user: 请从给定的汇编指令推导出C源代码:

```asm
<fib>:
  endbr64
  mov    %edi,%r11d
  test   %edi,%edi
  je     L42
  lea    -0x1(%rdi),%r9d
  cmp    $0x1,%r9d
  jbe    L302
  push   %r15
  xor    %r11d,%r11d
  mov    %r9d,%r10d
  push   %r14
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  sub    $0x48,%rsp
  mov    %r11d,(%rsp)
L59:
  test   %r10d,%r10d
  je     L260
  lea    -0x1(%r10),%eax
  cmp    $0x1,%eax
  jbe    L139
  movl   $0x0,0x4(%rsp)
  mov    %r10d,%r15d
  mov    %r10d,0xc(%rsp)
L34:
  mov    %r15d,0x1c(%rsp)
  mov    %r15d,%eax
  sub    $0x2,%r15d
  mov    %r15d,%r11d
  cmp    $0x1,%eax
  je     L86
  cmp    $0x1,%r15d
  jbe    L163
  mov    %r15d,0x10(%rsp)
  xor    %r10d,%r10d
  mov    %r10d,%r14d
L230:
  test   %r11d,%r11d
  je     L427
  lea    -0x1(%r11),%eax
  cmp    $0x1,%eax
  jbe    L404
  mov    %r11d,0x14(%rsp)
  xor    %r15d,%r15d
  mov    %r14d,0x18(%rsp)
  mov    %r15d,0x8(%rsp)
  mov    %r11d,%r15d
L210:
  mov    %r15d,0x20(%rsp)
  mov    %r15d,%eax
  sub    $0x2,%r15d
  mov    %r15d,%ecx
  cmp    $0x1,%eax
  je     L412
  cmp    $0x1,%r15d
  jbe    L20
  xor    %edx,%edx
  mov    %r15d,%r10d
L159:
  mov    %ecx,%r12d
  test   %ecx,%ecx
  je     L293
  lea    -0x1(%rcx),%eax
  cmp    $0x1,%eax
  jbe    L283
  xor    %r9d,%r9d
L384:
  mov    %r12d,%r8d
  sub    $0x2,%r12d
  mov    %r12d,%ebx
  cmp    $0x1,%r8d
  je     L365
  cmp    $0x1,%r12d
  jbe    L212
  xor    %ebp,%ebp
  mov    %r12d,%esi
  mov    %ebp,%r12d
L501:
  mov    %ebx,%r15d
  test   %ebx,%ebx
  je     L486
  lea    -0x1(%rbx),%eax
  cmp    $0x1,%eax
  jbe    L440
  mov    %r12d,%eax
  xor    %r14d,%r14d
  mov    %edx,%r12d
  mov    %ebx,%edx
  mov    %ecx,%ebx
  mov    %eax,%ecx
L468:
  mov    %r15d,%eax
  mov    %r15d,0x24(%rsp)
  sub    $0x2,%r15d
  cmp    $0x1,%eax
  je     L57
  cmp    $0x1,%r15d
  jbe    L55
  mov    %edx,0x2c(%rsp)
  xor    %ebp,%ebp
  mov    %r8d,%r13d
  mov    %r10d,0x30(%rsp)
  mov    %esi,0x34(%rsp)
  mov    %r9d,0x38(%rsp)
  mov    %ecx,0x3c(%rsp)
  mov    %ebx,0x28(%rsp)
  mov    %r15d,%ebx
  nopl   0x0(%rax)
L263:
  mov    %ebx,%edi
  sub    $0x2,%ebx
  call   <fib>
  add    %eax,%ebp
  cmp    $0x1,%ebx
  ja     L263
  mov    0x28(%rsp),%ebx
  mov    0x2c(%rsp),%edx
  mov    %r13d,%r8d
  add    $0x1,%ebp
  mov    0x30(%rsp),%r10d
  mov    0x34(%rsp),%esi
  mov    0x38(%rsp),%r9d
  mov    0x3c(%rsp),%ecx
L277:
  add    %ebp,%r14d
  test   %r15d,%r15d
  jne    L57
  mov    %ecx,%eax
  mov    %ebx,%ecx
  mov    %edx,%ebx
  mov    %r12d,%edx
  mov    %eax,%r12d
L394:
  add    %r14d,%r12d
L182:
  sub    $0x2,%ebx
  cmp    $0x1,%ebx
  ja     L501
  mov    %r12d,%ebp
  mov    %esi,%r12d
  add    $0x1,%ebp
  nopl   0x0(%rax)
L372:
  add    %ebp,%r9d
  test   %r12d,%r12d
  jne    L365
L443:
  add    %r9d,%edx
L12:
  sub    $0x2,%ecx
  cmp    $0x1,%ecx
  ja     L159
  mov    %r10d,%r15d
  add    $0x1,%edx
L247:
  add    %edx,0x8(%rsp)
  test   %r15d,%r15d
  je     L489
L412:
  mov    0x20(%rsp),%eax
  sub    $0x3,%eax
  cmp    $0x1,%eax
  ja     L210
  mov    0x8(%rsp),%r15d
  mov    0x14(%rsp),%r11d
  mov    0x18(%rsp),%r14d
  add    $0x1,%r15d
L224:
  add    %r15d,%r14d
L314:
  sub    $0x2,%r11d
  cmp    $0x1,%r11d
  ja     L230
  mov    %r14d,%r10d
  mov    0x10(%rsp),%r15d
  add    $0x1,%r10d
L208:
  add    %r10d,0x4(%rsp)
  test   %r15d,%r15d
  je     L101
L86:
  mov    0x1c(%rsp),%eax
  sub    $0x3,%eax
  cmp    $0x1,%eax
  ja     L34
  addl   $0x1,0x4(%rsp)
  mov    0xc(%rsp),%r10d
L97:
  mov    0x4(%rsp),%edi
  add    %edi,(%rsp)
L353:
  sub    $0x2,%r10d
  cmp    $0x1,%r10d
  ja     L59
  mov    (%rsp),%r11d
  add    $0x1,%r11d
L429:
  add    $0x48,%rsp
  mov    %r11d,%eax
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
L212:
  mov    $0x1,%ebp
  add    %ebp,%r9d
  test   %r12d,%r12d
  je     L443
L365:
  sub    $0x3,%r8d
  cmp    $0x1,%r8d
  ja     L384
  add    $0x1,%r9d
  jmp    L443
  nopl   (%rax)
L57:
  mov    0x24(%rsp),%r13d
  sub    $0x3,%r13d
  cmp    $0x1,%r13d
  ja     L468
  mov    %ecx,%eax
  add    $0x1,%r14d
  mov    %ebx,%ecx
  mov    %edx,%ebx
  mov    %r12d,%edx
  mov    %eax,%r12d
  jmp    L394
L283:
  add    $0x1,%edx
  test   %eax,%eax
  jne    L12
  mov    %r10d,%r15d
  add    %edx,0x8(%rsp)
  test   %r15d,%r15d
  jne    L412
L489:
  mov    0x14(%rsp),%r11d
  mov    0x8(%rsp),%r15d
  mov    0x18(%rsp),%r14d
  jmp    L224
L293:
  mov    $0xfffffffe,%ecx
  jmp    L159
  nopl   0x0(%rax)
L55:
  mov    $0x1,%ebp
  jmp    L277
L440:
  add    $0x1,%r12d
  test   %eax,%eax
  jne    L182
  mov    %r12d,%ebp
  mov    %esi,%r12d
  jmp    L372
L486:
  mov    $0xfffffffe,%ebx
  jmp    L501
L20:
  mov    $0x1,%edx
  jmp    L247
L404:
  add    $0x1,%r14d
  test   %eax,%eax
  jne    L314
  mov    0x10(%rsp),%r15d
  mov    %r14d,%r10d
  add    %r10d,0x4(%rsp)
  test   %r15d,%r15d
  jne    L86
L101:
  mov    0xc(%rsp),%r10d
  jmp    L97
L163:
  mov    $0x1,%r10d
  jmp    L208
L427:
  mov    $0xfffffffe,%r11d
  jmp    L230
L139:
  addl   $0x1,(%rsp)
  test   %eax,%eax
  jne    L353
  mov    (%rsp),%r11d
  jmp    L429
L260:
  mov    $0xfffffffe,%r10d
  jmp    L59
L302:
  mov    $0x1,%r11d
L42:
  mov    %r11d,%eax
  ret
```

assistant: ```c
int fib(int n) {
  if (n == 0)
    return 0;
  else if (n == 1 || n == 2)
    return 1;
  else
    return (fib(n - 1) + fib(n - 2));
}
```