[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) {

src/include/midend/Pass/Optimize/TailCallOpt.h

@@ -0,0 +1,39 @@
+#pragma once
+
+#include "Pass.h"
+#include "Dom.h"
+#include "Loop.h"
+
+namespace sysy {
+
+/**
+ * @class TailCallOpt
+ * @brief 优化尾调用的中端优化通道。
+ *
+ * 该类实现了一个针对函数级别的尾调用优化的优化通道（OptimizationPass）。
+ * 通过分析和转换 IR（中间表示），将可优化的尾调用转换为更高效的形式，
+ * 以减少函数调用的开销，提升程序性能。
+ *
+ * @note 需要传入 IRBuilder 指针用于 IR 构建和修改。
+ *
+ * @method runOnFunction
+ * 对指定函数进行尾调用优化。
+ *
+ * @method getPassID
+ * 获取当前优化通道的唯一标识符。
+ *
+ * @method getAnalysisUsage
+ * 指定该优化通道所依赖和失效的分析集合。
+ */
+class TailCallOpt : public OptimizationPass {
+private:
+  IRBuilder* builder;
+public:
+  TailCallOpt(IRBuilder* builder) : OptimizationPass("TailCallOpt", Granularity::Function), builder(builder) {}
+  static void *ID;
+  bool runOnFunction(Function *F, AnalysisManager &AM) override;
+  void *getPassID() const override { return &ID; }
+  void getAnalysisUsage(std::set<void *> &analysisDependencies, std::set<void *> &analysisInvalidations) const override;
+};
+
+} // namespace sysy

src/midend/CMakeLists.txt

@@ -25,6 +25,7 @@ add_library(midend_lib STATIC
     Pass/Optimize/GlobalStrengthReduction.cpp
     Pass/Optimize/BuildCFG.cpp
     Pass/Optimize/LargeArrayToGlobal.cpp
+    Pass/Optimize/TailCallOpt.cpp
 )
 
 # 包含中端模块所需的头文件路径

src/midend/Pass/Optimize/TailCallOpt.cpp

@@ -0,0 +1,125 @@
+#include "TailCallOpt.h"
+#include "IR.h"
+#include "IRBuilder.h"
+#include "SysYIROptUtils.h"
+#include <vector>
+// #include <iostream>
+#include <algorithm>
+
+namespace sysy {
+
+void *TailCallOpt::ID = (void *)&TailCallOpt::ID;
+
+void TailCallOpt::getAnalysisUsage(std::set<void *> &analysisDependencies, std::set<void *> &analysisInvalidations) const {
+  analysisInvalidations.insert(&DominatorTreeAnalysisPass::ID);
+  analysisInvalidations.insert(&LoopAnalysisPass::ID);
+}
+
+bool TailCallOpt::runOnFunction(Function *F, AnalysisManager &AM) {
+  std::vector<CallInst *> tailCallInsts;
+  // 遍历函数的所有基本块
+  for (auto &bb_ptr : F->getBasicBlocks()) {
+    auto BB = bb_ptr.get();
+    if (BB->getInstructions().empty()) continue; // 跳过空基本块
+
+    auto term_iter = BB->terminator();
+    if (term_iter == BB->getInstructions().end()) continue; // 没有终结指令则跳过
+    auto term = (*term_iter).get();
+
+    if (!term || !term->isReturn()) continue; // 不是返回指令则跳过
+    auto retInst = static_cast<ReturnInst *>(term);
+
+    Instruction *prevInst = nullptr;
+    if (BB->getInstructions().size() > 1) {
+        auto it = term_iter;
+        --it; // 获取返回指令前的指令
+        prevInst = (*it).get();
+    }
+
+    if (!prevInst || !prevInst->isCall()) continue; // 前一条不是调用指令则跳过
+    auto callInst = static_cast<CallInst *>(prevInst);
+
+    // 检查是否为尾递归调用：被调用函数与当前函数相同且返回值与调用结果匹配
+    if (callInst->getCallee() == F) {
+  // 对于尾递归，返回值应为调用结果或为 void 类型
+        if (retInst->getReturnValue() == callInst || 
+            (retInst->getReturnValue() == nullptr && callInst->getType()->isVoid())) {
+            tailCallInsts.push_back(callInst);
+        }
+    }
+  }
+
+  if (tailCallInsts.empty()) {
+    return false;
+  }
+
+  // 创建一个新的入口基本块，作为循环的前置块
+  auto original_entry = F->getEntryBlock();
+  auto new_entry = F->addBasicBlock("tco.entry");
+  auto loop_header = F->addBasicBlock("tco.loop_header");
+  
+  // 将原入口块中的所有指令移动到循环头块
+  loop_header->getInstructions().splice(loop_header->end(), original_entry->getInstructions());
+  original_entry->setName("tco.pre_header");
+
+  // 为函数参数创建 phi 节点
+  builder->setPosition(loop_header, loop_header->begin());
+  std::vector<PhiInst *> phis;
+  auto original_args = F->getArguments();
+  for (auto &arg : original_args) {
+    auto phi = builder->createPhiInst(arg->getType(), {}, {}, "tco.phi."+arg->getName());
+    phis.push_back(phi);
+  }
+
+  // 用 phi 节点替换所有原始参数的使用
+  for (size_t i = 0; i < original_args.size(); ++i) {
+    original_args[i]->replaceAllUsesWith(phis[i]);
+  }
+
+  // 设置 phi 节点的输入值
+  for (size_t i = 0; i < phis.size(); ++i) {
+    phis[i]->addIncoming(original_args[i], new_entry);
+  }
+
+  // 连接各个基本块
+  builder->setPosition(original_entry, original_entry->end());
+  builder->createUncondBrInst(new_entry);
+  original_entry->addSuccessor(new_entry);
+  
+  builder->setPosition(new_entry, new_entry->end());
+  builder->createUncondBrInst(loop_header);
+  new_entry->addSuccessor(loop_header);
+  loop_header->addPredecessor(new_entry);
+
+  // 处理每一个尾递归调用
+  for (auto callInst : tailCallInsts) {
+    auto tail_call_block = callInst->getParent();
+    
+  // 收集尾递归调用的参数
+    auto args_range = callInst->getArguments();
+    std::vector<Value*> args;
+    std::transform(args_range.begin(), args_range.end(), std::back_inserter(args), 
+                   [](auto& use_ptr){ return use_ptr->getValue(); });
+
+  // 用新的参数值更新 phi 节点
+    for (size_t i = 0; i < phis.size(); ++i) {
+        phis[i]->addIncoming(args[i], tail_call_block);
+    }
+
+  // 移除原有的调用和返回指令
+    auto term_iter = tail_call_block->terminator();
+    SysYIROptUtils::usedelete(term_iter);
+    auto call_iter = tail_call_block->findInstIterator(callInst);
+    SysYIROptUtils::usedelete(call_iter);
+
+  // 添加跳转回循环头块的分支指令
+    builder->setPosition(tail_call_block, tail_call_block->end());
+    builder->createUncondBrInst(loop_header);
+    tail_call_block->addSuccessor(loop_header);
+    loop_header->addPredecessor(tail_call_block);
+  }
+
+  return true;
+}
+
+} // namespace sysy

src/midend/Pass/Pass.cpp

@@ -19,6 +19,7 @@
 #include "LoopStrengthReduction.h"
 #include "InductionVariableElimination.h"
 #include "GlobalStrengthReduction.h"
+#include "TailCallOpt.h"
 #include "Pass.h"
 #include <iostream>
 #include <queue>
@@ -81,6 +82,7 @@ void PassManager::runOptimizationPipeline(Module* moduleIR, IRBuilder* builderIR
 
     registerOptimizationPass<GlobalStrengthReduction>(builderIR);
     registerOptimizationPass<Reg2Mem>(builderIR);
+    registerOptimizationPass<TailCallOpt>(builderIR);
 
     registerOptimizationPass<SCCP>(builderIR);
 
@@ -139,6 +141,16 @@ void PassManager::runOptimizationPipeline(Module* moduleIR, IRBuilder* builderIR
       this->addPass(&GVN::ID);
       this->run();
 
+      this->clearPasses();
+      this->addPass(&TailCallOpt::ID);
+      this->run();
+
+      if(DEBUG) {
+        std::cout << "=== IR After TailCallOpt ===\n";
+        SysYPrinter printer(moduleIR);
+        printer.printIR();
+      }
+
       if(DEBUG) {
         std::cout << "=== IR After GVN Optimizations ===\n";
         printPasses();
@@ -192,9 +204,9 @@ void PassManager::runOptimizationPipeline(Module* moduleIR, IRBuilder* builderIR
         printPasses();
       }
 
-      // this->clearPasses();
-      // this->addPass(&Reg2Mem::ID);
-      // this->run();
+      this->clearPasses();
+      this->addPass(&Reg2Mem::ID);
+      this->run();
 
       if(DEBUG) {
         std::cout << "=== IR After Reg2Mem Optimizations ===\n";