diff --git a/clang/lib/CodeGen/BackendUtil.cpp b/clang/lib/CodeGen/BackendUtil.cpp
index 05b3ac4305ac..7ee8e1fc8a22 100644
--- a/clang/lib/CodeGen/BackendUtil.cpp
+++ b/clang/lib/CodeGen/BackendUtil.cpp
@@ -458,8 +458,8 @@ TargetMachine *EmitAssemblyHelper::CreateTargetMachine(bool MustCreateTM) {
     BackendArgs.push_back("-limit-float-precision");
     BackendArgs.push_back(CodeGenOpts.LimitFloatPrecision.c_str());
   }
-  for (unsigned i = 0, e = CodeGenOpts.BackendOptions.size(); i != e; ++i)
-    BackendArgs.push_back(CodeGenOpts.BackendOptions[i].c_str());
+  for (const std::string &BackendOption : CodeGenOpts.BackendOptions)
+    BackendArgs.push_back(BackendOption.c_str());
   BackendArgs.push_back(nullptr);
   llvm::cl::ParseCommandLineOptions(BackendArgs.size() - 1,
                                     BackendArgs.data());
diff --git a/clang/lib/CodeGen/CGVTables.cpp b/clang/lib/CodeGen/CGVTables.cpp
index 3f5c7a49c172..42cfd36e845e 100644
--- a/clang/lib/CodeGen/CGVTables.cpp
+++ b/clang/lib/CodeGen/CGVTables.cpp
@@ -502,8 +502,8 @@ void CodeGenVTables::EmitThunks(GlobalDecl GD)
   if (!ThunkInfoVector)
     return;
 
-  for (unsigned I = 0, E = ThunkInfoVector->size(); I != E; ++I)
-    emitThunk(GD, (*ThunkInfoVector)[I], /*ForVTable=*/false);
+  for (const ThunkInfo& Thunk : *ThunkInfoVector)
+    emitThunk(GD, Thunk, /*ForVTable=*/false);
 }
 
 llvm::Constant *CodeGenVTables::CreateVTableInitializer(
diff --git a/clang/lib/CodeGen/CodeGenAction.cpp b/clang/lib/CodeGen/CodeGenAction.cpp
index 0e7b6d8a71d4..8f5ee6fde0aa 100644
--- a/clang/lib/CodeGen/CodeGenAction.cpp
+++ b/clang/lib/CodeGen/CodeGenAction.cpp
@@ -333,8 +333,7 @@ void BackendConsumer::InlineAsmDiagHandler2(const llvm::SMDiagnostic &D,
       DiagnosticBuilder B = Diags.Report(Loc, diag::note_fe_inline_asm_here);
       // Convert the SMDiagnostic ranges into SourceRange and attach them
       // to the diagnostic.
-      for (unsigned i = 0, e = D.getRanges().size(); i != e; ++i) {
-        std::pair<unsigned, unsigned> Range = D.getRanges()[i];
+      for (const std::pair<unsigned, unsigned> &Range : D.getRanges()) {
         unsigned Column = D.getColumnNo();
         B << SourceRange(Loc.getLocWithOffset(Range.first - Column),
                          Loc.getLocWithOffset(Range.second - Column));
diff --git a/clang/lib/CodeGen/ItaniumCXXABI.cpp b/clang/lib/CodeGen/ItaniumCXXABI.cpp
index 0b65088e6196..cb506c32cbab 100644
--- a/clang/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/clang/lib/CodeGen/ItaniumCXXABI.cpp
@@ -2079,9 +2079,9 @@ void ItaniumCXXABI::EmitThreadLocalInitFuncs(
     CodeGenFunction(CGM)
         .GenerateCXXGlobalInitFunc(InitFunc, CXXThreadLocalInits, Guard);
   }
-  for (unsigned I = 0, N = CXXThreadLocals.size(); I != N; ++I) {
-    const VarDecl *VD = CXXThreadLocals[I].first;
-    llvm::GlobalVariable *Var = CXXThreadLocals[I].second;
+  for (auto &I : CXXThreadLocals) {
+    const VarDecl *VD = I.first;
+    llvm::GlobalVariable *Var = I.second;
 
     // Some targets require that all access to thread local variables go through
     // the thread wrapper.  This means that we cannot attempt to create a thread