diff --git a/examples/BrainF/BrainF.cpp b/examples/BrainF/BrainF.cpp
index 97ecdab0fe9..91d813a6c3b 100644
--- a/examples/BrainF/BrainF.cpp
+++ b/examples/BrainF/BrainF.cpp
@@ -339,7 +339,7 @@ void BrainF::readloop(PHINode *phi, BasicBlock *oldbb, BasicBlock *testbb,
         switch(c) {
           case '-':
             direction = -1;
-            // Fall through
+            LLVM_FALLTHROUGH;
 
           case '+':
             if (cursym == SYM_CHANGE) {
@@ -360,7 +360,7 @@ void BrainF::readloop(PHINode *phi, BasicBlock *oldbb, BasicBlock *testbb,
 
           case '<':
             direction = -1;
-            // Fall through
+            LLVM_FALLTHROUGH;
 
           case '>':
             if (cursym == SYM_MOVE) {
diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp
index af688f98d7c..a28db6c269e 100644
--- a/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/lib/Analysis/BasicAliasAnalysis.cpp
@@ -227,7 +227,7 @@ static bool isObjectSize(const Value *V, uint64_t Size, const DataLayout &DL,
           Offset = 0;
           return V;
         }
-      // FALL THROUGH.
+        LLVM_FALLTHROUGH;
       case Instruction::Add:
         V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, ZExtBits,
                                 SExtBits, DL, Depth + 1, AC, DT, NSW, NUW);
diff --git a/lib/Analysis/MemoryDependenceAnalysis.cpp b/lib/Analysis/MemoryDependenceAnalysis.cpp
index 894b27b5462..549d9902f1a 100644
--- a/lib/Analysis/MemoryDependenceAnalysis.cpp
+++ b/lib/Analysis/MemoryDependenceAnalysis.cpp
@@ -1010,7 +1010,7 @@ SortNonLocalDepInfoCache(MemoryDependenceResults::NonLocalDepInfo &Cache,
     MemoryDependenceResults::NonLocalDepInfo::iterator Entry =
         std::upper_bound(Cache.begin(), Cache.end() - 1, Val);
     Cache.insert(Entry, Val);
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
   }
   case 1:
     // One new entry, Just insert the new value at the appropriate position.
diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index 24ac1e3c666..e58f9a645cb 100644
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/lib/Analysis/ScalarEvolution.cpp
@@ -4288,7 +4288,7 @@ const SCEV *ScalarEvolution::createNodeForSelectOrPHI(Instruction *I,
   case ICmpInst::ICMP_SLT:
   case ICmpInst::ICMP_SLE:
     std::swap(LHS, RHS);
-  // fall through
+    LLVM_FALLTHROUGH;
   case ICmpInst::ICMP_SGT:
   case ICmpInst::ICMP_SGE:
     // a >s b ? a+x : b+x  ->  smax(a, b)+x
@@ -4311,7 +4311,7 @@ const SCEV *ScalarEvolution::createNodeForSelectOrPHI(Instruction *I,
   case ICmpInst::ICMP_ULT:
   case ICmpInst::ICMP_ULE:
     std::swap(LHS, RHS);
-  // fall through
+    LLVM_FALLTHROUGH;
   case ICmpInst::ICMP_UGT:
   case ICmpInst::ICMP_UGE:
     // a >u b ? a+x : b+x  ->  umax(a, b)+x
@@ -8502,7 +8502,7 @@ static bool IsKnownPredicateViaMinOrMax(ScalarEvolution &SE,
 
   case ICmpInst::ICMP_SGE:
     std::swap(LHS, RHS);
-    // fall through
+    LLVM_FALLTHROUGH;
   case ICmpInst::ICMP_SLE:
     return
       // min(A, ...) <= A
@@ -8512,7 +8512,7 @@ static bool IsKnownPredicateViaMinOrMax(ScalarEvolution &SE,
 
   case ICmpInst::ICMP_UGE:
     std::swap(LHS, RHS);
-    // fall through
+    LLVM_FALLTHROUGH;
   case ICmpInst::ICMP_ULE:
     return
       // min(A, ...) <= A
@@ -9858,8 +9858,10 @@ ScalarEvolution::computeBlockDisposition(const SCEV *S, const BasicBlock *BB) {
     const SCEVAddRecExpr *AR = cast<SCEVAddRecExpr>(S);
     if (!DT.dominates(AR->getLoop()->getHeader(), BB))
       return DoesNotDominateBlock;
+
+    // Fall through into SCEVNAryExpr handling.
+    LLVM_FALLTHROUGH;
   }
-  // FALL THROUGH into SCEVNAryExpr handling.
   case scAddExpr:
   case scMulExpr:
   case scUMaxExpr:
diff --git a/lib/Analysis/TargetLibraryInfo.cpp b/lib/Analysis/TargetLibraryInfo.cpp
index 8569c4dbdd2..2a47390b4cb 100644
--- a/lib/Analysis/TargetLibraryInfo.cpp
+++ b/lib/Analysis/TargetLibraryInfo.cpp
@@ -324,6 +324,7 @@ static void initialize(TargetLibraryInfoImpl &TLI, const Triple &T,
     // on Linux.
     //
     // Fall through to disable all of them.
+    LLVM_FALLTHROUGH;
   default:
     TLI.setUnavailable(LibFunc::exp10);
     TLI.setUnavailable(LibFunc::exp10f);
diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp
index 41a924390be..48305f42023 100644
--- a/lib/Analysis/ValueTracking.cpp
+++ b/lib/Analysis/ValueTracking.cpp
@@ -1012,7 +1012,8 @@ static void computeKnownBitsFromOperator(const Operator *I, APInt &KnownZero,
   case Instruction::PtrToInt:
   case Instruction::IntToPtr:
   case Instruction::AddrSpaceCast: // Pointers could be different sizes.
-    // FALL THROUGH and handle them the same as zext/trunc.
+    // Fall through and handle them the same as zext/trunc.
+    LLVM_FALLTHROUGH;
   case Instruction::ZExt:
   case Instruction::Trunc: {
     Type *SrcTy = I->getOperand(0)->getType();
@@ -2559,7 +2560,7 @@ bool llvm::CannotBeOrderedLessThanZero(const Value *V,
     // x*x is always non-negative or a NaN.
     if (I->getOperand(0) == I->getOperand(1))
       return true;
-    // Fall through
+    LLVM_FALLTHROUGH;
   case Instruction::FAdd:
   case Instruction::FDiv:
   case Instruction::FRem:
diff --git a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 05bf1cb192e..0fed4e91eef 100644
--- a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -1784,7 +1784,7 @@ const MCExpr *AsmPrinter::lowerConstant(const Constant *CV) {
     // expression properly.  This is important for differences between
     // blockaddress labels.  Since the two labels are in the same function, it
     // is reasonable to treat their delta as a 32-bit value.
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
   case Instruction::BitCast:
     return lowerConstant(CE->getOperand(0));
 
diff --git a/lib/CodeGen/AsmPrinter/DIE.cpp b/lib/CodeGen/AsmPrinter/DIE.cpp
index 2aaa85a5809..c5b7277c1ec 100644
--- a/lib/CodeGen/AsmPrinter/DIE.cpp
+++ b/lib/CodeGen/AsmPrinter/DIE.cpp
@@ -247,17 +247,17 @@ void DIEInteger::EmitValue(const AsmPrinter *Asm, dwarf::Form Form) const {
     // FIXME: Is there a better way to do this?
     Asm->OutStreamer->AddBlankLine();
     return;
-  case dwarf::DW_FORM_flag:  // Fall thru
-  case dwarf::DW_FORM_ref1:  // Fall thru
+  case dwarf::DW_FORM_flag:  LLVM_FALLTHROUGH;
+  case dwarf::DW_FORM_ref1:  LLVM_FALLTHROUGH;
   case dwarf::DW_FORM_data1: Size = 1; break;
-  case dwarf::DW_FORM_ref2:  // Fall thru
+  case dwarf::DW_FORM_ref2:  LLVM_FALLTHROUGH;
   case dwarf::DW_FORM_data2: Size = 2; break;
-  case dwarf::DW_FORM_sec_offset: // Fall thru
-  case dwarf::DW_FORM_strp: // Fall thru
-  case dwarf::DW_FORM_ref4:  // Fall thru
+  case dwarf::DW_FORM_sec_offset: LLVM_FALLTHROUGH;
+  case dwarf::DW_FORM_strp:  LLVM_FALLTHROUGH;
+  case dwarf::DW_FORM_ref4:  LLVM_FALLTHROUGH;
   case dwarf::DW_FORM_data4: Size = 4; break;
-  case dwarf::DW_FORM_ref8:  // Fall thru
-  case dwarf::DW_FORM_ref_sig8:  // Fall thru
+  case dwarf::DW_FORM_ref8:  LLVM_FALLTHROUGH;
+  case dwarf::DW_FORM_ref_sig8:  LLVM_FALLTHROUGH;
   case dwarf::DW_FORM_data8: Size = 8; break;
   case dwarf::DW_FORM_GNU_str_index: Asm->EmitULEB128(Integer); return;
   case dwarf::DW_FORM_GNU_addr_index: Asm->EmitULEB128(Integer); return;
@@ -279,17 +279,17 @@ void DIEInteger::EmitValue(const AsmPrinter *Asm, dwarf::Form Form) const {
 unsigned DIEInteger::SizeOf(const AsmPrinter *AP, dwarf::Form Form) const {
   switch (Form) {
   case dwarf::DW_FORM_flag_present: return 0;
-  case dwarf::DW_FORM_flag:  // Fall thru
-  case dwarf::DW_FORM_ref1:  // Fall thru
+  case dwarf::DW_FORM_flag:  LLVM_FALLTHROUGH;
+  case dwarf::DW_FORM_ref1:  LLVM_FALLTHROUGH;
   case dwarf::DW_FORM_data1: return sizeof(int8_t);
-  case dwarf::DW_FORM_ref2:  // Fall thru
+  case dwarf::DW_FORM_ref2:  LLVM_FALLTHROUGH;
   case dwarf::DW_FORM_data2: return sizeof(int16_t);
-  case dwarf::DW_FORM_sec_offset: // Fall thru
-  case dwarf::DW_FORM_strp: // Fall thru
-  case dwarf::DW_FORM_ref4:  // Fall thru
+  case dwarf::DW_FORM_sec_offset: LLVM_FALLTHROUGH;
+  case dwarf::DW_FORM_strp:  LLVM_FALLTHROUGH;
+  case dwarf::DW_FORM_ref4:  LLVM_FALLTHROUGH;
   case dwarf::DW_FORM_data4: return sizeof(int32_t);
-  case dwarf::DW_FORM_ref8:  // Fall thru
-  case dwarf::DW_FORM_ref_sig8:  // Fall thru
+  case dwarf::DW_FORM_ref8:  LLVM_FALLTHROUGH;
+  case dwarf::DW_FORM_ref_sig8:  LLVM_FALLTHROUGH;
   case dwarf::DW_FORM_data8: return sizeof(int64_t);
   case dwarf::DW_FORM_GNU_str_index: return getULEB128Size(Integer);
   case dwarf::DW_FORM_GNU_addr_index: return getULEB128Size(Integer);
diff --git a/lib/CodeGen/RegAllocFast.cpp b/lib/CodeGen/RegAllocFast.cpp
index d3dcb4f7573..df6e6fb1c5b 100644
--- a/lib/CodeGen/RegAllocFast.cpp
+++ b/lib/CodeGen/RegAllocFast.cpp
@@ -360,7 +360,7 @@ void RAFast::usePhysReg(MachineOperand &MO) {
     break;
   case regReserved:
     PhysRegState[PhysReg] = regFree;
-    // Fall through
+    LLVM_FALLTHROUGH;
   case regFree:
     MO.setIsKill();
     return;
@@ -389,7 +389,7 @@ void RAFast::usePhysReg(MachineOperand &MO) {
       assert((TRI->isSuperRegister(PhysReg, Alias) ||
               TRI->isSuperRegister(Alias, PhysReg)) &&
              "Instruction is not using a subregister of a reserved register");
-      // Fall through.
+      LLVM_FALLTHROUGH;
     case regFree:
       if (TRI->isSuperRegister(PhysReg, Alias)) {
         // Leave the superregister in the working set.
@@ -421,7 +421,7 @@ void RAFast::definePhysReg(MachineInstr &MI, unsigned PhysReg,
     break;
   default:
     spillVirtReg(MI, VirtReg);
-    // Fall through.
+    LLVM_FALLTHROUGH;
   case regFree:
   case regReserved:
     PhysRegState[PhysReg] = NewState;
@@ -437,7 +437,7 @@ void RAFast::definePhysReg(MachineInstr &MI, unsigned PhysReg,
       break;
     default:
       spillVirtReg(MI, VirtReg);
-      // Fall through.
+      LLVM_FALLTHROUGH;
     case regFree:
     case regReserved:
       PhysRegState[Alias] = regDisabled;
diff --git a/lib/CodeGen/RegisterCoalescer.cpp b/lib/CodeGen/RegisterCoalescer.cpp
index 617ece902e0..2d9a61be853 100644
--- a/lib/CodeGen/RegisterCoalescer.cpp
+++ b/lib/CodeGen/RegisterCoalescer.cpp
@@ -2231,8 +2231,8 @@ void JoinVals::computeAssignment(unsigned ValNo, JoinVals &Other) {
     if ((OtherV.WriteLanes & ~V.ValidLanes) != 0 && TrackSubRegLiveness)
       OtherV.ErasableImplicitDef = false;
     OtherV.Pruned = true;
+    LLVM_FALLTHROUGH;
   }
-    // Fall through.
   default:
     // This value number needs to go in the final joined live range.
     Assignments[ValNo] = NewVNInfo.size();
@@ -2517,7 +2517,7 @@ void JoinVals::eraseInstrs(SmallPtrSetImpl<MachineInstr*> &ErasedInstrs,
       // make it appear like an unused value number.
       VNI->markUnused();
       DEBUG(dbgs() << "\t\tremoved " << i << '@' << Def << ": " << LR << '\n');
-      // FALL THROUGH.
+      LLVM_FALLTHROUGH;
     }
 
     case CR_Erase: {
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 44be069a4d0..5c8a2947e92 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -1579,7 +1579,7 @@ SDValue DAGCombiner::visitTokenFactor(SDNode *N) {
           Changed = true;
           break;
         }
-        // Fall thru
+        LLVM_FALLTHROUGH;
 
       default:
         // Only add if it isn't already in the list.
diff --git a/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp b/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
index e6d80caaaa5..16365c0e808 100644
--- a/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
@@ -1123,12 +1123,12 @@ void SelectionDAGLegalize::LegalizeOp(SDNode *Node) {
         ReplaceNode(Node, ResultVals.data());
         return;
       }
+      LLVM_FALLTHROUGH;
     }
-      // FALL THROUGH
     case TargetLowering::Expand:
       if (ExpandNode(Node))
         return;
-      // FALL THROUGH
+      LLVM_FALLTHROUGH;
     case TargetLowering::LibCall:
       ConvertNodeToLibcall(Node);
       return;
diff --git a/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp b/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp
index 3c9cb17b58b..709c2cebee7 100644
--- a/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp
+++ b/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp
@@ -362,7 +362,7 @@ SDValue VectorLegalizer::LegalizeOp(SDValue Op) {
       Result = Tmp1;
       break;
     }
-    // FALL THROUGH
+    LLVM_FALLTHROUGH;
   }
   case TargetLowering::Expand:
     Result = Expand(Op);
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 3b2e592713e..9b8f8239d5d 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -1943,29 +1943,29 @@ SDValue SelectionDAG::FoldSetCC(EVT VT, SDValue N1, SDValue N2,
       default: break;
       case ISD::SETEQ:  if (R==APFloat::cmpUnordered)
                           return getUNDEF(VT);
-                        // fall through
+                        LLVM_FALLTHROUGH;
       case ISD::SETOEQ: return getConstant(R==APFloat::cmpEqual, dl, VT);
       case ISD::SETNE:  if (R==APFloat::cmpUnordered)
                           return getUNDEF(VT);
-                        // fall through
+                        LLVM_FALLTHROUGH;
       case ISD::SETONE: return getConstant(R==APFloat::cmpGreaterThan ||
                                            R==APFloat::cmpLessThan, dl, VT);
       case ISD::SETLT:  if (R==APFloat::cmpUnordered)
                           return getUNDEF(VT);
-                        // fall through
+                        LLVM_FALLTHROUGH;
       case ISD::SETOLT: return getConstant(R==APFloat::cmpLessThan, dl, VT);
       case ISD::SETGT:  if (R==APFloat::cmpUnordered)
                           return getUNDEF(VT);
-                        // fall through
+                        LLVM_FALLTHROUGH;
       case ISD::SETOGT: return getConstant(R==APFloat::cmpGreaterThan, dl, VT);
       case ISD::SETLE:  if (R==APFloat::cmpUnordered)
                           return getUNDEF(VT);
-                        // fall through
+                        LLVM_FALLTHROUGH;
       case ISD::SETOLE: return getConstant(R==APFloat::cmpLessThan ||
                                            R==APFloat::cmpEqual, dl, VT);
       case ISD::SETGE:  if (R==APFloat::cmpUnordered)
                           return getUNDEF(VT);
-                        // fall through
+                        LLVM_FALLTHROUGH;
       case ISD::SETOGE: return getConstant(R==APFloat::cmpGreaterThan ||
                                            R==APFloat::cmpEqual, dl, VT);
       case ISD::SETO:   return getConstant(R!=APFloat::cmpUnordered, dl, VT);
@@ -2350,8 +2350,8 @@ void SelectionDAG::computeKnownBits(SDValue Op, APInt &KnownZero,
         }
       }
     }
+    LLVM_FALLTHROUGH;
   }
-  // fall through
   case ISD::ADD:
   case ISD::ADDE: {
     // Output known-0 bits are known if clear or set in both the low clear bits
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 4ba31cd3a9e..3f56ad75dd7 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -2482,7 +2482,7 @@ static bool isVectorReductionOp(const User *I) {
     if (const FPMathOperator *FPOp = dyn_cast<const FPMathOperator>(Inst))
       if (FPOp->getFastMathFlags().unsafeAlgebra())
         break;
-    // Fall through.
+    LLVM_FALLTHROUGH;
   default:
     return false;
   }
@@ -9243,4 +9243,3 @@ void SelectionDAGBuilder::visitSwitch(const SwitchInst &SI) {
     lowerWorkItem(W, SI.getCondition(), SwitchMBB, DefaultMBB);
   }
 }
-
diff --git a/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index 0411a4ab796..3102a9a7084 100644
--- a/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -1147,8 +1147,8 @@ bool TargetLowering::SimplifyDemandedBits(SDValue Op,
     // See if the operation should be performed at a smaller bit width.
     if (TLO.ShrinkDemandedOp(Op, BitWidth, NewMask, dl))
       return true;
+    LLVM_FALLTHROUGH;
   }
-  // FALL THROUGH
   default:
     // Just use computeKnownBits to compute output bits.
     TLO.DAG.computeKnownBits(Op, KnownZero, KnownOne, Depth);
@@ -2301,7 +2301,7 @@ void TargetLowering::LowerAsmOperandForConstraint(SDValue Op,
       Ops.push_back(Op);
       return;
     }
-    // fall through
+    LLVM_FALLTHROUGH;
   case 'i':    // Simple Integer or Relocatable Constant
   case 'n':    // Simple Integer
   case 's': {  // Relocatable Constant
diff --git a/lib/Fuzzer/FuzzerMutate.cpp b/lib/Fuzzer/FuzzerMutate.cpp
index d3eaac086c7..4a9fdd460cc 100644
--- a/lib/Fuzzer/FuzzerMutate.cpp
+++ b/lib/Fuzzer/FuzzerMutate.cpp
@@ -286,7 +286,7 @@ size_t MutationDispatcher::Mutate_CrossOver(uint8_t *Data, size_t Size,
       NewSize = InsertPartOf(O.data(), O.size(), U.data(), U.size(), MaxSize);
       if (NewSize)
         break;
-      // Fallthrough
+      LLVM_FALLTHROUGH;
     case 2:
       NewSize = CopyPartOf(O.data(), O.size(), U.data(), U.size());
       break;
diff --git a/lib/IR/Function.cpp b/lib/IR/Function.cpp
index d82e1492966..f1546f17d9e 100644
--- a/lib/IR/Function.cpp
+++ b/lib/IR/Function.cpp
@@ -748,9 +748,9 @@ static void DecodeIITType(unsigned &NextElt, ArrayRef<unsigned char> Infos,
   case IIT_EMPTYSTRUCT:
     OutputTable.push_back(IITDescriptor::get(IITDescriptor::Struct, 0));
     return;
-  case IIT_STRUCT5: ++StructElts; // FALL THROUGH.
-  case IIT_STRUCT4: ++StructElts; // FALL THROUGH.
-  case IIT_STRUCT3: ++StructElts; // FALL THROUGH.
+  case IIT_STRUCT5: ++StructElts; LLVM_FALLTHROUGH;
+  case IIT_STRUCT4: ++StructElts; LLVM_FALLTHROUGH;
+  case IIT_STRUCT3: ++StructElts; LLVM_FALLTHROUGH;
   case IIT_STRUCT2: {
     OutputTable.push_back(IITDescriptor::get(IITDescriptor::Struct,StructElts));
 
diff --git a/lib/MC/MCObjectFileInfo.cpp b/lib/MC/MCObjectFileInfo.cpp
index bbf6123e391..79e9dcc0a24 100644
--- a/lib/MC/MCObjectFileInfo.cpp
+++ b/lib/MC/MCObjectFileInfo.cpp
@@ -311,6 +311,7 @@ void MCObjectFileInfo::initELFMCObjectFileInfo(const Triple &T) {
     if (Ctx->getAsmInfo()->getExceptionHandlingType() == ExceptionHandling::ARM)
       break;
     // Fallthrough if not using EHABI
+    LLVM_FALLTHROUGH;
   case Triple::ppc:
   case Triple::x86:
     PersonalityEncoding = PositionIndependent
diff --git a/lib/Support/CommandLine.cpp b/lib/Support/CommandLine.cpp
index 102bc909889..551cdefcbe4 100644
--- a/lib/Support/CommandLine.cpp
+++ b/lib/Support/CommandLine.cpp
@@ -1228,7 +1228,7 @@ bool CommandLineParser::ParseCommandLineOptions(int argc,
         switch (PositionalOpts[i]->getNumOccurrencesFlag()) {
         case cl::Optional:
           Done = true; // Optional arguments want _at most_ one value
-        // FALL THROUGH
+          LLVM_FALLTHROUGH;
         case cl::ZeroOrMore: // Zero or more will take all they can get...
         case cl::OneOrMore:  // One or more will take all they can get...
           ProvidePositionalOption(PositionalOpts[i],
@@ -1282,7 +1282,7 @@ bool CommandLineParser::ParseCommandLineOptions(int argc,
         Opt.second->error("must be specified at least once!");
         ErrorParsing = true;
       }
-    // Fall through
+      LLVM_FALLTHROUGH;
     default:
       break;
     }
@@ -1337,7 +1337,7 @@ bool Option::addOccurrence(unsigned pos, StringRef ArgName, StringRef Value,
   case Required:
     if (NumOccurrences > 1)
       return error("must occur exactly one time!", ArgName);
-  // Fall through
+    LLVM_FALLTHROUGH;
   case OneOrMore:
   case ZeroOrMore:
   case ConsumeAfter:
diff --git a/lib/Support/FoldingSet.cpp b/lib/Support/FoldingSet.cpp
index 52baf865d83..a27d3174a4f 100644
--- a/lib/Support/FoldingSet.cpp
+++ b/lib/Support/FoldingSet.cpp
@@ -127,8 +127,8 @@ void FoldingSetNodeID::AddString(StringRef String) {
   // Pos will have overshot size by 4 - #bytes left over.
   // No need to take endianness into account here - this is always executed.
   switch (Pos - Size) {
-  case 1: V = (V << 8) | (unsigned char)String[Size - 3]; // Fall thru.
-  case 2: V = (V << 8) | (unsigned char)String[Size - 2]; // Fall thru.
+  case 1: V = (V << 8) | (unsigned char)String[Size - 3]; LLVM_FALLTHROUGH;
+  case 2: V = (V << 8) | (unsigned char)String[Size - 2]; LLVM_FALLTHROUGH;
   case 3: V = (V << 8) | (unsigned char)String[Size - 1]; break;
   default: return; // Nothing left.
   }
diff --git a/lib/Support/raw_ostream.cpp b/lib/Support/raw_ostream.cpp
index 275fe1d4945..c4a7b145588 100644
--- a/lib/Support/raw_ostream.cpp
+++ b/lib/Support/raw_ostream.cpp
@@ -344,10 +344,10 @@ void raw_ostream::copy_to_buffer(const char *Ptr, size_t Size) {
   // Handle short strings specially, memcpy isn't very good at very short
   // strings.
   switch (Size) {
-  case 4: OutBufCur[3] = Ptr[3]; // FALL THROUGH
-  case 3: OutBufCur[2] = Ptr[2]; // FALL THROUGH
-  case 2: OutBufCur[1] = Ptr[1]; // FALL THROUGH
-  case 1: OutBufCur[0] = Ptr[0]; // FALL THROUGH
+  case 4: OutBufCur[3] = Ptr[3]; LLVM_FALLTHROUGH;
+  case 3: OutBufCur[2] = Ptr[2]; LLVM_FALLTHROUGH;
+  case 2: OutBufCur[1] = Ptr[1]; LLVM_FALLTHROUGH;
+  case 1: OutBufCur[0] = Ptr[0]; LLVM_FALLTHROUGH;
   case 0: break;
   default:
     memcpy(OutBufCur, Ptr, Size);
diff --git a/lib/TableGen/TGLexer.cpp b/lib/TableGen/TGLexer.cpp
index 0f14928d049..acf1fb20afa 100644
--- a/lib/TableGen/TGLexer.cpp
+++ b/lib/TableGen/TGLexer.cpp
@@ -222,7 +222,7 @@ tgtok::TokKind TGLexer::LexString() {
     case '\0':
       if (CurPtr == CurBuf.end())
         return ReturnError(StrStart, "End of file in string literal");
-      // FALL THROUGH
+      LLVM_FALLTHROUGH;
     default:
       return ReturnError(CurPtr, "invalid escape in string literal");
     }
diff --git a/lib/Target/AArch64/AArch64ConditionalCompares.cpp b/lib/Target/AArch64/AArch64ConditionalCompares.cpp
index 6e9ca8428bb..c4005fcb1fb 100644
--- a/lib/Target/AArch64/AArch64ConditionalCompares.cpp
+++ b/lib/Target/AArch64/AArch64ConditionalCompares.cpp
@@ -329,7 +329,7 @@ MachineInstr *SSACCmpConv::findConvertibleCompare(MachineBasicBlock *MBB) {
         ++NumImmRangeRejs;
         return nullptr;
       }
-    // Fall through.
+      LLVM_FALLTHROUGH;
     case AArch64::SUBSWrr:
     case AArch64::SUBSXrr:
     case AArch64::ADDSWrr:
diff --git a/lib/Target/AArch64/AArch64ISelLowering.cpp b/lib/Target/AArch64/AArch64ISelLowering.cpp
index 05775a84bef..2236071e5ff 100644
--- a/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -7057,7 +7057,7 @@ bool AArch64TargetLowering::isExtFreeImpl(const Instruction *Ext) const {
       // trunc(sext ty1 to ty2) to ty1.
       if (Instr->getType() == Ext->getOperand(0)->getType())
         continue;
-    // FALL THROUGH.
+      LLVM_FALLTHROUGH;
     default:
       return false;
     }
diff --git a/lib/Target/AMDGPU/AMDGPUAsmPrinter.cpp b/lib/Target/AMDGPU/AMDGPUAsmPrinter.cpp
index 8866dcd4ecb..c0ecae849bd 100644
--- a/lib/Target/AMDGPU/AMDGPUAsmPrinter.cpp
+++ b/lib/Target/AMDGPU/AMDGPUAsmPrinter.cpp
@@ -286,7 +286,7 @@ void AMDGPUAsmPrinter::EmitProgramInfoR600(const MachineFunction &MF) {
   if (STM.getGeneration() >= R600Subtarget::EVERGREEN) {
     // Evergreen / Northern Islands
     switch (MF.getFunction()->getCallingConv()) {
-    default: // Fall through
+    default: LLVM_FALLTHROUGH;
     case CallingConv::AMDGPU_CS: RsrcReg = R_0288D4_SQ_PGM_RESOURCES_LS; break;
     case CallingConv::AMDGPU_GS: RsrcReg = R_028878_SQ_PGM_RESOURCES_GS; break;
     case CallingConv::AMDGPU_PS: RsrcReg = R_028844_SQ_PGM_RESOURCES_PS; break;
@@ -295,9 +295,9 @@ void AMDGPUAsmPrinter::EmitProgramInfoR600(const MachineFunction &MF) {
   } else {
     // R600 / R700
     switch (MF.getFunction()->getCallingConv()) {
-    default: // Fall through
-    case CallingConv::AMDGPU_GS: // Fall through
-    case CallingConv::AMDGPU_CS: // Fall through
+    default: LLVM_FALLTHROUGH;
+    case CallingConv::AMDGPU_GS: LLVM_FALLTHROUGH;
+    case CallingConv::AMDGPU_CS: LLVM_FALLTHROUGH;
     case CallingConv::AMDGPU_VS: RsrcReg = R_028868_SQ_PGM_RESOURCES_VS; break;
     case CallingConv::AMDGPU_PS: RsrcReg = R_028850_SQ_PGM_RESOURCES_PS; break;
     }
@@ -574,7 +574,7 @@ void AMDGPUAsmPrinter::getSIProgramInfo(SIProgramInfo &ProgInfo,
 
 static unsigned getRsrcReg(CallingConv::ID CallConv) {
   switch (CallConv) {
-  default: // Fall through
+  default: LLVM_FALLTHROUGH;
   case CallingConv::AMDGPU_CS: return R_00B848_COMPUTE_PGM_RSRC1;
   case CallingConv::AMDGPU_GS: return R_00B228_SPI_SHADER_PGM_RSRC1_GS;
   case CallingConv::AMDGPU_PS: return R_00B028_SPI_SHADER_PGM_RSRC1_PS;
diff --git a/lib/Target/ARM/ARMFastISel.cpp b/lib/Target/ARM/ARMFastISel.cpp
index 960b711c6de..9b4747b1b08 100644
--- a/lib/Target/ARM/ARMFastISel.cpp
+++ b/lib/Target/ARM/ARMFastISel.cpp
@@ -1868,6 +1868,7 @@ CCAssignFn *ARMFastISel::CCAssignFnForCall(CallingConv::ID CC,
       return (Return ? RetCC_ARM_AAPCS_VFP: CC_ARM_AAPCS_VFP);
     // Fall through to soft float variant, variadic functions don't
     // use hard floating point ABI.
+    LLVM_FALLTHROUGH;
   case CallingConv::ARM_AAPCS:
     return (Return ? RetCC_ARM_AAPCS: CC_ARM_AAPCS);
   case CallingConv::ARM_APCS:
diff --git a/lib/Target/ARM/ARMISelLowering.cpp b/lib/Target/ARM/ARMISelLowering.cpp
index ed126c177e7..cc0b58f9f33 100644
--- a/lib/Target/ARM/ARMISelLowering.cpp
+++ b/lib/Target/ARM/ARMISelLowering.cpp
@@ -8659,7 +8659,7 @@ static bool isConditionalZeroOrAllOnes(SDNode *N, bool AllOnes,
     // (zext cc) can never be the all ones value.
     if (AllOnes)
       return false;
-    // Fall through.
+    LLVM_FALLTHROUGH;
   case ISD::SIGN_EXTEND: {
     SDLoc dl(N);
     EVT VT = N->getValueType(0);
@@ -11409,7 +11409,7 @@ bool ARMTargetLowering::isLegalAddressingMode(const DataLayout &DL,
   case 1:
     if (Subtarget->isThumb1Only())
       return false;
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
   default:
     // ARM doesn't support any R+R*scale+imm addr modes.
     if (AM.BaseOffs)
diff --git a/lib/Target/ARM/Disassembler/ARMDisassembler.cpp b/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
index 3196a57ccc3..4da28861abd 100644
--- a/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
+++ b/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
@@ -1432,7 +1432,7 @@ static DecodeStatus DecodeCopMemInstruction(MCInst &Inst, unsigned Insn,
     case ARM::STC_POST:
     case ARM::STCL_POST:
       imm |= U << 8;
-      // fall through.
+      LLVM_FALLTHROUGH;
     default:
       // The 'option' variant doesn't encode 'U' in the immediate since
       // the immediate is unsigned [0,255].
@@ -2555,6 +2555,7 @@ static DecodeStatus DecodeVLDInstruction(MCInst &Inst, unsigned Insn,
       break;
     }
     // Fall through to handle the register offset variant.
+    LLVM_FALLTHROUGH;
   case ARM::VLD1d8wb_fixed:
   case ARM::VLD1d16wb_fixed:
   case ARM::VLD1d32wb_fixed:
@@ -4157,7 +4158,7 @@ static DecodeStatus DecodeMSRMask(MCInst &Inst, unsigned Val,
     case 0x93: // faultmask_ns
       if (!(FeatureBits[ARM::HasV8MMainlineOps]))
         return MCDisassembler::Fail;
-      // fall through
+      LLVM_FALLTHROUGH;
     case 10:   // msplim
     case 11:   // psplim
     case 0x88: // msp_ns
@@ -5310,4 +5311,3 @@ static DecodeStatus DecoderForMRRC2AndMCRR2(llvm::MCInst &Inst, unsigned Val,
 
   return S;
 }
-
diff --git a/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp b/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp
index 9b600baa273..64c51806b20 100644
--- a/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp
+++ b/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp
@@ -630,7 +630,7 @@ unsigned ARMAsmBackend::adjustFixupValue(const MCFixup &Fixup, uint64_t Value,
   case ARM::fixup_arm_pcrel_10:
     Value = Value - 4; // ARM fixups offset by an additional word and don't
                        // need to adjust for the half-word ordering.
-                       // Fall through.
+    LLVM_FALLTHROUGH;
   case ARM::fixup_t2_pcrel_10: {
     // Offset by 4, adjusted by two due to the half-word ordering of thumb.
     Value = Value - 4;
@@ -657,7 +657,7 @@ unsigned ARMAsmBackend::adjustFixupValue(const MCFixup &Fixup, uint64_t Value,
   case ARM::fixup_arm_pcrel_9:
     Value = Value - 4; // ARM fixups offset by an additional word and don't
                        // need to adjust for the half-word ordering.
-                       // Fall through.
+    LLVM_FALLTHROUGH;
   case ARM::fixup_t2_pcrel_9: {
     // Offset by 4, adjusted by two due to the half-word ordering of thumb.
     Value = Value - 4;
diff --git a/lib/Target/Hexagon/HexagonRDFOpt.cpp b/lib/Target/Hexagon/HexagonRDFOpt.cpp
index e67389217e8..efd28350183 100644
--- a/lib/Target/Hexagon/HexagonRDFOpt.cpp
+++ b/lib/Target/Hexagon/HexagonRDFOpt.cpp
@@ -116,8 +116,8 @@ bool HexagonCP::interpretAsCopy(const MachineInstr *MI, EqualityMap &EM) {
       const MachineOperand &A = MI->getOperand(2);
       if (!A.isImm() || A.getImm() != 0)
         return false;
+      LLVM_FALLTHROUGH;
     }
-    // Fall through.
     case Hexagon::A2_tfr: {
       const MachineOperand &DstOp = MI->getOperand(0);
       const MachineOperand &SrcOp = MI->getOperand(1);
diff --git a/lib/Target/Hexagon/HexagonSplitDouble.cpp b/lib/Target/Hexagon/HexagonSplitDouble.cpp
index f832ff2db9f..e4e259be139 100644
--- a/lib/Target/Hexagon/HexagonSplitDouble.cpp
+++ b/lib/Target/Hexagon/HexagonSplitDouble.cpp
@@ -337,6 +337,7 @@ int32_t HexagonSplitDoubleRegs::profit(const MachineInstr *MI) const {
       if (V == 0 || V == -1)
         return 10;
       // Fall through into A2_combinew.
+      LLVM_FALLTHROUGH;
     }
     case Hexagon::A2_combinew:
       return 2;
diff --git a/lib/Target/Mips/AsmParser/MipsAsmParser.cpp b/lib/Target/Mips/AsmParser/MipsAsmParser.cpp
index e3f0d16d660..0fd56ad8384 100644
--- a/lib/Target/Mips/AsmParser/MipsAsmParser.cpp
+++ b/lib/Target/Mips/AsmParser/MipsAsmParser.cpp
@@ -1606,7 +1606,7 @@ bool MipsAsmParser::processInstruction(MCInst &Inst, SMLoc IDLoc,
     case Mips::BBIT1:
     case Mips::BBIT132:
       assert(hasCnMips() && "instruction only valid for octeon cpus");
-      // Fall through
+      LLVM_FALLTHROUGH;
 
     case Mips::BEQ:
     case Mips::BNE:
diff --git a/lib/Target/NVPTX/NVPTXAsmPrinter.cpp b/lib/Target/NVPTX/NVPTXAsmPrinter.cpp
index e627be0b23d..b975f2719d4 100644
--- a/lib/Target/NVPTX/NVPTXAsmPrinter.cpp
+++ b/lib/Target/NVPTX/NVPTXAsmPrinter.cpp
@@ -2124,7 +2124,7 @@ NVPTXAsmPrinter::lowerConstantForGV(const Constant *CV, bool ProcessingGeneric)
     // expression properly.  This is important for differences between
     // blockaddress labels.  Since the two labels are in the same function, it
     // is reasonable to treat their delta as a 32-bit value.
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
   case Instruction::BitCast:
     return lowerConstantForGV(CE->getOperand(0), ProcessingGeneric);
 
diff --git a/lib/Target/Sparc/SparcInstrInfo.cpp b/lib/Target/Sparc/SparcInstrInfo.cpp
index ecedded3fa0..bf1de7f1293 100644
--- a/lib/Target/Sparc/SparcInstrInfo.cpp
+++ b/lib/Target/Sparc/SparcInstrInfo.cpp
@@ -118,19 +118,19 @@ static SPCC::CondCodes GetOppositeBranchCondition(SPCC::CondCodes CC)
   
   case SPCC::CPCC_A:   return SPCC::CPCC_N;
   case SPCC::CPCC_N:   return SPCC::CPCC_A;
-  case SPCC::CPCC_3:   // Fall through
-  case SPCC::CPCC_2:   // Fall through
-  case SPCC::CPCC_23:  // Fall through
-  case SPCC::CPCC_1:   // Fall through
-  case SPCC::CPCC_13:  // Fall through
-  case SPCC::CPCC_12:  // Fall through
-  case SPCC::CPCC_123: // Fall through
-  case SPCC::CPCC_0:   // Fall through
-  case SPCC::CPCC_03:  // Fall through
-  case SPCC::CPCC_02:  // Fall through
-  case SPCC::CPCC_023: // Fall through
-  case SPCC::CPCC_01:  // Fall through
-  case SPCC::CPCC_013: // Fall through
+  case SPCC::CPCC_3:   LLVM_FALLTHROUGH;
+  case SPCC::CPCC_2:   LLVM_FALLTHROUGH;
+  case SPCC::CPCC_23:  LLVM_FALLTHROUGH;
+  case SPCC::CPCC_1:   LLVM_FALLTHROUGH;
+  case SPCC::CPCC_13:  LLVM_FALLTHROUGH;
+  case SPCC::CPCC_12:  LLVM_FALLTHROUGH;
+  case SPCC::CPCC_123: LLVM_FALLTHROUGH;
+  case SPCC::CPCC_0:   LLVM_FALLTHROUGH;
+  case SPCC::CPCC_03:  LLVM_FALLTHROUGH;
+  case SPCC::CPCC_02:  LLVM_FALLTHROUGH;
+  case SPCC::CPCC_023: LLVM_FALLTHROUGH;
+  case SPCC::CPCC_01:  LLVM_FALLTHROUGH;
+  case SPCC::CPCC_013: LLVM_FALLTHROUGH;
   case SPCC::CPCC_012:
       // "Opposite" code is not meaningful, as we don't know
       // what the CoProc condition means here. The cond-code will
diff --git a/lib/Target/SystemZ/SystemZISelDAGToDAG.cpp b/lib/Target/SystemZ/SystemZISelDAGToDAG.cpp
index cd7fcc3070a..c74d396e3aa 100644
--- a/lib/Target/SystemZ/SystemZISelDAGToDAG.cpp
+++ b/lib/Target/SystemZ/SystemZISelDAGToDAG.cpp
@@ -832,7 +832,7 @@ bool SystemZDAGToDAGISel::expandRxSBG(RxSBGOperands &RxSBG) const {
       RxSBG.Input = N.getOperand(0);
       return true;
     }
-    // Fall through.
+    LLVM_FALLTHROUGH;
 
   case ISD::SIGN_EXTEND: {
     // Check that the extension bits are don't-care (i.e. are masked out
@@ -1265,7 +1265,7 @@ void SystemZDAGToDAGISel::Select(SDNode *Node) {
     if (Node->getOperand(1).getOpcode() != ISD::Constant)
       if (tryRxSBG(Node, SystemZ::RNSBG))
         return;
-    // Fall through.
+    LLVM_FALLTHROUGH;
   case ISD::ROTL:
   case ISD::SHL:
   case ISD::SRL:
diff --git a/lib/Target/X86/InstPrinter/X86InstComments.cpp b/lib/Target/X86/InstPrinter/X86InstComments.cpp
index 4657bbbe151..1953e92efde 100644
--- a/lib/Target/X86/InstPrinter/X86InstComments.cpp
+++ b/lib/Target/X86/InstPrinter/X86InstComments.cpp
@@ -382,7 +382,7 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
   case X86::VBLENDPDrri:
   case X86::VBLENDPDYrri:
     Src2Name = getRegName(MI->getOperand(2).getReg());
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
   case X86::BLENDPDrmi:
   case X86::VBLENDPDrmi:
   case X86::VBLENDPDYrmi:
@@ -398,7 +398,7 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
   case X86::VBLENDPSrri:
   case X86::VBLENDPSYrri:
     Src2Name = getRegName(MI->getOperand(2).getReg());
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
   case X86::BLENDPSrmi:
   case X86::VBLENDPSrmi:
   case X86::VBLENDPSYrmi:
@@ -414,7 +414,7 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
   case X86::VPBLENDWrri:
   case X86::VPBLENDWYrri:
     Src2Name = getRegName(MI->getOperand(2).getReg());
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
   case X86::PBLENDWrmi:
   case X86::VPBLENDWrmi:
   case X86::VPBLENDWYrmi:
@@ -429,7 +429,7 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
   case X86::VPBLENDDrri:
   case X86::VPBLENDDYrri:
     Src2Name = getRegName(MI->getOperand(2).getReg());
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
   case X86::VPBLENDDrmi:
   case X86::VPBLENDDYrmi:
     if (MI->getOperand(NumOperands - 1).isImm())
@@ -444,7 +444,7 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
   case X86::VINSERTPSrr:
   case X86::VINSERTPSZrr:
     Src2Name = getRegName(MI->getOperand(2).getReg());
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
   case X86::INSERTPSrm:
   case X86::VINSERTPSrm:
   case X86::VINSERTPSZrm:
@@ -507,7 +507,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
 
   CASE_MOVDUP(MOVSLDUP, r)
     Src1Name = getRegName(MI->getOperand(NumOperands - 1).getReg());
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   CASE_MOVDUP(MOVSLDUP, m)
     DestName = getRegName(MI->getOperand(0).getReg());
     DecodeMOVSLDUPMask(getRegOperandVectorVT(MI, MVT::f32, 0), ShuffleMask);
@@ -515,7 +516,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
 
   CASE_MOVDUP(MOVSHDUP, r)
     Src1Name = getRegName(MI->getOperand(NumOperands - 1).getReg());
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   CASE_MOVDUP(MOVSHDUP, m)
     DestName = getRegName(MI->getOperand(0).getReg());
     DecodeMOVSHDUPMask(getRegOperandVectorVT(MI, MVT::f32, 0), ShuffleMask);
@@ -523,7 +525,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
 
   CASE_MOVDUP(MOVDDUP, r)
     Src1Name = getRegName(MI->getOperand(NumOperands - 1).getReg());
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   CASE_MOVDUP(MOVDDUP, m)
     DestName = getRegName(MI->getOperand(0).getReg());
     DecodeMOVDDUPMask(getRegOperandVectorVT(MI, MVT::f64, 0), ShuffleMask);
@@ -566,7 +569,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
   CASE_SHUF(PALIGNR, rri)
     Src1Name = getRegName(MI->getOperand(NumOperands - 2).getReg());
     RegForm = true;
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   CASE_SHUF(PALIGNR, rmi)
     Src2Name = getRegName(MI->getOperand(NumOperands-(RegForm?3:7)).getReg());
     DestName = getRegName(MI->getOperand(0).getReg());
@@ -578,7 +582,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
 
   CASE_SHUF(PSHUFD, ri)
     Src1Name = getRegName(MI->getOperand(NumOperands - 2).getReg());
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   CASE_SHUF(PSHUFD, mi)
     DestName = getRegName(MI->getOperand(0).getReg());
     if (MI->getOperand(NumOperands - 1).isImm())
@@ -589,7 +594,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
 
   CASE_SHUF(PSHUFHW, ri)
     Src1Name = getRegName(MI->getOperand(NumOperands - 2).getReg());
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   CASE_SHUF(PSHUFHW, mi)
     DestName = getRegName(MI->getOperand(0).getReg());
     if (MI->getOperand(NumOperands - 1).isImm())
@@ -600,7 +606,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
 
   CASE_SHUF(PSHUFLW, ri)
     Src1Name = getRegName(MI->getOperand(NumOperands - 2).getReg());
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   CASE_SHUF(PSHUFLW, mi)
     DestName = getRegName(MI->getOperand(0).getReg());
     if (MI->getOperand(NumOperands - 1).isImm())
@@ -611,7 +618,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
 
   case X86::MMX_PSHUFWri:
     Src1Name = getRegName(MI->getOperand(1).getReg());
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   case X86::MMX_PSHUFWmi:
     DestName = getRegName(MI->getOperand(0).getReg());
     if (MI->getOperand(NumOperands - 1).isImm())
@@ -622,7 +630,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
 
   case X86::PSWAPDrr:
     Src1Name = getRegName(MI->getOperand(1).getReg());
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   case X86::PSWAPDrm:
     DestName = getRegName(MI->getOperand(0).getReg());
     DecodePSWAPMask(MVT::v2i32, ShuffleMask);
@@ -632,7 +641,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
   case X86::MMX_PUNPCKHBWirr:
     Src2Name = getRegName(MI->getOperand(NumOperands - 1).getReg());
     RegForm = true;
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   CASE_UNPCK(PUNPCKHBW, m)
   case X86::MMX_PUNPCKHBWirm:
     Src1Name = getRegName(MI->getOperand(NumOperands-(RegForm?2:6)).getReg());
@@ -644,7 +654,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
   case X86::MMX_PUNPCKHWDirr:
     Src2Name = getRegName(MI->getOperand(NumOperands - 1).getReg());
     RegForm = true;
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   CASE_UNPCK(PUNPCKHWD, m)
   case X86::MMX_PUNPCKHWDirm:
     Src1Name = getRegName(MI->getOperand(NumOperands-(RegForm?2:6)).getReg());
@@ -656,7 +667,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
   case X86::MMX_PUNPCKHDQirr:
     Src2Name = getRegName(MI->getOperand(NumOperands - 1).getReg());
     RegForm = true;
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   CASE_UNPCK(PUNPCKHDQ, m)
   case X86::MMX_PUNPCKHDQirm:
     Src1Name = getRegName(MI->getOperand(NumOperands-(RegForm?2:6)).getReg());
@@ -667,7 +679,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
   CASE_UNPCK(PUNPCKHQDQ, r)
     Src2Name = getRegName(MI->getOperand(NumOperands - 1).getReg());
     RegForm = true;
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   CASE_UNPCK(PUNPCKHQDQ, m)
     Src1Name = getRegName(MI->getOperand(NumOperands-(RegForm?2:6)).getReg());
     DestName = getRegName(MI->getOperand(0).getReg());
@@ -678,7 +691,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
   case X86::MMX_PUNPCKLBWirr:
     Src2Name = getRegName(MI->getOperand(NumOperands - 1).getReg());
     RegForm = true;
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   CASE_UNPCK(PUNPCKLBW, m)
   case X86::MMX_PUNPCKLBWirm:
     Src1Name = getRegName(MI->getOperand(NumOperands-(RegForm?2:6)).getReg());
@@ -690,7 +704,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
   case X86::MMX_PUNPCKLWDirr:
     Src2Name = getRegName(MI->getOperand(NumOperands - 1).getReg());
     RegForm = true;
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   CASE_UNPCK(PUNPCKLWD, m)
   case X86::MMX_PUNPCKLWDirm:
     Src1Name = getRegName(MI->getOperand(NumOperands-(RegForm?2:6)).getReg());
@@ -702,7 +717,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
   case X86::MMX_PUNPCKLDQirr:
     Src2Name = getRegName(MI->getOperand(NumOperands - 1).getReg());
     RegForm = true;
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   CASE_UNPCK(PUNPCKLDQ, m)
   case X86::MMX_PUNPCKLDQirm:
     Src1Name = getRegName(MI->getOperand(NumOperands-(RegForm?2:6)).getReg());
@@ -713,7 +729,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
   CASE_UNPCK(PUNPCKLQDQ, r)
     Src2Name = getRegName(MI->getOperand(NumOperands - 1).getReg());
     RegForm = true;
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   CASE_UNPCK(PUNPCKLQDQ, m)
     Src1Name = getRegName(MI->getOperand(NumOperands-(RegForm?2:6)).getReg());
     DestName = getRegName(MI->getOperand(0).getReg());
@@ -723,7 +740,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
   CASE_SHUF(SHUFPD, rri)
     Src2Name = getRegName(MI->getOperand(NumOperands - 2).getReg());
     RegForm = true;
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   CASE_SHUF(SHUFPD, rmi)
     if (MI->getOperand(NumOperands - 1).isImm())
       DecodeSHUFPMask(getRegOperandVectorVT(MI, MVT::f64, 0),
@@ -736,7 +754,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
   CASE_SHUF(SHUFPS, rri)
     Src2Name = getRegName(MI->getOperand(NumOperands - 2).getReg());
     RegForm = true;
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   CASE_SHUF(SHUFPS, rmi)
     if (MI->getOperand(NumOperands - 1).isImm())
       DecodeSHUFPMask(getRegOperandVectorVT(MI, MVT::f32, 0),
@@ -749,7 +768,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
   CASE_VSHUF(64X2, r)
     Src2Name = getRegName(MI->getOperand(NumOperands - 2).getReg());
     RegForm = true;
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   CASE_VSHUF(64X2, m)
     decodeVSHUF64x2FamilyMask(getRegOperandVectorVT(MI, MVT::i64, 0),
                               MI->getOperand(NumOperands - 1).getImm(),
@@ -761,7 +781,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
   CASE_VSHUF(32X4, r)
     Src2Name = getRegName(MI->getOperand(NumOperands - 2).getReg());
     RegForm = true;
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   CASE_VSHUF(32X4, m)
     decodeVSHUF64x2FamilyMask(getRegOperandVectorVT(MI, MVT::i32, 0),
                               MI->getOperand(NumOperands - 1).getImm(),
@@ -773,7 +794,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
   CASE_UNPCK(UNPCKLPD, r)
     Src2Name = getRegName(MI->getOperand(NumOperands - 1).getReg());
     RegForm = true;
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   CASE_UNPCK(UNPCKLPD, m)
     DecodeUNPCKLMask(getRegOperandVectorVT(MI, MVT::f64, 0), ShuffleMask);
     Src1Name = getRegName(MI->getOperand(NumOperands-(RegForm?2:6)).getReg());
@@ -783,7 +805,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
   CASE_UNPCK(UNPCKLPS, r)
     Src2Name = getRegName(MI->getOperand(NumOperands - 1).getReg());
     RegForm = true;
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   CASE_UNPCK(UNPCKLPS, m)
     DecodeUNPCKLMask(getRegOperandVectorVT(MI, MVT::f32, 0), ShuffleMask);
     Src1Name = getRegName(MI->getOperand(NumOperands-(RegForm?2:6)).getReg());
@@ -793,7 +816,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
   CASE_UNPCK(UNPCKHPD, r)
     Src2Name = getRegName(MI->getOperand(NumOperands - 1).getReg());
     RegForm = true;
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   CASE_UNPCK(UNPCKHPD, m)
     DecodeUNPCKHMask(getRegOperandVectorVT(MI, MVT::f64, 0), ShuffleMask);
     Src1Name = getRegName(MI->getOperand(NumOperands-(RegForm?2:6)).getReg());
@@ -803,7 +827,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
   CASE_UNPCK(UNPCKHPS, r)
     Src2Name = getRegName(MI->getOperand(NumOperands - 1).getReg());
     RegForm = true;
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   CASE_UNPCK(UNPCKHPS, m)
     DecodeUNPCKHMask(getRegOperandVectorVT(MI, MVT::f32, 0), ShuffleMask);
     Src1Name = getRegName(MI->getOperand(NumOperands-(RegForm?2:6)).getReg());
@@ -812,7 +837,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
 
   CASE_VPERMILPI(PERMILPS, r)
     Src1Name = getRegName(MI->getOperand(NumOperands - 2).getReg());
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   CASE_VPERMILPI(PERMILPS, m)
     if (MI->getOperand(NumOperands - 1).isImm())
       DecodePSHUFMask(getRegOperandVectorVT(MI, MVT::f32, 0),
@@ -823,7 +849,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
 
   CASE_VPERMILPI(PERMILPD, r)
     Src1Name = getRegName(MI->getOperand(NumOperands - 2).getReg());
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   CASE_VPERMILPI(PERMILPD, m)
     if (MI->getOperand(NumOperands - 1).isImm())
       DecodePSHUFMask(getRegOperandVectorVT(MI, MVT::f64, 0),
@@ -835,7 +862,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
   case X86::VPERM2F128rr:
   case X86::VPERM2I128rr:
     Src2Name = getRegName(MI->getOperand(2).getReg());
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   case X86::VPERM2F128rm:
   case X86::VPERM2I128rm:
     // For instruction comments purpose, assume the 256-bit vector is v4i64.
@@ -849,7 +877,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
 
   CASE_VPERM(PERMPD, r)
     Src1Name = getRegName(MI->getOperand(NumOperands - 2).getReg());
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   CASE_VPERM(PERMPD, m)
     if (MI->getOperand(NumOperands - 1).isImm())
       DecodeVPERMMask(getRegOperandVectorVT(MI, MVT::f64, 0),
@@ -860,7 +889,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
 
   CASE_VPERM(PERMQ, r)
     Src1Name = getRegName(MI->getOperand(NumOperands - 2).getReg());
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   CASE_VPERM(PERMQ, m)
     if (MI->getOperand(NumOperands - 1).isImm())
       DecodeVPERMMask(getRegOperandVectorVT(MI, MVT::i64, 0),
@@ -874,7 +904,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
   case X86::VMOVSDZrr:
     Src2Name = getRegName(MI->getOperand(2).getReg());
     Src1Name = getRegName(MI->getOperand(1).getReg());
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   case X86::MOVSDrm:
   case X86::VMOVSDrm:
   case X86::VMOVSDZrm:
@@ -887,7 +918,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
   case X86::VMOVSSZrr:
     Src2Name = getRegName(MI->getOperand(2).getReg());
     Src1Name = getRegName(MI->getOperand(1).getReg());
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   case X86::MOVSSrm:
   case X86::VMOVSSrm:
   case X86::VMOVSSZrm:
@@ -901,7 +933,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
   case X86::VMOVZPQILo2PQIrr:
   case X86::VMOVZPQILo2PQIZrr:
     Src1Name = getRegName(MI->getOperand(1).getReg());
-  // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   case X86::MOVQI2PQIrm:
   case X86::MOVZQI2PQIrm:
   case X86::MOVZPQILo2PQIrm:
@@ -954,7 +987,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
   CASE_PMOVZX(PMOVZXBD, r)
   CASE_PMOVZX(PMOVZXBQ, r)
     Src1Name = getRegName(MI->getOperand(NumOperands - 1).getReg());
-  // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   CASE_PMOVZX(PMOVZXBW, m)
   CASE_PMOVZX(PMOVZXBD, m)
   CASE_PMOVZX(PMOVZXBQ, m)
@@ -965,7 +999,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
   CASE_PMOVZX(PMOVZXWD, r)
   CASE_PMOVZX(PMOVZXWQ, r)
     Src1Name = getRegName(MI->getOperand(NumOperands - 1).getReg());
-  // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   CASE_PMOVZX(PMOVZXWD, m)
   CASE_PMOVZX(PMOVZXWQ, m)
     DecodeZeroExtendMask(MVT::i16, getZeroExtensionResultType(MI), ShuffleMask);
@@ -974,7 +1009,8 @@ bool llvm::EmitAnyX86InstComments(const MCInst *MI, raw_ostream &OS,
 
   CASE_PMOVZX(PMOVZXDQ, r)
     Src1Name = getRegName(MI->getOperand(NumOperands - 1).getReg());
-  // FALL THROUGH.
+    LLVM_FALLTHROUGH;
+
   CASE_PMOVZX(PMOVZXDQ, m)
     DecodeZeroExtendMask(MVT::i32, getZeroExtensionResultType(MI), ShuffleMask);
     DestName = getRegName(MI->getOperand(0).getReg());
diff --git a/lib/Target/X86/X86FastISel.cpp b/lib/Target/X86/X86FastISel.cpp
index ada3d99b8e2..f30331f0a11 100644
--- a/lib/Target/X86/X86FastISel.cpp
+++ b/lib/Target/X86/X86FastISel.cpp
@@ -2969,7 +2969,7 @@ bool X86FastISel::fastLowerArguments() {
     default: llvm_unreachable("Unexpected value type.");
     case MVT::i32: SrcReg = GPR32ArgRegs[GPRIdx++]; break;
     case MVT::i64: SrcReg = GPR64ArgRegs[GPRIdx++]; break;
-    case MVT::f32: // fall-through
+    case MVT::f32: LLVM_FALLTHROUGH;
     case MVT::f64: SrcReg = XMMArgRegs[FPRIdx++]; break;
     }
     unsigned DstReg = FuncInfo.MF->addLiveIn(SrcReg, RC);
@@ -3508,7 +3508,7 @@ unsigned X86FastISel::X86MaterializeInt(const ConstantInt *CI, MVT VT) {
   unsigned Opc = 0;
   switch (VT.SimpleTy) {
   default: llvm_unreachable("Unexpected value type");
-  case MVT::i1:  VT = MVT::i8; // fall-through
+  case MVT::i1:  VT = MVT::i8;       LLVM_FALLTHROUGH;
   case MVT::i8:  Opc = X86::MOV8ri;  break;
   case MVT::i16: Opc = X86::MOV16ri; break;
   case MVT::i32: Opc = X86::MOV32ri; break;
diff --git a/lib/Target/X86/X86ISelDAGToDAG.cpp b/lib/Target/X86/X86ISelDAGToDAG.cpp
index bce0acbd206..e0ec983edac 100644
--- a/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -1234,7 +1234,7 @@ bool X86DAGToDAGISel::matchAddressRecursively(SDValue N, X86ISelAddressMode &AM,
   case ISD::UMUL_LOHI:
     // A mul_lohi where we need the low part can be folded as a plain multiply.
     if (N.getResNo() != 0) break;
-    // FALL THROUGH
+    LLVM_FALLTHROUGH;
   case ISD::MUL:
   case X86ISD::MUL_IMM:
     // X*[3,5,9] -> X+X*[2,4,8]
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 5c5c0dc1421..d3f61cc129f 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -15028,7 +15028,7 @@ SDValue X86TargetLowering::EmitTest(SDValue Op, unsigned X86CC, const SDLoc &dl,
       if (!Subtarget.hasBMI() || !isAndn || !isLegalAndnType)
         break;
     }
-    // FALL THROUGH
+    LLVM_FALLTHROUGH;
   case ISD::SUB:
   case ISD::OR:
   case ISD::XOR:
@@ -27635,7 +27635,7 @@ static SDValue checkBoolTestSetCCCombine(SDValue Cmp, X86::CondCode &CC) {
       break;
     assert(X86::CondCode(SetCC.getConstantOperandVal(0)) == X86::COND_B &&
            "Invalid use of SETCC_CARRY!");
-    // FALL THROUGH
+    LLVM_FALLTHROUGH;
   case X86ISD::SETCC:
     // Set the condition code or opposite one if necessary.
     CC = X86::CondCode(SetCC.getConstantOperandVal(0));
@@ -32229,7 +32229,7 @@ X86TargetLowering::getRegForInlineAsmConstraint(const TargetRegisterInfo *TRI,
       return std::make_pair(0U, &X86::VR64RegClass);
     case 'Y':   // SSE_REGS if SSE2 allowed
       if (!Subtarget.hasSSE2()) break;
-      // FALL THROUGH.
+      LLVM_FALLTHROUGH;
     case 'x':   // SSE_REGS if SSE1 allowed or AVX_REGS if AVX allowed
       if (!Subtarget.hasSSE1()) break;
 
diff --git a/lib/Target/X86/X86WinAllocaExpander.cpp b/lib/Target/X86/X86WinAllocaExpander.cpp
index cc82074e685..9f22ca1fd15 100644
--- a/lib/Target/X86/X86WinAllocaExpander.cpp
+++ b/lib/Target/X86/X86WinAllocaExpander.cpp
@@ -225,6 +225,7 @@ void X86WinAllocaExpander::lower(MachineInstr* MI, Lowering L) {
       break;
 
     // Fall through to make any remaining adjustment.
+    LLVM_FALLTHROUGH;
   case Sub:
     assert(Amount > 0);
     if (Amount == SlotSize) {
diff --git a/lib/Target/XCore/XCoreAsmPrinter.cpp b/lib/Target/XCore/XCoreAsmPrinter.cpp
index be66e6cb812..ba94ac772b8 100644
--- a/lib/Target/XCore/XCoreAsmPrinter.cpp
+++ b/lib/Target/XCore/XCoreAsmPrinter.cpp
@@ -140,7 +140,7 @@ void XCoreAsmPrinter::EmitGlobalVariable(const GlobalVariable *GV) {
     if (GV->hasWeakLinkage() || GV->hasLinkOnceLinkage() ||
         GV->hasCommonLinkage())
       OutStreamer->EmitSymbolAttribute(GVSym, MCSA_Weak);
-    // FALL THROUGH
+    LLVM_FALLTHROUGH;
   case GlobalValue::InternalLinkage:
   case GlobalValue::PrivateLinkage:
     break;
diff --git a/lib/Transforms/IPO/FunctionAttrs.cpp b/lib/Transforms/IPO/FunctionAttrs.cpp
index 1de5f4f076f..ce648e2ea51 100644
--- a/lib/Transforms/IPO/FunctionAttrs.cpp
+++ b/lib/Transforms/IPO/FunctionAttrs.cpp
@@ -775,7 +775,8 @@ static bool isFunctionMallocLike(Function *F, const SCCNodeSet &SCCNodes) {
           break;
         if (CS.getCalledFunction() && SCCNodes.count(CS.getCalledFunction()))
           break;
-      } // fall-through
+        LLVM_FALLTHROUGH;
+      }
       default:
         return false; // Did not come from an allocation.
       }
diff --git a/lib/Transforms/IPO/MergeFunctions.cpp b/lib/Transforms/IPO/MergeFunctions.cpp
index fe653a75ddb..726786a7f71 100644
--- a/lib/Transforms/IPO/MergeFunctions.cpp
+++ b/lib/Transforms/IPO/MergeFunctions.cpp
@@ -828,6 +828,7 @@ int FunctionComparator::cmpTypes(Type *TyL, Type *TyR) const {
   default:
     llvm_unreachable("Unknown type!");
     // Fall through in Release mode.
+    LLVM_FALLTHROUGH;
   case Type::IntegerTyID:
     return cmpNumbers(cast<IntegerType>(TyL)->getBitWidth(),
                       cast<IntegerType>(TyR)->getBitWidth());
diff --git a/lib/Transforms/InstCombine/InstCombineCalls.cpp b/lib/Transforms/InstCombine/InstCombineCalls.cpp
index ea69ae92781..f00363e029c 100644
--- a/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -1473,7 +1473,7 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
       II->setArgOperand(1, LHS);
       return II;
     }
-    // fall through
+    LLVM_FALLTHROUGH;
 
   case Intrinsic::usub_with_overflow:
   case Intrinsic::ssub_with_overflow: {
diff --git a/lib/Transforms/InstCombine/InstCombineCompares.cpp b/lib/Transforms/InstCombine/InstCombineCompares.cpp
index cad8903c0ae..d422b463b9b 100644
--- a/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -2715,8 +2715,10 @@ bool InstCombiner::OptimizeOverflowCheck(OverflowCheckFlavor OCF, Value *LHS,
 
     if (OR == OverflowResult::AlwaysOverflows)
       return SetResult(Builder->CreateAdd(LHS, RHS), Builder->getTrue(), true);
+
+    // Fall through uadd into sadd
+    LLVM_FALLTHROUGH;
   }
-  // FALL THROUGH uadd into sadd
   case OCF_SIGNED_ADD: {
     // X + 0 -> {X, false}
     if (match(RHS, m_Zero()))
@@ -2756,7 +2758,8 @@ bool InstCombiner::OptimizeOverflowCheck(OverflowCheckFlavor OCF, Value *LHS,
                        true);
     if (OR == OverflowResult::AlwaysOverflows)
       return SetResult(Builder->CreateMul(LHS, RHS), Builder->getTrue(), true);
-  } // FALL THROUGH
+    LLVM_FALLTHROUGH;
+  }
   case OCF_SIGNED_MUL:
     // X * undef -> undef
     if (isa<UndefValue>(RHS))
@@ -3311,28 +3314,28 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
 
     case ICmpInst::ICMP_UGT:
       std::swap(Op0, Op1);                   // Change icmp ugt -> icmp ult
-      // FALL THROUGH
+      LLVM_FALLTHROUGH;
     case ICmpInst::ICMP_ULT:{                // icmp ult i1 A, B -> ~A & B
       Value *Not = Builder->CreateNot(Op0, I.getName() + "tmp");
       return BinaryOperator::CreateAnd(Not, Op1);
     }
     case ICmpInst::ICMP_SGT:
       std::swap(Op0, Op1);                   // Change icmp sgt -> icmp slt
-      // FALL THROUGH
+      LLVM_FALLTHROUGH;
     case ICmpInst::ICMP_SLT: {               // icmp slt i1 A, B -> A & ~B
       Value *Not = Builder->CreateNot(Op1, I.getName() + "tmp");
       return BinaryOperator::CreateAnd(Not, Op0);
     }
     case ICmpInst::ICMP_UGE:
       std::swap(Op0, Op1);                   // Change icmp uge -> icmp ule
-      // FALL THROUGH
+      LLVM_FALLTHROUGH;
     case ICmpInst::ICMP_ULE: {               // icmp ule i1 A, B -> ~A | B
       Value *Not = Builder->CreateNot(Op0, I.getName() + "tmp");
       return BinaryOperator::CreateOr(Not, Op1);
     }
     case ICmpInst::ICMP_SGE:
       std::swap(Op0, Op1);                   // Change icmp sge -> icmp sle
-      // FALL THROUGH
+      LLVM_FALLTHROUGH;
     case ICmpInst::ICMP_SLE: {               // icmp sle i1 A, B -> A | ~B
       Value *Not = Builder->CreateNot(Op1, I.getName() + "tmp");
       return BinaryOperator::CreateOr(Not, Op0);
diff --git a/lib/Transforms/InstCombine/InstCombineShifts.cpp b/lib/Transforms/InstCombine/InstCombineShifts.cpp
index cc61fc77589..341692fa3f4 100644
--- a/lib/Transforms/InstCombine/InstCombineShifts.cpp
+++ b/lib/Transforms/InstCombine/InstCombineShifts.cpp
@@ -457,9 +457,9 @@ Instruction *InstCombiner::FoldShiftByConstant(Value *Op0, Constant *Op1,
                                          V1->getName()+".mask");
           return BinaryOperator::Create(Op0BO->getOpcode(), YS, XM);
         }
+        LLVM_FALLTHROUGH;
       }
 
-      // FALL THROUGH.
       case Instruction::Sub: {
         // Turn ((X >> C) + Y) << C  ->  (X + (Y << C)) & (~0 << C)
         if (isLeftShift && Op0BO->getOperand(0)->hasOneUse() &&
diff --git a/lib/Transforms/InstCombine/InstructionCombining.cpp b/lib/Transforms/InstCombine/InstructionCombining.cpp
index 2dab5b6d628..6424e083bd1 100644
--- a/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -1983,8 +1983,8 @@ isAllocSiteRemovable(Instruction *AI, SmallVectorImpl<WeakVH> &Users,
             MemIntrinsic *MI = cast<MemIntrinsic>(II);
             if (MI->isVolatile() || MI->getRawDest() != PI)
               return false;
+            LLVM_FALLTHROUGH;
           }
-          // fall through
           case Intrinsic::dbg_declare:
           case Intrinsic::dbg_value:
           case Intrinsic::invariant_start:
diff --git a/lib/Transforms/ObjCARC/PtrState.cpp b/lib/Transforms/ObjCARC/PtrState.cpp
index df64fa32f3f..a5afc8ad977 100644
--- a/lib/Transforms/ObjCARC/PtrState.cpp
+++ b/lib/Transforms/ObjCARC/PtrState.cpp
@@ -201,7 +201,7 @@ bool BottomUpPtrState::MatchWithRetain() {
     // imprecise release, clear our reverse insertion points.
     if (OldSeq != S_Use || IsTrackingImpreciseReleases())
       ClearReverseInsertPts();
-  // FALL THROUGH
+    LLVM_FALLTHROUGH;
   case S_CanRelease:
     return true;
   case S_None:
@@ -332,7 +332,7 @@ bool TopDownPtrState::MatchWithRelease(ARCMDKindCache &Cache,
   case S_CanRelease:
     if (OldSeq == S_Retain || ReleaseMetadata != nullptr)
       ClearReverseInsertPts();
-  // FALL THROUGH
+    LLVM_FALLTHROUGH;
   case S_Use:
     SetReleaseMetadata(ReleaseMetadata);
     SetTailCallRelease(cast<CallInst>(Release)->isTailCall());
diff --git a/tools/llvm-config/llvm-config.cpp b/tools/llvm-config/llvm-config.cpp
index 94d426be361..c63733f9a8b 100644
--- a/tools/llvm-config/llvm-config.cpp
+++ b/tools/llvm-config/llvm-config.cpp
@@ -599,7 +599,7 @@ int main(int argc, char **argv) {
         }
         errs()
             << "llvm-config: error: component libraries and shared library\n\n";
-      // fall through
+        LLVM_FALLTHROUGH;
       case LinkModeStatic:
         for (auto &Lib : MissingLibs)
           errs() << "llvm-config: error: missing: " << Lib << "\n";
diff --git a/tools/llvm-mc/Disassembler.cpp b/tools/llvm-mc/Disassembler.cpp
index 8185947fc5e..acc5a5f4cab 100644
--- a/tools/llvm-mc/Disassembler.cpp
+++ b/tools/llvm-mc/Disassembler.cpp
@@ -66,7 +66,7 @@ static bool PrintInsts(const MCDisassembler &DisAsm,
       SM.PrintMessage(SMLoc::getFromPointer(Bytes.second[Index]),
                       SourceMgr::DK_Warning,
                       "potentially undefined instruction encoding");
-      // Fall through
+      LLVM_FALLTHROUGH;
 
     case MCDisassembler::Success:
       Streamer.EmitInstruction(Inst, STI);
diff --git a/utils/TableGen/IntrinsicEmitter.cpp b/utils/TableGen/IntrinsicEmitter.cpp
index a676159e494..8eff650a848 100644
--- a/utils/TableGen/IntrinsicEmitter.cpp
+++ b/utils/TableGen/IntrinsicEmitter.cpp
@@ -287,10 +287,10 @@ static void EncodeFixedType(Record *R, std::vector<unsigned char> &ArgCodes,
   unsigned Tmp = 0;
   switch (VT) {
   default: break;
-  case MVT::iPTRAny: ++Tmp; // FALL THROUGH.
-  case MVT::vAny: ++Tmp; // FALL THROUGH.
-  case MVT::fAny: ++Tmp; // FALL THROUGH.
-  case MVT::iAny: ++Tmp; // FALL THROUGH.
+  case MVT::iPTRAny: ++Tmp; LLVM_FALLTHROUGH;
+  case MVT::vAny: ++Tmp;    LLVM_FALLTHROUGH;
+  case MVT::fAny: ++Tmp;    LLVM_FALLTHROUGH;
+  case MVT::iAny: ++Tmp;    LLVM_FALLTHROUGH;
   case MVT::Any: {
     // If this is an "any" valuetype, then the type is the type of the next
     // type in the list specified to getIntrinsic().