diff --git a/llvm/lib/Transforms/IPO/GlobalOpt.cpp b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
index 4a06e0fa619c..7f5a2a982982 100644
--- a/llvm/lib/Transforms/IPO/GlobalOpt.cpp
+++ b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
@@ -250,10 +250,10 @@ CleanupPointerRootUsers(GlobalVariable *GV,
     }
   }
 
-  for (int i = 0, e = Dead.size(); i != e; ++i) {
-    if (IsSafeComputationToRemove(Dead[i].first, GetTLI)) {
-      Dead[i].second->eraseFromParent();
-      Instruction *I = Dead[i].first;
+  for (const auto &[Inst, Store] : Dead) {
+    if (IsSafeComputationToRemove(Inst, GetTLI)) {
+      Store->eraseFromParent();
+      Instruction *I = Inst;
       do {
         if (isAllocationFn(I, GetTLI))
           break;
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index 99acb02561d5..40578e5edc3a 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -3494,13 +3494,13 @@ Instruction *InstCombinerImpl::visitAllocSite(Instruction &MI) {
   auto Removable =
       isAllocSiteRemovable(&MI, Users, TLI, KnowInitZero | KnowInitUndef);
   if (Removable) {
-    for (unsigned i = 0, e = Users.size(); i != e; ++i) {
+    for (WeakTrackingVH &User : Users) {
       // Lowering all @llvm.objectsize and MTI calls first because they may use
       // a bitcast/GEP of the alloca we are removing.
-      if (!Users[i])
-       continue;
+      if (!User)
+        continue;
 
-      Instruction *I = cast<Instruction>(&*Users[i]);
+      Instruction *I = cast<Instruction>(&*User);
 
       if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
         if (II->getIntrinsicID() == Intrinsic::objectsize) {
@@ -3511,7 +3511,7 @@ Instruction *InstCombinerImpl::visitAllocSite(Instruction &MI) {
             Worklist.add(Inserted);
           replaceInstUsesWith(*I, Result);
           eraseInstFromFunction(*I);
-          Users[i] = nullptr; // Skip examining in the next loop.
+          User = nullptr; // Skip examining in the next loop.
           continue;
         }
         if (auto *MTI = dyn_cast<MemTransferInst>(I)) {
@@ -3527,11 +3527,11 @@ Instruction *InstCombinerImpl::visitAllocSite(Instruction &MI) {
         }
       }
     }
-    for (unsigned i = 0, e = Users.size(); i != e; ++i) {
-      if (!Users[i])
+    for (WeakTrackingVH &User : Users) {
+      if (!User)
         continue;
 
-      Instruction *I = cast<Instruction>(&*Users[i]);
+      Instruction *I = cast<Instruction>(&*User);
 
       if (ICmpInst *C = dyn_cast<ICmpInst>(I)) {
         replaceInstUsesWith(*C,
diff --git a/llvm/lib/Transforms/Scalar/LoopInterchange.cpp b/llvm/lib/Transforms/Scalar/LoopInterchange.cpp
index 1e16677e5a56..9e3b4b82cc45 100644
--- a/llvm/lib/Transforms/Scalar/LoopInterchange.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopInterchange.cpp
@@ -235,8 +235,8 @@ static bool populateDependencyMatrix(CharMatrix &DepMatrix, unsigned Level,
 // matrix by exchanging the two columns.
 static void interChangeDependencies(CharMatrix &DepMatrix, unsigned FromIndx,
                                     unsigned ToIndx) {
-  for (unsigned I = 0, E = DepMatrix.size(); I < E; ++I)
-    std::swap(DepMatrix[I][ToIndx], DepMatrix[I][FromIndx]);
+  for (auto &Row : DepMatrix)
+    std::swap(Row[ToIndx], Row[FromIndx]);
 }
 
 // Check if a direction vector is lexicographically positive. Return true if it
diff --git a/llvm/lib/Transforms/Scalar/Reassociate.cpp b/llvm/lib/Transforms/Scalar/Reassociate.cpp
index 778a6a012556..343da5b2e470 100644
--- a/llvm/lib/Transforms/Scalar/Reassociate.cpp
+++ b/llvm/lib/Transforms/Scalar/Reassociate.cpp
@@ -83,10 +83,10 @@ static void PrintOps(Instruction *I, const SmallVectorImpl<ValueEntry> &Ops) {
   Module *M = I->getModule();
   dbgs() << Instruction::getOpcodeName(I->getOpcode()) << " "
        << *Ops[0].Op->getType() << '\t';
-  for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
+  for (const ValueEntry &Op : Ops) {
     dbgs() << "[ ";
-    Ops[i].Op->printAsOperand(dbgs(), false, M);
-    dbgs() << ", #" << Ops[i].Rank << "] ";
+    Op.Op->printAsOperand(dbgs(), false, M);
+    dbgs() << ", #" << Op.Rank << "] ";
   }
 }
 #endif
@@ -1585,9 +1585,9 @@ Value *ReassociatePass::OptimizeAdd(Instruction *I,
   // where they are actually the same multiply.
   unsigned MaxOcc = 0;
   Value *MaxOccVal = nullptr;
-  for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
+  for (const ValueEntry &Op : Ops) {
     BinaryOperator *BOp =
-        isReassociableOp(Ops[i].Op, Instruction::Mul, Instruction::FMul);
+        isReassociableOp(Op.Op, Instruction::Mul, Instruction::FMul);
     if (!BOp)
       continue;
 
diff --git a/llvm/lib/Transforms/Vectorize/VectorCombine.cpp b/llvm/lib/Transforms/Vectorize/VectorCombine.cpp
index 3e459f5ea4ce..a4bfdcabaa31 100644
--- a/llvm/lib/Transforms/Vectorize/VectorCombine.cpp
+++ b/llvm/lib/Transforms/Vectorize/VectorCombine.cpp
@@ -3082,10 +3082,10 @@ bool VectorCombine::foldSelectShuffle(Instruction &I, bool FromReduction) {
       auto *SSV = cast<ShuffleVectorInst>(SVOp0);
       SVOp0 = SSV->getOperand(0);
       SVOp1 = SSV->getOperand(1);
-      for (unsigned I = 0, E = Mask.size(); I != E; I++) {
-        if (Mask[I] >= static_cast<int>(SSV->getShuffleMask().size()))
+      for (int &Elem : Mask) {
+        if (Elem >= static_cast<int>(SSV->getShuffleMask().size()))
           return false;
-        Mask[I] = Mask[I] < 0 ? Mask[I] : SSV->getMaskValue(Mask[I]);
+        Elem = Elem < 0 ? Elem : SSV->getMaskValue(Elem);
       }
     }
     if (SVOp0 == Op1 && SVOp1 == Op0) {