Revert "[CodeGen] Introduce MachineDomTreeUpdater" (#96846)

Reverts #95369
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Author: paperchalice

llvm/include/llvm/Analysis/DomTreeUpdater.h

@@ -15,8 +15,6 @@
 #define LLVM_ANALYSIS_DOMTREEUPDATER_H
 
 #include "llvm/ADT/SmallPtrSet.h"
-#include "llvm/Analysis/GenericDomTreeUpdater.h"
-#include "llvm/Analysis/PostDominators.h"
 #include "llvm/IR/Dominators.h"
 #include "llvm/IR/ValueHandle.h"
 #include "llvm/Support/Compiler.h"
@@ -25,17 +23,66 @@
 #include <vector>
 
 namespace llvm {
+class PostDominatorTree;
 
-class DomTreeUpdater
-    : public GenericDomTreeUpdater<DomTreeUpdater, DominatorTree,
-                                   PostDominatorTree> {
-  friend GenericDomTreeUpdater<DomTreeUpdater, DominatorTree,
-                               PostDominatorTree>;
-
+class DomTreeUpdater {
 public:
-  using Base =
-      GenericDomTreeUpdater<DomTreeUpdater, DominatorTree, PostDominatorTree>;
-  using Base::Base;
+  enum class UpdateStrategy : unsigned char { Eager = 0, Lazy = 1 };
+
+  explicit DomTreeUpdater(UpdateStrategy Strategy_) : Strategy(Strategy_) {}
+  DomTreeUpdater(DominatorTree &DT_, UpdateStrategy Strategy_)
+      : DT(&DT_), Strategy(Strategy_) {}
+  DomTreeUpdater(DominatorTree *DT_, UpdateStrategy Strategy_)
+      : DT(DT_), Strategy(Strategy_) {}
+  DomTreeUpdater(PostDominatorTree &PDT_, UpdateStrategy Strategy_)
+      : PDT(&PDT_), Strategy(Strategy_) {}
+  DomTreeUpdater(PostDominatorTree *PDT_, UpdateStrategy Strategy_)
+      : PDT(PDT_), Strategy(Strategy_) {}
+  DomTreeUpdater(DominatorTree &DT_, PostDominatorTree &PDT_,
+                 UpdateStrategy Strategy_)
+      : DT(&DT_), PDT(&PDT_), Strategy(Strategy_) {}
+  DomTreeUpdater(DominatorTree *DT_, PostDominatorTree *PDT_,
+                 UpdateStrategy Strategy_)
+      : DT(DT_), PDT(PDT_), Strategy(Strategy_) {}
+
+  ~DomTreeUpdater() { flush(); }
+
+  /// Returns true if the current strategy is Lazy.
+  bool isLazy() const { return Strategy == UpdateStrategy::Lazy; };
+
+  /// Returns true if the current strategy is Eager.
+  bool isEager() const { return Strategy == UpdateStrategy::Eager; };
+
+  /// Returns true if it holds a DominatorTree.
+  bool hasDomTree() const { return DT != nullptr; }
+
+  /// Returns true if it holds a PostDominatorTree.
+  bool hasPostDomTree() const { return PDT != nullptr; }
+
+  /// Returns true if there is BasicBlock awaiting deletion.
+  /// The deletion will only happen until a flush event and
+  /// all available trees are up-to-date.
+  /// Returns false under Eager UpdateStrategy.
+  bool hasPendingDeletedBB() const { return !DeletedBBs.empty(); }
+
+  /// Returns true if DelBB is awaiting deletion.
+  /// Returns false under Eager UpdateStrategy.
+  bool isBBPendingDeletion(BasicBlock *DelBB) const;
+
+  /// Returns true if either of DT or PDT is valid and the tree has at
+  /// least one update pending. If DT or PDT is nullptr it is treated
+  /// as having no pending updates. This function does not check
+  /// whether there is BasicBlock awaiting deletion.
+  /// Returns false under Eager UpdateStrategy.
+  bool hasPendingUpdates() const;
+
+  /// Returns true if there are DominatorTree updates queued.
+  /// Returns false under Eager UpdateStrategy or DT is nullptr.
+  bool hasPendingDomTreeUpdates() const;
+
+  /// Returns true if there are PostDominatorTree updates queued.
+  /// Returns false under Eager UpdateStrategy or PDT is nullptr.
+  bool hasPendingPostDomTreeUpdates() const;
 
   ///@{
   /// \name Mutation APIs
@@ -58,6 +105,51 @@ class DomTreeUpdater
   /// Although GenericDomTree provides several update primitives,
   /// it is not encouraged to use these APIs directly.
 
+  /// Submit updates to all available trees.
+  /// The Eager Strategy flushes updates immediately while the Lazy Strategy
+  /// queues the updates.
+  ///
+  /// Note: The "existence" of an edge in a CFG refers to the CFG which DTU is
+  /// in sync with + all updates before that single update.
+  ///
+  /// CAUTION!
+  /// 1. It is required for the state of the LLVM IR to be updated
+  /// *before* submitting the updates because the internal update routine will
+  /// analyze the current state of the CFG to determine whether an update
+  /// is valid.
+  /// 2. It is illegal to submit any update that has already been submitted,
+  /// i.e., you are supposed not to insert an existent edge or delete a
+  /// nonexistent edge.
+  void applyUpdates(ArrayRef<DominatorTree::UpdateType> Updates);
+
+  /// Submit updates to all available trees. It will also
+  /// 1. discard duplicated updates,
+  /// 2. remove invalid updates. (Invalid updates means deletion of an edge that
+  /// still exists or insertion of an edge that does not exist.)
+  /// The Eager Strategy flushes updates immediately while the Lazy Strategy
+  /// queues the updates.
+  ///
+  /// Note: The "existence" of an edge in a CFG refers to the CFG which DTU is
+  /// in sync with + all updates before that single update.
+  ///
+  /// CAUTION!
+  /// 1. It is required for the state of the LLVM IR to be updated
+  /// *before* submitting the updates because the internal update routine will
+  /// analyze the current state of the CFG to determine whether an update
+  /// is valid.
+  /// 2. It is illegal to submit any update that has already been submitted,
+  /// i.e., you are supposed not to insert an existent edge or delete a
+  /// nonexistent edge.
+  /// 3. It is only legal to submit updates to an edge in the order CFG changes
+  /// are made. The order you submit updates on different edges is not
+  /// restricted.
+  void applyUpdatesPermissive(ArrayRef<DominatorTree::UpdateType> Updates);
+
+  /// Notify DTU that the entry block was replaced.
+  /// Recalculate all available trees and flush all BasicBlocks
+  /// awaiting deletion immediately.
+  void recalculate(Function &F);
+
   /// Delete DelBB. DelBB will be removed from its Parent and
   /// erased from available trees if it exists and finally get deleted.
   /// Under Eager UpdateStrategy, DelBB will be processed immediately.
@@ -80,6 +172,33 @@ class DomTreeUpdater
 
   ///@}
 
+  ///@{
+  /// \name Flush APIs
+  ///
+  /// CAUTION! By the moment these flush APIs are called, the current CFG needs
+  /// to be the same as the CFG which DTU is in sync with + all updates
+  /// submitted.
+
+  /// Flush DomTree updates and return DomTree.
+  /// It flushes Deleted BBs if both trees are up-to-date.
+  /// It must only be called when it has a DomTree.
+  DominatorTree &getDomTree();
+
+  /// Flush PostDomTree updates and return PostDomTree.
+  /// It flushes Deleted BBs if both trees are up-to-date.
+  /// It must only be called when it has a PostDomTree.
+  PostDominatorTree &getPostDomTree();
+
+  /// Apply all pending updates to available trees and flush all BasicBlocks
+  /// awaiting deletion.
+
+  void flush();
+
+  ///@}
+
+  /// Debug method to help view the internal state of this class.
+  LLVM_DUMP_METHOD void dump() const;
+
 private:
   class CallBackOnDeletion final : public CallbackVH {
   public:
@@ -97,7 +216,16 @@ class DomTreeUpdater
     }
   };
 
+  SmallVector<DominatorTree::UpdateType, 16> PendUpdates;
+  size_t PendDTUpdateIndex = 0;
+  size_t PendPDTUpdateIndex = 0;
+  DominatorTree *DT = nullptr;
+  PostDominatorTree *PDT = nullptr;
+  const UpdateStrategy Strategy;
+  SmallPtrSet<BasicBlock *, 8> DeletedBBs;
   std::vector<CallBackOnDeletion> Callbacks;
+  bool IsRecalculatingDomTree = false;
+  bool IsRecalculatingPostDomTree = false;
 
   /// First remove all the instructions of DelBB and then make sure DelBB has a
   /// valid terminator instruction which is necessary to have when DelBB still
@@ -109,28 +237,32 @@ class DomTreeUpdater
   /// Returns true if at least one BasicBlock is deleted.
   bool forceFlushDeletedBB();
 
-  /// Debug method to help view the internal state of this class.
-  LLVM_DUMP_METHOD void dump() const {
-    Base::dump();
-#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
-    raw_ostream &OS = dbgs();
-    OS << "Pending Callbacks:\n";
-    int Index = 0;
-    for (const auto &BB : Callbacks) {
-      OS << "  " << Index << " : ";
-      ++Index;
-      if (BB->hasName())
-        OS << BB->getName() << "(";
-      else
-        OS << "(no_name)(";
-      OS << BB << ")\n";
-    }
-#endif
-  }
-};
+  /// Helper function to apply all pending DomTree updates.
+  void applyDomTreeUpdates();
+
+  /// Helper function to apply all pending PostDomTree updates.
+  void applyPostDomTreeUpdates();
+
+  /// Helper function to flush deleted BasicBlocks if all available
+  /// trees are up-to-date.
+  void tryFlushDeletedBB();
 
-extern template class GenericDomTreeUpdater<DomTreeUpdater, DominatorTree,
-                                            PostDominatorTree>;
+  /// Drop all updates applied by all available trees and delete BasicBlocks if
+  /// all available trees are up-to-date.
+  void dropOutOfDateUpdates();
+
+  /// Erase Basic Block node that has been unlinked from Function
+  /// in the DomTree and PostDomTree.
+  void eraseDelBBNode(BasicBlock *DelBB);
+
+  /// Returns true if the update appears in the LLVM IR.
+  /// It is used to check whether an update is valid in
+  /// insertEdge/deleteEdge or is unnecessary in the batch update.
+  bool isUpdateValid(DominatorTree::UpdateType Update) const;
+
+  /// Returns true if the update is self dominance.
+  bool isSelfDominance(DominatorTree::UpdateType Update) const;
+};
 } // namespace llvm
 
 #endif // LLVM_ANALYSIS_DOMTREEUPDATER_H