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

```asm
<cftmd21>:
  endbr64
  push   %r15
  lea    0x0(,%rsi,8),%eax
  push   %r14
  push   %r13
  push   %r12
  push   %rbp
  movslq %esi,%rbp
  push   %rbx
  shl    $0x3,%rbp
  mov    %rdx,%rbx
  lea    0x0(,%rsi,4),%edx
  lea    (%rbx,%rbp,1),%r12
  lea    (%r12,%rbp,1),%r13
  sub    $0x68,%rsp
  add    %r13,%rbp
  mov    %edi,0x5c(%rsp)
  mov    %edx,0x54(%rsp)
  mov    %eax,0x58(%rsp)
  cmp    %edi,%eax
  jge    L22
  add    %eax,%edx
  lea    0x10(%rcx),%rdi
  lea    (%rsi,%rax,1),%r15d
  add    $0x20,%rcx
  add    %edx,%esi
  mov    %rdi,0x48(%rsp)
  mov    %rcx,0x38(%rsp)
  mov    %esi,0x44(%rsp)
  mov    %eax,0x40(%rsp)
  nopl   0x0(%rax,%rax,1)
L6:
  mov    0x48(%rsp),%rax
  movsd  0x8(%rax),%xmm6
  movsd  (%rax),%xmm5
  mov    0x38(%rsp),%rax
  movapd %xmm6,%xmm0
  movsd  %xmm6,0x10(%rsp)
  movsd  0x8(%rax),%xmm2
  addsd  %xmm6,%xmm0
  movsd  (%rax),%xmm7
  movsd  %xmm5,0x8(%rsp)
  mov    0x40(%rsp),%eax
  movapd %xmm2,%xmm1
  movapd %xmm7,%xmm6
  movsd  %xmm7,0x18(%rsp)
  mulsd  %xmm0,%xmm1
  movsd  %xmm2,0x20(%rsp)
  mov    %eax,%r14d
  mulsd  %xmm7,%xmm0
  subsd  %xmm1,%xmm6
  subsd  %xmm2,%xmm0
  movsd  %xmm6,0x28(%rsp)
  movsd  %xmm0,0x30(%rsp)
  cmp    %r15d,%eax
  jge    L13
  nopl   0x0(%rax)
L14:
  mov    %rbx,%rdi
  call   <resetA@plt>
  movsd  0x30(%rsp),%xmm5
  mov    %r14d,%edi
  movsd  0x28(%rsp),%xmm4
  movsd  0x10(%rsp),%xmm3
  mov    %rbp,%r8
  mov    %r13,%rcx
  mov    %r12,%rdx
  movsd  0x8(%rsp),%xmm2
  movsd  0x20(%rsp),%xmm1
  mov    %rbx,%rsi
  add    $0x2,%r14d
  movsd  0x18(%rsp),%xmm0
  call   <btrfly@plt>
  cmp    %r15d,%r14d
  jl     L14
L13:
  movsd  0x8(%rsp),%xmm6
  mov    0x38(%rsp),%rax
  movsd  0x10(%rsp),%xmm4
  xorpd  D1(%rip),%xmm4
  movapd %xmm6,%xmm0
  movsd  0x18(%rax),%xmm3
  movsd  0x10(%rax),%xmm7
  addsd  %xmm6,%xmm0
  mov    0x40(%rsp),%r14d
  movsd  %xmm4,0x10(%rsp)
  add    0x54(%rsp),%r14d
  movapd %xmm3,%xmm1
  movapd %xmm7,%xmm6
  movsd  %xmm7,0x18(%rsp)
  movsd  %xmm3,0x20(%rsp)
  mulsd  %xmm0,%xmm1
  mulsd  %xmm7,%xmm0
  subsd  %xmm1,%xmm6
  subsd  %xmm3,%xmm0
  movsd  %xmm6,0x28(%rsp)
  movsd  %xmm0,0x30(%rsp)
  cmp    %r14d,0x44(%rsp)
  jle    L0
  mov    %r15d,0x50(%rsp)
  mov    %r14d,%r15d
  mov    0x44(%rsp),%r14d
  nopl   0x0(%rax,%rax,1)
L18:
  mov    %rbx,%rdi
  call   <resetA@plt>
  movsd  0x30(%rsp),%xmm5
  mov    %r15d,%edi
  movsd  0x28(%rsp),%xmm4
  movsd  0x8(%rsp),%xmm3
  mov    %rbp,%r8
  mov    %r13,%rcx
  mov    %r12,%rdx
  movsd  0x10(%rsp),%xmm2
  movsd  0x20(%rsp),%xmm1
  mov    %rbx,%rsi
  add    $0x2,%r15d
  movsd  0x18(%rsp),%xmm0
  call   <btrfly@plt>
  cmp    %r14d,%r15d
  jl     L18
  mov    0x50(%rsp),%r15d
L0:
  mov    0x58(%rsp),%edx
  addq   $0x10,0x48(%rsp)
  add    %edx,0x40(%rsp)
  mov    0x40(%rsp),%eax
  addq   $0x20,0x38(%rsp)
  add    %edx,%r15d
  add    %edx,0x44(%rsp)
  cmp    %eax,0x5c(%rsp)
  jg     L6
L22:
  add    $0x68,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
```

tool_calls: name: retrieve_data
arguments: data_tag: D1
datatype: byte[16]

tool: {"D1": [0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x80,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00]}

assistant: ```c
void cftmd21(int n, int l, double *a, double *w) {
  int j, k, k1;
  int m = l << 2;
  int m2 = 2 * m;
  int m3 = 3 * m;
  double *v = w + 1;
  double *b = a + l;
  double *c = a + l + l;
  double *d = a + l + l + l;
  for (k = m2, k1 = 2; k < n; k += m2, k1 += 2) {
    double wk2r = w[k1];
    double wk2i = v[k1];
    double wk1r = w[k1 + k1];
    double wk1i = v[k1 + k1];
    double wk3r = wk1r - 2 * wk2i * wk1i;
    double wk3i = 2 * wk2i * wk1r - wk1i;
#pragma mta use 100 streams
#pragma mta assert no dependence
    for (j = k; j < k + l; j += 2) {
      resetA(a);
      btrfly(j, wk1r, wk1i, wk2r, wk2i, wk3r, wk3i, a, b, c, d);
    }
    wk1r = w[k1 + k1 + 2];
    wk1i = v[k1 + k1 + 2];
    wk3r = wk1r - 2 * wk2r * wk1i;
    wk3i = 2 * wk2r * wk1r - wk1i;
#pragma mta use 100 streams
#pragma mta assert no dependence
    for (j = k + m; j < k + m + l; j += 2) {
      resetA(a);
      btrfly(j, wk1r, wk1i, -wk2i, wk2r, wk3r, wk3i, a, b, c, d);
    }
  }
}
```