diff --git a/llvm/lib/Transforms/IPO/Attributor.cpp b/llvm/lib/Transforms/IPO/Attributor.cpp
index efbc950496b69..fdbed1b62fdcd 100644
--- a/llvm/lib/Transforms/IPO/Attributor.cpp
+++ b/llvm/lib/Transforms/IPO/Attributor.cpp
@@ -977,7 +977,7 @@ bool IRPosition::getAttrsFromAssumes(Attribute::AttrKind AK,
   MustBeExecutedContextExplorer &Explorer =
       A.getInfoCache().getMustBeExecutedContextExplorer();
   auto EIt = Explorer.begin(getCtxI()), EEnd = Explorer.end(getCtxI());
-  for (auto &It : A2K)
+  for (const auto &It : A2K)
     if (Explorer.findInContextOf(It.first, EIt, EEnd))
       Attrs.push_back(Attribute::get(Ctx, AK, It.second.Max));
   return AttrsSize != Attrs.size();
@@ -1113,7 +1113,7 @@ bool Attributor::getAssumedSimplifiedValues(
   // a non-null value that is different from the associated value, or None, we
   // assume it's simplified.
   const auto &SimplificationCBs = SimplificationCallbacks.lookup(IRP);
-  for (auto &CB : SimplificationCBs) {
+  for (const auto &CB : SimplificationCBs) {
     Optional<Value *> CBResult = CB(IRP, AA, UsedAssumedInformation);
     if (!CBResult.has_value())
       continue;
@@ -2079,7 +2079,7 @@ ChangeStatus Attributor::cleanupIR() {
     }
   }
 
-  for (auto &V : InvokeWithDeadSuccessor)
+  for (const auto &V : InvokeWithDeadSuccessor)
     if (InvokeInst *II = dyn_cast_or_null<InvokeInst>(V)) {
       assert(isRunOn(*II->getFunction()) &&
              "Cannot replace an invoke outside the current SCC!");
@@ -2112,7 +2112,7 @@ ChangeStatus Attributor::cleanupIR() {
     CGModifiedFunctions.insert(I->getFunction());
     ConstantFoldTerminator(I->getParent());
   }
-  for (auto &V : ToBeChangedToUnreachableInsts)
+  for (const auto &V : ToBeChangedToUnreachableInsts)
     if (Instruction *I = dyn_cast_or_null<Instruction>(V)) {
       LLVM_DEBUG(dbgs() << "[Attributor] Change to unreachable: " << *I
                         << "\n");
@@ -2122,7 +2122,7 @@ ChangeStatus Attributor::cleanupIR() {
       changeToUnreachable(I);
     }
 
-  for (auto &V : ToBeDeletedInsts) {
+  for (const auto &V : ToBeDeletedInsts) {
     if (Instruction *I = dyn_cast_or_null<Instruction>(V)) {
       if (auto *CB = dyn_cast<CallBase>(I)) {
         assert(isRunOn(*I->getFunction()) &&
@@ -3190,7 +3190,7 @@ raw_ostream &llvm::operator<<(raw_ostream &OS,
   if (!S.isValidState())
     OS << "full-set";
   else {
-    for (auto &It : S.getAssumedSet())
+    for (const auto &It : S.getAssumedSet())
       OS << It << ", ";
     if (S.undefIsContained())
       OS << "undef ";
@@ -3206,7 +3206,7 @@ raw_ostream &llvm::operator<<(raw_ostream &OS,
   if (!S.isValidState())
     OS << "full-set";
   else {
-    for (auto &It : S.getAssumedSet()) {
+    for (const auto &It : S.getAssumedSet()) {
       if (auto *F = dyn_cast<Function>(It.first.getValue()))
         OS << "@" << F->getName() << "[" << int(It.second) << "], ";
       else
diff --git a/llvm/lib/Transforms/IPO/AttributorAttributes.cpp b/llvm/lib/Transforms/IPO/AttributorAttributes.cpp
index fa4e33a820edd..cf64ff5885f2f 100644
--- a/llvm/lib/Transforms/IPO/AttributorAttributes.cpp
+++ b/llvm/lib/Transforms/IPO/AttributorAttributes.cpp
@@ -891,7 +891,7 @@ struct AA::PointerInfo::State : public AbstractState {
     if (!isValidState())
       return false;
 
-    for (auto &It : AccessBins) {
+    for (const auto &It : AccessBins) {
       AAPointerInfo::OffsetAndSize ItOAS = It.getFirst();
       if (!OAS.mayOverlap(ItOAS))
         continue;
@@ -912,7 +912,7 @@ struct AA::PointerInfo::State : public AbstractState {
 
     // First find the offset and size of I.
     AAPointerInfo::OffsetAndSize OAS(-1, -1);
-    for (auto &It : AccessBins) {
+    for (const auto &It : AccessBins) {
       for (auto &Access : *It.getSecond()) {
         if (Access.getRemoteInst() == &I) {
           OAS = It.getFirst();
@@ -1148,7 +1148,7 @@ struct AAPointerInfoImpl
 
     // Combine the accesses bin by bin.
     ChangeStatus Changed = ChangeStatus::UNCHANGED;
-    for (auto &It : OtherAAImpl.getState()) {
+    for (const auto &It : OtherAAImpl.getState()) {
       OffsetAndSize OAS = OffsetAndSize::getUnknown();
       if (Offset != OffsetAndSize::Unknown)
         OAS = OffsetAndSize(It.first.getOffset() + Offset, It.first.getSize());
@@ -1802,7 +1802,7 @@ bool AAReturnedValuesImpl::checkForAllReturnedValuesAndReturnInsts(
 
   // Check all returned values but ignore call sites as long as we have not
   // encountered an overdefined one during an update.
-  for (auto &It : ReturnedValues) {
+  for (const auto &It : ReturnedValues) {
     Value *RV = It.first;
     if (!Pred(*RV, It.second))
       return false;
@@ -3977,7 +3977,7 @@ identifyAliveSuccessors(Attributor &A, const SwitchInst &SI,
   if (!C || isa_and_nonnull<UndefValue>(C.value())) {
     // No value yet, assume all edges are dead.
   } else if (isa_and_nonnull<ConstantInt>(C.value())) {
-    for (auto &CaseIt : SI.cases()) {
+    for (const auto &CaseIt : SI.cases()) {
       if (CaseIt.getCaseValue() == C.value()) {
         AliveSuccessors.push_back(&CaseIt.getCaseSuccessor()->front());
         return UsedAssumedInformation;
@@ -5141,7 +5141,7 @@ ChangeStatus AANoCaptureImpl::updateImpl(Attributor &A) {
     if (!RVAA.getState().isValidState())
       return false;
     bool SeenConstant = false;
-    for (auto &It : RVAA.returned_values()) {
+    for (const auto &It : RVAA.returned_values()) {
       if (isa<Constant>(It.first)) {
         if (SeenConstant)
           return false;
@@ -5902,7 +5902,7 @@ struct AAHeapToStackFunction final : public AAHeapToStack {
     STATS_DECL(
         MallocCalls, Function,
         "Number of malloc/calloc/aligned_alloc calls converted to allocas");
-    for (auto &It : AllocationInfos)
+    for (const auto &It : AllocationInfos)
       if (It.second->Status != AllocationInfo::INVALID)
         ++BUILD_STAT_NAME(MallocCalls, Function);
   }
@@ -5919,7 +5919,7 @@ struct AAHeapToStackFunction final : public AAHeapToStack {
     if (!isValidState())
       return false;
 
-    for (auto &It : AllocationInfos) {
+    for (const auto &It : AllocationInfos) {
       AllocationInfo &AI = *It.second;
       if (AI.Status == AllocationInfo::INVALID)
         continue;
@@ -8980,7 +8980,7 @@ struct AAPotentialConstantValuesFloating : AAPotentialConstantValuesImpl {
       if (Undef)
         unionAssumedWithUndef();
       else {
-        for (auto &It : *OpAA)
+        for (const auto &It : *OpAA)
           unionAssumed(It);
       }
 
@@ -8988,9 +8988,9 @@ struct AAPotentialConstantValuesFloating : AAPotentialConstantValuesImpl {
       // select i1 *, undef , undef => undef
       unionAssumedWithUndef();
     } else {
-      for (auto &It : LHSAAPVS)
+      for (const auto &It : LHSAAPVS)
         unionAssumed(It);
-      for (auto &It : RHSAAPVS)
+      for (const auto &It : RHSAAPVS)
         unionAssumed(It);
     }
     return AssumedBefore == getAssumed() ? ChangeStatus::UNCHANGED
@@ -9416,7 +9416,7 @@ struct AACallEdgesCallSite : public AACallEdgesImpl {
 
     // Process callee metadata if available.
     if (auto *MD = getCtxI()->getMetadata(LLVMContext::MD_callees)) {
-      for (auto &Op : MD->operands()) {
+      for (const auto &Op : MD->operands()) {
         Function *Callee = mdconst::dyn_extract_or_null<Function>(Op);
         if (Callee)
           addCalledFunction(Callee, Change);
@@ -9571,7 +9571,7 @@ struct AAFunctionReachabilityFunction : public AAFunctionReachability {
       }
 
       SmallVector<const AAFunctionReachability *, 8> Deps;
-      for (auto &AAEdges : AAEdgesList) {
+      for (const auto &AAEdges : AAEdgesList) {
         const SetVector<Function *> &Edges = AAEdges->getOptimisticEdges();
 
         for (Function *Edge : Edges) {
@@ -9851,7 +9851,7 @@ struct AAPotentialValuesImpl : AAPotentialValues {
 
     IRPosition ValIRP = IRPosition::value(V);
     if (auto *CB = dyn_cast_or_null<CallBase>(CtxI)) {
-      for (auto &U : CB->args()) {
+      for (const auto &U : CB->args()) {
         if (U.get() != &V)
           continue;
         ValIRP = IRPosition::callsite_argument(*CB, CB->getArgOperandNo(&U));
@@ -9868,7 +9868,7 @@ struct AAPotentialValuesImpl : AAPotentialValues {
         auto &PotentialConstantsAA = A.getAAFor<AAPotentialConstantValues>(
             *this, ValIRP, DepClassTy::OPTIONAL);
         if (PotentialConstantsAA.isValidState()) {
-          for (auto &It : PotentialConstantsAA.getAssumedSet())
+          for (const auto &It : PotentialConstantsAA.getAssumedSet())
             State.unionAssumed({{*ConstantInt::get(&Ty, It), nullptr}, S});
           if (PotentialConstantsAA.undefIsContained())
             State.unionAssumed({{*UndefValue::get(&Ty), nullptr}, S});
@@ -9930,7 +9930,7 @@ struct AAPotentialValuesImpl : AAPotentialValues {
 
   void giveUpOnIntraprocedural(Attributor &A) {
     auto NewS = StateType::getBestState(getState());
-    for (auto &It : getAssumedSet()) {
+    for (const auto &It : getAssumedSet()) {
       if (It.second == AA::Intraprocedural)
         continue;
       addValue(A, NewS, *It.first.getValue(), It.first.getCtxI(),
@@ -9982,7 +9982,7 @@ struct AAPotentialValuesImpl : AAPotentialValues {
                                   AA::ValueScope S) const override {
     if (!isValidState())
       return false;
-    for (auto &It : getAssumedSet())
+    for (const auto &It : getAssumedSet())
       if (It.second & S)
         Values.push_back(It.first);
     assert(!undefIsContained() && "Undef should be an explicit value!");
diff --git a/llvm/lib/Transforms/IPO/FunctionAttrs.cpp b/llvm/lib/Transforms/IPO/FunctionAttrs.cpp
index 399dc00a2a279..73ebb27b59621 100644
--- a/llvm/lib/Transforms/IPO/FunctionAttrs.cpp
+++ b/llvm/lib/Transforms/IPO/FunctionAttrs.cpp
@@ -517,7 +517,7 @@ bool llvm::thinLTOPropagateFunctionAttrs(
           ++NumThinLinkNoUnwind;
         }
 
-        for (auto &S : V.getSummaryList()) {
+        for (const auto &S : V.getSummaryList()) {
           if (auto *FS = dyn_cast<FunctionSummary>(S.get())) {
             if (InferredFlags.NoRecurse)
               FS->setNoRecurse();
diff --git a/llvm/lib/Transforms/IPO/GlobalOpt.cpp b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
index 1fd8133550b42..a7665f50a5eee 100644
--- a/llvm/lib/Transforms/IPO/GlobalOpt.cpp
+++ b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
@@ -2397,7 +2397,7 @@ static bool cxxDtorIsEmpty(const Function &Fn) {
   if (Fn.isDeclaration())
     return false;
 
-  for (auto &I : Fn.getEntryBlock()) {
+  for (const auto &I : Fn.getEntryBlock()) {
     if (I.isDebugOrPseudoInst())
       continue;
     if (isa<ReturnInst>(I))
diff --git a/llvm/lib/Transforms/IPO/LowerTypeTests.cpp b/llvm/lib/Transforms/IPO/LowerTypeTests.cpp
index e3e4908f085bc..69f7aba8b9be1 100644
--- a/llvm/lib/Transforms/IPO/LowerTypeTests.cpp
+++ b/llvm/lib/Transforms/IPO/LowerTypeTests.cpp
@@ -539,7 +539,7 @@ BitSetInfo LowerTypeTestsModule::buildBitSet(
 
   // Compute the byte offset of each address associated with this type
   // identifier.
-  for (auto &GlobalAndOffset : GlobalLayout) {
+  for (const auto &GlobalAndOffset : GlobalLayout) {
     for (MDNode *Type : GlobalAndOffset.first->types()) {
       if (Type->getOperand(1) != TypeId)
         continue;
@@ -1912,7 +1912,7 @@ bool LowerTypeTestsModule::lower() {
     for (auto &I : *ExportSummary)
       for (auto &GVS : I.second.SummaryList)
         if (GVS->isLive())
-          for (auto &Ref : GVS->refs())
+          for (const auto &Ref : GVS->refs())
             AddressTaken.insert(Ref.getGUID());
 
     NamedMDNode *CfiFunctionsMD = M.getNamedMetadata("cfi.functions");
@@ -1938,7 +1938,7 @@ bool LowerTypeTestsModule::lower() {
 
           bool Exported = false;
           if (auto VI = ExportSummary->getValueInfo(GUID))
-            for (auto &GVS : VI.getSummaryList())
+            for (const auto &GVS : VI.getSummaryList())
               if (GVS->isLive() && !GlobalValue::isLocalLinkage(GVS->linkage()))
                 Exported = true;
 
diff --git a/llvm/lib/Transforms/IPO/SampleProfile.cpp b/llvm/lib/Transforms/IPO/SampleProfile.cpp
index bec390ef37552..92cb7bd7976e7 100644
--- a/llvm/lib/Transforms/IPO/SampleProfile.cpp
+++ b/llvm/lib/Transforms/IPO/SampleProfile.cpp
@@ -363,7 +363,7 @@ class GUIDToFuncNameMapper {
       FS->GUIDToFuncNameMap = Map;
       for (const auto &ICS : FS->getCallsiteSamples()) {
         const FunctionSamplesMap &FSMap = ICS.second;
-        for (auto &IFS : FSMap) {
+        for (const auto &IFS : FSMap) {
           FunctionSamples &FS = const_cast<FunctionSamples &>(IFS.second);
           FSToUpdate.push(&FS);
         }
diff --git a/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp b/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp
index 18efe99f7cb48..6b50239463418 100644
--- a/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp
+++ b/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp
@@ -387,7 +387,7 @@ bool mustBeUnreachableFunction(ValueInfo TheFnVI) {
     return false;
   }
 
-  for (auto &Summary : TheFnVI.getSummaryList()) {
+  for (const auto &Summary : TheFnVI.getSummaryList()) {
     // Conservatively returns false if any non-live functions are seen.
     // In general either all summaries should be live or all should be dead.
     if (!Summary->isLive())
@@ -1048,7 +1048,7 @@ bool DevirtIndex::tryFindVirtualCallTargets(
     // conservatively return false early.
     const GlobalVarSummary *VS = nullptr;
     bool LocalFound = false;
-    for (auto &S : P.VTableVI.getSummaryList()) {
+    for (const auto &S : P.VTableVI.getSummaryList()) {
       if (GlobalValue::isLocalLinkage(S->linkage())) {
         if (LocalFound)
           return false;
@@ -1278,7 +1278,7 @@ bool DevirtIndex::trySingleImplDevirt(MutableArrayRef<ValueInfo> TargetsForSlot,
 
   // If the summary list contains multiple summaries where at least one is
   // a local, give up, as we won't know which (possibly promoted) name to use.
-  for (auto &S : TheFn.getSummaryList())
+  for (const auto &S : TheFn.getSummaryList())
     if (GlobalValue::isLocalLinkage(S->linkage()) && Size > 1)
       return false;
 
@@ -2309,7 +2309,7 @@ void DevirtIndex::run() {
     return;
 
   DenseMap<GlobalValue::GUID, std::vector<StringRef>> NameByGUID;
-  for (auto &P : ExportSummary.typeIdCompatibleVtableMap()) {
+  for (const auto &P : ExportSummary.typeIdCompatibleVtableMap()) {
     NameByGUID[GlobalValue::getGUID(P.first)].push_back(P.first);
   }
 
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index dd03f98c5be78..de551e049035d 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -3218,7 +3218,7 @@ Instruction *InstCombinerImpl::visitSwitchInst(SwitchInst &SI) {
 
   // Compute the number of leading bits we can ignore.
   // TODO: A better way to determine this would use ComputeNumSignBits().
-  for (auto &C : SI.cases()) {
+  for (const auto &C : SI.cases()) {
     LeadingKnownZeros = std::min(
         LeadingKnownZeros, C.getCaseValue()->getValue().countLeadingZeros());
     LeadingKnownOnes = std::min(
@@ -4377,7 +4377,7 @@ class AliasScopeTracker {
       const auto *MDScopeList = dyn_cast_or_null<MDNode>(ScopeList);
       if (!MDScopeList || !Container.insert(MDScopeList).second)
         return;
-      for (auto &MDOperand : MDScopeList->operands())
+      for (const auto &MDOperand : MDScopeList->operands())
         if (auto *MDScope = dyn_cast<MDNode>(MDOperand))
           Container.insert(MDScope);
     };
diff --git a/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp b/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
index b856772b13a86..ca3c4ba578df4 100644
--- a/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
+++ b/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
@@ -992,7 +992,7 @@ struct UseBBInfo : public BBInfo {
 // Sum up the count values for all the edges.
 static uint64_t sumEdgeCount(const ArrayRef<PGOUseEdge *> Edges) {
   uint64_t Total = 0;
-  for (auto &E : Edges) {
+  for (const auto &E : Edges) {
     if (E->Removed)
       continue;
     Total += E->CountValue;
@@ -1204,7 +1204,7 @@ static void annotateFunctionWithHashMismatch(Function &F,
   auto *Existing = F.getMetadata(LLVMContext::MD_annotation);
   if (Existing) {
     MDTuple *Tuple = cast<MDTuple>(Existing);
-    for (auto &N : Tuple->operands()) {
+    for (const auto &N : Tuple->operands()) {
       if (cast<MDString>(N.get())->getString() ==  MetadataName)
         return;
       Names.push_back(N.get());
diff --git a/llvm/lib/Transforms/ObjCARC/ObjCARCOpts.cpp b/llvm/lib/Transforms/ObjCARC/ObjCARCOpts.cpp
index da360acbbb378..5044d47fd37c5 100644
--- a/llvm/lib/Transforms/ObjCARC/ObjCARCOpts.cpp
+++ b/llvm/lib/Transforms/ObjCARC/ObjCARCOpts.cpp
@@ -1503,7 +1503,7 @@ static void collectReleaseInsertPts(
     const BlotMapVector<Value *, RRInfo> &Retains,
     DenseMap<const Instruction *, SmallPtrSet<const Value *, 2>>
         &ReleaseInsertPtToRCIdentityRoots) {
-  for (auto &P : Retains) {
+  for (const auto &P : Retains) {
     // Retains is a map from an objc_retain call to a RRInfo of the RC identity
     // root of the call. Get the RC identity root of the objc_retain call.
     Instruction *Retain = cast<Instruction>(P.first);
diff --git a/llvm/lib/Transforms/Scalar/ADCE.cpp b/llvm/lib/Transforms/Scalar/ADCE.cpp
index cdf9de8d78d52..1c1f838252a99 100644
--- a/llvm/lib/Transforms/Scalar/ADCE.cpp
+++ b/llvm/lib/Transforms/Scalar/ADCE.cpp
@@ -295,7 +295,7 @@ void AggressiveDeadCodeElimination::initialize() {
   // return of the function.
   // We do this by seeing which of the postdomtree root children exit the
   // program, and for all others, mark the subtree live.
-  for (auto &PDTChild : children<DomTreeNode *>(PDT.getRootNode())) {
+  for (const auto &PDTChild : children<DomTreeNode *>(PDT.getRootNode())) {
     auto *BB = PDTChild->getBlock();
     auto &Info = BlockInfo[BB];
     // Real function return
diff --git a/llvm/lib/Transforms/Scalar/CallSiteSplitting.cpp b/llvm/lib/Transforms/Scalar/CallSiteSplitting.cpp
index cc12033fb6774..310188de280a8 100644
--- a/llvm/lib/Transforms/Scalar/CallSiteSplitting.cpp
+++ b/llvm/lib/Transforms/Scalar/CallSiteSplitting.cpp
@@ -165,7 +165,7 @@ static void recordConditions(CallBase &CB, BasicBlock *Pred,
 }
 
 static void addConditions(CallBase &CB, const ConditionsTy &Conditions) {
-  for (auto &Cond : Conditions) {
+  for (const auto &Cond : Conditions) {
     Value *Arg = Cond.first->getOperand(0);
     Constant *ConstVal = cast<Constant>(Cond.first->getOperand(1));
     if (Cond.second == ICmpInst::ICMP_EQ)
diff --git a/llvm/lib/Transforms/Scalar/GVN.cpp b/llvm/lib/Transforms/Scalar/GVN.cpp
index afff8a8cfea1d..fd8e4890f4541 100644
--- a/llvm/lib/Transforms/Scalar/GVN.cpp
+++ b/llvm/lib/Transforms/Scalar/GVN.cpp
@@ -1900,7 +1900,7 @@ bool GVNPass::processAssumeIntrinsic(AssumeInst *IntrinsicI) {
         // after the found access or before the terminator if no such access is
         // found.
         if (AL) {
-          for (auto &Acc : *AL) {
+          for (const auto &Acc : *AL) {
             if (auto *Current = dyn_cast<MemoryUseOrDef>(&Acc))
               if (!Current->getMemoryInst()->comesBefore(NewS)) {
                 FirstNonDom = Current;
diff --git a/llvm/lib/Transforms/Scalar/GVNHoist.cpp b/llvm/lib/Transforms/Scalar/GVNHoist.cpp
index 6cdc671ddb649..5960dffa65ec4 100644
--- a/llvm/lib/Transforms/Scalar/GVNHoist.cpp
+++ b/llvm/lib/Transforms/Scalar/GVNHoist.cpp
@@ -435,7 +435,7 @@ class GVNHoist {
         continue;
       const VNType &VN = R;
       SmallPtrSet<BasicBlock *, 2> VNBlocks;
-      for (auto &I : V) {
+      for (const auto &I : V) {
         BasicBlock *BBI = I->getParent();
         if (!hasEH(BBI))
           VNBlocks.insert(BBI);
@@ -563,7 +563,7 @@ bool GVNHoist::run(Function &F) {
   for (const BasicBlock *BB : depth_first(&F.getEntryBlock())) {
     DFSNumber[BB] = ++BBI;
     unsigned I = 0;
-    for (auto &Inst : *BB)
+    for (const auto &Inst : *BB)
       DFSNumber[&Inst] = ++I;
   }
 
diff --git a/llvm/lib/Transforms/Scalar/LoopDeletion.cpp b/llvm/lib/Transforms/Scalar/LoopDeletion.cpp
index 93f3cd704196c..bf5c1f4b9a67b 100644
--- a/llvm/lib/Transforms/Scalar/LoopDeletion.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopDeletion.cpp
@@ -106,7 +106,7 @@ static bool isLoopDead(Loop *L, ScalarEvolution &SE,
   // Make sure that no instructions in the block have potential side-effects.
   // This includes instructions that could write to memory, and loads that are
   // marked volatile.
-  for (auto &I : L->blocks())
+  for (const auto &I : L->blocks())
     if (any_of(*I, [](Instruction &I) {
           return I.mayHaveSideEffects() && !I.isDroppable();
         }))
diff --git a/llvm/lib/Transforms/Scalar/LoopDistribute.cpp b/llvm/lib/Transforms/Scalar/LoopDistribute.cpp
index 9cf7ee2f6a364..f7f74675b290f 100644
--- a/llvm/lib/Transforms/Scalar/LoopDistribute.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopDistribute.cpp
@@ -633,7 +633,7 @@ class MemoryInstructionDependences {
     Accesses.append(Instructions.begin(), Instructions.end());
 
     LLVM_DEBUG(dbgs() << "Backward dependences:\n");
-    for (auto &Dep : Dependences)
+    for (const auto &Dep : Dependences)
       if (Dep.isPossiblyBackward()) {
         // Note that the designations source and destination follow the program
         // order, i.e. source is always first.  (The direction is given by the
@@ -715,7 +715,7 @@ class LoopDistributeForLoop {
                                      *Dependences);
 
     int NumUnsafeDependencesActive = 0;
-    for (auto &InstDep : MID) {
+    for (const auto &InstDep : MID) {
       Instruction *I = InstDep.Inst;
       // We update NumUnsafeDependencesActive post-instruction, catch the
       // start of a dependence directly via NumUnsafeDependencesStartOrEnd.
diff --git a/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index 0a17b777797ec..c3033070a0d46 100644
--- a/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -5980,7 +5980,7 @@ struct SCEVDbgValueBuilder {
            "Expected arithmetic SCEV type");
     bool Success = true;
     unsigned EmitOperator = 0;
-    for (auto &Op : CommExpr->operands()) {
+    for (const auto &Op : CommExpr->operands()) {
       Success &= pushSCEV(Op);
 
       if (EmitOperator >= 1)
@@ -6490,7 +6490,7 @@ static void DbgGatherSalvagableDVI(
     Loop *L, ScalarEvolution &SE,
     SmallVector<std::unique_ptr<DVIRecoveryRec>, 2> &SalvageableDVISCEVs,
     SmallSet<AssertingVH<DbgValueInst>, 2> &DVIHandles) {
-  for (auto &B : L->getBlocks()) {
+  for (const auto &B : L->getBlocks()) {
     for (auto &I : *B) {
       auto DVI = dyn_cast<DbgValueInst>(&I);
       if (!DVI)
@@ -6637,7 +6637,7 @@ static bool ReduceLoopStrength(Loop *L, IVUsers &IU, ScalarEvolution &SE,
   // Obtain relevant IVs and attempt to rewrite the salvageable DVIs with
   // expressions composed using the derived iteration count.
   // TODO: Allow for multiple IV references for nested AddRecSCEVs
-  for (auto &L : LI) {
+  for (const auto &L : LI) {
     if (llvm::PHINode *IV = GetInductionVariable(*L, SE, Reducer))
       DbgRewriteSalvageableDVIs(L, SE, IV, SalvageableDVIRecords);
     else {
diff --git a/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp b/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
index ca9ab3edcd0da..f993282b2e7d0 100644
--- a/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
@@ -1583,7 +1583,7 @@ PreservedAnalyses LoopUnrollPass::run(Function &F,
   // legality and profitability checks. This means running the loop unroller
   // will simplify all loops, regardless of whether anything end up being
   // unrolled.
-  for (auto &L : LI) {
+  for (const auto &L : LI) {
     Changed |=
         simplifyLoop(L, &DT, &LI, &SE, &AC, nullptr, false /* PreserveLCSSA */);
     Changed |= formLCSSARecursively(*L, DT, &LI, &SE);
diff --git a/llvm/lib/Transforms/Scalar/LowerMatrixIntrinsics.cpp b/llvm/lib/Transforms/Scalar/LowerMatrixIntrinsics.cpp
index c4281b6060fe1..4c434155d162a 100644
--- a/llvm/lib/Transforms/Scalar/LowerMatrixIntrinsics.cpp
+++ b/llvm/lib/Transforms/Scalar/LowerMatrixIntrinsics.cpp
@@ -2176,7 +2176,7 @@ class LowerMatrixIntrinsics {
       // the inlinedAt chain. If the function does not have a DISubprogram, we
       // only map them to the containing function.
       MapVector<DISubprogram *, SmallVector<Value *, 8>> Subprog2Exprs;
-      for (auto &KV : Inst2Matrix) {
+      for (const auto &KV : Inst2Matrix) {
         if (Func.getSubprogram()) {
           auto *I = cast<Instruction>(KV.first);
           DILocation *Context = I->getDebugLoc();
diff --git a/llvm/lib/Transforms/Scalar/NewGVN.cpp b/llvm/lib/Transforms/Scalar/NewGVN.cpp
index 955138bb511a8..7ea081f7e1ee5 100644
--- a/llvm/lib/Transforms/Scalar/NewGVN.cpp
+++ b/llvm/lib/Transforms/Scalar/NewGVN.cpp
@@ -207,7 +207,7 @@ struct TarjanSCC {
     Root[I] = ++DFSNum;
     // Store the DFS Number we had before it possibly gets incremented.
     unsigned int OurDFS = DFSNum;
-    for (auto &Op : I->operands()) {
+    for (const auto &Op : I->operands()) {
       if (auto *InstOp = dyn_cast<Instruction>(Op)) {
         if (Root.lookup(Op) == 0)
           FindSCC(InstOp);
@@ -3218,7 +3218,7 @@ void NewGVN::verifyMemoryCongruency() const {
         // We could have phi nodes which operands are all trivially dead,
         // so we don't process them.
         if (auto *MemPHI = dyn_cast<MemoryPhi>(Pair.first)) {
-          for (auto &U : MemPHI->incoming_values()) {
+          for (const auto &U : MemPHI->incoming_values()) {
             if (auto *I = dyn_cast<Instruction>(&*U)) {
               if (!isInstructionTriviallyDead(I))
                 return true;
diff --git a/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp
index 01c0bf7786aca..8a4477d16d5ce 100644
--- a/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp
+++ b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp
@@ -1592,7 +1592,7 @@ deleteDeadClonedBlocks(Loop &L, ArrayRef<BasicBlock *> ExitBlocks,
   // Find all the dead clones, and remove them from their successors.
   SmallVector<BasicBlock *, 16> DeadBlocks;
   for (BasicBlock *BB : llvm::concat<BasicBlock *const>(L.blocks(), ExitBlocks))
-    for (auto &VMap : VMaps)
+    for (const auto &VMap : VMaps)
       if (BasicBlock *ClonedBB = cast_or_null<BasicBlock>(VMap->lookup(BB)))
         if (!DT.isReachableFromEntry(ClonedBB)) {
           for (BasicBlock *SuccBB : successors(ClonedBB))
@@ -2247,7 +2247,7 @@ static void unswitchNontrivialInvariants(
       assert(SI->getDefaultDest() == RetainedSuccBB &&
              "Not retaining default successor!");
       SI->setDefaultDest(LoopPH);
-      for (auto &Case : SI->cases())
+      for (const auto &Case : SI->cases())
         if (Case.getCaseSuccessor() == RetainedSuccBB)
           Case.setSuccessor(LoopPH);
         else
@@ -2308,7 +2308,7 @@ static void unswitchNontrivialInvariants(
       SwitchInst *NewSI = cast<SwitchInst>(NewTI);
       assert(NewSI->getDefaultDest() == RetainedSuccBB &&
              "Not retaining default successor!");
-      for (auto &Case : NewSI->cases())
+      for (const auto &Case : NewSI->cases())
         Case.getCaseSuccessor()->removePredecessor(
             ParentBB,
             /*KeepOneInputPHIs*/ true);
diff --git a/llvm/lib/Transforms/Utils/CodeLayout.cpp b/llvm/lib/Transforms/Utils/CodeLayout.cpp
index b58e18585dca6..faf1d69ac6ea1 100644
--- a/llvm/lib/Transforms/Utils/CodeLayout.cpp
+++ b/llvm/lib/Transforms/Utils/CodeLayout.cpp
@@ -666,7 +666,7 @@ class ExtTSPImpl {
     });
 
     double Score = 0;
-    for (auto &Jump : Jumps) {
+    for (const auto &Jump : Jumps) {
       const auto SrcBlock = Jump->Source;
       const auto DstBlock = Jump->Target;
       Score += ::extTSPScore(SrcBlock->EstimatedAddr, SrcBlock->Size,
@@ -711,7 +711,7 @@ class ExtTSPImpl {
         return;
       // Apply the merge, compute the corresponding gain, and update the best
       // value, if the merge is beneficial
-      for (auto &MergeType : MergeTypes) {
+      for (const auto &MergeType : MergeTypes) {
         Gain.updateIfLessThan(
             computeMergeGain(ChainPred, ChainSucc, Jumps, Offset, MergeType));
       }
diff --git a/llvm/lib/Transforms/Utils/FunctionImportUtils.cpp b/llvm/lib/Transforms/Utils/FunctionImportUtils.cpp
index a30f920d0036a..87be6be018857 100644
--- a/llvm/lib/Transforms/Utils/FunctionImportUtils.cpp
+++ b/llvm/lib/Transforms/Utils/FunctionImportUtils.cpp
@@ -226,7 +226,7 @@ void FunctionImportGlobalProcessing::processGlobalForThinLTO(GlobalValue &GV) {
     if (VI && ImportIndex.hasSyntheticEntryCounts()) {
       if (Function *F = dyn_cast<Function>(&GV)) {
         if (!F->isDeclaration()) {
-          for (auto &S : VI.getSummaryList()) {
+          for (const auto &S : VI.getSummaryList()) {
             auto *FS = cast<FunctionSummary>(S->getBaseObject());
             if (FS->modulePath() == M.getModuleIdentifier()) {
               F->setEntryCount(Function::ProfileCount(FS->entryCount(),
diff --git a/llvm/lib/Transforms/Utils/LCSSA.cpp b/llvm/lib/Transforms/Utils/LCSSA.cpp
index 84d377d835f38..6de59f9eb5338 100644
--- a/llvm/lib/Transforms/Utils/LCSSA.cpp
+++ b/llvm/lib/Transforms/Utils/LCSSA.cpp
@@ -417,7 +417,7 @@ bool llvm::formLCSSARecursively(Loop &L, const DominatorTree &DT,
 static bool formLCSSAOnAllLoops(const LoopInfo *LI, const DominatorTree &DT,
                                 ScalarEvolution *SE) {
   bool Changed = false;
-  for (auto &L : *LI)
+  for (const auto &L : *LI)
     Changed |= formLCSSARecursively(*L, DT, LI, SE);
   return Changed;
 }
diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index c5f7a374c4ef6..25043b35b1bb2 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -1587,7 +1587,7 @@ bool llvm::LowerDbgDeclare(Function &F) {
     WorkList.push_back(AI);
     while (!WorkList.empty()) {
       const Value *V = WorkList.pop_back_val();
-      for (auto &AIUse : V->uses()) {
+      for (const auto &AIUse : V->uses()) {
         User *U = AIUse.getUser();
         if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
           if (AIUse.getOperandNo() == 1)
diff --git a/llvm/lib/Transforms/Utils/SampleProfileInference.cpp b/llvm/lib/Transforms/Utils/SampleProfileInference.cpp
index d9005be2c8f3a..5b4177bda9f93 100644
--- a/llvm/lib/Transforms/Utils/SampleProfileInference.cpp
+++ b/llvm/lib/Transforms/Utils/SampleProfileInference.cpp
@@ -148,7 +148,7 @@ class MinCostMaxFlow {
   /// Returns a list of pairs (target node, amount of flow to the target).
   const std::vector<std::pair<uint64_t, int64_t>> getFlow(uint64_t Src) const {
     std::vector<std::pair<uint64_t, int64_t>> Flow;
-    for (auto &Edge : Edges[Src]) {
+    for (const auto &Edge : Edges[Src]) {
       if (Edge.Flow > 0)
         Flow.push_back(std::make_pair(Edge.Dst, Edge.Flow));
     }
@@ -158,7 +158,7 @@ class MinCostMaxFlow {
   /// Get the total flow between a pair of nodes.
   int64_t getFlow(uint64_t Src, uint64_t Dst) const {
     int64_t Flow = 0;
-    for (auto &Edge : Edges[Src]) {
+    for (const auto &Edge : Edges[Src]) {
       if (Edge.Dst == Dst) {
         Flow += Edge.Flow;
       }
@@ -1137,7 +1137,7 @@ void extractWeights(MinCostMaxFlow &Network, FlowFunction &Func) {
     auto &Block = Func.Blocks[Src];
     uint64_t SrcOut = 3 * Src + 1;
     int64_t Flow = 0;
-    for (auto &Adj : Network.getFlow(SrcOut)) {
+    for (const auto &Adj : Network.getFlow(SrcOut)) {
       uint64_t DstIn = Adj.first;
       int64_t DstFlow = Adj.second;
       bool IsAuxNode = (DstIn < 3 * NumBlocks && DstIn % 3 == 2);
@@ -1176,7 +1176,7 @@ void verifyWeights(const FlowFunction &Func) {
   const uint64_t NumBlocks = Func.Blocks.size();
   auto InFlow = std::vector<uint64_t>(NumBlocks, 0);
   auto OutFlow = std::vector<uint64_t>(NumBlocks, 0);
-  for (auto &Jump : Func.Jumps) {
+  for (const auto &Jump : Func.Jumps) {
     InFlow[Jump.Target] += Jump.Flow;
     OutFlow[Jump.Source] += Jump.Flow;
   }
@@ -1202,7 +1202,7 @@ void verifyWeights(const FlowFunction &Func) {
   // One could modify FlowFunction to hold edges indexed by the sources, which
   // will avoid a creation of the object
   auto PositiveFlowEdges = std::vector<std::vector<uint64_t>>(NumBlocks);
-  for (auto &Jump : Func.Jumps) {
+  for (const auto &Jump : Func.Jumps) {
     if (Jump.Flow > 0) {
       PositiveFlowEdges[Jump.Source].push_back(Jump.Target);
     }
diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 164a9164ee11b..197b0d75d0912 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -5272,7 +5272,7 @@ static bool eliminateDeadSwitchCases(SwitchInst *SI, DomTreeUpdater *DTU,
   SmallVector<ConstantInt *, 8> DeadCases;
   SmallDenseMap<BasicBlock *, int, 8> NumPerSuccessorCases;
   SmallVector<BasicBlock *, 8> UniqueSuccessors;
-  for (auto &Case : SI->cases()) {
+  for (const auto &Case : SI->cases()) {
     auto *Successor = Case.getCaseSuccessor();
     if (DTU) {
       if (!NumPerSuccessorCases.count(Successor))
@@ -5372,7 +5372,7 @@ static bool ForwardSwitchConditionToPHI(SwitchInst *SI) {
   ForwardingNodesMap ForwardingNodes;
   BasicBlock *SwitchBlock = SI->getParent();
   bool Changed = false;
-  for (auto &Case : SI->cases()) {
+  for (const auto &Case : SI->cases()) {
     ConstantInt *CaseValue = Case.getCaseValue();
     BasicBlock *CaseDest = Case.getCaseSuccessor();
 
@@ -5588,7 +5588,7 @@ static bool initializeUniqueCases(SwitchInst *SI, PHINode *&PHI,
                                   const DataLayout &DL,
                                   const TargetTransformInfo &TTI,
                                   uintptr_t MaxUniqueResults) {
-  for (auto &I : SI->cases()) {
+  for (const auto &I : SI->cases()) {
     ConstantInt *CaseVal = I.getCaseValue();
 
     // Resulting value at phi nodes for this case value.
@@ -6494,7 +6494,7 @@ static bool ReduceSwitchRange(SwitchInst *SI, IRBuilder<> &Builder,
   // cases such as a sequence crossing zero {-4,0,4,8} if we interpret case values
   // as signed.
   SmallVector<int64_t,4> Values;
-  for (auto &C : SI->cases())
+  for (const auto &C : SI->cases())
     Values.push_back(C.getCaseValue()->getValue().getSExtValue());
   llvm::sort(Values);
 
@@ -7043,7 +7043,7 @@ static bool removeUndefIntroducingPredecessor(BasicBlock *BB,
           Builder.SetInsertPoint(Unreachable);
           // The new block contains only one instruction: Unreachable
           Builder.CreateUnreachable();
-          for (auto &Case : SI->cases())
+          for (const auto &Case : SI->cases())
             if (Case.getCaseSuccessor() == BB) {
               BB->removePredecessor(Predecessor);
               Case.setSuccessor(Unreachable);
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
index 183ba86abcb40..dff43efe494af 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
@@ -1364,7 +1364,7 @@ bool LoopVectorizationLegality::prepareToFoldTailByMasking() {
 
   SmallPtrSet<const Value *, 8> ReductionLiveOuts;
 
-  for (auto &Reduction : getReductionVars())
+  for (const auto &Reduction : getReductionVars())
     ReductionLiveOuts.insert(Reduction.second.getLoopExitInstr());
 
   // TODO: handle non-reduction outside users when tail is folded by masking.
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 91a452ef197c4..fd6b274811ffe 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -2755,7 +2755,7 @@ void InnerLoopVectorizer::scalarizeInstruction(Instruction *Instr,
 
   // Replace the operands of the cloned instructions with their scalar
   // equivalents in the new loop.
-  for (auto &I : enumerate(RepRecipe->operands())) {
+  for (const auto &I : enumerate(RepRecipe->operands())) {
     auto InputInstance = Instance;
     VPValue *Operand = I.value();
     VPReplicateRecipe *OperandR = dyn_cast<VPReplicateRecipe>(Operand);
@@ -3100,7 +3100,7 @@ void InnerLoopVectorizer::createInductionResumeValues(
   // If we come from a bypass edge then we need to start from the original
   // start value.
   Instruction *OldInduction = Legal->getPrimaryInduction();
-  for (auto &InductionEntry : Legal->getInductionVars()) {
+  for (const auto &InductionEntry : Legal->getInductionVars()) {
     PHINode *OrigPhi = InductionEntry.first;
     InductionDescriptor II = InductionEntry.second;
 
@@ -3655,7 +3655,7 @@ void InnerLoopVectorizer::fixVectorizedLoop(VPTransformState &State,
     // edge.
 
     // Fix-up external users of the induction variables.
-    for (auto &Entry : Legal->getInductionVars())
+    for (const auto &Entry : Legal->getInductionVars())
       fixupIVUsers(Entry.first, Entry.second,
                    getOrCreateVectorTripCount(VectorLoop->getLoopPreheader()),
                    IVEndValues[Entry.first], LoopMiddleBlock,
@@ -3665,7 +3665,7 @@ void InnerLoopVectorizer::fixVectorizedLoop(VPTransformState &State,
   // Fix LCSSA phis not already fixed earlier. Extracts may need to be generated
   // in the exit block, so update the builder.
   State.Builder.SetInsertPoint(State.CFG.ExitBB->getFirstNonPHI());
-  for (auto &KV : Plan.getLiveOuts())
+  for (const auto &KV : Plan.getLiveOuts())
     KV.second->fixPhi(Plan, State);
 
   for (Instruction *PI : PredicatedInstructions)
@@ -4182,7 +4182,7 @@ void InnerLoopVectorizer::widenCallInstruction(CallInst &CI, VPValue *Def,
   for (unsigned Part = 0; Part < UF; ++Part) {
     SmallVector<Type *, 2> TysForDecl = {CI.getType()};
     SmallVector<Value *, 4> Args;
-    for (auto &I : enumerate(ArgOperands.operands())) {
+    for (const auto &I : enumerate(ArgOperands.operands())) {
       // Some intrinsics have a scalar argument - don't replace it with a
       // vector.
       Value *Arg;
@@ -4359,7 +4359,7 @@ void LoopVectorizationCostModel::collectLoopScalars(ElementCount VF) {
 
   // An induction variable will remain scalar if all users of the induction
   // variable and induction variable update remain scalar.
-  for (auto &Induction : Legal->getInductionVars()) {
+  for (const auto &Induction : Legal->getInductionVars()) {
     auto *Ind = Induction.first;
     auto *IndUpdate = cast<Instruction>(Ind->getIncomingValueForBlock(Latch));
 
@@ -4749,7 +4749,7 @@ void LoopVectorizationCostModel::collectLoopUniforms(ElementCount VF) {
   // nodes separately. An induction variable will remain uniform if all users
   // of the induction variable and induction variable update remain uniform.
   // The code below handles both pointer and non-pointer induction variables.
-  for (auto &Induction : Legal->getInductionVars()) {
+  for (const auto &Induction : Legal->getInductionVars()) {
     auto *Ind = Induction.first;
     auto *IndUpdate = cast<Instruction>(Ind->getIncomingValueForBlock(Latch));
 
@@ -5381,7 +5381,7 @@ VectorizationFactor LoopVectorizationCostModel::selectVectorizationFactor(
         raw_string_ostream OS(OutString);
         assert(!Subset.empty() && "Unexpected empty range");
         OS << "Instruction with invalid costs prevented vectorization at VF=(";
-        for (auto &Pair : Subset)
+        for (const auto &Pair : Subset)
           OS << (Pair.second == Subset.front().second ? "" : ", ")
              << Pair.second;
         OS << "):";
@@ -5424,7 +5424,7 @@ bool LoopVectorizationCostModel::isCandidateForEpilogueVectorization(
 
   // Phis with uses outside of the loop require special handling and are
   // currently unsupported.
-  for (auto &Entry : Legal->getInductionVars()) {
+  for (const auto &Entry : Legal->getInductionVars()) {
     // Look for uses of the value of the induction at the last iteration.
     Value *PostInc = Entry.first->getIncomingValueForBlock(L.getLoopLatch());
     for (User *U : PostInc->users())
@@ -5558,7 +5558,7 @@ LoopVectorizationCostModel::getSmallestAndWidestTypes() {
     // Reset MaxWidth so that we can find the smallest type used by recurrences
     // in the loop.
     MaxWidth = -1U;
-    for (auto &PhiDescriptorPair : Legal->getReductionVars()) {
+    for (const auto &PhiDescriptorPair : Legal->getReductionVars()) {
       const RecurrenceDescriptor &RdxDesc = PhiDescriptorPair.second;
       // When finding the min width used by the recurrence we need to account
       // for casts on the input operands of the recurrence.
@@ -7342,14 +7342,14 @@ void LoopVectorizationCostModel::collectValuesToIgnore() {
 
   // Ignore type-promoting instructions we identified during reduction
   // detection.
-  for (auto &Reduction : Legal->getReductionVars()) {
+  for (const auto &Reduction : Legal->getReductionVars()) {
     const RecurrenceDescriptor &RedDes = Reduction.second;
     const SmallPtrSetImpl<Instruction *> &Casts = RedDes.getCastInsts();
     VecValuesToIgnore.insert(Casts.begin(), Casts.end());
   }
   // Ignore type-casting instructions we identified during induction
   // detection.
-  for (auto &Induction : Legal->getInductionVars()) {
+  for (const auto &Induction : Legal->getInductionVars()) {
     const InductionDescriptor &IndDes = Induction.second;
     const SmallVectorImpl<Instruction *> &Casts = IndDes.getCastInsts();
     VecValuesToIgnore.insert(Casts.begin(), Casts.end());
@@ -7357,7 +7357,7 @@ void LoopVectorizationCostModel::collectValuesToIgnore() {
 }
 
 void LoopVectorizationCostModel::collectInLoopReductions() {
-  for (auto &Reduction : Legal->getReductionVars()) {
+  for (const auto &Reduction : Legal->getReductionVars()) {
     PHINode *Phi = Reduction.first;
     const RecurrenceDescriptor &RdxDesc = Reduction.second;
 
@@ -8721,18 +8721,18 @@ VPlanPtr LoopVectorizationPlanner::buildVPlanWithVPRecipes(
 
   // Mark instructions we'll need to sink later and their targets as
   // ingredients whose recipe we'll need to record.
-  for (auto &Entry : SinkAfter) {
+  for (const auto &Entry : SinkAfter) {
     RecipeBuilder.recordRecipeOf(Entry.first);
     RecipeBuilder.recordRecipeOf(Entry.second);
   }
-  for (auto &Reduction : CM.getInLoopReductionChains()) {
+  for (const auto &Reduction : CM.getInLoopReductionChains()) {
     PHINode *Phi = Reduction.first;
     RecurKind Kind =
         Legal->getReductionVars().find(Phi)->second.getRecurrenceKind();
     const SmallVector<Instruction *, 4> &ReductionOperations = Reduction.second;
 
     RecipeBuilder.recordRecipeOf(Phi);
-    for (auto &R : ReductionOperations) {
+    for (const auto &R : ReductionOperations) {
       RecipeBuilder.recordRecipeOf(R);
       // For min/max reductions, where we have a pair of icmp/select, we also
       // need to record the ICmp recipe, so it can be removed later.
@@ -8913,7 +8913,7 @@ VPlanPtr LoopVectorizationPlanner::buildVPlanWithVPRecipes(
     }
     return nullptr;
   };
-  for (auto &Entry : SinkAfter) {
+  for (const auto &Entry : SinkAfter) {
     VPRecipeBase *Sink = RecipeBuilder.getRecipe(Entry.first);
     VPRecipeBase *Target = RecipeBuilder.getRecipe(Entry.second);
 
@@ -9112,7 +9112,7 @@ VPlanPtr LoopVectorizationPlanner::buildVPlan(VFRange &Range) {
 void LoopVectorizationPlanner::adjustRecipesForReductions(
     VPBasicBlock *LatchVPBB, VPlanPtr &Plan, VPRecipeBuilder &RecipeBuilder,
     ElementCount MinVF) {
-  for (auto &Reduction : CM.getInLoopReductionChains()) {
+  for (const auto &Reduction : CM.getInLoopReductionChains()) {
     PHINode *Phi = Reduction.first;
     const RecurrenceDescriptor &RdxDesc =
         Legal->getReductionVars().find(Phi)->second;
@@ -10496,7 +10496,7 @@ LoopVectorizeResult LoopVectorizePass::runImpl(
   // legality and profitability checks. This means running the loop vectorizer
   // will simplify all loops, regardless of whether anything end up being
   // vectorized.
-  for (auto &L : *LI)
+  for (const auto &L : *LI)
     Changed |= CFGChanged |=
         simplifyLoop(L, DT, LI, SE, AC, nullptr, false /* PreserveLCSSA */);
 
diff --git a/llvm/lib/Transforms/Vectorize/VPlan.cpp b/llvm/lib/Transforms/Vectorize/VPlan.cpp
index 30032dda7f60a..f78ccff7f9cd3 100644
--- a/llvm/lib/Transforms/Vectorize/VPlan.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlan.cpp
@@ -768,7 +768,7 @@ void VPlan::print(raw_ostream &O) const {
 
   if (!LiveOuts.empty())
     O << "\n";
-  for (auto &KV : LiveOuts) {
+  for (const auto &KV : LiveOuts) {
     O << "Live-out ";
     KV.second->getPhi()->printAsOperand(O);
     O << " = ";
diff --git a/llvm/lib/Transforms/Vectorize/VPlanVerifier.cpp b/llvm/lib/Transforms/Vectorize/VPlanVerifier.cpp
index 43e0a40fedb93..91ab693203103 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanVerifier.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlanVerifier.cpp
@@ -282,7 +282,7 @@ bool VPlanVerifier::verifyPlanIsValid(const VPlan &Plan) {
     }
   }
 
-  for (auto &KV : Plan.getLiveOuts())
+  for (const auto &KV : Plan.getLiveOuts())
     if (KV.second->getNumOperands() != 1) {
       errs() << "live outs must have a single operand\n";
       return false;