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refactor(joinir): Phase 255 P2 - loop_invariants + var() unification + Phase 256 prep
## Task A: Loop Invariants Architecture (Option A - Boundary Extension)
Introduced explicit loop_invariants concept for variables that are:
- Used in loop body but never modified (e.g., substring needle in index_of)
- Need header PHI (all iterations use same value)
- Do NOT need exit PHI (not a LoopState)
Implementation:
- Added `loop_invariants: Vec<(String, ValueId)>` field to JoinInlineBoundary
- Added `with_loop_invariants()` method to JoinInlineBoundaryBuilder
- Modified Pattern 6 to use loop_invariants instead of ConditionOnly misuse
* s (haystack) and ch (needle) now properly classified
* exit_bindings simplified to only LoopState carriers
- Extended LoopHeaderPhiBuilder to generate invariant PHIs
* Entry PHI: from host
* Latch PHI: self-reference (same value every iteration)
- Updated instruction_rewriter to handle invariant latch incoming
Files Modified:
- src/mir/join_ir/lowering/inline_boundary.rs (structure + builder)
- src/mir/join_ir/lowering/inline_boundary_builder.rs (builder method)
- src/mir/builder/control_flow/joinir/patterns/pattern6_scan_with_init.rs
- src/mir/builder/control_flow/joinir/merge/loop_header_phi_builder.rs
- src/mir/builder/control_flow/joinir/merge/mod.rs
- src/mir/builder/control_flow/joinir/merge/instruction_rewriter.rs
## Task B: Code Quality - var() Helper Unification
Created common module to eliminate var() duplication:
- New module: src/mir/builder/control_flow/joinir/patterns/common/
- Centralized var() helper in ast_helpers.rs
- Updated Pattern 6 and Pattern 2 to use common var()
- Test code (5 occurrences) deferred to Phase 256+ per 80/20 rule
Result: Eliminated 2 duplicate var() functions, 5 test occurrences remain
Files Created:
- src/mir/builder/control_flow/joinir/patterns/common/ast_helpers.rs
- src/mir/builder/control_flow/joinir/patterns/common/mod.rs
Files Modified:
- src/mir/builder/control_flow/joinir/patterns/mod.rs
- src/mir/builder/control_flow/joinir/patterns/pattern6_scan_with_init.rs
- src/mir/builder/control_flow/joinir/patterns/policies/balanced_depth_scan_policy.rs
## Task C: Documentation - PostLoopEarlyReturnPlan Usage Examples
Enhanced post_loop_early_return_plan.rs with:
- Architecture explanation (exit PHI usage prevents DCE)
- Pattern 2 example (Less: balanced_depth_scan)
- Pattern 6 example (NotEqual: index_of)
- Builder defer decision: when 4+ patterns emerge, add builder
Files Modified:
- src/mir/builder/control_flow/joinir/patterns/policies/post_loop_early_return_plan.rs
## Task D: Phase 256 Preparation
Analyzed next failure from smoke tests:
- `StringUtils.split/2` with variable-step loop
- Not constant step (i += len or similar)
- Three implementation options identified
Created Phase 256 README with:
- Minimal reproduction code
- Root cause analysis
- Implementation options with trade-offs
- Clear next steps
Files Created:
- docs/development/current/main/phases/phase-256/README.md
## Verification Results
✅ All tests passing:
- pattern254_p0_index_of_vm.sh: PASS
- No regression in Pattern 1-5
- Smoke test progresses past json_lint_vm to next failure
✅ Architecture achievements:
- Semantic clarity: loop_invariants vs exit_bindings properly separated
- ConditionOnly misuse eliminated
- PHI generation correct for all carrier types
- Code quality: var() duplication reduced
- Next phase clearly defined
## Summary
Phase 255 P2 achieves root-cause fix for multi-param loop support:
- Boundary concept expanded (loop_invariants field)
- Pattern 6 architecture corrected (no ConditionOnly misuse)
- Code quality improved (var() centralized)
- Next pattern (variable-step) is now the challenge
✨ Box-first principles maintained: clean separation, explicit roles, minimal coupling
🧠 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>
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2025-12-19 23:48:49 +09:00 |
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