[code-reflection] RFR: Aggregated work on Verifier and BytecodeLift deconstruction

[Adam Sotona]

On Fri, 18 Oct 2024 10:06:38 GMT, Adam Sotona <asotona at openjdk.org> wrote:

> This PR is aggregated continuation of work on `Verifier` #247 and new simplified and deconstructed implementation of `BytecodeLift`.
> 
> Work on `Verifier` revealed bugs in `BytecodeLift`.
> Fixing of the bugs adds more complexity to already very complex `BytecodeLift`.
> The goal of this PR is to deconstruct `BytecodeLift` to its bare bones  and re-introduce a kind of bytecode dialect:
> - `UnresolvedType.Ref` and `UnresolvedType.Int` represent references and int with all its possible sub-types
> - `SlotOp` is an intermediate model of local variables
> - `SlotToVarTransformer` transforms `SlotOp` to `CoreOp.VarOp`
> - `UnresolvedTypesTransformer` transforms `UnresolvedType.Ref` and `UnresolvedType.Int` to `JavaType`.

This is not final state of the `BytecodeLift` conversion nor `Verifier` implementation.
`TestSmallCorpus` actually pass first round without an errors, however second round indicates verification errors related to exception regions on the lifted model (Verifier newly checks exception region stack of the model).

Please review proposed changes.

Thanks,
Adam

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PR Comment: https://git.openjdk.org/babylon/pull/258#issuecomment-2450165187