[9] RFR(S): 8036851: volatile double accesses are not explicitly atomic in C2

Tobias Hartmann Tobias.Hartmann at oracle.com
Fri May 2 15:09:21 UTC 2014

Hi Aleksey,

thanks for your feedback.

On 05/02/2014 03:53 PM, Aleksey Shipilev wrote:
> Glad to see this addressed. The patch looks fine to me (not a Reviewer).
> I remember seeing places in C1 where we special-case T_LONG, so we
> probably need an additional work to fix it there as well. See e.g.
> LIRGenerator::volatile_field_store.

But the implementation of LIRGenerator::volatile_field_store is 
architecture specific so it should be fine to special-case T_LONG on x86 
because all other accesses are guaranteed to be atomic. Or am I missing 
something here?


> -Aleksey
> On 05/02/2014 04:15 PM, Tobias Hartmann wrote:
>> Hi,
>> please review the following patch for bug 8036851.
>> *Problem*
>> Volatile double accesses are not treated different from normal accesses
>> in the C2 compiler with respect to atomicity because on x86 and sparc
>> double accesses were always atomic. However, this may not be case on
>> other architectures. On an architecture where there are atomic and
>> non-atomic double accesses, we would have to implement all accesses to
>> be atomic, because the C2 compiler does not distinguish between the two
>> cases.
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8036851
>> *Solution*
>> The C2 structure is adapted to distinguish between volatile and
>> non-volatile double accesses.
>> Webrev: http://cr.openjdk.java.net/~anoll/8036851/webrev.00/
>> <http://cr.openjdk.java.net/%7Eanoll/8036851/webrev.00/>
>> *Tests*
>> Thanks,
>> Tobias

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