user: 请从给定的汇编指令推导出C源代码：

```asm
<ellipse>:
  endbr64
  push   %r15
  push   %r14
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  sub    $0x28,%rsp
  mov    %edi,%ebp
  mov    %edx,%ebx
  mov    %ecx,%edi
  mov    %edx,%ecx
  sub    %ebp,%ecx
  mov    %ecx,%edx
  neg    %edx
  cmovs  %ecx,%edx
  mov    %edi,%eax
  sub    %esi,%eax
  mov    %eax,%r8d
  neg    %r8d
  cmovs  %eax,%r8d
  mov    %r8d,%r10d
  mov    %r8d,0x18(%rsp)
  and    $0x1,%r8d
  mov    $0x1,%r9d
  sub    %edx,%r9d
  imul   %r10d,%r9d
  imul   %r10d,%r9d
  shl    $0x2,%r9d
  movslq %r9d,%r11
  mov    %r11,0x8(%rsp)
  lea    0x1(%r8),%r12d
  imul   %edx,%r12d
  mov    %r12d,%r15d
  imul   %edx,%r15d
  shl    $0x2,%r15d
  movslq %r15d,%r15
  sub    %edx,%r12d
  imul   %edx,%r12d
  movslq %r12d,%r12
  lea    (%r11,%r15,1),%r9
  add    %r9,%r12
  cmp    %ebp,%ebx
  jge    L31
  mov    %ebx,%ebp
  lea    (%rbx,%rdx,1),%ebx
L31:
  cmp    %esi,%edi
  cmovg  %esi,%edi
  mov    0x18(%rsp),%edx
  add    $0x1,%edx
  mov    %edx,%r13d
  shr    $0x1f,%r13d
  add    %edx,%r13d
  sar    %r13d
  add    %edi,%r13d
  mov    %r13d,%r14d
  sub    %r8d,%r14d
  imul   %ecx,%ecx
  shl    $0x3,%ecx
  mov    %ecx,0x1c(%rsp)
  imul   %eax,%eax
  shl    $0x3,%eax
  cltq
  mov    %rax,0x10(%rsp)
  jmp    L34
L7:
  add    $0x1,%ebp
  sub    $0x1,%ebx
  mov    0x10(%rsp),%rcx
  add    %rcx,0x8(%rsp)
  mov    0x8(%rsp),%rax
  add    %rax,%r12
L88:
  cmp    %ebx,%ebp
  jg     L35
L34:
  mov    %r13d,%esi
  mov    %ebx,%edi
  call   <setPixel@plt>
  mov    %r13d,%esi
  mov    %ebp,%edi
  call   <setPixel@plt>
  mov    %r14d,%esi
  mov    %ebp,%edi
  call   <setPixel@plt>
  mov    %r14d,%esi
  mov    %ebx,%edi
  call   <setPixel@plt>
  lea    (%r12,%r12,1),%rax
  cmp    %rax,%r15
  jl     L7
  add    $0x1,%r13d
  sub    $0x1,%r14d
  movslq 0x1c(%rsp),%rdx
  add    %rdx,%r15
  add    %r15,%r12
  cmp    %rax,0x8(%rsp)
  jle    L7
  lea    (%r12,%r12,1),%rax
  cmp    %r15,%rax
  jle    L88
  jmp    L7
L35:
  mov    %r13d,%eax
  sub    %r14d,%eax
  cmp    %eax,0x18(%rsp)
  jle    L8
  mov    %r14d,%r12d
  lea    (%r14,%r13,1),%eax
  mov    %eax,0x8(%rsp)
L59:
  mov    0x8(%rsp),%r15d
  sub    %r12d,%r15d
  lea    -0x1(%rbp),%r14d
  mov    %r15d,%esi
  mov    %r14d,%edi
  call   <setPixel@plt>
  lea    0x1(%rbx),%r13d
  mov    %r15d,%esi
  mov    %r13d,%edi
  call   <setPixel@plt>
  mov    %r12d,%esi
  mov    %r14d,%edi
  call   <setPixel@plt>
  mov    %r12d,%esi
  sub    $0x1,%r12d
  mov    %r13d,%edi
  call   <setPixel@plt>
  lea    (%r12,%r12,1),%edx
  mov    0x8(%rsp),%eax
  sub    %edx,%eax
  cmp    %eax,0x18(%rsp)
  jg     L59
L8:
  add    $0x28,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
```

assistant: ```c
void ellipse(int x0, int y0, int x1, int y1) {
  int a = abs(x1 - x0), b = abs(y1 - y0), b1 = b & 1;
  long dx = 4 * (1 - a) * b * b, dy = 4 * (b1 + 1) * a * a;
  long err = dx + dy + b1 * a * a, e2;
  if (x0 > x1) {
    x0 = x1;
    x1 += a;
  }
  if (y0 > y1)
    y0 = y1;
  y0 += (b + 1) / 2;
  y1 = y0 - b1;
  a *= 8 * a;
  b1 = 8 * b * b;
  do {
    setPixel(x1, y0);
    setPixel(x0, y0);
    setPixel(x0, y1);
    setPixel(x1, y1);
    e2 = 2 * err;
    if (e2 <= dy) {
      y0++;
      y1--;
      err += dy += a;
    }
    if (e2 >= dx || 2 * err > dy) {
      x0++;
      x1--;
      err += dx += b1;
    }
  } while (x0 <= x1);
  while (y0 - y1 < b) {
    setPixel(x0 - 1, y0);
    setPixel(x1 + 1, y0++);
    setPixel(x0 - 1, y1);
    setPixel(x1 + 1, y1--);
  }
}
```