[llvm] Use range-based for loops with llvm::drop_begin (NFC) (llvm#136417)

Author: kazutakahirata

llvm/lib/Bitcode/Reader/BitcodeReader.cpp

@@ -8079,9 +8079,9 @@ Error ModuleSummaryIndexBitcodeReader::parseEntireSummary(unsigned ID) {
     case bitc::FS_PERMODULE_CALLSITE_INFO: {
       unsigned ValueID = Record[0];
       SmallVector<unsigned> StackIdList;
-      for (auto R = Record.begin() + 1; R != Record.end(); R++) {
-        assert(*R < StackIds.size());
-        StackIdList.push_back(TheIndex.addOrGetStackIdIndex(StackIds[*R]));
+      for (uint64_t R : drop_begin(Record)) {
+        assert(R < StackIds.size());
+        StackIdList.push_back(TheIndex.addOrGetStackIdIndex(StackIds[R]));
       }
       ValueInfo VI = std::get<0>(getValueInfoFromValueId(ValueID));
       PendingCallsites.push_back(CallsiteInfo({VI, std::move(StackIdList)}));

llvm/lib/IR/DebugInfo.cpp

@@ -976,9 +976,9 @@ void Instruction::mergeDIAssignID(
     return; // No DIAssignID tags to process.
 
   DIAssignID *MergeID = IDs[0];
-  for (auto It = std::next(IDs.begin()), End = IDs.end(); It != End; ++It) {
-    if (*It != MergeID)
-      at::RAUW(*It, MergeID);
+  for (DIAssignID *AssignID : drop_begin(IDs)) {
+    if (AssignID != MergeID)
+      at::RAUW(AssignID, MergeID);
   }
   setMetadata(LLVMContext::MD_DIAssignID, MergeID);
 }

llvm/lib/Target/BPF/BPFPreserveStaticOffset.cpp

@@ -345,8 +345,7 @@ static bool foldGEPChainAsStructAccess(SmallVector<GetElementPtrInst *> &GEPs,
   Info.Indices.append(First->idx_begin(), First->idx_end());
   Info.Members.push_back(First);
 
-  for (auto *Iter = GEPs.begin() + 1; Iter != GEPs.end(); ++Iter) {
-    GetElementPtrInst *GEP = *Iter;
+  for (GetElementPtrInst *GEP : drop_begin(GEPs)) {
     if (!isZero(*GEP->idx_begin())) {
       Info.reset();
       return false;

llvm/lib/Target/SPIRV/SPIRVStructurizer.cpp

@@ -509,9 +509,8 @@ class SPIRVStructurizer : public FunctionPass {
       }
 
       SwitchInst *Sw = ExitBuilder.CreateSwitch(Load, Dsts[0], Dsts.size() - 1);
-      for (auto It = Dsts.begin() + 1; It != Dsts.end(); ++It) {
-        Sw->addCase(DstToIndex[*It], *It);
-      }
+      for (BasicBlock *BB : drop_begin(Dsts))
+        Sw->addCase(DstToIndex[BB], BB);
       return NewExit;
     }
   };

llvm/lib/Transforms/Vectorize/SandboxVectorizer/SeedCollector.cpp

@@ -46,7 +46,7 @@ ArrayRef<Instruction *> SeedBundle::getSlice(unsigned StartIdx,
   uint32_t BitCountPowerOfTwo = 0;
   // Can't start a slice with a used instruction.
   assert(!isUsed(StartIdx) && "Expected unused at StartIdx");
-  for (auto S : make_range(Seeds.begin() + StartIdx, Seeds.end())) {
+  for (Instruction *S : drop_begin(Seeds, StartIdx)) {
     // Stop if this instruction is used. This needs to be done before
     // getNumBits() because a "used" instruction may have been erased.
     if (isUsed(StartIdx + NumElements))