[lworld] RFR: 8348972: [lworld] C1/C2: Update Valhalla with UseCompactObjectHeaders for oop->klass load/stores

[Christian Hagedorn]

This patch fixes various issues in C1 and C2 (11 bugs in total) when running with `-XX:+UseCompactObjectHeaders`.

Most of the bugs could either be traced back to:
- Unconditionally assuming old layout with klass pointer following immediately the mark word.
- Small mistakes when merging JEP 450.
- Using the wrong basic type `T_OBJECT` for flat arrays instead of `T_FLAT_ELEMENT`. In Valhalla, we require that the elements of an array are aligned:https://github.com/openjdk/valhalla/blob/04efe5c66b70b9dca1a5c538c9a04e7ad93c107a/src/hotspot/share/oops/arrayOop.hpp#L94-L97
https://github.com/openjdk/valhalla/blob/04efe5c66b70b9dca1a5c538c9a04e7ad93c107a/src/hotspot/share/oops/arrayOop.hpp#L57-L61
When we now wrongly use `T_OBJECT`, it is not a problem with default flags (using compressed klass pointers and no COH): An array has a 12 byte header + 4 byte length which is 16 bytes in total - no alignment required. But with COH, we now have a header of 8 bytes + 4 byte length. We now require alignment but when we pass in `T_OBJECT`, we miss the alignment which leads to crashes down the line. I went through all the uses of `base_offset_in_bytes()` and fixed more such issues.

To review: I made separate commits for each fixed bug, each message summarizing the found issue. To better understand individual changes of the patch, it might help to look at the commits separately.

**Testing:**
- Apart from one bug, I could trigger them with existing tests. So, I have not added new tests for these issues separately.
- One bug only manifested with a new test (`test127a`) which I added with this patch.
- tier1-5 + compiler stress:
  - No additional flags, i.e. (mostly) without COH: Looks good and only known failures
  - With explicitly setting COH:
    - A lot of CDS related failures on which @matias9927 is working ([JDK-8367959](https://bugs.openjdk.org/browse/JDK-8367959))
    - Test timeout with `TestIntrinsics`: Unrelated to COH but only triggering with COH ([JDK-8368274](https://bugs.openjdk.org/browse/JDK-8368274)).
    - Otherwise, looks good with only known failures.

Thanks,
Christian

-------------

Commit messages:
 - Unproblemlist tests
 - C2: store_inline_type_fields_to_buf() wrongly loads InlineKlassFixedBlock from wrong register on aarch with COH
 - C2: Fix wrong prototype klass word in expand_mh_intrinsic_return with COH
 - C2: Fix wrong header computation in ArrayCopyNode::modifies with COH
 - C2: Fix wrong header computation for System.arraycopy() with COH
 - C2: Fix wrong header computation in ArrayCopyNode::prepare_array_copy() for copyOf() with COH
 - C2: Fix header computation in array_element_address() with COH
 - C2: Wrong header size computation when attaching value object fields to safepoint with COH
 - C2: First element of array was wrongly fetched with T_OBJECT instead of T_FLAT_ELEMENT which ignored forced alignment checked with element_type_should_be_aligned()
 - C2: store_inline_type_fields_to_buf() wrongly loads InlineKlassFixedBlock from markword instead of klass pointer with COH
 - ... and 2 more: https://git.openjdk.org/valhalla/compare/01225ee2...dc06e1e9

Changes: https://git.openjdk.org/valhalla/pull/1632/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1632&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8348972
  Stats: 157 lines in 12 files changed: 93 ins; 37 del; 27 mod
  Patch: https://git.openjdk.org/valhalla/pull/1632.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1632/head:pull/1632

PR: https://git.openjdk.org/valhalla/pull/1632