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diff --git a/llvm/tools/llvm-exegesis/lib/InMemoryAssembler.h b/llvm/tools/llvm-exegesis/lib/InMemoryAssembler.h
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+//===-- InMemoryAssembler.h -------------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Defines classes to assemble functions composed of a single basic block of
+/// MCInsts.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TOOLS_LLVM_EXEGESIS_INMEMORYASSEMBLER_H
+#define LLVM_TOOLS_LLVM_EXEGESIS_INMEMORYASSEMBLER_H
+
+#include "llvm/ADT/BitVector.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineModuleInfo.h"
+#include "llvm/CodeGen/TargetRegisterInfo.h"
+#include "llvm/ExecutionEngine/ExecutionEngine.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/MC/MCInst.h"
+#include <cstdint>
+#include <memory>
+#include <vector>
+
+namespace exegesis {
+
+// Consumable context for JitFunction below.
+// This temporary object allows for retrieving MachineFunction properties before
+// assembling it.
+class JitFunctionContext {
+public:
+  explicit JitFunctionContext(std::unique_ptr<llvm::LLVMTargetMachine> TM);
+  // Movable
+  JitFunctionContext(JitFunctionContext &&) = default;
+  JitFunctionContext &operator=(JitFunctionContext &&) = default;
+  // Non copyable
+  JitFunctionContext(const JitFunctionContext &) = delete;
+  JitFunctionContext &operator=(const JitFunctionContext &) = delete;
+
+  const llvm::BitVector &getReservedRegs() const { return ReservedRegs; }
+
+private:
+  friend class JitFunction;
+
+  std::unique_ptr<llvm::LLVMContext> Context;
+  std::unique_ptr<llvm::LLVMTargetMachine> TM;
+  std::unique_ptr<llvm::MachineModuleInfo> MMI;
+  std::unique_ptr<llvm::Module> Module;
+  llvm::MachineFunction *MF = nullptr;
+  llvm::BitVector ReservedRegs;
+};
+
+// Creates a void() function from a sequence of llvm::MCInst.
+class JitFunction {
+public:
+  // Assembles Instructions into an executable function.
+  JitFunction(JitFunctionContext &&Context,
+              llvm::ArrayRef<llvm::MCInst> Instructions);
+
+  // Retrieves the function as an array of bytes.
+  llvm::StringRef getFunctionBytes() const { return FunctionBytes; }
+
+  // Retrieves the callable function.
+  void operator()() const {
+    char* const FnData = const_cast<char*>(FunctionBytes.data());
+    ((void (*)())(intptr_t)FnData)();
+  }
+
+private:
+  JitFunctionContext FunctionContext;
+  std::unique_ptr<llvm::ExecutionEngine> ExecEngine;
+  llvm::StringRef FunctionBytes;
+};
+
+} // namespace exegesis
+
+#endif // LLVM_TOOLS_LLVM_EXEGESIS_INMEMORYASSEMBLER_H