[backend]添加了DAG图打印函数；为分支指令引入了延迟物化；添加了函数参数溢出到栈的处理逻辑

src/RISCv64ISel.cpp

@@ -83,6 +83,10 @@ void RISCv64ISel::selectBasicBlock(BasicBlock* bb) {
     CurMBB = bb_map.at(bb);
     auto dag = build_dag(bb);
 
+    if (DEBUG) { // 使用 DEBUG 宏或变量来控制是否打印
+        print_dag(dag, bb->getName());
+    }
+
     std::map<Value*, DAGNode*> value_to_node;
     for(const auto& node : dag) {
         if (node->value) {
@@ -486,7 +490,9 @@ void RISCv64ISel::selectNode(DAGNode* node) {
         case DAGNode::CALL: {
             auto call = dynamic_cast<CallInst*>(node->value);
             // 处理函数参数，放入a0-a7物理寄存器
-            for (size_t i = 0; i < node->operands.size() && i < 8; ++i) {
+            size_t num_operands = node->operands.size();
+            size_t reg_arg_count = std::min(num_operands, (size_t)8);
+            for (size_t i = 0; i < reg_arg_count; ++i) {
                 DAGNode* arg_node = node->operands[i];
                 auto arg_preg = static_cast<PhysicalReg>(static_cast<int>(PhysicalReg::A0) + i);
 
@@ -505,11 +511,63 @@ void RISCv64ISel::selectNode(DAGNode* node) {
                     CurMBB->addInstruction(std::move(mv));
                 }
             }
+            if (num_operands > 8) {
+                size_t stack_arg_count = num_operands - 8;
+                int stack_space = stack_arg_count * 8; // RV64中每个参数槽位8字节
+
+                // 2a. 在栈上分配空间
+                auto alloc_instr = std::make_unique<MachineInstr>(RVOpcodes::ADDI);
+                alloc_instr->addOperand(std::make_unique<RegOperand>(PhysicalReg::SP));
+                alloc_instr->addOperand(std::make_unique<RegOperand>(PhysicalReg::SP));
+                alloc_instr->addOperand(std::make_unique<ImmOperand>(-stack_space));
+                CurMBB->addInstruction(std::move(alloc_instr));
+
+                // 2b. 存储每个栈参数
+                for (size_t i = 8; i < num_operands; ++i) {
+                    DAGNode* arg_node = node->operands[i];
+                    unsigned src_vreg;
+                    
+                    // 准备源寄存器
+                    if (arg_node->kind == DAGNode::CONSTANT) {
+                        // 如果是常量，先加载到临时寄存器
+                        src_vreg = getNewVReg();
+                        auto const_val = dynamic_cast<ConstantValue*>(arg_node->value);
+                        auto li = std::make_unique<MachineInstr>(RVOpcodes::LI);
+                        li->addOperand(std::make_unique<RegOperand>(src_vreg));
+                        li->addOperand(std::make_unique<ImmOperand>(const_val->getInt()));
+                        CurMBB->addInstruction(std::move(li));
+                    } else {
+                        src_vreg = getVReg(arg_node->value);
+                    }
+                    
+                    // 计算在栈上的偏移量
+                    int offset = (i - 8) * 8;
+                    
+                    // 生成 sd 指令
+                    auto sd_instr = std::make_unique<MachineInstr>(RVOpcodes::SD);
+                    sd_instr->addOperand(std::make_unique<RegOperand>(src_vreg));
+                    sd_instr->addOperand(std::make_unique<MemOperand>(
+                        std::make_unique<RegOperand>(PhysicalReg::SP),
+                        std::make_unique<ImmOperand>(offset)
+                    ));
+                    CurMBB->addInstruction(std::move(sd_instr));
+                }
+            }
 
             auto call_instr = std::make_unique<MachineInstr>(RVOpcodes::CALL);
             call_instr->addOperand(std::make_unique<LabelOperand>(call->getCallee()->getName()));
             CurMBB->addInstruction(std::move(call_instr));
             
+            if (num_operands > 8) {
+                size_t stack_arg_count = num_operands - 8;
+                int stack_space = stack_arg_count * 8;
+
+                auto dealloc_instr = std::make_unique<MachineInstr>(RVOpcodes::ADDI);
+                dealloc_instr->addOperand(std::make_unique<RegOperand>(PhysicalReg::SP));
+                dealloc_instr->addOperand(std::make_unique<RegOperand>(PhysicalReg::SP));
+                dealloc_instr->addOperand(std::make_unique<ImmOperand>(stack_space));
+                CurMBB->addInstruction(std::move(dealloc_instr));
+            }
             // 处理返回值，从a0移动到目标虚拟寄存器
             if (!call->getType()->isVoid()) {
                 auto mv_instr = std::make_unique<MachineInstr>(RVOpcodes::MV);
@@ -545,33 +603,59 @@ void RISCv64ISel::selectNode(DAGNode* node) {
         }
 
         case DAGNode::BRANCH: {
-            if (auto cond_br = dynamic_cast<CondBrInst*>(node->value)) {
+        // 处理条件分支
-                // [V2优点] 采用更健壮的if-then-else分支逻辑。
+        if (auto cond_br = dynamic_cast<CondBrInst*>(node->value)) {
-                auto cond_vreg = getVReg(cond_br->getCondition());
+            Value* condition = cond_br->getCondition();
-                auto then_bb_name = cond_br->getThenBlock()->getName();
+            auto then_bb_name = cond_br->getThenBlock()->getName();
-                auto else_bb_name = cond_br->getElseBlock()->getName();
+            auto else_bb_name = cond_br->getElseBlock()->getName();
 
-                // bne cond, zero, then_label  (如果cond不为0，则跳转到then)
+            // [优化] 检查分支条件是否为编译期常量
+            if (auto const_cond = dynamic_cast<ConstantValue*>(condition)) {
+                // 如果条件是常量，直接生成一个无条件跳转J，而不是BNE
+                if (const_cond->getInt() != 0) { // 条件为 true
+                    auto j_instr = std::make_unique<MachineInstr>(RVOpcodes::J);
+                    j_instr->addOperand(std::make_unique<LabelOperand>(then_bb_name));
+                    CurMBB->addInstruction(std::move(j_instr));
+                } else { // 条件为 false
+                    auto j_instr = std::make_unique<MachineInstr>(RVOpcodes::J);
+                    j_instr->addOperand(std::make_unique<LabelOperand>(else_bb_name));
+                    CurMBB->addInstruction(std::move(j_instr));
+                }
+            } 
+            // 如果条件不是常量，则执行标准流程
+            else {
+                // [修复] 为条件变量生成加载指令（如果它是常量的话，尽管上面已经处理了）
+                // 这一步是为了逻辑完整，以防有其他类型的常量没有被捕获
+                if (auto const_val = dynamic_cast<ConstantValue*>(condition)) {
+                    auto li = std::make_unique<MachineInstr>(RVOpcodes::LI);
+                    li->addOperand(std::make_unique<RegOperand>(getVReg(const_val)));
+                    li->addOperand(std::make_unique<ImmOperand>(const_val->getInt()));
+                    CurMBB->addInstruction(std::move(li));
+                }
+
+                auto cond_vreg = getVReg(condition);
+                
+                // 生成 bne cond, zero, then_label (如果cond不为0，则跳转到then)
                 auto br_instr = std::make_unique<MachineInstr>(RVOpcodes::BNE);
                 br_instr->addOperand(std::make_unique<RegOperand>(cond_vreg));
                 br_instr->addOperand(std::make_unique<RegOperand>(PhysicalReg::ZERO));
                 br_instr->addOperand(std::make_unique<LabelOperand>(then_bb_name));
                 CurMBB->addInstruction(std::move(br_instr));
                 
-                // 无条件跳转到else块 (如果上面分支未发生)
+                // 为else分支生成无条件跳转 (后续Pass可以优化掉不必要的跳转)
-                // 注意：在实际的CFG中，这个J指令可能不是必须的，
-                // 因为else块可能是下一个块。但为了通用性，这里生成它。
                 auto j_instr = std::make_unique<MachineInstr>(RVOpcodes::J);
                 j_instr->addOperand(std::make_unique<LabelOperand>(else_bb_name));
                 CurMBB->addInstruction(std::move(j_instr));
-
-            } else if (auto uncond_br = dynamic_cast<UncondBrInst*>(node->value)) {
-                auto j_instr = std::make_unique<MachineInstr>(RVOpcodes::J);
-                j_instr->addOperand(std::make_unique<LabelOperand>(uncond_br->getBlock()->getName()));
-                CurMBB->addInstruction(std::move(j_instr));
             }
-            break;
         } 
+        // 处理无条件分支
+        else if (auto uncond_br = dynamic_cast<UncondBrInst*>(node->value)) {
+            auto j_instr = std::make_unique<MachineInstr>(RVOpcodes::J);
+            j_instr->addOperand(std::make_unique<LabelOperand>(uncond_br->getBlock()->getName()));
+            CurMBB->addInstruction(std::move(j_instr));
+        }
+        break;
+    }
 
         case DAGNode::MEMSET: {
             // [V1设计保留] Memset的核心展开逻辑在虚拟寄存器层面是正确的，无需修改。
@@ -808,4 +892,98 @@ std::vector<std::unique_ptr<RISCv64ISel::DAGNode>> RISCv64ISel::build_dag(BasicB
     return nodes_storage;
 }
 
+// [新] 打印DAG图以供调试的辅助函数
+void RISCv64ISel::print_dag(const std::vector<std::unique_ptr<DAGNode>>& dag, const std::string& bb_name) {
+    // 检查是否有DEBUG宏或者全局变量，避免在非调试模式下打印
+    // if (!DEBUG) return; 
+
+    std::cerr << "=== DAG for Basic Block: " << bb_name << " ===\n";
+    std::set<DAGNode*> visited;
+
+    // 为节点分配临时ID，方便阅读
+    std::map<DAGNode*, int> node_to_id;
+    int current_id = 0;
+    for (const auto& node_ptr : dag) {
+        node_to_id[node_ptr.get()] = current_id++;
+    }
+
+    // 将NodeKind枚举转换为字符串的辅助函数
+    auto get_kind_string = [](DAGNode::NodeKind kind) {
+        switch (kind) {
+            case DAGNode::CONSTANT: return "CONSTANT";
+            case DAGNode::LOAD: return "LOAD";
+            case DAGNode::STORE: return "STORE";
+            case DAGNode::BINARY: return "BINARY";
+            case DAGNode::CALL: return "CALL";
+            case DAGNode::RETURN: return "RETURN";
+            case DAGNode::BRANCH: return "BRANCH";
+            case DAGNode::ALLOCA_ADDR: return "ALLOCA_ADDR";
+            case DAGNode::UNARY: return "UNARY";
+            case DAGNode::MEMSET: return "MEMSET";
+            default: return "UNKNOWN";
+        }
+    };
+
+    // 递归打印节点的lambda表达式
+    std::function<void(DAGNode*, int)> print_node = 
+        [&](DAGNode* node, int indent) {
+        if (!node) return;
+
+        std::string current_indent(indent, ' ');
+        int node_id = node_to_id.count(node) ? node_to_id[node] : -1;
+
+        std::cerr << current_indent << "Node#" << node_id << ": " << get_kind_string(node->kind);
+        
+        // 尝试打印关联的虚拟寄存器
+        if (node->value && vreg_map.count(node->value)) {
+            std::cerr << " (vreg: %vreg" << vreg_map.at(node->value) << ")";
+        }
+
+        // 打印关联的IR Value信息
+        if (node->value) {
+            std::cerr << " [";
+            if (auto inst = dynamic_cast<Instruction*>(node->value)) {
+                std::cerr << inst->getKindString();
+                if (!inst->getName().empty()) {
+                    std::cerr << "(" << inst->getName() << ")";
+                }
+            } else if (auto constant = dynamic_cast<ConstantValue*>(node->value)) {
+                std::cerr << "Const(" << constant->getInt() << ")";
+            } else if (auto global = dynamic_cast<GlobalValue*>(node->value)) {
+                std::cerr << "Global(" << global->getName() << ")";
+            } else if (auto alloca = dynamic_cast<AllocaInst*>(node->value)) {
+                std::cerr << "Alloca(" << alloca->getName() << ")";
+            }
+            std::cerr << "]";
+        }
+        std::cerr << "\n";
+
+        if (visited.count(node)) {
+            std::cerr << current_indent << "  (已打印过子节点)\n";
+            return;
+        }
+        visited.insert(node);
+
+        if (!node->operands.empty()) {
+            std::cerr << current_indent << "  Operands:\n";
+            for (auto operand : node->operands) {
+                print_node(operand, indent + 4);
+            }
+        }
+    };
+
+    // 从根节点（没有用户的节点，或有副作用的节点）开始打印
+    for (const auto& node_ptr : dag) {
+        if (node_ptr->users.empty() || 
+            node_ptr->kind == DAGNode::STORE || 
+            node_ptr->kind == DAGNode::RETURN || 
+            node_ptr->kind == DAGNode::BRANCH ||
+            node_ptr->kind == DAGNode::MEMSET) 
+        {
+            print_node(node_ptr.get(), 0);
+        }
+    }
+    std::cerr << "======================================\n\n";
+}
+
 } // namespace sysy

src/include/RISCv64ISel.h

@@ -34,6 +34,8 @@ private:
     DAGNode* get_operand_node(Value* val_ir, std::map<Value*, DAGNode*>&, std::vector<std::unique_ptr<DAGNode>>&);
     DAGNode* create_node(int kind, Value* val, std::map<Value*, DAGNode*>&, std::vector<std::unique_ptr<DAGNode>>&);
     
+    void print_dag(const std::vector<std::unique_ptr<DAGNode>>& dag, const std::string& bb_name);
+    
     // 状态
     Function* F; // 当前处理的高层IR函数
     std::unique_ptr<MachineFunction> MFunc; // 正在构建的底层LLIR函数