RFR: 8356761: IGV: dump escape analysis information

[Anton Seoane Ampudia]

On Wed, 12 Nov 2025 11:01:30 GMT, Roberto Castañeda Lozano <rcastanedalo at openjdk.org> wrote:

>> This PR introduces new IGV dumps, property fields and filters related to escape analysis information.
>> 
>> The C2 escape analysis algorithm is carried out in six primary steps, of which many have interesting sub-steps (e.g. `split_unique_types`) or present an iterative nature where access to intermediate results can aid debugging and analysis. Additionally, escape analysis relies on an "intermediate structure" called the _connection graph_, which is also particularly valuable for deeper investigations.
>> 
>> With this changeset, escape analysis information is now dumped at key points throughout the algorithm, with a degree of granularity (from only the basic steps to in-detail iterative dumping). The dumps include several property fields, such as:
>> 
>> - Node escape “level”.
>> - Scalar replaceability.
>> - Node type within the connection graph (per [C2 Escape Analysis connection graph](https://wiki.openjdk.org/display/HotSpot/EscapeAnalysis)).
>> 
>> This is achieved by passing the `ConnectionGraph` in use to the `IdealGraphPrinter` during escape analysis, so that these properties can be dumped. After escape analysis, remaining interesting information that is left until macro elimination (and consequent elimination of non-escaping, replaceable allocations) is also dumped.
>> 
>> Additionally, two filters are provided: one for displaying the connection node type in the IGV node box, and another one for color-scaling nodes based on their escaping/scalar status.
>> 
>> **Testing:** passes tiers 1-3, manual testing in IGV
>
> src/hotspot/share/opto/escape.cpp line 3153:
> 
>> 3151:               revisit_reducible_phi_status(jobj, reducible_merges);
>> 3152:               found_nsr_alloc = true;
>> 3153:               _compile->print_method(PHASE_EA_PROPAGATE_NSR_ITER, 5);
> 
> Why dumping here and not for the `use->is_LocalVar()` case? Anyway, maybe it would be more useful to dump one or two levels up instead, e.g. for each `jobj`.

Absolutely. I guess at some point of trying different places I forgot to move it back where it should be

> src/hotspot/share/opto/escape.cpp line 4749:
> 
>> 4747:   uint new_index_end = (uint) _compile->num_alias_types();
>> 4748: 
>> 4749:   _compile->print_method(PHASE_EA_AFTER_SPLIT_UNIQUE_TYPES_1, 5);
> 
> I guess there is no `PHASE_EA_AFTER_SPLIT_UNIQUE_TYPES_2` because Phase 2 does not change the state of the Ideal graph or the connection graph and hence the changes are not observable within IGV, right?

Correct

> src/hotspot/share/opto/escape.cpp line 5173:
> 
>> 5171:   }
>> 5172: }
>> 5173: 
> 
> Spurious change?

Yes, I had a function there and when removing it I got rid of the line apparently.

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PR Review Comment: https://git.openjdk.org/jdk/pull/28060#discussion_r2518098779
PR Review Comment: https://git.openjdk.org/jdk/pull/28060#discussion_r2518099327
PR Review Comment: https://git.openjdk.org/jdk/pull/28060#discussion_r2518106520