RFR: 8306842: Classfile API performance improvements [v4]

[Adam Sotona]

> Following improvements implemented:
> - Switch over `String` replaced with switch single char
> - Binary search for frames in `StackMapGenerator`
> - `StackMapGenerator.rawHandlers` with pre-calculated offsets
> - `ClassEntry` is caching `ClassDesc` symbol
> - Caching of type symbols in `NameAndTypeEntry` and `MethodTypeEntry`
> - Caching `MethodTypeDesc` in `MethodInfo` implementations
> - `StackMapGenerator` and `Utils` delegating to cached `MethodTypeDesc` instead of custom parsing
> 
> No API change.
> 
> Benchmarks show stack map generation improved by 21% and code generation from symbols improved by 30%.
> 
> 
> Benchmark                     Mode  Cnt       Score       Error  Units
> GenerateStackMaps.benchmark  thrpt   10  407931.202 ± 13101.023  ops/s
> RebuildMethodBodies.shared   thrpt    4   10258.597 ±   383.699  ops/s
> RebuildMethodBodies.unshared thrpt    4    7224.543 ±   256.800  ops/s
> 
> 
> 
> Benchmark                     Mode  Cnt       Score      Error  Units
> GenerateStackMaps.benchmark  thrpt   10  495101.110 ± 2389.628  ops/s
> RebuildMethodBodies.shared    thrpt   4   13380.272 ±  810.113  ops/s
> RebuildMethodBodies.unshared  thrpt   4    9399.863 ±  557.060  ops/s

Adam Sotona has updated the pull request incrementally with one additional commit since the last revision:

  fixed jmh benchmark parameters

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/13671/files
  - new: https://git.openjdk.org/jdk/pull/13671/files/5af9f9c4..3cbb11c2

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13671&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13671&range=02-03

  Stats: 46 lines in 5 files changed: 32 ins; 9 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/13671.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13671/head:pull/13671

PR: https://git.openjdk.org/jdk/pull/13671