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diff --git a/unittests/IR/CFGBuilder.h b/unittests/IR/CFGBuilder.h
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+++ b/unittests/IR/CFGBuilder.h
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+//===- CFGBuilder.h - CFG building and updating utility ----------*- C++ -*-==//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+/// \file
+/// CFGBuilders provides utilities fo building and updating CFG for testing
+/// purposes.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_UNITTESTS_CFG_BUILDER_H
+#define LLVM_UNITTESTS_CFG_BUILDER_H
+
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/Optional.h"
+#include "llvm/ADT/StringMap.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Support/Debug.h"
+
+#include <memory>
+#include <set>
+#include <tuple>
+#include <vector>
+
+namespace llvm {
+
+class LLVMContext;
+class Module;
+class Function;
+class BasicBlock;
+class raw_ostream;
+
+struct CFGHolder {
+  std::unique_ptr<LLVMContext> Context;
+  std::unique_ptr<Module> M;
+  Function *F;
+
+  CFGHolder(StringRef ModuleName = "m", StringRef FunctionName = "foo");
+  ~CFGHolder(); // Defined in the .cpp file so we can use forward declarations.
+};
+
+/// \brief
+/// CFGBuilder builds IR with specific CFG, based on the supplied list of arcs.
+/// It's able to apply the provided updates and automatically modify the IR.
+///
+/// Internally it makes every basic block end with either SwitchInst or with
+/// UnreachableInst. When all arc to a BB are deleted, the BB remains in the
+/// function and doesn't get deleted.
+///
+class CFGBuilder {
+public:
+  struct Arc {
+    StringRef From;
+    StringRef To;
+
+    friend bool operator<(const Arc &LHS, const Arc &RHS) {
+      return std::tie(LHS.From, LHS.To) <
+             std::tie(RHS.From, RHS.To);
+    }
+  };
+
+  enum class ActionKind { Insert, Delete };
+  struct Update {
+    ActionKind Action;
+    Arc Edge;
+  };
+
+  CFGBuilder(Function *F, const std::vector<Arc> &InitialArcs,
+             std::vector<Update> Updates);
+
+  BasicBlock *getOrAddBlock(StringRef BlockName);
+  Optional<Update> getNextUpdate() const;
+  Optional<Update> applyUpdate();
+  void dump(raw_ostream &OS = dbgs()) const;
+
+private:
+  void buildCFG(const std::vector<Arc> &Arcs);
+  bool connect(const Arc &A);
+  bool disconnect(const Arc &A);
+
+  Function *F;
+  unsigned UpdateIdx = 0;
+  StringMap<BasicBlock *> NameToBlock;
+  std::set<Arc> Arcs;
+  std::vector<Update> Updates;
+};
+
+} // namespace llvm
+
+#endif