[pypy-dev] Pypy custom interpreter JIT question

[Andrew Brown]

Thanks for the info!
That's all the questions I have, for now at least. Feel free to reply with
any more tips if you think of any.

I read over your posts you linked, Carl. They were certainly informative and
helpful, thanks. I'll keep thinking of ways to improve the performance of my
test interpreter, but it's so simple, I don't think there's much more that
can be done. The shared attribute maps described by that link don't really
apply here.

In any case, I'm satisfied with the speed. It's still beaten by a BF to C
translator combined with gcc -O2 though, that'd be a tough case to beat. =)

-Andrew

On Tue, Mar 29, 2011 at 5:33 AM, Armin Rigo <arigo at tunes.org> wrote:

> Hi Andrew,
>
> On Mon, Mar 28, 2011 at 7:21 PM, Andrew Brown <brownan at gmail.com> wrote:
> > When the optimizer encounters a "pure" function, it must compare the
> objects
> > "promote - promote the argument from a variable into a constant". Could
> this
> > be an appropriate alternate to the @purefunction solution? Or, I'm
> guessing,
> > does it just mean the name bracket_map won't change bindings, but does
> not
> > impose a restriction on mutating the dictionary?
>
> One point of view on 'promote' is to mean "this variable was red, but
> now turn it green (i.e. make it constant)".  It has no effect on a
> variable that is already green (= a constant).
>
> We have no support for considering that a dict is immutable, so it
> needs to be done with @purefunction.  But to be effective,
> @purefunction must receive constant arguments; so in one or two places
> in the source code of PyPy you will find a construction like:
>
>   x = hint(x, promote=True)   # turn x into a constant
>   some_pure_function(x)     # call this pure function on x
>
> Indeed, Carl Friedrich's blog series explains it nicely, but it should
> also mention that when the hints described in the blog are applied not
> to integer but to pointers, they apply only to the pointers
> themselves, not on the fields of the objects they point to.
>
>
> A bientôt,
>
> Armin.
>
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