[vector] RFR: Enable call devirtualization during post-parse phase

[Vladimir Ivanov]

http://cr.openjdk.java.net/~vlivanov/panama/vector/late_inline_virtual/webrev.00/

Vector API refactoring broke inlining through virtual calls in some 
important scenarios (for example, both dot product and matrix 
multiplication samples [1] are affected [1]).

The primary root cause is the delay in intrinsification of vector 
operations: unless enough type info is available for receiver during 
parsing, the call won't be devirtualized (and hence inlined), but 
intrinsification happens during post-parse phase.

However, it turned out that the problem is broader and not specific to 
Vector API. It's not enough just to intrinsify vector operations eagerly.

Proposed patch is an experimental implementation of post-parse 
devirtualization (virtual-to-direct call transformation) which then 
enables post-parse inlining & intrinsification through such calls.

I'll work on upstreaming the optimization separately since it benefits 
ordinary Java code as well. Meanwhile, I propose to integrate the 
interim version into vectorIntrinsics branch right away to avoid 
surprises during performance analysis.

Best regards,
Vladimir Ivanov

[1] 
https://github.com/richardstartin/vectorbenchmarks/blob/master/src/main/java/com/openkappa/panama/vectorbenchmarks/