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

Aleksey Shipilev shade at redhat.com
Mon Feb 27 14:12:17 UTC 2017

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:

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.


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