Request for reviews (XS): 6992789: assert(phi->_idx >= nodes_size()) failed: only new Phi per instance memory slice

[Vladimir Kozlov]

http://cr.openjdk.java.net/~kvn/6992789/webrev

Fixed 6992789: assert(phi->_idx >= nodes_size()) failed: only new Phi per 
instance memory slice

After instance's memory slices are split we update original phi inputs to skip 
stores to instance (Phase 4). We should keep original input if it was not memory 
node. In the bug case the input is an other Phi with different alias index and 
instead of keeping it the code tries to create new phi with original index. It 
happened because the check that it is not instance memory slice was done after 
compare indexes.

Swap checks: check for regular memory slice first and keep input phi.