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diff --git a/llvm/lib/CodeGen/RegAllocScore.h b/llvm/lib/CodeGen/RegAllocScore.h
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+//==- RegAllocScore.h - evaluate regalloc policy quality  ----------*-C++-*-==//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+/// Calculate a measure of the register allocation policy quality. This is used
+/// to construct a reward for the training of the ML-driven allocation policy.
+/// Currently, the score is the sum of the machine basic block frequency-weighed
+/// number of loads, stores, copies, and remat instructions, each factored with
+/// a relative weight.
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_REGALLOCSCORE_H_
+#define LLVM_CODEGEN_REGALLOCSCORE_H_
+
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/SetVector.h"
+#include "llvm/ADT/StringMap.h"
+#include "llvm/Analysis/ProfileSummaryInfo.h"
+#include "llvm/Analysis/Utils/TFUtils.h"
+#include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/SelectionDAGNodes.h"
+#include "llvm/IR/Module.h"
+#include <cassert>
+#include <cstdint>
+#include <limits>
+
+namespace llvm {
+
+/// Regalloc score.
+class RegAllocScore final {
+  double CopyCounts = 0.0;
+  double LoadCounts = 0.0;
+  double StoreCounts = 0.0;
+  double CheapRematCounts = 0.0;
+  double LoadStoreCounts = 0.0;
+  double ExpensiveRematCounts = 0.0;
+
+public:
+  RegAllocScore() = default;
+  RegAllocScore(const RegAllocScore &) = default;
+
+  double copyCounts() const { return CopyCounts; }
+  double loadCounts() const { return LoadCounts; }
+  double storeCounts() const { return StoreCounts; }
+  double loadStoreCounts() const { return LoadStoreCounts; }
+  double expensiveRematCounts() const { return ExpensiveRematCounts; }
+  double cheapRematCounts() const { return CheapRematCounts; }
+
+  void onCopy(double Freq) { CopyCounts += Freq; }
+  void onLoad(double Freq) { LoadCounts += Freq; }
+  void onStore(double Freq) { StoreCounts += Freq; }
+  void onLoadStore(double Freq) { LoadStoreCounts += Freq; }
+  void onExpensiveRemat(double Freq) { ExpensiveRematCounts += Freq; }
+  void onCheapRemat(double Freq) { CheapRematCounts += Freq; }
+
+  RegAllocScore &operator+=(const RegAllocScore &Other);
+  bool operator==(const RegAllocScore &Other) const;
+  bool operator!=(const RegAllocScore &Other) const;
+  double getScore() const;
+};
+
+/// Calculate a score. When comparing 2 scores for the same function but
+/// different policies, the better policy would have a smaller score.
+/// The implementation is the overload below (which is also easily unittestable)
+RegAllocScore calculateRegAllocScore(const MachineFunction &MF,
+                                     const MachineBlockFrequencyInfo &MBFI,
+                                     AAResults &AAResults);
+
+/// Implementation of the above, which is also more easily unittestable.
+RegAllocScore calculateRegAllocScore(
+    const MachineFunction &MF,
+    llvm::function_ref<double(const MachineBasicBlock &)> GetBBFreq,
+    llvm::function_ref<bool(const MachineInstr &)> IsTriviallyRematerializable);
+} // end namespace llvm
+
+#endif // LLVM_CODEGEN_REGALLOCSCORE_H_