RFR: 8317349: Randomize order of macro node expansion in C2 [v3]

[Christian Hagedorn]

On Tue, 6 Feb 2024 10:13:23 GMT, Daniel Lundén <dlunden at openjdk.org> wrote:

>> This changeset adds a flag `StressMacroExpansion` which randomizes macro expansion ordering for stress testing purposes.
>> 
>> Changes:
>> - Implement the flag `StressMacroExpansion`.
>> - Add functionality tests for `StressMacroExpansion`, analogous to testing for previous stress flags such as `StressIGVN`.
>> - Add `StressMacroExpansion` to a number of tests that already turn on all other stress flags (and therefore should also use `StressMacroExpansion`).
>> - Rename the previous compiler phase `MACRO_EXPANSION` to `AFTER_MACRO_EXPANSION`.
>> - Add new Ideal phases related to macro expansion, allowing `StressMacroExpansion` testing. Below is a sample phase list screenshot including some of the new phases (IGV print level 4).
>>    <p align="center">
>>       <img src="https://github.com/openjdk/jdk/assets/4222397/b65c67a0-13f7-45a6-aef4-5dfe259dab66" width="300">
>>    </p>
>> 
>> 
>> Question for the review: are the new macro expansion Ideal phases OK, or should we change anything?
>> 
>> Testing:
>> - [GitHub Actions](https://github.com/dlunde/jdk/actions/runs/7797963709)
>> - 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.
>
> Daniel Lundén has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Update to print level 5 and fix copyright

src/hotspot/share/opto/macro.cpp line 2580:

> 2578:     assert(C->macro_count() == (old_macro_count - 1), "expansion must have deleted one node from macro list");
> 2579:     if (C->failing())  return true;
> 2580:     C->print_method(PHASE_AFTER_MACRO_EXPANSION_ARRAYCOPY, 5, n);

Should we rename this to something more generic since we are not only expanding array copy nodes but also locks and subtype checks? Maybe `PHASE_AFTER_MACRO_EXPANSION_STEP`? We could also use the same phase name for the allocations below since we also print the node name with `n` which already provides the required information about what node was expanded.

src/utils/IdealGraphVisualizer/README.md line 34:

> 32: * `N=3`: additionally, after every minor phase
> 33: * `N=4`: additionally, after every loop optimization
> 34: * `N=5`: additionally, after every effective IGVN step and every macro expansion (slow)

Suggestion:

* `N=5`: additionally, after every effective IGVN and every macro expansion step (slow)

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PR Review Comment: https://git.openjdk.org/jdk/pull/17684#discussion_r1479553544
PR Review Comment: https://git.openjdk.org/jdk/pull/17684#discussion_r1479548717