RFR(S): 8237776: Shenandoah: Wrong result with Lucene test

[Roland Westrelin]

http://cr.openjdk.java.net/~roland/8237776/webrev.00/

xmm0 (an argument to a call) gets corrupted in the c2i adapter (when
going from c1 code to the interpreter) at the
ShenandoahRuntime::write_ref_field_pre_entry() runtime call. That call
is in the c2i because of c2i_entry_barrier() and
resolve_weak_handle(). The proposed fix saves all floating point
argument registers.

Roland.