#include "asan_impl.h"
#include "libc.h"
#include <endian.h>
#include <stdint.h>
#include <string.h>

NO_ASAN 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;
}

__typeof(memcpy) __unsanitized_memcpy __attribute__((alias("memcpy")));
__asan_weak_alias(memcpy)