[Transforms] Use range-based for loops (NFC)

llvm/lib/Transforms/IPO/ConstantMerge.cpp

@@ -226,9 +226,7 @@ static bool mergeConstants(Module &M) {
     // Now that we have figured out which replacements must be made, do them all
     // now.  This avoid invalidating the pointers in CMap, which are unneeded
     // now.
-    for (unsigned i = 0, e = SameContentReplacements.size(); i != e; ++i) {
-      GlobalVariable *Old = SameContentReplacements[i].first;
-      GlobalVariable *New = SameContentReplacements[i].second;
+    for (const auto &[Old, New] : SameContentReplacements) {
       replace(M, Old, New);
       ++ChangesMade;
       ++NumIdenticalMerged;

llvm/lib/Transforms/Scalar/GVN.cpp

@@ -3036,12 +3036,12 @@ bool GVNPass::performScalarPRE(Instruction *CurInst) {
   PHINode *Phi = PHINode::Create(CurInst->getType(), PredMap.size(),
                                  CurInst->getName() + ".pre-phi");
   Phi->insertBefore(CurrentBlock->begin());
-  for (unsigned I = 0, E = PredMap.size(); I != E; ++I) {
-    if (Value *V = PredMap[I].first) {
+  for (auto &[V, BB] : PredMap) {
+    if (V) {
       // If we use an existing value in this phi, we have to patch the original
       // value because the phi will be used to replace a later value.
       patchReplacementInstruction(CurInst, V);
-      Phi->addIncoming(V, PredMap[I].second);
+      Phi->addIncoming(V, BB);
     } else
       Phi->addIncoming(PREInstr, PREPred);
   }

llvm/lib/Transforms/Scalar/Reassociate.cpp

@@ -1115,10 +1115,8 @@ Value *ReassociatePass::RemoveFactorFromExpression(Value *V, Value *Factor,
   MadeChange |= LinearizeExprTree(BO, Tree, RedoInsts, Flags);
   SmallVector<ValueEntry, 8> Factors;
   Factors.reserve(Tree.size());
-  for (unsigned i = 0, e = Tree.size(); i != e; ++i) {
-    RepeatedValue E = Tree[i];
+  for (const RepeatedValue &E : Tree)
     Factors.append(E.second, ValueEntry(getRank(E.first), E.first));
-  }
 
   bool FoundFactor = false;
   bool NeedsNegate = false;
@@ -1391,8 +1389,8 @@ Value *ReassociatePass::OptimizeXor(Instruction *I,
   APInt ConstOpnd(Ty->getScalarSizeInBits(), 0);
 
   // Step 1: Convert ValueEntry to XorOpnd
-  for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
-    Value *V = Ops[i].Op;
+  for (const ValueEntry &Op : Ops) {
+    Value *V = Op.Op;
     const APInt *C;
     // TODO: Support non-splat vectors.
     if (match(V, m_APInt(C))) {

llvm/lib/Transforms/Utils/SimplifyCFG.cpp

@@ -976,8 +976,8 @@ bool SimplifyCFGOpt::simplifyEqualityComparisonWithOnlyPredecessor(
     SwitchInstProfUpdateWrapper SI = *cast<SwitchInst>(TI);
     // Okay, TI has cases that are statically dead, prune them away.
     SmallPtrSet<Constant *, 16> DeadCases;
-    for (unsigned i = 0, e = PredCases.size(); i != e; ++i)
-      DeadCases.insert(PredCases[i].Value);
+    for (const ValueEqualityComparisonCase &Case : PredCases)
+      DeadCases.insert(Case.Value);
 
     LLVM_DEBUG(dbgs() << "Threading pred instr: " << *Pred->getTerminator()
                       << "Through successor TI: " << *TI);
@@ -1307,14 +1307,14 @@ bool SimplifyCFGOpt::performValueComparisonIntoPredecessorFolding(
 
     // Okay, now we know which constants were sent to BB from the
     // predecessor.  Figure out where they will all go now.
-    for (unsigned i = 0, e = BBCases.size(); i != e; ++i)
-      if (PTIHandled.count(BBCases[i].Value)) {
+    for (const ValueEqualityComparisonCase &Case : BBCases)
+      if (PTIHandled.count(Case.Value)) {
         // If this is one we are capable of getting...
         if (PredHasWeights || SuccHasWeights)
-          Weights.push_back(WeightsForHandled[BBCases[i].Value]);
-        PredCases.push_back(BBCases[i]);
-        ++NewSuccessors[BBCases[i].Dest];
-        PTIHandled.erase(BBCases[i].Value); // This constant is taken care of
+          Weights.push_back(WeightsForHandled[Case.Value]);
+        PredCases.push_back(Case);
+        ++NewSuccessors[Case.Dest];
+        PTIHandled.erase(Case.Value); // This constant is taken care of
       }
 
     // If there are any constants vectored to BB that TI doesn't handle,
@@ -5177,8 +5177,8 @@ bool SimplifyCFGOpt::simplifyBranchOnICmpChain(BranchInst *BI,
   SwitchInst *New = Builder.CreateSwitch(CompVal, DefaultBB, Values.size());
 
   // Add all of the 'cases' to the switch instruction.
-  for (unsigned i = 0, e = Values.size(); i != e; ++i)
-    New->addCase(Values[i], EdgeBB);
+  for (ConstantInt *Val : Values)
+    New->addCase(Val, EdgeBB);
 
   // We added edges from PI to the EdgeBB.  As such, if there were any
   // PHI nodes in EdgeBB, they need entries to be added corresponding to
@@ -6453,9 +6453,7 @@ SwitchLookupTable::SwitchLookupTable(
 
   // Build up the table contents.
   SmallVector<Constant *, 64> TableContents(TableSize);
-  for (size_t I = 0, E = Values.size(); I != E; ++I) {
-    ConstantInt *CaseVal = Values[I].first;
-    Constant *CaseRes = Values[I].second;
+  for (const auto &[CaseVal, CaseRes] : Values) {
     assert(CaseRes->getType() == ValueType);
 
     uint64_t Idx = (CaseVal->getValue() - Offset->getValue()).getLimitedValue();