hakorune/MIR13_MODE.md at f0608e9bb1ee7539fa541f5f7c726e1c484984ad

Files

Selfhosting Dev f0608e9bb1 feat: Phase 2.4 レガシーアーカイブ整理完了（151MB削減）

## 🎉 完了項目
- ✅ plugin_box_legacy.rs削除（7.7KB、参照ゼロ確認済み）
- ✅ REMOVEDコメント整理（encode.rs簡潔化）
- ✅ venv削除（143MB節約、.gitignoreは既存）
- ✅ llvm_legacyスタブ化（8KB、compile_error!による安全化）

## 🏆 成果
- **リポジトリサイズ改善**: 151MB削減
- **コード整理**: レガシーコード安全にアーカイブ
- **プラグインファースト**: StrictPluginFirst継続動作

## ✅ 検証完了
- cargo build --release --features llvm (警告のみ、エラーなし)
- LLVMハーネス実行: print出力正常
- プラグイン動作: StringBox等正常動作

codex先生の戦略に従った安全な段階的削除を実行

Co-Authored-By: codex <noreply@anthropic.com>

2025-09-24 14:13:15 +09:00

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MIR13 Mode (legacy PHI-off fallback)

Overview

Goal: Retain the Phase‑14 edge-copy compatibility path for debugging historical MIR dumps or diagnosing SSA regressions.
Default: MIR14 (PHI-on) now ships as the standard. MIR13 must be explicitly enabled through environment flags.

Why keep MIR13 around?

Reproducibility: Some archived JSON v0 fixtures were captured before PHI-on shipped. MIR13 allows replaying them without regeneration.
Diagnostics: Edge-copy runs make it easier to isolate builder regressions by removing PHI synthesis from the equation.
Tooling parity: Certain scripts still compare MIR13 traces; they will be retired once PHI-on parity checks are complete.

Flags and Behavior

NYASH_MIR_NO_PHI (default: 0)
- 0: Builders emit PHIs at merge heads (MIR14, default).
- 1: Builders drop PHIs and insert per-predecessor edge copies (MIR13 fallback).
NYASH_VERIFY_ALLOW_NO_PHI (default: 0 unless PHI-off is requested)
- Set this to 1 together with NYASH_MIR_NO_PHI=1 when you intentionally relax SSA verification.
NYASH_LLVM_USE_HARNESS=1 (AOT via llvmlite harness)
- In MIR13 mode the harness synthesizes PHIs. In MIR14 it simply validates incoming edges.

LLVM (llvmlite) Responsibilities

setup_phi_placeholders(): still records declared PHIs; in MIR13 mode it creates placeholders for later wiring.
block_end_values: snapshots per block end to materialize predecessor values (dominance-safe).
finalize_phis(): wires incoming edges for declared PHIs; when MIR13 runs, it creates PHIs on the fly to recover SSA.
Resolver.resolve_i64():
- single-pred: take predecessor end value;
- multi-pred + declared PHI: reuse the placeholder at the block head;
- multi-pred + no PHI: synthesize a localization PHI at the current block head (MIR13 compatibility);
- avoids reusing non-dominating vmap values across blocks.

Bridge/Builder (JSON v0) Behavior

MIR14 (default): If/Loop/Try placements emit PHIs up front; loop latches, break/continue, and structured joins have explicit incoming pairs.
MIR13 (fallback): Merges are performed with edge copies (merge_var_maps). Use only when reproducing historical issues.

Testing

Curated LLVM (default = PHI-on):
- tools/smokes/curated_llvm.sh (add --phi-off to exercise MIR13)
PHI invariants/parity (AOT vs PyVM):
- tools/pyvm_vs_llvmlite.sh (default compares exit code; use CMP_STRICT=1 for stdout+exit)
Bridge/PyVM:
- tools/selfhost_stage2_bridge_smoke.sh

How to Force PHI-off (MIR13 fallback)

Set: NYASH_MIR_NO_PHI=1 NYASH_VERIFY_ALLOW_NO_PHI=1 and run tools/smokes/curated_llvm.sh --phi-off
Label the run as legacy in CURRENT_TASK.md if results inform shared debugging.

Known Limitations (current)

MIR13 no longer receives new feature work; expect missing coverage for recent LoopForm updates.
PHI-on is the supported path. MIR13 bugs are fixed only when they block diagnostics.

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