[lworld] Integrated: JDK-8293321: [lworld] substitutability test shall support value class with cyclic membership

[Mandy Chung]

On Fri, 28 Oct 2022 17:15:19 GMT, Mandy Chung <mchung at openjdk.org> wrote:

> L-type allows cycles. `acmp` shall support value classes with cyclic membership.  This PR adds the support in the Java implementation of `acmp` (i.e. `ValueObjectMethods::isSubstitutable`). 
> 
> This patch includes [John's first cut to make a Y combinator method handle](https://github.com/openjdk/jdk/pull/10155) to enable a method handle to call itself recursively.    PR 10155 is adequate for internal use for now.  A separate RFE will follow to define such an API.
> 
> A separate issue [JDK-8296056](https://bugs.openjdk.org/browse/JDK-8296056) tracks the C2 `acmp` support.

This pull request has now been integrated.

Changeset: 0ff3973c
Author:    Mandy Chung <mchung at openjdk.org>
URL:       https://git.openjdk.org/valhalla/commit/0ff3973c6105ae8f7b3709caa452ceed8df8f885
Stats:     769 lines in 3 files changed: 743 ins; 4 del; 22 mod

8293321: [lworld] substitutability test shall support value class with cyclic membership

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PR: https://git.openjdk.org/valhalla/pull/802