user: 提供的汇编代码用C语言表示会是什么样子:

```asm
<clean>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  push   %r15
  push   %r14
  push   %r12
  push   %rbx
  sub    $0x50,%rsp
  mov    %rdi,-0x58(%rbp)
  mov    %fs:0x28,%rax
  mov    %rax,-0x28(%rbp)
  xor    %eax,%eax
  mov    -0x58(%rbp),%rax
  mov    %rax,%rdi
  call   <strlen@plt>
  mov    %eax,-0x44(%rbp)
  cmpl   $0x0,-0x44(%rbp)
  jne    L73
  mov    $0x8,%edi
  call   <malloc@plt>
  mov    %rax,-0x40(%rbp)
  mov    -0x40(%rbp),%rax
  movb   $0x0,(%rax)
  mov    -0x40(%rbp),%rax
  jmp    L33
L73:
  mov    %rsp,%rax
  mov    %rax,%r12
  mov    -0x44(%rbp),%eax
  cltq
  shl    $0x3,%eax
  mov    %eax,%edi
  call   <malloc@plt>
  mov    %rax,-0x40(%rbp)
  mov    -0x44(%rbp),%eax
  movslq %eax,%rdx
  sub    $0x1,%rdx
  mov    %rdx,-0x38(%rbp)
  movslq %eax,%rdx
  mov    %rdx,-0x70(%rbp)
  movq   $0x0,-0x68(%rbp)
  movslq %eax,%rdx
  mov    %rdx,%r14
  mov    $0x0,%r15d
  cltq
  mov    $0x10,%edx
  sub    $0x1,%rdx
  add    %rdx,%rax
  mov    $0x10,%esi
  mov    $0x0,%edx
  div    %rsi
  imul   $0x10,%rax,%rax
  mov    %rax,%rcx
  and    $0xfffffffffffff000,%rcx
  mov    %rsp,%rdx
  sub    %rcx,%rdx
L29:
  cmp    %rdx,%rsp
  je     L86
  sub    $0x1000,%rsp
  orq    $0x0,0xff8(%rsp)
  jmp    L29
L86:
  mov    %rax,%rdx
  and    $0xfff,%edx
  sub    %rdx,%rsp
  mov    %rax,%rdx
  and    $0xfff,%edx
  test   %rdx,%rdx
  je     L84
  and    $0xfff,%eax
  sub    $0x8,%rax
  add    %rsp,%rax
  orq    $0x0,(%rax)
L84:
  mov    %rsp,%rax
  add    $0x0,%rax
  mov    %rax,-0x30(%rbp)
  movl   $0x0,-0x4c(%rbp)
  movl   $0x0,-0x48(%rbp)
  jmp    L103
L61:
  mov    -0x48(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x58(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  movsbl %al,%eax
  mov    %eax,%edi
  call   <isalpha@plt>
  test   %rax,%rax
  je     L138
  mov    -0x48(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x58(%rbp),%rax
  lea    (%rdx,%rax,1),%rcx
  mov    -0x4c(%rbp),%eax
  lea    0x1(%rax),%edx
  mov    %edx,-0x4c(%rbp)
  movzbl (%rcx),%ecx
  mov    -0x30(%rbp),%rdx
  cltq
  mov    %cl,(%rdx,%rax,1)
L138:
  addl   $0x1,-0x48(%rbp)
L103:
  mov    -0x48(%rbp),%eax
  cmp    -0x44(%rbp),%eax
  jl     L61
  mov    -0x4c(%rbp),%eax
  cmp    -0x44(%rbp),%eax
  jne    L46
  movl   $0x0,-0x48(%rbp)
  jmp    L62
L50:
  mov    -0x48(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x58(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  movsbl %al,%eax
  mov    -0x48(%rbp),%edx
  movslq %edx,%rcx
  mov    -0x40(%rbp),%rdx
  lea    (%rcx,%rdx,1),%rbx
  mov    %eax,%edi
  call   <toupper@plt>
  mov    %al,(%rbx)
  addl   $0x1,-0x48(%rbp)
L62:
  mov    -0x48(%rbp),%eax
  cmp    -0x44(%rbp),%eax
  jl     L50
  jmp    L101
L46:
  movl   $0x0,-0x48(%rbp)
  jmp    L125
L11:
  mov    -0x30(%rbp),%rdx
  mov    -0x48(%rbp),%eax
  cltq
  movzbl (%rdx,%rax,1),%eax
  movsbl %al,%eax
  mov    -0x48(%rbp),%edx
  movslq %edx,%rcx
  mov    -0x40(%rbp),%rdx
  lea    (%rcx,%rdx,1),%rbx
  mov    %eax,%edi
  call   <toupper@plt>
  mov    %al,(%rbx)
  addl   $0x1,-0x48(%rbp)
L125:
  mov    -0x48(%rbp),%eax
  cmp    -0x4c(%rbp),%eax
  jl     L11
L101:
  mov    %r12,%rsp
  mov    -0x40(%rbp),%rax
L33:
  mov    -0x28(%rbp),%rdx
  sub    %fs:0x28,%rdx
  je     L57
  call   <__stack_chk_fail@plt>
L57:
  lea    -0x20(%rbp),%rsp
  pop    %rbx
  pop    %r12
  pop    %r14
  pop    %r15
  pop    %rbp
  ret
```

assistant: ```c
char *clean(const char *str) {
  int len = strlen(str);
  char *res;
  if (len == 0) {
    res = malloc(sizeof(str));
    res[0] = '\0';
    return (res);
  } else {
    res = malloc(sizeof(str) * len);
    char chars[len];
    int cnt = 0, i;
    for (i = 0; i < len; i++) {
      if (isalpha(str[i])) {
        chars[cnt++] = str[i];
      }
    }
    if (cnt == len) {
      for (i = 0; i < len; i++) {
        res[i] = toupper(str[i]);
      }
    } else {
      for (i = 0; i < cnt; i++) {
        res[i] = toupper(chars[i]);
      }
    }
  }
  return (res);
}
```