RFR: 8371419: IGV: Add view to visualise dominator tree and dominator information

[Damon Fenacci]

On Wed, 19 Nov 2025 09:58:59 GMT, Roberto Castañeda Lozano <rcastanedalo at openjdk.org> wrote:

> Would it be possible to avoid dumping dominator information as node properties, to reduce the size of the graph dump?

The idea I had in mind was to dump all the information we compute in C2 about dominators/blocks and the information in nodes and blocks come from different sources (and didn't think 2 small fields per node would make a lot of difference 😉). 
When the dominator information comes from C2 the block information in the node properties comes from [`_node_to_block_mapping` ](https://github.com/openjdk/jdk/blob/2347e9a4e14eb14700415c58130885a7d06522d5/src/hotspot/share/opto/block.hpp#L403) whereas the block one directly [from the blocks](https://github.com/openjdk/jdk/blob/2347e9a4e14eb14700415c58130885a7d06522d5/src/hotspot/share/opto/block.hpp#L118) (and might not be yet in sync while computing GCM as I found out:
<img height="300" alt="image" src="https://github.com/user-attachments/assets/c20a72d0-5af2-483c-9a5b-8cec798ecb58" />


> I like the idea of distinguishing visually when control-flow information originates from HotSpot and when it is approximated by IGV, ... once the graph is saved into a file (from IGV) the information is lost

Oops, I didn't really think about this.

> I think this is a great and much-needed IGV feature, but one that would require substantial work to get right, so my suggestion would be leaving it out of the scope of this RFE and creating a separate RFE just for it. What do you think?

Yes, it is probably better to leave it for now. I'll file a new RFE. Thanks @robcasloz.

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PR Comment: https://git.openjdk.org/jdk/pull/28293#issuecomment-3580934752