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

[Aleksey Shipilev]

On 02/27/2017 04:21 PM, Stuart Monteith wrote:
> Actually, rerunning without any jvmargs (which reduced the coverage when
> testing your patch), I get:
> 
> 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, -XX:-TieredCompilation, -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
> 
> So what I said before was wrong, I do get the failures.
> Running with -XX:TieredStopAtLevel=1, I don't get failures.

Good. This is what I wanted to know for this patch.

> Given that -server == -client, all of the failing tests are either
> against C2 or tiered C1 & C2 compilation.
> 
> Running with the options passed explicity, "-m tough", the tests pass with:
> 	-XX:TieredStopAtLevel=1   (Patched & unpatched)
> 
> Fails with:
> 	-XX:-TieredCompilation              "
> 
> No failures with:
> 	-XX:-TieredComplation -Xcomp
> 
> My other two machines doen't exhibit the failure.

Ok, let's discuss that one separately. These failures seem unrelated to this
issue with C1, and most probably indicate some other peculiar issue.

Thanks,
-Aleksey

Thanks,
-Aleksey

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