cmpxchg %bl,%cl  (al=22 bl=44 cl=33)
  al!=cl so al should equal cl (Result al=33 bl=44 cl=33)
cmpxchg %bl,%cl  (al=77 bl=55 cl=55)
  al==cl so cl should equal bl (Result al=55 bl=55 cl=55)
cmpxchg %bx,%cx  (ax=2222 bx=4444 cx=3333)
  ax!=cx so ax should equal cx (Result ax=3333 bx=4444 cx=3333)
cmpxchg %bx,%cx  (ax=7777 bx=5555 cx=5555)
  ax==cx so cx should equal bx (Result ax=5555 bx=5555 cx=5555)
cmpxchg %ebx,%ecx  (eax=22222222 ebx=44444444 ecx=33333333)
  eax!=ecx so eax should equal ecx (Result eax=33333333 ebx=44444444 ecx=33333333)
cmpxchg %ebx,%ecx  (eax=77777777 ebx=55555555 ecx=55555555)
  eax==ecx so ecx should equal ebx (Result eax=55555555 ebx=55555555 ecx=55555555)
cmpxchg %rbx,%rcx  (rax=222222222 rbx=444444444 rcx=333333333)
  rax!=rcx so rax should equal rcx (Result rax=333333333 rbx=444444444 rcx=333333333)
cmpxchg %rbx,%rcx  (rax=777777777 rbx=555555555 rcx=555555555)
  rax==rcx so ecx should equal rbx (Result rax=555555555 rbx=555555555 rcx=555555555)
