[8u] RFR for backport of JDK-8164920: ppc: enhancement of CRC32 intrinsic to jdk8u-dev (v2)

[Gustavo Romero]

Hi,

Maybe I please get reviews for the following changes (v2)?

http://cr.openjdk.java.net/~gromero/crc32_jdk8u/v2/8131048/
http://cr.openjdk.java.net/~gromero/crc32_jdk8u/v2/8164920/

Change JDK-8131048 is a dependency to backport JDK-8164920 to 8u.

Goetz reviewed the first version of this backport and pointed out necessary
changes and fixes that are present in this v2. Thank you, Goetz.

There is no code change except to adapt the file paths, to add has_vpmsumb()
feature detection, and to adapt the signature before doing the runtime call
to CRC32 intrinsic by casting T_INTs as T_LONGs, because PPC64
c_calling_convention() requires T_LONGs on 8u, otherwise a proper assert()
for that is hit.

Change JDK-8131048 touches shared code but, since it checks for
'CCallingConventionRequiresIntsAsLongs' flag that is only currently set on
PPC64, that change is in effect PPC64-only.

JDK-8164920 is important for PPC64 because it helps a lot some Apache
Cassandra workloads on Power.

Thank you.


Best regards,
Gustavo