user: 下面的汇编指令对应的C源代码是什么:

```asm
<rotate>:
  endbr64
  push   %r15
  push   %r14
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  sub    $0x38,%rsp
  mov    %rdi,(%rsp)
  mov    %fs:0x28,%rax
  mov    %rax,0x28(%rsp)
  xor    %eax,%eax
  movl   $0xfffffffd,0x18(%rsp)
  lea    0x24(%rsp),%rax
  mov    %rax,0x8(%rsp)
L8:
  mov    0x18(%rsp),%eax
  lea    0x3(%rax),%edx
  mov    %edx,%eax
  shr    $0x1f,%eax
  add    %edx,%eax
  sar    %eax
  cltq
  shl    $0x4,%rax
  add    (%rsp),%rax
  mov    %rax,0x10(%rsp)
  mov    $0x0,%r14d
L12:
  mov    0x18(%rsp),%eax
  mov    %eax,0x20(%rsp)
  lea    -0x3(%r14),%eax
  mov    %eax,0x24(%rsp)
  mov    %r14d,%ebx
  shr    $0x1f,%ebx
  add    %r14d,%ebx
  sar    %ebx
  movslq %ebx,%rbx
  mov    0x10(%rsp),%rax
  mov    (%rax,%rbx,4),%esi
  mov    %esi,0x1c(%rsp)
  lea    0x20(%rsp),%r15
  mov    0x8(%rsp),%rsi
  mov    %r15,%rdi
  call   <R90deg@plt>
  mov    0x20(%rsp),%ecx
  lea    0x3(%rcx),%eax
  mov    %eax,%ebp
  shr    $0x1f,%ebp
  add    %eax,%ebp
  sar    %ebp
  movslq %ebp,%rbp
  shl    $0x4,%rbp
  mov    (%rsp),%r12
  add    %r12,%rbp
  mov    0x24(%rsp),%ecx
  lea    0x3(%rcx),%eax
  mov    %eax,%r13d
  shr    $0x1f,%r13d
  add    %eax,%r13d
  sar    %r13d
  movslq %r13d,%r13
  mov    0x0(%rbp,%r13,4),%eax
  mov    0x10(%rsp),%rdi
  mov    %eax,(%rdi,%rbx,4)
  mov    0x8(%rsp),%rsi
  mov    %r15,%rdi
  call   <R90deg@plt>
  mov    0x20(%rsp),%eax
  add    $0x3,%eax
  mov    %eax,%ebx
  shr    $0x1f,%ebx
  add    %eax,%ebx
  sar    %ebx
  movslq %ebx,%rbx
  shl    $0x4,%rbx
  mov    %r12,(%rsp)
  add    %r12,%rbx
  mov    0x24(%rsp),%eax
  add    $0x3,%eax
  mov    %eax,%ecx
  shr    $0x1f,%ecx
  mov    %ecx,%r12d
  add    %eax,%r12d
  sar    %r12d
  movslq %r12d,%r12
  mov    (%rbx,%r12,4),%eax
  mov    %eax,0x0(%rbp,%r13,4)
  mov    0x8(%rsp),%rsi
  mov    %r15,%rdi
  call   <R90deg@plt>
  mov    0x20(%rsp),%eax
  lea    0x3(%rax),%edx
  mov    %edx,%eax
  shr    $0x1f,%eax
  add    %edx,%eax
  sar    %eax
  cltq
  shl    $0x4,%rax
  add    (%rsp),%rax
  mov    0x24(%rsp),%edi
  lea    0x3(%rdi),%ecx
  mov    %ecx,%edx
  shr    $0x1f,%edx
  add    %ecx,%edx
  sar    %edx
  movslq %edx,%rdx
  mov    (%rax,%rdx,4),%ecx
  mov    %ecx,(%rbx,%r12,4)
  mov    0x1c(%rsp),%esi
  mov    %esi,(%rax,%rdx,4)
  add    $0x2,%r14d
  cmp    $0x4,%r14d
  jne    L12
  addl   $0x2,0x18(%rsp)
  mov    0x18(%rsp),%eax
  cmp    $0x1,%eax
  jne    L8
  mov    0x28(%rsp),%rax
  sub    %fs:0x28,%rax
  jne    L13
  mov    $0x0,%eax
  add    $0x38,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
L13:
  call   <__stack_chk_fail@plt>
```

assistant: ```c
int rotate(int field[][4]) {
  int tmp = 0, offset = (4 * 2 - 1) / 2, step = 2;
  for (int i = 0, x = 0, ox = 0; i < step * 4 / 2; i += step) {
    for (int j = 0, y = 0, oy = 0; j < step * 4 / 2; j += step) {
      x = i - offset, y = j - offset;
      tmp = field[(x + offset) / step][(y + offset) / step];
      ox = x, oy = y;
      R90deg(&x, &y);
      field[(ox + offset) / step][(oy + offset) / step] = field[(x + offset) / step][(y + offset) / step];
      ox = x, oy = y;
      R90deg(&x, &y);
      field[(ox + offset) / step][(oy + offset) / step] = field[(x + offset) / step][(y + offset) / step];
      ox = x, oy = y;
      R90deg(&x, &y);
      field[(ox + offset) / step][(oy + offset) / step] = field[(x + offset) / step][(y + offset) / step];
      field[(x + offset) / step][(y + offset) / step] = tmp;
    }
  }
  return 0;
}
```