Add a "fork" of musl as //fusl.

fusl/src/math/asinhl.c

Index: fusl/src/math/asinhl.c
diff --git a/fusl/src/math/asinhl.c b/fusl/src/math/asinhl.c
new file mode 100644
index 0000000000000000000000000000000000000000..8635f52e82381bdaff12badbd7cd170b2e05bf62
--- /dev/null
+++ b/fusl/src/math/asinhl.c
@@ -0,0 +1,41 @@
+#include "libm.h"
+
+#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
+long double asinhl(long double x)
+{
+	return asinh(x);
+}
+#elif LDBL_MANT_DIG == 64 && LDBL_MAX_EXP == 16384
+/* asinh(x) = sign(x)*log(|x|+sqrt(x*x+1)) ~= x - x^3/6 + o(x^5) */
+long double asinhl(long double x)
+{
+	union ldshape u = {x};
+	unsigned e = u.i.se & 0x7fff;
+	unsigned s = u.i.se >> 15;
+
+	/* |x| */
+	u.i.se = e;
+	x = u.f;
+
+	if (e >= 0x3fff + 32) {
+		/* |x| >= 0x1p32 or inf or nan */
+		x = logl(x) + 0.693147180559945309417232121458176568L;
+	} else if (e >= 0x3fff + 1) {
+		/* |x| >= 2 */
+		x = logl(2*x + 1/(sqrtl(x*x+1)+x));
+	} else if (e >= 0x3fff - 32) {
+		/* |x| >= 0x1p-32 */
+		x = log1pl(x + x*x/(sqrtl(x*x+1)+1));
+	} else {
+		/* |x| < 0x1p-32, raise inexact if x!=0 */
+		FORCE_EVAL(x + 0x1p120f);
+	}
+	return s ? -x : x;
+}
+#elif LDBL_MANT_DIG == 113 && LDBL_MAX_EXP == 16384
+// TODO: broken implementation to make things compile
+long double asinhl(long double x)
+{
+	return asinh(x);
+}
+#endif