Summary: T_ADDRESS size is defined as 'int' size (4 bytes) but C2 use it for raw pointers and as memory type for StoreP and LoadP nodes.
Reviewed-by: jrose

Summary: Use the same default number of GC threads as used by ParNewGC and ConcMarkSweepGC (i.e., the 5/8th rule).
Reviewed-by: ysr, tonyp

Reviewed-by: jcoomes