286 lines
8.4 KiB
Markdown
286 lines
8.4 KiB
Markdown
# Phase 56: Ownership-Relay Design
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## Overview
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「読むのは自由、管理は直下 owned だけ」アーキテクチャの設計文書。
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Phase 56 は **インターフェース設計のみ**。実装は Phase 57 以降。
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## Core Definitions
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### owned (所有)
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- 変数を定義したスコープが唯一の owner
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- Loop直下の `local x` → そのループが owned
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- body-local（if/block内の local）→ 最も内側の enclosing loop が owned
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**例**:
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```rust
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fn outer() {
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local a = 0 // owned by outer
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loop {
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local b = 0 // owned by this loop
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if cond {
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local c = 0 // owned by enclosing loop (not if!)
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}
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}
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}
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```
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### carriers (管理対象)
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- `carriers = writes ∩ owned`
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- そのスコープが定義 AND 更新する変数のみ
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- loop_step の引数として管理
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**重要**: Carrier は「所有 AND 更新」のみ。読み取り専用の owned 変数は carrier ではない。
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### captures (読み取り参照)
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- `captures = reads \ owned` (かつ carriers ではない)
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- 祖先スコープの変数への read-only アクセス
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- CapturedEnv / ConditionEnv 経由
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**例**:
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```rust
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local limit = 100
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loop {
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local sum = 0
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if sum < limit { // limit は capture (read-only)
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sum++ // sum は carrier (owned + written)
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}
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}
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```
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### relay (中継)
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- 内側スコープが祖先 owned を更新する場合
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- 更新責務を owner へ昇格（relay up）
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- 中間ループは引数として素通し
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**例**:
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```rust
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loop outer {
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local total = 0 // owned by outer
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loop inner {
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total++ // relay to outer (inner doesn't own total)
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}
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}
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// outer の exit PHI で total を merge
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```
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## Invariants (不変条件)
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1. **Ownership Uniqueness**: 各変数は唯一の owner を持つ
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2. **Carrier Locality**: carriers = writes ∩ owned (借用なし)
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3. **Relay Propagation**: writes \ owned → owner に昇格
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4. **Capture Read-Only**: captures は read-only (PHI 不要)
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## Shadowing Rules
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```nyash
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local x = 0 // outer owned
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loop {
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local x = 1 // inner owned (shadows outer)
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// 外の x は capture 可能だが、inner の x が優先
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print(x) // inner の x (1)
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}
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print(x) // outer の x (0)
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```
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- Shadowing = 新しい ownership 発生
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- 名前解決は最内スコープ優先
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- 外の x は capture として参照可能だが、内の x が存在する限り内が優先
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## Multi-Writer Merge
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```nyash
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loop outer {
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local total = 0
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if a { loop inner1 { total++ } } // relay to outer
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if b { loop inner2 { total-- } } // relay to outer
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}
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// outer の exit PHI で merge
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```
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- Relay は「更新意図の伝達」
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- 実際の PHI merge は owner 側で実行
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- 複数の内側ループが同じ変数を relay → owner の exit PHI で統合
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## JoinIR Mapping
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### Current System → New System
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| Current | New |
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|---------|-----|
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| CarrierInfo.carriers | OwnershipPlan.owned_vars (where is_written=true) |
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| promoted_loopbodylocals | (absorbed into owned analysis) |
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| CapturedEnv | OwnershipPlan.captures |
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| ConditionEnv | OwnershipPlan.condition_captures |
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| (implicit) | OwnershipPlan.relay_writes |
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### OwnershipPlan Structure
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```rust
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pub struct OwnershipPlan {
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pub scope_id: ScopeId,
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pub owned_vars: Vec<ScopeOwnedVar>, // All owned vars (carriers = is_written subset)
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pub relay_writes: Vec<RelayVar>,
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pub captures: Vec<CapturedVar>,
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pub condition_captures: Vec<CapturedVar>,
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}
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```
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**設計意図**:
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- `owned_vars`: このスコープが所有する変数（更新されるものは carriers）
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- `relay_writes`: 祖先の変数への書き込み（owner へ昇格）
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- `captures`: 祖先の変数への読み取り専用参照
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- `condition_captures`: captures のうち、条件式で使われるもの
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## Implementation Phases
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- **Phase 56**: Design + interface skeleton (this phase) ✅
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- **Phase 57**: OwnershipAnalyzer implementation (dev-only)
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- **Phase 58**: P2 plumbing (dev-only)
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- **Phase 59**: P3 plumbing (dev-only)
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- **Phase 60**: Single-hop relay threading for fixtures (dev-only)
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- **Phase 61**: P3 側の接続点を決めて段階接続（dev-only）
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- まずは fixtures ルート（Program(JSON v0)）で、if-sum+break を別箱として構造的に接続する
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- 詳細: `docs/development/current/main/PHASE_61_SUMMARY.md`
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- MIR→JoinIR の本番ルート（`pattern3_with_if_phi.rs`）へ寄せるのは別フェーズで設計→接続
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## Module Boundary
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`src/mir/join_ir/ownership/` - 責務は「解析のみ」
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**This module does**:
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- ✅ Collect reads/writes from AST/ProgramJSON
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- ✅ Determine variable ownership (owned/relay/capture)
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- ✅ Produce OwnershipPlan for downstream lowering
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**This module does NOT**:
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- ❌ Generate MIR instructions
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- ❌ Modify JoinIR structures
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- ❌ Perform lowering transformations
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Lowering/MIR生成は既存モジュールが担当。
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## Example Ownership Plans
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### Example 1: Simple Loop
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```nyash
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local sum = 0
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loop {
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sum++
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}
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```
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**OwnershipPlan (loop scope)**:
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- `owned_vars`: [`sum` (is_written=true)]
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- `relay_writes`: []
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- `captures`: []
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### Example 2: Nested Loop with Relay
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```nyash
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local total = 0
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loop outer {
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loop inner {
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total++
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}
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}
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```
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**OwnershipPlan (inner loop)**:
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- `owned_vars`: []
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- `relay_writes`: [`total` → relay to outer]
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- `captures`: []
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**OwnershipPlan (outer loop)**:
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- `owned_vars`: [`total` (is_written=true, via relay)]
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- `relay_writes`: []
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- `captures`: []
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### Example 3: Capture + Carrier
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```nyash
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local limit = 100
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loop {
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local sum = 0
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if sum < limit {
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sum++
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}
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}
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```
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**OwnershipPlan (loop scope)**:
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- `owned_vars`: [`sum` (is_written=true)]
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- `relay_writes`: []
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- `captures`: [`limit` (read-only)]
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- `condition_captures`: [`limit`]
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## References
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- **Phase 53-54**: Structural axis expansion
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- **Phase 43/245B**: Normalized JoinIR completion
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- **ChatGPT discussion**: 「読むのは自由、管理は直下だけ」設計
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- **JoinIR Architecture**: [joinir-architecture-overview.md](joinir-architecture-overview.md)
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## Phase 57: Algorithm Implementation
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### Analysis Steps
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1. **Scope Tree Construction**
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- Function/Loop/Block/If each get a ScopeId
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- Parent-child relationships tracked
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2. **Variable Collection (per scope)**
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- `defined`: Variables declared with `local` in this scope
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- `reads`: All variable reads (including nested)
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- `writes`: All variable writes (including nested)
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- `condition_reads`: Variables read in loop/if conditions
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3. **Ownership Assignment**
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- Body-local rule: `local` in if/block → enclosing Loop/Function owns it
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- `owned_vars` = variables defined in Loop/Function scopes
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4. **Plan Generation**
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- `carriers` = owned_vars where is_written=true
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- `relay_writes` = writes - owned (find owner in ancestors)
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- `captures` = reads - owned - writes (read-only)
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- `condition_captures` = captures ∩ condition_reads
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### Implementation Details
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**Input JSON Compatibility**:
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- テスト用の簡易スキーマ: top-level `functions` + stmt/expr の `kind` を解釈
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- Program(JSON v0): top-level `defs` + stmt/expr の `type` を解釈
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- `Local` は JSON v0 で「新規束縛」と「rebind/update」が混在し得るため、
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解析では「scope chain で既に定義済みなら write / 未定義なら define」として扱う（dev-only 前提）。
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- Note: `docs/private` は submodule のため、fixture JSON を参照する場合は submodule 側で追跡されていることを前提とする。
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**Body-Local Ownership Rule**:
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```rust
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// Example: local in if/block → enclosing loop owns it
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loop {
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if cond {
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local temp = 0 // owned by LOOP, not if!
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}
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}
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```
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**Relay Path Construction**:
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- Walk up ancestor chain to find owner
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- Collect only Loop scopes in relay_path (skip If/Block)
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- Inner loop → Outer loop → Function (relay chain)
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**Invariant Verification** (debug builds):
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- No variable in multiple categories (owned/relay/capture)
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- All relay_writes have valid owners
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- condition_captures ⊆ captures
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## Status
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- ✅ Phase 56: Design + interface skeleton completed
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- ✅ Phase 57: Analyzer implemented (dev-only)
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- ✅ Phase 58-59: plan_to_lowering helpers (P2/P3) with Fail-Fast relay
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- ✅ Phase 60 (dev-only): single-hop relay threading for P2 fixtures
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- `plan_to_p2_inputs_with_relay` promotes relay_writes to carriers (relay_path.len()<=1 only)
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- Frontend Break(P2) lowering uses ownership-with-relay; legacy path preserved for comparison
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- P3 stays analysis-only; real threading is Phase 61+
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