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

fusl/src/string/memcpy.c

Index: fusl/src/string/memcpy.c
diff --git a/fusl/src/string/memcpy.c b/fusl/src/string/memcpy.c
new file mode 100644
index 0000000000000000000000000000000000000000..06e88742b1144a3b770184cc34dc14d96bdd2134
--- /dev/null
+++ b/fusl/src/string/memcpy.c
@@ -0,0 +1,124 @@
+#include <string.h>
+#include <stdint.h>
+#include <endian.h>
+
+void *memcpy(void *restrict dest, const void *restrict src, size_t n)
+{
+	unsigned char *d = dest;
+	const unsigned char *s = src;
+
+#ifdef __GNUC__
+
+#if __BYTE_ORDER == __LITTLE_ENDIAN
+#define LS >>
+#define RS <<
+#else
+#define LS <<
+#define RS >>
+#endif
+
+	typedef uint32_t __attribute__((__may_alias__)) u32;
+	uint32_t w, x;
+
+	for (; (uintptr_t)s % 4 && n; n--) *d++ = *s++;
+
+	if ((uintptr_t)d % 4 == 0) {
+		for (; n>=16; s+=16, d+=16, n-=16) {
+			*(u32 *)(d+0) = *(u32 *)(s+0);
+			*(u32 *)(d+4) = *(u32 *)(s+4);
+			*(u32 *)(d+8) = *(u32 *)(s+8);
+			*(u32 *)(d+12) = *(u32 *)(s+12);
+		}
+		if (n&8) {
+			*(u32 *)(d+0) = *(u32 *)(s+0);
+			*(u32 *)(d+4) = *(u32 *)(s+4);
+			d += 8; s += 8;
+		}
+		if (n&4) {
+			*(u32 *)(d+0) = *(u32 *)(s+0);
+			d += 4; s += 4;
+		}
+		if (n&2) {
+			*d++ = *s++; *d++ = *s++;
+		}
+		if (n&1) {
+			*d = *s;
+		}
+		return dest;
+	}
+
+	if (n >= 32) switch ((uintptr_t)d % 4) {
+	case 1:
+		w = *(u32 *)s;
+		*d++ = *s++;
+		*d++ = *s++;
+		*d++ = *s++;
+		n -= 3;
+		for (; n>=17; s+=16, d+=16, n-=16) {
+			x = *(u32 *)(s+1);
+			*(u32 *)(d+0) = (w LS 24) | (x RS 8);
+			w = *(u32 *)(s+5);
+			*(u32 *)(d+4) = (x LS 24) | (w RS 8);
+			x = *(u32 *)(s+9);
+			*(u32 *)(d+8) = (w LS 24) | (x RS 8);
+			w = *(u32 *)(s+13);
+			*(u32 *)(d+12) = (x LS 24) | (w RS 8);
+		}
+		break;
+	case 2:
+		w = *(u32 *)s;
+		*d++ = *s++;
+		*d++ = *s++;
+		n -= 2;
+		for (; n>=18; s+=16, d+=16, n-=16) {
+			x = *(u32 *)(s+2);
+			*(u32 *)(d+0) = (w LS 16) | (x RS 16);
+			w = *(u32 *)(s+6);
+			*(u32 *)(d+4) = (x LS 16) | (w RS 16);
+			x = *(u32 *)(s+10);
+			*(u32 *)(d+8) = (w LS 16) | (x RS 16);
+			w = *(u32 *)(s+14);
+			*(u32 *)(d+12) = (x LS 16) | (w RS 16);
+		}
+		break;
+	case 3:
+		w = *(u32 *)s;
+		*d++ = *s++;
+		n -= 1;
+		for (; n>=19; s+=16, d+=16, n-=16) {
+			x = *(u32 *)(s+3);
+			*(u32 *)(d+0) = (w LS 8) | (x RS 24);
+			w = *(u32 *)(s+7);
+			*(u32 *)(d+4) = (x LS 8) | (w RS 24);
+			x = *(u32 *)(s+11);
+			*(u32 *)(d+8) = (w LS 8) | (x RS 24);
+			w = *(u32 *)(s+15);
+			*(u32 *)(d+12) = (x LS 8) | (w RS 24);
+		}
+		break;
+	}
+	if (n&16) {
+		*d++ = *s++; *d++ = *s++; *d++ = *s++; *d++ = *s++;
+		*d++ = *s++; *d++ = *s++; *d++ = *s++; *d++ = *s++;
+		*d++ = *s++; *d++ = *s++; *d++ = *s++; *d++ = *s++;
+		*d++ = *s++; *d++ = *s++; *d++ = *s++; *d++ = *s++;
+	}
+	if (n&8) {
+		*d++ = *s++; *d++ = *s++; *d++ = *s++; *d++ = *s++;
+		*d++ = *s++; *d++ = *s++; *d++ = *s++; *d++ = *s++;
+	}
+	if (n&4) {
+		*d++ = *s++; *d++ = *s++; *d++ = *s++; *d++ = *s++;
+	}
+	if (n&2) {
+		*d++ = *s++; *d++ = *s++;
+	}
+	if (n&1) {
+		*d = *s;
+	}
+	return dest;
+#endif
+
+	for (; n; n--) *d++ = *s++;
+	return dest;
+}