[code-reflection] Integrated: Testing BytecodeLift and BytecodeGenerator roundtrip stability

[Adam Sotona]

On Thu, 15 Feb 2024 08:50:35 GMT, Adam Sotona <asotona at openjdk.org> wrote:

> Hi,
> I've added `TestLiftSmallCorpus::testDoubleRoundtripStability` to test stability of the `BytecodeLift` and `BytecodeGenerator` roundtrip on JDK classes (aka "Small Corpus"). 
> 
> The test takes ~40k methods from JDK classes and tries to lift them from bytecode, generate, lift again and generate again. Only about 4300 methods pass the roundtrip now, because `BytecodeLift` and `BytecodeGenerator` are still under construction.
> 
> The test then compares "normalized" bytecode from the first round and the second round and fails with printed details if differ. The test actually contains a non-zero error threshold before failure. This threshold can be manually adjusted when working on `BytecodeLift` and `BytecodeGenerator` improvements.
> This approach allows to incrementally fix `BytecodeLift` and `BytecodeGenerator` roundtrip, as well as to extend their coverage.
> 
> This patch also includes several fixes of bugs discovered during work on `TestLiftSmallCorpus`:
> - conditional branches are unwound to avoid growing number of blocks during the round trip
> - conditional branches are inverted to fix roundtrip stability
> - partial fix of block parameters construction
> - partial fix of the locals overrides
> - aggressive local variable slots overrides in `BytecodeGenerator` are temporary disabled until `BytecodeLift` is ready to support it 
> - fixed redundant block argument assignements of unused variables in `BytecodeGenerator`
> - fixed storing of values into invalid slots
> 
> Partial fix means it significantly reduced the error threshold (in order of magnitudes), however there are still some cases failing.
> 
> I would like to integrate this patch, because it introduces a tool to allow subsequent incremental progress.
> 
> Please review.
> 
> Thank you,
> Adam

This pull request has now been integrated.

Changeset: 8c6b5754
Author:    Adam Sotona <asotona at openjdk.org>
URL:       https://git.openjdk.org/babylon/commit/8c6b5754fd043348ec193d78b5b505111fe7b3b9
Stats:     384 lines in 5 files changed: 293 ins; 43 del; 48 mod

Testing BytecodeLift and BytecodeGenerator roundtrip stability

Reviewed-by: psandoz

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PR: https://git.openjdk.org/babylon/pull/24