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

```asm
<sp2fctest>:
  endbr64
  push   %r15
  push   %r14
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  sub    $0x58,%rsp
  mov    %rdx,0x40(%rsp)
  mov    %ecx,%ebx
  mov    %ecx,0x4c(%rsp)
  mov    0x90(%rsp),%ecx
  lea    0x1(%rcx),%edx
  add    $0x2,%ecx
  imul   %ecx,%edx
  test   %ebx,%ebx
  jle    L50
  mov    %r8d,%r12d
  mov    %r9d,%eax
  imul   %r8d,%eax
  movslq %eax,%r8
  shl    $0x3,%eax
  mov    %eax,0x48(%rsp)
  movslq %r12d,%rcx
  lea    0x0(,%rcx,8),%r14
  mov    %r12d,%ebp
  shr    $0x1f,%ebp
  add    %r12d,%ebp
  sar    %ebp
  lea    (%r12,%r12,1),%eax
  cltq
  shl    $0x3,%rax
  mov    %rax,0x10(%rsp)
  lea    0x0(,%r8,8),%rax
  mov    %rax,0x30(%rsp)
  mov    %rsi,0x20(%rsp)
  movslq %edx,%rax
  shl    $0x3,%rax
  mov    %rax,0x38(%rsp)
  mov    %rdi,0x28(%rsp)
  lea    -0x8(,%rcx,8),%r13
  movl   $0x0,0x1c(%rsp)
  jmp    L67
L78:
  lea    (%rbx,%r14,1),%rcx
  mov    0x8(%rsp),%r8
  mov    %r15,%rsi
  mov    $0x0,%edi
L21:
  add    $0x1,%edi
  mov    %edi,%edx
  shr    $0x1f,%edx
  lea    (%rdi,%rdx,1),%eax
  and    $0x1,%eax
  sub    %edx,%eax
  lea    -0x1(%rax,%rax,1),%r9d
  movsd  (%r8),%xmm4
  add    $0x10,%r8
  movsd  -0x8(%r8),%xmm5
  cmp    $0x1,%r12d
  jle    L11
  mov    %r13,%rdx
  mov    $0x0,%eax
  pxor   %xmm2,%xmm2
  cvtsi2sd %r9d,%xmm2
L65:
  movsd  (%rsi,%rax,8),%xmm0
  movapd %xmm4,%xmm1
  mulsd  %xmm0,%xmm1
  movapd %xmm1,%xmm3
  addsd  (%rbx,%rax,8),%xmm3
  movsd  %xmm3,(%rbx,%rax,8)
  mulsd  %xmm5,%xmm0
  movapd %xmm0,%xmm3
  addsd  (%rcx,%rax,8),%xmm3
  movsd  %xmm3,(%rcx,%rax,8)
  mulsd  %xmm2,%xmm1
  addsd  (%rbx,%rdx,1),%xmm1
  movsd  %xmm1,(%rbx,%rdx,1)
  mulsd  %xmm2,%xmm0
  addsd  (%rcx,%rdx,1),%xmm0
  movsd  %xmm0,(%rcx,%rdx,1)
  add    $0x1,%rax
  sub    $0x8,%rdx
  cmp    %eax,%ebp
  jg     L65
L11:
  add    %r14,%rsi
  cmp    %r10d,%edi
  jne    L21
  mov    %r11d,%eax
  add    $0x1,%rax
  mov    %rax,%rdx
  shl    $0x4,%rdx
  add    %rdx,0x8(%rsp)
  imul   %r14,%rax
  add    %rax,%r15
L90:
  add    0x10(%rsp),%rbx
  sub    $0x1,%r11d
  sub    $0x1,%r10d
  cmp    $0xffffffff,%r11d
  je     L6
L89:
  test   %r11d,%r11d
  jns    L78
  jmp    L90
L6:
  addl   $0x1,0x1c(%rsp)
  mov    0x1c(%rsp),%eax
  mov    0x30(%rsp),%rsi
  add    %rsi,0x20(%rsp)
  mov    0x38(%rsp),%rsi
  add    %rsi,0x28(%rsp)
  cmp    %eax,0x4c(%rsp)
  je     L50
L67:
  mov    0x20(%rsp),%rdi
  mov    %rdi,%rbx
  mov    0x28(%rsp),%rax
  mov    %rax,0x8(%rsp)
  mov    0x48(%rsp),%edx
  mov    $0x0,%esi
  call   <memset@plt>
  cmpl   $0x0,0x90(%rsp)
  js     L6
  mov    0x90(%rsp),%r11d
  lea    0x1(%r11),%r10d
  mov    0x40(%rsp),%r15
  jmp    L89
L50:
  add    $0x58,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
```

assistant: ```c
void sp2fctest(double *sa, double *fa, double *poli, int nlev, int nlat, int nfc, int nt) {
  int lev, jm, jn, latn, lats, nsp2, is;
  double sar, sai;
  double *far, *fai, *pol;
  double *sal, *fal;
  double pval;
  nsp2 = (nt + 1) * (nt + 2);
  for (lev = 0; lev < nlev; lev++) {
    pol = poli;
    fal = fa + lev * nfc * nlat;
    sal = sa + lev * nsp2;
    memset(fal, 0, nfc * nlat * sizeof(double));
    for (jm = 0; jm <= nt; jm++) {
      for (jn = 0; jn <= nt - jm; jn++) {
        is = (jn + 1) % 2 * 2 - 1;
        sar = *sal++;
        sai = *sal++;
        far = fal;
        fai = fal + nlat;
        for (latn = 0; latn < nlat / 2; latn++) {
          lats = nlat - latn - 1;
          pval = pol[latn];
          far[latn] += pval * sar;
          fai[latn] += pval * sai;
          far[lats] += pval * sar * is;
          fai[lats] += pval * sai * is;
        }
        pol += nlat;
      }
      fal += 2 * nlat;
    }
  }
}
```