diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
index 6bd2d38f65744a..7765ef0898dc27 100644
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -115,10 +115,10 @@ getOffloadTargetTriple(const Driver &D, const ArgList &Args) {
   switch (OffloadTargets.size()) {
   default:
     D.Diag(diag::err_drv_only_one_offload_target_supported);
-    return llvm::None;
+    return std::nullopt;
   case 0:
     D.Diag(diag::err_drv_invalid_or_unsupported_offload_target) << "";
-    return llvm::None;
+    return std::nullopt;
   case 1:
     break;
   }
@@ -138,10 +138,10 @@ getNVIDIAOffloadTargetTriple(const Driver &D, const ArgList &Args,
     if (Args.hasArg(options::OPT_emit_llvm))
       return TT;
     D.Diag(diag::err_drv_cuda_offload_only_emit_bc);
-    return llvm::None;
+    return std::nullopt;
   }
   D.Diag(diag::err_drv_invalid_or_unsupported_offload_target) << TT->str();
-  return llvm::None;
+  return std::nullopt;
 }
 static llvm::Optional<llvm::Triple>
 getHIPOffloadTargetTriple(const Driver &D, const ArgList &Args) {
@@ -150,7 +150,7 @@ getHIPOffloadTargetTriple(const Driver &D, const ArgList &Args) {
   }
   auto TT = getOffloadTargetTriple(D, Args);
   if (!TT)
-    return llvm::None;
+    return std::nullopt;
   if (TT->getArch() == llvm::Triple::amdgcn &&
       TT->getVendor() == llvm::Triple::AMD &&
       TT->getOS() == llvm::Triple::AMDHSA)
@@ -158,7 +158,7 @@ getHIPOffloadTargetTriple(const Driver &D, const ArgList &Args) {
   if (TT->getArch() == llvm::Triple::spirv64)
     return TT;
   D.Diag(diag::err_drv_invalid_or_unsupported_offload_target) << TT->str();
-  return llvm::None;
+  return std::nullopt;
 }
 
 // static
@@ -1596,7 +1596,7 @@ void Driver::generateCompilationDiagnostics(
     NewLLDInvocation.replaceArguments(std::move(ArgList));
 
     // Redirect stdout/stderr to /dev/null.
-    NewLLDInvocation.Execute({None, {""}, {""}}, nullptr, nullptr);
+    NewLLDInvocation.Execute({std::nullopt, {""}, {""}}, nullptr, nullptr);
     Diag(clang::diag::note_drv_command_failed_diag_msg) << BugReporMsg;
     Diag(clang::diag::note_drv_command_failed_diag_msg) << TmpName;
     Diag(clang::diag::note_drv_command_failed_diag_msg)
@@ -3128,7 +3128,7 @@ class OffloadingActionBuilder final {
     llvm::Optional<std::pair<llvm::StringRef, llvm::StringRef>>
     getConflictOffloadArchCombination(
         const std::set<StringRef> &GpuArchs) override {
-      return llvm::None;
+      return std::nullopt;
     }
 
     ActionBuilderReturnCode
@@ -4211,7 +4211,7 @@ static llvm::Optional<std::pair<llvm::StringRef, llvm::StringRef>>
 getConflictOffloadArchCombination(const llvm::DenseSet<StringRef> &Archs,
                                   Action::OffloadKind Kind) {
   if (Kind != Action::OFK_HIP)
-    return None;
+    return std::nullopt;
 
   std::set<StringRef> ArchSet;
   llvm::copy(Archs, std::inserter(ArchSet, ArchSet.begin()));
@@ -5721,7 +5721,7 @@ std::string Driver::GetFilePath(StringRef Name, const ToolChain &TC) const {
       if (llvm::sys::fs::exists(Twine(P)))
         return std::string(P);
     }
-    return None;
+    return std::nullopt;
   };
 
   if (auto P = SearchPaths(PrefixDirs))
diff --git a/clang/lib/Driver/OffloadBundler.cpp b/clang/lib/Driver/OffloadBundler.cpp
index 2aaa0179a4948c..a21deef7a30a8d 100644
--- a/clang/lib/Driver/OffloadBundler.cpp
+++ b/clang/lib/Driver/OffloadBundler.cpp
@@ -417,7 +417,7 @@ class BinaryFileHandler final : public FileHandler {
 
   Expected<Optional<StringRef>> ReadBundleStart(MemoryBuffer &Input) final {
     if (NextBundleInfo == BundlesInfo.end())
-      return None;
+      return std::nullopt;
     CurBundleInfo = NextBundleInfo++;
     return CurBundleInfo->first();
   }
@@ -545,7 +545,7 @@ class ObjectFileHandler final : public FileHandler {
 
     // If it does not start with the reserved suffix, just skip this section.
     if (!NameOrErr->startswith(OFFLOAD_BUNDLER_MAGIC_STR))
-      return None;
+      return std::nullopt;
 
     // Return the triple that is right after the reserved prefix.
     return NameOrErr->substr(sizeof(OFFLOAD_BUNDLER_MAGIC_STR) - 1);
@@ -590,7 +590,7 @@ class ObjectFileHandler final : public FileHandler {
       if (*TripleOrErr)
         return **TripleOrErr;
     }
-    return None;
+    return std::nullopt;
   }
 
   Error ReadBundleEnd(MemoryBuffer &Input) final { return Error::success(); }
@@ -739,7 +739,7 @@ class TextFileHandler final : public FileHandler {
     // Find start of the bundle.
     ReadChars = FC.find(BundleStartString, ReadChars);
     if (ReadChars == FC.npos)
-      return None;
+      return std::nullopt;
 
     // Get position of the triple.
     size_t TripleStart = ReadChars = ReadChars + BundleStartString.size();
@@ -747,7 +747,7 @@ class TextFileHandler final : public FileHandler {
     // Get position that closes the triple.
     size_t TripleEnd = ReadChars = FC.find("\n", ReadChars);
     if (TripleEnd == FC.npos)
-      return None;
+      return std::nullopt;
 
     // Next time we read after the new line.
     ++ReadChars;
diff --git a/clang/lib/Driver/ToolChains/AIX.cpp b/clang/lib/Driver/ToolChains/AIX.cpp
index 3bf97eec04a1a3..58a5103e7d9b8f 100644
--- a/clang/lib/Driver/ToolChains/AIX.cpp
+++ b/clang/lib/Driver/ToolChains/AIX.cpp
@@ -226,7 +226,7 @@ void aix::Linker::ConstructJob(Compilation &C, const JobAction &JA,
     auto ExpCommand = std::make_unique<Command>(
         JA, *this, ResponseFileSupport::None(), CreateExportListExec,
         CreateExportCmdArgs, Inputs, Output);
-    ExpCommand->setRedirectFiles({None, std::string(ExportList), None});
+    ExpCommand->setRedirectFiles({std::nullopt, std::string(ExportList), None});
     C.addCommand(std::move(ExpCommand));
     CmdArgs.push_back(Args.MakeArgString(llvm::Twine("-bE:") + ExportList));
   }
diff --git a/clang/lib/Driver/ToolChains/AMDGPU.cpp b/clang/lib/Driver/ToolChains/AMDGPU.cpp
index f8d3cab00b70cd..f3ac7d2ab73547 100644
--- a/clang/lib/Driver/ToolChains/AMDGPU.cpp
+++ b/clang/lib/Driver/ToolChains/AMDGPU.cpp
@@ -747,12 +747,12 @@ AMDGPUToolChain::ParsedTargetIDType
 AMDGPUToolChain::getParsedTargetID(const llvm::opt::ArgList &DriverArgs) const {
   StringRef TargetID = DriverArgs.getLastArgValue(options::OPT_mcpu_EQ);
   if (TargetID.empty())
-    return {None, None, None};
+    return {std::nullopt, std::nullopt, std::nullopt};
 
   llvm::StringMap<bool> FeatureMap;
   auto OptionalGpuArch = parseTargetID(getTriple(), TargetID, &FeatureMap);
   if (!OptionalGpuArch)
-    return {TargetID.str(), None, None};
+    return {TargetID.str(), std::nullopt, std::nullopt};
 
   return {TargetID.str(), OptionalGpuArch->str(), FeatureMap};
 }
diff --git a/clang/lib/Driver/ToolChains/AVR.cpp b/clang/lib/Driver/ToolChains/AVR.cpp
index 6dbe6c62bb2e80..dad8669dbe7dbc 100644
--- a/clang/lib/Driver/ToolChains/AVR.cpp
+++ b/clang/lib/Driver/ToolChains/AVR.cpp
@@ -345,14 +345,14 @@ llvm::Optional<StringRef> GetMCUFamilyName(StringRef MCUName) {
   for (const auto &MCU : MCUInfo)
     if (MCU.Name == MCUName)
       return Optional<StringRef>(MCU.Family);
-  return None;
+  return std::nullopt;
 }
 
 llvm::Optional<unsigned> GetMCUSectionAddressData(StringRef MCUName) {
   for (const auto &MCU : MCUInfo)
     if (MCU.Name == MCUName && MCU.DataAddr > 0)
       return Optional<unsigned>(MCU.DataAddr);
-  return None;
+  return std::nullopt;
 }
 
 const StringRef PossibleAVRLibcLocations[] = {
@@ -580,5 +580,5 @@ llvm::Optional<std::string> AVRToolChain::findAVRLibcInstallation() const {
       return Path;
   }
 
-  return llvm::None;
+  return std::nullopt;
 }
diff --git a/clang/lib/Driver/ToolChains/Arch/CSKY.cpp b/clang/lib/Driver/ToolChains/Arch/CSKY.cpp
index 9b432534f441f1..b6e50ee47cb3c5 100644
--- a/clang/lib/Driver/ToolChains/Arch/CSKY.cpp
+++ b/clang/lib/Driver/ToolChains/Arch/CSKY.cpp
@@ -33,7 +33,7 @@ csky::getCSKYArchName(const Driver &D, const ArgList &Args,
 
     if (ArchKind == llvm::CSKY::ArchKind::INVALID) {
       D.Diag(clang::diag::err_drv_invalid_arch_name) << A->getAsString(Args);
-      return llvm::None;
+      return std::nullopt;
     }
     return llvm::Optional<llvm::StringRef>(A->getValue());
   }
@@ -42,7 +42,7 @@ csky::getCSKYArchName(const Driver &D, const ArgList &Args,
     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::None;
+      return std::nullopt;
     }
     return llvm::Optional<llvm::StringRef>(llvm::CSKY::getArchName(ArchKind));
   }
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 6ec4172e3ebd35..867445eec0eb82 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -8161,7 +8161,7 @@ void OffloadBundler::ConstructJob(Compilation &C, const JobAction &JA,
   C.addCommand(std::make_unique<Command>(
       JA, *this, ResponseFileSupport::None(),
       TCArgs.MakeArgString(getToolChain().GetProgramPath(getShortName())),
-      CmdArgs, None, Output));
+      CmdArgs, std::nullopt, Output));
 }
 
 void OffloadBundler::ConstructJobMultipleOutputs(
@@ -8245,7 +8245,7 @@ void OffloadBundler::ConstructJobMultipleOutputs(
   C.addCommand(std::make_unique<Command>(
       JA, *this, ResponseFileSupport::None(),
       TCArgs.MakeArgString(getToolChain().GetProgramPath(getShortName())),
-      CmdArgs, None, Outputs));
+      CmdArgs, std::nullopt, Outputs));
 }
 
 void OffloadPackager::ConstructJob(Compilation &C, const JobAction &JA,
diff --git a/clang/lib/Driver/ToolChains/Darwin.cpp b/clang/lib/Driver/ToolChains/Darwin.cpp
index 050b90a344a46a..3c327c23b4fed0 100644
--- a/clang/lib/Driver/ToolChains/Darwin.cpp
+++ b/clang/lib/Driver/ToolChains/Darwin.cpp
@@ -550,8 +550,9 @@ void darwin::Linker::ConstructJob(Compilation &C, const JobAction &JA,
     const char *Exec =
         Args.MakeArgString(getToolChain().GetProgramPath("touch"));
     CmdArgs.push_back(Output.getFilename());
-    C.addCommand(std::make_unique<Command>(
-        JA, *this, ResponseFileSupport::None(), Exec, CmdArgs, None, Output));
+    C.addCommand(std::make_unique<Command>(JA, *this,
+                                           ResponseFileSupport::None(), Exec,
+                                           CmdArgs, std::nullopt, Output));
     return;
   }
 
@@ -1790,7 +1791,7 @@ getDeploymentTargetFromOSVersionArg(DerivedArgList &Args,
         Darwin::WatchOS, WatchOSVersion,
         WatchOSVersion->getOption().getID() ==
             options::OPT_mwatchos_simulator_version_min_EQ);
-  return None;
+  return std::nullopt;
 }
 
 /// Returns the deployment target that's specified using the
@@ -1845,7 +1846,7 @@ getDeploymentTargetFromEnvironmentVariables(const Driver &TheDriver,
           (Darwin::DarwinPlatformKind)Target.index(), EnvVars[Target.index()],
           Target.value());
   }
-  return None;
+  return std::nullopt;
 }
 
 /// Returns the SDK name without the optional prefix that ends with a '.' or an
@@ -1865,11 +1866,11 @@ inferDeploymentTargetFromSDK(DerivedArgList &Args,
                              const Optional<DarwinSDKInfo> &SDKInfo) {
   const Arg *A = Args.getLastArg(options::OPT_isysroot);
   if (!A)
-    return None;
+    return std::nullopt;
   StringRef isysroot = A->getValue();
   StringRef SDK = Darwin::getSDKName(isysroot);
   if (!SDK.size())
-    return None;
+    return std::nullopt;
 
   std::string Version;
   if (SDKInfo) {
@@ -1884,7 +1885,7 @@ inferDeploymentTargetFromSDK(DerivedArgList &Args,
       Version = std::string(SDK.slice(StartVer, EndVer + 1));
   }
   if (Version.empty())
-    return None;
+    return std::nullopt;
 
   auto CreatePlatformFromSDKName =
       [&](StringRef SDK) -> Optional<DarwinPlatform> {
@@ -1905,7 +1906,7 @@ inferDeploymentTargetFromSDK(DerivedArgList &Args,
           /*IsSimulator=*/SDK.startswith("AppleTVSimulator"));
     else if (SDK.startswith("DriverKit"))
       return DarwinPlatform::createFromSDK(Darwin::DriverKit, Version);
-    return None;
+    return std::nullopt;
   };
   if (auto Result = CreatePlatformFromSDKName(SDK))
     return Result;
@@ -1974,7 +1975,7 @@ inferDeploymentTargetFromArch(DerivedArgList &Args, const Darwin &Toolchain,
            MachOArchName != "armv7em")
     OSTy = llvm::Triple::MacOSX;
   if (OSTy == llvm::Triple::UnknownOS)
-    return None;
+    return std::nullopt;
   return DarwinPlatform::createFromArch(OSTy,
                                         getOSVersion(OSTy, Triple, TheDriver));
 }
@@ -1984,10 +1985,10 @@ Optional<DarwinPlatform> getDeploymentTargetFromTargetArg(
     DerivedArgList &Args, const llvm::Triple &Triple, const Driver &TheDriver,
     const Optional<DarwinSDKInfo> &SDKInfo) {
   if (!Args.hasArg(options::OPT_target))
-    return None;
+    return std::nullopt;
   if (Triple.getOS() == llvm::Triple::Darwin ||
       Triple.getOS() == llvm::Triple::UnknownOS)
-    return None;
+    return std::nullopt;
   std::string OSVersion = getOSVersion(Triple.getOS(), Triple, TheDriver);
   Optional<llvm::Triple> TargetVariantTriple;
   for (const Arg *A : Args.filtered(options::OPT_darwin_target_variant)) {
@@ -2026,7 +2027,7 @@ getDeploymentTargetFromMTargetOSArg(DerivedArgList &Args,
                                     const Optional<DarwinSDKInfo> &SDKInfo) {
   auto *A = Args.getLastArg(options::OPT_mtargetos_EQ);
   if (!A)
-    return None;
+    return std::nullopt;
   llvm::Triple TT(llvm::Twine("unknown-apple-") + A->getValue());
   switch (TT.getOS()) {
   case llvm::Triple::MacOSX:
@@ -2037,14 +2038,14 @@ getDeploymentTargetFromMTargetOSArg(DerivedArgList &Args,
   default:
     TheDriver.Diag(diag::err_drv_invalid_os_in_arg)
         << TT.getOSName() << A->getAsString(Args);
-    return None;
+    return std::nullopt;
   }
 
   VersionTuple Version = TT.getOSVersion();
   if (!Version.getMajor()) {
     TheDriver.Diag(diag::err_drv_invalid_version_number)
         << A->getAsString(Args);
-    return None;
+    return std::nullopt;
   }
   return DarwinPlatform::createFromMTargetOS(TT.getOS(), Version,
                                              TT.getEnvironment(), A, SDKInfo);
@@ -2055,13 +2056,13 @@ Optional<DarwinSDKInfo> parseSDKSettings(llvm::vfs::FileSystem &VFS,
                                          const Driver &TheDriver) {
   const Arg *A = Args.getLastArg(options::OPT_isysroot);
   if (!A)
-    return None;
+    return std::nullopt;
   StringRef isysroot = A->getValue();
   auto SDKInfoOrErr = parseDarwinSDKInfo(VFS, isysroot);
   if (!SDKInfoOrErr) {
     llvm::consumeError(SDKInfoOrErr.takeError());
     TheDriver.Diag(diag::warn_drv_darwin_sdk_invalid_settings);
-    return None;
+    return std::nullopt;
   }
   return *SDKInfoOrErr;
 }
diff --git a/clang/lib/Driver/ToolChains/HLSL.cpp b/clang/lib/Driver/ToolChains/HLSL.cpp
index 9eaf2a06c76c26..a3ad9ba24e162a 100644
--- a/clang/lib/Driver/ToolChains/HLSL.cpp
+++ b/clang/lib/Driver/ToolChains/HLSL.cpp
@@ -69,7 +69,7 @@ llvm::Optional<std::string> tryParseProfile(StringRef Profile) {
   SmallVector<StringRef, 3> Parts;
   Profile.split(Parts, "_");
   if (Parts.size() != 3)
-    return None;
+    return std::nullopt;
 
   Triple::EnvironmentType Kind =
       StringSwitch<Triple::EnvironmentType>(Parts[0])
@@ -84,17 +84,17 @@ llvm::Optional<std::string> tryParseProfile(StringRef Profile) {
           .Case("as", Triple::EnvironmentType::Amplification)
           .Default(Triple::EnvironmentType::UnknownEnvironment);
   if (Kind == Triple::EnvironmentType::UnknownEnvironment)
-    return None;
+    return std::nullopt;
 
   unsigned long long Major = 0;
   if (llvm::getAsUnsignedInteger(Parts[1], 0, Major))
-    return None;
+    return std::nullopt;
 
   unsigned long long Minor = 0;
   if (Parts[2] == "x" && Kind == Triple::EnvironmentType::Library)
     Minor = OfflineLibMinor;
   else if (llvm::getAsUnsignedInteger(Parts[2], 0, Minor))
-    return None;
+    return std::nullopt;
 
   // dxil-unknown-shadermodel-hull
   llvm::Triple T;
@@ -105,7 +105,7 @@ llvm::Optional<std::string> tryParseProfile(StringRef Profile) {
   if (isLegalShaderModel(T))
     return T.getTriple();
   else
-    return None;
+    return std::nullopt;
 }
 
 bool isLegalValidatorVersion(StringRef ValVersionStr, const Driver &D) {
diff --git a/clang/lib/Driver/ToolChains/Hexagon.cpp b/clang/lib/Driver/ToolChains/Hexagon.cpp
index 703a470b3dbf75..ba5d468a063bbd 100644
--- a/clang/lib/Driver/ToolChains/Hexagon.cpp
+++ b/clang/lib/Driver/ToolChains/Hexagon.cpp
@@ -129,7 +129,7 @@ static void handleHVXTargetFeatures(const Driver &D, const ArgList &Args,
     //   to Features.
     Arg *A = Args.getLastArg(FlagOn, FlagOff);
     if (!A)
-      return None;
+      return std::nullopt;
 
     StringRef OptName = A->getOption().getName();
     if (A->getOption().matches(FlagOff))
@@ -137,12 +137,12 @@ static void handleHVXTargetFeatures(const Driver &D, const ArgList &Args,
 
     if (!HasHVX) {
       D.Diag(diag::err_drv_needs_hvx) << withMinus(OptName);
-      return None;
+      return std::nullopt;
     }
     if (HvxVerNum < MinVerNum) {
       D.Diag(diag::err_drv_needs_hvx_version)
           << withMinus(OptName) << ("v" + std::to_string(HvxVerNum));
-      return None;
+      return std::nullopt;
     }
     return makeFeature(OptName, true);
   };
@@ -533,7 +533,7 @@ Optional<unsigned> HexagonToolChain::getSmallDataThreshold(
   if (!Gn.getAsInteger(10, G))
     return G;
 
-  return None;
+  return std::nullopt;
 }
 
 std::string HexagonToolChain::getCompilerRTPath() const {