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

```asm
<fft>:
  endbr64
  push   %r15
  push   %r14
  mov    %rdx,%r14
  push   %r13
  mov    %ecx,%r13d
  push   %r12
  movslq %r8d,%r12
  push   %rbp
  mov    %r12,%r15
  push   %rbx
  mov    %rsi,%rbx
  sub    $0x38,%rsp
  mov    %rdi,0x8(%rsp)
  movaps %xmm0,0x10(%rsp)
  mov    %fs:0x28,%rax
  mov    %rax,0x28(%rsp)
  xor    %eax,%eax
  mov    %r12d,0x20(%rsp)
  shl    $0x3,%r12
  mov    %r12,%rdi
  call   <malloc@plt>
  mov    %r12,%rdi
  mov    %rax,%rbp
  call   <malloc@plt>
  mov    %rax,%r12
  test   %r15d,%r15d
  jle    L103
  mov    %r15d,%edx
  xor    %esi,%esi
  mov    %rax,%rdi
  shl    $0x3,%rdx
  call   <memset@plt>
  lea    -0x1(%r15),%eax
  mov    0x8(%rsp),%r9
  cmp    $0x2,%eax
  jbe    L14
  mov    %r15d,%edx
  movaps 0x10(%rsp),%xmm0
  xor    %eax,%eax
  shr    $0x2,%edx
  shl    $0x4,%rdx
  nopw   0x0(%rax,%rax,1)
L43:
  movlps 0x8(%r9,%rax,1),%xmm0
  cvtps2pd (%r9,%rax,1),%xmm1
  movups %xmm1,0x0(%rbp,%rax,2)
  cvtps2pd %xmm0,%xmm1
  movups %xmm1,0x10(%rbp,%rax,2)
  add    $0x10,%rax
  cmp    %rdx,%rax
  jne    L43
  mov    %r15d,%eax
  and    $0xfffffffc,%eax
  test   $0x3,%r15b
  je     L103
L12:
  movslq %eax,%rdx
  pxor   %xmm0,%xmm0
  cvtss2sd (%r9,%rdx,4),%xmm0
  lea    0x0(,%rdx,8),%rcx
  lea    0x0(,%rdx,4),%rsi
  movsd  %xmm0,0x0(%rbp,%rdx,8)
  lea    0x1(%rax),%edx
  cmp    %edx,%r15d
  jle    L103
  pxor   %xmm0,%xmm0
  add    $0x2,%eax
  cvtss2sd 0x4(%r9,%rsi,1),%xmm0
  movsd  %xmm0,0x8(%rbp,%rcx,1)
  cmp    %eax,%r15d
  jle    L103
  pxor   %xmm0,%xmm0
  cvtss2sd 0x8(%r9,%rsi,1),%xmm0
  movsd  %xmm0,0x10(%rbp,%rcx,1)
L103:
  lea    0x20(%rsp),%rsi
  mov    $0xffffffff,%r9d
  mov    %r12,%rcx
  xor    %eax,%eax
  mov    $0x1,%r8d
  mov    %rbp,%rdx
  mov    $0x1,%edi
  call   <fftn@plt>
  pxor   %xmm0,%xmm0
  cvtsd2ss 0x0(%rbp),%xmm0
  movss  %xmm0,(%rbx)
  movl   $0x0,(%r14)
  cmp    $0x1,%r13d
  jle    L84
  mov    %r14,%rax
  sub    %rbx,%rax
  sub    $0x4,%rax
  cmp    $0x8,%rax
  jbe    L33
  lea    -0x2(%r13),%eax
  cmp    $0x2,%eax
  jbe    L33
  lea    -0x1(%r13),%ecx
  mov    %ecx,%eax
  shr    $0x2,%eax
  lea    -0x1(%rax),%edx
  mov    $0x4,%eax
  shl    $0x4,%rdx
  add    $0x14,%rdx
  nopl   (%rax)
L55:
  movupd 0x0(%rbp,%rax,2),%xmm0
  movupd 0x10(%rbp,%rax,2),%xmm1
  addpd  %xmm0,%xmm0
  addpd  %xmm1,%xmm1
  cvtpd2ps %xmm0,%xmm0
  cvtpd2ps %xmm1,%xmm1
  movlhps %xmm1,%xmm0
  movupd 0x10(%r12,%rax,2),%xmm1
  movups %xmm0,(%rbx,%rax,1)
  movupd (%r12,%rax,2),%xmm0
  addpd  %xmm1,%xmm1
  addpd  %xmm0,%xmm0
  cvtpd2ps %xmm1,%xmm1
  cvtpd2ps %xmm0,%xmm0
  movlhps %xmm1,%xmm0
  movups %xmm0,(%r14,%rax,1)
  add    $0x10,%rax
  cmp    %rax,%rdx
  jne    L55
  mov    %ecx,%edx
  and    $0xfffffffc,%edx
  lea    0x1(%rdx),%eax
  cmp    %edx,%ecx
  je     L84
  cltq
  movsd  0x0(%rbp,%rax,8),%xmm0
  lea    0x0(,%rax,8),%rsi
  lea    0x0(,%rax,4),%rcx
  addsd  %xmm0,%xmm0
  cvtsd2ss %xmm0,%xmm0
  movss  %xmm0,(%rbx,%rax,4)
  movsd  (%r12,%rax,8),%xmm0
  addsd  %xmm0,%xmm0
  cvtsd2ss %xmm0,%xmm0
  movss  %xmm0,(%r14,%rax,4)
  lea    0x2(%rdx),%eax
  cmp    %r13d,%eax
  jge    L84
  movsd  0x8(%rbp,%rsi,1),%xmm0
  add    $0x3,%edx
  addsd  %xmm0,%xmm0
  cvtsd2ss %xmm0,%xmm0
  movss  %xmm0,0x4(%rbx,%rcx,1)
  movsd  0x8(%r12,%rsi,1),%xmm0
  addsd  %xmm0,%xmm0
  cvtsd2ss %xmm0,%xmm0
  movss  %xmm0,0x4(%r14,%rcx,1)
  cmp    %edx,%r13d
  jle    L84
  movsd  0x10(%rbp,%rsi,1),%xmm0
  addsd  %xmm0,%xmm0
  cvtsd2ss %xmm0,%xmm0
  movss  %xmm0,0x8(%rbx,%rcx,1)
  movsd  0x10(%r12,%rsi,1),%xmm0
  addsd  %xmm0,%xmm0
  cvtsd2ss %xmm0,%xmm0
  movss  %xmm0,0x8(%r14,%rcx,1)
L84:
  mov    %r12,%rdi
  call   <free@plt>
  mov    0x28(%rsp),%rax
  sub    %fs:0x28,%rax
  jne    L119
  add    $0x38,%rsp
  mov    %rbp,%rdi
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  jmp    1090 <free@plt>
  nopl   0x0(%rax)
L33:
  mov    $0x1,%eax
  nopl   (%rax)
L122:
  movsd  0x0(%rbp,%rax,8),%xmm0
  addsd  %xmm0,%xmm0
  cvtsd2ss %xmm0,%xmm0
  movss  %xmm0,(%rbx,%rax,4)
  movsd  (%r12,%rax,8),%xmm0
  addsd  %xmm0,%xmm0
  cvtsd2ss %xmm0,%xmm0
  movss  %xmm0,(%r14,%rax,4)
  add    $0x1,%rax
  cmp    %rax,%r13
  jne    L122
  jmp    L84
L14:
  xor    %eax,%eax
  jmp    L12
L119:
  call   <__stack_chk_fail@plt>
```

assistant: ```c
void fft(data, ct, st, nmodes, length) float *data, *ct, *st;
int nmodes, length;
{
  double *im, *re;
  int dim[2], i;
  dim[0] = length;
  re = (double *)malloc(length * sizeof(double));
  im = (double *)malloc(length * sizeof(double));
  for (i = 0; i < length; i++) {
    im[i] = 0.0;
    re[i] = data[i];
  }
  fftn(1, dim, re, im, 1, -1);
  ct[0] = re[0];
  st[0] = 0.0;
  for (i = 1; i < nmodes; i++) {
    ct[i] = re[i] * 2.0;
    st[i] = im[i] * 2.0;
  }
  free(im);
  free(re);
}
```