BE-258: HashQL: Add Changed enum to track MIR transformation pass modifications

[indietyp]

Add Changed enum to MIR transform passes for tracking modifications

🌟 What is the purpose of this PR?

This PR adds a Changed enum to MIR transform passes to track whether a pass modified the code. This enables more efficient pass pipelines by allowing subsequent passes to be skipped when no changes were made.

🔍 What does this change?

• Adds a new Changed enum (Yes, No, Unknown) that transform passes return to indicate modifications
• Updates all transform pass implementations to return the appropriate Changed value
• Modifies test harnesses to capture and display the Changed value in snapshots
• Updates documentation to describe the new feature in the testing guide
• Improves benchmarks to track and propagate change status through pass pipelines

🛡 What tests cover this?

• All existing transform pass tests have been updated to include the Changed value in snapshots
• The test harness now verifies the correct Changed value is returned

Pre-Merge Checklist 🚀

🚢 Has this modified a publishable library?

This PR:

• does not modify any publishable blocks or libraries, or modifications do not need publishing

📜 Does this require a change to the docs?

The changes in this PR:

• require changes to docs which are made as part of this PR

🕸️ Does this require a change to the Turbo Graph?

The changes in this PR:

• do not affect the execution graph

[cursor]

PR Summary

Adds change tracking to MIR transformations and surfaces it in tests and benches.

• Introduces Changed enum and updates TransformPass::run to return Changed with helpers (conservative, optimistic, From<bool>)
• Refactors passes (cfg_simplify, sroa, inst_simplify, dse, dbe, dle, ssa_repair, cp) to compute and return Changed, including early exits and aggregation where applicable
• Test harnesses now capture and snapshot Changed (formatted separator replaced with Changed: Yes/No/Unknown); all related snapshots updated
• Benchmarks/plumbing updated to propagate and combine Changed across pipeline stages; run_bencher returns and carries values
• Docs updated: testing skill and MIR builder guide document Changed and the new snapshot pattern; reference paths fixed from resources/* to references/*

^{Written by Cursor Bugbot for commit eaca057. This will update automatically on new commits. Configure here.}

[indietyp]

• BE-273: HashQL: Profile and benchmark MIR interpreter #8251
• BE-272: HashQL: Add numeric addition and subtraction operators to MIR #8250
• BE-257: HashQL: Implement MIR interpreter with runtime value representation #8245
• BE-271: HashQL: Implement PostInline pass #8240
• BE-269: HashQL: Move PreInline out into Canonicalization pass #8239
• BE-268: HashQL: Rename PreInlining to PreInline for consistency #8238
• BE-270: HashQL: Optimize empty tuples to unit constants in MIR #8237
• BE-197: Implement MIR inline pass for HashQL #8236
• BE-267: Use bump scopes instead of full resets across transformation passes #8234
• BE-266: HashQL: Implement PreInlining pass for MIR optimization #8233
• BE-265: HashQL: Make CopyPropagation aware of local re-assignments #8231
• BE-264: HashQL: Rename SROA to ForwardSubstitution for better semantic clarity #8230
• BE-263: HashQL: add body! macro for declarative MIR construction in tests #8229
• BE-261: HashQL: Implement Administrative Reduction pass for MIR #8227
• BE-262: HashQL: Do not intern empty slices #8223
• BE-260: HashQL: Switch to bump allocator with scoping support #8218
• BE-259: HashQL: Add benchmarks for type system operations #8216
• BE-227: HashQL: Implement call graph analysis for MIR #8214
• BE-258: HashQL: Add Changed enum to track MIR transformation pass modifications #8210 👈 (View in Graphite)
• BE-255: HashQL: Implement Copy Propagation (CP) pass for MIR #8207
• BE-231: HashQL: Add InstSimplify pass for MIR instruction simplification and constant folding #8206
• BE-254: Add CodSpeed benchmarking for HashQL MIR transformation passes #8204
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[codecov]

Codecov Report

❌ Patch coverage is 89.79592% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 59.27%. Comparing base (86f263f) to head (eaca057).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
libs/@local/hashql/mir/src/pass/mod.rs	23.07%	10 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #8210   +/-   ##
=======================================
  Coverage   59.26%   59.27%           
=======================================
  Files        1191     1191           
  Lines      113436   113489   +53     
  Branches     4982     4986    +4     
=======================================
+ Hits        67232    67273   +41     
- Misses      45428    45440   +12     
  Partials      776      776           

Flag	Coverage Δ
rust.hashql-compiletest	46.65% <ø> (ø)
rust.hashql-mir	88.23% <89.79%> (-0.07%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[codspeed-hq]

CodSpeed Performance Report

Merging this PR will improve performance by ×2.6

_{Comparing bm/be-258-hashql-implement-transformationpass-changed-detection (eaca057) with main (86f263f)}

Summary

⚡ 7 improved benchmarks
✅ 7 untouched benchmarks
🗄️ 3 archived benchmarks run¹

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
⚡	complex	68.1 µs	55.7 µs	+22.24%
⚡	complex	18.8 µs	8.1 µs	×2.3
⚡	diamond	50.1 µs	38.3 µs	+30.7%
⚡	diamond	20.8 µs	7.9 µs	×2.6
⚡	complex	25.4 µs	12 µs	×2.1
⚡	diamond	15.5 µs	7.5 µs	×2.1
⚡	linear	11.9 µs	7 µs	+69.54%

Footnotes

1. 3 benchmarks were run, but are now archived. If they were deleted in another branch, consider rebasing to remove them from the report. Instead if they were added back, click here to restore them. ↩

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

2 Skipped Deployments

Project	Deployment	Review	Updated (UTC)
ds-theme	Ignored	Preview	Jan 15, 2026 3:10pm
hashdotdesign	Ignored	Preview	Jan 15, 2026 3:10pm

[graphite-app]

Merge activity

• Jan 15, 3:10 PM UTC: Graphite rebased this pull request, because this pull request is set to merge when ready.
• Jan 15, 3:10 PM UTC: Graphite rebased this pull request, because this pull request is set to merge when ready.
• Jan 16, 12:45 PM UTC: A user started a stack merge that includes this pull request via Graphite.