Add cache in GenericCycleInfo

Author: Chengjunp

llvm/include/llvm/ADT/GenericCycleImpl.h

@@ -47,6 +47,11 @@ bool GenericCycle<ContextT>::contains(const GenericCycle *C) const {
 template <typename ContextT>
 void GenericCycle<ContextT>::getExitBlocks(
     SmallVectorImpl<BlockT *> &TmpStorage) const {
+  if (!ExitBlocksCache->empty()) {
+    TmpStorage = *ExitBlocksCache;
+    return;
+  }
+
   TmpStorage.clear();
 
   size_t NumExitBlocks = 0;
@@ -65,6 +70,7 @@ void GenericCycle<ContextT>::getExitBlocks(
 
     TmpStorage.resize(NumExitBlocks);
   }
+  ExitBlocksCache->append(TmpStorage.begin(), TmpStorage.end());
 }
 
 template <typename ContextT>

llvm/include/llvm/ADT/GenericCycleInfo.h

@@ -74,12 +74,16 @@ template <typename ContextT> class GenericCycle {
   ///       always have the same depth.
   unsigned Depth = 0;
 
+  /// Cache for the results of GetExitBlocks
+  std::unique_ptr<SmallVector<BlockT *, 4>> ExitBlocksCache;
+
   void clear() {
     Entries.clear();
     Children.clear();
     Blocks.clear();
     Depth = 0;
     ParentCycle = nullptr;
+    ExitBlocksCache->clear();
   }
 
   void appendEntry(BlockT *Block) { Entries.push_back(Block); }
@@ -91,7 +95,8 @@ template <typename ContextT> class GenericCycle {
   GenericCycle &operator=(GenericCycle &&Rhs) = delete;
 
 public:
-  GenericCycle() = default;
+  GenericCycle()
+      : ExitBlocksCache(std::make_unique<SmallVector<BlockT *, 4>>()){};
 
   /// \brief Whether the cycle is a natural loop.
   bool isReducible() const { return Entries.size() == 1; }