Re: Controlling Inling in GWT compiler

[Peter Donald]

>
> I still suspect (having not experimented with it) that the "return this"
> aliasing will still confuse matters, at least without deliberate code in
> closure to handle it. At least with strings, it isn't smart enough:
> https://closure-compiler.appspot.com/home#code%3D%252F%252F%2520%253D%
> 253DClosureCompiler%253D%253D%250A%252F%252F%2520%2540compilation_level%
> 2520ADVANCED_OPTIMIZATIONS%250A%252F%252F%2520%2540output_file_name%
> 2520default.js%250A%252F%252F%2520%253D%253D%
> 252FClosureCompiler%253D%253D%250A%250A%252F%252F%2520ADD%
> 2520YOUR%2520CODE%2520HERE%250Afunction%2520A()%257Bthis.
> str%253D%27%27%257D%253B%250AA.prototype.b%2520%253D%
> 2520function(string)%2520%257Bthis.str%252B%253Dstring%
> 253B%2520return%2520this%253B%257D%253B%250AA.prototype.c%
> 2520%253D%2520function()%2520%257Breturn%2520this.str%257D%
> 253B%250A%250Aconsole.log(new%2520A().b(%2522a%2522).b(
> window.prompt()).b(%2522b%2522).c())%253B
> I'm having a hard time modeling this in plain JS to get it to treat the
> constructor like an object, so as to correctly handle the "return this".
> Might be better as a @JsOverlay...
>

I should note I tried lots of different ways to try and get this working
and came up with nothing. If you do figure it out - I would love to see
what it looks like ;)

-- 
Cheers,

Peter Donald

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Re: Controlling Inling in GWT compiler

[Peter Donald]

On Wed, Oct 18, 2017 at 1:14 PM, Colin Alworth  wrote:

> For the first one, chaining methods has the unfortunate detail that each
> method has a return value, which the next object is called on. To my
> knowledge, there is no optimization in the compiler which currently can
> undo the presence of the return value, and recognize that the method
> returns "this" (or a param, some other easily aliased value) as a special
> case.
>

Ok. I think I have been spoilt by working on the JVM for so long. I just
assumed that GWT and/or Closure could do escape analysis and inline
non-escaping objects into the current scope. I assume this is not the case
then? It would explain the resulting code.

Lets assume that "str" was only one char, since we are compiling after all,
> 40 chars for the "idiomatic" js version, 37 chars for staticified version,
> 50 for the "inlined" version.
>

Hmm ... I guess I was too down in the trenches to think high level enough.
I like this idea. In my context the following is the lay of the land

*Current Java Input: *
new InputBuilder().type( "checkbox" ).className( "foo" ).child( "Hello"
).build()

*Naive Javascript output (71 chars)*
React.createElement('input',{type:'checkbox',className:'foo'},'Hello')

*Current GWT output: (lots)*
function up(a){var b,c;c=a.b;b=a.a;return
$wnd.React.createElement.apply(null,[hw,c].concat(b))}
function vp(a,b){a.a.concat(b);return a}
function wp(a){a.b['className']='foo';return a}
function xp(a){a.b['type']='checkbox';return a}
a=up(vp(wp(xp(new yp)),'Hello'))

*Non-reusable GWT output: (82 chars)*
function wp(a){a.b['className']='foo';return a}
a=up(vp(wp(xp(new yp)),'Hello'))

*Hypothetical Less Naive ES3 Javascript output (45 chars)*
ab(dc,{'type':xs,'className':'foo'},'Hello')

*Hypothetical Less Naive ES6 Javascript output (36 chars)*
ab(dc,{[eg]:xs,[gg]:'foo'},'Hello')

So even if you strip the potentially reusable code out of the current GWT
output the non reusable chunk is still 82 characters which is 9 characters
more than the most naive javascript implementation. However a more
optimized javascript implementation that aliases the methods and constants
comes in at 36 chars. However I think that uses some ES6 features ([gg] as
key).

I still suspect (having not experimented with it) that the "return this"
> aliasing will still confuse matters, at least without deliberate code in
> closure to handle it. At least with strings, it isn't smart enough:
>

Right.


> I played with a similar optimization in GWT a few years ago, but ended up
> not finishing it. It mostly dealt with trying to deal with compile-time
> strings and avoiding runtime regular expressions on them, but I abandoned
> it. If there is enough interest in this, I think I at least have the
> working knowledge to give it a shot... but lets be sure that we get
> something out of it.
>

To be perfectly honest I have no idea on the state of either the GWT or
closure optimizer so could not rightly say but I suspect that without an
escape analysis this may be a very difficult optimization to get right and
probably a lot of work ;) I remember spending weeks  (months?) trying to
get some similar optimizations working in a past life and I mostly failed !
But if you want to try don't let me stop you.

create({a:'asdf',b:1,c:false});
> create(c(b(a({},'asdf'),1),false);
> Literal is 31 bytes, chained is 35, so two bytes per setter (plus the cost
> of the setter method, which can then be reused). Might not be worth more
> than a few hours of time, but then again, the work could lead to other
> unexpected benefits...
>


I think the optimization would offer a fairly significant improvement but I
also think it is a massive amount of work. Maybe time would be better spent
elsewhere.

Anyhoo interesting idea - thanks for your reply.

-- 
Cheers,

Peter Donald

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