diff --git a/llvm/include/llvm/CodeGen/ReachingDefAnalysis.h b/llvm/include/llvm/CodeGen/ReachingDefAnalysis.h
index c889f3c6d4ae..0b4b0007e946 100644
--- a/llvm/include/llvm/CodeGen/ReachingDefAnalysis.h
+++ b/llvm/include/llvm/CodeGen/ReachingDefAnalysis.h
@@ -37,6 +37,7 @@ class ReachingDefAnalysis : public MachineFunctionPass {
 private:
   MachineFunction *MF;
   const TargetRegisterInfo *TRI;
+  LoopTraversal::TraversalOrder TraversedMBBOrder;
   unsigned NumRegUnits;
   /// Instruction that defined each register, relative to the beginning of the
   /// current basic block.  When a LiveRegsDefInfo is used to represent a
@@ -93,6 +94,15 @@ public:
           MachineFunctionProperties::Property::TracksLiveness);
   }
 
+  /// Re-run the analysis.
+  void reset();
+
+  /// Initialize data structures.
+  void init();
+
+  /// Traverse the machine function, mapping definitions.
+  void traverse();
+
   /// Provides the instruction id of the closest reaching def instruction of
   /// PhysReg that reaches MI, relative to the begining of MI's basic block.
   int getReachingDef(MachineInstr *MI, int PhysReg) const;
diff --git a/llvm/lib/CodeGen/ReachingDefAnalysis.cpp b/llvm/lib/CodeGen/ReachingDefAnalysis.cpp
index 03122ae75670..c14fa8c43b38 100644
--- a/llvm/lib/CodeGen/ReachingDefAnalysis.cpp
+++ b/llvm/lib/CodeGen/ReachingDefAnalysis.cpp
@@ -136,30 +136,9 @@ void ReachingDefAnalysis::processBasicBlock(
 bool ReachingDefAnalysis::runOnMachineFunction(MachineFunction &mf) {
   MF = &mf;
   TRI = MF->getSubtarget().getRegisterInfo();
-
-  LiveRegs.clear();
-  NumRegUnits = TRI->getNumRegUnits();
-
-  MBBReachingDefs.resize(mf.getNumBlockIDs());
-
   LLVM_DEBUG(dbgs() << "********** REACHING DEFINITION ANALYSIS **********\n");
-
-  // Initialize the MBBOutRegsInfos
-  MBBOutRegsInfos.resize(mf.getNumBlockIDs());
-
-  // Traverse the basic blocks.
-  LoopTraversal Traversal;
-  LoopTraversal::TraversalOrder TraversedMBBOrder = Traversal.traverse(mf);
-  for (LoopTraversal::TraversedMBBInfo TraversedMBB : TraversedMBBOrder) {
-    processBasicBlock(TraversedMBB);
-  }
-
-  // Sorting all reaching defs found for a ceartin reg unit in a given BB.
-  for (MBBDefsInfo &MBBDefs : MBBReachingDefs) {
-    for (MBBRegUnitDefs &RegUnitDefs : MBBDefs)
-      llvm::sort(RegUnitDefs);
-  }
-
+  init();
+  traverse();
   return false;
 }
 
@@ -168,6 +147,33 @@ void ReachingDefAnalysis::releaseMemory() {
   MBBOutRegsInfos.clear();
   MBBReachingDefs.clear();
   InstIds.clear();
+  LiveRegs.clear();
+}
+
+void ReachingDefAnalysis::reset() {
+  releaseMemory();
+  init();
+  traverse();
+}
+
+void ReachingDefAnalysis::init() {
+  NumRegUnits = TRI->getNumRegUnits();
+  MBBReachingDefs.resize(MF->getNumBlockIDs());
+  // Initialize the MBBOutRegsInfos
+  MBBOutRegsInfos.resize(MF->getNumBlockIDs());
+  LoopTraversal Traversal;
+  TraversedMBBOrder = Traversal.traverse(*MF);
+}
+
+void ReachingDefAnalysis::traverse() {
+  // Traverse the basic blocks.
+  for (LoopTraversal::TraversedMBBInfo TraversedMBB : TraversedMBBOrder)
+    processBasicBlock(TraversedMBB);
+  // Sorting all reaching defs found for a ceartin reg unit in a given BB.
+  for (MBBDefsInfo &MBBDefs : MBBReachingDefs) {
+    for (MBBRegUnitDefs &RegUnitDefs : MBBDefs)
+      llvm::sort(RegUnitDefs);
+  }
 }
 
 int ReachingDefAnalysis::getReachingDef(MachineInstr *MI, int PhysReg) const {