RFR: 8189171: Move GC argument processing into GC specific classes

[Roman Kennke]

> I'm posting it to both hotspot-runtime-dev and hotspot-gc-dev because 
> it touches both areas (i.e. the GC interface).
>
> Currently, all GC related argument processing is done in 
> arguments.cpp, littering it with #ifdef INCLUDE_ALL_GCS and all sorts 
> of GC specific methods etc.
>
> In order to have a cleaner GC interface, I propose to move all that 
> code into GC specific classes under their GC specific directories.
>
> Since at this point in time we haven't created the XXXHeap subclasses 
> yet (and cannot, before having set up all the flags and arguments), I 
> propose to create a GC interface of which we create an instance as 
> soon as we have selected a GC, and then do argument processing there.
>
> This 'GC' interface is, at this point, meant as a sort of GC factory 
> interface. With this patch, it will only do argument processing. Later 
> I plan to add heap creation to it (which is currently done in 
> universe.cpp, with INCLUDE_ALL_GCS stuff and all the if (UseBlahGC) .. 
> else if .. else branch chains. My current prototype in the jdk10 
> sandbox also provides servicabilty support classes and some more 
> stuff, but we should decide later where to put this.
>
> I broke out some code paths into gc_factory.cpp (i.e. not in gc.cpp). 
> Those are all the code paths that select GC, create the right 
> instances, etc, in other words, the code paths that need to know about 
> all GCs. Ideally, this should be the only file that needs to know 
> about all the GCs. (Suggestions for improvement are welcome of course.)
>
> I tested this by running hotspot_gc jtreg tests, with normal fastdebug 
> and no-precompiled configurations. Everything passes fine.
>
> http://cr.openjdk.java.net/~rkennke/8189171/webrev.00/ 
> <http://cr.openjdk.java.net/%7Erkennke/8189171/webrev.00/>
>
> Opinions?
>
> Roman
>
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