RFR: 8004643 Reduce javac space overhead introduced with compiler support for repeating annotations

Fri May 31 19:14:09 PDT 2013

More from the javac janitation crew, cleaning up the odds and ends.

This is a relatively simple fix for the space overhead introduced by 
allocating an Annotations object for every Symbol.  The fix is to hide 
the Annotations object behind methods in Symbol (which also cleans up 
the client code a bunch) and to lazily allocate the Annotations object 
if and only if it is needed.  If the reference to the Annotations object 
is null, that means "no annotations on this symbol". (I tried using an 
immutable empty object, but it caused more clutter than it saved.)

Most notably, Annotations is not itself changed by this changeset.

The savings on a JDK build are significant, going from every Symbol 
having an Annotations object, to < 1% of Symbols needing an Annotations 
object ... from 4,024,455 to just 35,272.  In the table below, each row 
is a separate javac compilation in the JDK build.  The left hand block 
of numbers comes from a recent build of TL; the right hand block of 
numbers comes from a build of TL with the patch applied.  There may be 
more optimizations possible, by further improving the checks on whether 
a new Annotations object is required.

There's a couple of related minor cleanups here as well. Going forward, 
it would be nice to clean up the method names on Annotations and the 
wrapper methods on Symbol. There's an inconsistent set of names using 
fragments like {(empty), Raw, Declaration, Type} x {Attributes, 
Annotations}.   Once we can decide on a better set of names, we can do a 
separate "renaming only" changeset for that.

The webrev is available at 
http://cr.openjdk.java.net/~jjg/8004643/webrev.00/  It is against 
tl/langtools.

-- Jon

	OLD 	

	NEW 	

	Symbols 	Annotations 	% 	
	Symbols 	Annotations 	%

	269,144 	269,144 	100.00% 	
	269,191 	1,817 	0.67%

	4,463 	4,463 	100.00% 	
	4,463 	32 	0.72%

	39,845 	39,845 	100.00% 	
	39,845 	40 	0.10%

	2,276 	2,276 	100.00% 	
	2,276 	7 	0.31%

	224,546 	224,546 	100.00% 	
	224,546 	182 	0.08%

	356,137 	356,137 	100.00% 	
	356,137 	343 	0.10%

	8,610 	8,610 	100.00% 	
	8,610 	37 	0.43%

	428,097 	428,097 	100.00% 	
	428,097 	4,884 	1.14%

	49,031 	49,031 	100.00% 	
	49,031 	253 	0.52%

	1,338 	1,338 	100.00% 	
	1,338 	4 	0.30%

	2,016,962 	2,016,962 	100.00% 	
	2,017,279 	9,824 	0.49%

	2,642 	2,642 	100.00% 	
	3,944 	110 	2.79%

	3,937 	3,937 	100.00% 	
	2,642 	78 	2.95%

	3,944 	3,944 	100.00% 	
	3,937 	112 	2.84%

	4,015 	4,015 	100.00% 	
	4,015 	101 	2.52%

	5,361 	5,361 	100.00% 	
	4,462 	120 	2.69%

	4,779 	4,779 	100.00% 	
	5,361 	139 	2.59%

	3,855 	3,855 	100.00% 	
	4,281 	88 	2.06%

	4,281 	4,281 	100.00% 	
	4,779 	135 	2.82%

	4,462 	4,462 	100.00% 	
	4,447 	107 	2.41%

	4,546 	4,546 	100.00% 	
	4,546 	102 	2.24%

	5,795 	5,795 	100.00% 	
	3,855 	28 	0.73%

	4,447 	4,447 	100.00% 	
	5,795 	144 	2.48%

	5,176 	5,176 	100.00% 	
	6,496 	117 	1.80%

	6,496 	6,496 	100.00% 	
	5,176 	144 	2.78%

	6,056 	6,056 	100.00% 	
	6,056 	118 	1.95%

	5,759 	5,759 	100.00% 	
	5,759 	112 	1.94%

	4,926 	4,926 	100.00% 	
	4,926 	106 	2.15%

	1,025 	1,025 	100.00% 	
	6,468 	136 	2.10%

	3,697 	3,697 	100.00% 	
	4,185 	43 	1.03%

	6,468 	6,468 	100.00% 	
	7,804 	139 	1.78%

	4,185 	4,185 	100.00% 	
	3,697 	40 	1.08%

	7,809 	7,809 	100.00% 	
	1,025 	12 	1.17%

	8,878 	8,878 	100.00% 	
	8,878 	170 	1.91%

	7,804 	7,804 	100.00% 	
	7,809 	173 	2.22%

	1,029 	1,029 	100.00% 	
	10,420 	164 	1.57%

	1,403 	1,403 	100.00% 	
	8,011 	183 	2.28%

	10,420 	10,420 	100.00% 	
	10,024 	227 	2.26%

	8,011 	8,011 	100.00% 	
	11,303 	190 	1.68%

	10,024 	10,024 	100.00% 	
	12,225 	231 	1.89%

	11,303 	11,303 	100.00% 	
	1,029 	12 	1.17%

	12,225 	12,225 	100.00% 	
	1,403 	28 	2.00%

	15,827 	15,827 	100.00% 	
	15,827 	173 	1.09%

	12,642 	12,642 	100.00% 	
	12,686 	166 	1.31%

	124,653 	124,653 	100.00% 	
	124,654 	2,824 	2.27%

	39,797 	39,797 	100.00% 	
	39,797 	691 	1.74%

	255,866 	255,866 	100.00% 	
	255,910 	10,386 	4.06%

	TOTAL 	4,023,992 	4,023,992 	100.00% 	
	4,024,445 	35,272 	0.88%

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