+
+#include "math_private.h"
+
+static const long double one = 1.0, huge = 1e4900L;
+
+static const long double zero = 0.0;
+
+long double
+atanhl(long double x)
+{
+	long double t;
+	int32_t ix;
+	u_int32_t se,i0,i1;
+	GET_LDOUBLE_WORDS(se,i0,i1,x);
+	ix = se&0x7fff;
+	if ((ix+((((i0&0x7fffffff)|i1)|(-((i0&0x7fffffff)|i1)))>>31))>0x3fff)
+	  /* |x|>1 */
+	    return (x-x)/(x-x);
+	if(ix==0x3fff)
+	    return x/zero;
+	if(ix<0x3fe3&&(huge+x)>zero) return x;	/* x<2**-28 */
+	SET_LDOUBLE_EXP(x,ix);
+	if(ix<0x3ffe) {		/* x < 0.5 */
+	    t = x+x;
+	    t = 0.5*log1pl(t+t*x/(one-x));
+	} else
+	    t = 0.5*log1pl((x+x)/(one-x));
+	if(se<=0x7fff) return t; else return -t;
+}