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

[Doug Simon]

> On 15 Apr 2018, at 12:03, Andrew Haley <aph at redhat.com> wrote:
> 
> On 04/14/2018 01:29 PM, Doug Simon wrote:
>>> In the meantime, be aware that Graal development on JDK11 is broken
>>> until this change is pushed to Graal.  As far as I know, Graal changes
>>> are supposed to be reviewed by Graal developers.
>> Changes like this one can be reviewed by anyone in the HotSpot
>> compiler team or Graal team.
> 
> That's good to know.  The change is obviously correct, but it needs to
> be handled correctly.

Right. The GitHub Graal code base needs to work from JDK 8 (with a JVMCI patch) onwards. We have just recently switched to using multi-release jars to make this process saner and avoid the use of reflection to access version dependent API. When GitHub Graal snapshots are taken for syncing the code into OpenJDK, the versioned directories are flattened to the non-versioned root directory following the same logic that would be applied when resolving a versioned class at runtime. The flattenmultireleasesources command[1] was added to mx to facilitate this flattening.

The particular change in this webrev is a good opportunity to make GraalHotSpotVMConfig versioned in this way. I'll make the necessary changes for this in GitHub Graal. Normally, no manual change should be made to OpenJDK Graal but in this case I think it's necessary so that OpenJDK testing of Graal won't break.

> For my information, though, I presume "changes like this" means simple
> changes to JVMCI.  That right?

Sorry for my ambiguity. I meant that this is a simple change to both JVMCI and Graal and by now most HotSpot compiler developers should be able to review it. Of course, having a Graal developer look at it as well is recommended. The preferred way to do this is to open a PR at https://github.com/graalvm/mx/pulls.

-Doug

[1] https://github.com/graalvm/mx/commit/bad56c1101db758c3f8c6560fc62012c15be39e4

> -- 
> Andrew Haley
> Java Platform Lead Engineer
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