8373698: [Lilliput] Fix oop-checking with ZGC/CDS and compact headers

[rkennke]

UnsafeIntrinsicsTest.java (and some others) are failing with +COH and ZGC. The reason is:

1. archive_object_size() (aotStreamedHeapLoader.cpp:159) operates on oopDesc* pointers to archived objects in CDS shared memory (not the GC
   heap)
2. The COH code at lines 169 and 182 calls klass->expand_for_hash(archive_object, ...) which takes an oop parameter
3. The implicit oopDesc* → oop conversion calls on_construction() which validates the address via ZGC's check_is_valid_zaddress()
4. ZGC requires addresses to have the heap base bit set (zAddress.inline.hpp:450) and be within heap range (:456), but CDS objects are
   outside ZGC's virtual address space

The fix is to temporarily disable oop-checking around the affected code, because those are not real oops in the Java heap.

The alternative would have been to change all the i-hash-functions to accept oopDesc* instead of oop, but that would disable the oop-check wholesale, even for valid heap objects, which is not what we want.

Testing:

• UnsafeIntrinsicsTest.java
• tier1 +UCOH
• tier1 -UCOH

---

Progress

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Issue

• JDK-8373698: [Lilliput] Fix oop-checking with ZGC/CDS and compact headers (Bug - P4)

Reviewers

• Oli Gillespie (@olivergillespie - Author)

Reviewing

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[mlbridge]

Webrevs

• 01: Full - Incremental (04f9cac3)
• 00: Full (011d86c4)

[olivergillespie]

I don't know the threading model here - are you happy that this will not be used concurrently?

[rkennke]

archive-loading is single-threaded, so we should be ok, I think.