BE-265: HashQL: Make CopyPropagation aware of local re-assignments

[indietyp]

🌟 What is the purpose of this PR?

Enhance the Place::local function to be more efficient by making it a const fn that doesn't require an interner parameter, and add a convenient From<Local> implementation for Operand to simplify code that converts locals to operands.

🔍 What does this change?

• Make Place::local() a const fn that doesn't require an interner parameter
• Add From<Local> implementation for Operand to simplify code
• Update all call sites to use the new signature
• Enhance copy propagation to handle both constant and local value propagation
• Add tests for copy propagation with local values

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:

• are internal and do not require a docs change

🕸️ Does this require a change to the Turbo Graph?

The changes in this PR:

• do not affect the execution graph

🛡 What tests cover this?

• Added new tests for copy propagation with local values
• Existing tests continue to pass with the updated API

[cursor]

PR Summary

Core API changes

• Place::local is now a const fn without an Interner param; uses Interned::empty() for projections
• Target::block is now interner-free and const; initializes empty args via Interned::empty()
• Adds From<Local> for Operand for concise Local→Operand conversion
• Updated usages across MIR passes, reification, builders, and analyses to new constructors

Copy propagation improvements

• Propagates both constants and copies by tracking KnownValue (constant or local)
• Substitutes operands with known locals/constants; propagates through block params when predecessors agree
• Retains limitations (no projections; no loop fixpoint)

Refactors/cleanup

• Simplifies CFG simplify simplify_goto signature (drops context param)
• Adjusts data-dependency resolution and SSA repair to new Place::local

Tests/docs

• Adds tests for copy propagation of locals: simple_copy, copy_chain, block_param_copy, and disagreement cases
• Updates doc examples to use new Target::block/Place::local signatures

^{Written by Cursor Bugbot for commit 1c1b05d. This will update automatically on new commits. Configure here.}

[indietyp]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• 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 👈 (View in Graphite)
• 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
• 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.

[codspeed-hq]

CodSpeed Performance Report

Merging #8231 will not alter performance

_{Comparing bm/be-265-hashql-track-locals-inside-of-copy-propagation (1c1b05d) with bm/be-264-hashql-rename-sroa-to-projectionforwarding (0fc7994)}

Summary

✅ 17 untouched

[codecov]

Codecov Report

❌ Patch coverage is 96.42857% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 59.81%. Comparing base (0fc7994) to head (1c1b05d).

Files with missing lines	Patch %	Lines
libs/@local/hashql/mir/src/body/operand.rs	0.00%	3 Missing ⚠️
libs/@local/hashql/mir/src/reify/rvalue.rs	50.00%	1 Missing ⚠️

Additional details and impacted files

@@                                   Coverage Diff                                    @@
##           bm/be-264-hashql-rename-sroa-to-projectionforwarding    #8231      +/-   ##
========================================================================================
+ Coverage                                                 59.78%   59.81%   +0.02%     
========================================================================================
  Files                                                      1066     1066              
  Lines                                                    106191   106239      +48     
  Branches                                                   4478     4472       -6     
========================================================================================
+ Hits                                                      63488    63545      +57     
+ Misses                                                    41963    41956       -7     
+ Partials                                                    740      738       -2     

Flag	Coverage Δ
rust.hashql-compiletest	46.65% <ø> (ø)
rust.hashql-mir	87.39% <96.42%> (+0.17%)	⬆️

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[augmentcode]

🤖 Augment PR Summary

Summary: Extends HashQL MIR copy propagation to handle local-to-local copies (not just constants) and simplifies MIR place/operand helpers.

Changes:

• Place::local(Local) is now a const fn and no longer needs an Interner; it uses a canonical empty projection list.
• Adds From<Local> for Operand to streamline local-to-operand conversions.
• Updates call sites across MIR builder, reifier, SSA repair, CFG simplify, and data-dependency resolution to the new Place::local signature.
• Generalizes CopyPropagation to track a KnownValue (constant or local) and substitute operands, including via block-parameter agreement.
• Adds new unit tests + snapshots for simple copy, chained copy, and block-param copy/disagreement scenarios.

Technical Notes: The pass remains single-pass (reverse postorder), does not traverse projections, and assumes SSA-like single-assignment locals for soundness.

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[augmentcode]

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