user: Demonstrate the C code that generates the assembly output below:

```asm
<dfft>:
  endbr64
  push   %r15
  push   %r14
  mov    %rcx,%r14
  push   %r13
  push   %r12
  mov    %edi,%r12d
  push   %rbp
  mov    %rdx,%rbp
  mov    %rcx,%rdx
  push   %rbx
  mov    %esi,%ebx
  mov    %ebx,%r15d
  shr    $0x1f,%r15d
  sub    $0x18,%rsp
  add    %ebx,%r15d
  mov    %esi,0xc(%rsp)
  mov    %rbp,%rsi
  sar    %r15d
  call   <cft1st@plt>
  cmp    $0x7,%ebx
  jle    L57
  mov    %r15d,%r13d
  mov    $0x8,%ebx
  mov    $0x4,%r15d
L62:
  mov    %ebx,%esi
  mov    %r14,%rcx
  mov    %rbp,%rdx
  mov    %r12d,%edi
  call   <cftmd1@plt>
  add    $0x2,%r15d
  shl    $0x2,%ebx
  cmp    %r13d,%r15d
  jle    L62
L9:
  mov    0xc(%rsp),%eax
  cmp    %eax,%r15d
  jge    L7
  mov    %eax,%r13d
  sub    $0x1,%r13d
  sub    %r15d,%r13d
  xor    %r15d,%r15d
  shr    %r13d
  nopl   (%rax)
L11:
  mov    %ebx,%esi
  mov    %r14,%rcx
  mov    %rbp,%rdx
  mov    %r12d,%edi
  call   <cftmd2@plt>
  mov    %r15d,%eax
  shl    $0x2,%ebx
  add    $0x1,%r15d
  cmp    %eax,%r13d
  jne    L11
L7:
  movslq %ebx,%r14
  lea    0x0(,%rbx,4),%eax
  shl    $0x3,%r14
  lea    0x0(%rbp,%r14,1),%r13
  cmp    %r12d,%eax
  je     L30
  sub    $0x1,%ebx
  xor    %eax,%eax
  xor    %edx,%edx
  shr    %ebx
  add    $0x1,%ebx
  nopl   0x0(%rax,%rax,1)
L33:
  movupd 0x0(%r13,%rax,1),%xmm1
  movupd 0x0(%rbp,%rax,1),%xmm0
  add    $0x1,%edx
  movapd %xmm1,%xmm2
  addpd  %xmm0,%xmm2
  subpd  %xmm1,%xmm0
  movups %xmm2,0x0(%rbp,%rax,1)
  movups %xmm0,0x0(%r13,%rax,1)
  add    $0x10,%rax
  cmp    %edx,%ebx
  ja     L33
  add    $0x18,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
  xchg   %ax,%ax
L30:
  lea    0x0(%r13,%r14,1),%r15
  movsd  D8(%rip),%xmm2
  xor    %r12d,%r12d
  pxor   %xmm1,%xmm1
  add    %r15,%r14
  nopw   0x0(%rax,%rax,1)
L58:
  movapd %xmm1,%xmm5
  movapd %xmm2,%xmm4
  movapd %xmm1,%xmm3
  mov    %r12d,%edi
  movapd %xmm2,%xmm0
  mov    %r14,%r8
  mov    %r15,%rcx
  mov    %r13,%rdx
  mov    %rbp,%rsi
  add    $0x2,%r12d
  call   <btrfly@plt>
  mov    D8(%rip),%rax
  cmp    %ebx,%r12d
  pxor   %xmm1,%xmm1
  movq   %rax,%xmm2
  jl     L58
  add    $0x18,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
  nopl   0x0(%rax)
L57:
  mov    $0x8,%ebx
  mov    $0x4,%r15d
  jmp    L9
```

tool_calls: name: retrieve_data
arguments: data_label: D8
datatype: f64

tool: D8: 1

assistant: ```c
void dfft(int n, int logn, double *a, double *w) {
  int i, l, j;
  double *v, *b, *c, *d;
  cft1st(n, a, w);
  i = 4;
  l = 8;
  for (; i <= logn / 2; i += 2, l *= 4)
    cftmd1(n, l, a, w);
  for (; i <= logn - 1; i += 2, l *= 4)
    cftmd2(n, l, a, w);
  v = w + 1;
  b = a + l;
  c = a + l + l;
  d = a + l + l + l;
  if ((l << 2) == n) {
#pragma mta use 100 streams
#pragma mta assert no dependence
    for (j = 0; j < l; j += 2)
      btrfly(j, 1.0, 0.0, 1.0, 0.0, 1.0, 0.0, a, b, c, d);
  } else {
#pragma mta use 100 streams
#pragma mta assert no dependence
    for (j = 0; j < l; j += 2) {
      double x0r = a[j];
      double x0i = a[j + 1];
      double x1r = b[j];
      double x1i = b[j + 1];
      a[j] = x0r + x1r;
      a[j + 1] = x0i + x1i;
      b[j] = x0r - x1r;
      b[j + 1] = x0i - x1i;
    }
  }
}
```