user: 请从给定的汇编指令推导出C源代码:

```asm
<fit_line>:
  endbr64
  cmp    $0x2,%edx
  je     L43
  sub    $0x48,%rsp
  mov    %rdi,%rcx
  pxor   %xmm7,%xmm7
  cvtsi2sd %edx,%xmm7
  movsd  %xmm7,0x30(%rsp)
  movslq %edx,%rdi
  shl    $0x2,%rdi
  mov    -0x4(%rcx,%rdi,1),%eax
  sub    (%rcx),%eax
  mov    %eax,%r8d
  neg    %r8d
  cmovs  %eax,%r8d
  mov    -0x4(%rsi,%rdi,1),%eax
  sub    (%rsi),%eax
  mov    %eax,%edi
  neg    %edi
  cmovns %edi,%eax
  cmp    %eax,%r8d
  jge    L38
  test   %edx,%edx
  jle    L1
  mov    %edx,%edx
  mov    $0x0,%eax
  pxor   %xmm3,%xmm3
  movsd  %xmm3,0x28(%rsp)
  movsd  %xmm3,0x20(%rsp)
  movsd  %xmm3,0x10(%rsp)
  movsd  %xmm3,0x18(%rsp)
  movsd  %xmm3,0x8(%rsp)
L71:
  pxor   %xmm0,%xmm0
  cvtsi2sdl (%rcx,%rax,4),%xmm0
  pxor   %xmm1,%xmm1
  cvtsi2sdl (%rsi,%rax,4),%xmm1
  movsd  0x8(%rsp),%xmm7
  addsd  %xmm1,%xmm7
  movsd  %xmm7,0x8(%rsp)
  movsd  0x18(%rsp),%xmm4
  addsd  %xmm0,%xmm4
  movsd  %xmm4,0x18(%rsp)
  movapd %xmm1,%xmm2
  mulsd  %xmm1,%xmm2
  addsd  0x10(%rsp),%xmm2
  movsd  %xmm2,0x10(%rsp)
  mulsd  %xmm0,%xmm1
  addsd  0x20(%rsp),%xmm1
  movsd  %xmm1,0x20(%rsp)
  mulsd  %xmm0,%xmm0
  addsd  0x28(%rsp),%xmm0
  movsd  %xmm0,0x28(%rsp)
  add    $0x1,%rax
  cmp    %rax,%rdx
  jne    L71
  jmp    L51
L1:
  pxor   %xmm4,%xmm4
  movsd  %xmm4,0x28(%rsp)
  movsd  %xmm4,0x20(%rsp)
  movsd  %xmm4,0x10(%rsp)
  movsd  %xmm4,0x18(%rsp)
  movsd  %xmm4,0x8(%rsp)
  jmp    L51
L38:
  test   %edx,%edx
  jle    L58
  mov    %edx,%edx
  mov    $0x0,%eax
  pxor   %xmm4,%xmm4
  movsd  %xmm4,0x28(%rsp)
  movsd  %xmm4,0x20(%rsp)
  movsd  %xmm4,0x10(%rsp)
  movsd  %xmm4,0x18(%rsp)
  movsd  %xmm4,0x8(%rsp)
L67:
  pxor   %xmm1,%xmm1
  cvtsi2sdl (%rcx,%rax,4),%xmm1
  pxor   %xmm0,%xmm0
  cvtsi2sdl (%rsi,%rax,4),%xmm0
  movsd  0x8(%rsp),%xmm5
  addsd  %xmm1,%xmm5
  movsd  %xmm5,0x8(%rsp)
  movsd  0x18(%rsp),%xmm6
  addsd  %xmm0,%xmm6
  movsd  %xmm6,0x18(%rsp)
  movapd %xmm1,%xmm2
  mulsd  %xmm1,%xmm2
  addsd  0x10(%rsp),%xmm2
  movsd  %xmm2,0x10(%rsp)
  mulsd  %xmm0,%xmm1
  addsd  0x20(%rsp),%xmm1
  movsd  %xmm1,0x20(%rsp)
  mulsd  %xmm0,%xmm0
  addsd  0x28(%rsp),%xmm0
  movsd  %xmm0,0x28(%rsp)
  add    $0x1,%rax
  cmp    %rdx,%rax
  jne    L67
L51:
  movsd  0x8(%rsp),%xmm3
  movapd %xmm3,%xmm1
  mulsd  %xmm3,%xmm1
  movsd  0x10(%rsp),%xmm0
  mulsd  0x30(%rsp),%xmm0
  subsd  %xmm1,%xmm0
  movsd  %xmm0,0x38(%rsp)
  ucomisd D15(%rip),%xmm0
  jp     L84
  je     L88
L84:
  movsd  0x18(%rsp),%xmm7
  movapd %xmm7,%xmm3
  movsd  0x10(%rsp),%xmm2
  mulsd  %xmm2,%xmm3
  movsd  0x8(%rsp),%xmm5
  movapd %xmm5,%xmm0
  movsd  0x20(%rsp),%xmm6
  mulsd  %xmm6,%xmm0
  subsd  %xmm0,%xmm3
  movsd  0x38(%rsp),%xmm1
  divsd  %xmm1,%xmm3
  movapd %xmm6,%xmm4
  movsd  0x30(%rsp),%xmm8
  mulsd  %xmm8,%xmm4
  movapd %xmm5,%xmm0
  mulsd  %xmm7,%xmm0
  subsd  %xmm0,%xmm4
  divsd  %xmm1,%xmm4
  movapd %xmm8,%xmm0
  mulsd  %xmm3,%xmm0
  mulsd  %xmm3,%xmm0
  addsd  0x28(%rsp),%xmm0
  mulsd  %xmm4,%xmm2
  movapd %xmm2,%xmm1
  mulsd  %xmm4,%xmm1
  addsd  %xmm1,%xmm0
  mulsd  %xmm3,%xmm7
  movapd %xmm7,%xmm1
  mulsd  %xmm4,%xmm6
  addsd  %xmm6,%xmm1
  mulsd  %xmm4,%xmm3
  mulsd  %xmm5,%xmm3
  subsd  %xmm3,%xmm1
  addsd  %xmm1,%xmm1
  subsd  %xmm1,%xmm0
  movapd %xmm8,%xmm1
  subsd  D5(%rip),%xmm1
  divsd  %xmm1,%xmm0
  add    $0x48,%rsp
  ret
L58:
  pxor   %xmm4,%xmm4
  movsd  %xmm4,0x28(%rsp)
  movsd  %xmm4,0x20(%rsp)
  movsd  %xmm4,0x10(%rsp)
  movsd  %xmm4,0x18(%rsp)
  movsd  %xmm4,0x8(%rsp)
  jmp    L51
L88:
  lea    D1(%rip),%rdi
  call   <printf@plt>
  jmp    L84
L43:
  pxor   %xmm0,%xmm0
  ret
```

tool_calls: name: retrieve_data
arguments: label: D15
type_guessed: f64
name: retrieve_data
arguments: label: D5
type_guessed: f64
name: retrieve_data
arguments: label: D1
type_guessed: string

tool: D15: 0

tool: D5: 2

tool: D1: Error - div by zero in fit_line


assistant: ```c
double fit_line(int *xp, int *yp, int npts) {
  int i;
  double x, y, n;
  double del, a, b, var;
  double sx = 0.0, sy = 0.0, sxx = 0.0, sxy = 0.0, syy = 0.0;
  if (npts == 2)
    return (0.0);
  n = (double)npts;
  if ((((xp[npts - 1] - xp[0]) > 0) ? ((xp[npts - 1] - xp[0])) : (-(xp[npts - 1] - xp[0]))) >= (((yp[npts - 1] - yp[0]) > 0) ? ((yp[npts - 1] - yp[0])) : (-(yp[npts - 1] - yp[0])))) {
    for (i = 0; i < npts; ++i) {
      x = (double)xp[i];
      y = (double)yp[i];
      sx += x;
      sy += y;
      sxx += x * x;
      sxy += x * y;
      syy += y * y;
    }
  } else {
    for (i = 0; i < npts; ++i) {
      y = (double)xp[i];
      x = (double)yp[i];
      sx += x;
      sy += y;
      sxx += x * x;
      sxy += x * y;
      syy += y * y;
    }
  }
  del = n * sxx - sx * sx;
  if (del == 0.0)
    printf("Error - div by zero in fit_line\n");
  a = (sxx * sy - sx * sxy) / del;
  b = (n * sxy - sx * sy) / del;
  var = (syy + n * a * a + sxx * b * b - 2.0 * (a * sy + b * sxy - a * b * sx)) / (n - 2);
  return (var);
}
```