[backend]修复了引入常量重质化后全局常量加载指令的缺失问题

src/RISCv64Backend.cpp

@@ -635,6 +635,14 @@ void RISCv64CodeGen::select_instructions(DAGNode* node, const RegAllocResult& al
                 }
             } else {
                 std::string ptr_reg = get_preg_or_temp(ptr_node->result_vreg);
+                
+                // [与STORE逻辑类似的修复] 如果是从一个全局地址加载，先用la加载地址
+                if (ptr_node->kind == DAGNode::CONSTANT) {
+                    if (auto global = dynamic_cast<GlobalValue*>(ptr_node->value)) {
+                        ss_inst << "la " << ptr_reg << ", " << global->getName() << "\n\t";
+                    }
+                }
+                
                 ss_inst << "lw " << dest_reg << ", 0(" << ptr_reg << ")";
             }
             break;
@@ -660,18 +668,30 @@ void RISCv64CodeGen::select_instructions(DAGNode* node, const RegAllocResult& al
                         // 如果 STORE 的目标是浮点数，这里逻辑需要调整
                     }
                 } else if (auto global = dynamic_cast<GlobalValue*>(val_node->value)) {
-                    // 如果是存储全局变量的地址
+                    // 如果要存储的值是另一个全局变量的地址
                     ss_inst << "la " << src_reg << ", " << global->getName() << "\n\t";
                 }
             }
             
+            // [本次修复] 处理目标地址，并生成最终的存储指令
             if (ptr_node->kind == DAGNode::ALLOCA_ADDR) {
+                // 情况1: 存储到栈上的局部变量
                 if (auto alloca_inst = dynamic_cast<AllocaInst*>(ptr_node->value)) {
                     int offset = alloc.stack_map.at(alloca_inst);
                     ss_inst << "sw " << src_reg << ", " << offset << "(s0)";
                 }
             } else {
+                // 情况2: 存储到指针指向的地址 (可能是全局变量或已计算的地址)
                 std::string ptr_reg = get_preg_or_temp(ptr_node->result_vreg);
+
+                // 如果指针本身是一个全局变量的地址，需要先用 la 加载它
+                if (ptr_node->kind == DAGNode::CONSTANT) {
+                    if (auto global = dynamic_cast<GlobalValue*>(ptr_node->value)) {
+                        ss_inst << "la " << ptr_reg << ", " << global->getName() << "\n\t";
+                    }
+                }
+
+                // 生成最终的存储指令
                 ss_inst << "sw " << src_reg << ", 0(" << ptr_reg << ")";
             }
             break;
@@ -712,10 +732,12 @@ void RISCv64CodeGen::select_instructions(DAGNode* node, const RegAllocResult& al
             std::string lhs_reg = get_preg_or_temp(lhs_node->result_vreg);
             std::string rhs_reg = get_preg_or_temp(rhs_node->result_vreg);
             
-            // [V2 特性] 在生成二元运算指令前，检查操作数是否为常数，并按需加载
+            // [V2 特性] & [上次修复] 在生成二元运算指令前，检查操作数是否为常数（立即数或全局地址），并按需加载
             if (lhs_node->kind == DAGNode::CONSTANT) {
                  if (auto c = dynamic_cast<ConstantValue*>(lhs_node->value)) {
                      ss_inst << "li " << lhs_reg << ", " << c->getInt() << "\n\t";
+                 } else if (auto g = dynamic_cast<GlobalValue*>(lhs_node->value)) {
+                     ss_inst << "la " << lhs_reg << ", " << g->getName() << "\n\t";
                  }
             }
             if (rhs_node->kind == DAGNode::CONSTANT) {
@@ -728,6 +750,8 @@ void RISCv64CodeGen::select_instructions(DAGNode* node, const RegAllocResult& al
                     }
                     // 否则，正常加载
                     ss_inst << "li " << rhs_reg << ", " << c->getInt() << "\n\t";
+                } else if (auto g = dynamic_cast<GlobalValue*>(rhs_node->value)) {
+                    ss_inst << "la " << rhs_reg << ", " << g->getName() << "\n\t";
                 }
             }
 
@@ -853,10 +877,12 @@ void RISCv64CodeGen::select_instructions(DAGNode* node, const RegAllocResult& al
             if (!node->operands.empty() && node->operands[0]) {
                 DAGNode* ret_val_node = node->operands[0];
                 
-                // [V2 特性] 如果返回值是常量，直接加载到 a0
+                // [V2 特性] & [上次修复] 如果返回值是常量（立即数或全局地址），直接加载到 a0
                 if (ret_val_node->kind == DAGNode::CONSTANT) {
                     if (auto c = dynamic_cast<ConstantValue*>(ret_val_node->value)) {
                         ss_inst << "li a0, " << c->getInt() << "\n";
+                    } else if (auto g = dynamic_cast<GlobalValue*>(ret_val_node->value)) {
+                        ss_inst << "la a0, " << g->getName() << "\n";
                     }
                 } else {
                     std::string return_val_reg = get_preg_or_temp(ret_val_node->result_vreg);