user: Please show me the C implementation that matches the assembly code listed below:

```asm
<checkers>:
  endbr64
  mov    %esi,%r9d
  mov    %rdx,%r10
  movslq %edi,%r11
  movslq %r8d,%r8
  mov    (%rcx,%r8,4),%ecx
  mov    %ecx,%eax
  cltd
  idiv   %edi
  mov    %edx,%esi
  mov    %ecx,%eax
  sub    %edx,%eax
  cltd
  idiv   %edi
  cltd
  idiv   %r9d
  test   %esi,%esi
  jle    L92
  sub    $0x1,%edi
  cmp    %esi,%edi
  jg     L80
  test   %edx,%edx
  jle    L52
  sub    $0x1,%r9d
  cmp    %edx,%r9d
  jg     L169
  lea    -0x1(%rdx),%ecx
  movslq %ecx,%rcx
  imul   %r11,%rcx
  movslq %esi,%rdi
  lea    (%r10,%rcx,1),%r8
  mov    $0x1,%eax
  cmpb   $0x78,(%r8,%rdi,1)
  je     L171
  lea    (%r10,%r11,1),%rax
  add    %rax,%rcx
  lea    -0x1(%rsi),%eax
  cltq
  cmpb   $0x78,(%rcx,%rax,1)
  jne    L99
  mov    $0x4,%eax
  ret
L92:
  test   %edx,%edx
  jle    L204
  sub    $0x1,%r9d
  cmp    %edx,%r9d
  jg     L165
  lea    -0x1(%rdx),%ecx
  movslq %ecx,%rcx
  imul   %r11,%rcx
  movslq %esi,%rdi
  lea    (%r10,%rcx,1),%r8
  mov    $0x1,%eax
  cmpb   $0x78,(%r8,%rdi,1)
  je     L171
  lea    (%r10,%r11,1),%rax
  add    %rax,%rcx
  lea    0x1(%rsi),%eax
  cltq
  cmpb   $0x78,(%rcx,%rax,1)
  je     L307
L99:
  movslq %edx,%rax
  imul   %r11,%rax
  lea    (%r10,%rax,1),%r8
  lea    -0x1(%rsi),%ecx
  movslq %ecx,%rcx
  cmpb   $0x78,(%r8,%rcx,1)
  je     L116
  sub    %r11,%rax
  movslq %esi,%rdi
  lea    (%r10,%rax,1),%rcx
  mov    $0x1,%eax
  cmpb   $0x78,(%rcx,%rdi,1)
  je     L171
  lea    0x1(%rsi),%eax
  cltq
  cmpb   $0x78,(%r8,%rax,1)
  jne    L130
  mov    $0x2,%eax
  ret
L204:
  lea    0x1(%rdx),%eax
  cltq
  imul   %r11,%rax
  movslq %esi,%rcx
  lea    (%r10,%rax,1),%rdi
  cmpb   $0x78,(%rdi,%rcx,1)
  je     L63
  sub    %r11,%rax
  lea    0x1(%rsi),%ecx
  movslq %ecx,%rcx
  add    %r10,%rax
  cmpb   $0x78,(%rax,%rcx,1)
  je     L166
L127:
  lea    0x1(%rdx),%ecx
  movslq %ecx,%rcx
  imul   %r11,%rcx
L197:
  sub    %r11,%rcx
  lea    (%r10,%rcx,1),%rax
  lea    -0x1(%rsi),%ecx
  movslq %ecx,%rcx
  cmpb   $0x78,(%rax,%rcx,1)
  je     L114
  lea    0x1(%rsi),%ecx
  movslq %ecx,%rcx
  cmpb   $0x78,(%rax,%rcx,1)
  je     L17
L130:
  movslq %edx,%rcx
  imul   %r11,%rcx
  add    %r10,%rcx
L255:
  sub    $0x1,%edx
  movslq %edx,%rdx
  imul   %r11,%rdx
  movslq %esi,%rdi
  lea    (%r10,%rdx,1),%r8
  mov    $0x1,%eax
  cmpb   $0x78,(%r8,%rdi,1)
  je     L171
  lea    0x1(%rsi),%eax
  cltq
  cmpb   $0x78,(%rcx,%rax,1)
  je     L211
  lea    (%r10,%r11,2),%rax
  add    %rdx,%rax
  cmpb   $0x78,(%rax,%rdi,1)
  sete   %al
  movzbl %al,%eax
  lea    (%rax,%rax,2),%eax
  ret
L165:
  lea    0x1(%rdx),%eax
  cltq
  imul   %r11,%rax
  movslq %esi,%rcx
  lea    (%r10,%rax,1),%rdi
  cmpb   $0x78,(%rdi,%rcx,1)
  je     L207
  lea    (%r11,%r11,1),%rdi
  sub    %rdi,%rax
  mov    %rax,%rcx
  movslq %esi,%rdi
  lea    (%r10,%rax,1),%r8
  mov    $0x1,%eax
  cmpb   $0x78,(%r8,%rdi,1)
  je     L171
  lea    (%r10,%r11,1),%rax
  add    %rax,%rcx
  lea    0x1(%rsi),%eax
  cltq
  cmpb   $0x78,(%rcx,%rax,1)
  jne    L273
  mov    $0x2,%eax
  ret
L52:
  lea    0x1(%rdx),%eax
  cltq
  imul   %r11,%rax
  movslq %esi,%rcx
  lea    (%r10,%rax,1),%rdi
  cmpb   $0x78,(%rdi,%rcx,1)
  je     L21
  sub    %r11,%rax
  lea    -0x1(%rsi),%ecx
  movslq %ecx,%rcx
  add    %r10,%rax
  cmpb   $0x78,(%rax,%rcx,1)
  jne    L127
  mov    $0x4,%eax
  ret
L169:
  lea    0x1(%rdx),%eax
  cltq
  imul   %r11,%rax
  movslq %esi,%rcx
  lea    (%r10,%rax,1),%rdi
  cmpb   $0x78,(%rdi,%rcx,1)
  je     L25
  lea    (%r11,%r11,1),%rdi
  sub    %rdi,%rax
  mov    %rax,%rcx
  movslq %esi,%rdi
  lea    (%r10,%rax,1),%r8
  mov    $0x1,%eax
  cmpb   $0x78,(%r8,%rdi,1)
  je     L171
  lea    (%r10,%r11,1),%rax
  add    %rax,%rcx
  lea    -0x1(%rsi),%eax
  cltq
  cmpb   $0x78,(%rcx,%rax,1)
  jne    L273
  mov    $0x4,%eax
  ret
L80:
  test   %edx,%edx
  jle    L248
  sub    $0x1,%r9d
  cmp    %edx,%r9d
  jle    L99
L273:
  movslq %edx,%rcx
  imul   %r11,%rcx
  add    %r10,%rcx
  lea    -0x1(%rsi),%edi
  movslq %edi,%rdi
  mov    $0x4,%eax
  cmpb   $0x78,(%rcx,%rdi,1)
  jne    L255
L171:
  ret
L248:
  lea    0x1(%rdx),%ecx
  movslq %ecx,%rcx
  imul   %r11,%rcx
  movslq %esi,%rdi
  lea    (%r10,%rcx,1),%r8
  mov    $0x3,%eax
  cmpb   $0x78,(%r8,%rdi,1)
  jne    L197
  jmp    L171
L63:
  mov    $0x3,%eax
  ret
L166:
  mov    $0x2,%eax
  ret
L307:
  mov    $0x2,%eax
  ret
L207:
  mov    $0x3,%eax
  ret
L21:
  mov    $0x3,%eax
  ret
L25:
  mov    $0x3,%eax
  ret
L114:
  mov    $0x4,%eax
  ret
L17:
  mov    $0x2,%eax
  ret
L116:
  mov    $0x4,%eax
  ret
L211:
  mov    $0x2,%eax
  ret
```

assistant: ```c
int checkers(int w, int h, char board[h][w], int stack[w * h], int tail, int done[h][w]) {
  int x = stack[tail] % w;
  int y = (stack[tail] - x) / w % h;
  if (x <= 0) {
    if (y <= 0) {
      if (board[y + 1][x] == 'x')
        return 3;
      else if (board[y][x + 1] == 'x')
        return 2;
    } else if (y >= h - 1) {
      if (board[y - 1][x] == 'x')
        return 1;
      else if (board[y][x + 1] == 'x')
        return 2;
    } else {
      if (board[y + 1][x] == 'x')
        return 3;
      else if (board[y - 1][x] == 'x')
        return 1;
      else if (board[y][x + 1] == 'x')
        return 2;
    }
  } else if (x >= w - 1) {
    if (y <= 0) {
      if (board[y + 1][x] == 'x')
        return 3;
      else if (board[y][x - 1] == 'x')
        return 4;
    } else if (y >= h - 1) {
      if (board[y - 1][x] == 'x')
        return 1;
      else if (board[y][x - 1] == 'x')
        return 4;
    } else {
      if (board[y + 1][x] == 'x')
        return 3;
      else if (board[y - 1][x] == 'x')
        return 1;
      else if (board[y][x - 1] == 'x')
        return 4;
    }
  }
  if (y <= 0) {
    if (board[y + 1][x] == 'x')
      return 3;
    else if (board[y][x - 1] == 'x')
      return 4;
    else if (board[y][x + 1] == 'x')
      return 2;
  } else if (y >= h - 1) {
    if (board[y][x - 1] == 'x')
      return 4;
    else if (board[y - 1][x] == 'x')
      return 1;
    else if (board[y][x + 1] == 'x')
      return 2;
  }
  if (board[y][x - 1] == 'x')
    return 4;
  else if (board[y - 1][x] == 'x')
    return 1;
  else if (board[y][x + 1] == 'x')
    return 2;
  else if (board[y + 1][x] == 'x')
    return 3;
  return 0;
}
```