RFR: 8339694: ciTypeFlow does not correctly handle unresolved constant dynamic of array type

[Tobias Hartmann]

After [JDK-8280473](https://bugs.openjdk.org/browse/JDK-8280473), the CI will represent an unresolved constant dynamic as unloaded `ciConstant` of a `java/lang/Object` `ciInstanceKlass`:

https://github.com/openjdk/jdk/blob/6133866150cf6131ab578f1537f84c239703fa67/src/hotspot/share/ci/ciEnv.cpp#L721-L723

Now with a constant dynamic of array type, we hit an assert in type flow analysis on `*astore` because the type is not a primitive array type:

https://github.com/openjdk/jdk/blob/6133866150cf6131ab578f1537f84c239703fa67/src/hotspot/share/ci/ciTypeFlow.cpp#L967-L971

->
https://github.com/openjdk/jdk/blob/6133866150cf6131ab578f1537f84c239703fa67/src/hotspot/share/ci/ciTypeFlow.hpp#L343-L346

The same problem exists with object array types. New `TestUnresolvedConstantDynamic` triggers both.

Similar to `unloaded_ciinstance` used by [JDK-8280473](https://bugs.openjdk.org/browse/JDK-8280473) (see [here](https://github.com/openjdk/jdk/commit/88fc3bfdff7f89a02fcfb16909df144e6173c658#diff-7c032de54e85754d39e080fd24d49b7469543b163f54229eb0631c6b1bf26450R784)), we could now add an unloaded `ciObjArray` and `ciTypeArray` to represent an unresolved dynamic constant of array type. We would then add a trap when parsing the array access. However, this requires rather invasive changes for this edge case and it wouldn't make much sense because even though type flow analysis would continue, we would add a trap when parsing `_ldc` anyway if the constant is not loaded: 
https://github.com/openjdk/jdk/blob/037f11b864734734dd7fbce029b2e8b4bc17f3ab/src/hotspot/share/opto/parse2.cpp#L1962-L1979

I propose to do the same in type flow analysis, i.e., trap early in `_ldc` when the constant is not loaded.

Thanks,
Tobias

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Commit messages:
 - First prototype

Changes: https://git.openjdk.org/jdk/pull/21470/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21470&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8339694
  Stats: 111 lines in 4 files changed: 108 ins; 2 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/21470.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21470/head:pull/21470

PR: https://git.openjdk.org/jdk/pull/21470