diff --git a/clang/include/clang/AST/ASTImporterSharedState.h b/clang/include/clang/AST/ASTImporterSharedState.h
--- a/clang/include/clang/AST/ASTImporterSharedState.h
+++ b/clang/include/clang/AST/ASTImporterSharedState.h
@@ -70,7 +70,7 @@
     if (Pos != ImportErrors.end())
       return Pos->second;
     else
-      return Optional<ASTImportError>();
+      return None;
   }
 
   void setImportDeclError(Decl *To, ASTImportError Error) {
diff --git a/clang/lib/AST/ASTImporter.cpp b/clang/lib/AST/ASTImporter.cpp
--- a/clang/lib/AST/ASTImporter.cpp
+++ b/clang/lib/AST/ASTImporter.cpp
@@ -223,7 +223,7 @@
     template<typename T>
     Expected<Optional<T>> import(Optional<T> From) {
       if (!From)
-        return Optional<T>();
+        return None;
       return import(*From);
     }
 
@@ -10022,7 +10022,7 @@
   if (Pos != ImportDeclErrors.end())
     return Pos->second;
   else
-    return Optional<ASTImportError>();
+    return None;
 }
 
 void ASTImporter::setImportDeclError(Decl *From, ASTImportError Error) {
diff --git a/clang/lib/ASTMatchers/Dynamic/Parser.cpp b/clang/lib/ASTMatchers/Dynamic/Parser.cpp
--- a/clang/lib/ASTMatchers/Dynamic/Parser.cpp
+++ b/clang/lib/ASTMatchers/Dynamic/Parser.cpp
@@ -910,10 +910,10 @@
                                Diagnostics *Error) {
   VariantValue Value;
   if (!parseExpression(Code, S, NamedValues, &Value, Error))
-    return llvm::Optional<DynTypedMatcher>();
+    return llvm::None;
   if (!Value.isMatcher()) {
     Error->addError(SourceRange(), Error->ET_ParserNotAMatcher);
-    return llvm::Optional<DynTypedMatcher>();
+    return llvm::None;
   }
   llvm::Optional<DynTypedMatcher> Result =
       Value.getMatcher().getSingleMatcher();
diff --git a/clang/lib/ASTMatchers/Dynamic/VariantValue.cpp b/clang/lib/ASTMatchers/Dynamic/VariantValue.cpp
--- a/clang/lib/ASTMatchers/Dynamic/VariantValue.cpp
+++ b/clang/lib/ASTMatchers/Dynamic/VariantValue.cpp
@@ -126,7 +126,7 @@
 
   llvm::Optional<DynTypedMatcher> getSingleMatcher() const override {
     if (Matchers.size() != 1)
-      return llvm::Optional<DynTypedMatcher>();
+      return llvm::None;
     return Matchers[0];
   }
 
@@ -190,7 +190,7 @@
       : Op(Op), Args(std::move(Args)) {}
 
   llvm::Optional<DynTypedMatcher> getSingleMatcher() const override {
-    return llvm::Optional<DynTypedMatcher>();
+    return llvm::None;
   }
 
   std::string getTypeAsString() const override {
diff --git a/clang/lib/CodeGen/CodeGenAction.cpp b/clang/lib/CodeGen/CodeGenAction.cpp
--- a/clang/lib/CodeGen/CodeGenAction.cpp
+++ b/clang/lib/CodeGen/CodeGenAction.cpp
@@ -698,7 +698,7 @@
     if (Pair.first == Hash)
       return Pair.second;
   }
-  return Optional<FullSourceLoc>();
+  return None;
 }
 
 void BackendConsumer::UnsupportedDiagHandler(
diff --git a/clang/lib/Driver/ToolChains/AVR.cpp b/clang/lib/Driver/ToolChains/AVR.cpp
--- a/clang/lib/Driver/ToolChains/AVR.cpp
+++ b/clang/lib/Driver/ToolChains/AVR.cpp
@@ -345,14 +345,14 @@
   for (const auto &MCU : MCUInfo)
     if (MCU.Name == MCUName)
       return Optional<StringRef>(MCU.Family);
-  return Optional<StringRef>();
+  return None;
 }
 
 llvm::Optional<unsigned> GetMCUSectionAddressData(StringRef MCUName) {
   for (const auto &MCU : MCUInfo)
     if (MCU.Name == MCUName && MCU.DataAddr > 0)
       return Optional<unsigned>(MCU.DataAddr);
-  return Optional<unsigned>();
+  return None;
 }
 
 const StringRef PossibleAVRLibcLocations[] = {
diff --git a/clang/lib/Driver/ToolChains/Arch/CSKY.cpp b/clang/lib/Driver/ToolChains/Arch/CSKY.cpp
--- a/clang/lib/Driver/ToolChains/Arch/CSKY.cpp
+++ b/clang/lib/Driver/ToolChains/Arch/CSKY.cpp
@@ -33,7 +33,7 @@
 
     if (ArchKind == llvm::CSKY::ArchKind::INVALID) {
       D.Diag(clang::diag::err_drv_invalid_arch_name) << A->getAsString(Args);
-      return llvm::Optional<llvm::StringRef>();
+      return llvm::None;
     }
     return llvm::Optional<llvm::StringRef>(A->getValue());
   }
@@ -42,7 +42,7 @@
     llvm::CSKY::ArchKind ArchKind = llvm::CSKY::parseCPUArch(A->getValue());
     if (ArchKind == llvm::CSKY::ArchKind::INVALID) {
       D.Diag(clang::diag::err_drv_clang_unsupported) << A->getAsString(Args);
-      return llvm::Optional<llvm::StringRef>();
+      return llvm::None;
     }
     return llvm::Optional<llvm::StringRef>(llvm::CSKY::getArchName(ArchKind));
   }
diff --git a/llvm/include/llvm/Analysis/TargetTransformInfoImpl.h b/llvm/include/llvm/Analysis/TargetTransformInfoImpl.h
--- a/llvm/include/llvm/Analysis/TargetTransformInfoImpl.h
+++ b/llvm/include/llvm/Analysis/TargetTransformInfoImpl.h
@@ -459,7 +459,7 @@
     case TargetTransformInfo::CacheLevel::L1D:
       [[fallthrough]];
     case TargetTransformInfo::CacheLevel::L2D:
-      return llvm::Optional<unsigned>();
+      return llvm::None;
     }
     llvm_unreachable("Unknown TargetTransformInfo::CacheLevel");
   }
@@ -470,7 +470,7 @@
     case TargetTransformInfo::CacheLevel::L1D:
       [[fallthrough]];
     case TargetTransformInfo::CacheLevel::L2D:
-      return llvm::Optional<unsigned>();
+      return llvm::None;
     }
 
     llvm_unreachable("Unknown TargetTransformInfo::CacheLevel");
diff --git a/llvm/lib/CodeGen/SelectOptimize.cpp b/llvm/lib/CodeGen/SelectOptimize.cpp
--- a/llvm/lib/CodeGen/SelectOptimize.cpp
+++ b/llvm/lib/CodeGen/SelectOptimize.cpp
@@ -949,7 +949,7 @@
       TTI->getInstructionCost(I, TargetTransformInfo::TCK_Latency);
   if (auto OC = ICost.getValue())
     return Optional<uint64_t>(*OC);
-  return Optional<uint64_t>();
+  return None;
 }
 
 ScaledNumber<uint64_t>
diff --git a/llvm/lib/DebugInfo/PDB/DIA/DIADataStream.cpp b/llvm/lib/DebugInfo/PDB/DIA/DIADataStream.cpp
--- a/llvm/lib/DebugInfo/PDB/DIA/DIADataStream.cpp
+++ b/llvm/lib/DebugInfo/PDB/DIA/DIADataStream.cpp
@@ -30,11 +30,11 @@
   DWORD RecordSize = 0;
   StreamData->Item(Index, 0, &RecordSize, nullptr);
   if (RecordSize == 0)
-    return llvm::Optional<RecordType>();
+    return llvm::None;
 
   Record.resize(RecordSize);
   if (S_OK != StreamData->Item(Index, RecordSize, &RecordSize, &Record[0]))
-    return llvm::Optional<RecordType>();
+    return llvm::None;
   return Record;
 }
 
diff --git a/llvm/lib/IR/BasicBlock.cpp b/llvm/lib/IR/BasicBlock.cpp
--- a/llvm/lib/IR/BasicBlock.cpp
+++ b/llvm/lib/IR/BasicBlock.cpp
@@ -512,7 +512,7 @@
       return Optional<uint64_t>(CI->getValue().getZExtValue());
     }
   }
-  return Optional<uint64_t>();
+  return None;
 }
 
 BasicBlock::iterator llvm::skipDebugIntrinsics(BasicBlock::iterator It) {
diff --git a/llvm/lib/LineEditor/LineEditor.cpp b/llvm/lib/LineEditor/LineEditor.cpp
--- a/llvm/lib/LineEditor/LineEditor.cpp
+++ b/llvm/lib/LineEditor/LineEditor.cpp
@@ -255,7 +255,7 @@
 
   // Either of these may mean end-of-file.
   if (!Line || LineLen == 0)
-    return Optional<std::string>();
+    return None;
 
   // Strip any newlines off the end of the string.
   while (LineLen > 0 &&
@@ -301,7 +301,7 @@
     char *Res = ::fgets(Buf, sizeof(Buf), Data->In);
     if (!Res) {
       if (Line.empty())
-        return Optional<std::string>();
+        return None;
       else
         return Line;
     }
diff --git a/llvm/lib/MC/MCSubtargetInfo.cpp b/llvm/lib/MC/MCSubtargetInfo.cpp
--- a/llvm/lib/MC/MCSubtargetInfo.cpp
+++ b/llvm/lib/MC/MCSubtargetInfo.cpp
@@ -336,16 +336,16 @@
 }
 
 Optional<unsigned> MCSubtargetInfo::getCacheSize(unsigned Level) const {
-  return Optional<unsigned>();
+  return None;
 }
 
 Optional<unsigned>
 MCSubtargetInfo::getCacheAssociativity(unsigned Level) const {
-  return Optional<unsigned>();
+  return None;
 }
 
 Optional<unsigned> MCSubtargetInfo::getCacheLineSize(unsigned Level) const {
-  return Optional<unsigned>();
+  return None;
 }
 
 unsigned MCSubtargetInfo::getPrefetchDistance() const {
diff --git a/llvm/lib/Object/Archive.cpp b/llvm/lib/Object/Archive.cpp
--- a/llvm/lib/Object/Archive.cpp
+++ b/llvm/lib/Object/Archive.cpp
@@ -1158,7 +1158,7 @@
         return MemberOrErr.takeError();
     }
   }
-  return Optional<Child>();
+  return None;
 }
 
 // Returns true if archive file contains no member file.
diff --git a/llvm/lib/Support/Z3Solver.cpp b/llvm/lib/Support/Z3Solver.cpp
--- a/llvm/lib/Support/Z3Solver.cpp
+++ b/llvm/lib/Support/Z3Solver.cpp
@@ -878,7 +878,7 @@
     if (res == Z3_L_FALSE)
       return false;
 
-    return Optional<bool>();
+    return None;
   }
 
   void push() override { return Z3_solver_push(Context.Context, Solver); }
diff --git a/llvm/lib/TableGen/Record.cpp b/llvm/lib/TableGen/Record.cpp
--- a/llvm/lib/TableGen/Record.cpp
+++ b/llvm/lib/TableGen/Record.cpp
@@ -2648,9 +2648,9 @@
 Record::getValueAsOptionalString(StringRef FieldName) const {
   const RecordVal *R = getValue(FieldName);
   if (!R || !R->getValue())
-    return llvm::Optional<StringRef>();
+    return llvm::None;
   if (isa<UnsetInit>(R->getValue()))
-    return llvm::Optional<StringRef>();
+    return llvm::None;
 
   if (StringInit *SI = dyn_cast<StringInit>(R->getValue()))
     return SI->getValue();
diff --git a/llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp b/llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
--- a/llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
+++ b/llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
@@ -2608,7 +2608,7 @@
   }
 
   if (Res == std::make_pair(-1, -1))
-    return Optional<std::pair<int, int>>();
+    return None;
 
   return Optional<std::pair<int, int>>(Res);
 }
diff --git a/llvm/lib/Target/ARM/ARMISelDAGToDAG.cpp b/llvm/lib/Target/ARM/ARMISelDAGToDAG.cpp
--- a/llvm/lib/Target/ARM/ARMISelDAGToDAG.cpp
+++ b/llvm/lib/Target/ARM/ARMISelDAGToDAG.cpp
@@ -3535,7 +3535,7 @@
   unsigned FirstOne = A.getBitWidth() - A.countLeadingZeros() - 1;
   unsigned LastOne = A.countTrailingZeros();
   if (A.countPopulation() != (FirstOne - LastOne + 1))
-    return Optional<std::pair<unsigned,unsigned>>();
+    return None;
   return std::make_pair(FirstOne, LastOne);
 }
 
diff --git a/llvm/lib/Target/PowerPC/PPCFastISel.cpp b/llvm/lib/Target/PowerPC/PPCFastISel.cpp
--- a/llvm/lib/Target/PowerPC/PPCFastISel.cpp
+++ b/llvm/lib/Target/PowerPC/PPCFastISel.cpp
@@ -226,7 +226,7 @@
     case CmpInst::FCMP_OLE:
     case CmpInst::FCMP_ONE:
     default:
-      return Optional<PPC::Predicate>();
+      return None;
 
     case CmpInst::FCMP_OEQ:
     case CmpInst::ICMP_EQ:
diff --git a/llvm/lib/Target/WebAssembly/Utils/WebAssemblyTypeUtilities.cpp b/llvm/lib/Target/WebAssembly/Utils/WebAssemblyTypeUtilities.cpp
--- a/llvm/lib/Target/WebAssembly/Utils/WebAssemblyTypeUtilities.cpp
+++ b/llvm/lib/Target/WebAssembly/Utils/WebAssemblyTypeUtilities.cpp
@@ -39,7 +39,7 @@
     return wasm::ValType::FUNCREF;
   if (Type == "externref")
     return wasm::ValType::EXTERNREF;
-  return Optional<wasm::ValType>();
+  return None;
 }
 
 WebAssembly::BlockType WebAssembly::parseBlockType(StringRef Type) {
diff --git a/mlir/lib/Dialect/Vector/Transforms/VectorTransforms.cpp b/mlir/lib/Dialect/Vector/Transforms/VectorTransforms.cpp
--- a/mlir/lib/Dialect/Vector/Transforms/VectorTransforms.cpp
+++ b/mlir/lib/Dialect/Vector/Transforms/VectorTransforms.cpp
@@ -157,7 +157,7 @@
   if (isInt) {
     if (kind == CombiningKind::MINF || kind == CombiningKind::MAXF)
       // Only valid for floating point types.
-      return Optional<Value>();
+      return None;
     mul = rewriter.create<arith::MulIOp>(loc, x, y);
   } else {
     // Float case.
@@ -166,7 +166,7 @@
         kind == CombiningKind::MAXSI || kind == CombiningKind::OR ||
         kind == CombiningKind::XOR)
       // Only valid for integer types.
-      return Optional<Value>();
+      return None;
     // Special case for fused multiply-add.
     if (acc && acc.getType().isa<VectorType>() && kind == CombiningKind::ADD) {
       return Optional<Value>(rewriter.create<vector::FMAOp>(loc, x, y, acc));
diff --git a/mlir/lib/Dialect/Vector/Utils/VectorUtils.cpp b/mlir/lib/Dialect/Vector/Utils/VectorUtils.cpp
--- a/mlir/lib/Dialect/Vector/Utils/VectorUtils.cpp
+++ b/mlir/lib/Dialect/Vector/Utils/VectorUtils.cpp
@@ -77,7 +77,7 @@
 Optional<SmallVector<int64_t, 4>> mlir::shapeRatio(ArrayRef<int64_t> superShape,
                                                    ArrayRef<int64_t> subShape) {
   if (superShape.size() < subShape.size()) {
-    return Optional<SmallVector<int64_t, 4>>();
+    return None;
   }
 
   // Starting from the end, compute the integer divisors.