diff --git a/clang/include/clang/ExtractAPI/ExtractAPIVisitor.h b/clang/include/clang/ExtractAPI/ExtractAPIVisitor.h
--- a/clang/include/clang/ExtractAPI/ExtractAPIVisitor.h
+++ b/clang/include/clang/ExtractAPI/ExtractAPIVisitor.h
@@ -179,7 +179,7 @@
       return true;
 
     // Skip methods in records.
-    for (auto P : Context.getParents(*Method)) {
+    for (const auto &P : Context.getParents(*Method)) {
       if (P.template get<CXXRecordDecl>())
         return true;
     }
diff --git a/clang/lib/AST/ComputeDependence.cpp b/clang/lib/AST/ComputeDependence.cpp
--- a/clang/lib/AST/ComputeDependence.cpp
+++ b/clang/lib/AST/ComputeDependence.cpp
@@ -663,7 +663,7 @@
 
 ExprDependence clang::computeDependence(DesignatedInitExpr *E) {
   auto Deps = E->getInit()->getDependence();
-  for (auto D : E->designators()) {
+  for (const auto &D : E->designators()) {
     auto DesignatorDeps = ExprDependence::None;
     if (D.isArrayDesignator())
       DesignatorDeps |= E->getArrayIndex(D)->getDependence();
diff --git a/clang/lib/CodeGen/CGGPUBuiltin.cpp b/clang/lib/CodeGen/CGGPUBuiltin.cpp
--- a/clang/lib/CodeGen/CGGPUBuiltin.cpp
+++ b/clang/lib/CodeGen/CGGPUBuiltin.cpp
@@ -189,7 +189,7 @@
                /* ParamsToSkip = */ 0);
 
   SmallVector<llvm::Value *, 8> Args;
-  for (auto A : CallArgs) {
+  for (const auto &A : CallArgs) {
     // We don't know how to emit non-scalar varargs.
     if (!A.getRValue(*this).isScalar()) {
       CGM.ErrorUnsupported(E, "non-scalar arg to printf");
diff --git a/clang/lib/CodeGen/MicrosoftCXXABI.cpp b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
--- a/clang/lib/CodeGen/MicrosoftCXXABI.cpp
+++ b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
@@ -3757,7 +3757,7 @@
   Classes.front().initialize(/*Parent=*/nullptr, /*Specifier=*/nullptr);
   detectAmbiguousBases(Classes);
   int Flags = 0;
-  for (auto Class : Classes) {
+  for (const MSRTTIClass &Class : Classes) {
     if (Class.RD->getNumBases() > 1)
       Flags |= HasBranchingHierarchy;
     // Note: cl.exe does not calculate "HasAmbiguousBases" correctly.  We
diff --git a/clang/lib/Format/Format.cpp b/clang/lib/Format/Format.cpp
--- a/clang/lib/Format/Format.cpp
+++ b/clang/lib/Format/Format.cpp
@@ -2806,7 +2806,7 @@
 // Determines whether 'Ranges' intersects with ('Start', 'End').
 static bool affectsRange(ArrayRef<tooling::Range> Ranges, unsigned Start,
                          unsigned End) {
-  for (auto Range : Ranges) {
+  for (const auto &Range : Ranges) {
     if (Range.getOffset() < End &&
         Range.getOffset() + Range.getLength() > Start) {
       return true;
diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -447,7 +447,7 @@
   if (!CXXRecord)
     return false;
 
-  for (auto BaseSpecifier : CXXRecord->bases()) {
+  for (const auto &BaseSpecifier : CXXRecord->bases()) {
     if (!foundStarOperator)
       foundStarOperator = IsOverloadedOperatorPresent(
           BaseSpecifier.getType()->getAsRecordDecl(), OO_Star);
diff --git a/clang/utils/TableGen/NeonEmitter.cpp b/clang/utils/TableGen/NeonEmitter.cpp
--- a/clang/utils/TableGen/NeonEmitter.cpp
+++ b/clang/utils/TableGen/NeonEmitter.cpp
@@ -389,7 +389,7 @@
       Mods = getNextModifiers(Proto, Pos);
     }
 
-    for (auto Type : Types) {
+    for (const auto &Type : Types) {
       // If this builtin takes an immediate argument, we need to #define it rather
       // than use a standard declaration, so that SemaChecking can range check
       // the immediate passed by the user.