Integrated: 8325478: Restructure the macro expansion compiler phase to not include macro elimination

[Saranya Natarajan]

On Fri, 6 Jun 2025 22:40:34 GMT, Saranya Natarajan <snatarajan at openjdk.org> wrote:

> This changeset restructures the macro expansion phase to not include macro elimination and also adds a flag StressMacroElimination which randomizes macro elimination ordering for stress testing purposes.
> 
> Changes:
> - Implemented a method `eliminate_opaque_looplimit_macro_nodes` that removes the functionality for eliminating Opaque and LoopLimit nodes from the `expand_macro_nodes ` method. 
> - Introduced compiler phases` PHASE_AFTER_MACRO_ELIMINATION` 
> -  Added a new Ideal phase for individual macro elimination steps. 
> - Implemented the flag `StressMacroElimination`. Added functionality tests for `StressMacroElimination`, similar to previous stress flag `StressMacroExpansion` ([JDK-8317349](https://bugs.openjdk.org/browse/JDK-8317349)).
> 
> Below is a sample screenshot (IGV print level 4 ) mainly showing the new phase .
> ![image](https://github.com/user-attachments/assets/16013cd4-6ec6-4939-ac66-33bb03d59cd6)
> 
> Questions to reviewers: 
> - Is the new macro elimination phase OK, or should we change anything?
> - In `compile.cpp `, `PHASE_ITER_GVN_AFTER_ELIMINATION` follows `PHASE_AFTER_MACRO_ELIMINATION` in the current fix. Should `PHASE_ITER_GVN_AFTER_ELIMINATION` be removed ? 
> 
> Testing:
> GitHub Actions
> tier1 to tier5 on windows-x64, linux-x64, linux-aarch64, macosx-x64, and macosx-aarch64.
> Tested that thousands of graphs are correctly opened and visualized with IGV using the same test used in  ([JDK-8317349](https://bugs.openjdk.org/browse/JDK-8317349))

This pull request has now been integrated.

Changeset: eac8f5d2
Author:    Saranya Natarajan <snatarajan at openjdk.org>
Committer: Daniel Lundén <dlunden at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/eac8f5d2c99e1bcc526da0f6a05af76e815c2db9
Stats:     77 lines in 11 files changed: 54 ins; 8 del; 15 mod

8325478: Restructure the macro expansion compiler phase to not include macro elimination

Reviewed-by: kvn, dlunden

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PR: https://git.openjdk.org/jdk/pull/25682