user: 下面的汇编指令对应的C源代码是什么：

```asm
<memcpy>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  mov    %rdi,-0x38(%rbp)
  mov    %rsi,-0x40(%rbp)
  mov    %rdx,-0x48(%rbp)
  mov    -0x40(%rbp),%rax
  mov    %rax,-0x18(%rbp)
  mov    -0x48(%rbp),%rax
  shr    $0x3,%rax
  mov    %rax,-0x28(%rbp)
  subq   $0x4,-0x18(%rbp)
  mov    -0x38(%rbp),%rax
  sub    $0x4,%rax
  mov    %rax,-0x20(%rbp)
  cmpq   $0x0,-0x28(%rbp)
  je     L88
  mov    -0x20(%rbp),%rax
  and    $0x3,%eax
  mov    %rax,-0x30(%rbp)
  cmpq   $0x0,-0x30(%rbp)
  jne    L1
  nop
L93:
  mov    -0x18(%rbp),%rax
  mov    0x4(%rax),%rax
  mov    %rax,-0x10(%rbp)
  addq   $0x8,-0x18(%rbp)
  mov    -0x18(%rbp),%rax
  mov    (%rax),%rax
  mov    %rax,-0x8(%rbp)
  mov    -0x20(%rbp),%rax
  lea    0x4(%rax),%rdx
  mov    -0x10(%rbp),%rax
  mov    %rax,(%rdx)
  addq   $0x8,-0x20(%rbp)
  mov    -0x20(%rbp),%rax
  mov    -0x8(%rbp),%rdx
  mov    %rdx,(%rax)
  subq   $0x1,-0x28(%rbp)
  cmpq   $0x0,-0x28(%rbp)
  jne    L93
  jmp    L21
L88:
  nop
  jmp    L21
L112:
  nop
L21:
  andq   $0x7,-0x48(%rbp)
  cmpq   $0x3,-0x48(%rbp)
  jbe    L13
  addq   $0x4,-0x18(%rbp)
  addq   $0x4,-0x20(%rbp)
  mov    -0x18(%rbp),%rax
  mov    (%rax),%rdx
  mov    -0x20(%rbp),%rax
  mov    %rdx,(%rax)
  subq   $0x4,-0x48(%rbp)
L13:
  cmpq   $0x0,-0x48(%rbp)
  jne    L2
  mov    -0x38(%rbp),%rax
  jmp    L91
L2:
  addq   $0x3,-0x18(%rbp)
  addq   $0x3,-0x20(%rbp)
L52:
  addq   $0x1,-0x18(%rbp)
  addq   $0x1,-0x20(%rbp)
  mov    -0x18(%rbp),%rax
  movzbl (%rax),%edx
  mov    -0x20(%rbp),%rax
  mov    %dl,(%rax)
  subq   $0x1,-0x48(%rbp)
  cmpq   $0x0,-0x48(%rbp)
  jne    L52
  mov    -0x38(%rbp),%rax
  jmp    L91
L1:
  nop
  mov    $0x4,%eax
  sub    -0x30(%rbp),%rax
  mov    %rax,-0x30(%rbp)
  mov    -0x30(%rbp),%rax
  sub    %rax,-0x48(%rbp)
L129:
  mov    -0x20(%rbp),%rax
  lea    0x4(%rax),%rdx
  mov    -0x18(%rbp),%rax
  movzbl 0x4(%rax),%eax
  mov    %al,(%rdx)
  addq   $0x1,-0x18(%rbp)
  addq   $0x1,-0x20(%rbp)
  subq   $0x1,-0x30(%rbp)
  cmpq   $0x0,-0x30(%rbp)
  jne    L129
  mov    -0x48(%rbp),%rax
  shr    $0x3,%rax
  mov    %rax,-0x28(%rbp)
  cmpq   $0x0,-0x28(%rbp)
  je     L112
  jmp    L93
L91:
  pop    %rbp
  ret
```

assistant: ```c
void *memcpy(void *to, const void *from, size_t len) {
  unsigned long rem, chunks, tmp1, tmp2;
  unsigned char *tmp_to;
  unsigned char *tmp_from = (unsigned char *)from;
  chunks = len / 8;
  tmp_from -= 4;
  tmp_to = to - 4;
  if (!chunks)
    goto lessthan8;
  rem = (unsigned long)tmp_to % 4;
  if (rem)
    goto align;
copy_chunks:
  do {
    tmp1 = *(unsigned long *)(tmp_from + 4);
    tmp_from += 8;
    tmp2 = *(unsigned long *)tmp_from;
    *(unsigned long *)(tmp_to + 4) = tmp1;
    tmp_to += 8;
    *(unsigned long *)tmp_to = tmp2;
  } while (--chunks);
lessthan8:
  len = len % 8;
  if (len >= 4) {
    tmp_from += 4;
    tmp_to += 4;
    *(unsigned long *)(tmp_to) = *(unsigned long *)(tmp_from);
    len -= 4;
  }
  if (!len)
    return to;
  tmp_from += 3;
  tmp_to += 3;
  do {
    *++tmp_to = *++tmp_from;
  } while (--len);
  return to;
align:
  rem = 4 - rem;
  len -= rem;
  do {
    *(tmp_to + 4) = *(tmp_from + 4);
    ++tmp_from;
    ++tmp_to;
  } while (--rem);
  chunks = len / 8;
  if (chunks)
    goto copy_chunks;
  goto lessthan8;
}
```