RFC 8175887: C1 value numbering handling of Unsafe.get*Volatile is incorrect?

[Aleksey Shipilev]

On 02/27/2017 03:35 PM, Aleksey Shipilev wrote:
> On 02/27/2017 03:32 PM, Stuart Monteith wrote:
>> Will throw any pending exceptions at this point.
>> Exception in thread "main" java.lang.AssertionError: TEST FAILURES:
>>
>> org.openjdk.jcstress.tests.coherence.varHandles.fields.opaque.ShortTest
>> [-client, -XX:-TieredCompilation]: Observed forbidden state: -1, 0
>>
>> org.openjdk.jcstress.tests.coherence.varHandles.fields.opaque.ShortTest
>> [-server, -XX:+UnlockDiagnosticVMOptions, -XX:+StressLCM,
>> -XX:+StressGCM]: Observed forbidden state: -1, 0
>>
>> org.openjdk.jcstress.tests.coherence.varHandles.fields.opaque.ShortTest
>> [-server]: Observed forbidden state: -1, 0
>>
>> org.openjdk.jcstress.tests.coherence.varHandles.fields.opaque.ShortTest
>> [-server, -XX:-TieredCompilation]: Observed forbidden state: -1, 0
>>
>> org.openjdk.jcstress.tests.coherence.varHandles.fields.opaque.ShortTest
>> [-client]: Observed forbidden state: -1, 0
>>
>> org.openjdk.jcstress.tests.coherence.varHandles.fields.opaque.ShortTest
>> [-server, -XX:-TieredCompilation, -XX:+UnlockDiagnosticVMOptions,
>> -XX:+StressLCM, -XX:+StressGCM]: Observed forbidden state: -1, 0
>>
>> Applying your patch and rerunning this test on the aarch64 machine
>> causes these tests to pass. Now doing a full run. It should be finished
>> by Tuesday.
> 
> So Opaque failures on your machines *are* related to this. Good to know, thanks!

It does not sound right though: with -TieredCompilation only C2 should have been
working, not C1. Must be something else.

-Aleksey

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