user: Converte this assembly snippet into its equivalent C code:

```asm
<rftfsub>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  mov    %edi,-0x54(%rbp)
  mov    %rsi,-0x60(%rbp)
  mov    %edx,-0x58(%rbp)
  mov    %rcx,-0x68(%rbp)
  mov    -0x54(%rbp),%eax
  sar    %eax
  mov    %eax,-0x3c(%rbp)
  mov    -0x58(%rbp),%eax
  add    %eax,%eax
  cltd
  idivl  -0x3c(%rbp)
  mov    %eax,-0x38(%rbp)
  movl   $0x0,-0x40(%rbp)
  movl   $0x2,-0x44(%rbp)
  jmp    L16
L19:
  mov    -0x54(%rbp),%eax
  sub    -0x44(%rbp),%eax
  mov    %eax,-0x34(%rbp)
  mov    -0x38(%rbp),%eax
  add    %eax,-0x40(%rbp)
  mov    -0x58(%rbp),%eax
  sub    -0x40(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x68(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm1
  movsd  D2(%rip),%xmm0
  subsd  %xmm1,%xmm0
  movsd  %xmm0,-0x30(%rbp)
  mov    -0x40(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x68(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  movsd  %xmm0,-0x28(%rbp)
  mov    -0x44(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x60(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  mov    -0x34(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x60(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm1
  subsd  %xmm1,%xmm0
  movsd  %xmm0,-0x20(%rbp)
  mov    -0x44(%rbp),%eax
  cltq
  add    $0x1,%rax
  lea    0x0(,%rax,8),%rdx
  mov    -0x60(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm1
  mov    -0x34(%rbp),%eax
  cltq
  add    $0x1,%rax
  lea    0x0(,%rax,8),%rdx
  mov    -0x60(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  addsd  %xmm1,%xmm0
  movsd  %xmm0,-0x18(%rbp)
  movsd  -0x30(%rbp),%xmm0
  mulsd  -0x20(%rbp),%xmm0
  movsd  -0x28(%rbp),%xmm1
  mulsd  -0x18(%rbp),%xmm1
  subsd  %xmm1,%xmm0
  movsd  %xmm0,-0x10(%rbp)
  movsd  -0x30(%rbp),%xmm0
  movapd %xmm0,%xmm1
  mulsd  -0x18(%rbp),%xmm1
  movsd  -0x28(%rbp),%xmm0
  mulsd  -0x20(%rbp),%xmm0
  addsd  %xmm1,%xmm0
  movsd  %xmm0,-0x8(%rbp)
  mov    -0x44(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x60(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  mov    -0x44(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x60(%rbp),%rax
  add    %rdx,%rax
  subsd  -0x10(%rbp),%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x44(%rbp),%eax
  cltq
  add    $0x1,%rax
  lea    0x0(,%rax,8),%rdx
  mov    -0x60(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  mov    -0x44(%rbp),%eax
  cltq
  add    $0x1,%rax
  lea    0x0(,%rax,8),%rdx
  mov    -0x60(%rbp),%rax
  add    %rdx,%rax
  subsd  -0x8(%rbp),%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x34(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x60(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  mov    -0x34(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x60(%rbp),%rax
  add    %rdx,%rax
  addsd  -0x10(%rbp),%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x34(%rbp),%eax
  cltq
  add    $0x1,%rax
  lea    0x0(,%rax,8),%rdx
  mov    -0x60(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  mov    -0x34(%rbp),%eax
  cltq
  add    $0x1,%rax
  lea    0x0(,%rax,8),%rdx
  mov    -0x60(%rbp),%rax
  add    %rdx,%rax
  subsd  -0x8(%rbp),%xmm0
  movsd  %xmm0,(%rax)
  addl   $0x2,-0x44(%rbp)
L16:
  mov    -0x44(%rbp),%eax
  cmp    -0x3c(%rbp),%eax
  jl     L19
  nop
  nop
  pop    %rbp
  ret
```

tool_calls: name: retrieve_data
arguments: data_tag: D2
type_guessed: f64

tool: D2: 0.5

assistant: ```c
void rftfsub(int n, double *a, int nc, double *c) {
  int j, k, kk, ks, m;
  double wkr, wki, xr, xi, yr, yi;
  m = n >> 1;
  ks = 2 * nc / m;
  kk = 0;
  for (j = 2; j < m; j += 2) {
    k = n - j;
    kk += ks;
    wkr = 0.5 - c[nc - kk];
    wki = c[kk];
    xr = a[j] - a[k];
    xi = a[j + 1] + a[k + 1];
    yr = wkr * xr - wki * xi;
    yi = wkr * xi + wki * xr;
    a[j] -= yr;
    a[j + 1] -= yi;
    a[k] += yr;
    a[k + 1] -= yi;
  }
}
```