RFR(S): 8217043: Shenandoah: SIGSEGV in Type::meet_helper() at barrier expansion time

[Roland Westrelin]

http://cr.openjdk.java.net/~roland/8217043/webrev.00/

The ShenandoahBarrierNode::needs_barrier_impl() encounters a
CallLeafNode (from a write barrier) and tries to get the type of n which
is a tuple, not a pointer and this causes a null pointer
dereference. The write barrier runtime call should anyway prevent an
optimization of the barrier and to be on the safe side, any call should.

Roland.