RFR: 8160821: VarHandle accesses are penalized when argument conversion is required [v8]

[Chen Liang]

> Since access descriptor is created for each VH operation site, we can optimistically cache the adapted method handle in a site if the site operates on a constant VH.  Used a C2 IR test to verify such a setup through an inexact VarHandle invocation can be constant folded through (previously, it was blocked by `asType`)

Chen Liang has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 15 additional commits since the last revision:

 - Bugs and verify loader leak
 - Try to avoid loader leak
 - Merge branch 'master' of https://github.com/openjdk/jdk into fix/vh-adapt-cache
 - Revert void special case removal due to C2 shortage causing TestZGCBarrierElision::testAtomicThenAtomicAnotherField failure
 - Test from Jorn
 - Copyright years
 - Fix problem identified by Jorn
 - Rollback getAndAdd for now
 - Redundant change
 - Merge branch 'master' of https://github.com/openjdk/jdk into fix/vh-adapt-cache
 - ... and 5 more: https://git.openjdk.org/jdk/compare/295928d3...eebb8ff7

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Changes:
  - all: https://git.openjdk.org/jdk/pull/28585/files
  - new: https://git.openjdk.org/jdk/pull/28585/files/8200fb28..eebb8ff7

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28585&range=07
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28585&range=06-07

  Stats: 10547 lines in 389 files changed: 7296 ins; 2024 del; 1227 mod
  Patch: https://git.openjdk.org/jdk/pull/28585.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28585/head:pull/28585

PR: https://git.openjdk.org/jdk/pull/28585