[IR]:增加默认添加ret指令逻辑

src/SysYIRGenerator.cpp

@@ -204,6 +204,7 @@ std::any SysYIRGenerator::visitFuncType(SysYParser::FuncTypeContext *ctx) {
 std::any SysYIRGenerator::visitFuncDef(SysYParser::FuncDefContext *ctx){
   // 更新作用域
   module->enterNewScope();
+  HasReturnInst = false;
 
   auto name = ctx->Ident()->getText();
   std::vector<Type *> paramTypes;
@@ -243,6 +244,18 @@ std::any SysYIRGenerator::visitFuncDef(SysYParser::FuncDefContext *ctx){
     visitBlockItem(item);
   }
 
+  if(HasReturnInst == false) {
+    // 如果没有return语句，则默认返回0
+    if (returnType != Type::getVoidType()) {
+      Value* returnValue = ConstantValue::get(0);
+      if (returnType == Type::getFloatType()) {
+        returnValue = ConstantValue::get(0.0f);
+      }
+      builder.createReturnInst(returnValue);
+    } else {
+      builder.createReturnInst();
+    }
+  }
   module->leaveScope();
 
   return std::any();
@@ -478,6 +491,7 @@ std::any SysYIRGenerator::visitReturnStmt(SysYParser::ReturnStmtContext *ctx) {
       }
     }
   builder.createReturnInst(returnValue);
+  HasReturnInst = true;
   return std::any();
 }