RFR: 8081669: aarch64: JTreg TestStable tests failing

[Vladimir Ivanov]

The only concern I have is that I don't see Alexander on OCA list [1].
In order to proceed with the fix, he should sign OCA first.

Best regards,
Vladimir Ivanov

[1] http://www.oracle.com/technetwork/community/oca-486395.html

On 6/2/15 5:17 PM, Vladimir Ivanov wrote:
> Looks good.
>
> Best regards,
> Vladimir Ivanov
>
> On 6/2/15 12:26 PM, Edward Nevill wrote:
>> Hi,
>>
>> The following webrev
>>
>> http://cr.openjdk.java.net/~enevill/8081669/webrev.00/
>>
>> fixes a number of TestStable tests.
>>
>> This patch was contributed by alexander.alexeev at caviumnetworks.com
>>
>> The following are the test failures that are fixed by this patch
>>
>> compiler/stable/TestStableByte.java
>> compiler/stable/TestStableBoolean.java
>> compiler/stable/TestStableChar.java
>> compiler/stable/TestStableFloat.java
>> compiler/stable/TestStableObject.java
>> compiler/stable/TestStableDouble.java
>> compiler/stable/TestStableInt.java
>> compiler/stable/TestStableLong.java
>> compiler/stable/TestStableShort.java
>>
>> The problem is that the method 'get' in StableConfiguration is
>> supposed to return true if the method is server compiled, false
>> otherwise.
>>
>> On aarch64 it is always returning true, even when the method is client
>> compiled. The reason for this is that aarch64 differs from other ports
>> in that it always deopts on patching.
>>
>> This means that the method 'get' deopts immediately when compiled with
>> -Xcomp because it hits an unresolved method call. This means that the
>> method is now executing in the interpreter.
>>
>> When the method 'get' is executing in the interpreter, it uses the
>> value of java.vm.name to determine whether the method would be server
>> compiled if it were to be compiled. This ends up returning true on
>> aarch64, because it is a server compiler.
>>
>> However in the case where we force it not to server compile by using
>> -XX:+TieredCompilation and -XX:TieredStopAtLevel=1 (as in the
>> TestStable tests) this will be incorrect.
>>
>> The solution is to introduce a simple (null) method 'get1' which will
>> never be deopted (because there is never anything to patch) and uses
>> this as the basis for deciding whether we are server compiling or not.
>>
>> This is more fully explained in the inline comment in the patch.
>>
>> Please review and if appropriate I will push.
>>
>> All the best,
>> Ed.
>>
>>