----- こんな感じのコード -----
if ( sw ) {
	data[num/8] |= 1<<(num%8);
} else {
	data[num/8] &= ~(1<<(num%8));
}


----- コンパイル結果 -----
VC6SP6
  mov     eax, dword ptr [esi+4]    ; [esi+4] = sw
  mov     ecx, edi
  test    eax, eax
  je      short label2
  and     ecx, dword 080000007h 
  jns     short label1
  dec     ecx
  or      ecx, -8
  inc     ecx
label1:
  ...


VC6SP5+VCPP
  mov     eax, dword ptr [esi+004h]
  mov     ecx, edi
  test    eax, eax
  and     ecx, dword 080000007h     ; ちょｗｗｗおまｗｗｗ
  je      short label2
  jns     short label1
  dec     ecx
  or      ecx, -8
  inc     ecx
label1:
  ...