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tomoaki a2c5fd90fe feat(joinir): Phase 188.3 - Pattern6 (NestedLoopMinimal) 選択ロジック実装

## Phase 188.3 進捗: Phase 2 完了 (6/13 tasks)

### 実装完了 ✅

**Phase 1: Fixture作成**
- apps/tests/phase1883_nested_minimal.hako 追加
  - Add/Compare のみ（乗算なし）
  - 期待 exit code: 9 (3×3 nested loops)
- 既存 lowering で fallback 動作確認

**Phase 2: 選択ロジック (SSOT)**
- LoopPatternContext に step_tree_max_loop_depth フィールド追加
- choose_pattern_kind() に Pattern6 選択ロジック実装:
  1. Cheap check (has_inner_loop)
  2. StepTree 構築 (max_loop_depth 取得)
  3. AST validation (is_pattern6_lowerable)
- pattern6_nested_minimal.rs モジュール作成 (stub)
- LOOP_PATTERNS に Pattern6 entry 追加
- **検証**: Pattern6 が正しく選択される ✅

### 設計原則 (確認済み)

1. **Fail-Fast**: Pattern6 選択後は Ok(None) で逃げない
2. **outer 変数 write-back 検出 → validation false** (Phase 188.4+)
3. **最小実装**: inner local だけ、Pattern1 モデル二重化
4. **cfg! 依存なし**: production で動作

### 検証結果

```
[choose_pattern_kind] has_inner_loop=true
[choose_pattern_kind] max_loop_depth=2
[choose_pattern_kind] is_pattern6_lowerable=true
✅ Pattern6 SELECTED!
```

Stub からの期待エラー:
```
[ERROR] ❌ [Pattern6] Nested loop lowering not yet implemented
```

### 次: Phase 3 (Lowering 実装 - 推定4時間)

残りタスク:
- Phase 3-1: AST 抽出ヘルパー
- Phase 3-2: Validation ヘルパー
- Phase 3-3: Continuation 生成 (outer_step, inner_step, k_inner_exit)
- Phase 3-4: fixture が exit=9 を返すことを検証

### 変更ファイル

**新規**:
- apps/tests/phase1883_nested_minimal.hako
- src/mir/builder/control_flow/joinir/patterns/pattern6_nested_minimal.rs
- docs/development/current/main/phases/phase-188.{1,2,3}/README.md

**変更**:
- src/mir/builder/control_flow/joinir/routing.rs (Pattern6 選択)
- src/mir/builder/control_flow/joinir/patterns/router.rs (Context 拡張)
- src/mir/builder/control_flow/joinir/patterns/mod.rs (module 宣言)

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

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

2025-12-27 05:45:12 +09:00

4.1 KiB

Raw Blame History

Phase 188.2: StepTree nesting depth SSOT (Option A) — strict Fail-Fast

Date: 2025-12-27 Status: ✅ Option A implemented / ❌ Pattern 6 lowering deferred (Phase 188.3+) Goal: StepTreeFeatures.max_loop_depth を SSOT として、strict mode で depth > 2 を明示エラーにする

✅ Decision: Option A Adopted (2025-12-27)

Chosen Approach: StepTreeFeatures Integration

What Phase 188.2 Implements:

Use StepTree.features.max_loop_depth as SSOT for nesting depth
Add explicit error for max_loop_depth > 2 in strict mode (capability_guard.rs)
Update NestedLoop capability hint to reflect current support

Implementation Location:

src/mir/builder/control_flow/joinir/control_tree_capability_guard.rs (lines 32-76)

Status: Option A depth checking implemented, Option B deferred

What Phase 188.2 delivered

✅ strict mode の depth 制約を SSOT 化（max_loop_depth > 2 は明示エラー）
✅ NestedLoop capability hint を現実に合わせて更新（1-levelは許可、2+ level は depth_exceeded）
✅ unit tests 更新（depth=2 PASS / depth=3 FAIL）
✅ quick/integration は不変（回帰なし）

Verification (reference)

quick: ./tools/smokes/v2/run.sh --profile quick
integration selfhost: ./tools/smokes/v2/run.sh --profile integration --filter "selfhost_"

Background

Phase 188.1 delivered infrastructure (capability allowlist, enum, stub module), but detection and lowering are NOT implemented due to architectural limitations.

See: docs/development/current/main/phases/phase-188.1/README.md § Implementation Reality

Design Decision Required (Choose A or B)

Option A: StepTreeFeatures Integration

Approach:

Pass StepTreeFeatures from StepTree to LoopForm creation
Store max_loop_depth in LoopForm (add field) or pass via context
Use AST-level nesting depth for Pattern 6 detection

Pros:

Nesting info already exists in StepTree
No new detection logic required
Fast implementation

Cons:

AST-level info may diverge from MIR structure (after optimizations)
Adding fields to LoopForm breaks separation of concerns

Estimated Effort: 1-2 days

Option B: LoopRegion Integration

Approach:

Implement LoopRegion builder (instantiate parent/child structure)
Build LoopRegion tree from MIR control flow graph
Compute nesting depth from LoopRegion.parent traversal
Replace LoopForm with LoopRegion in lowering pipeline

Pros:

MIR-level truth (accurate after optimizations)
Leverages Phase 32 infrastructure
Clean separation (LoopRegion is designed for nesting)

Cons:

Requires implementing LoopRegion builder (non-trivial)
Larger architectural change
May affect other loop analysis code

Estimated Effort: 1-2 weeks

Planning Session Agenda

Step 1: Docs-First Design Review

Review Option A vs B trade-offs
Consider impact on selfhost_minimal requirements
Decide on approach based on scope/timeline

Step 2: Detailed Implementation Plan

Write step-by-step implementation guide
Identify critical files
Estimate effort per task

Step 3: Implementation

Execute chosen approach
Test with selfhost_minimal
Verify 154/154 PASS maintained

Out of Scope (Phase 188.2)

Still deferred to Phase 188.3+:

Break/continue in nested loops (Pattern 2/4 combinations)
Multiple inner loops (siblings)
2+ level nesting (depth > 2) の lowering（Phase 188.2 は strict Fail-Fast のみ）

Rationale: Phase 188.2 focuses on 1-level nesting detection only (minimal scope).

References

Phase 188.1 Reality: docs/development/current/main/phases/phase-188.1/README.md § Implementation Reality
LoopRegion Definition: src/mir/control_form.rs (lines 40-62)
StepTreeFeatures Definition: src/mir/control_tree/step_tree.rs (lines 17-25)
LoopForm/LoopShape Definition: src/mir/loop_form.rs, src/mir/control_form.rs

End of Phase 188.2 Planning Stub

Status: Option A is complete; remaining work is Phase 188.3+ Dependencies: Phase 188.1 “Implementation Reality” remains SSOT

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