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

fusl/src/math/fmodl.c

+#include "libm.h"
+
+#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
+long double fmodl(long double x, long double y)
+{
+        return fmod(x, y);
+}
+#elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384
+long double fmodl(long double x, long double y)
+{
+        union ldshape ux = {x}, uy = {y};
+        int ex = ux.i.se & 0x7fff;
+        int ey = uy.i.se & 0x7fff;
+        int sx = ux.i.se & 0x8000;
+
+        if (y == 0 || isnan(y) || ex == 0x7fff)
+                return (x*y)/(x*y);
+        ux.i.se = ex;
+        uy.i.se = ey;
+        if (ux.f <= uy.f) {
+                if (ux.f == uy.f)
+                        return 0*x;
+                return x;
+        }
+
+        /* normalize x and y */
+        if (!ex) {
+                ux.f *= 0x1p120f;
+                ex = ux.i.se - 120;
+        }
+        if (!ey) {
+                uy.f *= 0x1p120f;
+                ey = uy.i.se - 120;
+        }
+
+        /* x mod y */
+#if LDBL_MANT_DIG == 64
+        uint64_t i, mx, my;
+        mx = ux.i.m;
+        my = uy.i.m;
+        for (; ex > ey; ex--) {
+                i = mx - my;
+                if (mx >= my) {
+                        if (i == 0)
+                                return 0*x;
+                        mx = 2*i;
+                } else if (2*mx < mx) {
+                        mx = 2*mx - my;
+                } else {
+                        mx = 2*mx;
+                }
+        }
+        i = mx - my;
+        if (mx >= my) {
+                if (i == 0)
+                        return 0*x;
+                mx = i;
+        }
+        for (; mx >> 63 == 0; mx *= 2, ex--);
+        ux.i.m = mx;
+#elif LDBL_MANT_DIG == 113
+        uint64_t hi, lo, xhi, xlo, yhi, ylo;
+        xhi = (ux.i2.hi & -1ULL>>16) | 1ULL<<48;
+        yhi = (uy.i2.hi & -1ULL>>16) | 1ULL<<48;
+        xlo = ux.i2.lo;
+        ylo = uy.i2.lo;
+        for (; ex > ey; ex--) {
+                hi = xhi - yhi;
+                lo = xlo - ylo;
+                if (xlo < ylo)
+                        hi -= 1;
+                if (hi >> 63 == 0) {
+                        if ((hi|lo) == 0)
+                                return 0*x;
+                        xhi = 2*hi + (lo>>63);
+                        xlo = 2*lo;
+                } else {
+                        xhi = 2*xhi + (xlo>>63);
+                        xlo = 2*xlo;
+                }
+        }
+        hi = xhi - yhi;
+        lo = xlo - ylo;
+        if (xlo < ylo)
+                hi -= 1;
+        if (hi >> 63 == 0) {
+                if ((hi|lo) == 0)
+                        return 0*x;
+                xhi = hi;
+                xlo = lo;
+        }
+        for (; xhi >> 48 == 0; xhi = 2*xhi + (xlo>>63), xlo = 2*xlo, ex--);
+        ux.i2.hi = xhi;
+        ux.i2.lo = xlo;
+#endif
+
+        /* scale result */
+        if (ex <= 0) {
+                ux.i.se = (ex+120)|sx;
+                ux.f *= 0x1p-120f;
+        } else
+                ux.i.se = ex|sx;
+        return ux.f;
+}
+#endif