Projects/frostbyte-39

Bytecode needs/design goals/whatever

• Initial overview: do it a function at a time. Function calls still

do callAsFunction:

• • But can setup the arguments on the stack frame, along with the length.

   List integration with that may be tricky, especially for native calls.

• Goal #1: cheap temporaries --- make the wiring inexpensive
  • M.O.: my tendency is towards simpler bytecode (think Copy4, Copy8),

   for simpler optimization; critical for that, nice otherwise

• • All accesses to temporaries, locals should be simple offsets
  • Can compute stack size need easily: just have a

    ByteCodeTemp class that links in to a counter in 
    compilation context. So there is no need to put in conditionals 
    on push/pop. Also, this gives the temporaries an explicit name,
    which can be in a shared namespace with locals. Somewhat (see below)

• • Keep track of stack pointer?
    • Pro: less ++ / --
    • Con: garbage can linger
  • Basic compilation interface for evaluate:

        void evaluateTo(CompileState* comp, ByteCodeTemp& dest);

• • A simple peephole optimization on reads for this:

        t1 = local;
        t2 = t1 * t3;
   will probably be a good idea. Not sure if full copy prop is worth anything

 * Limit reallocations -- entering a context should do only a single 
   stack frame allocation

• Literals should go into some sort of a symbol table

• Obviously, would like globals to used all of the above

 * Problem: symbol tables, stack frames might grow. May require 
   segmenting them an multiple subst