8328107: Shenandoah/C2: TestVerifyLoopOptimizations test failure

[rwestrel]

The failure occurs because a load barrier is expanded on the backedge of the counted loop. That breaks the expected counted loop shape. The fix I propose is to replace the CountedLoop with a Loop node when that happens. We're basically done with optimizations related to counted loop at this point so this shouldn't make a difference.

/cc hotspot-compiler

---

Progress

• [ ] Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• [x] Change must not contain extraneous whitespace
• [x] Commit message must refer to an issue

Issue

• JDK-8328107: Shenandoah/C2: TestVerifyLoopOptimizations test failure (Bug - P3)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/19259/head:pull/19259
$ git checkout pull/19259

Update a local copy of the PR:
$ git checkout pull/19259
$ git pull https://git.openjdk.org/jdk.git pull/19259/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 19259

View PR using the GUI difftool:
$ git pr show -t 19259

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/19259.diff

Webrev

Link to Webrev Comment