RFR: 8339576: Speed up raw bytecode processing in ClassFile API [v2]

[Claes Redestad]

On Thu, 5 Sep 2024 15:39:07 GMT, Chen Liang <liach at openjdk.org> wrote:

>> Currently, raw bytecode access goes through multiple wrappers, include one from ClassFile API and another ByteBuffer for merged big endian value reads. We can merge the ByteBuffer =into the ClassFile API one (RawBytecodeHelper) for safer access.
>> 
>> RawBytecodeHelper is also restructured so we avoid allocating it on the heap. Large `rawNext` method is now also inlined into the smaller `next` method.
>> 
>> Current benchmark results show this significantly speeds up `jdk.classfile.Write` and some degree of speedup for simple lambda startup. The impact on general application workloads is minuscule, but this doesn't seem to bring any regression.
>> 
>> Pinging @wenshao and @cl4es for review.
>
> Chen Liang has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Avoid repeated field usage, eliminate bound checks

Marked as reviewed by redestad (Reviewer).

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

PR Review: https://git.openjdk.org/jdk/pull/20863#pullrequestreview-2283641297