RFR: 8284115: [IR Framework] Compilation is not found due to rare safepoint while dumping PrintIdeal/PrintOptoAssembly

[Christian Hagedorn]

This is yet another manifestation of the safepointing problem while printing a `PrintIdeal/PrintOptoAssembly` block.

In this case here, a safepoint is done and the `` message is emitted while dumping a `PrintIdeal` block of `retainDenominator()` inside the `hotspot_pid` file. During this interruption, another test class method is enqueued for compilation which is logged to the `hotspot_pid` file before the printing of the `PrintIdeal` block resumes:


# PrintIdeal output of retainDenominator()
 3 Start === 3 0 [[ 3 5 6 7 8 9 13 11 ]] #{0:control, 1:abIO, 2:memory, 3:rawptr:BotPTR, 4:return_address, 5:compiler/c2/irTests/DivLNodeIdealizationTests:NotNull *, 6:long, 7:half, 8:long, 9:half}
 36 CallStaticJava === 34 6 7 8 9 ( 35 1 1 1 1 1 26 1 27 1 ) [[ 37 ]] # Static uncommon_trap(reason='div0_check' action='maybe_recompile' debug_id='0') void ( int ) C=0.000100 DivLNodeIdealizationTests::retainDenominator @ bci:4 (line 130) !jvms: DivLNodeIdealizationTests::retainDenominator

# Safepoint interruption
<writer thread='40451'/>

# Enqueuing of another test class method identityThird()
<task_queued compile_id='205' method='compiler.c2.irTests.DivLNodeIdealizationTests identityThird (JJ)J' bytes='6' count='6000' iicount='6000' blocking='1' stamp='1.046' comment='whitebox' hot_count='6000'/>
<writer thread='23811'/>
 @ bci:4 (line 130)

# Continue to dump PrintIdeal of retainDenominator()
 41 DivL === 33 26 13 [[ 42 ]] !jvms: DivLNodeIdealizationTests::retainDenominator @ bci:4 (line 130)
 9 Parm === 3 [[ 42 36 ]] ReturnAdr !jvms: DivLNodeIdealizationTests::retainDenominator @ bci:-1 (line 130)


The `HotSpotPidFileParser` looks for these enqueue messages containing the method name in order to find and correctly map the corresponding `PrintIdeal` and `PrintOptoAssembly` outputs. However, the `HotSpotPidFileParser` does not expect such an enqueuing message to be found inside a `PrintIdeal/PrintOptoAssembly` block and thus ignores it. As a result, we later do not parse the `PrintIdeal` and `PrintOptoAssembly` output of the enqueued method during the safepoint and fail with the assertion that we did not find any compilation output for the method.

In the example above, the assertion says that we did not find the compilation output of `identityThird()` whose enqueue message was ignored inside the `PrintIdeal` block of `retainDominator()`.

The proposed fix is to make `HotSpotPidFileParser` aware of the possibility of a safepoint while reading the `PrintIdeal` or `PrintOptoAssembly` output and therefore add a check if there was a method enqueued for compilation while reading inside `BlockOutputReader::readBlock()`.

Thanks,
Christian

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Commit messages:
 - 8284115: [IR Framework] Compilation is not found due to rare safepoint while dumping PrintIdeal/PrintOptoAssembly

Changes: https://git.openjdk.java.net/jdk/pull/8692/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8692&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8284115
  Stats: 160 lines in 6 files changed: 109 ins; 40 del; 11 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8692.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8692/head:pull/8692

PR: https://git.openjdk.java.net/jdk/pull/8692