RFR: 8368675: IGV: nodes are wrongly marked as changed in the difference view

[Damon Fenacci]

On Fri, 26 Sep 2025 08:34:34 GMT, Roberto Castañeda Lozano <rcastanedalo at openjdk.org> wrote:

> This changeset refines IGV's node difference analysis to ignore changes in node properties that are derived by IGV, as opposed to generated by HotSpot. Derived properties include the label and color of each node. Ignoring changes in these properties prevents IGV from wrongly marking equal nodes as "changed" (colored in yellow) when showing the difference between two graphs:
> 
> <img width="2323" height="651" alt="before-after" src="https://github.com/user-attachments/assets/ea51c86d-4719-45c0-b615-e6e4b8aec023" />
> 
> **Testing:** tier1 and manual testing on a few graphs.

Thanks @robcasloz! I've been wondering why sometimes there seemed to be a lot of yellow nodes 😉 Looks good to me too.

src/utils/IdealGraphVisualizer/Data/src/main/java/com/sun/hotspot/igv/data/serialization/Parser.java line 84:

> 82:     public static final String TO_INDEX_PROPERTY = "toIndex";
> 83:     public static final String TO_INDEX_ALT_PROPERTY = "index";
> 84:     public static final String EDGE_LABEL_PROPERTY = "label";

changed to improve its "expressiveness"?

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Marked as reviewed by dfenacci (Committer).

PR Review: https://git.openjdk.org/jdk/pull/27515#pullrequestreview-3272764606
PR Review Comment: https://git.openjdk.org/jdk/pull/27515#discussion_r2382759560