class initialization check overhead

Thu Oct 24 05:34:00 GMT 2002

On Thu, 2002年10月24日 at 02:10, C. van Reeuwijk wrote:
> - If a class has an empty init, change it to a superclass init (repeat).
> - Eliminate inits of java.lang.Object (since it's empty).
> - Within a method, keep track of the classes already initialized,
> and don't initialize a class again if you know for sure that it, or a
> subclass, has already been initialized.

I know we used to do this (without the subclass trick), by generating
something like the following for "x = foo.bar.y"...
 int _foo_bar__initialized_p = 0; // once per method
 if (! _foo_bar__initialized_p) // each reference would do this
 {
 initialize foo.bar
 _foo_bar_initialized_p = 1;
 }
 x = foo.bar.y;
The compiler's normal optimizations will remove useless initializations,
and even eliminate _foo_bar__initialized_p from the final output. 
However, I believe this was changed somehow since the original
implementation. To what, I don't recall.
apbianco once suggested also annotating the .class files with notes on
which classes each method guaranteed to initialize.
> - Inline small inits.

AG