DISCLAIMER: These notes are from the defunct k8 project which precedes SquirrelJME. The notes for SquirrelJME start on 2016/02/26! The k8 project was effectively a Java SE 8 operating system and as such all of the notes are in the context of that scope. That project is no longer my goal as SquirrelJME is the spiritual successor to it.


Thought about including type information, but also thought about it being included in the StackMapTable. It would probably be best to include such information about types and also include it in the micro operations so that such operations can be checked and such.


It must be type safe, but I also must eat.


JStack::pushAll and JStack::popAll are very similar so they will need to be merged as one to simplify things.


I do not believe that micro-operations in operations would be efficient. The only reason I had thought of it was to group RISC operations together to represent singular operations. However, I can just set an extremely high PC address (shifted) and use that instead. I could either shift it left by 16 or use a smaller number. Most operations should not take up much space. Removing the need for micro operations would simplify things also since there would be no extra work needed to operate them in clusters.


I also would not need the OperandBuilder much, that can be squashed down a bit. Well it can be used where I can have methods that create operands that do something. So rather than have a next() as I currently have, I can have a copy() with inputs and outputs. Then that copy() will create the right operand as needed. There would also be meta things such as exception handlers that can be set and other things such as state information (for debugging).


The Operand class can just be an abstract class with a bunch of inner operations init. So rather than an enum things can be a bit more checked since an enum would complicate things a bit.


OK, so I have basic byte code operation decoding, what do I do next? There is the StackMapTable that needs decoding, but what about exceptions. The locals will be very different and it is quite possible that things would be different for every operand that gets executed (for locals). However, the StackMapTable might just choose a most common set of operations for each byte operation. So even though there may be 20 different variations of local values across all of the operations being executed the state of the locals for the exceptional jump may be just 2.


Now I am currently at INVOKESPECIAL, which is either a construction of an object or a super call.


The Java byte code decoder is complex because the Java class file format and its resulting byte codes is complex. But any complex mess should be contained within it with no real trouble. Provided the code generation is correct and works without issues. The later generation code where a pure register state machine would be exposed (after conversion from Java stack) will hopefully keep the later bits simple.


The JBOPPB I made for JavaByteOp for push and pop lists has just simplified handling of method invocations since they are dynamic according to the virtual machine. I will also need a new type of input for operands, that being a dynamic reference to another class. Those dynamic references would need to be added to the linker table for the class file when they are loaded.


Now I need to handle the various difference in the pop types based on the input, right now being that INVOKESPECIAL. This is just simple checking if the end of the array matches the required types.


Stack was not being set properly between operations but I believe the cause of that was just a lacking a set of a variable when I copy the stacks.


So after this I will need to finish off the DynamicLink and the creation of the special invokation operations. Then I believe after that I have this entire very basic constructor.