[fix]修复部分常量构建，[Pass]建立Pass基类和管理器，预重构优化遍结构

src/SysYIRCFGOpt.cpp

@@ -463,9 +463,9 @@ bool SysYCFGOpt::SysYAddReturn(Function *func, IRBuilder* pBuilder) {
         pBuilder->setPosition(block.get(), block->end());
         // TODO: 如果int float函数缺少返回值是否需要报错
         if (func->getReturnType()->isInt()) {
-          pBuilder->createReturnInst(ConstantValue::get(0));
+          pBuilder->createReturnInst(ConstantInteger::get(0));
         } else if (func->getReturnType()->isFloat()) {
-          pBuilder->createReturnInst(ConstantValue::get(0.0F));
+          pBuilder->createReturnInst(ConstantFloating::get(0.0F));
         } else {
           pBuilder->createReturnInst();
         }