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

fusl/src/math/hypotl.c

Index: fusl/src/math/hypotl.c
diff --git a/fusl/src/math/hypotl.c b/fusl/src/math/hypotl.c
new file mode 100644
index 0000000000000000000000000000000000000000..479aa92c3dc29b235c8f6200863f73d22cd1fcef
--- /dev/null
+++ b/fusl/src/math/hypotl.c
@@ -0,0 +1,66 @@
+#include "libm.h"
+
+#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
+long double hypotl(long double x, long double y)
+{
+	return hypot(x, y);
+}
+#elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384
+#if LDBL_MANT_DIG == 64
+#define SPLIT (0x1p32L+1)
+#elif LDBL_MANT_DIG == 113
+#define SPLIT (0x1p57L+1)
+#endif
+
+static void sq(long double *hi, long double *lo, long double x)
+{
+	long double xh, xl, xc;
+	xc = x*SPLIT;
+	xh = x - xc + xc;
+	xl = x - xh;
+	*hi = x*x;
+	*lo = xh*xh - *hi + 2*xh*xl + xl*xl;
+}
+
+long double hypotl(long double x, long double y)
+{
+	union ldshape ux = {x}, uy = {y};
+	int ex, ey;
+	long double hx, lx, hy, ly, z;
+
+	ux.i.se &= 0x7fff;
+	uy.i.se &= 0x7fff;
+	if (ux.i.se < uy.i.se) {
+		ex = uy.i.se;
+		ey = ux.i.se;
+		x = uy.f;
+		y = ux.f;
+	} else {
+		ex = ux.i.se;
+		ey = uy.i.se;
+		x = ux.f;
+		y = uy.f;
+	}
+
+	if (ex == 0x7fff && isinf(y))
+		return y;
+	if (ex == 0x7fff || y == 0)
+		return x;
+	if (ex - ey > LDBL_MANT_DIG)
+		return x + y;
+
+	z = 1;
+	if (ex > 0x3fff+8000) {
+		z = 0x1p10000L;
+		x *= 0x1p-10000L;
+		y *= 0x1p-10000L;
+	} else if (ey < 0x3fff-8000) {
+		z = 0x1p-10000L;
+		x *= 0x1p10000L;
+		y *= 0x1p10000L;
+	}
+	sq(&hx, &lx, x);
+	sq(&hy, &ly, y);
+	return z*sqrtl(ly+lx+hy+hx);
+}
+#endif