RFR: 8208171: PPC64: Enrich SLP support

[Michihiro Horie]

Dear all,

Would you review the following change?
Bug: https://bugs.openjdk.java.net/browse/JDK-8208171
Webrev: http://cr.openjdk.java.net/~mhorie/8208171/webrev.00

This change adds support for vectorized arithmetic calculation with SLP.

The to_vr function is added to convert VSR to VR. Currently, vecX is
associated with a VSR class vs_reg that only defines VSR32-51 in ppc.ad,
which are exactly overlapped with VRs. Instruction APIs receiving VRs use
the to_vr via vecX. Another thing is the change in sqrtF_reg to enable the
matching with SqrtVF. I think the change in sqrtF_reg would be fine due to
the ConvD2FNode::Value in convertnode.cpp.

I confirmed this change with JTREG. In addition, I used attached micro
benchmarks.
(See attached file: slp_microbench.zip)


Best regards,
--
Michihiro,
IBM Research - Tokyo