user: 这段汇编代码用C语言表示是什么样的？

```asm
<SDL_imageFilterBitOr>:
  endbr64
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  mov    %rdx,%rbx
  sub    $0x8,%rsp
  test   %rsi,%rsi
  sete   %al
  test   %rdx,%rdx
  sete   %dl
  or     %dl,%al
  jne    L248
  mov    %rdi,%r12
  test   %rdi,%rdi
  je     L248
  mov    %ecx,%r13d
  test   %ecx,%ecx
  jne    L207
L155:
  xor    %eax,%eax
L186:
  add    $0x8,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  ret
  nopl   (%rax)
L207:
  xor    %eax,%eax
  mov    %rsi,%rbp
  call   <SDL_imageFilterMMXdetect@plt>
  test   %rax,%rax
  je     L135
  cmp    $0x7,%r13d
  ja     L250
L135:
  xor    %esi,%esi
L90:
  lea    0x1(%rbp),%r8
  mov    %r13d,%edi
  lea    0x1(%rsi),%ecx
  mov    %rbx,%rax
  sub    %r8,%rax
  sub    %esi,%edi
  lea    -0x1(%rdi),%edx
  cmp    $0xe,%rax
  seta   %r8b
  cmp    $0x6,%edx
  seta   %al
  cmp    %ecx,%r13d
  setae  %r9b
  and    %r9d,%eax
  test   %al,%r8b
  je     L0
  lea    0x1(%r12),%r8
  mov    %rbx,%rax
  sub    %r8,%rax
  cmp    $0xe,%rax
  jbe    L0
  cmp    %ecx,%r13d
  mov    $0x1,%eax
  cmovb  %eax,%edi
  cmp    $0xe,%edx
  jbe    L200
  lea    -0x10(%rdi),%eax
  xor    %ecx,%ecx
  shr    $0x4,%eax
  lea    0x1(%rax),%edx
  xor    %eax,%eax
  nop
L201:
  movdqu (%r12,%rax,1),%xmm0
  movdqu 0x0(%rbp,%rax,1),%xmm2
  add    $0x1,%ecx
  por    %xmm2,%xmm0
  movups %xmm0,(%rbx,%rax,1)
  add    $0x10,%rax
  cmp    %edx,%ecx
  jb     L201
  mov    %edx,%eax
  shl    $0x4,%eax
  mov    %eax,%edx
  add    %eax,%esi
  lea    (%r12,%rdx,1),%r8
  lea    0x0(%rbp,%rdx,1),%rcx
  add    %rbx,%rdx
  cmp    %eax,%edi
  je     L155
L113:
  mov    %edi,%r9d
  sub    $0x1,%edi
  sub    %eax,%edi
  sub    %eax,%r9d
  cmp    $0x6,%edi
  jbe    L168
  movq   (%r12,%rax,1),%xmm0
  movq   0x0(%rbp,%rax,1),%xmm1
  por    %xmm1,%xmm0
  movq   %xmm0,(%rbx,%rax,1)
  mov    %r9d,%eax
  and    $0xfffffff8,%eax
  mov    %eax,%edi
  add    %eax,%esi
  add    %rdi,%r8
  add    %rdi,%rcx
  add    %rdi,%rdx
  cmp    %eax,%r9d
  je     L155
L168:
  movzbl (%r8),%eax
  or     (%rcx),%al
  mov    %al,(%rdx)
  lea    0x1(%rsi),%eax
  cmp    %eax,%r13d
  jbe    L155
  movzbl 0x1(%r8),%eax
  or     0x1(%rcx),%al
  mov    %al,0x1(%rdx)
  lea    0x2(%rsi),%eax
  cmp    %eax,%r13d
  jbe    L155
  movzbl 0x2(%r8),%eax
  or     0x2(%rcx),%al
  mov    %al,0x2(%rdx)
  lea    0x3(%rsi),%eax
  cmp    %eax,%r13d
  jbe    L155
  movzbl 0x3(%r8),%eax
  or     0x3(%rcx),%al
  mov    %al,0x3(%rdx)
  lea    0x4(%rsi),%eax
  cmp    %eax,%r13d
  jbe    L155
  movzbl 0x4(%r8),%eax
  or     0x4(%rcx),%al
  mov    %al,0x4(%rdx)
  lea    0x5(%rsi),%eax
  cmp    %eax,%r13d
  jbe    L155
  movzbl 0x5(%r8),%eax
  add    $0x6,%esi
  or     0x5(%rcx),%al
  mov    %al,0x5(%rdx)
  cmp    %esi,%r13d
  jbe    L155
  movzbl 0x6(%r8),%eax
  or     0x6(%rcx),%al
  mov    %al,0x6(%rdx)
  jmp    L155
  nopl   0x0(%rax)
L250:
  mov    %r13d,%ecx
  mov    %rbx,%rdx
  mov    %rbp,%rsi
  mov    %r12,%rdi
  call   <SDL_imageFilterBitOrMMX@plt>
  test   $0x7,%r13b
  je     L155
  mov    %r13d,%esi
  and    $0xfffffff8,%esi
  cmp    %esi,%r13d
  jbe    L155
  mov    %esi,%eax
  add    %rax,%r12
  add    %rax,%rbp
  add    %rax,%rbx
  jmp    L90
  nopw   0x0(%rax,%rax,1)
L0:
  xor    %eax,%eax
  nopw   0x0(%rax,%rax,1)
L80:
  movzbl (%r12,%rax,1),%edx
  or     0x0(%rbp,%rax,1),%dl
  mov    %dl,(%rbx,%rax,1)
  add    $0x1,%rax
  lea    (%rsi,%rax,1),%edx
  cmp    %edx,%r13d
  ja     L80
  jmp    L155
L200:
  mov    %rbx,%rdx
  mov    %rbp,%rcx
  mov    %r12,%r8
  xor    %eax,%eax
  jmp    L113
L248:
  mov    $0xffffffff,%eax
  jmp    L186
```

assistant: ```c
int SDL_imageFilterBitOr(unsigned char *Src1, unsigned char *Src2, unsigned char *Dest, unsigned int length) {
  unsigned int i, istart;
  unsigned char *cursrc1, *cursrc2, *curdst;
  if ((Src1 == NULL) || (Src2 == NULL) || (Dest == NULL))
    return (-1);
  if (length == 0)
    return (0);
  if ((SDL_imageFilterMMXdetect()) && (length > 7)) {
    SDL_imageFilterBitOrMMX(Src1, Src2, Dest, length);
    if ((length & 7) > 0) {
      istart = length & 0xfffffff8;
      cursrc1 = &Src1[istart];
      cursrc2 = &Src2[istart];
      curdst = &Dest[istart];
    } else {
      return (0);
    }
  } else {
    istart = 0;
    cursrc1 = Src1;
    cursrc2 = Src2;
    curdst = Dest;
  }
  for (i = istart; i < length; i++) {
    *curdst = *cursrc1 | *cursrc2;
    cursrc1++;
    cursrc2++;
    curdst++;
  }
  return (0);
}
```