[llvm] Use drop_begin (NFC)

Author: kazutakahirata

llvm/lib/CodeGen/BranchFolding.cpp

@@ -1198,14 +1198,13 @@ bool BranchFolder::OptimizeBranches(MachineFunction &MF) {
   // Renumbering blocks alters EH scope membership, recalculate it.
   EHScopeMembership = getEHScopeMembership(MF);
 
-  for (MachineFunction::iterator I = std::next(MF.begin()), E = MF.end();
-       I != E; ) {
-    MachineBasicBlock *MBB = &*I++;
-    MadeChange |= OptimizeBlock(MBB);
+  for (MachineBasicBlock &MBB :
+       llvm::make_early_inc_range(llvm::drop_begin(MF))) {
+    MadeChange |= OptimizeBlock(&MBB);
 
     // If it is dead, remove it.
-    if (MBB->pred_empty()) {
-      RemoveDeadBlock(MBB);
+    if (MBB.pred_empty()) {
+      RemoveDeadBlock(&MBB);
       MadeChange = true;
       ++NumDeadBlocks;
     }

llvm/lib/CodeGen/TailDuplicator.cpp

@@ -279,18 +279,17 @@ bool TailDuplicator::tailDuplicateBlocks() {
     VerifyPHIs(*MF, true);
   }
 
-  for (MachineFunction::iterator I = ++MF->begin(), E = MF->end(); I != E;) {
-    MachineBasicBlock *MBB = &*I++;
-
+  for (MachineBasicBlock &MBB :
+       llvm::make_early_inc_range(llvm::drop_begin(*MF))) {
     if (NumTails == TailDupLimit)
       break;
 
-    bool IsSimple = isSimpleBB(MBB);
+    bool IsSimple = isSimpleBB(&MBB);
 
-    if (!shouldTailDuplicate(IsSimple, *MBB))
+    if (!shouldTailDuplicate(IsSimple, MBB))
       continue;
 
-    MadeChange |= tailDuplicateAndUpdate(IsSimple, MBB, nullptr);
+    MadeChange |= tailDuplicateAndUpdate(IsSimple, &MBB, nullptr);
   }
 
   if (PreRegAlloc && TailDupVerify)

llvm/lib/Target/AVR/AVRFrameLowering.cpp

@@ -111,9 +111,8 @@ void AVRFrameLowering::emitPrologue(MachineFunction &MF,
       .setMIFlag(MachineInstr::FrameSetup);
 
   // Mark the FramePtr as live-in in every block except the entry.
-  for (MachineFunction::iterator I = std::next(MF.begin()), E = MF.end();
-       I != E; ++I) {
-    I->addLiveIn(AVR::R29R28);
+  for (MachineBasicBlock &MBBJ : llvm::drop_begin(MF)) {
+    MBBJ.addLiveIn(AVR::R29R28);
   }
 
   if (!FrameSize) {

llvm/lib/Target/MSP430/MSP430FrameLowering.cpp

@@ -71,9 +71,8 @@ void MSP430FrameLowering::emitPrologue(MachineFunction &MF,
       .addReg(MSP430::SP);
 
     // Mark the FramePtr as live-in in every block except the entry.
-    for (MachineFunction::iterator I = std::next(MF.begin()), E = MF.end();
-         I != E; ++I)
-      I->addLiveIn(MSP430::R4);
+    for (MachineBasicBlock &MBBJ : llvm::drop_begin(MF))
+      MBBJ.addLiveIn(MSP430::R4);
 
   } else
     NumBytes = StackSize - MSP430FI->getCalleeSavedFrameSize();

llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp

@@ -566,8 +566,8 @@ void SystemZELFFrameLowering::emitPrologue(MachineFunction &MF,
     // Mark the FramePtr as live at the beginning of every block except
     // the entry block.  (We'll have marked R11 as live on entry when
     // saving the GPRs.)
-    for (auto I = std::next(MF.begin()), E = MF.end(); I != E; ++I)
-      I->addLiveIn(SystemZ::R11D);
+    for (MachineBasicBlock &MBBJ : llvm::drop_begin(MF))
+      MBBJ.addLiveIn(SystemZ::R11D);
   }
 
   // Skip over the FPR/VR saves.

llvm/lib/TextAPI/TextStub.cpp

@@ -1121,9 +1121,9 @@ TextAPIReader::get(MemoryBufferRef InputBuffer) {
   auto File = std::unique_ptr<InterfaceFile>(
       const_cast<InterfaceFile *>(Files.front()));
 
-  for (auto Iter = std::next(Files.begin()); Iter != Files.end(); ++Iter)
+  for (const InterfaceFile *FI : llvm::drop_begin(Files))
     File->addDocument(
-        std::shared_ptr<InterfaceFile>(const_cast<InterfaceFile *>(*Iter)));
+        std::shared_ptr<InterfaceFile>(const_cast<InterfaceFile *>(FI)));
 
   if (YAMLIn.error())
     return make_error<StringError>(Ctx.ErrorMessage, YAMLIn.error());

llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp

@@ -1623,11 +1623,10 @@ struct DSEState {
 
       // Find the common post-dominator of all killing blocks.
       BasicBlock *CommonPred = *KillingBlocks.begin();
-      for (auto I = std::next(KillingBlocks.begin()), E = KillingBlocks.end();
-           I != E; I++) {
+      for (BasicBlock *BB : llvm::drop_begin(KillingBlocks)) {
         if (!CommonPred)
           break;
-        CommonPred = PDT.findNearestCommonDominator(CommonPred, *I);
+        CommonPred = PDT.findNearestCommonDominator(CommonPred, BB);
       }
 
       // If CommonPred is in the set of killing blocks, just check if it

llvm/utils/TableGen/CodeGenRegisters.cpp

@@ -1624,9 +1624,9 @@ static void computeUberSets(std::vector<UberRegSet> &UberSets,
     assert(USetID && "register number 0 is invalid");
 
     AllocatableRegs.insert((*Regs.begin())->EnumValue);
-    for (auto I = std::next(Regs.begin()), E = Regs.end(); I != E; ++I) {
-      AllocatableRegs.insert((*I)->EnumValue);
-      UberSetIDs.join(USetID, (*I)->EnumValue);
+    for (const CodeGenRegister *CGR : llvm::drop_begin(Regs)) {
+      AllocatableRegs.insert(CGR->EnumValue);
+      UberSetIDs.join(USetID, CGR->EnumValue);
     }
   }
   // Combine non-allocatable regs.