fix(frontend): 修复部分实现

src/irgen/IRGen.h

@@ -1,4 +1,4 @@
-// 将 ANTLR parse tree 翻译为极简 IR。
+// 将语法树翻译为极简 IR。
 // 实现拆分在 IRGenFunc/IRGenStmt/IRGenExp/IRGenDecl。
 
 #pragma once
@@ -32,7 +32,7 @@ class IRGenImpl {
  private:
   void GenFuncDef(SysYParser::FuncDefContext& func);
   void GenBlock(SysYParser::BlockContext& block);
-  void GenStmt(SysYParser::StmtContext& stmt);
+  bool GenStmt(SysYParser::StmtContext& stmt);
   void GenVarDecl(SysYParser::VarDeclContext& decl);
   void GenReturnStmt(SysYParser::ReturnStmtContext& ret);
 

src/irgen/IRGenDecl.cpp

@@ -6,27 +6,22 @@
 #include "ir/IR.h"
 
 void IRGenImpl::GenBlock(SysYParser::BlockContext& block) {
-  for (auto* stmt : block.stmt()) {
-    if (stmt && stmt->varDecl()) {
-      const std::string name = stmt->varDecl()->Ident()->getText();
-      auto* slot = builder_.CreateAllocaI32(ir::DefaultContext().NextTemp());
-      locals_[name] = slot;
-    }
-  }
-
   for (auto* stmt : block.stmt()) {
     if (stmt) {
-      GenStmt(*stmt);
+      if (GenStmt(*stmt)) {
+        break;
+      }
     }
   }
 }
 
 void IRGenImpl::GenVarDecl(SysYParser::VarDeclContext& decl) {
   const std::string name = decl.Ident()->getText();
-  auto it = locals_.find(name);
-  if (it == locals_.end()) {
-    throw std::runtime_error("[irgen] 变量栈槽未创建: " + name);
+  if (locals_.find(name) != locals_.end()) {
+    throw std::runtime_error("[irgen] 重复定义变量: " + name);
   }
+  auto* slot = builder_.CreateAllocaI32(ir::DefaultContext().NextTemp());
+  locals_[name] = slot;
 
   ir::Value* init = nullptr;
   if (decl.exp()) {
@@ -34,5 +29,5 @@ void IRGenImpl::GenVarDecl(SysYParser::VarDeclContext& decl) {
   } else {
     init = ir::DefaultContext().GetConstInt(0);
   }
-  builder_.CreateStore(init, it->second);
+  builder_.CreateStore(init, slot);
 }

src/irgen/IRGenDriver.cpp

@@ -9,12 +9,12 @@
 
 std::unique_ptr<ir::Module> GenerateIR(antlr4::tree::ParseTree* tree) {
   if (!tree) {
-    throw std::runtime_error("[irgen] parse tree 为空");
+    throw std::runtime_error("[irgen] 语法树为空");
   }
 
   auto* cu = dynamic_cast<SysYParser::CompUnitContext*>(tree);
   if (!cu) {
-    throw std::runtime_error("[irgen] parse tree 根节点不是 compUnit");
+    throw std::runtime_error("[irgen] 语法树根节点不是 compUnit");
   }
 
   auto module = std::make_unique<ir::Module>();

src/irgen/IRGenStmt.cpp

@@ -5,14 +5,14 @@
 #include "SysYParser.h"
 #include "ir/IR.h"
 
-void IRGenImpl::GenStmt(SysYParser::StmtContext& stmt) {
+bool IRGenImpl::GenStmt(SysYParser::StmtContext& stmt) {
   if (stmt.varDecl()) {
     GenVarDecl(*stmt.varDecl());
-    return;
+    return false;
   }
   if (stmt.returnStmt()) {
     GenReturnStmt(*stmt.returnStmt());
-    return;
+    return true;
   }
   throw std::runtime_error("[irgen] 暂不支持的语句类型");
 }