user: 请从给定的汇编指令推导出C源代码：

```asm
<fib>:
  endbr64
  push   %r15
  push   %r14
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  sub    $0x48,%rsp
  mov    %edi,0x4(%rsp)
  mov    %edi,(%rsp)
  movl   $0x0,0x8(%rsp)
  cmp    $0x2,%edi
  jle    L123
L164:
  mov    (%rsp),%eax
  movl   $0x0,0xc(%rsp)
  sub    $0x1,%eax
  mov    %eax,%r11d
  cmp    $0x2,%eax
  je     L237
L127:
  lea    -0x1(%r11),%eax
  movl   $0x0,0x10(%rsp)
  cmp    $0x2,%eax
  je     L229
  mov    %r11d,0x18(%rsp)
  mov    %eax,%r11d
L6:
  lea    -0x1(%r11),%eax
  movl   $0x0,0x14(%rsp)
  mov    %eax,%r9d
  cmp    $0x2,%eax
  je     L122
  mov    %r11d,0x1c(%rsp)
L170:
  lea    -0x1(%r9),%r12d
  xor    %r11d,%r11d
  cmp    $0x2,%r12d
  je     L51
  mov    %r9d,0x20(%rsp)
L236:
  lea    -0x1(%r12),%ebx
  xor    %r15d,%r15d
  cmp    $0x2,%ebx
  je     L30
L28:
  cmp    $0x3,%ebx
  je     L42
  lea    -0x4(%rbx),%r14d
  lea    -0x7(%rbx),%esi
  xor    %ecx,%ecx
  mov    %r14d,%eax
  lea    -0x5(%rbx),%r8d
  mov    %r14d,%r9d
  and    $0xfffffffe,%eax
  sub    %eax,%esi
L116:
  lea    0x3(%r8),%ebp
  xor    %edx,%edx
  cmp    $0xffffffff,%r8d
  je     L145
L181:
  lea    -0x1(%rbp),%r13d
  xor    %r10d,%r10d
  cmp    $0x2,%r13d
  je     L194
L21:
  lea    -0x1(%r13),%edi
  mov    %r8d,0x3c(%rsp)
  sub    $0x2,%r13d
  mov    %r9d,0x38(%rsp)
  mov    %esi,0x34(%rsp)
  mov    %r10d,0x30(%rsp)
  mov    %edx,0x2c(%rsp)
  mov    %ecx,0x28(%rsp)
  mov    %r11d,0x24(%rsp)
  call   <fib>
  mov    0x30(%rsp),%r10d
  mov    0x24(%rsp),%r11d
  mov    0x28(%rsp),%ecx
  mov    0x2c(%rsp),%edx
  add    %eax,%r10d
  cmp    $0x2,%r13d
  mov    0x34(%rsp),%esi
  mov    0x38(%rsp),%r9d
  mov    0x3c(%rsp),%r8d
  jg     L21
  lea    -0x4(%rbp),%edi
  lea    -0x3(%rbp),%eax
  and    $0xfffffffe,%edi
  sub    %edi,%eax
  add    %r10d,%eax
L191:
  sub    $0x2,%ebp
  add    %eax,%edx
  cmp    $0x2,%ebp
  jg     L181
  mov    %r8d,%eax
  mov    %r9d,%ebp
  and    $0xfffffffe,%eax
  sub    %eax,%ebp
  add    %edx,%ebp
L145:
  sub    $0x2,%r8d
  add    %ebp,%ecx
  sub    $0x2,%r9d
  cmp    %r8d,%esi
  jne    L116
  and    $0xfffffffe,%r14d
  lea    -0x3(%rbx),%eax
  sub    %r14d,%eax
  add    %ecx,%eax
L216:
  sub    $0x2,%ebx
  add    %eax,%r15d
  cmp    $0x2,%ebx
  jg     L28
  lea    -0x4(%r12),%edx
  lea    -0x3(%r12),%eax
  and    $0xfffffffe,%edx
  sub    %edx,%eax
  add    %r15d,%eax
L173:
  sub    $0x2,%r12d
  add    %eax,%r11d
  cmp    $0x2,%r12d
  jg     L236
  mov    0x20(%rsp),%r9d
  lea    -0x4(%r9),%edx
  lea    -0x3(%r9),%eax
  and    $0xfffffffe,%edx
  sub    %edx,%eax
  add    %r11d,%eax
L41:
  sub    $0x2,%r9d
  add    %eax,0x14(%rsp)
  cmp    $0x2,%r9d
  jg     L170
  mov    0x1c(%rsp),%r11d
  lea    -0x4(%r11),%edx
  lea    -0x3(%r11),%eax
  and    $0xfffffffe,%edx
  sub    %edx,%eax
  add    0x14(%rsp),%eax
L148:
  sub    $0x2,%r11d
  add    %eax,0x10(%rsp)
  cmp    $0x2,%r11d
  jg     L6
  mov    0x18(%rsp),%r11d
  lea    -0x4(%r11),%edx
  lea    -0x3(%r11),%eax
  and    $0xfffffffe,%edx
  sub    %edx,%eax
  add    0x10(%rsp),%eax
L50:
  sub    $0x2,%r11d
  add    %eax,0xc(%rsp)
  cmp    $0x2,%r11d
  jg     L127
  mov    (%rsp),%eax
  lea    -0x4(%rax),%edx
  sub    $0x3,%eax
  and    $0xfffffffe,%edx
  sub    %edx,%eax
  add    0xc(%rsp),%eax
L60:
  subl   $0x2,(%rsp)
  mov    (%rsp),%edi
  add    %eax,0x8(%rsp)
  cmp    $0x2,%edi
  jg     L164
  mov    0x4(%rsp),%eax
  lea    -0x3(%rax),%edx
  sub    $0x2,%eax
  and    $0xfffffffe,%edx
  sub    %edx,%eax
  add    0x8(%rsp),%eax
  mov    %eax,0x4(%rsp)
L123:
  mov    0x4(%rsp),%eax
  add    $0x48,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
L42:
  mov    $0x2,%eax
  jmp    L216
  nopl   0x0(%rax)
L194:
  mov    $0x2,%eax
  jmp    L191
L30:
  mov    $0x2,%eax
  jmp    L173
L51:
  mov    $0x2,%eax
  jmp    L41
L122:
  mov    $0x2,%eax
  jmp    L148
L229:
  mov    $0x2,%eax
  jmp    L50
L237:
  mov    $0x2,%eax
  jmp    L60
```

assistant: ```c
int fib(int n) {
  if (n < 3)
    return n;
  else
    return fib(n - 1) + fib(n - 2);
}
```