user: 这段汇编代码用C语言表示是什么样的：

```asm
<memcpy>:
  endbr64
  mov    %rdi,%r8
  mov    %rdx,%rax
  test   $0x3,%sil
  je     L27
  test   %rdx,%rdx
  jne    L268
  jmp    L45
  nopw   0x0(%rax,%rax,1)
L2:
  test   %rax,%rax
  je     L45
L268:
  movsb  %ds:(%rsi),%es:(%rdi)
  sub    $0x1,%rax
  test   $0x3,%sil
  jne    L2
L27:
  mov    %rdi,%rcx
  and    $0x3,%ecx
  je     L149
  push   %rbp
  push   %rbx
  cmp    $0x1f,%rax
  jbe    L253
  movzbl (%rsi),%edx
  mov    (%rsi),%r9d
  cmp    $0x2,%rcx
  je     L180
  cmp    $0x3,%rcx
  je     L288
  movzbl 0x2(%rsi),%edx
  movzwl (%rsi),%ecx
  lea    -0x14(%rax),%rbp
  lea    0x3(%rsi),%r11
  mov    %rbp,%r10
  lea    0x3(%rdi),%rbx
  and    $0xfffffffffffffff0,%rbp
  mov    %cx,(%rdi)
  shr    $0x4,%r10
  lea    0x13(%rdi,%rbp,1),%rsi
  mov    %rbx,%rcx
  mov    %dl,0x2(%rdi)
  mov    %r11,%rdx
  nopl   (%rax)
L73:
  movd   0x5(%rdx),%xmm1
  movd   0x9(%rdx),%xmm3
  movd   %r9d,%xmm0
  add    $0x10,%rcx
  movd   0x1(%rdx),%xmm4
  mov    0xd(%rdx),%r9d
  add    $0x10,%rdx
  punpckldq %xmm3,%xmm1
  punpckldq %xmm4,%xmm0
  punpcklqdq %xmm1,%xmm0
  movdqu -0xf(%rdx),%xmm1
  psrad  $0x18,%xmm0
  pslld  $0x8,%xmm1
  por    %xmm1,%xmm0
  movups %xmm0,-0x10(%rcx)
  cmp    %rsi,%rcx
  jne    L73
  sub    $0x13,%rax
L101:
  lea    0x1(%r10),%rsi
  sub    %rbp,%rax
  shl    $0x4,%rsi
  lea    (%rbx,%rsi,1),%rdi
  add    %r11,%rsi
L253:
  mov    %rax,%rcx
  mov    %rax,%rdx
  mov    %rax,%r10
  mov    %rax,%r9
  and    $0x8,%ecx
  and    $0x4,%edx
  and    $0x2,%r10d
  and    $0x1,%r9d
  test   $0x10,%al
  je     L76
  movdqu (%rsi),%xmm4
  lea    0x10(%rdi),%rax
  add    $0x10,%rsi
  movups %xmm4,(%rdi)
L21:
  test   %rcx,%rcx
  je     L174
  mov    (%rsi),%rdi
  lea    0x8(%rax),%rcx
  add    $0x8,%rsi
  mov    %rdi,(%rax)
L223:
  test   %rdx,%rdx
  je     L286
  lea    0x4(%rsi),%rdx
  mov    (%rsi),%esi
  lea    0x4(%rcx),%rax
  mov    %esi,(%rcx)
L196:
  test   %r10,%r10
  je     L42
  lea    0x2(%rdx),%rsi
  movzwl (%rdx),%edx
  lea    0x2(%rax),%rcx
  mov    %dx,(%rax)
L284:
  test   %r9,%r9
  je     L255
  movzbl (%rsi),%eax
  mov    %al,(%rcx)
L255:
  mov    %r8,%rax
  pop    %rbx
  pop    %rbp
  ret
  nopw   0x0(%rax,%rax,1)
L149:
  cmp    $0xf,%rax
  jbe    L105
  lea    -0x10(%rax),%r9
  xor    %edx,%edx
  shr    $0x4,%r9
  add    $0x1,%r9
  nopl   0x0(%rax)
L41:
  movdqu (%rsi,%rdx,1),%xmm2
  add    $0x1,%rcx
  movups %xmm2,(%rdi,%rdx,1)
  add    $0x10,%rdx
  cmp    %r9,%rcx
  jb     L41
  shl    $0x4,%r9
  and    $0xf,%eax
  add    %r9,%rdi
  add    %r9,%rsi
L105:
  mov    %rax,%r9
  mov    %rax,%rdx
  mov    %rax,%rcx
  and    $0x4,%r9d
  and    $0x2,%edx
  and    $0x1,%ecx
  test   $0x8,%al
  je     L79
  mov    (%rsi),%rax
  add    $0x8,%rdi
  add    $0x8,%rsi
  mov    %rax,-0x8(%rdi)
L79:
  test   %r9,%r9
  je     L34
  mov    (%rsi),%eax
  add    $0x4,%rdi
  add    $0x4,%rsi
  mov    %eax,-0x4(%rdi)
L34:
  test   %rdx,%rdx
  je     L189
  lea    0x2(%rsi),%rdx
  movzwl (%rsi),%esi
  lea    0x2(%rdi),%rax
  mov    %si,(%rdi)
L205:
  test   %rcx,%rcx
  je     L45
  movzbl (%rdx),%edx
  mov    %dl,(%rax)
L45:
  mov    %r8,%rax
  ret
  nopl   0x0(%rax,%rax,1)
L288:
  lea    -0x14(%rax),%r11
  lea    0x1(%rdi),%rbx
  add    $0x1,%rsi
  mov    %dl,(%rdi)
  mov    %r11,%r10
  and    $0xfffffffffffffff0,%r11
  mov    %rsi,%rdx
  mov    %rbx,%rcx
  shr    $0x4,%r10
  lea    0x11(%rdi,%r11,1),%rdi
  nopl   0x0(%rax)
L216:
  movd   0x7(%rdx),%xmm1
  movd   0xb(%rdx),%xmm7
  movd   %r9d,%xmm0
  add    $0x10,%rcx
  movd   0x3(%rdx),%xmm3
  mov    0xf(%rdx),%r9d
  add    $0x10,%rdx
  punpckldq %xmm7,%xmm1
  punpckldq %xmm3,%xmm0
  punpcklqdq %xmm1,%xmm0
  movdqu -0xd(%rdx),%xmm1
  psrad  $0x8,%xmm0
  pslld  $0x18,%xmm1
  por    %xmm1,%xmm0
  movups %xmm0,-0x10(%rcx)
  cmp    %rdi,%rcx
  jne    L216
  lea    0x1(%r10),%rdx
  sub    $0x11,%rax
  shl    $0x4,%rdx
  sub    %r11,%rax
  lea    (%rbx,%rdx,1),%rdi
  add    %rdx,%rsi
  jmp    L253
  nopl   0x0(%rax,%rax,1)
L180:
  movzwl (%rsi),%edx
  lea    -0x14(%rax),%rbp
  lea    0x2(%rsi),%r11
  mov    %rbp,%r10
  lea    0x2(%rdi),%rbx
  and    $0xfffffffffffffff0,%rbp
  mov    %dx,(%rdi)
  shr    $0x4,%r10
  lea    0x12(%rdi,%rbp,1),%rsi
  mov    %r11,%rdx
  mov    %rbx,%rcx
  nopl   0x0(%rax,%rax,1)
L220:
  movd   0x6(%rdx),%xmm1
  movd   0xa(%rdx),%xmm5
  movd   %r9d,%xmm0
  add    $0x10,%rcx
  movd   0x2(%rdx),%xmm6
  mov    0xe(%rdx),%r9d
  add    $0x10,%rdx
  punpckldq %xmm5,%xmm1
  punpckldq %xmm6,%xmm0
  punpcklqdq %xmm1,%xmm0
  movdqu -0xe(%rdx),%xmm1
  psrad  $0x10,%xmm0
  pslld  $0x10,%xmm1
  por    %xmm1,%xmm0
  movups %xmm0,-0x10(%rcx)
  cmp    %rsi,%rcx
  jne    L220
  sub    $0x12,%rax
  jmp    L101
L42:
  mov    %rdx,%rsi
  mov    %rax,%rcx
  jmp    L284
L174:
  mov    %rax,%rcx
  jmp    L223
L286:
  mov    %rsi,%rdx
  mov    %rcx,%rax
  jmp    L196
L76:
  mov    %rdi,%rax
  jmp    L21
L189:
  mov    %rsi,%rdx
  mov    %rdi,%rax
  jmp    L205
```

assistant: ```c
void *memcpy(void *restrict dest, const void *restrict src, size_t n) {
  unsigned char *d = dest;
  const unsigned char *s = src;
  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 >> 24) | (x << 8);
        w = *(u32 *)(s + 5);
        *(u32 *)(d + 4) = (x >> 24) | (w << 8);
        x = *(u32 *)(s + 9);
        *(u32 *)(d + 8) = (w >> 24) | (x << 8);
        w = *(u32 *)(s + 13);
        *(u32 *)(d + 12) = (x >> 24) | (w << 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 >> 16) | (x << 16);
        w = *(u32 *)(s + 6);
        *(u32 *)(d + 4) = (x >> 16) | (w << 16);
        x = *(u32 *)(s + 10);
        *(u32 *)(d + 8) = (w >> 16) | (x << 16);
        w = *(u32 *)(s + 14);
        *(u32 *)(d + 12) = (x >> 16) | (w << 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 >> 8) | (x << 24);
        w = *(u32 *)(s + 7);
        *(u32 *)(d + 4) = (x >> 8) | (w << 24);
        x = *(u32 *)(s + 11);
        *(u32 *)(d + 8) = (w >> 8) | (x << 24);
        w = *(u32 *)(s + 15);
        *(u32 *)(d + 12) = (x >> 8) | (w << 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;
}
```