RFR: 8160821: VarHandle accesses are penalized when argument conversion is required [v7]

[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 incrementally with one additional commit since the last revision:

  Revert void special case removal due to C2 shortage causing TestZGCBarrierElision::testAtomicThenAtomicAnotherField failure

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Changes:
  - all: https://git.openjdk.org/jdk/pull/28585/files
  - new: https://git.openjdk.org/jdk/pull/28585/files/ff7b3629..8200fb28

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28585&range=06
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28585&range=05-06

  Stats: 23 lines in 1 file changed: 20 ins; 0 del; 3 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