Backtrace Debugger

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I am writing Backtrace Debugger. Part of the processor commands will be converted to the contrary, the rest will be recovered from memory, with the persistence context. Please advise what command processor, you can better convert to the contrary, and which are just a handle and store the result of work before and after.

For example the command XOR, better make a handle, or do the reverse command? How do I know the reverse command, in this case is difficult to make. Thanks  :8)