RFR: 8201318: Introduce GCThreadLocalData to abstract GC-specific data belonging to a thread

[Aleksey Shipilev]

On 04/10/2018 05:25 PM, Robbin Ehn wrote:
> Had quick look, what I saw looked good. (not a full review)
> Is there a reason for moving the gc data to 'zero offset' in Thread?

Oh! I missed that, and I fully agree with this move. At least one reason I see, smaller offsets
against TLS open up opportunities for denser code-generation when e.g. GC barriers poll thread-local
data. Right now SATB barrier generates something like "cmpb $0x0, 0x3d8(%r15)", while it could
generate just "cmpb $0x0, 0x0(%r15)" now :)

Thanks,
-Aleksey