RFR: 8293170: Improve encoding of the debuginfo nmethod section [v2]

[Boris Ulasevich]

On Mon, 3 Oct 2022 20:34:56 GMT, Evgeny Astigeevich <eastigeevich at openjdk.org> wrote:

>> Boris Ulasevich has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains four commits:
>> 
>>  - warning fix and name fix
>>  - optimize the encoding
>>  - fix
>>  - 8293170: Improve encoding of the debuginfo nmethod section
>
> src/hotspot/share/compiler/oopMap.hpp line 377:
> 
>> 375:   OopMapValue current()                 { return _omv; }
>> 376: #ifdef ASSERT
>> 377:   int stream_position()                 { return _stream.position(); }
> 
> This change is an example that something is wrong with the design.
> There is a concrete class `CompressedReadStream` with expected behaviour of `position`: no changes to `_stream`.  We have to break this contract to be able to compile `OopMapStream`.

This change is unrolled as CompressedSparseDataReadStream is a separate class now (rework to avoid the virtual functions)

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PR: https://git.openjdk.org/jdk/pull/10025