Request for reviews (XS): 6746892: Register Allocator does not process a data phi with one unique input correctly

[Vladimir Kozlov]

http://webrev.invokedynamic.info/kvn/6746892/index.html

Fixed 6746892: Register Allocator does not process a data phi with one unique input correctly

Problem:
Register Allocator does not process a data phi with one unique input correctly.
In PhaseChaitin::Split() when it see all block's input edges have the same
live_range it does not look for existing phi for this live_range in the block.
As result the live_range of this phi is not updated and the new live_range
is not propagated to successors.
So the new live range is lost on this path.

Solution:
Always look for the existing phi for a processed live_range.

Reviewed by:
Fix verified (y/n): y, failed CTW test.

Other testing:
JPRT