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

```asm
<cftbsub>:
  endbr64
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  sub    $0x8,%rsp
  mov    %rsi,%rbx
  cmp    $0x8,%edi
  jg     L37
  mov    $0x2,%ebp
  je     L75
L131:
  movslq %ebp,%rax
  lea    (%rbx,%rax,8),%rax
  lea    0x8(%rbx),%rdx
  mov    $0x0,%ecx
  movq   D11(%rip),%xmm5
L141:
  movsd  -0x8(%rdx),%xmm1
  movsd  (%rax),%xmm3
  movsd  (%rdx),%xmm0
  movsd  0x8(%rax),%xmm2
  subsd  %xmm0,%xmm2
  movapd %xmm1,%xmm4
  addsd  %xmm3,%xmm4
  movsd  %xmm4,-0x8(%rdx)
  xorpd  %xmm5,%xmm0
  subsd  0x8(%rax),%xmm0
  movsd  %xmm0,(%rdx)
  subsd  %xmm3,%xmm1
  movsd  %xmm1,(%rax)
  movsd  %xmm2,0x8(%rax)
  add    $0x2,%ecx
  add    $0x10,%rax
  add    $0x10,%rdx
  cmp    %ebp,%ecx
  jl     L141
L21:
  add    $0x8,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  ret
L37:
  mov    %edi,%r12d
  mov    %rdx,%r13
  call   <cft1st@plt>
  cmp    $0x20,%r12d
  jle    L119
  mov    $0x8,%esi
  mov    $0x20,%ebp
  jmp    L12
L83:
  mov    %eax,%ebp
L12:
  mov    %r13,%rcx
  mov    %rbx,%rdx
  mov    %r12d,%edi
  call   <cftmdl@plt>
  lea    0x0(,%rbp,4),%eax
  mov    %ebp,%esi
  cmp    %r12d,%eax
  jl     L83
  je     L145
  test   %ebp,%ebp
  jg     L131
  jmp    L21
L145:
  test   %ebp,%ebp
  jg     L55
  jmp    L21
L75:
  mov    $0x2,%ebp
L55:
  movslq %ebp,%rax
  shl    $0x3,%rax
  lea    (%rbx,%rax,1),%rdx
  mov    %rdx,%rsi
  add    %rax,%rdx
  mov    %rdx,%rcx
  add    %rax,%rdx
  mov    $0x0,%eax
  movq   D11(%rip),%xmm10
L78:
  movsd  (%rbx,%rax,8),%xmm1
  movsd  (%rsi),%xmm4
  movapd %xmm1,%xmm5
  addsd  %xmm4,%xmm5
  movsd  0x8(%rbx,%rax,8),%xmm3
  movsd  0x8(%rsi),%xmm0
  movapd %xmm3,%xmm2
  xorpd  %xmm10,%xmm2
  subsd  %xmm0,%xmm2
  subsd  %xmm4,%xmm1
  subsd  %xmm3,%xmm0
  movsd  (%rcx),%xmm3
  movsd  (%rdx),%xmm9
  movapd %xmm3,%xmm7
  addsd  %xmm9,%xmm7
  movsd  0x8(%rcx),%xmm4
  movsd  0x8(%rdx),%xmm8
  movapd %xmm4,%xmm6
  addsd  %xmm8,%xmm6
  subsd  %xmm9,%xmm3
  subsd  %xmm8,%xmm4
  movapd %xmm5,%xmm8
  addsd  %xmm7,%xmm8
  movsd  %xmm8,(%rbx,%rax,8)
  movapd %xmm2,%xmm8
  subsd  %xmm6,%xmm8
  movsd  %xmm8,0x8(%rbx,%rax,8)
  subsd  %xmm7,%xmm5
  movsd  %xmm5,(%rcx)
  addsd  %xmm6,%xmm2
  movsd  %xmm2,0x8(%rcx)
  movapd %xmm1,%xmm2
  subsd  %xmm4,%xmm2
  movsd  %xmm2,(%rsi)
  movapd %xmm0,%xmm2
  subsd  %xmm3,%xmm2
  movsd  %xmm2,0x8(%rsi)
  addsd  %xmm4,%xmm1
  movsd  %xmm1,(%rdx)
  addsd  %xmm3,%xmm0
  movsd  %xmm0,0x8(%rdx)
  add    $0x2,%rax
  add    $0x10,%rsi
  add    $0x10,%rcx
  add    $0x10,%rdx
  cmp    %eax,%ebp
  jg     L78
  jmp    L21
L119:
  mov    $0x8,%ebp
  jne    L131
  mov    $0x8,%ebp
  jmp    L55
```

tool_calls: name: retrieve_data
arguments: label: D11
type_guessed: byte[8]

tool: {"D11": [0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x80]}

assistant: ```c
void cftbsub(int n, double *a, double const *w) {
  int j, j1, j2, j3, l;
  double x0r, x0i, x1r, x1i, x2r, x2i, x3r, x3i;
  l = 2;
  if (n > 8) {
    cft1st(n, a, w);
    l = 8;
    while ((l << 2) < n) {
      cftmdl(n, l, a, w);
      l <<= 2;
    }
  }
  if ((l << 2) == n) {
    for (j = 0; j < l; j += 2) {
      j1 = j + l;
      j2 = j1 + l;
      j3 = j2 + l;
      x0r = a[j] + a[j1];
      x0i = -a[j + 1] - a[j1 + 1];
      x1r = a[j] - a[j1];
      x1i = -a[j + 1] + a[j1 + 1];
      x2r = a[j2] + a[j3];
      x2i = a[j2 + 1] + a[j3 + 1];
      x3r = a[j2] - a[j3];
      x3i = a[j2 + 1] - a[j3 + 1];
      a[j] = x0r + x2r;
      a[j + 1] = x0i - x2i;
      a[j2] = x0r - x2r;
      a[j2 + 1] = x0i + x2i;
      a[j1] = x1r - x3i;
      a[j1 + 1] = x1i - x3r;
      a[j3] = x1r + x3i;
      a[j3 + 1] = x1i + x3r;
    }
  } else {
    for (j = 0; j < l; j += 2) {
      j1 = j + l;
      x0r = a[j] - a[j1];
      x0i = -a[j + 1] + a[j1 + 1];
      a[j] += a[j1];
      a[j + 1] = -a[j + 1] - a[j1 + 1];
      a[j1] = x0r;
      a[j1 + 1] = x0i;
    }
  }
}
```