diff --git a/llvm/lib/Support/SpecialCaseList.cpp b/llvm/lib/Support/SpecialCaseList.cpp
index ea417c41c0a7..0ffe4444a179 100644
--- a/llvm/lib/Support/SpecialCaseList.cpp
+++ b/llvm/lib/Support/SpecialCaseList.cpp
@@ -50,7 +50,7 @@ std::unique_ptr<SpecialCaseList>
 SpecialCaseList::create(const std::vector<std::string> &Paths,
                         std::string &Error) {
   std::unique_ptr<SpecialCaseList> SCL(new SpecialCaseList());
-  for (auto Path : Paths) {
+  for (const auto &Path : Paths) {
     ErrorOr<std::unique_ptr<MemoryBuffer>> FileOrErr =
         MemoryBuffer::getFile(Path);
     if (std::error_code EC = FileOrErr.getError()) {
diff --git a/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUAsmBackend.cpp b/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUAsmBackend.cpp
index 8fec80307a6e..1e66b3b0934c 100644
--- a/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUAsmBackend.cpp
+++ b/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUAsmBackend.cpp
@@ -190,8 +190,6 @@ public:
 MCAsmBackend *llvm::createAMDGPUAsmBackend(const Target &T,
                                            const MCRegisterInfo &MRI,
                                            const Triple &TT, StringRef CPU) {
-  Triple TargetTriple(TT);
-
   // Use 64-bit ELF for amdgcn
-  return new ELFAMDGPUAsmBackend(T, TargetTriple.getArch() == Triple::amdgcn);
+  return new ELFAMDGPUAsmBackend(T, TT.getArch() == Triple::amdgcn);
 }
diff --git a/llvm/lib/Target/ARM/ARMAsmPrinter.cpp b/llvm/lib/Target/ARM/ARMAsmPrinter.cpp
index 71823e470091..9ad7f9cc9d57 100644
--- a/llvm/lib/Target/ARM/ARMAsmPrinter.cpp
+++ b/llvm/lib/Target/ARM/ARMAsmPrinter.cpp
@@ -642,7 +642,7 @@ void ARMAsmPrinter::emitAttributes() {
       static_cast<const ARMBaseTargetMachine &>(TM);
   const ARMSubtarget STI(TT, CPU, ArchFS, ATM, ATM.isLittleEndian());
 
-  std::string CPUString = STI.getCPUString();
+  const std::string &CPUString = STI.getCPUString();
 
   if (CPUString.find("generic") != 0) { //CPUString doesn't start with "generic"
     // FIXME: remove krait check when GNU tools support krait cpu
diff --git a/llvm/lib/Target/Hexagon/AsmParser/HexagonAsmParser.cpp b/llvm/lib/Target/Hexagon/AsmParser/HexagonAsmParser.cpp
index c54a6b26c69a..633d1a476892 100644
--- a/llvm/lib/Target/Hexagon/AsmParser/HexagonAsmParser.cpp
+++ b/llvm/lib/Target/Hexagon/AsmParser/HexagonAsmParser.cpp
@@ -1401,7 +1401,6 @@ bool HexagonAsmParser::parseInstruction(OperandVector &Operands) {
       AsmToken const &Token = Parser.getTok();
       if (Token.is(AsmToken::Identifier)) {
         StringRef String = Token.getString();
-        AsmToken IDToken = Token;
         if (String.lower() == "hi") {
           HiOnly = true;
         } else if (String.lower() == "lo") {
diff --git a/llvm/lib/Target/Mips/AsmParser/MipsAsmParser.cpp b/llvm/lib/Target/Mips/AsmParser/MipsAsmParser.cpp
index 16ec118aba6d..b22a7fb0078f 100644
--- a/llvm/lib/Target/Mips/AsmParser/MipsAsmParser.cpp
+++ b/llvm/lib/Target/Mips/AsmParser/MipsAsmParser.cpp
@@ -438,7 +438,7 @@ public:
     IsCpRestoreSet = false;
     CpRestoreOffset = -1;
 
-    Triple TheTriple(sti.getTargetTriple());
+    const Triple &TheTriple = sti.getTargetTriple();
     if ((TheTriple.getArch() == Triple::mips) ||
         (TheTriple.getArch() == Triple::mips64))
       IsLittleEndian = false;
diff --git a/llvm/lib/Target/NVPTX/NVPTXAsmPrinter.cpp b/llvm/lib/Target/NVPTX/NVPTXAsmPrinter.cpp
index 50232c384dd2..a3c9657e9647 100644
--- a/llvm/lib/Target/NVPTX/NVPTXAsmPrinter.cpp
+++ b/llvm/lib/Target/NVPTX/NVPTXAsmPrinter.cpp
@@ -117,7 +117,7 @@ void NVPTXAsmPrinter::emitLineNumberAsDotLoc(const MachineInstr &MI) {
   if (ignoreLoc(MI))
     return;
 
-  DebugLoc curLoc = MI.getDebugLoc();
+  const DebugLoc &curLoc = MI.getDebugLoc();
 
   if (!prevDebugLoc && !curLoc)
     return;
diff --git a/llvm/lib/Target/PowerPC/AsmParser/PPCAsmParser.cpp b/llvm/lib/Target/PowerPC/AsmParser/PPCAsmParser.cpp
index 4b526fc6efec..cf8ee1d6a16f 100644
--- a/llvm/lib/Target/PowerPC/AsmParser/PPCAsmParser.cpp
+++ b/llvm/lib/Target/PowerPC/AsmParser/PPCAsmParser.cpp
@@ -292,7 +292,7 @@ public:
                const MCInstrInfo &MII, const MCTargetOptions &Options)
     : MCTargetAsmParser(Options, STI), MII(MII) {
     // Check for 64-bit vs. 32-bit pointer mode.
-    Triple TheTriple(STI.getTargetTriple());
+    const Triple &TheTriple = STI.getTargetTriple();
     IsPPC64 = (TheTriple.getArch() == Triple::ppc64 ||
                TheTriple.getArch() == Triple::ppc64le);
     IsDarwin = TheTriple.isMacOSX();
diff --git a/llvm/lib/Transforms/IPO/SampleProfile.cpp b/llvm/lib/Transforms/IPO/SampleProfile.cpp
index afafd45bec04..deba6ea0661d 100644
--- a/llvm/lib/Transforms/IPO/SampleProfile.cpp
+++ b/llvm/lib/Transforms/IPO/SampleProfile.cpp
@@ -445,7 +445,7 @@ void SampleProfileLoader::printBlockWeight(raw_ostream &OS,
 /// \returns the weight of \p Inst.
 ErrorOr<uint64_t>
 SampleProfileLoader::getInstWeight(const Instruction &Inst) const {
-  DebugLoc DLoc = Inst.getDebugLoc();
+  const DebugLoc &DLoc = Inst.getDebugLoc();
   if (!DLoc)
     return std::error_code();
 
diff --git a/llvm/lib/Transforms/Utils/CodeExtractor.cpp b/llvm/lib/Transforms/Utils/CodeExtractor.cpp
index 823696d88e65..3d2ee73669bc 100644
--- a/llvm/lib/Transforms/Utils/CodeExtractor.cpp
+++ b/llvm/lib/Transforms/Utils/CodeExtractor.cpp
@@ -77,15 +77,15 @@ static SetVector<BasicBlock *> buildExtractionBlockSet(IteratorT BBBegin,
 
   // Loop over the blocks, adding them to our set-vector, and aborting with an
   // empty set if we encounter invalid blocks.
-  for (IteratorT I = BBBegin, E = BBEnd; I != E; ++I) {
-    if (!Result.insert(*I))
+  do {
+    if (!Result.insert(*BBBegin))
       llvm_unreachable("Repeated basic blocks in extraction input");
 
-    if (!isBlockValidForExtraction(**I)) {
+    if (!isBlockValidForExtraction(**BBBegin)) {
       Result.clear();
       return Result;
     }
-  }
+  } while (++BBBegin != BBEnd);
 
 #ifndef NDEBUG
   for (SetVector<BasicBlock *>::iterator I = std::next(Result.begin()),
diff --git a/llvm/tools/llvm-dwarfdump/llvm-dwarfdump.cpp b/llvm/tools/llvm-dwarfdump/llvm-dwarfdump.cpp
index 415de6c591f3..fb6c7f4ffe8f 100644
--- a/llvm/tools/llvm-dwarfdump/llvm-dwarfdump.cpp
+++ b/llvm/tools/llvm-dwarfdump/llvm-dwarfdump.cpp
@@ -158,7 +158,7 @@ int main(int argc, char **argv) {
 
   // Expand any .dSYM bundles to the individual object files contained therein.
   std::vector<std::string> Objects;
-  for (auto F : InputFilenames) {
+  for (const auto &F : InputFilenames) {
     auto Objs = expandBundle(F);
     Objects.insert(Objects.end(), Objs.begin(), Objs.end());
   }
diff --git a/llvm/tools/sancov/sancov.cc b/llvm/tools/sancov/sancov.cc
index 891304d4f13d..efeb46a1faac 100644
--- a/llvm/tools/sancov/sancov.cc
+++ b/llvm/tools/sancov/sancov.cc
@@ -894,7 +894,7 @@ public:
     OS << "<table>\n";
     OS << "<tr><th>File</th><th>Coverage %</th>";
     OS << "<th>Hit (Total) Fns</th></tr>\n";
-    for (auto FileName : Files) {
+    for (const auto &FileName : Files) {
       std::pair<size_t, size_t> FC = FileCoverage[FileName];
       if (FC.first == 0) {
         NotCoveredFilesCount++;
@@ -915,7 +915,7 @@ public:
     if (NotCoveredFilesCount) {
       OS << "<details><summary>Not Touched Files</summary>\n";
       OS << "<table>\n";
-      for (auto FileName : Files) {
+      for (const auto &FileName : Files) {
         std::pair<size_t, size_t> FC = FileCoverage[FileName];
         if (FC.first == 0)
           OS << "<tr><td>" << stripPathPrefix(FileName) << "</td>\n";
@@ -927,7 +927,7 @@ public:
     }
 
     // Source
-    for (auto FileName : Files) {
+    for (const auto &FileName : Files) {
       std::pair<size_t, size_t> FC = FileCoverage[FileName];
       if (FC.first == 0)
         continue;
@@ -969,7 +969,7 @@ public:
           FileLoc Loc = FileLoc{FileName, Line};
           auto It = AllFnsByLoc.find(Loc);
           if (It != AllFnsByLoc.end()) {
-            for (std::string Fn : It->second) {
+            for (const std::string &Fn : It->second) {
               OS << "<a name=\"" << anchorName(FileName + "::" + Fn)
                  << "\"></a>";
             };
@@ -1069,7 +1069,7 @@ public:
     std::vector<std::unique_ptr<CoverageDataWithObjectFile>> MergedCoverage;
     for (const auto &Pair : CoverageByObjFile) {
       if (findSanitizerCovFunctions(Pair.first).empty()) {
-        for (auto FileName : Pair.second) {
+        for (const auto &FileName : Pair.second) {
           CovFiles.erase(FileName);
         }
 
@@ -1159,7 +1159,7 @@ public:
     // About
     OS << "<details><summary>About</summary>\n";
     OS << "Coverage files:<ul>";
-    for (auto InputFile : CoverageFiles) {
+    for (const auto &InputFile : CoverageFiles) {
       llvm::sys::fs::file_status Status;
       llvm::sys::fs::status(InputFile, Status);
       OS << "<li>" << stripPathPrefix(InputFile) << " ("
@@ -1209,7 +1209,7 @@ int main(int argc, char **argv) {
     return 0;
   } else if (Action == PrintCovPointsAction) {
     // -print-coverage-points doesn't need coverage files.
-    for (std::string ObjFile : ClInputFiles) {
+    for (const std::string &ObjFile : ClInputFiles) {
       printCovPoints(ObjFile, outs());
     }
     return 0;
diff --git a/llvm/tools/yaml2obj/yaml2macho.cpp b/llvm/tools/yaml2obj/yaml2macho.cpp
index 57f36d6a90d4..9faa767e9a6e 100644
--- a/llvm/tools/yaml2obj/yaml2macho.cpp
+++ b/llvm/tools/yaml2obj/yaml2macho.cpp
@@ -116,7 +116,7 @@ template <>
 size_t writeLoadCommandData<MachO::segment_command>(MachOYAML::LoadCommand &LC,
                                                     raw_ostream &OS) {
   size_t BytesWritten = 0;
-  for (auto Sec : LC.Sections) {
+  for (const auto &Sec : LC.Sections) {
     auto TempSec = constructSection<MachO::section>(Sec);
     OS.write(reinterpret_cast<const char *>(&(TempSec)),
              sizeof(MachO::section));
@@ -130,7 +130,7 @@ size_t
 writeLoadCommandData<MachO::segment_command_64>(MachOYAML::LoadCommand &LC,
                                                 raw_ostream &OS) {
   size_t BytesWritten = 0;
-  for (auto Sec : LC.Sections) {
+  for (const auto &Sec : LC.Sections) {
     auto TempSec = constructSection<MachO::section_64>(Sec);
     TempSec.reserved3 = Sec.reserved3;
     OS.write(reinterpret_cast<const char *>(&(TempSec)),
diff --git a/llvm/utils/TableGen/RegisterInfoEmitter.cpp b/llvm/utils/TableGen/RegisterInfoEmitter.cpp
index 60ddb5c88ece..9bb988f30f18 100644
--- a/llvm/utils/TableGen/RegisterInfoEmitter.cpp
+++ b/llvm/utils/TableGen/RegisterInfoEmitter.cpp
@@ -990,7 +990,7 @@ RegisterInfoEmitter::runMCDesc(raw_ostream &OS, CodeGenTarget &Target,
     ArrayRef<Record*> Order = RC.getOrder();
 
     // Give the register class a legal C name if it's anonymous.
-    std::string Name = RC.getName();
+    const std::string &Name = RC.getName();
 
     RegClassStrings.add(Name);