RFR: 8282053: IGV: refine schedule approximation

[Daniel Lundén]

On Tue, 1 Apr 2025 07:23:04 GMT, Daniel Skantz <dskantz at openjdk.org> wrote:

> This patch refines the schedule approximation in IGV by 1)  placing parm. and projection nodes in the same block as their predecessors, and 2) disallows erroneously considering machine nodes such as prefetchAlloc and rep_stos as CFG nodes.
> 
> The reader may refer to the corresponding JBS issue where graphs sampled before and after the change are attached.
> 
> Testing: T1-T3 with no failures. Opened graphs before and after the change and saw no obvious problems. Opened a large number of graphs in CFG view and observed no unexpected IGV warnings, errors or assert failures.

Good CFG scheduling approximation improvement! Just one style suggestion.

src/utils/IdealGraphVisualizer/ServerCompiler/src/main/java/com/sun/hotspot/igv/servercompiler/ServerCompilerScheduler.java line 800:

> 798:                 n.isCFG = true;
> 799:             } else if (n.inputNode.getProperties().get("type").equals("bottom")
> 800:                        && n.preds.size() > 0 &&

Suggestion:

            } else if (n.inputNode.getProperties().get("type").equals("bottom") &&
                       n.preds.size() > 0 &&

For consistent placement of `&&` (already a problem before this changeset, but might as well fix now)

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

Marked as reviewed by dlunden (Committer).

PR Review: https://git.openjdk.org/jdk/pull/24350#pullrequestreview-2732918158
PR Review Comment: https://git.openjdk.org/jdk/pull/24350#discussion_r2022983828