RFR: 8339576: Speed up raw bytecode processing in ClassFile API

[Claes Redestad]

On Thu, 5 Sep 2024 06:24:46 GMT, Shaojin Wen <swen 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.
>
> src/java.base/share/classes/jdk/internal/classfile/impl/RawBytecodeHelper.java line 235:
> 
>> 233:      * we have a valid opcode.
>> 234:      */
>> 235:     public boolean next() {
> 
> In C1, this cannot be inlined. See if you need to add ForceInline

I don't think we should worry too much about making C1 inline more aggressively.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20863#discussion_r1745532319