NeoVM Runtime Versioning

[erikzhang]

Close neo-project/neo#2987

[shargon]

For allow versions inside the VM we need to change how the opcodes will be executed in different versions, by a jump table or similar, this pr doesn't close the issue https:/neo-project/neo-vm/issues/142

[erikzhang]

if (RuntimeVersion == xxx)
{
}
else
{
}

Doesn't it work?

[shargon]

It will work, but you are adding an extra comparation for each opcode instead of configure the environment and use it. It will be slower.

[erikzhang]

Then we need to create a Runtime class and move the entire runtime environment into it. I don't think it's necessary to do this right now.

[shargon]

We can start with this, but in my mind I was thinking in something like this

 protected ExecutionEngine(ReferenceCounter referenceCounter, ExecutionEngineLimits limits, RuntimeVersion version = RuntimeVersion.Latest)
        {
              if (RuntimeVersion == Latest)
              {
ExecuteInstruction = LastestExecuteInstruction;
              }
              else
              {
ExecuteInstruction = PreviousVersionOfExecuteInstruction;
              }
}

[erikzhang]

Changes to the instruction set also need to be considered. In this way, the verification of Script is different. Needs to be reconsidered.