user: Please show me the C implementation that matches the assembly code listed below:

```asm
<fft_real_mon>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  sub    $0x30,%rsp
  mov    %rdi,-0x18(%rbp)
  mov    %esi,-0x1c(%rbp)
  mov    %edx,-0x20(%rbp)
  mov    %rcx,-0x28(%rbp)
  mov    %r8,-0x30(%rbp)
  cmpl   $0x8,-0x1c(%rbp)
  jne    L21
  lea    D2(%rip),%rax
  mov    %rax,%rdi
  mov    $0x0,%eax
  call   <SCIprintf@plt>
  mov    -0x20(%rbp),%edx
  mov    -0x1c(%rbp),%eax
  mov    %eax,%esi
  lea    D33(%rip),%rax
  mov    %rax,%rdi
  mov    $0x0,%eax
  call   <SCIprintf@plt>
  lea    D26(%rip),%rax
  mov    %rax,%rdi
  mov    $0x0,%eax
  call   <SCIprintf@plt>
  movl   $0x0,-0xc(%rbp)
  jmp    L7
L31:
  mov    -0xc(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x18(%rbp),%rax
  add    %rdx,%rax
  mov    (%rax),%rdx
  mov    -0xc(%rbp),%eax
  movq   %rdx,%xmm0
  mov    %eax,%esi
  lea    D23(%rip),%rax
  mov    %rax,%rdi
  mov    $0x1,%eax
  call   <SCIprintf@plt>
  addl   $0x1,-0xc(%rbp)
L7:
  mov    -0xc(%rbp),%eax
  cmp    -0x1c(%rbp),%eax
  jl     L31
  lea    D49(%rip),%rax
  mov    %rax,%rdi
  mov    $0x0,%eax
  call   <SCIprintf@plt>
  mov    -0x1c(%rbp),%eax
  mov    %eax,%edx
  shr    $0x1f,%edx
  add    %edx,%eax
  sar    %eax
  mov    %eax,-0x4(%rbp)
  movl   $0x0,-0x8(%rbp)
  jmp    L38
L46:
  mov    -0x8(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x30(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  mov    -0x8(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x28(%rbp),%rax
  add    %rdx,%rax
  mov    (%rax),%rdx
  mov    -0x8(%rbp),%eax
  movapd %xmm0,%xmm1
  movq   %rdx,%xmm0
  mov    %eax,%esi
  lea    D60(%rip),%rax
  mov    %rax,%rdi
  mov    $0x2,%eax
  call   <SCIprintf@plt>
  addl   $0x1,-0x8(%rbp)
L38:
  mov    -0x8(%rbp),%eax
  cmp    -0x4(%rbp),%eax
  jle    L46
  lea    D2(%rip),%rax
  mov    %rax,%rdi
  mov    $0x0,%eax
  call   <SCIprintf@plt>
  jmp    L12
L21:
  nop
L12:
  leave
  ret
```

tool_calls: name: parse_data
arguments: data_tag: D2
datatype: string
name: parse_data
arguments: data_tag: D33
datatype: string
name: parse_data
arguments: data_tag: D26
datatype: string
name: parse_data
arguments: data_tag: D23
datatype: string
name: parse_data
arguments: data_tag: D49
datatype: string
name: parse_data
arguments: data_tag: D60
datatype: string

tool: D2: ----------------------------------------


tool: D33: DEBUG MON: fft_real_mon: npoint=%d, interval=%d


tool: D26: ---input---


tool: D23:  i=%3d: re = %12.3le


tool: D49: ---output---


tool: D60:  fi=%2d: re = %12.3le, im = %12.3le


assistant: ```c
void fft_real_mon(double din_re[], const int npoint, const int interval, double out_re[], double out_im[]) {
  int i;
  int fi, fi_max;
  if (npoint != 8)
    return;
  SCIprintf("----------------------------------------\n");
  SCIprintf("DEBUG MON: fft_real_mon: npoint=%d, interval=%d\n", npoint, interval);
  SCIprintf("---input---\n");
  for (i = 0; i < npoint; i++) {
    SCIprintf(" i=%3d: re = %12.3le\n", i, din_re[i]);
  }
  SCIprintf("---output---\n");
  fi_max = npoint / 2;
  for (fi = 0; fi <= fi_max; fi++) {
    SCIprintf(" fi=%2d: re = %12.3le, im = %12.3le\n", fi, out_re[fi], out_im[fi]);
  }
  SCIprintf("----------------------------------------\n");
}
```