[IR]消除Falltrhough现象

[IR]优化生成Ret指令逻辑
[README]添加TODO表

README.md

@@ -37,4 +37,13 @@ mysysy/ $ bash setup.sh
     ```
 
 ### 配套脚本
-   （TODO: 需要完善）
+   （TODO: 需要完善）
+
+
+### TODO_list:
+
+除开注释中的TODO后续时间充足可以考虑的TODO:
+
+- store load指令由于gep指令的引入, 维度信息的记录是非必须的, 考虑删除
+
+- use def关系经过mem2reg和phi函数明确转换为ssa形式, 以及函数参数通过value数组明确定义, 使得基本块的args参数信息记录非必须, 考虑删除

src/SysYIRGenerator.cpp

@@ -340,7 +340,6 @@ 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;
@@ -376,22 +375,34 @@ std::any SysYIRGenerator::visitFuncDef(SysYParser::FuncDefContext *ctx){
     module->addVariable(paramNames[i], alloca);
   }
 
+  // 在处理函数体之前，创建一个新的基本块作为函数体的实际入口
+  // 这样 entryBB 就可以在完成初始化后跳转到这里
+  BasicBlock* funcBodyEntry = function->addBasicBlock("funcBodyEntry");
+  
+  // 从 entryBB 无条件跳转到 funcBodyEntry
+  builder.createUncondBrInst(funcBodyEntry, {});
+  builder.setPosition(funcBodyEntry,funcBodyEntry->end()); // 将插入点设置到 funcBodyEntry
+
   for (auto item : ctx->blockStmt()->blockItem()) {
     visitBlockItem(item);
   }
 
-  if(HasReturnInst == false) {
-    // 如果没有return语句，则默认返回0
-    if (returnType != Type::getVoidType()) {
-      Value* returnValue = ConstantInteger::get(0);
-      if (returnType == Type::getFloatType()) {
-        returnValue = ConstantFloating::get(0.0f);
-      }
-      builder.createReturnInst(returnValue);
+  // 如果函数没有显式的返回语句，且返回类型不是 void，则需要添加一个默认的返回值
+  ReturnInst* retinst = nullptr;
+  retinst = dynamic_cast<ReturnInst*>(builder.getBasicBlock()->terminator()->get());
+
+  if (!retinst) {
+    if (returnType->isVoid()) {
+        builder.createReturnInst();
+    } else if (returnType->isInt()) {
+        builder.createReturnInst(ConstantInteger::get(0)); // 默认返回 0
+    } else if (returnType->isFloat()) {
+        builder.createReturnInst(ConstantFloating::get(0.0f)); // 默认返回 0.0f
     } else {
-      builder.createReturnInst();
+        assert(false && "Function with no explicit return and non-void type should return a value.");
     }
   }
+
   module->leaveScope();
 
   return std::any();
@@ -549,6 +560,7 @@ std::any SysYIRGenerator::visitIfStmt(SysYParser::IfStmtContext *ctx) {
       ctx->stmt(0)->accept(this);
       module->leaveScope();
     }
+    builder.createUncondBrInst(exitBlock, {});
     BasicBlock::conectBlocks(builder.getBasicBlock(), exitBlock);
 
     labelstring << "if_exit.L" << builder.getLabelIndex();
@@ -570,6 +582,7 @@ std::any SysYIRGenerator::visitWhileStmt(SysYParser::WhileStmtContext *ctx) {
   labelstring << "while_head.L" << builder.getLabelIndex();
   BasicBlock *headBlock = function->addBasicBlock(labelstring.str());
   labelstring.str("");
+  builder.createUncondBrInst(headBlock, {});
   BasicBlock::conectBlocks(curBlock, headBlock);
   builder.setPosition(headBlock, headBlock->end());
 
@@ -654,7 +667,7 @@ std::any SysYIRGenerator::visitReturnStmt(SysYParser::ReturnStmtContext *ctx) {
       }
     }
   builder.createReturnInst(returnValue);
-  HasReturnInst = true;
+
   return std::any();
 }
 

src/include/SysYIRGenerator.h

@@ -62,8 +62,6 @@ private:
 public:
   SysYIRGenerator() = default;
 
-  bool HasReturnInst;
-
 public:
   Module *get() const { return module.get(); }
   IRBuilder *getBuilder(){ return &builder; }