337 lines
12 KiB
Rust
337 lines
12 KiB
Rust
/*!
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* MIR Loop Builder - SSA形式でのループ構築専用モジュール
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*
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* Sealed/Unsealed blockとPhi nodeを使った正しいループ実装
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* Based on Gemini's recommendation for proper SSA loop handling
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*/
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use super::{
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MirInstruction, BasicBlockId, ValueId,
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ConstValue
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};
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use crate::ast::ASTNode;
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use std::collections::HashMap;
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/// 不完全なPhi nodeの情報
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#[derive(Debug, Clone)]
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struct IncompletePhi {
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/// Phi nodeの結果ValueId
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phi_id: ValueId,
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/// 変数名
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var_name: String,
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/// 既知の入力値 (predecessor block id, value)
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known_inputs: Vec<(BasicBlockId, ValueId)>,
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}
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/// ループビルダー - SSA形式でのループ構築を管理
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pub struct LoopBuilder<'a> {
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/// 親のMIRビルダーへの参照
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parent_builder: &'a mut super::builder::MirBuilder,
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/// ループ内で追跡する変数の不完全Phi node
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incomplete_phis: HashMap<BasicBlockId, Vec<IncompletePhi>>,
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/// ブロックごとの変数マップ（スコープ管理）
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#[allow(dead_code)]
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block_var_maps: HashMap<BasicBlockId, HashMap<String, ValueId>>,
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/// ループヘッダーID（continueで使用）
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loop_header: Option<BasicBlockId>,
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/// continue文からの変数スナップショット
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continue_snapshots: Vec<(BasicBlockId, HashMap<String, ValueId>)>,
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}
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impl<'a> LoopBuilder<'a> {
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/// 新しいループビルダーを作成
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pub fn new(parent: &'a mut super::builder::MirBuilder) -> Self {
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Self {
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parent_builder: parent,
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incomplete_phis: HashMap::new(),
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block_var_maps: HashMap::new(),
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loop_header: None,
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continue_snapshots: Vec::new(),
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}
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}
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/// SSA形式でループを構築
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pub fn build_loop(
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&mut self,
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condition: ASTNode,
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body: Vec<ASTNode>,
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) -> Result<ValueId, String> {
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// 1. ブロックの準備
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let preheader_id = self.current_block()?;
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let header_id = self.new_block();
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let body_id = self.new_block();
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let after_loop_id = self.new_block();
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self.loop_header = Some(header_id);
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self.continue_snapshots.clear();
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// 2. Preheader -> Header へのジャンプ
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self.emit_jump(header_id)?;
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let _ = self.add_predecessor(header_id, preheader_id);
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// 3. Headerブロックの準備（unsealed状態）
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self.set_current_block(header_id)?;
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let _ = self.mark_block_unsealed(header_id);
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// 4. ループ変数のPhi nodeを準備
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// ここでは、ループ内で変更される可能性のある変数を事前に検出するか、
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// または変数アクセス時に遅延生成する
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self.prepare_loop_variables(header_id, preheader_id)?;
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// 5. 条件評価（Phi nodeの結果を使用）
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let condition_value = self.build_expression_with_phis(condition)?;
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// 6. 条件分岐
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self.emit_branch(condition_value, body_id, after_loop_id)?;
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let _ = self.add_predecessor(body_id, header_id);
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let _ = self.add_predecessor(after_loop_id, header_id);
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// 7. ループボディの構築
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self.set_current_block(body_id)?;
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// Optional safepoint per loop-iteration
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if std::env::var("NYASH_BUILDER_SAFEPOINT_LOOP").ok().as_deref() == Some("1") {
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self.emit_safepoint()?;
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}
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// ボディをビルド
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for stmt in body {
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self.build_statement(stmt)?;
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}
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// latchブロックのスナップショットを保存（phi入力解決用）
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let latch_snapshot = self.get_current_variable_map();
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self.block_var_maps.insert(body_id, latch_snapshot);
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// 8. Latchブロック（ボディの最後）からHeaderへ戻る
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let latch_id = self.current_block()?;
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self.emit_jump(header_id)?;
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let _ = self.add_predecessor(header_id, latch_id);
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// 9. Headerブロックをシール（全predecessors確定）
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self.seal_block(header_id, latch_id)?;
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// 10. ループ後の処理
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self.set_current_block(after_loop_id)?;
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// void値を返す
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let void_dst = self.new_value();
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self.emit_const(void_dst, ConstValue::Void)?;
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Ok(void_dst)
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}
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/// ループ変数の準備（事前検出または遅延生成）
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fn prepare_loop_variables(
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&mut self,
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header_id: BasicBlockId,
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preheader_id: BasicBlockId,
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) -> Result<(), String> {
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// 現在の変数マップから、ループで使用される可能性のある変数を取得
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let current_vars = self.get_current_variable_map();
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// preheader時点のスナップショット（後でphi入力の解析に使う）
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self.block_var_maps.insert(preheader_id, current_vars.clone());
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// 各変数に対して不完全なPhi nodeを作成
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let mut incomplete_phis = Vec::new();
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for (var_name, &value_before) in ¤t_vars {
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let phi_id = self.new_value();
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// 不完全なPhi nodeを作成（preheaderからの値のみ設定）
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let incomplete_phi = IncompletePhi {
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phi_id,
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var_name: var_name.clone(),
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known_inputs: vec![(preheader_id, value_before)],
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};
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incomplete_phis.push(incomplete_phi);
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// 変数マップを更新（Phi nodeの結果を使用）
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self.update_variable(var_name.clone(), phi_id);
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}
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// 不完全なPhi nodeを記録
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self.incomplete_phis.insert(header_id, incomplete_phis);
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Ok(())
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}
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/// ブロックをシールし、不完全なPhi nodeを完成させる
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fn seal_block(
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&mut self,
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block_id: BasicBlockId,
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latch_id: BasicBlockId,
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) -> Result<(), String> {
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// 不完全なPhi nodeを取得
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if let Some(incomplete_phis) = self.incomplete_phis.remove(&block_id) {
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for mut phi in incomplete_phis {
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for (cid, snapshot) in &self.continue_snapshots {
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if let Some(v) = snapshot.get(&phi.var_name) {
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phi.known_inputs.push((*cid, *v));
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}
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}
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let value_after = self
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.get_variable_at_block(&phi.var_name, latch_id)
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.ok_or_else(|| {
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format!("Variable {} not found at latch block", phi.var_name)
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})?;
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phi.known_inputs.push((latch_id, value_after));
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self.emit_phi_at_block_start(block_id, phi.phi_id, phi.known_inputs)?;
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self.update_variable(phi.var_name.clone(), phi.phi_id);
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}
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}
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// ブロックをシール済みとしてマーク
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self.mark_block_sealed(block_id)?;
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Ok(())
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}
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// --- ヘルパーメソッド（親ビルダーへの委譲） ---
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fn current_block(&self) -> Result<BasicBlockId, String> {
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self.parent_builder.current_block
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.ok_or_else(|| "No current block".to_string())
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}
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fn new_block(&mut self) -> BasicBlockId {
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self.parent_builder.block_gen.next()
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}
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fn new_value(&mut self) -> ValueId {
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self.parent_builder.value_gen.next()
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}
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fn set_current_block(&mut self, block_id: BasicBlockId) -> Result<(), String> {
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self.parent_builder.start_new_block(block_id)
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}
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fn emit_jump(&mut self, target: BasicBlockId) -> Result<(), String> {
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self.parent_builder.emit_instruction(MirInstruction::Jump { target })
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}
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fn emit_branch(
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&mut self,
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condition: ValueId,
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then_bb: BasicBlockId,
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else_bb: BasicBlockId,
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) -> Result<(), String> {
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self.parent_builder.emit_instruction(MirInstruction::Branch {
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condition,
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then_bb,
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else_bb,
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})
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}
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fn emit_safepoint(&mut self) -> Result<(), String> {
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self.parent_builder.emit_instruction(MirInstruction::Safepoint)
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}
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fn emit_const(&mut self, dst: ValueId, value: ConstValue) -> Result<(), String> {
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self.parent_builder.emit_instruction(MirInstruction::Const { dst, value })
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}
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fn emit_phi_at_block_start(
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&mut self,
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block_id: BasicBlockId,
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dst: ValueId,
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inputs: Vec<(BasicBlockId, ValueId)>,
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) -> Result<(), String> {
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// Phi nodeをブロックの先頭に挿入
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if let Some(ref mut function) = self.parent_builder.current_function {
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if let Some(block) = function.get_block_mut(block_id) {
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// Phi命令は必ずブロックの先頭に配置
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let phi_inst = MirInstruction::Phi { dst, inputs };
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block.instructions.insert(0, phi_inst);
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Ok(())
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} else {
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Err(format!("Block {} not found", block_id))
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}
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} else {
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Err("No current function".to_string())
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}
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}
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fn add_predecessor(&mut self, block: BasicBlockId, pred: BasicBlockId) -> Result<(), String> {
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if let Some(ref mut function) = self.parent_builder.current_function {
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if let Some(block) = function.get_block_mut(block) {
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block.add_predecessor(pred);
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Ok(())
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} else {
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Err(format!("Block {} not found", block))
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}
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} else {
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Err("No current function".to_string())
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}
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}
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fn mark_block_unsealed(&mut self, _block_id: BasicBlockId) -> Result<(), String> {
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// ブロックはデフォルトでunsealedなので、特に何もしない
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// （既にBasicBlock::newでsealed: falseに初期化されている）
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Ok(())
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}
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fn mark_block_sealed(&mut self, block_id: BasicBlockId) -> Result<(), String> {
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if let Some(ref mut function) = self.parent_builder.current_function {
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if let Some(block) = function.get_block_mut(block_id) {
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block.seal();
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Ok(())
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} else {
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Err(format!("Block {} not found", block_id))
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}
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} else {
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Err("No current function".to_string())
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}
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}
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fn get_current_variable_map(&self) -> HashMap<String, ValueId> {
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self.parent_builder.variable_map.clone()
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}
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fn update_variable(&mut self, name: String, value: ValueId) {
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self.parent_builder.variable_map.insert(name, value);
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}
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fn get_variable_at_block(&self, name: &str, block_id: BasicBlockId) -> Option<ValueId> {
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// まずブロックごとのスナップショットを優先
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if let Some(map) = self.block_var_maps.get(&block_id) {
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if let Some(v) = map.get(name) { return Some(*v); }
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}
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// フォールバック：現在の変数マップ（単純ケース用）
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self.parent_builder.variable_map.get(name).copied()
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}
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fn build_expression_with_phis(&mut self, expr: ASTNode) -> Result<ValueId, String> {
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// Phi nodeの結果を考慮しながら式を構築
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self.parent_builder.build_expression(expr)
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}
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fn build_statement(&mut self, stmt: ASTNode) -> Result<ValueId, String> {
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match stmt {
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ASTNode::Continue { .. } => {
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let snapshot = self.get_current_variable_map();
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let cur_block = self.current_block()?;
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self.block_var_maps.insert(cur_block, snapshot.clone());
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self.continue_snapshots.push((cur_block, snapshot));
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if let Some(header) = self.loop_header {
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self.emit_jump(header)?;
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let _ = self.add_predecessor(header, cur_block);
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}
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let next_block = self.new_block();
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self.set_current_block(next_block)?;
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let void_id = self.new_value();
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self.emit_const(void_id, ConstValue::Void)?;
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Ok(void_id)
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}
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other => self.parent_builder.build_expression(other),
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}
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}
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}
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