diff --git a/clang/lib/CodeGen/CGOpenMPRuntimeGPU.cpp b/clang/lib/CodeGen/CGOpenMPRuntimeGPU.cpp
--- a/clang/lib/CodeGen/CGOpenMPRuntimeGPU.cpp
+++ b/clang/lib/CodeGen/CGOpenMPRuntimeGPU.cpp
@@ -1128,7 +1128,7 @@
   const auto I = FunctionGlobalizedDecls.find(CGF.CurFn);
   if (I != FunctionGlobalizedDecls.end()) {
     // Deallocate the memory for each globalized VLA object
-    for (auto AddrSizePair :
+    for (const auto &AddrSizePair :
          llvm::reverse(I->getSecond().EscapedVariableLengthDeclsAddrs)) {
       CGF.EmitRuntimeCall(OMPBuilder.getOrCreateRuntimeFunction(
                               CGM.getModule(), OMPRTL___kmpc_free_shared),
diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -4425,7 +4425,7 @@
       Id->second->setOutOfDate(true);
   }
   // Mark selectors as out of date.
-  for (auto Sel : SelectorGeneration)
+  for (const auto &Sel : SelectorGeneration)
     SelectorOutOfDate[Sel.first] = true;
 
   // Resolve any unresolved module exports.
@@ -7693,7 +7693,7 @@
   };
 
   if (isa<TranslationUnitDecl>(DC)) {
-    for (auto Lexical : TULexicalDecls)
+    for (const auto &Lexical : TULexicalDecls)
       Visit(Lexical.first, Lexical.second);
   } else {
     auto I = LexicalDecls.find(DC);
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -1884,7 +1884,7 @@
 
       // If the file didn't exist, we can still create a module if we were given
       // enough information in the module map.
-      for (auto U : M->MissingHeaders) {
+      for (const auto &U : M->MissingHeaders) {
         // Check that we were given enough information to build a module
         // without this file existing on disk.
         if (!U.Size || (!U.ModTime && IncludeTimestamps)) {