RFR (S) 8175887: C1 value numbering handling of Unsafe.get*Volatile is incorrect

[Aleksey Shipilev]

On 02/27/2017 03:12 PM, Aleksey Shipilev wrote:
> On 02/27/2017 10:53 AM, Aleksey Shipilev wrote:
>> C1 does not have intrinsics for Opaque, and therefore it should delegate Opaque
>> ops to volatile via fallbacks in Unsafe.java. But now I read the C1
>> Unsafe.getObject handling, and my hair stand on end, because I think C1 {L,G}VN
>> does not treat volatile Unsafe ops any specially, while it probably should:
>>  https://bugs.openjdk.java.net/browse/JDK-8175887
>>
>> Makes sense?
> 
> This is the actual reproducible bug, changing the thread subject.
> 
> Fix against jdk9/hs:
>   http://cr.openjdk.java.net/~shade/8175887/webrev.01/

Updated after off-list review (renamed tests, used internal Unsafe):
  http://cr.openjdk.java.net/~shade/8175887/webrev.02/

Everything else still stands:

> Testing: Linux x86_64/release hotspot/test/compiler, includes new tests
> 
> I need a sponsor. I think this bugfix is too important to miss 9, and it even
> deserves backporting to 8u.

-Aleksey

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