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diff --git a/gnu/llvm/lib/CodeGen/AsmPrinter/DbgValueHistoryCalculator.cpp b/gnu/llvm/lib/CodeGen/AsmPrinter/DbgValueHistoryCalculator.cpp
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index 00000000000..3c46a99d084
--- /dev/null
+++ b/gnu/llvm/lib/CodeGen/AsmPrinter/DbgValueHistoryCalculator.cpp
@@ -0,0 +1,232 @@
+//===-- llvm/CodeGen/AsmPrinter/DbgValueHistoryCalculator.cpp -------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "DbgValueHistoryCalculator.h"
+#include "llvm/ADT/BitVector.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/MachineBasicBlock.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/IR/DebugInfo.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Target/TargetRegisterInfo.h"
+#include <algorithm>
+#include <map>
+using namespace llvm;
+
+#define DEBUG_TYPE "dwarfdebug"
+
+// \brief If @MI is a DBG_VALUE with debug value described by a
+// defined register, returns the number of this register.
+// In the other case, returns 0.
+static unsigned isDescribedByReg(const MachineInstr &MI) {
+  assert(MI.isDebugValue());
+  assert(MI.getNumOperands() == 4);
+  // If location of variable is described using a register (directly or
+  // indirecltly), this register is always a first operand.
+  return MI.getOperand(0).isReg() ? MI.getOperand(0).getReg() : 0;
+}
+
+void DbgValueHistoryMap::startInstrRange(InlinedVariable Var,
+                                         const MachineInstr &MI) {
+  // Instruction range should start with a DBG_VALUE instruction for the
+  // variable.
+  assert(MI.isDebugValue() && "not a DBG_VALUE");
+  auto &Ranges = VarInstrRanges[Var];
+  if (!Ranges.empty() && Ranges.back().second == nullptr &&
+      Ranges.back().first->isIdenticalTo(&MI)) {
+    DEBUG(dbgs() << "Coalescing identical DBG_VALUE entries:\n"
+                 << "\t" << Ranges.back().first << "\t" << MI << "\n");
+    return;
+  }
+  Ranges.push_back(std::make_pair(&MI, nullptr));
+}
+
+void DbgValueHistoryMap::endInstrRange(InlinedVariable Var,
+                                       const MachineInstr &MI) {
+  auto &Ranges = VarInstrRanges[Var];
+  // Verify that the current instruction range is not yet closed.
+  assert(!Ranges.empty() && Ranges.back().second == nullptr);
+  // For now, instruction ranges are not allowed to cross basic block
+  // boundaries.
+  assert(Ranges.back().first->getParent() == MI.getParent());
+  Ranges.back().second = &MI;
+}
+
+unsigned DbgValueHistoryMap::getRegisterForVar(InlinedVariable Var) const {
+  const auto &I = VarInstrRanges.find(Var);
+  if (I == VarInstrRanges.end())
+    return 0;
+  const auto &Ranges = I->second;
+  if (Ranges.empty() || Ranges.back().second != nullptr)
+    return 0;
+  return isDescribedByReg(*Ranges.back().first);
+}
+
+namespace {
+// Maps physreg numbers to the variables they describe.
+typedef DbgValueHistoryMap::InlinedVariable InlinedVariable;
+typedef std::map<unsigned, SmallVector<InlinedVariable, 1>> RegDescribedVarsMap;
+}
+
+// \brief Claim that @Var is not described by @RegNo anymore.
+static void dropRegDescribedVar(RegDescribedVarsMap &RegVars, unsigned RegNo,
+                                InlinedVariable Var) {
+  const auto &I = RegVars.find(RegNo);
+  assert(RegNo != 0U && I != RegVars.end());
+  auto &VarSet = I->second;
+  const auto &VarPos = std::find(VarSet.begin(), VarSet.end(), Var);
+  assert(VarPos != VarSet.end());
+  VarSet.erase(VarPos);
+  // Don't keep empty sets in a map to keep it as small as possible.
+  if (VarSet.empty())
+    RegVars.erase(I);
+}
+
+// \brief Claim that @Var is now described by @RegNo.
+static void addRegDescribedVar(RegDescribedVarsMap &RegVars, unsigned RegNo,
+                               InlinedVariable Var) {
+  assert(RegNo != 0U);
+  auto &VarSet = RegVars[RegNo];
+  assert(std::find(VarSet.begin(), VarSet.end(), Var) == VarSet.end());
+  VarSet.push_back(Var);
+}
+
+// \brief Terminate the location range for variables described by register at
+// @I by inserting @ClobberingInstr to their history.
+static void clobberRegisterUses(RegDescribedVarsMap &RegVars,
+                                RegDescribedVarsMap::iterator I,
+                                DbgValueHistoryMap &HistMap,
+                                const MachineInstr &ClobberingInstr) {
+  // Iterate over all variables described by this register and add this
+  // instruction to their history, clobbering it.
+  for (const auto &Var : I->second)
+    HistMap.endInstrRange(Var, ClobberingInstr);
+  RegVars.erase(I);
+}
+
+// \brief Terminate the location range for variables described by register
+// @RegNo by inserting @ClobberingInstr to their history.
+static void clobberRegisterUses(RegDescribedVarsMap &RegVars, unsigned RegNo,
+                                DbgValueHistoryMap &HistMap,
+                                const MachineInstr &ClobberingInstr) {
+  const auto &I = RegVars.find(RegNo);
+  if (I == RegVars.end())
+    return;
+  clobberRegisterUses(RegVars, I, HistMap, ClobberingInstr);
+}
+
+// \brief Collect all registers clobbered by @MI and apply the functor
+// @Func to their RegNo.
+// @Func should be a functor with a void(unsigned) signature. We're
+// not using std::function here for performance reasons. It has a
+// small but measurable impact. By using a functor instead of a
+// std::set& here, we can avoid the overhead of constructing
+// temporaries in calculateDbgValueHistory, which has a significant
+// performance impact.
+template<typename Callable>
+static void applyToClobberedRegisters(const MachineInstr &MI,
+                                      const TargetRegisterInfo *TRI,
+                                      Callable Func) {
+  for (const MachineOperand &MO : MI.operands()) {
+    if (!MO.isReg() || !MO.isDef() || !MO.getReg())
+      continue;
+    for (MCRegAliasIterator AI(MO.getReg(), TRI, true); AI.isValid(); ++AI)
+      Func(*AI);
+  }
+}
+
+// \brief Returns the first instruction in @MBB which corresponds to
+// the function epilogue, or nullptr if @MBB doesn't contain an epilogue.
+static const MachineInstr *getFirstEpilogueInst(const MachineBasicBlock &MBB) {
+  auto LastMI = MBB.getLastNonDebugInstr();
+  if (LastMI == MBB.end() || !LastMI->isReturn())
+    return nullptr;
+  // Assume that epilogue starts with instruction having the same debug location
+  // as the return instruction.
+  DebugLoc LastLoc = LastMI->getDebugLoc();
+  auto Res = LastMI;
+  for (MachineBasicBlock::const_reverse_iterator I(std::next(LastMI)),
+       E = MBB.rend();
+       I != E; ++I) {
+    if (I->getDebugLoc() != LastLoc)
+      return Res;
+    Res = &*I;
+  }
+  // If all instructions have the same debug location, assume whole MBB is
+  // an epilogue.
+  return MBB.begin();
+}
+
+// \brief Collect registers that are modified in the function body (their
+// contents is changed outside of the prologue and epilogue).
+static void collectChangingRegs(const MachineFunction *MF,
+                                const TargetRegisterInfo *TRI,
+                                BitVector &Regs) {
+  for (const auto &MBB : *MF) {
+    auto FirstEpilogueInst = getFirstEpilogueInst(MBB);
+
+    for (const auto &MI : MBB) {
+      if (&MI == FirstEpilogueInst)
+        break;
+      if (!MI.getFlag(MachineInstr::FrameSetup))
+        applyToClobberedRegisters(MI, TRI, [&](unsigned r) { Regs.set(r); });
+    }
+  }
+}
+
+void llvm::calculateDbgValueHistory(const MachineFunction *MF,
+                                    const TargetRegisterInfo *TRI,
+                                    DbgValueHistoryMap &Result) {
+  BitVector ChangingRegs(TRI->getNumRegs());
+  collectChangingRegs(MF, TRI, ChangingRegs);
+
+  RegDescribedVarsMap RegVars;
+  for (const auto &MBB : *MF) {
+    for (const auto &MI : MBB) {
+      if (!MI.isDebugValue()) {
+        // Not a DBG_VALUE instruction. It may clobber registers which describe
+        // some variables.
+        applyToClobberedRegisters(MI, TRI, [&](unsigned RegNo) {
+          if (ChangingRegs.test(RegNo))
+            clobberRegisterUses(RegVars, RegNo, Result, MI);
+        });
+        continue;
+      }
+
+      assert(MI.getNumOperands() > 1 && "Invalid DBG_VALUE instruction!");
+      // Use the base variable (without any DW_OP_piece expressions)
+      // as index into History. The full variables including the
+      // piece expressions are attached to the MI.
+      const DILocalVariable *RawVar = MI.getDebugVariable();
+      assert(RawVar->isValidLocationForIntrinsic(MI.getDebugLoc()) &&
+             "Expected inlined-at fields to agree");
+      InlinedVariable Var(RawVar, MI.getDebugLoc()->getInlinedAt());
+
+      if (unsigned PrevReg = Result.getRegisterForVar(Var))
+        dropRegDescribedVar(RegVars, PrevReg, Var);
+
+      Result.startInstrRange(Var, MI);
+
+      if (unsigned NewReg = isDescribedByReg(MI))
+        addRegDescribedVar(RegVars, NewReg, Var);
+    }
+
+    // Make sure locations for register-described variables are valid only
+    // until the end of the basic block (unless it's the last basic block, in
+    // which case let their liveness run off to the end of the function).
+    if (!MBB.empty() && &MBB != &MF->back()) {
+      for (auto I = RegVars.begin(), E = RegVars.end(); I != E;) {
+        auto CurElem = I++; // CurElem can be erased below.
+        if (ChangingRegs.test(CurElem->first))
+          clobberRegisterUses(RegVars, CurElem, Result, MBB.back());
+      }
+    }
+  }
+}