Comment by alok-g
2 months ago
To the best I now understand, the jump address is allowed to be an expression using a specified bit variable. That would mean that the language has means to compile an expression for evaluation at the run time. If I am understanding correctly, then the power of flip jump is coming from those expressions, not the base flipjump instruction itself.
If I haven't understood this right, then I still do not follow how if statement works with flipjump.
@alok-g I'll be happy to explain - You don't understand it correctly. The flipjump assembly syntax does allow relating to an address with offsets/more advanced stuff, but that doesn't add anything to.the language. It' just adds comfort to the programmer - it's basically like adding labels to an assembly language - it's possible to write assembly without them, just much less convenient.
The power of flipjump results in self modifying code. If I jump to a address that have the [flip 0, jump 0x1000], then I'll get to 0x1000 afterwards, right? But if I flip some specific bit in this instruction before jumping to it, it will become [flip 0, jump 0x1080]. You can call this instruction "memory bit", and the part of jumping to it and resulting in one of two possible addresses 0x1000/0x1040 based on a specific bit in it - "read the memory bit". The action is reading as you get to different place based on the value stored in this instruction. This "read" can also be seen as an "if". How you write then? For example writing "1" whould be doing a "read", and in the "read 0" case - do a flip to this address, and in the "read 1" case don't flip this memory address bit.
I could follow the part you have explained. Thanks still though.
>> But if I flip some specific bit in this instruction before jumping to it
Isn't the 'if' really happening in the above phrase? The rest of it is a modified jump address based on the above 'if' and just jumps to the modified address.
Now if I understand this correctly, how to do the above 'if', i.e., flip the address bit or not based on some condition?
May be it would begin from some bit read from IO which modifies an address. I saw that memory-mapped IO is used.