test(codegen): assert the push-barrier ordering over the CFG region, not a text slice (#7708)

[proggeramlug]

Closes the last residue of #7708. The census rewrite (CFG walk from apush.inbounds) replaces the text slice that went blind when the barrier legally moved downstream of apush.realloc — full analysis and the shared verdict with the peer session on #7708's thread and in the fragment.

• Targeted suite: 3/3 green.
• Sabotage: cutting the successor walk (recreating the old blindness) reds exactly this test; restore → green. Committed before sabotage this time.
• Full cargo test -p perry-codegen: 1,306 passed; the ONE remaining failure is typed_f64_receiver_method_clone_raw_loads_after_composed_guards red again on main — window #7833..#7842, prop_cse prime suspect #7857 (typed_f64, red on main since the perf(transform): eliminate redundant property reads across diverging guard chains #7833..fix(codegen,runtime): a declared string is not a proof, so it may not pick the + operator #7842 window — filed with suspect ranking, not this PR's doing: it fails identically on main without this change).
• The fixture pushes a heap pointer, so the assertion guards a real barrier invariant — this is the perf(class-fields): a conforming pointer store skips the layout note (#5094) #7698 remedy, not a deletion.

Summary by CodeRabbit

• Bug Fixes

  • Improved validation of push barriers across complex control-flow paths.
  • Added checks to ensure barrier operations, storage updates, and layout metadata appear in the correct order.
  • Extended equivalent validation to class-field stores.

• Tests

  • Expanded coverage for local arrays and large-object handling, including scenarios spanning multiple execution blocks.

• Documentation

  • Added a changelog entry describing the updated validation behavior.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 45e12a58-48bd-40f6-954f-f5acf20261c2

📥 Commits

Reviewing files that changed from the base of the PR and between 079e646 and 3fc3df1.

📒 Files selected for processing (2)

• changelog.d/7858-push-barrier-cfg-census.md
• crates/perry-codegen/tests/large_object_barriers.rs

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📝 Walkthrough

Walkthrough

The push-barrier test now traverses the reachable apush.* control-flow region. It verifies in-bounds store placement and ordering of layout notes and write barriers across basic blocks. The changelog documents the CFG-based validation.

Changes

Push-barrier CFG census

Layer / File(s)	Summary
CFG region traversal crates/perry-codegen/tests/large_object_barriers.rs	ApushRegion parses LLVM blocks, extracts successors, traverses reachable apush.* blocks, and locates markers by block and offset.
Barrier ordering assertions crates/perry-codegen/tests/large_object_barriers.rs, changelog.d/7858-push-barrier-cfg-census.md	The test requires the direct store in the in-bounds block and checks store, slot-layout note, and write-barrier ordering. The changelog records the validation changes and test status.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Possibly related PRs

• PerryTS/perry#7602: Related array-push barrier code and test changes.
• PerryTS/perry#6831: Related validation of array slot layout-note and write-barrier ordering.
• PerryTS/perry#7120: Related LLVM IR test validation scoped to generated regions.

Suggested reviewers: thehypnoo

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch test/7708-cfg-walk-push-barrier

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