Integrated: 8368753: IGV: improve CFG view of difference graphs

[Roberto Castañeda Lozano]

On Fri, 26 Sep 2025 09:48:57 GMT, Roberto Castañeda Lozano <rcastanedalo at openjdk.org> wrote:

> This changeset improves the control-flow graph view of difference graphs by:
> 
> 1. ensuring that nodes are scheduled locally within each block, and
> 2. hiding internal, artificial blocks containing nodes that remain in the graph even if they are dead, such as the top constant node.
> 
> The following screenshot illustrates the effect of scheduling nodes locally:
> 
> <img width="3853" height="1033" alt="JDK-8368753" src="https://github.com/user-attachments/assets/bdc0f6de-3d28-4615-9e0d-221de2ad4770" />
> 
> For example, before this changeset (left) the `Return` node in B9 is scheduled at the beginning of the block. After the changeset (right), this node is scheduled last, as expected.
> 
> **Testing:** tier1 and manual testing on a few graphs.

This pull request has now been integrated.

Changeset: 59e87437
Author:    Roberto Castañeda Lozano <rcastanedalo at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/59e87437b4f9259121710dca5e595ca714c3e71b
Stats:     65 lines in 4 files changed: 44 ins; 11 del; 10 mod

8368753: IGV: improve CFG view of difference graphs

Reviewed-by: chagedorn, mhaessig, dfenacci

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PR: https://git.openjdk.org/jdk/pull/27520