user: 请将这段汇编代码片段转换成等效的C代码:

```asm
<mdct_butterfly_first>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  mov    %rdi,-0x28(%rbp)
  mov    %rsi,-0x30(%rbp)
  mov    %edx,-0x34(%rbp)
  mov    -0x34(%rbp),%eax
  cltq
  shl    $0x3,%rax
  lea    -0x40(%rax),%rdx
  mov    -0x30(%rbp),%rax
  add    %rdx,%rax
  mov    %rax,-0x20(%rbp)
  mov    -0x34(%rbp),%eax
  sar    %eax
  cltq
  shl    $0x3,%rax
  lea    -0x40(%rax),%rdx
  mov    -0x30(%rbp),%rax
  add    %rdx,%rax
  mov    %rax,-0x18(%rbp)
L8:
  mov    -0x20(%rbp),%rax
  add    $0x30,%rax
  movsd  (%rax),%xmm0
  mov    -0x18(%rbp),%rax
  add    $0x30,%rax
  movsd  (%rax),%xmm1
  subsd  %xmm1,%xmm0
  movsd  %xmm0,-0x10(%rbp)
  mov    -0x20(%rbp),%rax
  add    $0x38,%rax
  movsd  (%rax),%xmm0
  mov    -0x18(%rbp),%rax
  add    $0x38,%rax
  movsd  (%rax),%xmm1
  subsd  %xmm1,%xmm0
  movsd  %xmm0,-0x8(%rbp)
  mov    -0x20(%rbp),%rax
  add    $0x30,%rax
  movsd  (%rax),%xmm1
  mov    -0x18(%rbp),%rax
  add    $0x30,%rax
  movsd  (%rax),%xmm0
  mov    -0x20(%rbp),%rax
  add    $0x30,%rax
  addsd  %xmm1,%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x20(%rbp),%rax
  add    $0x38,%rax
  movsd  (%rax),%xmm1
  mov    -0x18(%rbp),%rax
  add    $0x38,%rax
  movsd  (%rax),%xmm0
  mov    -0x20(%rbp),%rax
  add    $0x38,%rax
  addsd  %xmm1,%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x28(%rbp),%rax
  add    $0x8,%rax
  movsd  (%rax),%xmm0
  movapd %xmm0,%xmm1
  mulsd  -0x8(%rbp),%xmm1
  mov    -0x28(%rbp),%rax
  movsd  (%rax),%xmm0
  mulsd  -0x10(%rbp),%xmm0
  mov    -0x18(%rbp),%rax
  add    $0x30,%rax
  addsd  %xmm1,%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x28(%rbp),%rax
  movsd  (%rax),%xmm0
  mulsd  -0x8(%rbp),%xmm0
  mov    -0x28(%rbp),%rax
  add    $0x8,%rax
  movsd  (%rax),%xmm1
  mulsd  -0x10(%rbp),%xmm1
  mov    -0x18(%rbp),%rax
  add    $0x38,%rax
  subsd  %xmm1,%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x20(%rbp),%rax
  add    $0x20,%rax
  movsd  (%rax),%xmm0
  mov    -0x18(%rbp),%rax
  add    $0x20,%rax
  movsd  (%rax),%xmm1
  subsd  %xmm1,%xmm0
  movsd  %xmm0,-0x10(%rbp)
  mov    -0x20(%rbp),%rax
  add    $0x28,%rax
  movsd  (%rax),%xmm0
  mov    -0x18(%rbp),%rax
  add    $0x28,%rax
  movsd  (%rax),%xmm1
  subsd  %xmm1,%xmm0
  movsd  %xmm0,-0x8(%rbp)
  mov    -0x20(%rbp),%rax
  add    $0x20,%rax
  movsd  (%rax),%xmm1
  mov    -0x18(%rbp),%rax
  add    $0x20,%rax
  movsd  (%rax),%xmm0
  mov    -0x20(%rbp),%rax
  add    $0x20,%rax
  addsd  %xmm1,%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x20(%rbp),%rax
  add    $0x28,%rax
  movsd  (%rax),%xmm1
  mov    -0x18(%rbp),%rax
  add    $0x28,%rax
  movsd  (%rax),%xmm0
  mov    -0x20(%rbp),%rax
  add    $0x28,%rax
  addsd  %xmm1,%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x28(%rbp),%rax
  add    $0x28,%rax
  movsd  (%rax),%xmm0
  movapd %xmm0,%xmm1
  mulsd  -0x8(%rbp),%xmm1
  mov    -0x28(%rbp),%rax
  add    $0x20,%rax
  movsd  (%rax),%xmm0
  mulsd  -0x10(%rbp),%xmm0
  mov    -0x18(%rbp),%rax
  add    $0x20,%rax
  addsd  %xmm1,%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x28(%rbp),%rax
  add    $0x20,%rax
  movsd  (%rax),%xmm0
  mulsd  -0x8(%rbp),%xmm0
  mov    -0x28(%rbp),%rax
  add    $0x28,%rax
  movsd  (%rax),%xmm1
  mulsd  -0x10(%rbp),%xmm1
  mov    -0x18(%rbp),%rax
  add    $0x28,%rax
  subsd  %xmm1,%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x20(%rbp),%rax
  add    $0x10,%rax
  movsd  (%rax),%xmm0
  mov    -0x18(%rbp),%rax
  add    $0x10,%rax
  movsd  (%rax),%xmm1
  subsd  %xmm1,%xmm0
  movsd  %xmm0,-0x10(%rbp)
  mov    -0x20(%rbp),%rax
  add    $0x18,%rax
  movsd  (%rax),%xmm0
  mov    -0x18(%rbp),%rax
  add    $0x18,%rax
  movsd  (%rax),%xmm1
  subsd  %xmm1,%xmm0
  movsd  %xmm0,-0x8(%rbp)
  mov    -0x20(%rbp),%rax
  add    $0x10,%rax
  movsd  (%rax),%xmm1
  mov    -0x18(%rbp),%rax
  add    $0x10,%rax
  movsd  (%rax),%xmm0
  mov    -0x20(%rbp),%rax
  add    $0x10,%rax
  addsd  %xmm1,%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x20(%rbp),%rax
  add    $0x18,%rax
  movsd  (%rax),%xmm1
  mov    -0x18(%rbp),%rax
  add    $0x18,%rax
  movsd  (%rax),%xmm0
  mov    -0x20(%rbp),%rax
  add    $0x18,%rax
  addsd  %xmm1,%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x28(%rbp),%rax
  add    $0x48,%rax
  movsd  (%rax),%xmm0
  movapd %xmm0,%xmm1
  mulsd  -0x8(%rbp),%xmm1
  mov    -0x28(%rbp),%rax
  add    $0x40,%rax
  movsd  (%rax),%xmm0
  mulsd  -0x10(%rbp),%xmm0
  mov    -0x18(%rbp),%rax
  add    $0x10,%rax
  addsd  %xmm1,%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x28(%rbp),%rax
  add    $0x40,%rax
  movsd  (%rax),%xmm0
  mulsd  -0x8(%rbp),%xmm0
  mov    -0x28(%rbp),%rax
  add    $0x48,%rax
  movsd  (%rax),%xmm1
  mulsd  -0x10(%rbp),%xmm1
  mov    -0x18(%rbp),%rax
  add    $0x18,%rax
  subsd  %xmm1,%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x20(%rbp),%rax
  movsd  (%rax),%xmm0
  mov    -0x18(%rbp),%rax
  movsd  (%rax),%xmm1
  subsd  %xmm1,%xmm0
  movsd  %xmm0,-0x10(%rbp)
  mov    -0x20(%rbp),%rax
  add    $0x8,%rax
  movsd  (%rax),%xmm0
  mov    -0x18(%rbp),%rax
  add    $0x8,%rax
  movsd  (%rax),%xmm1
  subsd  %xmm1,%xmm0
  movsd  %xmm0,-0x8(%rbp)
  mov    -0x20(%rbp),%rax
  movsd  (%rax),%xmm1
  mov    -0x18(%rbp),%rax
  movsd  (%rax),%xmm0
  addsd  %xmm1,%xmm0
  mov    -0x20(%rbp),%rax
  movsd  %xmm0,(%rax)
  mov    -0x20(%rbp),%rax
  add    $0x8,%rax
  movsd  (%rax),%xmm1
  mov    -0x18(%rbp),%rax
  add    $0x8,%rax
  movsd  (%rax),%xmm0
  mov    -0x20(%rbp),%rax
  add    $0x8,%rax
  addsd  %xmm1,%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x28(%rbp),%rax
  add    $0x68,%rax
  movsd  (%rax),%xmm0
  movapd %xmm0,%xmm1
  mulsd  -0x8(%rbp),%xmm1
  mov    -0x28(%rbp),%rax
  add    $0x60,%rax
  movsd  (%rax),%xmm0
  mulsd  -0x10(%rbp),%xmm0
  addsd  %xmm1,%xmm0
  mov    -0x18(%rbp),%rax
  movsd  %xmm0,(%rax)
  mov    -0x28(%rbp),%rax
  add    $0x60,%rax
  movsd  (%rax),%xmm0
  mulsd  -0x8(%rbp),%xmm0
  mov    -0x28(%rbp),%rax
  add    $0x68,%rax
  movsd  (%rax),%xmm1
  mulsd  -0x10(%rbp),%xmm1
  mov    -0x18(%rbp),%rax
  add    $0x8,%rax
  subsd  %xmm1,%xmm0
  movsd  %xmm0,(%rax)
  subq   $0x40,-0x20(%rbp)
  subq   $0x40,-0x18(%rbp)
  subq   $0xffffffffffffff80,-0x28(%rbp)
  mov    -0x18(%rbp),%rax
  cmp    -0x30(%rbp),%rax
  jae    L8
  nop
  nop
  pop    %rbp
  ret
```

assistant: ```c
void mdct_butterfly_first(double *trig, double *x, int points) {
  double *x1 = x + points - 8;
  double *x2 = x + (points >> 1) - 8;
  double r0;
  double r1;
  do {
    r0 = x1[6] - x2[6];
    r1 = x1[7] - x2[7];
    x1[6] += x2[6];
    x1[7] += x2[7];
    x2[6] = (r1 * trig[1] + r0 * trig[0]);
    x2[7] = (r1 * trig[0] - r0 * trig[1]);
    r0 = x1[4] - x2[4];
    r1 = x1[5] - x2[5];
    x1[4] += x2[4];
    x1[5] += x2[5];
    x2[4] = (r1 * trig[5] + r0 * trig[4]);
    x2[5] = (r1 * trig[4] - r0 * trig[5]);
    r0 = x1[2] - x2[2];
    r1 = x1[3] - x2[3];
    x1[2] += x2[2];
    x1[3] += x2[3];
    x2[2] = (r1 * trig[9] + r0 * trig[8]);
    x2[3] = (r1 * trig[8] - r0 * trig[9]);
    r0 = x1[0] - x2[0];
    r1 = x1[1] - x2[1];
    x1[0] += x2[0];
    x1[1] += x2[1];
    x2[0] = (r1 * trig[13] + r0 * trig[12]);
    x2[1] = (r1 * trig[12] - r0 * trig[13]);
    x1 -= 8;
    x2 -= 8;
    trig += 16;
  } while (x2 >= x);
}
```