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

fusl/src/math/sincosl.c

Index: fusl/src/math/sincosl.c
diff --git a/fusl/src/math/sincosl.c b/fusl/src/math/sincosl.c
new file mode 100644
index 0000000000000000000000000000000000000000..d3ac1c4c8c29e11067d55a3a99fa82eb888c5dd5
--- /dev/null
+++ b/fusl/src/math/sincosl.c
@@ -0,0 +1,60 @@
+#define _GNU_SOURCE
+#include "libm.h"
+
+#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
+void sincosl(long double x, long double *sin, long double *cos)
+{
+	double sind, cosd;
+	sincos(x, &sind, &cosd);
+	*sin = sind;
+	*cos = cosd;
+}
+#elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384
+void sincosl(long double x, long double *sin, long double *cos)
+{
+	union ldshape u = {x};
+	unsigned n;
+	long double y[2], s, c;
+
+	u.i.se &= 0x7fff;
+	if (u.i.se == 0x7fff) {
+		*sin = *cos = x - x;
+		return;
+	}
+	if (u.f < M_PI_4) {
+		if (u.i.se < 0x3fff - LDBL_MANT_DIG) {
+			/* raise underflow if subnormal */
+			if (u.i.se == 0) FORCE_EVAL(x*0x1p-120f);
+			*sin = x;
+			/* raise inexact if x!=0 */
+			*cos = 1.0 + x;
+			return;
+		}
+		*sin = __sinl(x, 0, 0);
+		*cos = __cosl(x, 0);
+		return;
+	}
+	n = __rem_pio2l(x, y);
+	s = __sinl(y[0], y[1], 1);
+	c = __cosl(y[0], y[1]);
+	switch (n & 3) {
+	case 0:
+		*sin = s;
+		*cos = c;
+		break;
+	case 1:
+		*sin = c;
+		*cos = -s;
+		break;
+	case 2:
+		*sin = -s;
+		*cos = -c;
+		break;
+	case 3:
+	default:
+		*sin = -c;
+		*cos = s;
+		break;
+	}
+}
+#endif