RFR: 8291065: Creating a VarHandle for a static field triggers class initialization [v15]

[Chen Liang]

> This patch implements lazy initialization for VarHandle working on static fields. It has a good initial call performance.
> 
> We introduce a new internal API, `target()` to unpack a lazy VarHandle in VH implementation methods. If called via MethodHandle, a barrier is added in the MethodHandle instead.
> 
> The new test ensures the correctness of Lazy VH for both direct and indirect invocation; the performance of MethodHandle version of lazy VH is not yet tested.
> 
> 
> Benchmark                                            Mode  Cnt    Score    Error  Units
> LazyStaticColdStart.methodHandleCreateEager            ss   10   41.490 ± 12.331  us/op
> LazyStaticColdStart.methodHandleCreateLazy             ss   10   21.810 ± 16.964  us/op
> LazyStaticColdStart.methodHandleInitializeCallEager    ss   10   57.860 ± 13.738  us/op
> LazyStaticColdStart.methodHandleInitializeCallLazy     ss   10   93.300 ± 18.858  us/op
> LazyStaticColdStart.varHandleCreateEager               ss   10   39.860 ±  9.362  us/op
> LazyStaticColdStart.varHandleCreateLazy                ss   10   17.630 ±  1.111  us/op
> LazyStaticColdStart.varHandleInitializeCallEager       ss   10  123.170 ± 62.468  us/op
> LazyStaticColdStart.varHandleInitializeCallLazy        ss   10  105.390 ± 41.815  us/op

Chen Liang has updated the pull request incrementally with one additional commit since the last revision:

  Apply suggestions from code review
  
  Co-authored-by: Paul Sandoz <paul.d.sandoz at googlemail.com>

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/13821/files
  - new: https://git.openjdk.org/jdk/pull/13821/files/8cbb2083..469a583f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13821&range=14
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13821&range=13-14

  Stats: 2 lines in 2 files changed: 1 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/13821.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13821/head:pull/13821

PR: https://git.openjdk.org/jdk/pull/13821