[midend-IVE]增加无用归纳变量消除遍

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

@@ -0,0 +1,157 @@
+#pragma once
+
+#include "Pass.h"
+#include "IR.h"
+#include "LoopCharacteristics.h"
+#include "Loop.h"
+#include "Dom.h"
+#include "SideEffectAnalysis.h"
+#include <vector>
+#include <unordered_map>
+#include <unordered_set>
+#include <memory>
+
+namespace sysy {
+
+// 前向声明
+class LoopCharacteristicsResult;
+class LoopAnalysisResult;
+
+/**
+ * @brief 死归纳变量信息
+ * 记录一个可以被消除的归纳变量
+ */
+struct DeadInductionVariable {
+  PhiInst* phiInst;                    // phi 指令
+  std::vector<Instruction*> relatedInsts; // 相关的递增/递减指令
+  Loop* containingLoop;                // 所在循环
+  bool canEliminate;                   // 是否可以安全消除
+  
+  DeadInductionVariable(PhiInst* phi, Loop* loop) 
+    : phiInst(phi), containingLoop(loop), canEliminate(false) {}
+};
+
+/**
+ * @brief 归纳变量消除上下文类
+ * 封装归纳变量消除优化的核心逻辑和状态
+ */
+class InductionVariableEliminationContext {
+public:
+  InductionVariableEliminationContext() {}
+  
+  /**
+   * 运行归纳变量消除优化
+   * @param F 目标函数
+   * @param AM 分析管理器
+   * @return 是否修改了IR
+   */
+  bool run(Function* F, AnalysisManager& AM);
+
+private:
+  // 分析结果缓存
+  LoopAnalysisResult* loopAnalysis = nullptr;
+  LoopCharacteristicsResult* loopCharacteristics = nullptr;
+  DominatorTree* dominatorTree = nullptr;
+  SideEffectAnalysisResult* sideEffectAnalysis = nullptr;
+  
+  // 死归纳变量存储
+  std::vector<std::unique_ptr<DeadInductionVariable>> deadIVs;
+  std::unordered_map<Loop*, std::vector<DeadInductionVariable*>> loopToDeadIVs;
+  
+  // ========== 核心分析和优化阶段 ==========
+  
+  /**
+   * 阶段1：识别死归纳变量
+   * 找出没有被有效使用的归纳变量
+   */
+  void identifyDeadInductionVariables(Function* F);
+  
+  /**
+   * 阶段2：分析消除的安全性
+   * 确保消除操作不会破坏程序语义
+   */
+  void analyzeSafetyForElimination();
+  
+  /**
+   * 阶段3：执行归纳变量消除
+   * 删除死归纳变量及其相关指令
+   */
+  bool performInductionVariableElimination();
+  
+  // ========== 辅助方法 ==========
+  
+  /**
+   * 检查归纳变量是否为死归纳变量
+   * @param iv 归纳变量信息
+   * @param loop 所在循环
+   * @return 如果是死归纳变量返回相关信息，否则返回nullptr
+   */
+  std::unique_ptr<DeadInductionVariable> 
+  isDeadInductionVariable(const InductionVarInfo* iv, Loop* loop);
+  
+  /**
+   * 检查归纳变量是否只用于自身更新
+   * @param phiInst phi指令
+   * @param loop 所在循环
+   * @return 是否只用于自身更新
+   */
+  bool isUsedOnlyForSelfUpdate(PhiInst* phiInst, Loop* loop);
+  
+  /**
+   * 收集与归纳变量相关的所有指令
+   * @param phiInst phi指令
+   * @param loop 所在循环
+   * @return 相关指令列表
+   */
+  std::vector<Instruction*> collectRelatedInstructions(PhiInst* phiInst, Loop* loop);
+  
+  /**
+   * 检查消除归纳变量的安全性
+   * @param deadIV 死归纳变量
+   * @return 是否可以安全消除
+   */
+  bool isSafeToEliminate(const DeadInductionVariable* deadIV);
+  
+  /**
+   * 消除单个死归纳变量
+   * @param deadIV 死归纳变量
+   * @return 是否成功消除
+   */
+  bool eliminateDeadInductionVariable(DeadInductionVariable* deadIV);
+  
+  /**
+   * 打印调试信息
+   */
+  void printDebugInfo();
+};
+
+/**
+ * @brief 归纳变量消除优化遍
+ * 消除循环中无用的归纳变量，减少寄存器压力
+ */
+class InductionVariableElimination : public OptimizationPass {
+public:
+  // 唯一的 Pass ID
+  static void *ID;
+  
+  InductionVariableElimination() 
+    : OptimizationPass("InductionVariableElimination", Granularity::Function) {}
+  
+  /**
+   * 在函数上运行归纳变量消除优化
+   * @param F 目标函数
+   * @param AM 分析管理器
+   * @return 是否修改了IR
+   */
+  bool runOnFunction(Function* F, AnalysisManager& AM) override;
+  
+  /**
+   * 声明分析依赖和失效信息
+   */
+  void getAnalysisUsage(std::set<void*>& analysisDependencies, 
+                       std::set<void*>& analysisInvalidations) const override;
+  
+  void* getPassID() const override { return &ID; }
+};
+
+} // namespace sysy

src/midend/CMakeLists.txt

@@ -20,6 +20,7 @@ add_library(midend_lib STATIC
     Pass/Optimize/LoopNormalization.cpp
     Pass/Optimize/LICM.cpp
     Pass/Optimize/LoopStrengthReduction.cpp
+    Pass/Optimize/InductionVariableElimination.cpp
     Pass/Optimize/BuildCFG.cpp
     Pass/Optimize/LargeArrayToGlobal.cpp
 )

src/midend/Pass/Optimize/InductionVariableElimination.cpp

@@ -0,0 +1,433 @@
+#include "InductionVariableElimination.h"
+#include "LoopCharacteristics.h"
+#include "Loop.h"
+#include "Dom.h"
+#include "SideEffectAnalysis.h"
+#include "SysYIROptUtils.h"
+#include <iostream>
+#include <algorithm>
+
+// 使用全局调试开关
+extern int DEBUG;
+
+namespace sysy {
+
+// 定义 Pass 的唯一 ID
+void *InductionVariableElimination::ID = (void *)&InductionVariableElimination::ID;
+
+bool InductionVariableElimination::runOnFunction(Function* F, AnalysisManager& AM) {
+  if (F->getBasicBlocks().empty()) {
+    return false; // 空函数
+  }
+
+  if (DEBUG) {
+    std::cout << "Running InductionVariableElimination on function: " << F->getName() << std::endl;
+  }
+
+  // 创建优化上下文并运行
+  InductionVariableEliminationContext context;
+  bool modified = context.run(F, AM);
+
+  if (DEBUG) {
+    std::cout << "InductionVariableElimination " << (modified ? "modified" : "did not modify") 
+              << " function: " << F->getName() << std::endl;
+  }
+
+  return modified;
+}
+
+void InductionVariableElimination::getAnalysisUsage(std::set<void*>& analysisDependencies, 
+                                                   std::set<void*>& analysisInvalidations) const {
+  // 依赖的分析
+  analysisDependencies.insert(&LoopAnalysisPass::ID);
+  analysisDependencies.insert(&LoopCharacteristicsPass::ID);
+  analysisDependencies.insert(&DominatorTreeAnalysisPass::ID);
+  analysisDependencies.insert(&SysYSideEffectAnalysisPass::ID);
+  
+  // 会使失效的分析（归纳变量消除会修改IR结构）
+  analysisInvalidations.insert(&LoopCharacteristicsPass::ID);
+  // 注意：支配树分析通常不会因为归纳变量消除而失效，因为我们不改变控制流
+}
+
+// ========== InductionVariableEliminationContext 实现 ==========
+
+bool InductionVariableEliminationContext::run(Function* F, AnalysisManager& AM) {
+  if (DEBUG) {
+    std::cout << "  Starting induction variable elimination analysis..." << std::endl;
+  }
+
+  // 获取必要的分析结果
+  loopAnalysis = AM.getAnalysisResult<LoopAnalysisResult, LoopAnalysisPass>(F);
+  if (!loopAnalysis || !loopAnalysis->hasLoops()) {
+    if (DEBUG) {
+      std::cout << "  No loops found, skipping induction variable elimination" << std::endl;
+    }
+    return false;
+  }
+
+  loopCharacteristics = AM.getAnalysisResult<LoopCharacteristicsResult, LoopCharacteristicsPass>(F);
+  if (!loopCharacteristics) {
+    if (DEBUG) {
+      std::cout << "  LoopCharacteristics analysis not available" << std::endl;
+    }
+    return false;
+  }
+
+  dominatorTree = AM.getAnalysisResult<DominatorTree, DominatorTreeAnalysisPass>(F);
+  if (!dominatorTree) {
+    if (DEBUG) {
+      std::cout << "  DominatorTree analysis not available" << std::endl;
+    }
+    return false;
+  }
+
+  sideEffectAnalysis = AM.getAnalysisResult<SideEffectAnalysisResult, SysYSideEffectAnalysisPass>();
+  if (!sideEffectAnalysis) {
+    if (DEBUG) {
+      std::cout << "  SideEffectAnalysis not available, using conservative approach" << std::endl;
+    }
+    // 可以继续执行，但会使用更保守的策略
+  } else {
+    if (DEBUG) {
+      std::cout << "  Using SideEffectAnalysis for safety checks" << std::endl;
+    }
+  }
+
+  // 执行三个阶段的优化
+  
+  // 阶段1：识别死归纳变量
+  identifyDeadInductionVariables(F);
+  
+  if (deadIVs.empty()) {
+    if (DEBUG) {
+      std::cout << "  No dead induction variables found" << std::endl;
+    }
+    return false;
+  }
+
+  if (DEBUG) {
+    std::cout << "  Found " << deadIVs.size() << " potentially dead induction variables" << std::endl;
+  }
+
+  // 阶段2：分析安全性
+  analyzeSafetyForElimination();
+
+  // 阶段3：执行消除
+  bool modified = performInductionVariableElimination();
+
+  if (DEBUG) {
+    printDebugInfo();
+  }
+
+  return modified;
+}
+
+void InductionVariableEliminationContext::identifyDeadInductionVariables(Function* F) {
+  if (DEBUG) {
+    std::cout << "  === Phase 1: Identifying Dead Induction Variables ===" << std::endl;
+  }
+
+  // 遍历所有循环
+  for (const auto& loop_ptr : loopAnalysis->getAllLoops()) {
+    Loop* loop = loop_ptr.get();
+    
+    if (DEBUG) {
+      std::cout << "    Analyzing loop: " << loop->getName() << std::endl;
+    }
+
+    // 获取循环特征
+    const LoopCharacteristics* characteristics = loopCharacteristics->getCharacteristics(loop);
+    if (!characteristics) {
+      if (DEBUG) {
+        std::cout << "      No characteristics available for loop" << std::endl;
+      }
+      continue;
+    }
+
+    if (characteristics->InductionVars.empty()) {
+      if (DEBUG) {
+        std::cout << "      No induction variables found in loop" << std::endl;
+      }
+      continue;
+    }
+
+    // 检查每个归纳变量是否为死归纳变量
+    for (const auto& iv : characteristics->InductionVars) {
+      auto deadIV = isDeadInductionVariable(iv.get(), loop);
+      if (deadIV) {
+        if (DEBUG) {
+          std::cout << "      Found potential dead IV: %" << deadIV->phiInst->getName() << std::endl;
+        }
+        
+        // 添加到候选项列表
+        loopToDeadIVs[loop].push_back(deadIV.get());
+        deadIVs.push_back(std::move(deadIV));
+      }
+    }
+  }
+
+  if (DEBUG) {
+    std::cout << "  === End Phase 1: Found " << deadIVs.size() << " candidates ===" << std::endl;
+  }
+}
+
+std::unique_ptr<DeadInductionVariable> 
+InductionVariableEliminationContext::isDeadInductionVariable(const InductionVarInfo* iv, Loop* loop) {
+  // 获取 phi 指令
+  auto* phiInst = dynamic_cast<PhiInst*>(iv->div);
+  if (!phiInst) {
+    return nullptr; // 不是 phi 指令
+  }
+
+  // 检查是否只用于自身更新
+  if (!isUsedOnlyForSelfUpdate(phiInst, loop)) {
+    return nullptr; // 有其他用途
+  }
+
+  // 创建死归纳变量信息
+  auto deadIV = std::make_unique<DeadInductionVariable>(phiInst, loop);
+  deadIV->relatedInsts = collectRelatedInstructions(phiInst, loop);
+  
+  return deadIV;
+}
+
+bool InductionVariableEliminationContext::isUsedOnlyForSelfUpdate(PhiInst* phiInst, Loop* loop) {
+  // 检查 phi 指令的所有使用
+  for (auto use : phiInst->getUses()) {
+    auto user = use->getUser();
+    auto* userInst = dynamic_cast<Instruction*>(user);
+    
+    if (!userInst) {
+      return false; // 被非指令使用
+    }
+    
+    // 检查使用是否在循环内
+    if (!loop->contains(userInst->getParent())) {
+      return false; // 在循环外被使用
+    }
+    
+    // 检查是否为自身的更新指令
+    bool isSelfUpdate = false;
+    
+    // 检查是否为加法/减法指令（常见的归纳变量更新模式）
+    if (userInst->getKind() == Instruction::Kind::kAdd || 
+        userInst->getKind() == Instruction::Kind::kSub) {
+      auto* binInst = dynamic_cast<BinaryInst*>(userInst);
+      if (binInst && (binInst->getOperand(0) == phiInst || binInst->getOperand(1) == phiInst)) {
+        // 检查这个指令的结果是否流回到 phi
+        for (auto& [incomingBB, incomingVal] : phiInst->getIncomingValues()) {
+          if (loop->contains(incomingBB) && incomingVal == binInst) {
+            isSelfUpdate = true;
+            break;
+          }
+        }
+      }
+    }
+    
+    if (!isSelfUpdate) {
+      return false; // 有非自更新的使用
+    }
+  }
+  
+  return true; // 只用于自身更新
+}
+
+std::vector<Instruction*> InductionVariableEliminationContext::collectRelatedInstructions(
+    PhiInst* phiInst, Loop* loop) {
+  std::vector<Instruction*> relatedInsts;
+  
+  // 收集所有与该归纳变量相关的指令
+  for (auto use : phiInst->getUses()) {
+    auto user = use->getUser();
+    auto* userInst = dynamic_cast<Instruction*>(user);
+    
+    if (userInst && loop->contains(userInst->getParent())) {
+      relatedInsts.push_back(userInst);
+    }
+  }
+  
+  return relatedInsts;
+}
+
+void InductionVariableEliminationContext::analyzeSafetyForElimination() {
+  if (DEBUG) {
+    std::cout << "  === Phase 2: Analyzing Safety for Elimination ===" << std::endl;
+  }
+
+  // 为每个死归纳变量检查消除的安全性
+  for (auto& deadIV : deadIVs) {
+    bool isSafe = isSafeToEliminate(deadIV.get());
+    deadIV->canEliminate = isSafe;
+    
+    if (DEBUG) {
+      std::cout << "    Dead IV " << deadIV->phiInst->getName() 
+                << ": " << (isSafe ? "SAFE" : "UNSAFE") << " to eliminate" << std::endl;
+    }
+  }
+
+  if (DEBUG) {
+    size_t safeCount = 0;
+    for (const auto& deadIV : deadIVs) {
+      if (deadIV->canEliminate) safeCount++;
+    }
+    std::cout << "  === End Phase 2: " << safeCount << " of " << deadIVs.size() 
+              << " variables are safe to eliminate ===" << std::endl;
+  }
+}
+
+bool InductionVariableEliminationContext::isSafeToEliminate(const DeadInductionVariable* deadIV) {
+  // 1. 确保归纳变量在循环头
+  if (deadIV->phiInst->getParent() != deadIV->containingLoop->getHeader()) {
+    if (DEBUG) {
+      std::cout << "      Unsafe: phi not in loop header" << std::endl;
+    }
+    return false;
+  }
+  
+  // 2. 确保相关指令都在循环内
+  for (auto* inst : deadIV->relatedInsts) {
+    if (!deadIV->containingLoop->contains(inst->getParent())) {
+      if (DEBUG) {
+        std::cout << "      Unsafe: related instruction outside loop" << std::endl;
+      }
+      return false;
+    }
+  }
+  
+  // 3. 确保没有副作用
+  for (auto* inst : deadIV->relatedInsts) {
+    if (sideEffectAnalysis) {
+      // 使用副作用分析进行精确检查
+      if (sideEffectAnalysis->hasSideEffect(inst)) {
+        if (DEBUG) {
+          std::cout << "      Unsafe: related instruction " << inst->getName() 
+                    << " has side effects" << std::endl;
+        }
+        return false;
+      }
+    } else {
+      // 没有副作用分析时使用保守策略：只允许基本算术运算
+      auto kind = inst->getKind();
+      if (kind != Instruction::Kind::kAdd && 
+          kind != Instruction::Kind::kSub &&
+          kind != Instruction::Kind::kMul) {
+        if (DEBUG) {
+          std::cout << "      Unsafe: related instruction may have side effects (conservative)" << std::endl;
+        }
+        return false;
+      }
+    }
+  }
+  
+  // 4. 确保不影响循环的退出条件
+  for (BasicBlock* exitingBB : deadIV->containingLoop->getExitingBlocks()) {
+    auto terminatorIt = exitingBB->terminator();
+    if (terminatorIt != exitingBB->end()) {
+      Instruction* terminator = terminatorIt->get();
+      if (terminator) {
+        for (size_t i = 0; i < terminator->getNumOperands(); ++i) {
+          if (terminator->getOperand(i) == deadIV->phiInst) {
+            if (DEBUG) {
+              std::cout << "      Unsafe: phi used in loop exit condition" << std::endl;
+            }
+            return false;
+          }
+        }
+      }
+    }
+  }
+  
+  return true;
+}
+
+bool InductionVariableEliminationContext::performInductionVariableElimination() {
+  if (DEBUG) {
+    std::cout << "  === Phase 3: Performing Induction Variable Elimination ===" << std::endl;
+  }
+
+  bool modified = false;
+
+  for (auto& deadIV : deadIVs) {
+    if (!deadIV->canEliminate) {
+      continue;
+    }
+
+    if (DEBUG) {
+      std::cout << "    Eliminating dead IV: " << deadIV->phiInst->getName() << std::endl;
+    }
+
+    if (eliminateDeadInductionVariable(deadIV.get())) {
+      if (DEBUG) {
+        std::cout << "      Successfully eliminated: " << deadIV->phiInst->getName() << std::endl;
+      }
+      modified = true;
+    } else {
+      if (DEBUG) {
+        std::cout << "      Failed to eliminate: " << deadIV->phiInst->getName() << std::endl;
+      }
+    }
+  }
+
+  if (DEBUG) {
+    std::cout << "  === End Phase 3: " << (modified ? "Eliminations performed" : "No eliminations") << " ===" << std::endl;
+  }
+
+  return modified;
+}
+
+bool InductionVariableEliminationContext::eliminateDeadInductionVariable(DeadInductionVariable* deadIV) {
+  // 1. 删除所有相关指令
+  for (auto* inst : deadIV->relatedInsts) {
+    auto* bb = inst->getParent();
+    auto it = bb->findInstIterator(inst);
+    if (it != bb->end()) {
+        SysYIROptUtils::usedelete(it);
+    //   bb->getInstructions().erase(it);
+      if (DEBUG) {
+        std::cout << "        Removed related instruction: " << inst->getName() << std::endl;
+      }
+    }
+  }
+
+  // 2. 删除 phi 指令
+  auto* bb = deadIV->phiInst->getParent();
+  auto it = bb->findInstIterator(deadIV->phiInst);
+  if (it != bb->end()) {
+    SysYIROptUtils::usedelete(it);
+    // bb->getInstructions().erase(it);
+    if (DEBUG) {
+      std::cout << "        Removed phi instruction: " << deadIV->phiInst->getName() << std::endl;
+    }
+    return true;
+  }
+
+  return false;
+}
+
+void InductionVariableEliminationContext::printDebugInfo() {
+  if (!DEBUG) return;
+
+  std::cout << "\n=== Induction Variable Elimination Summary ===" << std::endl;
+  std::cout << "Total dead IVs found: " << deadIVs.size() << std::endl;
+  
+  size_t eliminatedCount = 0;
+  for (auto& [loop, loopDeadIVs] : loopToDeadIVs) {
+    size_t loopEliminatedCount = 0;
+    for (auto* deadIV : loopDeadIVs) {
+      if (deadIV->canEliminate) {
+        loopEliminatedCount++;
+        eliminatedCount++;
+      }
+    }
+    
+    if (loopEliminatedCount > 0) {
+      std::cout << "Loop " << loop->getName() << ": " << loopEliminatedCount 
+                << " of " << loopDeadIVs.size() << " IVs eliminated" << std::endl;
+    }
+  }
+  
+  std::cout << "Total eliminated: " << eliminatedCount << " of " << deadIVs.size() << std::endl;
+  std::cout << "=============================================" << std::endl;
+}
+
+} // namespace sysy

src/midend/Pass/Pass.cpp

@@ -16,6 +16,7 @@
 #include "LoopNormalization.h"
 #include "LICM.h"
 #include "LoopStrengthReduction.h"
+#include "InductionVariableElimination.h"
 #include "Pass.h"
 #include <iostream>
 #include <queue>
@@ -72,6 +73,7 @@ void PassManager::runOptimizationPipeline(Module* moduleIR, IRBuilder* builderIR
     registerOptimizationPass<LoopNormalizationPass>(builderIR);
     registerOptimizationPass<LICM>(builderIR);
     registerOptimizationPass<LoopStrengthReduction>(builderIR);
+    registerOptimizationPass<InductionVariableElimination>();
     registerOptimizationPass<Reg2Mem>(builderIR);
 
     registerOptimizationPass<SCCP>(builderIR);
@@ -140,6 +142,7 @@ void PassManager::runOptimizationPipeline(Module* moduleIR, IRBuilder* builderIR
       this->addPass(&LoopNormalizationPass::ID);
       this->addPass(&LICM::ID);
       this->addPass(&LoopStrengthReduction::ID);
+      this->addPass(&InductionVariableElimination::ID);
       this->run();
 
       if(DEBUG) {