user: Translate the below assembly code into C programming language:

```asm
<M>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  mov    %rdi,-0x18(%rbp)
  movl   $0x0,-0x4(%rbp)
  jmp    L19
L25:
  mov    -0x4(%rbp),%eax
  cltq
  lea    0x4(%rax),%rdx
  mov    -0x18(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%ecx
  mov    -0x4(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x18(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%edx
  mov    -0x4(%rbp),%eax
  cltq
  lea    0x4(%rax),%rsi
  mov    -0x18(%rbp),%rax
  add    %rsi,%rax
  xor    %ecx,%edx
  mov    %dl,(%rax)
  mov    -0x4(%rbp),%eax
  cltq
  lea    0x5(%rax),%rdx
  mov    -0x18(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%ecx
  mov    -0x4(%rbp),%eax
  cltq
  lea    0x1(%rax),%rdx
  mov    -0x18(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%edx
  mov    -0x4(%rbp),%eax
  cltq
  lea    0x5(%rax),%rsi
  mov    -0x18(%rbp),%rax
  add    %rsi,%rax
  xor    %ecx,%edx
  mov    %dl,(%rax)
  mov    -0x4(%rbp),%eax
  cltq
  lea    0x6(%rax),%rdx
  mov    -0x18(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%ecx
  mov    -0x4(%rbp),%eax
  cltq
  lea    0x2(%rax),%rdx
  mov    -0x18(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%edx
  mov    -0x4(%rbp),%eax
  cltq
  lea    0x6(%rax),%rsi
  mov    -0x18(%rbp),%rax
  add    %rsi,%rax
  xor    %ecx,%edx
  mov    %dl,(%rax)
  mov    -0x4(%rbp),%eax
  cltq
  lea    0x7(%rax),%rdx
  mov    -0x18(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%ecx
  mov    -0x4(%rbp),%eax
  cltq
  lea    0x3(%rax),%rdx
  mov    -0x18(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%edx
  mov    -0x4(%rbp),%eax
  cltq
  lea    0x7(%rax),%rsi
  mov    -0x18(%rbp),%rax
  add    %rsi,%rax
  xor    %ecx,%edx
  mov    %dl,(%rax)
  addl   $0x8,-0x4(%rbp)
L19:
  cmpl   $0x1f,-0x4(%rbp)
  jle    L25
  movl   $0x0,-0x4(%rbp)
  jmp    L6
L24:
  mov    -0x4(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x18(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  mov    %al,-0x8(%rbp)
  mov    -0x4(%rbp),%eax
  cltq
  lea    0x8(%rax),%rdx
  mov    -0x18(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  mov    %al,-0x7(%rbp)
  mov    -0x4(%rbp),%eax
  cltq
  lea    0x10(%rax),%rdx
  mov    -0x18(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  mov    %al,-0x6(%rbp)
  mov    -0x4(%rbp),%eax
  cltq
  lea    0x18(%rax),%rdx
  mov    -0x18(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  mov    %al,-0x5(%rbp)
  movzbl -0x8(%rbp),%eax
  xor    -0x7(%rbp),%al
  mov    -0x4(%rbp),%edx
  movslq %edx,%rcx
  mov    -0x18(%rbp),%rdx
  add    %rcx,%rdx
  xor    -0x5(%rbp),%al
  mov    %al,(%rdx)
  movzbl -0x7(%rbp),%eax
  xor    -0x6(%rbp),%al
  mov    -0x4(%rbp),%edx
  movslq %edx,%rdx
  lea    0x8(%rdx),%rcx
  mov    -0x18(%rbp),%rdx
  add    %rcx,%rdx
  xor    -0x8(%rbp),%al
  mov    %al,(%rdx)
  movzbl -0x6(%rbp),%eax
  xor    -0x5(%rbp),%al
  mov    -0x4(%rbp),%edx
  movslq %edx,%rdx
  lea    0x10(%rdx),%rcx
  mov    -0x18(%rbp),%rdx
  add    %rcx,%rdx
  xor    -0x7(%rbp),%al
  mov    %al,(%rdx)
  movzbl -0x5(%rbp),%eax
  xor    -0x8(%rbp),%al
  mov    -0x4(%rbp),%edx
  movslq %edx,%rdx
  lea    0x18(%rdx),%rcx
  mov    -0x18(%rbp),%rdx
  add    %rcx,%rdx
  xor    -0x6(%rbp),%al
  mov    %al,(%rdx)
  addl   $0x1,-0x4(%rbp)
L6:
  cmpl   $0x7,-0x4(%rbp)
  jle    L24
  nop
  nop
  pop    %rbp
  ret
```

assistant: ```c
void M(unsigned char *_m_) {
  int i;
  unsigned char t0, t1, t2, t3;
  for (i = 0; i < 32; i += 8) {
    _m_[i + 4] ^= _m_[i];
    _m_[i + 5] ^= _m_[i + 1];
    _m_[i + 6] ^= _m_[i + 2];
    _m_[i + 7] ^= _m_[i + 3];
  }
  for (i = 0; i < 8; i++) {
    t0 = _m_[i];
    t1 = _m_[i + 8];
    t2 = _m_[i + 16];
    t3 = _m_[i + 24];
    _m_[i] = t0 ^ t1 ^ t3;
    _m_[i + 8] = t1 ^ t2 ^ t0;
    _m_[i + 16] = t2 ^ t3 ^ t1;
    _m_[i + 24] = t3 ^ t0 ^ t2;
  }
}
```