Lab4: Implement basic scalar optimizations and lower Phi nodes to assembly

include/ir/IR.h

@@ -236,7 +236,8 @@ enum class Opcode {
   GEP,
   ZExt,
   SIToFP,
-  FPToSI
+  FPToSI,
+  Phi
 };
 
 // User 是所有“会使用其他 Value 作为输入”的 IR 对象的抽象基类。
@@ -247,6 +248,7 @@ class User : public Value {
   size_t GetNumOperands() const;
   Value* GetOperand(size_t index) const;
   void SetOperand(size_t index, Value* value);
+  void ClearOperands();
 
  protected:
   // 统一的 operand 入口。
@@ -345,6 +347,18 @@ class StoreInst : public Instruction {
   Value* GetPtr() const;
 };
 
+class PhiInst : public Instruction {
+ public:
+  PhiInst(std::shared_ptr<Type> ty, std::string name = "");
+  void AddIncoming(Value* val, BasicBlock* bb);
+  size_t GetNumIncoming() const;
+  Value* GetIncomingValue(size_t i) const;
+  BasicBlock* GetIncomingBlock(size_t i) const;
+  void SetIncomingValue(size_t i, Value* val);
+  void SetIncomingBlock(size_t i, BasicBlock* bb);
+  void RemoveIncomingBlock(BasicBlock* bb);
+};
+
 // BasicBlock 已纳入 Value 体系，便于后续向更完整 IR 类图靠拢。
 // 当前其类型仍使用 void 作为占位，后续可替换为专门的 label type。
 class BasicBlock : public Value {
@@ -356,6 +370,15 @@ class BasicBlock : public Value {
   const std::vector<std::unique_ptr<Instruction>>& GetInstructions() const;
   const std::vector<BasicBlock*>& GetPredecessors() const;
   const std::vector<BasicBlock*>& GetSuccessors() const;
+
+  void AddPredecessor(BasicBlock* pred) { predecessors_.push_back(pred); }
+  void AddSuccessor(BasicBlock* succ) { successors_.push_back(succ); }
+  void ClearPredecessors() { predecessors_.clear(); }
+  void ClearSuccessors() { successors_.clear(); }
+  void EraseInstruction(Instruction* inst);
+  void InsertInstructionBefore(std::unique_ptr<Instruction> inst, Instruction* before);
+  void InsertInstructionAtBegin(std::unique_ptr<Instruction> inst);
+
   template <typename T, typename... Args>
   T* Append(Args&&... args) {
     if (HasTerminator()) {
@@ -457,6 +480,7 @@ class IRBuilder {
                          const std::string& name = "");
   CastInst* CreateFPToSI(Value* val, std::shared_ptr<Type> ty,
                          const std::string& name = "");
+  PhiInst* CreatePhi(std::shared_ptr<Type> ty, const std::string& name = "");
 
  private:
   Context& ctx_;