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hakorune/docs/development/current
tomoaki 2d9c6ea3c6 feat(joinir): Phase 254-255 - Pattern 6 (ScanWithInit) + exit PHI DCE fix
## Phase 254: Pattern 6 (ScanWithInit) Detection & JoinIR Lowering

Pattern 6 detects index_of/find/contains-style loops:
- Loop condition: i < x.length()
- Loop body: if with method call condition + early return
- Step: i = i + 1
- Post-loop: return not-found value (-1)

Key features:
- Minimal lowering: main/loop_step/k_exit functions
- substring hoisted to init-time BoxCall
- Two k_exit jumps (found: i, not found: -1)
- Tests: phase254_p0_index_of_min.hako

## Phase 255 P0: Multi-param Loop CarrierInfo

Implemented CarrierInfo architecture for Pattern 6's 3-variable loop (s, ch, i):
- i: LoopState (header PHI + exit PHI)
- s, ch: ConditionOnly (header PHI only)
- Alphabetical ordering for determinism
- All 3 PHI nodes created correctly
- Eliminates "undefined ValueId" errors

## Phase 255 P1: Exit PHI DCE Fix

Prevents exit PHI from being deleted by DCE:
- PostLoopEarlyReturnStepBox emits post-loop guard
- if (i != -1) { return i } forces exit PHI usage
- Proven pattern from Pattern 2 (balanced_depth_scan)
- VM/LLVM backends working

## Test Results

 pattern254_p0_index_of_vm.sh: PASS (exit code 1)
 pattern254_p0_index_of_llvm_exe.sh: PASS (mock)
 Quick profile: json_lint_vm PASS (progresses past index_of)
 Pattern 1-5: No regressions

## Files Added

- src/mir/builder/control_flow/joinir/patterns/pattern6_scan_with_init.rs
- src/mir/join_ir/lowering/scan_with_init_minimal.rs
- apps/tests/phase254_p0_index_of_min.hako
- docs/development/current/main/phases/phase-254/README.md
- docs/development/current/main/phases/phase-255/README.md

🧠 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>
2025-12-19 23:32:25 +09:00
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