[master] RFR: 8319185: [Lilliput] Enable and fix vectorization tests [v2]

[Roman Kennke]

> The change does two (related) things:
> 
> It white-lists the UseCompactObjectHeaders flag in the IR testing framework. Without this, the flag would not be passed through to any IR framework test.
> That first change makes 3 tests fail. Those are all vectorization tests, and they are failing because 'small' array types (4-byte-elements and smaller) no longer have their elements aligned at 8-byte-boundaries. This throws off vectorization because this only kicks in on aligned accesses. The mitigation is to disable the failing tests for now. #118 offered a more comprehensive solution, but it was also more intrusive. After some discussion with Emmanuel Peter and Maurizio Cimadamore, we came to the conclusion that disabling the tests for now might be a better approach, especially considering that we may soon no longer need special 4-byte-array-alignment anymore.
> 
> 
> Testing:
>  - [x] compiler/c2/irTests/TestVectorizationMismatchedAccess.java +UCOH
>  - [x] compiler/c2/irTests/TestVectorizationNotRun.java +UCOH
>  - [x] compiler/loopopts/superword/TestIndependentPacksWithCyclicDependency.java +UCOH
>  - [x] compiler/c2/irTests/TestVectorizationMismatchedAccess.java -UCOH
>  - [x] compiler/c2/irTests/TestVectorizationNotRun.java -UCOH
>  - [x] compiler/loopopts/superword/TestIndependentPacksWithCyclicDependency.java -UCOH
>  - [x] tier1 +UCOH
>  - [x] tier1 -UCOH

Roman Kennke has updated the pull request incrementally with one additional commit since the last revision:

  Formatting improvement

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

Changes:
  - all: https://git.openjdk.org/lilliput/pull/125/files
  - new: https://git.openjdk.org/lilliput/pull/125/files/08460a63..341cef3e

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=lilliput&pr=125&range=01
 - incr: https://webrevs.openjdk.org/?repo=lilliput&pr=125&range=00-01

  Stats: 14 lines in 2 files changed: 7 ins; 0 del; 7 mod
  Patch: https://git.openjdk.org/lilliput/pull/125.diff
  Fetch: git fetch https://git.openjdk.org/lilliput.git pull/125/head:pull/125

PR: https://git.openjdk.org/lilliput/pull/125