Opcode.java fields (require,ret) are wrongly named, replace them with (lookupDepth, popCount, pushCount)

[SergioDemianLerner]

The Opcode class has the fields:

    private final int require;
  ...
    private final int ret;

And a comment describes them as : in-args,out-args
But they are not what is seems.

require is really a stack lookupDepth.
ret cannot be easily explained, it is basically (lookupDepth+pushCount).

I suggest removing ret and require and replace them with 3 arguments: (lookupDepth, popCount, pushCount).
While popCount won't be referenced in the code, it's useful to have it as reference and for debugging.
For most opcodes the definition won't change. For DUPx, SWAPx, DUPN, SWAPN it will change.

verifyStackOverflow() will also need to be modified.

[SergioDemianLerner]

I think the original meaning was that you could implement those opcodes by removing all elements until lookupDepth, and them pushing back the same elements plus pushCount.

Not very intuitive, because that's not how it is implemented, but that was the code author's idea.

[Vovchyk]

this will require to refactor all opcodes in the OpCode enum, won't it? Seems there are a lot of them. Can we just add toString() method to that enum, so that we could print opcode internals in a format that fits our debugging purposes?

[SergioDemianLerner]

I don't mind doing the re-factor. In all cases except DUPx, SWAPx, DUPN, SWAPN, it will be simply duplicating the "retire" value so the line:
ADD(0x01, 2, 1, VERY_LOW_TIER),
will become:
ADD(0x01, 2, 2, 1, VERY_LOW_TIER),