user: What is the c source code of the assembly code below:

```asm
<expansion_sum>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  mov    %edi,-0x54(%rbp)
  mov    %rsi,-0x60(%rbp)
  mov    %edx,-0x58(%rbp)
  mov    %rcx,-0x68(%rbp)
  mov    %r8,-0x70(%rbp)
  mov    -0x68(%rbp),%rax
  movsd  (%rax),%xmm0
  movsd  %xmm0,-0x38(%rbp)
  movl   $0x0,-0x40(%rbp)
  jmp    L53
L28:
  mov    -0x40(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x60(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  movsd  %xmm0,-0x30(%rbp)
  movsd  -0x38(%rbp),%xmm0
  addsd  -0x30(%rbp),%xmm0
  movsd  %xmm0,-0x28(%rbp)
  movsd  -0x28(%rbp),%xmm0
  subsd  -0x38(%rbp),%xmm0
  movsd  %xmm0,-0x20(%rbp)
  movsd  -0x28(%rbp),%xmm0
  subsd  -0x20(%rbp),%xmm0
  movsd  %xmm0,-0x18(%rbp)
  movsd  -0x30(%rbp),%xmm0
  subsd  -0x20(%rbp),%xmm0
  movsd  %xmm0,-0x10(%rbp)
  movsd  -0x38(%rbp),%xmm0
  subsd  -0x18(%rbp),%xmm0
  movsd  %xmm0,-0x8(%rbp)
  mov    -0x40(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x70(%rbp),%rax
  add    %rdx,%rax
  movsd  -0x8(%rbp),%xmm0
  addsd  -0x10(%rbp),%xmm0
  movsd  %xmm0,(%rax)
  movsd  -0x28(%rbp),%xmm0
  movsd  %xmm0,-0x38(%rbp)
  addl   $0x1,-0x40(%rbp)
L53:
  mov    -0x40(%rbp),%eax
  cmp    -0x54(%rbp),%eax
  jl     L28
  mov    -0x40(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x70(%rbp),%rax
  add    %rdx,%rax
  movsd  -0x38(%rbp),%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x40(%rbp),%eax
  mov    %eax,-0x3c(%rbp)
  movl   $0x1,-0x44(%rbp)
  jmp    L46
L19:
  mov    -0x44(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x68(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  movsd  %xmm0,-0x38(%rbp)
  mov    -0x44(%rbp),%eax
  mov    %eax,-0x40(%rbp)
  jmp    L40
L26:
  mov    -0x40(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x70(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  movsd  %xmm0,-0x30(%rbp)
  movsd  -0x38(%rbp),%xmm0
  addsd  -0x30(%rbp),%xmm0
  movsd  %xmm0,-0x28(%rbp)
  movsd  -0x28(%rbp),%xmm0
  subsd  -0x38(%rbp),%xmm0
  movsd  %xmm0,-0x20(%rbp)
  movsd  -0x28(%rbp),%xmm0
  subsd  -0x20(%rbp),%xmm0
  movsd  %xmm0,-0x18(%rbp)
  movsd  -0x30(%rbp),%xmm0
  subsd  -0x20(%rbp),%xmm0
  movsd  %xmm0,-0x10(%rbp)
  movsd  -0x38(%rbp),%xmm0
  subsd  -0x18(%rbp),%xmm0
  movsd  %xmm0,-0x8(%rbp)
  mov    -0x40(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x70(%rbp),%rax
  add    %rdx,%rax
  movsd  -0x8(%rbp),%xmm0
  addsd  -0x10(%rbp),%xmm0
  movsd  %xmm0,(%rax)
  movsd  -0x28(%rbp),%xmm0
  movsd  %xmm0,-0x38(%rbp)
  addl   $0x1,-0x40(%rbp)
L40:
  mov    -0x40(%rbp),%eax
  cmp    -0x3c(%rbp),%eax
  jle    L26
  addl   $0x1,-0x3c(%rbp)
  mov    -0x3c(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x70(%rbp),%rax
  add    %rdx,%rax
  movsd  -0x38(%rbp),%xmm0
  movsd  %xmm0,(%rax)
  addl   $0x1,-0x44(%rbp)
L46:
  mov    -0x44(%rbp),%eax
  cmp    -0x58(%rbp),%eax
  jl     L19
  mov    -0x3c(%rbp),%eax
  add    $0x1,%eax
  pop    %rbp
  ret
```

assistant: ```c
int expansion_sum(elen, e, flen, f, h)
int elen;
double *e;
int flen;
double *f;
double *h;
{
  double Q;
  double Qnew;
  int findex, hindex, hlast;
  double hnow;
  double bvirt;
  double avirt, bround, around;
  Q = f[0];
  for (hindex = 0; hindex < elen; hindex++) {
    hnow = e[hindex];
    Qnew = (double)(Q + hnow);
    bvirt = (double)(Qnew - Q);
    avirt = Qnew - bvirt;
    bround = hnow - bvirt;
    around = Q - avirt;
    h[hindex] = around + bround;
    Q = Qnew;
  }
  h[hindex] = Q;
  hlast = hindex;
  for (findex = 1; findex < flen; findex++) {
    Q = f[findex];
    for (hindex = findex; hindex <= hlast; hindex++) {
      hnow = h[hindex];
      Qnew = (double)(Q + hnow);
      bvirt = (double)(Qnew - Q);
      avirt = Qnew - bvirt;
      bround = hnow - bvirt;
      around = Q - avirt;
      h[hindex] = around + bround;
      Q = Qnew;
    }
    h[++hlast] = Q;
  }
  return hlast + 1;
}
```