> I don't think that it does, since oparg gets totally reassigned each time
> we load a new instruction. EXTENDED_ARG actually needs to hack around
> this by advancing the instruction itself, updating oparg, and jumping
> straight into the next opcode.

Right, it's like this:

        TARGET(EXTENDED_ARG) {
            int oldoparg = oparg;
            NEXTOPARG();
            oparg |= oldoparg << 8;
            PRE_DISPATCH_GOTO();
            DISPATCH_GOTO();
        }

It's seems correct (the next arg will be NOP so nothing happens). But it's wasteful.