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Date: Fri, 5 Jun 2009 18:04:08 +0100
Message-ID: <af54caaf0906051004s74a11a04v637d3c745b15845f@mail.gmail.com>
To: Graham Kelly <grahamk@facebook.com>
Cc: PHP Internals <internals@lists.php.net>, Brian Shire <shire@facebook.com>
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Subject: Re: Optimizer discussion
From: paul.biggar@gmail.com (Paul Biggar)

Hi Graham,

On Fri, Jun 5, 2009 at 12:03 PM, Paul Biggar<paul.biggar@gmail.com> wrote:
>> Why not start off with the big stuff, dataflow. I personally believe tha=
t working out good data flow for PHP is key to getting good optimizations. =
But you are right, its a very tricky thing to do and in some cases impossib=
le. Ultimately, I would like to move a lot of the optimizer work more into =
this direction and use the data flow to build a basic platform for code ana=
lysis on which optimizations can be done. For now though, pecl/optimizer is=
 "dumb" about data types :-)
>
>
> And now the hard stuff. To avoid me repeating myself, let me just pimp
> my Tech Talk. Have a look at
> http://www.youtube.com/watch?v=3DkKySEUrP7LA from about the 30:45 mark
> until just before the 47:00 mark (slides at
> https://www.cs.tcd.ie/~pbiggar/paul_biggar_google_18_mar_2009_notes.pdf).
> That highlights most of the problems, and vaguely hints at their
> solution. We can go into much greater detail on the solutions after.


Based on the fact that you want to do dataflow, I wonder if its a good
idea to think about co-opting the phc optimizer to perform analysis on
bytecode. To my mind this seems much easier than re-implementing from
scratch. As I mentioned before, this incorporates about 2 years of
work (much of it research of course, so it might not take as long to
replicate). This would mean you could go straight to performing
analyses (though there will no doubt be work required on the optimizer
itself).

Technically speaking, this isn't a big problem. We'd probably need to
change the phc MIR to mirror the bytecode (no harm anyway in terms of
correctness), and have a bytecode-reader and -writer (though this
needn't involve serializing - likely a small interface instead).
Politically, I assume it won't be a problem either, since its in PECL.


Thoughts?

Paul




--=20
Paul Biggar
paul.biggar@gmail.com