8187809: UseMembar should be set true and deprecate the flag Reviewed-by: dcubed, sspitsyn, dholmes

8186125: "DU iteration must converge quickly" assert in split if with unsafe accesses Summary: added missing checks for Opaque4Node in split-if code Reviewed-by: kvn

8183542: Factor out serial GC specific code from GenCollectedHeap into its own subclass Reviewed-by: kbarrett, jgeorge

8185925: StackFrameInfo::walker field can be replaced with bitmap to save footprint 8153682: StackFrameInfo.declaringClass could be removed Reviewed-by: coleenp, mchung