8386586: [s390x] TestSyncOnValueBasedClassEvent.java fails due to incorrect branch

[offamitkumar]

Depends on:

• 8286300: Port JEP 425 to S390X #31441

This test case was mistakenly marked as "related to loom" and disabled on s390x.

Explanation:

What we WANT: Jump to slow path when the value-based class bit IS SET (bit = 1)

What TM instruction does when testing a single bit:

• Bit is 0 → CC=0 (all tested bits are zero)
• Bit is 1 → CC=3 (all tested bits are one)

Branch conditions:

• z_brne uses mask bcondNotEqual = 6 = binary 0110 = branches on CC=1 or CC=2
• z_brnaz uses mask bcondNotAllZero = 7 = binary 0111 = branches on CC=1, CC=2, or CC=3

The problem:
When the bit IS SET (value-based class detected):

• TM sets CC=3
• z_brne (mask 6) does NOT include CC=3, so it does NOT branch → BUG!

Failure:
java.lang.RuntimeException: No events: expected false, was true
at jdk.test.lib.Asserts.fail(Asserts.java:715)
at jdk.test.lib.Asserts.assertFalse(Asserts.java:520)
at jdk.test.lib.jfr.Events.hasEvents(Events.java:160)
at jdk.jfr.event.runtime.TestSyncOnValueBasedClassEvent.main(TestSyncOnValueBasedClassEvent.java:79)
at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
at java.base/java.lang.reflect.Method.invoke(Method.java:583)
at com.sun.javatest.regtest.agent.MainWrapper$MainTask.run(MainWrapper.java:138)
at java.base/java.lang.Thread.run(Thread.java:1527)

with the change:

Finished running test 'jtreg:test/jdk/jdk/jfr/event/runtime/TestSyncOnValueBasedClassEvent.java'
Test report is stored in build/linux-s390x-server-fastdebug/test-results/jtreg_test_jdk_jdk_jfr_event_runtime_TestSyncOnValueBasedClassEvent_java

==============================
Test summary
==============================
   TEST                                              TOTAL  PASS  FAIL ERROR  SKIP   
   jtreg:test/jdk/jdk/jfr/event/runtime/TestSyncOnValueBasedClassEvent.java
                                                         1     1     0     0     0   
==============================
TEST SUCCESS

Finished building target 'test' in configuration 'linux-s390x-server-fastdebug'

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Issue

• JDK-8386586: [s390x] TestSyncOnValueBasedClassEvent.java fails due to incorrect branch (Bug - P4)

Reviewing

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Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/31497/head:pull/31497
$ git checkout pull/31497

Update a local copy of the PR:
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$ git pull https://git.openjdk.org/jdk.git pull/31497/head

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$ git pr checkout 31497

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https://git.openjdk.org/jdk/pull/31497.diff

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