A better JIT for Keiko

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The existing JIT for Keiko is very simple-minded, and does little more than translate each bytecode into the corresponding machine code. Either improve the translation by using one of the many JIT libraries now available, or adjust the Oberon compiler and the specification of the bytecode machine to free it of restrictive assumptions and produce a better pure-JIT implementation.

  • One idea: the compiler now knows too much about the layout of stack frames. In particular, it knows that the arguments of a procedure are on the stack at a certain offset from the frame base, effectively fixing the size of the frame head. By introducing appropriate instructions into the VM, it should be possible to make the code more independent of the exact stack layout, and that may make it possible to fit in with the native calling convention of some platforms. This should make it possible to merge the Oberon stack and the native subroutine stack, saving space and freeing up registers.