RFR: 8327380: Add tests for Shenandoah barrier expansion optimization

Tue May 21 14:32:35 UTC 2024

The Ideal graph for Shenandoah barrier expansion is optimized so that unnecessary checks are eliminated; however, currently there is no test cases to determine these optimizations are in effect.

Adding unit tests with the IR test framework will support related code changes in the future.

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Commit messages:
 - update asserted IR phase
 - change assertion phase from MACRO_EXPANSION to AFTER_MACRO_EXPANSION_STEP
 - add license header
 - update test annotation
 - Merge branch 'master' into test-shenandoah-barrier-expansion
 - update vm flags
 - update vm flags
 - add TestShenandoahBarrierExpansion

Changes: https://git.openjdk.org/jdk/pull/18814/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18814&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8327380
  Stats: 89 lines in 1 file changed: 89 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/18814.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18814/head:pull/18814

PR: https://git.openjdk.org/jdk/pull/18814