Re: Jit Implementation

Philip Herron <herron.philip@googlemail.com> writes:
>From what i understand to Jit some kind of language, do your parsing
>into an IR maybe some optimizations to a code generator. So ok if we
>have successfully output target code for the processor would you use
>simply a system assembler or what i see some people have runtime
>assemblers to assemble this code, then where would this target code
>go?
>
>Then how do you link it in a useful way?
>
>And ultimately how would you execute this


To reduce the reinvent-the-wheel overhead, you might consider using
a library to help with the mechanics of this. For example, I have
heard of (but not personally used) VCODE:
    http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.25.8634
    http://pdos.csail.mit.edu/~engler/pldi96-abstract.html
    http://www.stanford.edu/~engler/vcode-pldi.ps


Abstract:
    We present vcode, a portable, extensible, very fast dynamic code
    generation system. An important feature of vcode is that it generates
    machine code ``in-place'' without the use of intermediate data
    structures. Eliminating the need to construct and consume an
    intermediate representation at runtime makes vcode both efficient
    and extensible. vcode dynamically generates code at an approximate
    cost of six to ten instructions per generated instruction, making
    it over an order of magnitude faster than the most efficient
    general-purpose code generation system in the literature.


    Dynamic code generation is relatively well known within the compiler
    community. However, due in large part to the lack of a publicly
    available dynamic code generation system, it has remained a curiosity
    rather than a widely used technique. A practical contribution of
    this work is the free, unrestricted distribution of the vcode system,
    which currently runs on the MIPS, SPARC, and Alpha architectures.


ciao,


--
-- "Jonathan Thornburg [remove -animal to reply]" <jthorn@astro.indiana-zebra.edu>
      Dept of Astronomy, Indiana University, Bloomington, Indiana, USA
      "C++ is to programming as sex is to reproduction. Better ways might
        technically exist but they're not nearly as much fun." -- Nikolai Irgens

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