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diff --git a/llvm/lib/CodeGen/RemoveRedundantDebugValues.cpp b/llvm/lib/CodeGen/RemoveRedundantDebugValues.cpp
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+++ b/llvm/lib/CodeGen/RemoveRedundantDebugValues.cpp
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+//===- RemoveRedundantDebugValues.cpp - Remove Redundant Debug Value MIs --===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/DenseSet.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/CodeGen/MachineBasicBlock.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/DebugInfoMetadata.h"
+#include "llvm/IR/Function.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+
+/// \file RemoveRedundantDebugValues.cpp
+///
+/// The RemoveRedundantDebugValues pass removes redundant DBG_VALUEs that
+/// appear in MIR after the register allocator.
+
+#define DEBUG_TYPE "removeredundantdebugvalues"
+
+using namespace llvm;
+
+STATISTIC(NumRemovedBackward, "Number of DBG_VALUEs removed (backward scan)");
+
+namespace {
+
+class RemoveRedundantDebugValues : public MachineFunctionPass {
+public:
+  static char ID;
+
+  RemoveRedundantDebugValues();
+
+  bool reduceDbgValues(MachineFunction &MF);
+
+  /// Remove redundant debug value MIs for the given machine function.
+  bool runOnMachineFunction(MachineFunction &MF) override;
+
+  void getAnalysisUsage(AnalysisUsage &AU) const override {
+    AU.setPreservesCFG();
+    MachineFunctionPass::getAnalysisUsage(AU);
+  }
+};
+
+} // namespace
+
+//===----------------------------------------------------------------------===//
+//            Implementation
+//===----------------------------------------------------------------------===//
+
+char RemoveRedundantDebugValues::ID = 0;
+
+char &llvm::RemoveRedundantDebugValuesID = RemoveRedundantDebugValues::ID;
+
+INITIALIZE_PASS(RemoveRedundantDebugValues, DEBUG_TYPE,
+                "Remove Redundant DEBUG_VALUE analysis", false, false)
+
+/// Default construct and initialize the pass.
+RemoveRedundantDebugValues::RemoveRedundantDebugValues()
+    : MachineFunctionPass(ID) {
+  initializeRemoveRedundantDebugValuesPass(*PassRegistry::getPassRegistry());
+}
+
+// This analysis aims to remove redundant DBG_VALUEs by going backward
+// in the basic block and removing all but the last DBG_VALUE for any
+// given variable in a set of consecutive DBG_VALUE instructions.
+// For example:
+//   (1) DBG_VALUE $edi, !"var1", ...
+//   (2) DBG_VALUE $esi, !"var2", ...
+//   (3) DBG_VALUE $edi, !"var1", ...
+//   ...
+// in this case, we can remove (1).
+static bool reduceDbgValsBackwardScan(MachineBasicBlock &MBB) {
+  LLVM_DEBUG(dbgs() << "\n == Backward Scan == \n");
+  SmallVector<MachineInstr *, 8> DbgValsToBeRemoved;
+  SmallDenseSet<DebugVariable> VariableSet;
+
+  for (MachineBasicBlock::reverse_iterator I = MBB.rbegin(), E = MBB.rend();
+       I != E; ++I) {
+    MachineInstr *MI = &*I;
+
+    if (MI->isDebugValue()) {
+      DebugVariable Var(MI->getDebugVariable(), MI->getDebugExpression(),
+                        MI->getDebugLoc()->getInlinedAt());
+      auto R = VariableSet.insert(Var);
+      // If it is a DBG_VALUE describing a constant as:
+      //   DBG_VALUE 0, ...
+      // we just don't consider such instructions as candidates
+      // for redundant removal.
+      if (MI->isNonListDebugValue()) {
+        MachineOperand &Loc = MI->getDebugOperand(0);
+        if (!Loc.isReg()) {
+          // If we have already encountered this variable, just stop
+          // tracking it.
+          if (!R.second)
+            VariableSet.erase(Var);
+          continue;
+        }
+      }
+
+      // We have already encountered the value for this variable,
+      // so this one can be deleted.
+      if (!R.second)
+        DbgValsToBeRemoved.push_back(MI);
+      continue;
+    }
+
+    // If we encountered a non-DBG_VALUE, try to find the next
+    // sequence with consecutive DBG_VALUE instructions.
+    VariableSet.clear();
+  }
+
+  for (auto &Instr : DbgValsToBeRemoved) {
+    LLVM_DEBUG(dbgs() << "removing "; Instr->dump());
+    Instr->eraseFromParent();
+    ++NumRemovedBackward;
+  }
+
+  return !DbgValsToBeRemoved.empty();
+}
+
+bool RemoveRedundantDebugValues::reduceDbgValues(MachineFunction &MF) {
+  LLVM_DEBUG(dbgs() << "\nDebug Value Reduction\n");
+
+  bool Changed = false;
+
+  for (auto &MBB : MF)
+    Changed |= reduceDbgValsBackwardScan(MBB);
+
+  return Changed;
+}
+
+bool RemoveRedundantDebugValues::runOnMachineFunction(MachineFunction &MF) {
+  // Skip functions without debugging information.
+  if (!MF.getFunction().getSubprogram())
+    return false;
+
+  // Skip functions from NoDebug compilation units.
+  if (MF.getFunction().getSubprogram()->getUnit()->getEmissionKind() ==
+      DICompileUnit::NoDebug)
+    return false;
+
+  bool Changed = reduceDbgValues(MF);
+  return Changed;
+}