diff --git a/llvm/lib/CodeGen/AsmPrinter/DbgValueHistoryCalculator.cpp b/llvm/lib/CodeGen/AsmPrinter/DbgValueHistoryCalculator.cpp
index 143b0135c8c8..998c396924bc 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DbgValueHistoryCalculator.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DbgValueHistoryCalculator.cpp
@@ -112,15 +112,23 @@ static void clobberRegisterUses(RegDescribedVarsMap &RegVars, unsigned RegNo,
   RegVars.erase(I);
 }
 
-// \brief Collect all registers clobbered by @MI and insert them to @Regs.
-static void collectClobberedRegisters(const MachineInstr &MI,
+// \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,
-                                      std::set<unsigned> &Regs) {
+                                      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)
-      Regs.insert(*AI);
+      Func(*AI);
   }
 }
 
@@ -146,7 +154,7 @@ static const MachineInstr *getFirstEpilogueInst(const MachineBasicBlock &MBB) {
 }
 
 // \brief Collect registers that are modified in the function body (their
-// contents is changed only in the prologue and epilogue).
+// contents is changed outside of the prologue and epilogue).
 static void collectChangingRegs(const MachineFunction *MF,
                                 const TargetRegisterInfo *TRI,
                                 std::set<unsigned> &Regs) {
@@ -157,7 +165,7 @@ static void collectChangingRegs(const MachineFunction *MF,
       if (&MI == FirstEpilogueInst)
         break;
       if (!MI.getFlag(MachineInstr::FrameSetup))
-        collectClobberedRegisters(MI, TRI, Regs);
+        applyToClobberedRegisters(MI, TRI, [&](unsigned r) { Regs.insert(r); });
     }
   }
 }
@@ -174,12 +182,10 @@ void calculateDbgValueHistory(const MachineFunction *MF,
       if (!MI.isDebugValue()) {
         // Not a DBG_VALUE instruction. It may clobber registers which describe
         // some variables.
-        std::set<unsigned> MIClobberedRegs;
-        collectClobberedRegisters(MI, TRI, MIClobberedRegs);
-        for (unsigned RegNo : MIClobberedRegs) {
+        applyToClobberedRegisters(MI, TRI, [&](unsigned RegNo) {
           if (ChangingRegs.count(RegNo))
             clobberRegisterUses(RegVars, RegNo, Result, MI);
-        }
+        });
         continue;
       }