[midend]重构中端，建立遍管理器，注册器等，初步构建支配树分析遍，增加基本块方法

src/Dom.cpp

@@ -0,0 +1,181 @@
+#include "Dom.h"
+#include <limits> // for std::numeric_limits
+#include <queue>
+
+namespace sysy {
+
+// 初始化 支配树静态 ID
+char DominatorTreeAnalysisPass::ID = 0;
+
+// ==============================================================
+// DominatorTree 结果类的实现
+// ==============================================================
+
+DominatorTree::DominatorTree(Function *F) : AssociatedFunction(F) {
+  // 构造时可以不计算，在分析遍运行里计算并填充
+}
+
+const std::set<BasicBlock *> *DominatorTree::getDominators(BasicBlock *BB) const {
+  auto it = Dominators.find(BB);
+  if (it != Dominators.end()) {
+    return &(it->second);
+  }
+  return nullptr;
+}
+
+BasicBlock *DominatorTree::getImmediateDominator(BasicBlock *BB) const {
+  auto it = IDoms.find(BB);
+  if (it != IDoms.end()) {
+    return it->second;
+  }
+  return nullptr;
+}
+
+const std::set<BasicBlock *> *DominatorTree::getDominanceFrontier(BasicBlock *BB) const {
+  auto it = DominanceFrontiers.find(BB);
+  if (it != DominanceFrontiers.end()) {
+    return &(it->second);
+  }
+  return nullptr;
+}
+
+void DominatorTree::computeDominators(Function *F) {
+  // 经典的迭代算法计算支配者集合
+  // TODO: 可以替换为更高效的算法，如 Lengauer-Tarjan 算法
+  BasicBlock *entryBlock = F->getEntryBlock();
+
+  for (const auto &bb_ptr : F->getBasicBlocks()) {
+    BasicBlock *bb = bb_ptr.get();
+    if (bb == entryBlock) {
+      Dominators[bb].insert(bb);
+    } else {
+      for (const auto &all_bb_ptr : F->getBasicBlocks()) {
+        Dominators[bb].insert(all_bb_ptr.get());
+      }
+    }
+  }
+
+  bool changed = true;
+  while (changed) {
+    changed = false;
+    for (const auto &bb_ptr : F->getBasicBlocks()) {
+      BasicBlock *bb = bb_ptr.get();
+      if (bb == entryBlock)
+        continue;
+
+      std::set<BasicBlock *> newDom;
+      bool firstPred = true;
+      for (BasicBlock *pred : bb->getPredecessors()) {
+        if (Dominators.count(pred)) {
+          if (firstPred) {
+            newDom = Dominators[pred];
+            firstPred = false;
+          } else {
+            std::set<BasicBlock *> intersection;
+            std::set_intersection(newDom.begin(), newDom.end(), Dominators[pred].begin(), Dominators[pred].end(),
+                                  std::inserter(intersection, intersection.begin()));
+            newDom = intersection;
+          }
+        }
+      }
+      newDom.insert(bb);
+
+      if (newDom != Dominators[bb]) {
+        Dominators[bb] = newDom;
+        changed = true;
+      }
+    }
+  }
+}
+
+void DominatorTree::computeIDoms(Function *F) {
+  // 采用与之前类似的简化实现。TODO:Lengauer-Tarjan等算法。
+  BasicBlock *entryBlock = F->getEntryBlock();
+  IDoms[entryBlock] = nullptr;
+
+  for (const auto &bb_ptr : F->getBasicBlocks()) {
+    BasicBlock *bb = bb_ptr.get();
+    if (bb == entryBlock)
+      continue;
+
+    BasicBlock *currentIDom = nullptr;
+    const std::set<BasicBlock *> *domsOfBB = getDominators(bb);
+    if (!domsOfBB)
+      continue;
+
+    for (BasicBlock *D : *domsOfBB) {
+      if (D == bb)
+        continue;
+
+      bool isCandidateIDom = true;
+      for (BasicBlock *candidate : *domsOfBB) {
+        if (candidate == bb || candidate == D)
+          continue;
+        const std::set<BasicBlock *> *domsOfCandidate = getDominators(candidate);
+        if (domsOfCandidate && domsOfCandidate->count(D) == 0 && domsOfBB->count(candidate)) {
+          isCandidateIDom = false;
+          break;
+        }
+      }
+      if (isCandidateIDom) {
+        currentIDom = D;
+        break;
+      }
+    }
+    IDoms[bb] = currentIDom;
+  }
+}
+
+void DominatorTree::computeDominanceFrontiers(Function *F) {
+  // 经典的支配边界计算算法
+  for (const auto &bb_ptr_X : F->getBasicBlocks()) {
+    BasicBlock *X = bb_ptr_X.get();
+    DominanceFrontiers[X].clear();
+
+    for (BasicBlock *Y : X->getSuccessors()) {
+      const std::set<BasicBlock *> *domsOfY = getDominators(Y);
+      if (domsOfY && domsOfY->find(X) == domsOfY->end()) {
+        DominanceFrontiers[X].insert(Y);
+      }
+    }
+
+    const std::set<BasicBlock *> *domsOfX = getDominators(X);
+    if (!domsOfX)
+      continue;
+    for (const auto &bb_ptr_Z : F->getBasicBlocks()) {
+      BasicBlock *Z = bb_ptr_Z.get();
+      if (Z == X)
+        continue;
+      const std::set<BasicBlock *> *domsOfZ = getDominators(Z);
+      if (domsOfZ && domsOfZ->count(X) && Z != X) {
+
+        for (BasicBlock *Y : Z->getSuccessors()) {
+          const std::set<BasicBlock *> *domsOfY = getDominators(Y);
+          if (domsOfY && domsOfY->find(X) == domsOfY->end()) {
+            DominanceFrontiers[X].insert(Y);
+          }
+        }
+      }
+    }
+  }
+}
+
+// ==============================================================
+// DominatorTreeAnalysisPass 的实现
+// ==============================================================
+
+
+bool DominatorTreeAnalysisPass::runOnFunction(Function* F) {
+  CurrentDominatorTree = std::make_unique<DominatorTree>(F);
+  CurrentDominatorTree->computeDominators(F);
+  CurrentDominatorTree->computeIDoms(F);
+  CurrentDominatorTree->computeDominanceFrontiers(F);
+  return false;
+}
+
+std::unique_ptr<AnalysisResultBase> DominatorTreeAnalysisPass::getResult() {
+  // 返回计算好的 DominatorTree 实例，所有权转移给 AnalysisManager
+  return std::move(CurrentDominatorTree);
+}
+
+} // namespace sysy