feat(llvm): Phase 131-11-H/12 - ループキャリアPHI型修正 & vmap snapshot SSOT

## Phase 131-11-H: ループキャリアPHI型修正
- PHI生成時に初期値（entry block）の型のみ使用
- backedge の値を型推論に使わない（循環依存回避）
- NYASH_CARRIER_PHI_DEBUG=1 でトレース

## Phase 131-12-P0: def_blocks 登録 & STRICT エラー化
- safe_vmap_write() で PHI 上書き保護
- resolver miss を STRICT でエラー化（フォールバック 0 禁止）
- def_blocks 自動登録

## Phase 131-12-P1: vmap_cur スナップショット実装
- DeferredTerminator 構造体（block, term_ops, vmap_snapshot）
- Pass A で vmap_cur をスナップショット
- Pass C でスナップショット復元（try-finally）
- STRICT モード assert

## 結果
- ✅ MIR PHI型: Integer（正しい）
- ✅ VM: Result: 3
- ✅ vmap snapshot 機構: 動作確認
- ⚠️ LLVM: Result: 0（別のバグ、次Phase で調査）

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

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

src/llvm_py/builders/block_lower.py

@@ -1,9 +1,20 @@
-from typing import Dict, Any, List, Tuple
+from typing import Dict, Any, List, Tuple, NamedTuple
 from llvmlite import ir
 from trace import debug as trace_debug
 from trace import phi_json as trace_phi_json
 
 
+class DeferredTerminator(NamedTuple):
+    """Phase 131-12-P1: Deferred terminator with vmap snapshot.
+
+    This structure captures the terminator operations along with the vmap state
+    at the end of Pass A, ensuring Pass C uses the correct SSA context.
+    """
+    bb: ir.Block
+    term_ops: List[Dict[str, Any]]
+    vmap_snapshot: Dict[int, ir.Value]
+
+
 def lower_blocks(builder, func: ir.Function, block_by_id: Dict[int, Dict[str, Any]], order: List[int], loop_plan: Dict[str, Any] | None):
     """Lower blocks in multi-pass to ensure PHIs are always before terminators.
 
@@ -34,6 +45,8 @@ def lower_blocks(builder, func: ir.Function, block_by_id: Dict[int, Dict[str, An
             try:
                 builder.resolver.builder = ib
                 builder.resolver.module = builder.module
+                # P0-1: Set current block_id for def_blocks tracking
+                builder.resolver.current_block_id = bid
             except Exception:
                 pass
             builder.loop_count += 1
@@ -116,6 +129,8 @@ def lower_blocks(builder, func: ir.Function, block_by_id: Dict[int, Dict[str, An
         try:
             builder.resolver.builder = ib
             builder.resolver.module = builder.module
+            # P0-1: Set current block_id for def_blocks tracking
+            builder.resolver.current_block_id = bid
         except Exception:
             pass
         block_data = block_by_id.get(bid, {})
@@ -162,6 +177,10 @@ def lower_blocks(builder, func: ir.Function, block_by_id: Dict[int, Dict[str, An
         except Exception:
             vmap_cur = dict(builder.vmap)
         builder._current_vmap = vmap_cur
+        # Phase 131-12-P1: Object identity trace for vmap_cur investigation
+        import os, sys
+        if os.environ.get('NYASH_LLVM_VMAP_TRACE') == '1':
+            print(f"[vmap/id] bb{bid} vmap_cur id={id(vmap_cur)} keys={sorted(vmap_cur.keys())[:10]}", file=sys.stderr)
         created_ids: List[int] = []
         defined_here_all: set = set()
         for _inst in body_ops:
@@ -229,11 +248,17 @@ def lower_blocks(builder, func: ir.Function, block_by_id: Dict[int, Dict[str, An
             except Exception:
                 pass
         # Phase 131-4 Pass A: DEFER terminators until after PHI finalization
-        # Store terminators for Pass C (will be lowered in lower_terminators)
+        # Phase 131-12-P1 P0-2: Store terminators WITH vmap_cur snapshot for Pass C
         if not hasattr(builder, '_deferred_terminators'):
             builder._deferred_terminators = {}
         if term_ops:
-            builder._deferred_terminators[bid] = (bb, term_ops)
+            # CRITICAL: dict(vmap_cur) creates a snapshot copy to prevent mutation issues
+            vmap_snapshot = dict(vmap_cur)
+            builder._deferred_terminators[bid] = DeferredTerminator(bb, term_ops, vmap_snapshot)
+            # Phase 131-12-P1: Trace snapshot creation
+            import os, sys
+            if os.environ.get('NYASH_LLVM_VMAP_TRACE') == '1':
+                print(f"[vmap/id] Pass A bb{bid} snapshot id={id(vmap_snapshot)} keys={sorted(vmap_snapshot.keys())[:10]}", file=sys.stderr)
         # Phase 131-7: Sync ALL created values to global vmap (not just PHIs)
         # This ensures Pass C (deferred terminators) can access values from Pass A
         try:
@@ -265,9 +290,11 @@ def lower_blocks(builder, func: ir.Function, block_by_id: Dict[int, Dict[str, An
 
 def lower_terminators(builder, func: ir.Function):
     """Phase 131-4 Pass C: Lower deferred terminators after PHI finalization.
+    Phase 131-12-P1 P0-3: Restore vmap_cur snapshot for each block's terminator lowering.
 
     This ensures PHI nodes are always at block heads before terminators are added,
     maintaining LLVM IR's invariant: PHIs first, then other instructions, then terminators.
+    The vmap snapshot ensures terminators see the SSA context from Pass A, not later mutations.
     """
     if not hasattr(builder, '_deferred_terminators'):
         return
@@ -275,31 +302,65 @@ def lower_terminators(builder, func: ir.Function):
     deferred = builder._deferred_terminators
     trace_debug(f"[llvm-py/pass-c] Lowering {len(deferred)} blocks with deferred terminators")
 
-    for bid, (bb, term_ops) in deferred.items():
-        ib = ir.IRBuilder(bb)
-        try:
-            builder.resolver.builder = ib
-            builder.resolver.module = builder.module
-            # Phase 131-4: Disable PHI synthesis during terminator lowering
-            # Terminators should only use values that already exist (from Pass A/B)
-            builder.resolver._disable_phi_synthesis = True
-        except Exception:
-            pass
+    import os, sys
+    strict_mode = os.environ.get('NYASH_LLVM_STRICT') == '1'
 
-        for inst in term_ops:
+    for bid, deferred_term in deferred.items():
+        # Phase 131-12-P1: Unpack DeferredTerminator with vmap snapshot
+        bb = deferred_term.bb
+        term_ops = deferred_term.term_ops
+        vmap_snapshot = deferred_term.vmap_snapshot
+
+        # Phase 131-12-P1 P0-4: STRICT mode assertion
+        if strict_mode:
+            assert vmap_snapshot is not None, f"STRICT: vmap_snapshot must exist for bb{bid}"
+            trace_debug(f"[llvm-py/pass-c/strict] bb{bid} vmap_snapshot id={id(vmap_snapshot)}")
+
+        # Phase 131-12-P1 P0-3: Save and restore _current_vmap
+        old_current_vmap = getattr(builder, '_current_vmap', None)
+        builder._current_vmap = vmap_snapshot
+
+        # Trace snapshot restoration
+        if os.environ.get('NYASH_LLVM_VMAP_TRACE') == '1':
+            print(f"[vmap/id] Pass C bb{bid} restored snapshot id={id(vmap_snapshot)} keys={sorted(vmap_snapshot.keys())[:10]}", file=sys.stderr)
+
+        # Phase 131-12-P1 P0-4: STRICT mode verification
+        if strict_mode:
+            assert hasattr(builder, '_current_vmap'), f"STRICT: _current_vmap must be set for bb{bid} terminator lowering"
+            assert id(builder._current_vmap) == id(vmap_snapshot), f"STRICT: _current_vmap must match snapshot for bb{bid}"
+
+        try:
+            ib = ir.IRBuilder(bb)
             try:
-                trace_debug(f"[llvm-py/pass-c] term op: {inst.get('op')} dst={inst.get('dst')} in bb{bid}")
+                builder.resolver.builder = ib
+                builder.resolver.module = builder.module
+                # Phase 131-4: Disable PHI synthesis during terminator lowering
+                # Terminators should only use values that already exist (from Pass A/B)
+                builder.resolver._disable_phi_synthesis = True
             except Exception:
                 pass
-            try:
-                if bb.terminator is not None:
-                    # Terminator already exists (e.g., from loop lowering), skip
-                    trace_debug(f"[llvm-py/pass-c] bb{bid} already has terminator, skipping")
-                    break
-            except Exception:
-                pass
-            ib.position_at_end(bb)
-            builder.lower_instruction(ib, inst, func)
+
+            for inst in term_ops:
+                try:
+                    trace_debug(f"[llvm-py/pass-c] term op: {inst.get('op')} dst={inst.get('dst')} in bb{bid}")
+                except Exception:
+                    pass
+                try:
+                    if bb.terminator is not None:
+                        # Terminator already exists (e.g., from loop lowering), skip
+                        trace_debug(f"[llvm-py/pass-c] bb{bid} already has terminator, skipping")
+                        break
+                except Exception:
+                    pass
+                ib.position_at_end(bb)
+                builder.lower_instruction(ib, inst, func)
+        finally:
+            # Phase 131-12-P1 P0-3: Restore previous _current_vmap state (prevent side effects)
+            if old_current_vmap is None:
+                if hasattr(builder, '_current_vmap'):
+                    delattr(builder, '_current_vmap')
+            else:
+                builder._current_vmap = old_current_vmap
 
     # Clean up deferred state
     try:

src/llvm_py/builders/instruction_lower.py

@@ -31,6 +31,10 @@ def lower_instruction(owner, builder: ir.IRBuilder, inst: Dict[str, Any], func:
     op = inst.get("op")
     # Pick current vmap context (per-block context during lowering)
     vmap_ctx = getattr(owner, '_current_vmap', owner.vmap)
+    # Phase 131-12-P1: Object identity trace for vmap_ctx investigation
+    import os, sys
+    if os.environ.get('NYASH_LLVM_VMAP_TRACE') == '1':
+        print(f"[vmap/id] instruction op={op} vmap_ctx id={id(vmap_ctx)}", file=sys.stderr)
 
     if op == "const":
         dst = inst.get("dst")