Re: Does GWT optimize inefficient code?

What about the first could be optimized out - just the size() accessor? Most List implementations have a size field (see http://code.google.com/p/google-web-toolkit/source/browse/trunk/user/super/com/google/gwt/emul/java/util/ArrayList.java?r=6609#77 for the actual ArrayList used in compiled GWT code) that will be accessed instead of running a method. But if the loop modifies the list, rechecking the actual size is important. Again, in the case of ArrayList, any change made to the size of the list will itself change that same field.

For the second: it depends. If the compiler detects that there is a subclass of the current presenter that overrides getView(), then it will need to leave that method in so that it can call the right version. But if there is only one possible implementation at that point (current class is final, only one real impl ever, or various type/method tightening optimizations that already occur as part of the compilation process), then yes, it will almost certainly compile out to this._view.doAction() (the 'this' keyword is not implicit in JavaScript as it is in Java).

So the short answer is that it will probably do the sane thing. If it doesn't, it is either a more complex optimization than you think it is (for-each loop to for loop for example), or some specific Java semantics must be preserved (static initializers are a big one), or the compiler noticed something you forgot (another subclass of your Presenter that overrides getView()). I try compiling my app out in style PRETTY every few weeks/months and page through briefly to look for anything that surprises me, and it usually ends up that the surprises are what it *can* do than what it cannot.

On Friday, February 1, 2013 12:27:43 PM UTC-6, Joel Cairney wrote:

Dear forum,

I've searched as hard as I can, but I haven't found any information on what specific developer practices GWTs compiler optimizations might optimize out.  For instance:

for(int i = 0; i < myList.size(); i++) {...}

or in the presenter:

getView().doAction();

for every action, instead of:

_view.doAction();


Note that I'm not suggesting I plan to go through my code base and fix these, so please, please spare me the discussion on whether premature optimization is the root of all evil.  I would just like my curiousity satisfied.  Does GWT compiler change these code imperfections?

-Joel

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