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

```asm
<cftbsub>:
  endbr64
  push   %r12
  push   %rbp
  push   %rbx
  mov    %rsi,%rbx
  cmp    $0x8,%edi
  jg     L123
  mov    $0x2,%ebp
  je     L72
L69:
  movslq %ebp,%rax
  lea    (%rbx,%rax,8),%rax
  lea    0x8(%rbx),%rdx
  mov    $0x0,%ecx
  movq   D7(%rip),%xmm5
L126:
  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     L126
L65:
  pop    %rbx
  pop    %rbp
  pop    %r12
  ret
L123:
  mov    %edi,%r12d
  call   <cft1st@plt>
  cmp    $0x20,%r12d
  jle    L149
  mov    $0x8,%esi
  mov    $0x20,%ebp
  jmp    L103
L68:
  mov    %eax,%ebp
L103:
  mov    %rbx,%rdx
  mov    %r12d,%edi
  call   <cftmdl@plt>
  lea    0x0(,%rbp,4),%eax
  mov    %ebp,%esi
  cmp    %r12d,%eax
  jl     L68
  je     L136
  test   %ebp,%ebp
  jg     L69
  jmp    L65
L136:
  test   %ebp,%ebp
  jg     L139
  jmp    L65
L72:
  mov    $0x2,%ebp
L139:
  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   D7(%rip),%xmm10
L10:
  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     L10
  jmp    L65
L149:
  mov    $0x8,%ebp
  jne    L69
  mov    $0x8,%ebp
  jmp    L139
```

tool_calls: name: disassemble_data
arguments: data_label: D7
data_type: byte[8]

tool: {"D7": [0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x80]}

assistant: ```c
void cftbsub(int n, double *a) {
  void cft1st(int n, double *a);
  void cftmdl(int n, int l, double *a);
  int j, j1, j2, j3, l;
  double x0r, x0i, x1r, x1i, x2r, x2i, x3r, x3i;
  l = 2;
  if (n > 8) {
    cft1st(n, a);
    l = 8;
    while ((l << 2) < n) {
      cftmdl(n, l, a);
      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;
    }
  }
}
```