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

fusl/src/math/asinf.c

Index: fusl/src/math/asinf.c
diff --git a/fusl/src/math/asinf.c b/fusl/src/math/asinf.c
new file mode 100644
index 0000000000000000000000000000000000000000..bcd304a3425991689cbf14dd1cd575a43a8b1117
--- /dev/null
+++ b/fusl/src/math/asinf.c
@@ -0,0 +1,61 @@
+/* origin: FreeBSD /usr/src/lib/msun/src/e_asinf.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 double
+pio2 = 1.570796326794896558e+00;
+
+static const float
+/* coefficients for R(x^2) */
+pS0 =  1.6666586697e-01,
+pS1 = -4.2743422091e-02,
+pS2 = -8.6563630030e-03,
+qS1 = -7.0662963390e-01;
+
+static float R(float z)
+{
+	float_t p, q;
+	p = z*(pS0+z*(pS1+z*pS2));
+	q = 1.0f+z*qS1;
+	return p/q;
+}
+
+float asinf(float x)
+{
+	double s;
+	float z;
+	uint32_t hx,ix;
+
+	GET_FLOAT_WORD(hx, x);
+	ix = hx & 0x7fffffff;
+	if (ix >= 0x3f800000) {  /* |x| >= 1 */
+		if (ix == 0x3f800000)  /* |x| == 1 */
+			return x*pio2 + 0x1p-120f;  /* asin(+-1) = +-pi/2 with inexact */
+		return 0/(x-x);  /* asin(|x|>1) is NaN */
+	}
+	if (ix < 0x3f000000) {  /* |x| < 0.5 */
+		/* if 0x1p-126 <= |x| < 0x1p-12, avoid raising underflow */
+		if (ix < 0x39800000 && ix >= 0x00800000)
+			return x;
+		return x + x*R(x*x);
+	}
+	/* 1 > |x| >= 0.5 */
+	z = (1 - fabsf(x))*0.5f;
+	s = sqrt(z);
+	x = pio2 - 2*(s+s*R(z));
+	if (hx >> 31)
+		return -x;
+	return x;
+}