Index: lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
===================================================================
--- lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
+++ lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
@@ -732,7 +732,7 @@
 
 #ifndef NDEBUG
   DEBUG(dbgs() << "States after initialization:\n");
-  for (auto Pair : States) {
+  for (const auto &Pair : States) {
     DEBUG(dbgs() << " " << Pair.second << " for " << *Pair.first << "\n");
   }
 #endif
@@ -757,8 +757,9 @@
     // Since this is computing a fixed point, the order of visit does not
     // effect the result.  TODO: We could use a worklist here and make this run
     // much faster.
-    for (auto Pair : States) {
+    for (auto &Pair : States) {
       Value *BDV = Pair.first;
+      BDVState &State = Pair.second;
       assert(!isKnownBaseResult(BDV) && "why did it get added?");
 
       // Given an input value for the current instruction, return a BDVState
@@ -794,10 +795,9 @@
         NewState = meetBDVState(NewState, getStateForInput(SV->getOperand(1)));
       }
 
-      BDVState OldState = States[BDV];
-      if (OldState != NewState) {
+      if (State != NewState) {
         Progress = true;
-        States[BDV] = NewState;
+        State = NewState;
       }
     }
 
@@ -807,16 +807,16 @@
 
 #ifndef NDEBUG
   DEBUG(dbgs() << "States after meet iteration:\n");
-  for (auto Pair : States) {
+  for (const auto &Pair : States) {
     DEBUG(dbgs() << " " << Pair.second << " for " << *Pair.first << "\n");
   }
 #endif
 
   // Insert Phis for all conflicts
   // TODO: adjust naming patterns to avoid this order of iteration dependency
-  for (auto Pair : States) {
+  for (auto &Pair : States) {
     Instruction *I = cast<Instruction>(Pair.first);
-    BDVState State = Pair.second;
+    BDVState &State = Pair.second;
     assert(!isKnownBaseResult(I) && "why did it get added?");
     assert(!State.isUnknown() && "Optimistic algorithm didn't complete!");
 
@@ -833,7 +833,7 @@
       auto *BaseInst = ExtractElementInst::Create(
           State.getBaseValue(), EE->getIndexOperand(), "base_ee", EE);
       BaseInst->setMetadata("is_base_value", MDNode::get(I->getContext(), {}));
-      States[I] = BDVState(BDVState::Base, BaseInst);
+      State = BDVState(BDVState::Base, BaseInst);
     }
 
     // Since we're joining a vector and scalar base, they can never be the
@@ -880,7 +880,7 @@
     Instruction *BaseInst = MakeBaseInstPlaceholder(I);
     // Add metadata marking this as a base value
     BaseInst->setMetadata("is_base_value", MDNode::get(I->getContext(), {}));
-    States[I] = BDVState(BDVState::Conflict, BaseInst);
+    State = BDVState(BDVState::Conflict, BaseInst);
   }
 
   // Returns a instruction which produces the base pointer for a given
@@ -911,7 +911,7 @@
   // Fixup all the inputs of the new PHIs.  Visit order needs to be
   // deterministic and predictable because we're naming newly created
   // instructions.
-  for (auto Pair : States) {
+  for (const auto &Pair : States) {
     Instruction *BDV = cast<Instruction>(Pair.first);
     BDVState State = Pair.second;
 
@@ -1001,7 +1001,7 @@
   // Cache all of our results so we can cheaply reuse them
   // NOTE: This is actually two caches: one of the base defining value
   // relation and one of the base pointer relation!  FIXME
-  for (auto Pair : States) {
+  for (const auto &Pair : States) {
     auto *BDV = Pair.first;
     Value *Base = Pair.second.getBaseValue();
     assert(BDV && Base);