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From Gordon Smith <gosm...@adobe.com>
Subject RE: [FalconJx] Prototype ActionScript -> JavaScript compiler code up in svn
Date Fri, 14 Dec 2012 19:31:28 GMT
I would be surprised if the BURM is faster than a simple top-down walk.

The main advantage of using a BURM is that it allows for optimizations to be easily coded
as alternate reductions with lower cost. Typically there are many difference sequences of
bottom-up reductions that could be applied to reduce the tree, and the BURM actually computes
the *lowest-cost*  sequence out of all possible sequences. (It is solving a complicated optimization
problem, although in an efficient way.) 

As a trivial example, in addition to writing a reduction for

    expression + expression

that reduces

    a + b

to instructions like

    push a
    push b


    1 + 2

to (inefficient) instructions like

    push 1
    push 2

you can write a reduction for

    constant + constant

and assign it a lower "cost" so that

    1 + 2

reduces to

    push 3

In the case of JavaScript, I'll bet that today's JavaScript engines are good at doing various
optimizations, so I don't see why an AS->JS cross-compiler needs to do them in advance
using a BURM.

- Gordon

-----Original Message-----
From: Alex Harui [mailto:aharui@adobe.com] 
Sent: Friday, December 14, 2012 10:34 AM
To: flex-dev@incubator.apache.org
Subject: Re: [FalconJx] Prototype ActionScript -> JavaScript compiler code up in svn

On 12/14/12 10:04 AM, "Michael Schmalle" <apache@teotigraphix.com> wrote:

> Quoting Alex Harui <aharui@adobe.com>:
>> On 12/14/12 4:24 AM, "Erik de Bruin" <erik@ixsoftware.nl> wrote:
>>> Dude,
>>> "goog" it is.
>>> I just needed a little pep-talk, I guess ;-)
>> Right now, I'm trying to get FalconJS to compile an MXML file and 
>> output the goog stuff.  That work got delayed because there were more 
>> distractions from the 4.9 release than I expected.  Then I will try 
>> to get the BURM/Reducer/Emitter to do the same.  Mike sent me what he 
>> tried to do in this area so I can reference it if needed.
>> We are definitely in prototype/research mode and different angles 
>> should be investigated.  The key to the "Apache Way" is that if we 
>> have to make choices in deciding what to ship, it should be done on technical merit.
> What context are you speaking from? compiler, js framework?
In theory, everything in Apache is decided on technical merit.  If your version of AS to JS
turns out to be faster and easier to maintain, it will win.

It will be interesting to figure out what to do if the BURM version is significantly faster,
but my gut says that won't be the case.

Alex Harui
Flex SDK Team
Adobe Systems, Inc.

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