RFR (XL): 6934604: enable parts of EliminateAutoBox by default

[Vladimir Kozlov]

http://cr.openjdk.java.net/~kvn/6934604.v2/webrev/

Resurrected autobox elimination code and enabled it by default.
Added new experimental C2 flag in preparation for 8012974.

After static fields were moved to JavaMirror the existing autobox 
elimination code (LoadNode::eliminate_autobox()) stopped working because 
graph was changed. Fixed it for loading from Boxing cache array, moved 
spit through Phi code from eliminate_autobox() to 
LoadNode::split_through_phi(). Also use incremental inlining to delay 
inlining of valueOf() methods to get value from argument. Mark such 
method as Macro nodes and treat them the same way as Allocations. Added 
value load from constant boxing objects. Eliminated MemBarRelease for 
non-escaping allocations (such membar generated when final fields are 
initialized in constructor).

Did not get any significant performance improvements because very few 
places have opportunity for current optimization (when all objects do 
not escape).

Additional changes:
Added ability to recompile method without EliminateAutoBox if 
compilation with it failed.

Added assert live_nodes < MaxNodeLimit into Node costructor.

Added timer for incremental inlining.

Fixed TypeAryPtr::narrow_size_type() to return correct type for 
arr[MAXINT] (currently it returns incorrect arr[0]).

Moved the check in assert to condition in loopPredicate.cpp because I 
hit the problem during CTW testing.

Fixed tiered compilation process dependence on the order of -Xcomp 
-XX:+TieredCompilation flags.

Added regression tests.

Tested with jprt, ctw, nashorn.

Thanks,
Vladimir