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

fusl/src/math/asinhf.c

+#include "libm.h"
+
+/* asinh(x) = sign(x)*log(|x|+sqrt(x*x+1)) ~= x - x^3/6 + o(x^5) */
+float asinhf(float x)
+{
+        union {float f; uint32_t i;} u = {.f = x};
+        uint32_t i = u.i & 0x7fffffff;
+        unsigned s = u.i >> 31;
+
+        /* |x| */
+        u.i = i;
+        x = u.f;
+
+        if (i >= 0x3f800000 + (12<<23)) {
+                /* |x| >= 0x1p12 or inf or nan */
+                x = logf(x) + 0.693147180559945309417232121458176568f;
+        } else if (i >= 0x3f800000 + (1<<23)) {
+                /* |x| >= 2 */
+                x = logf(2*x + 1/(sqrtf(x*x+1)+x));
+        } else if (i >= 0x3f800000 - (12<<23)) {
+                /* |x| >= 0x1p-12, up to 1.6ulp error in [0.125,0.5] */
+                x = log1pf(x + x*x/(sqrtf(x*x+1)+1));
+        } else {
+                /* |x| < 0x1p-12, raise inexact if x!=0 */
+                FORCE_EVAL(x + 0x1p120f);
+        }
+        return s ? -x : x;
+}