RFR: 8306842: Classfile API performance improvements [v5]

[Glavo]

On Mon, 15 May 2023 14:48:58 GMT, Adam Sotona <asotona at openjdk.org> wrote:

>> 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 two additional commits since the last revision:
> 
>  - changed LinkedList to ArrayList in RebuildMethodBodies benchmark
>  - added RepeatedModelTraversal JMH benchmark

test/micro/org/openjdk/bench/jdk/classfile/RepeatedModelTraversal.java line 54:

> 52:     @Setup(Level.Trial)
> 53:     public void setup() throws IOException {
> 54:         models = new LinkedList<>();

I think `ArrayList` can be used instead of `LinkedList` here too. 

While this may not be an actual improvement, I don't think `LinkedList` should be used unless necessary.

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PR Review Comment: https://git.openjdk.org/jdk/pull/13671#discussion_r1194256653