docs(llvm/vm): 静的Box(self)規約を明文化 + Bridgeトグル追記; Gate‑C/Core 現状反映; CURRENT_TASK 更新。\n\n- 新規: docs/development/architecture/llvm/static_box_singleton.md\n- 追記: lang/src/vm/README.md に self 先頭規約/互換トグルを明記\n- 追記: CURRENT_TASK に本更新を記録\n- phase-20.33/CHECKLIST にドキュメント完了チェックを追加\n- bak フォルダはリポジトリ直下に存在せず（削除対象なし）\n\n併せて未コミット差分をスナップショット（Rust 層の前作業含む）

src/mir/loop_builder.rs

@@ -306,7 +306,15 @@ impl<'a> LoopBuilder<'a> {
         header_id: BasicBlockId,
         preheader_id: BasicBlockId,
     ) -> Result<(), String> {
+        use std::sync::atomic::{AtomicUsize, Ordering};
+        static CALL_COUNT: AtomicUsize = AtomicUsize::new(0);
+        let count = CALL_COUNT.fetch_add(1, Ordering::SeqCst);
+
         let current_vars = self.get_current_variable_map();
+        // Debug: print current_vars before prepare
+        eprintln!("[DEBUG] prepare_loop_variables call #{}", count);
+        eprintln!("[DEBUG]   current_vars = {:?}", current_vars);
+        eprintln!("[DEBUG]   preheader_id = {:?}, header_id = {:?}", preheader_id, header_id);
         crate::mir::phi_core::loop_phi::save_block_snapshot(
             &mut self.block_var_maps,
             preheader_id,
@@ -409,17 +417,34 @@ impl<'a> LoopBuilder<'a> {
         dst: ValueId,
         inputs: Vec<(BasicBlockId, ValueId)>,
     ) -> Result<(), String> {
+        eprintln!("[DEBUG] LoopBuilder::emit_phi_at_block_start: block={}, dst=%{}, inputs={:?}", block_id, dst.0, inputs);
         // Phi nodeをブロックの先頭に挿入
         if let Some(ref mut function) = self.parent_builder.current_function {
             if let Some(block) = function.get_block_mut(block_id) {
+                eprintln!("[DEBUG]   Block {} current instructions count: {}", block_id, block.instructions.len());
                 // Phi命令は必ずブロックの先頭に配置
-                let phi_inst = MirInstruction::Phi { dst, inputs };
+                let phi_inst = MirInstruction::Phi { dst, inputs: inputs.clone() };
                 block.instructions.insert(0, phi_inst);
+                eprintln!("[DEBUG]   ✅ PHI instruction inserted at position 0");
+                eprintln!("[DEBUG]   Block {} after insert instructions count: {}", block_id, block.instructions.len());
+                // Verify PHI is still there
+                if let Some(first_inst) = block.instructions.get(0) {
+                    match first_inst {
+                        MirInstruction::Phi { dst: phi_dst, .. } => {
+                            eprintln!("[DEBUG]   Verified: First instruction is PHI dst=%{}", phi_dst.0);
+                        }
+                        other => {
+                            eprintln!("[DEBUG]   ⚠️  WARNING: First instruction is NOT PHI! It's {:?}", other);
+                        }
+                    }
+                }
                 Ok(())
             } else {
+                eprintln!("[DEBUG]   ❌ Block {} not found!", block_id);
                 Err(format!("Block {} not found", block_id))
             }
         } else {
+            eprintln!("[DEBUG]   ❌ No current function!");
             Err("No current function".to_string())
         }
     }
@@ -465,6 +490,7 @@ impl<'a> LoopBuilder<'a> {
     }
 
     fn update_variable(&mut self, name: String, value: ValueId) {
+        eprintln!("[DEBUG] LoopBuilder::update_variable: name={}, value=%{}", name, value.0);
         self.parent_builder.variable_map.insert(name, value);
     }
 
@@ -716,4 +742,26 @@ impl crate::mir::phi_core::loop_phi::LoopPhiOps for LoopBuilder<'_> {
             crate::mir::phi_core::common::debug_verify_phi_inputs(func, merge_bb, inputs);
         }
     }
+
+    fn emit_copy_at_preheader(
+        &mut self,
+        preheader_id: BasicBlockId,
+        dst: ValueId,
+        src: ValueId,
+    ) -> Result<(), String> {
+        eprintln!("[DEBUG] emit_copy_at_preheader: preheader={}, dst=%{}, src=%{}", preheader_id, dst.0, src.0);
+        if let Some(ref mut function) = self.parent_builder.current_function {
+            if let Some(block) = function.get_block_mut(preheader_id) {
+                eprintln!("[DEBUG]   Adding Copy instruction to block {}", preheader_id);
+                block.add_instruction(MirInstruction::Copy { dst, src });
+                Ok(())
+            } else {
+                eprintln!("[DEBUG]   ❌ Preheader block {} not found!", preheader_id);
+                Err(format!("Preheader block {} not found", preheader_id))
+            }
+        } else {
+            eprintln!("[DEBUG]   ❌ No current function!");
+            Err("No current function".to_string())
+        }
+    }
 }