[midend-LICM]将能够外提的循环不变量进行Kanh拓扑排序保证外提后的计算顺序正确。

src/midend/Pass/Optimize/LICM.cpp

@@ -12,33 +12,62 @@ bool LICMContext::run() { return hoistInstructions(); }
 bool LICMContext::hoistInstructions() {
   bool changed = false;
   BasicBlock *preheader = loop->getPreHeader();
-  if (!preheader || !chars){
-    if(DEBUG) {
-      std::cerr << "LICM: No preheader or loop characteristics found, skipping hoisting." << std::endl;
+  if (!preheader || !chars)
+    return false;
+
+  // 1. 先收集所有可外提指令
+  std::unordered_set<Instruction *> workSet(chars->invariantInsts.begin(), chars->invariantInsts.end());
+
+  // 2. 计算每个指令被依赖的次数（入度）
+  std::unordered_map<Instruction *, int> indegree;
+  for (auto *inst : workSet) {
+    indegree[inst] = 0;
+  }
+  for (auto *inst : workSet) {
+    for (size_t i = 0; i < inst->getNumOperands(); ++i) {
+      if (auto *dep = dynamic_cast<Instruction *>(inst->getOperand(i))) {
+        if (workSet.count(dep)) {
+          indegree[inst]++;
+        }
+      }
     }
+  }
+
+  // 3. Kahn拓扑排序
+  std::vector<Instruction *> sorted;
+  std::queue<Instruction *> q;
+  for (auto &[inst, deg] : indegree) {
+    if (deg == 0)
+      q.push(inst);
+  }
+  while (!q.empty()) {
+    auto *inst = q.front();
+    q.pop();
+    sorted.push_back(inst);
+    for (size_t i = 0; i < inst->getNumOperands(); ++i) {
+      if (auto *dep = dynamic_cast<Instruction *>(inst->getOperand(i))) {
+        if (workSet.count(dep)) {
+          indegree[dep]--;
+          if (indegree[dep] == 0)
+            q.push(dep);
+        }
+      }
+    }
+  }
+
+  // 检查是否全部排序，若未全部排序，说明有环（理论上不会）
+  if (sorted.size() != workSet.size()) {
+    if (DEBUG)
+      std::cerr << "LICM: Topological sort failed, possible dependency cycle." << std::endl;
     return false;
   }
-    
-  for (auto *inst : chars->invariantInsts) {
-    if (!inst) {
-      if(DEBUG) {
-        std::cerr << "LICM: Invalid instruction found, skipping." << std::endl;
-      }
-      continue; // 跳过无效指令
-    }
-    else{
-      if(DEBUG) {
-        std::cout << "LICM: Processing instruction " << inst->getName() << " for hoisting." << std::endl;
-      }
-    }
+
+  // 4. 按拓扑序外提
+  for (auto *inst : sorted) {
+    if (!inst)
+      continue;
     BasicBlock *parent = inst->getParent();
-    // 只外提当前还在循环体内的指令
     if (parent && loop->contains(parent)) {
-      // 获取源和槽的迭代器并移动指令到前置块
-      if(DEBUG) {
-        std::cout << "LICM: Hoisting instruction " << inst->getName() << " from " 
-                  << parent->getName() << " to preheader " << preheader->getName() << std::endl;
-      }
       auto sourcePos = parent->findInstIterator(inst);
       auto targetPos = preheader->terminator();
       parent->moveInst(sourcePos, targetPos, preheader);
@@ -47,7 +76,6 @@ bool LICMContext::hoistInstructions() {
   }
   return changed;
 }
-
 // ---- LICM Pass Implementation ----
 
 bool LICM::runOnFunction(Function *F, AnalysisManager &AM) {
@@ -60,7 +88,7 @@ bool LICM::runOnFunction(Function *F, AnalysisManager &AM) {
   // 对每个函数内的所有循环做处理
   for (const auto &loop_ptr : loopAnalysis->getAllLoops()) {
     Loop *loop = loop_ptr.get();
-    if(DEBUG){
+    if (DEBUG) {
       std::cout << "LICM: Processing loop in function " << F->getName() << ": " << loop->getName() << std::endl;
     }
     const LoopCharacteristics *chars = loopCharsResult->getCharacteristics(loop);