8387908: [s390x] Port JEP 401 to s390 architecture

[offamitkumar]

S390 port for valhalla, this is just dummy PR for review purposes. Once valhalla code is integrated into mainline, I will open a new PR against jdk/master.

Note

Issue being referred is not for lworld. This is intentional because final PR will be created against jdk/master branch;

---

• I confirm that I make this contribution in accordance with the OpenJDK Interim AI Policy.

---

Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• Change must be properly reviewed (1 review required, with at least 1 Committer)

Issue

• JDK-8387908: [s390x] Port JEP 401 to s390 architecture (Enhancement - P1)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/valhalla.git pull/2632/head:pull/2632
$ git checkout pull/2632

Update a local copy of the PR:
$ git checkout pull/2632
$ git pull https://git.openjdk.org/valhalla.git pull/2632/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 2632

View PR using the GUI difftool:
$ git pr show -t 2632

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/valhalla/pull/2632.diff

[bridgekeeper]

👋 Welcome back amitkumar! A progress list of the required criteria for merging this PR into lworld will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

❗ This change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

[offamitkumar]

Further work is going on here : https://github.com/offamitkumar/valhalla/tree/s390-valhalla-loom ; Right now I am working on enabling the valhalla optimisations.

Changes might be included into this PR or probably a separate PR will be raised, as this is stable already.

[theRealAph]

Fix this.

[offamitkumar]

This is optimisation InlineTypePassFieldsAsArgs which is not yet enabled on s390x, with that this would be cleaned up.

For now idea is to provide a very minimal support for Valhalla, which will prevent the build break and all of tier1 tests, excluding Valhalla-specific ones, should be passing.

[theRealAph]

Then the comment needs to be clear about that. In particular, you need to explain why the poisoned code is unreachable.