RFR(XS) 8071302: assert(!_reg_node[reg_lo] || edge_from_to(_reg_node[reg_lo], def)) failed: after block local scheduling

[Igor Veresov]

This is caused by JDK-8068881. MachMerge node is scheduled incorrectly because it is not mapped to an appropriate block.

Webrev: http://cr.openjdk.java.net/~iveresov/8071302/webrev.00/

Thanks,
igor