[midend-tco]添加TCO尾递归优化

src/backend/RISCv64/Optimize/Peephole.cpp

@@ -634,6 +634,22 @@ void PeepholeOptimizer::runOnMachineFunction(MachineFunction *mfunc) {
           }
         }
       }
+      // 8. 消除无用移动指令: mv a, a -> (删除)
+      else if (mi1->getOpcode() == RVOpcodes::MV &&
+               mi1->getOperands().size() == 2) {
+        if (mi1->getOperands()[0]->getKind() == MachineOperand::KIND_REG &&
+            mi1->getOperands()[1]->getKind() == MachineOperand::KIND_REG) {
+          auto *dst = static_cast<RegOperand *>(mi1->getOperands()[0].get());
+          auto *src = static_cast<RegOperand *>(mi1->getOperands()[1].get());
+          
+          // 检查源和目标寄存器是否相同
+          if (areRegsEqual(dst, src)) {
+            // 删除这条无用指令
+            instrs.erase(instrs.begin() + i);
+            changed = true;
+          }
+        }
+      }
 
       // 根据是否发生变化调整遍历索引
       if (!changed) {