Revert "[IR] Use range-based for loops (NFC)"

This reverts commit e851278.

This revert is done because llvm::drop_begin over an empty ArrayRef
doesn't return an empty range, and therefore can lead to an invalid
address returned instead.

See discussion in #80737 for
more context.

Author: rastogishubham

llvm/lib/IR/AsmWriter.cpp

@@ -1309,8 +1309,8 @@ void SlotTracker::CreateMetadataSlot(const MDNode *N) {
   ++mdnNext;
 
   // Recursively add any MDNodes referenced by operands.
-  for (const MDOperand &MDO : N->operands())
-    if (const MDNode *Op = dyn_cast_or_null<MDNode>(MDO))
+  for (unsigned i = 0, e = N->getNumOperands(); i != e; ++i)
+    if (const MDNode *Op = dyn_cast_or_null<MDNode>(N->getOperand(i)))
       CreateMetadataSlot(Op);
 }
 

llvm/lib/IR/AutoUpgrade.cpp

@@ -5209,8 +5209,8 @@ static Metadata *upgradeLoopArgument(Metadata *MD) {
   SmallVector<Metadata *, 8> Ops;
   Ops.reserve(T->getNumOperands());
   Ops.push_back(upgradeLoopTag(T->getContext(), OldTag->getString()));
-  for (const MDOperand &MDO : llvm::drop_begin(T->operands()))
-    Ops.push_back(MDO);
+  for (unsigned I = 1, E = T->getNumOperands(); I != E; ++I)
+    Ops.push_back(T->getOperand(I));
 
   return MDTuple::get(T->getContext(), Ops);
 }

llvm/lib/IR/DebugInfo.cpp

@@ -400,8 +400,8 @@ static MDNode *updateLoopMetadataDebugLocationsImpl(
   // Save space for the self-referential LoopID.
   SmallVector<Metadata *, 4> MDs = {nullptr};
 
-  for (const MDOperand &MDO : llvm::drop_begin(OrigLoopID->operands())) {
-    Metadata *MD = MDO;
+  for (unsigned i = 1; i < OrigLoopID->getNumOperands(); ++i) {
+    Metadata *MD = OrigLoopID->getOperand(i);
     if (!MD)
       MDs.push_back(nullptr);
     else if (Metadata *NewMD = Updater(MD))

llvm/lib/IR/Function.cpp

@@ -1976,9 +1976,10 @@ DenseSet<GlobalValue::GUID> Function::getImportGUIDs() const {
   if (MDNode *MD = getMetadata(LLVMContext::MD_prof))
     if (MDString *MDS = dyn_cast<MDString>(MD->getOperand(0)))
       if (MDS->getString().equals("function_entry_count"))
-        for (const MDOperand &MDO : llvm::drop_begin(MD->operands(), 2))
-          R.insert(
-              mdconst::extract<ConstantInt>(MDO)->getValue().getZExtValue());
+        for (unsigned i = 2; i < MD->getNumOperands(); i++)
+          R.insert(mdconst::extract<ConstantInt>(MD->getOperand(i))
+                       ->getValue()
+                       .getZExtValue());
   return R;
 }
 

llvm/lib/IR/ProfDataUtils.cpp

@@ -162,8 +162,8 @@ bool extractProfTotalWeight(const MDNode *ProfileData, uint64_t &TotalVal) {
     return false;
 
   if (ProfDataName->getString().equals("branch_weights")) {
-    for (const MDOperand &MDO : llvm::drop_begin(ProfileData->operands())) {
-      auto *V = mdconst::dyn_extract<ConstantInt>(MDO);
+    for (unsigned Idx = 1; Idx < ProfileData->getNumOperands(); Idx++) {
+      auto *V = mdconst::dyn_extract<ConstantInt>(ProfileData->getOperand(Idx));
       assert(V && "Malformed branch_weight in MD_prof node");
       TotalVal += V->getValue().getZExtValue();
     }

llvm/lib/IR/Verifier.cpp

@@ -2913,8 +2913,8 @@ void Verifier::visitFunction(const Function &F) {
       VisitDebugLoc(I, I.getDebugLoc().getAsMDNode());
       // The llvm.loop annotations also contain two DILocations.
       if (auto MD = I.getMetadata(LLVMContext::MD_loop))
-        for (const MDOperand &MDO : llvm::drop_begin(MD->operands()))
-          VisitDebugLoc(I, dyn_cast_or_null<MDNode>(MDO));
+        for (unsigned i = 1; i < MD->getNumOperands(); ++i)
+          VisitDebugLoc(I, dyn_cast_or_null<MDNode>(MD->getOperand(i)));
       if (BrokenDebugInfo)
         return;
     }
@@ -4713,7 +4713,8 @@ void Verifier::visitProfMetadata(Instruction &I, MDNode *MD) {
       Check(MD->getNumOperands() == 1 + ExpectedNumOperands,
             "Wrong number of operands", MD);
     }
-    for (const MDOperand &MDO : llvm::drop_begin(MD->operands())) {
+    for (unsigned i = 1; i < MD->getNumOperands(); ++i) {
+      auto &MDO = MD->getOperand(i);
       Check(MDO, "second operand should not be null", MD);
       Check(mdconst::dyn_extract<ConstantInt>(MDO),
             "!prof brunch_weights operand is not a const int");