diff --git a/lib/IR/AsmWriter.cpp b/lib/IR/AsmWriter.cpp
index bb300a230b9..642ecc92e9b 100644
--- a/lib/IR/AsmWriter.cpp
+++ b/lib/IR/AsmWriter.cpp
@@ -2332,17 +2332,17 @@ static void writeDIExpression(raw_ostream &Out, const DIExpression *N,
   Out << "!DIExpression(";
   FieldSeparator FS;
   if (N->isValid()) {
-    for (auto I = N->expr_op_begin(), E = N->expr_op_end(); I != E; ++I) {
-      auto OpStr = dwarf::OperationEncodingString(I->getOp());
+    for (const DIExpression::ExprOperand &Op : N->expr_ops()) {
+      auto OpStr = dwarf::OperationEncodingString(Op.getOp());
       assert(!OpStr.empty() && "Expected valid opcode");
 
       Out << FS << OpStr;
-      if (I->getOp() == dwarf::DW_OP_LLVM_convert) {
-        Out << FS << I->getArg(0);
-        Out << FS << dwarf::AttributeEncodingString(I->getArg(1));
+      if (Op.getOp() == dwarf::DW_OP_LLVM_convert) {
+        Out << FS << Op.getArg(0);
+        Out << FS << dwarf::AttributeEncodingString(Op.getArg(1));
       } else {
-        for (unsigned A = 0, AE = I->getNumArgs(); A != AE; ++A)
-          Out << FS << I->getArg(A);
+        for (unsigned A = 0, AE = Op.getNumArgs(); A != AE; ++A)
+          Out << FS << Op.getArg(A);
       }
     }
   } else {
@@ -2914,12 +2914,11 @@ void AssemblyWriter::printModuleSummaryIndex() {
   }
 
   // Print the TypeIdMap entries.
-  for (auto TidIter = TheIndex->typeIds().begin();
-       TidIter != TheIndex->typeIds().end(); TidIter++) {
-    Out << "^" << Machine.getTypeIdSlot(TidIter->second.first)
-        << " = typeid: (name: \"" << TidIter->second.first << "\"";
-    printTypeIdSummary(TidIter->second.second);
-    Out << ") ; guid = " << TidIter->first << "\n";
+  for (const auto &TID : TheIndex->typeIds()) {
+    Out << "^" << Machine.getTypeIdSlot(TID.second.first)
+        << " = typeid: (name: \"" << TID.second.first << "\"";
+    printTypeIdSummary(TID.second.second);
+    Out << ") ; guid = " << TID.first << "\n";
   }
 
   // Print the TypeIdCompatibleVtableMap entries.
@@ -4023,8 +4022,8 @@ void AssemblyWriter::printInstruction(const Instruction &I) {
   } else if (const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(&I)) {
     Out << ' ';
     writeOperand(I.getOperand(0), true);
-    for (const unsigned *i = EVI->idx_begin(), *e = EVI->idx_end(); i != e; ++i)
-      Out << ", " << *i;
+    for (unsigned i : EVI->indices())
+      Out << ", " << i;
   } else if (const InsertValueInst *IVI = dyn_cast<InsertValueInst>(&I)) {
     Out << ' ';
     writeOperand(I.getOperand(0), true); Out << ", ";
diff --git a/lib/IR/Attributes.cpp b/lib/IR/Attributes.cpp
index c4629decc6d..c98e5c36a51 100644
--- a/lib/IR/Attributes.cpp
+++ b/lib/IR/Attributes.cpp
@@ -1869,9 +1869,8 @@ bool AttrBuilder::operator==(const AttrBuilder &B) const {
   if (Attrs != B.Attrs)
     return false;
 
-  for (td_const_iterator I = TargetDepAttrs.begin(),
-         E = TargetDepAttrs.end(); I != E; ++I)
-    if (B.TargetDepAttrs.find(I->first) == B.TargetDepAttrs.end())
+  for (const auto &TDA : TargetDepAttrs)
+    if (B.TargetDepAttrs.find(TDA.first) == B.TargetDepAttrs.end())
       return false;
 
   return Alignment == B.Alignment && StackAlignment == B.StackAlignment &&
diff --git a/lib/IR/BasicBlock.cpp b/lib/IR/BasicBlock.cpp
index 00ef10dd53a..48227d8e6c6 100644
--- a/lib/IR/BasicBlock.cpp
+++ b/lib/IR/BasicBlock.cpp
@@ -455,9 +455,8 @@ void BasicBlock::replaceSuccessorsPhiUsesWith(BasicBlock *Old,
     // Cope with being called on a BasicBlock that doesn't have a terminator
     // yet. Clang's CodeGenFunction::EmitReturnBlock() likes to do this.
     return;
-  llvm::for_each(successors(TI), [Old, New](BasicBlock *Succ) {
+  for (BasicBlock *Succ : successors(TI))
     Succ->replacePhiUsesWith(Old, New);
-  });
 }
 
 void BasicBlock::replaceSuccessorsPhiUsesWith(BasicBlock *New) {
diff --git a/lib/IR/Core.cpp b/lib/IR/Core.cpp
index fdcd64370c0..6631a4ac224 100644
--- a/lib/IR/Core.cpp
+++ b/lib/IR/Core.cpp
@@ -679,9 +679,8 @@ unsigned LLVMCountParamTypes(LLVMTypeRef FunctionTy) {
 
 void LLVMGetParamTypes(LLVMTypeRef FunctionTy, LLVMTypeRef *Dest) {
   FunctionType *Ty = unwrap<FunctionType>(FunctionTy);
-  for (FunctionType::param_iterator I = Ty->param_begin(),
-                                    E = Ty->param_end(); I != E; ++I)
-    *Dest++ = wrap(*I);
+  for (Type *T : Ty->params())
+    *Dest++ = wrap(T);
 }
 
 /*--.. Operations on struct types ..........................................--*/
@@ -723,9 +722,8 @@ unsigned LLVMCountStructElementTypes(LLVMTypeRef StructTy) {
 
 void LLVMGetStructElementTypes(LLVMTypeRef StructTy, LLVMTypeRef *Dest) {
   StructType *Ty = unwrap<StructType>(StructTy);
-  for (StructType::element_iterator I = Ty->element_begin(),
-                                    E = Ty->element_end(); I != E; ++I)
-    *Dest++ = wrap(*I);
+  for (Type *T : Ty->elements())
+    *Dest++ = wrap(T);
 }
 
 LLVMTypeRef LLVMStructGetTypeAtIndex(LLVMTypeRef StructTy, unsigned i) {
@@ -2495,9 +2493,8 @@ unsigned LLVMCountParams(LLVMValueRef FnRef) {
 
 void LLVMGetParams(LLVMValueRef FnRef, LLVMValueRef *ParamRefs) {
   Function *Fn = unwrap<Function>(FnRef);
-  for (Function::arg_iterator I = Fn->arg_begin(),
-                              E = Fn->arg_end(); I != E; I++)
-    *ParamRefs++ = wrap(&*I);
+  for (Argument &A : Fn->args())
+    *ParamRefs++ = wrap(&A);
 }
 
 LLVMValueRef LLVMGetParam(LLVMValueRef FnRef, unsigned index) {
diff --git a/lib/IR/DebugInfoMetadata.cpp b/lib/IR/DebugInfoMetadata.cpp
index 55eff38d3fa..973020c02ff 100644
--- a/lib/IR/DebugInfoMetadata.cpp
+++ b/lib/IR/DebugInfoMetadata.cpp
@@ -82,8 +82,8 @@ DILocation *DILocation::getMergedLocations(ArrayRef<const DILocation *> Locs) {
   if (Locs.size() == 1)
     return Locs[0];
   auto *Merged = Locs[0];
-  for (auto I = std::next(Locs.begin()), E = Locs.end(); I != E; ++I) {
-    Merged = getMergedLocation(Merged, *I);
+  for (const DILocation *L : llvm::drop_begin(Locs)) {
+    Merged = getMergedLocation(Merged, L);
     if (Merged == nullptr)
       break;
   }
diff --git a/lib/IR/Dominators.cpp b/lib/IR/Dominators.cpp
index fbc28c202ae..5d17d6ced3c 100644
--- a/lib/IR/Dominators.cpp
+++ b/lib/IR/Dominators.cpp
@@ -222,9 +222,7 @@ bool DominatorTree::dominates(const BasicBlockEdge &BBE,
   // other predecessors. Since the only way out of X is via NormalDest, X can
   // only properly dominate a node if NormalDest dominates that node too.
   int IsDuplicateEdge = 0;
-  for (const_pred_iterator PI = pred_begin(End), E = pred_end(End);
-       PI != E; ++PI) {
-    const BasicBlock *BB = *PI;
+  for (const BasicBlock *BB : predecessors(End)) {
     if (BB == Start) {
       // If there are multiple edges between Start and End, by definition they
       // can't dominate anything.
diff --git a/lib/IR/Instructions.cpp b/lib/IR/Instructions.cpp
index b73528d8975..2fb277bd12d 100644
--- a/lib/IR/Instructions.cpp
+++ b/lib/IR/Instructions.cpp
@@ -2105,13 +2105,13 @@ static bool isSingleSourceMaskImpl(ArrayRef<int> Mask, int NumOpElts) {
   assert(!Mask.empty() && "Shuffle mask must contain elements");
   bool UsesLHS = false;
   bool UsesRHS = false;
-  for (int i = 0, NumMaskElts = Mask.size(); i < NumMaskElts; ++i) {
-    if (Mask[i] == -1)
+  for (int I : Mask) {
+    if (I == -1)
       continue;
-    assert(Mask[i] >= 0 && Mask[i] < (NumOpElts * 2) &&
+    assert(I >= 0 && I < (NumOpElts * 2) &&
            "Out-of-bounds shuffle mask element");
-    UsesLHS |= (Mask[i] < NumOpElts);
-    UsesRHS |= (Mask[i] >= NumOpElts);
+    UsesLHS |= (I < NumOpElts);
+    UsesRHS |= (I >= NumOpElts);
     if (UsesLHS && UsesRHS)
       return false;
   }
diff --git a/lib/IR/LegacyPassManager.cpp b/lib/IR/LegacyPassManager.cpp
index 19b03dfc35c..94be208617c 100644
--- a/lib/IR/LegacyPassManager.cpp
+++ b/lib/IR/LegacyPassManager.cpp
@@ -948,14 +948,13 @@ void PMDataManager::removeNotPreservedAnalysis(Pass *P) {
 
   // Check inherited analysis also. If P is not preserving analysis
   // provided by parent manager then remove it here.
-  for (unsigned Index = 0; Index < PMT_Last; ++Index) {
-
-    if (!InheritedAnalysis[Index])
+  for (DenseMap<AnalysisID, Pass *> *IA : InheritedAnalysis) {
+    if (!IA)
       continue;
 
-    for (DenseMap<AnalysisID, Pass*>::iterator
-           I = InheritedAnalysis[Index]->begin(),
-           E = InheritedAnalysis[Index]->end(); I != E; ) {
+    for (DenseMap<AnalysisID, Pass *>::iterator I = IA->begin(),
+                                                E = IA->end();
+         I != E;) {
       DenseMap<AnalysisID, Pass *>::iterator Info = I++;
       if (Info->second->getAsImmutablePass() == nullptr &&
           !is_contained(PreservedSet, Info->first)) {
@@ -965,7 +964,7 @@ void PMDataManager::removeNotPreservedAnalysis(Pass *P) {
           dbgs() << " -- '" <<  P->getPassName() << "' is not preserving '";
           dbgs() << S->getPassName() << "'\n";
         }
-        InheritedAnalysis[Index]->erase(Info);
+        IA->erase(Info);
       }
     }
   }
diff --git a/lib/IR/Mangler.cpp b/lib/IR/Mangler.cpp
index 674ba3cdaa2..bbdde586e6e 100644
--- a/lib/IR/Mangler.cpp
+++ b/lib/IR/Mangler.cpp
@@ -98,12 +98,11 @@ static void addByteCountSuffix(raw_ostream &OS, const Function *F,
 
   const unsigned PtrSize = DL.getPointerSize();
 
-  for (Function::const_arg_iterator AI = F->arg_begin(), AE = F->arg_end();
-       AI != AE; ++AI) {
+  for (const Argument &A : F->args()) {
     // 'Dereference' type in case of byval or inalloca parameter attribute.
-    uint64_t AllocSize = AI->hasPassPointeeByValueCopyAttr() ?
-      AI->getPassPointeeByValueCopySize(DL) :
-      DL.getTypeAllocSize(AI->getType());
+    uint64_t AllocSize = A.hasPassPointeeByValueCopyAttr() ?
+      A.getPassPointeeByValueCopySize(DL) :
+      DL.getTypeAllocSize(A.getType());
 
     // Size should be aligned to pointer size.
     ArgWords += alignTo(AllocSize, PtrSize);