RFR: 8282053: IGV: refine schedule approximation [v2]

[Damon Fenacci]

On Tue, 1 Apr 2025 14:42:47 GMT, Daniel Skantz <dskantz at openjdk.org> wrote:

>> This patch refines the schedule approximation in IGV by 1)  placing parm. and projection nodes in the same block as their predecessors, and 2) disallows erroneously considering machine nodes such as prefetchAlloc and rep_stos as CFG nodes.
>> 
>> The reader may refer to the corresponding JBS issue where graphs sampled before and after the change are attached.
>> 
>> Testing: T1-T3 with no failures. Opened graphs before and after the change and saw no obvious problems. Opened a large number of graphs in CFG view and observed no unexpected IGV warnings, errors or assert failures.
>
> Daniel Skantz has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Update src/utils/IdealGraphVisualizer/ServerCompiler/src/main/java/com/sun/hotspot/igv/servercompiler/ServerCompilerScheduler.java
>   
>   Co-authored-by: Daniel Lundén <daniel.lunden at oracle.com>

Nice! Thanks @danielogh!

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Marked as reviewed by dfenacci (Committer).

PR Review: https://git.openjdk.org/jdk/pull/24350#pullrequestreview-2734882114