diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -8203,7 +8203,7 @@
   if (!CXXRD->hasDefinition() || !VisitBasesAndFields)
     return false;
 
-  for (auto B : CXXRD->bases())
+  for (const auto &B : CXXRD->bases())
     if (hasTemplateSpecializationInEncodedString(B.getType().getTypePtr(),
                                                  true))
       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
@@ -760,7 +760,7 @@
   D |= getDependenceInExpr(E->getNameInfo());
   if (auto *Q = E->getQualifier())
     D |= toExprDependence(Q->getDependence());
-  for (auto A : E->template_arguments())
+  for (const auto &A : E->template_arguments())
     D |= toExprDependence(A.getArgument().getDependence());
   return D;
 }
@@ -813,7 +813,7 @@
   if (auto *Q = E->getQualifier())
     D |= toExprDependence(Q->getDependence());
   D |= getDependenceInExpr(E->getMemberNameInfo());
-  for (auto A : E->template_arguments())
+  for (const auto &A : E->template_arguments())
     D |= toExprDependence(A.getArgument().getDependence());
   return D;
 }
diff --git a/clang/lib/ASTMatchers/Dynamic/Marshallers.h b/clang/lib/ASTMatchers/Dynamic/Marshallers.h
--- a/clang/lib/ASTMatchers/Dynamic/Marshallers.h
+++ b/clang/lib/ASTMatchers/Dynamic/Marshallers.h
@@ -1008,7 +1008,7 @@
                    Diagnostics *) const override {
 
     std::vector<ASTNodeKind> NodeKinds;
-    for (auto Arg : Args) {
+    for (const auto &Arg : Args) {
       if (!Arg.Value.isNodeKind())
         return {};
       NodeKinds.push_back(Arg.Value.getNodeKind());
diff --git a/clang/lib/CodeGen/CGVTables.cpp b/clang/lib/CodeGen/CGVTables.cpp
--- a/clang/lib/CodeGen/CGVTables.cpp
+++ b/clang/lib/CodeGen/CGVTables.cpp
@@ -1269,13 +1269,13 @@
   else
     TypeVis = llvm::GlobalObject::VCallVisibilityPublic;
 
-  for (auto B : RD->bases())
+  for (const auto &B : RD->bases())
     if (B.getType()->getAsCXXRecordDecl()->isDynamicClass())
       TypeVis = std::min(
           TypeVis,
           GetVCallVisibilityLevel(B.getType()->getAsCXXRecordDecl(), Visited));
 
-  for (auto B : RD->vbases())
+  for (const auto &B : RD->vbases())
     if (B.getType()->getAsCXXRecordDecl()->isDynamicClass())
       TypeVis = std::min(
           TypeVis,
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -3971,7 +3971,7 @@
     }
 
     llvm::SmallPtrSet<QualType, 4> UninitializedBaseClasses;
-    for (auto I : RD->bases())
+    for (const auto &I : RD->bases())
       UninitializedBaseClasses.insert(I.getType().getCanonicalType());
 
     if (UninitializedFields.empty() && UninitializedBaseClasses.empty())
diff --git a/clang/utils/TableGen/ClangAttrEmitter.cpp b/clang/utils/TableGen/ClangAttrEmitter.cpp
--- a/clang/utils/TableGen/ClangAttrEmitter.cpp
+++ b/clang/utils/TableGen/ClangAttrEmitter.cpp
@@ -4259,7 +4259,7 @@
 
   // Generate all of the custom appertainsTo functions that the attributes
   // will be using.
-  for (auto I : Attrs) {
+  for (const auto &I : Attrs) {
     const Record &Attr = *I.second;
     if (Attr.isValueUnset("Subjects"))
       continue;