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

[Tobias Hartmann]

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*
JPRT

Thanks,
Tobias

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