feat(phase21.5): Stage-B parser loop fix + delegate path stabilization
## 修正内容 ### 1. Stage-B パーサー修正（偶然の回避） - **ファイル**: - `lang/src/compiler/parser/expr/parser_expr_box.hako` - `lang/src/compiler/parser/stmt/parser_control_box.hako` - **問題**: ネストループで gpos が正しく進まず、loop の cond/body が壊れる - **回避策**: new 式のメソッドチェーン処理追加で別ループを導入 - **結果**: MIR 生成が変わって VM gpos バグを回避 ### 2. delegate パス動作確認 - **テスト**: `/tmp/loop_min.hako` → rc=10 ✅ - **MIR構造**: 正しい PHI/compare/binop を生成 - **チェーン**: hakorune parser → Rust delegate → LLVM EXE 完動 ### 3. ドキュメント追加 - `docs/development/analysis/` - delegate 分析 - `docs/development/guides/` - ループテストガイド - `docs/development/testing/` - Stage-B 検証報告 ### 4. カナリーテスト追加 - `tools/smokes/v2/profiles/quick/core/phase2100/` 配下に複数追加 - emit_boxcall_length_canary_vm.sh - stageb_parser_loop_json_canary_vm.sh - 他 ### 受け入れ基準 - ✅ delegate パス: rc=10 返す - ✅ FORCE パス: rc=10 返す（既存） - ✅ MIR 構造: 正しい PHI incoming と compare - ✅ 既定挙動: 不変（dev トグルのみ） 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>
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nyash-codex
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docs/development/analysis/delegate_loop_lowering_analysis.md
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docs/development/analysis/delegate_loop_lowering_analysis.md
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# Delegate Loop Lowering Analysis
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## Executive Summary
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**Root Cause**: The delegate path loop lowering issue is **NOT** a bug in the Rust lowering code (`src/runner/json_v0_bridge/lowering/loop_.rs`). The actual problem is in the **Stage-B self-hosting compiler** (`lang/src/compiler/entry/compiler_stageb.hako` and `lang/src/compiler/parser/parser_box.hako`) which produces malformed Program JSON v0.
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**Status**: The Rust delegate lowering code is correct. The Stage-B parser is producing incorrect output.
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## Problem Description
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### Test Case
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```hako
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static box Main { method main(){
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local n=10; local i=0;
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loop(i<n){ i=i+1 }
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return i
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} }
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```
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**Expected**: Returns 10
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**Actual (delegate)**: Returns 0
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**Actual (FORCE)**: Returns 10 ✅
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## Investigation Findings
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### 1. Malformed Program JSON v0
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The Stage-B compiler produces this Program JSON:
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```json
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{
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"body": [
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{"type":"Local","name":"n","expr":{"type":"Int","value":10}},
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{"type":"Local","name":"i","expr":{"type":"Int","value":0}},
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{"type":"Loop","cond":{"type":"Compare","op":"<","lhs":{"type":"Var","name":"i"},"rhs":{"type":"Int","value":0}},"body":[]},
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...
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]
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}
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```
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**Two Critical Bugs**:
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1. **Empty loop body**: `"body":[]` instead of `[{"type":"Local","name":"i","expr":{"type":"Binary",...}}]`
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2. **Wrong condition**: Compares `i < 0` instead of `i < n` (rhs is `{"type":"Int","value":0}` instead of `{"type":"Var","name":"n"}`)
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### 2. Delegate MIR Structure (Incorrect)
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The delegate path produces this MIR:
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**Block 1 (Header)**:
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```json
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{
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"op": "phi", "dst": 3, "incoming": [[2,0],[2,2]] // Wrong: both from reg 2
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},
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{
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"op": "phi", "dst": 5, "incoming": [[4,0],[4,2]] // Wrong: both from reg 4
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},
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{
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"op": "compare", "operation": "<", "lhs": 5, "rhs": 6 // Wrong: compares i < 0
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}
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```
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**Block 2 (Body)**:
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```json
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{
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"op": "jump", "target": 1 // Empty body - no i=i+1!
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}
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```
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### 3. FORCE MIR Structure (Correct)
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The FORCE path (using selfhost-first with JsonFrag) produces correct MIR:
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**Block 1 (Header)**:
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```json
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{
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"op": "phi", "dst": 6, "incoming": [[2,0],[6,2]] // Correct: n from preheader/itself
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},
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{
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"op": "phi", "dst": 3, "incoming": [[1,0],[5,2]] // Correct: i from 0/updated
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},
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{
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"op": "compare", "operation": "<", "lhs": 3, "rhs": 6 // Correct: i < n
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}
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```
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**Block 2 (Body)**:
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```json
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{
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"op": "const", "dst": 10, "value": {"type":"i64","value":1}
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},
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{
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"op": "binop", "operation": "+", "lhs": 3, "rhs": 10, "dst": 5 // Correct: i+1
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},
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{
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"op": "jump", "target": 1
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}
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```
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## Rust Delegate Lowering Code Analysis
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The Rust lowering code in `src/runner/json_v0_bridge/lowering/loop_.rs` is **CORRECT**:
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1. **Line 109-111**: Correctly prepares loop PHIs with preheader seeds
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2. **Line 115-116**: Correctly lowers condition and sets up branch
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3. **Line 117-123**: Correctly clones vars and lowers body
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4. **Line 133**: Correctly saves `body_vars` after body execution
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5. **Line 145-152**: Correctly seals PHIs with latch values
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The code correctly implements:
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- PHI preparation with preheader copies
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- Body variable tracking
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- PHI sealing with latch values
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- Exit PHI generation
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**The problem is garbage-in, garbage-out**: When the Program JSON has an empty body and wrong condition, the lowering correctly processes that incorrect input.
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## Verification
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### Test Results
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**FORCE Path** (✅ Works):
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```bash
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HAKO_SELFHOST_BUILDER_FIRST=1 \
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HAKO_MIR_BUILDER_LOOP_FORCE_JSONFRAG=1 \
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bash tools/hakorune_emit_mir.sh /tmp/loop_min.hako /tmp/loop_min_force.json
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# Result: MIR with correct structure, EXE returns 10
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```
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**Delegate Path** (❌ Broken):
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```bash
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NYASH_JSON_ONLY=1 \
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bash tools/hakorune_emit_mir.sh /tmp/loop_min.hako /tmp/loop_min_delegate.json
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# Result: MIR with empty body and wrong condition, EXE returns 0
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```
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## Root Cause Location
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The bug is in the **Stage-B self-hosting compiler**:
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**Entry Point**: `lang/src/compiler/entry/compiler_stageb.hako` line 341
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```hako
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local ast_json = p.parse_program2(body_src)
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```
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**Parser**: `lang/src/compiler/parser/parser_box.hako`
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- Likely in loop parsing logic
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- Incorrectly handles loop body extraction
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- Incorrectly handles loop condition parsing
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## Recommendations
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### Short-Term (Immediate)
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1. **Use FORCE path for production**:
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```bash
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export HAKO_SELFHOST_BUILDER_FIRST=1
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export HAKO_MIR_BUILDER_LOOP_FORCE_JSONFRAG=1
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```
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2. **Document delegate path limitation**:
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- Add warning in tools/hakorune_emit_mir.sh
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- Update phase documentation
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### Medium-Term (Fix)
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1. **Debug Stage-B parser**:
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- Add instrumentation to `parser_box.hako`
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- Trace loop parsing logic
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- Fix body extraction and condition parsing
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2. **Add Stage-B tests**:
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- Create test suite for Program JSON v0 output
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- Include loop test cases
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- Verify against expected JSON structure
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### Long-Term (Architecture)
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1. **Phase out Stage-B for critical paths**:
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- Keep FORCE path as primary
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- Use delegate only for verified constructs
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- Consider Rust-based parser for reliability
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2. **Improve JsonFrag robustness**:
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- The FORCE path already works correctly
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- Focus optimization efforts there
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## Conclusion
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**The delegate loop lowering code is correct**. The bug is upstream in the Stage-B self-hosting compiler which produces malformed Program JSON v0. The FORCE path works because it bypasses the buggy Stage-B parser and uses the JsonFrag-based MirBuilder implementation.
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**Immediate Action**: Use FORCE path (`HAKO_SELFHOST_BUILDER_FIRST=1`) for all loop-related development and testing until the Stage-B parser is fixed.
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## Files Analyzed
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- ✅ `src/runner/json_v0_bridge/lowering/loop_.rs` - Correct implementation
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- ✅ `src/mir/phi_core/loop_phi.rs` - Correct PHI management
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- ❌ `lang/src/compiler/entry/compiler_stageb.hako` - Calls buggy parser
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- ❌ `lang/src/compiler/parser/parser_box.hako` - Contains loop parsing bug
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- ✅ `tools/hakorune_emit_mir.sh` - Script wrapper (works as designed)
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---
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**Date**: 2025-11-11
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**Analyst**: Claude (Sonnet 4.5)
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**Context**: Phase 21.5 Delegate Loop Lowering Investigation
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