user: 提供的汇编代码用C语言表示会是什么样子:

```asm
<find_tag_var_start>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  mov    %rdi,-0x28(%rbp)
  mov    %rsi,-0x30(%rbp)
  cmpq   $0x0,-0x28(%rbp)
  je     L309
  cmpq   $0x0,-0x30(%rbp)
  jne    L227
L309:
  mov    $0xffffffff,%eax
  jmp    L213
L227:
  movl   $0x0,-0x1c(%rbp)
L254:
  mov    -0x1c(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x28(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  movsbl %al,%eax
  and    $0xff,%eax
  mov    %eax,-0xc(%rbp)
  cmpl   $0x0,-0xc(%rbp)
  jne    L31
  mov    $0xffffffff,%eax
  jmp    L213
L31:
  cmpl   $0x20,-0xc(%rbp)
  ja     L269
  nop
  addl   $0x1,-0x1c(%rbp)
  jmp    L254
L269:
  nop
  movl   $0x0,-0x18(%rbp)
L17:
  mov    -0x18(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x30(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  movsbl %al,%eax
  and    $0xff,%eax
  mov    %eax,-0x14(%rbp)
  mov    -0x1c(%rbp),%edx
  mov    -0x18(%rbp),%eax
  add    %edx,%eax
  movslq %eax,%rdx
  mov    -0x28(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  movsbl %al,%eax
  and    $0xff,%eax
  mov    %eax,-0x10(%rbp)
  cmpl   $0x0,-0x14(%rbp)
  je     L120
  cmpl   $0x0,-0x10(%rbp)
  jne    L132
  mov    $0xffffffff,%eax
  jmp    L213
L132:
  cmpl   $0x40,-0x14(%rbp)
  jbe    L218
  cmpl   $0x5a,-0x14(%rbp)
  ja     L218
  subl   $0x41,-0x14(%rbp)
  addl   $0x61,-0x14(%rbp)
L218:
  cmpl   $0x40,-0x10(%rbp)
  jbe    L115
  cmpl   $0x5a,-0x10(%rbp)
  ja     L115
  subl   $0x41,-0x10(%rbp)
  addl   $0x61,-0x10(%rbp)
L115:
  mov    -0x10(%rbp),%eax
  cmp    -0x14(%rbp),%eax
  jne    L290
  addl   $0x1,-0x18(%rbp)
  jmp    L17
L120:
  nop
  jmp    L238
L290:
  nop
L238:
  mov    -0x18(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x30(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  test   %al,%al
  jne    L22
L161:
  mov    -0x1c(%rbp),%edx
  mov    -0x18(%rbp),%eax
  add    %edx,%eax
  movslq %eax,%rdx
  mov    -0x28(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  movsbl %al,%eax
  and    $0xff,%eax
  mov    %eax,-0x8(%rbp)
  cmpl   $0x0,-0x8(%rbp)
  jne    L118
  mov    $0xffffffff,%eax
  jmp    L213
L118:
  cmpl   $0x3d,-0x8(%rbp)
  jne    L176
  mov    -0x1c(%rbp),%eax
  jmp    L213
L176:
  cmpl   $0xa,-0x8(%rbp)
  je     L183
  cmpl   $0x20,-0x8(%rbp)
  ja     L112
  nop
  addl   $0x1,-0x18(%rbp)
  jmp    L161
L183:
  nop
  jmp    L22
L112:
  nop
L22:
  mov    -0x18(%rbp),%eax
  add    $0x1,%eax
  add    %eax,-0x1c(%rbp)
L151:
  mov    -0x1c(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x28(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  movsbl %al,%eax
  and    $0xff,%eax
  mov    %eax,-0x4(%rbp)
  cmpl   $0x0,-0x4(%rbp)
  jne    L235
  mov    $0xffffffff,%eax
  jmp    L213
L235:
  cmpl   $0xa,-0x4(%rbp)
  je     L33
  addl   $0x1,-0x1c(%rbp)
  jmp    L151
L33:
  nop
  jmp    L254
L213:
  pop    %rbp
  ret
```

assistant: ```c
int find_tag_var_start(const char *tagbuffer, const char *varname) {
  int i, j;
  if (!tagbuffer || !varname)
    return -1;
  for (i = 0;;) {
    for (;; i++) {
      unsigned u = ((unsigned)(tagbuffer[i])) & 0xFF;
      if (!u)
        return -1;
      if (u <= 0x20)
        continue;
      break;
    }
    for (j = 0;; j++) {
      unsigned ucmp = ((unsigned)(varname[j])) & 0xFF;
      unsigned u = ((unsigned)(tagbuffer[i + j])) & 0xFF;
      if (!ucmp)
        break;
      if (!u)
        return -1;
      if (ucmp >= 'A' && ucmp <= 'Z') {
        ucmp -= 'A';
        ucmp += 'a';
      }
      if (u >= 'A' && u <= 'Z') {
        u -= 'A';
        u += 'a';
      }
      if (u != ucmp)
        break;
    }
    if (!varname[j]) {
      for (;; j++) {
        unsigned u = ((unsigned)(tagbuffer[i + j])) & 0xFF;
        if (!u)
          return -1;
        if (u == '=')
          return i;
        if (u == 0x0A)
          break;
        if (u <= 0x20)
          continue;
        break;
      }
    }
    i += j + 1;
    for (;; i++) {
      unsigned u = ((unsigned)(tagbuffer[i])) & 0xFF;
      if (!u)
        return -1;
      if (u == 0x0A)
        break;
    }
  }
  return -1;
}
```