Integrated: 8361144: Strenghten the Ideal Verification in PhaseIterGVN::verify_Ideal_for by comparing the hash of a node before and after Ideal

[Benoît Maillard]

On Tue, 1 Jul 2025 11:35:06 GMT, Benoît Maillard <bmaillard at openjdk.org> wrote:

> This PR adds a node hash comparison after calling `Ideal` in `PhaseIterGVN::verify_Ideal_for` to introduce an additional layer of verification for missed optimizations. Previously, we relied on the return value of `Ideal`, which is expected to be `nullptr` if no transformation was done.
> 
> By also checking the node's hash before and after `Ideal`, we could catch inconsistencies in the implementation or unintended modifications to the graph. Both of these may indicate missed or incomplete optimizations.
> 
> ### Testing
> - [x] [GitHub Actions](https://github.com/benoitmaillard/jdk/actions?query=branch%3AJDK-8361144)
> - [x] tier1-3, plus some internal testing
> 
> Thank you for reviewing!

This pull request has now been integrated.

Changeset: a531c9ae
Author:    Benoît Maillard <bmaillard at openjdk.org>
Committer: Damon Fenacci <dfenacci at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/a531c9aece200d27d7870595eee8e14e39e9bd00
Stats:     12 lines in 1 file changed: 11 ins; 0 del; 1 mod

8361144: Strenghten the Ideal Verification in PhaseIterGVN::verify_Ideal_for by comparing the hash of a node before and after Ideal

Co-authored-by: Emanuel Peter <epeter at openjdk.org>
Reviewed-by: galder, dfenacci, epeter

-------------

PR: https://git.openjdk.org/jdk/pull/26064