RFR: 8214056: Allow the GC to attach context information to CompiledMethod

[Aleksey Shipilev]

On 11/19/18 4:27 PM, Erik Österlund wrote:
> Hi,
> 
> A GC might want extra GC-related information attached to a CompiledMethod.
> I propose to introduce a type-erased _gc_data member, with accessors.
> This allows ZGC to stick in some data we need to keep track of concurrent class unloading.
> 
> Webrev:
> http://cr.openjdk.java.net/~eosterlund/8214056/webrev.00/

This looks generally useful. Patch looks good. Having the type-checked abstraction would be nicer,
of course, but type-erased member would also do.

-Aleksey