[code-reflection] Integrated: Bytecode locals compaction

[Adam Sotona]

On Mon, 9 Sep 2024 17:35:04 GMT, Adam Sotona <asotona at openjdk.org> wrote:

> `LocalsCompactor` is a bytecode transformation reducing generated method `maxLocals` by re-using local slots.
> Roundtrip of lift and bytecode generation doubles the `maxLocals` value, while `LocalsCompactor` reduces the regression by 50%.
> 
> Lifting of compacted locals revealed bugs in `LocalsTypeMapper` variables graph construction. This patch includes significantly  refactored `LocalsTypeMapper` to support lifting of compacted locals.
> 
> `BytecodeGenerator` has slightly improved performance (so `TestSmallCorpus` finishes in a reasonable time). However performance has not been main focus of this PR.
> 
> `TestSmallCorpus` has been slightly refactored to provide better debugging feedback and compaction statistics. Overall stability is still >99%.
> 
> Please review.
> 
> Thanks,
> Adam

This pull request has now been integrated.

Changeset: 15e8b6e4
Author:    Adam Sotona <asotona at openjdk.org>
URL:       https://git.openjdk.org/babylon/commit/15e8b6e48a1c799f420583d69988e822fb047164
Stats:     684 lines in 5 files changed: 483 ins; 102 del; 99 mod

Bytecode locals compaction

Reviewed-by: psandoz

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PR: https://git.openjdk.org/babylon/pull/224