RFR: 8268125: ZGC: Clone oop array gets wrong acopy stub

[Nils Eliasson]

Hi,

This fixes a problem I introduced with JDK-8267726. With that change clone oop array is treated as normal clone arrays with ZGC. I missed that a case was missing in zBarrierSetC2::clone_at_expansion - which caused clone_oop-arrays to get the wrong array copy stub.

In this fix I move the entire leaf call creation inside zBarrierSetC2, and leave BarrierSetC2 as is. In this way I don't have to change anything for the other collectors.

Please review,
Best regards,
Nils Eliasson

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Commit messages:
 - Fix elem check
 - clone_at_expansion

Changes: https://git.openjdk.java.net/jdk/pull/4359/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4359&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8268125
  Stats: 51 lines in 2 files changed: 46 ins; 0 del; 5 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4359.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4359/head:pull/4359

PR: https://git.openjdk.java.net/jdk/pull/4359