vendor/clang/clang-trunk-r338150

18 files changed, 901 insertions, 524 deletions

diff --git a/lib/Lex/HeaderSearch.cpp b/lib/Lex/HeaderSearch.cpp
index 6976294a2eaf3..b1a2ef121288e 100644
--- a/lib/Lex/HeaderSearch.cpp
+++ b/lib/Lex/HeaderSearch.cpp
@@ -124,7 +124,7 @@ const HeaderMap *HeaderSearch::CreateHeaderMap(const FileEntry *FE) {
   return nullptr;
 }
 
-/// \brief Get filenames for all registered header maps.
+/// Get filenames for all registered header maps.
 void HeaderSearch::getHeaderMapFileNames(
     SmallVectorImpl<std::string> &Names) const {
   for (auto &HM : HeaderMaps)
@@ -198,31 +198,33 @@ std::string HeaderSearch::getCachedModuleFileName(StringRef ModuleName,
   return Result.str().str();
 }
 
-Module *HeaderSearch::lookupModule(StringRef ModuleName, bool AllowSearch) {
+Module *HeaderSearch::lookupModule(StringRef ModuleName, bool AllowSearch,
+                                   bool AllowExtraModuleMapSearch) {
   // Look in the module map to determine if there is a module by this name.
   Module *Module = ModMap.findModule(ModuleName);
   if (Module || !AllowSearch || !HSOpts->ImplicitModuleMaps)
     return Module;
 
   StringRef SearchName = ModuleName;
-  Module = lookupModule(ModuleName, SearchName);
+  Module = lookupModule(ModuleName, SearchName, AllowExtraModuleMapSearch);
 
   // The facility for "private modules" -- adjacent, optional module maps named
   // module.private.modulemap that are supposed to define private submodules --
   // may have different flavors of names: FooPrivate, Foo_Private and Foo.Private.
   //
-  // Foo.Private is now depracated in favor of Foo_Private. Users of FooPrivate
+  // Foo.Private is now deprecated in favor of Foo_Private. Users of FooPrivate
   // should also rename to Foo_Private. Representing private as submodules
   // could force building unwanted dependencies into the parent module and cause
   // dependency cycles.
   if (!Module && SearchName.consume_back("_Private"))
-    Module = lookupModule(ModuleName, SearchName);
+    Module = lookupModule(ModuleName, SearchName, AllowExtraModuleMapSearch);
   if (!Module && SearchName.consume_back("Private"))
-    Module = lookupModule(ModuleName, SearchName);
+    Module = lookupModule(ModuleName, SearchName, AllowExtraModuleMapSearch);
   return Module;
 }
 
-Module *HeaderSearch::lookupModule(StringRef ModuleName, StringRef SearchName) {
+Module *HeaderSearch::lookupModule(StringRef ModuleName, StringRef SearchName,
+                                   bool AllowExtraModuleMapSearch) {
   Module *Module = nullptr;
 
   // Look through the various header search paths to load any available module
@@ -281,8 +283,9 @@ Module *HeaderSearch::lookupModule(StringRef ModuleName, StringRef SearchName) {
       continue;
 
     // Load all module maps in the immediate subdirectories of this search
-    // directory.
-    loadSubdirectoryModuleMaps(SearchDirs[Idx]);
+    // directory if ModuleName was from @import.
+    if (AllowExtraModuleMapSearch)
+      loadSubdirectoryModuleMaps(SearchDirs[Idx]);
 
     // Look again for the module.
     Module = ModMap.findModule(ModuleName);
@@ -404,7 +407,7 @@ const FileEntry *DirectoryLookup::LookupFile(
   return Result;
 }
 
-/// \brief Given a framework directory, find the top-most framework directory.
+/// Given a framework directory, find the top-most framework directory.
 ///
 /// \param FileMgr The file manager to use for directory lookups.
 /// \param DirName The name of the framework directory.
@@ -600,7 +603,7 @@ void HeaderSearch::setTarget(const TargetInfo &Target) {
 // Header File Location.
 //===----------------------------------------------------------------------===//
 
-/// \brief Return true with a diagnostic if the file that MSVC would have found
+/// Return true with a diagnostic if the file that MSVC would have found
 /// fails to match the one that Clang would have found with MSVC header search
 /// disabled.
 static bool checkMSVCHeaderSearch(DiagnosticsEngine &Diags,
@@ -621,6 +624,74 @@ static const char *copyString(StringRef Str, llvm::BumpPtrAllocator &Alloc) {
   return CopyStr;
 }
 
+static bool isFrameworkStylePath(StringRef Path, bool &IsPrivateHeader,
+                                 SmallVectorImpl<char> &FrameworkName) {
+  using namespace llvm::sys;
+  path::const_iterator I = path::begin(Path);
+  path::const_iterator E = path::end(Path);
+  IsPrivateHeader = false;
+
+  // Detect different types of framework style paths:
+  //
+  //   ...Foo.framework/{Headers,PrivateHeaders}
+  //   ...Foo.framework/Versions/{A,Current}/{Headers,PrivateHeaders}
+  //   ...Foo.framework/Frameworks/Nested.framework/{Headers,PrivateHeaders}
+  //   ...<other variations with 'Versions' like in the above path>
+  //
+  // and some other variations among these lines.
+  int FoundComp = 0;
+  while (I != E) {
+    if (*I == "Headers")
+      ++FoundComp;
+    if (I->endswith(".framework")) {
+      FrameworkName.append(I->begin(), I->end());
+      ++FoundComp;
+    }
+    if (*I == "PrivateHeaders") {
+      ++FoundComp;
+      IsPrivateHeader = true;
+    }
+    ++I;
+  }
+
+  return FoundComp >= 2;
+}
+
+static void
+diagnoseFrameworkInclude(DiagnosticsEngine &Diags, SourceLocation IncludeLoc,
+                         StringRef Includer, StringRef IncludeFilename,
+                         const FileEntry *IncludeFE, bool isAngled = false,
+                         bool FoundByHeaderMap = false) {
+  bool IsIncluderPrivateHeader = false;
+  SmallString<128> FromFramework, ToFramework;
+  if (!isFrameworkStylePath(Includer, IsIncluderPrivateHeader, FromFramework))
+    return;
+  bool IsIncludeePrivateHeader = false;
+  bool IsIncludeeInFramework = isFrameworkStylePath(
+      IncludeFE->getName(), IsIncludeePrivateHeader, ToFramework);
+
+  if (!isAngled && !FoundByHeaderMap) {
+    SmallString<128> NewInclude("<");
+    if (IsIncludeeInFramework) {
+      NewInclude += StringRef(ToFramework).drop_back(10); // drop .framework
+      NewInclude += "/";
+    }
+    NewInclude += IncludeFilename;
+    NewInclude += ">";
+    Diags.Report(IncludeLoc, diag::warn_quoted_include_in_framework_header)
+        << IncludeFilename
+        << FixItHint::CreateReplacement(IncludeLoc, NewInclude);
+  }
+
+  // Headers in Foo.framework/Headers should not include headers
+  // from Foo.framework/PrivateHeaders, since this violates public/private
+  // API boundaries and can cause modular dependency cycles.
+  if (!IsIncluderPrivateHeader && IsIncludeeInFramework &&
+      IsIncludeePrivateHeader && FromFramework == ToFramework)
+    Diags.Report(IncludeLoc, diag::warn_framework_include_private_from_public)
+        << IncludeFilename;
+}
+
 /// LookupFile - Given a "foo" or \<foo> reference, look up the indicated file,
 /// return null on failure.  isAngled indicates whether the file reference is
 /// for system \#include's or not (i.e. using <> instead of ""). Includers, if
@@ -722,8 +793,12 @@ const FileEntry *HeaderSearch::LookupFile(
           RelativePath->clear();
           RelativePath->append(Filename.begin(), Filename.end());
         }
-        if (First)
+        if (First) {
+          diagnoseFrameworkInclude(Diags, IncludeLoc,
+                                   IncluderAndDir.second->getName(), Filename,
+                                   FE);
           return FE;
+        }
 
         // Otherwise, we found the path via MSVC header search rules.  If
         // -Wmsvc-include is enabled, we have to keep searching to see if we
@@ -834,6 +909,12 @@ const FileEntry *HeaderSearch::LookupFile(
       return MSFE;
     }
 
+    bool FoundByHeaderMap = !IsMapped ? false : *IsMapped;
+    if (!Includers.empty())
+      diagnoseFrameworkInclude(Diags, IncludeLoc,
+                               Includers.front().second->getName(), Filename,
+                               FE, isAngled, FoundByHeaderMap);
+
     // Remember this location for the next lookup we do.
     CacheLookup.HitIdx = i;
     return FE;
@@ -996,7 +1077,7 @@ LookupSubframeworkHeader(StringRef Filename,
 // File Info Management.
 //===----------------------------------------------------------------------===//
 
-/// \brief Merge the header file info provided by \p OtherHFI into the current
+/// Merge the header file info provided by \p OtherHFI into the current
 /// header file info (\p HFI)
 static void mergeHeaderFileInfo(HeaderFileInfo &HFI, 
                                 const HeaderFileInfo &OtherHFI) {
@@ -1580,9 +1661,15 @@ void HeaderSearch::loadSubdirectoryModuleMaps(DirectoryLookup &SearchDir) {
 std::string HeaderSearch::suggestPathToFileForDiagnostics(const FileEntry *File,
                                                           bool *IsSystem) {
   // FIXME: We assume that the path name currently cached in the FileEntry is
-  // the most appropriate one for this analysis (and that it's spelled the same
-  // way as the corresponding header search path).
-  StringRef Name = File->getName();
+  // the most appropriate one for this analysis (and that it's spelled the
+  // same way as the corresponding header search path).
+  return suggestPathToFileForDiagnostics(File->getName(), /*BuildDir=*/"",
+                                         IsSystem);
+}
+
+std::string HeaderSearch::suggestPathToFileForDiagnostics(
+    llvm::StringRef File, llvm::StringRef WorkingDir, bool *IsSystem) {
+  using namespace llvm::sys;
 
   unsigned BestPrefixLength = 0;
   unsigned BestSearchDir;
@@ -1593,12 +1680,17 @@ std::string HeaderSearch::suggestPathToFileForDiagnostics(const FileEntry *File,
       continue;
 
     StringRef Dir = SearchDirs[I].getDir()->getName();
-    for (auto NI = llvm::sys::path::begin(Name),
-              NE = llvm::sys::path::end(Name),
-              DI = llvm::sys::path::begin(Dir),
-              DE = llvm::sys::path::end(Dir);
+    llvm::SmallString<32> DirPath(Dir.begin(), Dir.end());
+    if (!WorkingDir.empty() && !path::is_absolute(Dir)) {
+      auto err = fs::make_absolute(WorkingDir, DirPath);
+      if (!err)
+        path::remove_dots(DirPath, /*remove_dot_dot=*/true);
+      Dir = DirPath;
+    }
+    for (auto NI = path::begin(File), NE = path::end(File),
+              DI = path::begin(Dir), DE = path::end(Dir);
          /*termination condition in loop*/; ++NI, ++DI) {
-      // '.' components in Name are ignored.
+      // '.' components in File are ignored.
       while (NI != NE && *NI == ".")
         ++NI;
       if (NI == NE)
@@ -1608,9 +1700,9 @@ std::string HeaderSearch::suggestPathToFileForDiagnostics(const FileEntry *File,
       while (DI != DE && *DI == ".")
         ++DI;
       if (DI == DE) {
-        // Dir is a prefix of Name, up to '.' components and choice of path
+        // Dir is a prefix of File, up to '.' components and choice of path
         // separators.
-        unsigned PrefixLength = NI - llvm::sys::path::begin(Name);
+        unsigned PrefixLength = NI - path::begin(File);
         if (PrefixLength > BestPrefixLength) {
           BestPrefixLength = PrefixLength;
           BestSearchDir = I;
@@ -1625,5 +1717,5 @@ std::string HeaderSearch::suggestPathToFileForDiagnostics(const FileEntry *File,
 
   if (IsSystem)
     *IsSystem = BestPrefixLength ? BestSearchDir >= SystemDirIdx : false;
-  return Name.drop_front(BestPrefixLength);
+  return File.drop_front(BestPrefixLength);
 }
diff --git a/lib/Lex/Lexer.cpp b/lib/Lex/Lexer.cpp
index 830354ab23f0d..e8588a771a431 100644
--- a/lib/Lex/Lexer.cpp
+++ b/lib/Lex/Lexer.cpp
@@ -257,7 +257,7 @@ void Lexer::Stringify(SmallVectorImpl<char> &Str) { StringifyImpl(Str, '"'); }
 // Token Spelling
 //===----------------------------------------------------------------------===//
 
-/// \brief Slow case of getSpelling. Extract the characters comprising the
+/// Slow case of getSpelling. Extract the characters comprising the
 /// spelling of this token from the provided input buffer.
 static size_t getSpellingSlow(const Token &Tok, const char *BufPtr,
                               const LangOptions &LangOpts, char *Spelling) {
@@ -442,7 +442,7 @@ unsigned Lexer::MeasureTokenLength(SourceLocation Loc,
   return TheTok.getLength();
 }
 
-/// \brief Relex the token at the specified location.
+/// Relex the token at the specified location.
 /// \returns true if there was a failure, false on success.
 bool Lexer::getRawToken(SourceLocation Loc, Token &Result,
                         const SourceManager &SM,
@@ -708,12 +708,9 @@ PreambleBounds Lexer::ComputePreamble(StringRef Buffer,
                         TheTok.isAtStartOfLine());
 }
 
-/// AdvanceToTokenCharacter - Given a location that specifies the start of a
-/// token, return a new location that specifies a character within the token.
-SourceLocation Lexer::AdvanceToTokenCharacter(SourceLocation TokStart,
-                                              unsigned CharNo,
-                                              const SourceManager &SM,
-                                              const LangOptions &LangOpts) {
+unsigned Lexer::getTokenPrefixLength(SourceLocation TokStart, unsigned CharNo,
+                                     const SourceManager &SM,
+                                     const LangOptions &LangOpts) {
   // Figure out how many physical characters away the specified expansion
   // character is.  This needs to take into consideration newlines and
   // trigraphs.
@@ -722,7 +719,7 @@ SourceLocation Lexer::AdvanceToTokenCharacter(SourceLocation TokStart,
 
   // If they request the first char of the token, we're trivially done.
   if (Invalid || (CharNo == 0 && Lexer::isObviouslySimpleCharacter(*TokPtr)))
-    return TokStart;
+    return 0;
 
   unsigned PhysOffset = 0;
 
@@ -731,7 +728,7 @@ SourceLocation Lexer::AdvanceToTokenCharacter(SourceLocation TokStart,
   // chars, this method is extremely fast.
   while (Lexer::isObviouslySimpleCharacter(*TokPtr)) {
     if (CharNo == 0)
-      return TokStart.getLocWithOffset(PhysOffset);
+      return PhysOffset;
     ++TokPtr;
     --CharNo;
     ++PhysOffset;
@@ -753,10 +750,10 @@ SourceLocation Lexer::AdvanceToTokenCharacter(SourceLocation TokStart,
   if (!Lexer::isObviouslySimpleCharacter(*TokPtr))
     PhysOffset += Lexer::SkipEscapedNewLines(TokPtr)-TokPtr;
 
-  return TokStart.getLocWithOffset(PhysOffset);
+  return PhysOffset;
 }
 
-/// \brief Computes the source location just past the end of the
+/// Computes the source location just past the end of the
 /// token at this source location.
 ///
 /// This routine can be used to produce a source location that
@@ -791,7 +788,7 @@ SourceLocation Lexer::getLocForEndOfToken(SourceLocation Loc, unsigned Offset,
   return Loc.getLocWithOffset(Len);
 }
 
-/// \brief Returns true if the given MacroID location points at the first
+/// Returns true if the given MacroID location points at the first
 /// token of the macro expansion.
 bool Lexer::isAtStartOfMacroExpansion(SourceLocation loc,
                                       const SourceManager &SM,
@@ -813,7 +810,7 @@ bool Lexer::isAtStartOfMacroExpansion(SourceLocation loc,
   return isAtStartOfMacroExpansion(expansionLoc, SM, LangOpts, MacroBegin);
 }
 
-/// \brief Returns true if the given MacroID location points at the last
+/// Returns true if the given MacroID location points at the last
 /// token of the macro expansion.
 bool Lexer::isAtEndOfMacroExpansion(SourceLocation loc,
                                     const SourceManager &SM,
@@ -971,7 +968,7 @@ StringRef Lexer::getSourceText(CharSourceRange Range,
 StringRef Lexer::getImmediateMacroName(SourceLocation Loc,
                                        const SourceManager &SM,
                                        const LangOptions &LangOpts) {
-  assert(Loc.isMacroID() && "Only reasonble to call this on macros");
+  assert(Loc.isMacroID() && "Only reasonable to call this on macros");
 
   // Find the location of the immediate macro expansion.
   while (true) {
@@ -987,7 +984,7 @@ StringRef Lexer::getImmediateMacroName(SourceLocation Loc,
 
     // Loc points to the argument id of the macro definition, move to the
     // macro expansion.
-    Loc = SM.getImmediateExpansionRange(Loc).first;
+    Loc = SM.getImmediateExpansionRange(Loc).getBegin();
     SourceLocation SpellLoc = Expansion.getSpellingLoc();
     if (SpellLoc.isFileID())
       break; // No inner macro.
@@ -1017,10 +1014,10 @@ StringRef Lexer::getImmediateMacroName(SourceLocation Loc,
 
 StringRef Lexer::getImmediateMacroNameForDiagnostics(
     SourceLocation Loc, const SourceManager &SM, const LangOptions &LangOpts) {
-  assert(Loc.isMacroID() && "Only reasonble to call this on macros");
+  assert(Loc.isMacroID() && "Only reasonable to call this on macros");
   // Walk past macro argument expanions.
   while (SM.isMacroArgExpansion(Loc))
-    Loc = SM.getImmediateExpansionRange(Loc).first;
+    Loc = SM.getImmediateExpansionRange(Loc).getBegin();
 
   // If the macro's spelling has no FileID, then it's actually a token paste
   // or stringization (or similar) and not a macro at all.
@@ -1030,7 +1027,7 @@ StringRef Lexer::getImmediateMacroNameForDiagnostics(
   // Find the spelling location of the start of the non-argument expansion
   // range. This is where the macro name was spelled in order to begin
   // expanding this macro.
-  Loc = SM.getSpellingLoc(SM.getImmediateExpansionRange(Loc).first);
+  Loc = SM.getSpellingLoc(SM.getImmediateExpansionRange(Loc).getBegin());
 
   // Dig out the buffer where the macro name was spelled and the extents of the
   // name so that we can render it into the expansion note.
@@ -1112,10 +1109,9 @@ static SourceLocation GetMappedTokenLoc(Preprocessor &PP,
 
   // Figure out the expansion loc range, which is the range covered by the
   // original _Pragma(...) sequence.
-  std::pair<SourceLocation,SourceLocation> II =
-    SM.getImmediateExpansionRange(FileLoc);
+  CharSourceRange II = SM.getImmediateExpansionRange(FileLoc);
 
-  return SM.createExpansionLoc(SpellingLoc, II.first, II.second, TokLen);
+  return SM.createExpansionLoc(SpellingLoc, II.getBegin(), II.getEnd(), TokLen);
 }
 
 /// getSourceLocation - Return a source location identifier for the specified
@@ -1260,7 +1256,7 @@ Optional<Token> Lexer::findNextToken(SourceLocation Loc,
   return Tok;
 }
 
-/// \brief Checks that the given token is the first token that occurs after the
+/// Checks that the given token is the first token that occurs after the
 /// given location (this excludes comments and whitespace). Returns the location
 /// immediately after the specified token. If the token is not found or the
 /// location is inside a macro, the returned source location will be invalid.
@@ -1413,7 +1409,7 @@ Slash:
 // Helper methods for lexing.
 //===----------------------------------------------------------------------===//
 
-/// \brief Routine that indiscriminately sets the offset into the source file.
+/// Routine that indiscriminately sets the offset into the source file.
 void Lexer::SetByteOffset(unsigned Offset, bool StartOfLine) {
   BufferPtr = BufferStart + Offset;
   if (BufferPtr > BufferEnd)
@@ -1645,20 +1641,38 @@ FinishIdentifier:
     // Fill in Result.IdentifierInfo and update the token kind,
     // looking up the identifier in the identifier table.
     IdentifierInfo *II = PP->LookUpIdentifierInfo(Result);
+    // Note that we have to call PP->LookUpIdentifierInfo() even for code
+    // completion, it writes IdentifierInfo into Result, and callers rely on it.
+
+    // If the completion point is at the end of an identifier, we want to treat
+    // the identifier as incomplete even if it resolves to a macro or a keyword.
+    // This allows e.g. 'class^' to complete to 'classifier'.
+    if (isCodeCompletionPoint(CurPtr)) {
+      // Return the code-completion token.
+      Result.setKind(tok::code_completion);
+      // Skip the code-completion char and all immediate identifier characters.
+      // This ensures we get consistent behavior when completing at any point in
+      // an identifier (i.e. at the start, in the middle, at the end). Note that
+      // only simple cases (i.e. [a-zA-Z0-9_]) are supported to keep the code
+      // simpler.
+      assert(*CurPtr == 0 && "Completion character must be 0");
+      ++CurPtr;
+      // Note that code completion token is not added as a separate character
+      // when the completion point is at the end of the buffer. Therefore, we need
+      // to check if the buffer has ended.
+      if (CurPtr < BufferEnd) {
+        while (isIdentifierBody(*CurPtr))
+          ++CurPtr;
+      }
+      BufferPtr = CurPtr;
+      return true;
+    }
 
     // Finally, now that we know we have an identifier, pass this off to the
     // preprocessor, which may macro expand it or something.
     if (II->isHandleIdentifierCase())
       return PP->HandleIdentifier(Result);
 
-    if (II->getTokenID() == tok::identifier && isCodeCompletionPoint(CurPtr)
-        && II->getPPKeywordID() == tok::pp_not_keyword
-        && II->getObjCKeywordID() == tok::objc_not_keyword) {
-      // Return the code-completion token.
-      Result.setKind(tok::code_completion);
-      cutOffLexing();
-      return true;
-    }
     return true;
   }
 
@@ -2009,18 +2023,21 @@ bool Lexer::LexAngledStringLiteral(Token &Result, const char *CurPtr) {
   const char *AfterLessPos = CurPtr;
   char C = getAndAdvanceChar(CurPtr, Result);
   while (C != '>') {
-    // Skip escaped characters.
-    if (C == '\\' && CurPtr < BufferEnd) {
-      // Skip the escaped character.
-      getAndAdvanceChar(CurPtr, Result);
-    } else if (C == '\n' || C == '\r' ||             // Newline.
-               (C == 0 && (CurPtr-1 == BufferEnd ||  // End of file.
-                           isCodeCompletionPoint(CurPtr-1)))) {
+    // Skip escaped characters.  Escaped newlines will already be processed by
+    // getAndAdvanceChar.
+    if (C == '\\')
+      C = getAndAdvanceChar(CurPtr, Result);
+
+    if (C == '\n' || C == '\r' ||             // Newline.
+        (C == 0 && (CurPtr-1 == BufferEnd ||  // End of file.
+                    isCodeCompletionPoint(CurPtr-1)))) {
       // If the filename is unterminated, then it must just be a lone <
       // character.  Return this as such.
       FormTokenWithChars(Result, AfterLessPos, tok::less);
       return true;
-    } else if (C == 0) {
+    }
+
+    if (C == 0) {
       NulCharacter = CurPtr-1;
     }
     C = getAndAdvanceChar(CurPtr, Result);
@@ -2160,7 +2177,7 @@ bool Lexer::SkipWhitespace(Token &Result, const char *CurPtr,
 }
 
 /// We have just read the // characters from input.  Skip until we find the
-/// newline character thats terminate the comment.  Then update BufferPtr and
+/// newline character that terminates the comment.  Then update BufferPtr and
 /// return.
 ///
 /// If we're in KeepCommentMode or any CommentHandler has inserted
@@ -2738,7 +2755,7 @@ unsigned Lexer::isNextPPTokenLParen() {
   return Tok.is(tok::l_paren);
 }
 
-/// \brief Find the end of a version control conflict marker.
+/// Find the end of a version control conflict marker.
 static const char *FindConflictEnd(const char *CurPtr, const char *BufferEnd,
                                    ConflictMarkerKind CMK) {
   const char *Terminator = CMK == CMK_Perforce ? "<<<<\n" : ">>>>>>>";
@@ -3509,7 +3526,7 @@ LexNextToken:
       // want to lex this as a comment.  There is one problem with this though,
       // that in one particular corner case, this can change the behavior of the
       // resultant program.  For example, In  "foo //**/ bar", C89 would lex
-      // this as "foo / bar" and langauges with Line comments would lex it as
+      // this as "foo / bar" and languages with Line comments would lex it as
       // "foo".  Check to see if the character after the second slash is a '*'.
       // If so, we will lex that as a "/" instead of the start of a comment.
       // However, we never do this if we are just preprocessing.
diff --git a/lib/Lex/LiteralSupport.cpp b/lib/Lex/LiteralSupport.cpp
index cbec5e6b63856..966dafca27197 100644
--- a/lib/Lex/LiteralSupport.cpp
+++ b/lib/Lex/LiteralSupport.cpp
@@ -70,7 +70,7 @@ static CharSourceRange MakeCharSourceRange(const LangOptions &Features,
   return CharSourceRange::getCharRange(Begin, End);
 }
 
-/// \brief Produce a diagnostic highlighting some portion of a literal.
+/// Produce a diagnostic highlighting some portion of a literal.
 ///
 /// Emits the diagnostic \p DiagID, highlighting the range of characters from
 /// \p TokRangeBegin (inclusive) to \p TokRangeEnd (exclusive), which must be
@@ -538,6 +538,7 @@ NumericLiteralParser::NumericLiteralParser(StringRef TokSpelling,
   saw_exponent = false;
   saw_period = false;
   saw_ud_suffix = false;
+  saw_fixed_point_suffix = false;
   isLong = false;
   isUnsigned = false;
   isLongLong = false;
@@ -547,6 +548,8 @@ NumericLiteralParser::NumericLiteralParser(StringRef TokSpelling,
   isFloat16 = false;
   isFloat128 = false;
   MicrosoftInteger = 0;
+  isFract = false;
+  isAccum = false;
   hadError = false;
 
   if (*s == '0') { // parse radix
@@ -568,6 +571,16 @@ NumericLiteralParser::NumericLiteralParser(StringRef TokSpelling,
   SuffixBegin = s;
   checkSeparator(TokLoc, s, CSK_AfterDigits);
 
+  // Initial scan to lookahead for fixed point suffix.
+  if (PP.getLangOpts().FixedPoint) {
+    for (const char *c = s; c != ThisTokEnd; ++c) {
+      if (*c == 'r' || *c == 'k' || *c == 'R' || *c == 'K') {
+        saw_fixed_point_suffix = true;
+        break;
+      }
+    }
+  }
+
   // Parse the suffix.  At this point we can classify whether we have an FP or
   // integer constant.
   bool isFPConstant = isFloatingLiteral();
@@ -576,11 +589,25 @@ NumericLiteralParser::NumericLiteralParser(StringRef TokSpelling,
   // we break out of the loop.
   for (; s != ThisTokEnd; ++s) {
     switch (*s) {
+    case 'R':
+    case 'r':
+      if (!PP.getLangOpts().FixedPoint) break;
+      if (isFract || isAccum) break;
+      if (!(saw_period || saw_exponent)) break;
+      isFract = true;
+      continue;
+    case 'K':
+    case 'k':
+      if (!PP.getLangOpts().FixedPoint) break;
+      if (isFract || isAccum) break;
+      if (!(saw_period || saw_exponent)) break;
+      isAccum = true;
+      continue;
     case 'h':      // FP Suffix for "half".
     case 'H':
       // OpenCL Extension v1.2 s9.5 - h or H suffix for half type.
-      if (!PP.getLangOpts().Half) break;
-      if (!isFPConstant) break;  // Error for integer constant.
+      if (!(PP.getLangOpts().Half || PP.getLangOpts().FixedPoint)) break;
+      if (isIntegerLiteral()) break;  // Error for integer constant.
       if (isHalf || isFloat || isLong) break; // HH, FH, LH invalid.
       isHalf = true;
       continue;  // Success.
@@ -693,6 +720,9 @@ NumericLiteralParser::NumericLiteralParser(StringRef TokSpelling,
         isHalf = false;
         isImaginary = false;
         MicrosoftInteger = 0;
+        saw_fixed_point_suffix = false;
+        isFract = false;
+        isAccum = false;
       }
 
       saw_ud_suffix = true;
@@ -707,6 +737,10 @@ NumericLiteralParser::NumericLiteralParser(StringRef TokSpelling,
       hadError = true;
     }
   }
+
+  if (!hadError && saw_fixed_point_suffix) {
+    assert(isFract || isAccum);
+  }
 }
 
 /// ParseDecimalOrOctalCommon - This method is called for decimal or octal
@@ -717,7 +751,8 @@ void NumericLiteralParser::ParseDecimalOrOctalCommon(SourceLocation TokLoc){
 
   // If we have a hex digit other than 'e' (which denotes a FP exponent) then
   // the code is using an incorrect base.
-  if (isHexDigit(*s) && *s != 'e' && *s != 'E') {
+  if (isHexDigit(*s) && *s != 'e' && *s != 'E' &&
+      !isValidUDSuffix(PP.getLangOpts(), StringRef(s, ThisTokEnd - s))) {
     PP.Diag(PP.AdvanceToTokenCharacter(TokLoc, s-ThisTokBegin),
             diag::err_invalid_digit) << StringRef(s, 1) << (radix == 8 ? 1 : 0);
     hadError = true;
@@ -738,15 +773,17 @@ void NumericLiteralParser::ParseDecimalOrOctalCommon(SourceLocation TokLoc){
     s++;
     radix = 10;
     saw_exponent = true;
-    if (*s == '+' || *s == '-')  s++; // sign
+    if (s != ThisTokEnd && (*s == '+' || *s == '-'))  s++; // sign
     const char *first_non_digit = SkipDigits(s);
     if (containsDigits(s, first_non_digit)) {
       checkSeparator(TokLoc, s, CSK_BeforeDigits);
       s = first_non_digit;
     } else {
-      PP.Diag(PP.AdvanceToTokenCharacter(TokLoc, Exponent-ThisTokBegin),
-              diag::err_exponent_has_no_digits);
-      hadError = true;
+      if (!hadError) {
+        PP.Diag(PP.AdvanceToTokenCharacter(TokLoc, Exponent-ThisTokBegin),
+                diag::err_exponent_has_no_digits);
+        hadError = true;
+      }
       return;
     }
   }
@@ -768,12 +805,14 @@ bool NumericLiteralParser::isValidUDSuffix(const LangOptions &LangOpts,
   if (!LangOpts.CPlusPlus14)
     return false;
 
-  // In C++1y, "s", "h", "min", "ms", "us", and "ns" are used in the library.
+  // In C++14, "s", "h", "min", "ms", "us", and "ns" are used in the library.
   // Per tweaked N3660, "il", "i", and "if" are also used in the library.
+  // In C++2a "d" and "y" are used in the library.
   return llvm::StringSwitch<bool>(Suffix)
       .Cases("h", "min", "s", true)
       .Cases("ms", "us", "ns", true)
       .Cases("il", "i", "if", true)
+      .Cases("d", "y", LangOpts.CPlusPlus2a)
       .Default(false);
 }
 
@@ -787,10 +826,12 @@ void NumericLiteralParser::checkSeparator(SourceLocation TokLoc,
   } else if (Pos == ThisTokEnd)
     return;
 
-  if (isDigitSeparator(*Pos))
+  if (isDigitSeparator(*Pos)) {
     PP.Diag(PP.AdvanceToTokenCharacter(TokLoc, Pos - ThisTokBegin),
             diag::err_digit_separator_not_between_digits)
       << IsAfterDigits;
+    hadError = true;
+  }
 }
 
 /// ParseNumberStartingWithZero - This method is called when the first character
@@ -840,12 +881,14 @@ void NumericLiteralParser::ParseNumberStartingWithZero(SourceLocation TokLoc) {
       const char *Exponent = s;
       s++;
       saw_exponent = true;
-      if (*s == '+' || *s == '-')  s++; // sign
+      if (s != ThisTokEnd && (*s == '+' || *s == '-'))  s++; // sign
       const char *first_non_digit = SkipDigits(s);
       if (!containsDigits(s, first_non_digit)) {
-        PP.Diag(PP.AdvanceToTokenCharacter(TokLoc, Exponent-ThisTokBegin),
-                diag::err_exponent_has_no_digits);
-        hadError = true;
+        if (!hadError) {
+          PP.Diag(PP.AdvanceToTokenCharacter(TokLoc, Exponent-ThisTokBegin),
+                  diag::err_exponent_has_no_digits);
+          hadError = true;
+        }
         return;
       }
       checkSeparator(TokLoc, s, CSK_BeforeDigits);
@@ -882,7 +925,9 @@ void NumericLiteralParser::ParseNumberStartingWithZero(SourceLocation TokLoc) {
     s = SkipBinaryDigits(s);
     if (s == ThisTokEnd) {
       // Done.
-    } else if (isHexDigit(*s)) {
+    } else if (isHexDigit(*s) &&
+               !isValidUDSuffix(PP.getLangOpts(),
+                                StringRef(s, ThisTokEnd - s))) {
       PP.Diag(PP.AdvanceToTokenCharacter(TokLoc, s-ThisTokBegin),
               diag::err_invalid_digit) << StringRef(s, 1) << 2;
       hadError = true;
@@ -1006,6 +1051,126 @@ NumericLiteralParser::GetFloatValue(llvm::APFloat &Result) {
   return Result.convertFromString(Str, APFloat::rmNearestTiesToEven);
 }
 
+static inline bool IsExponentPart(char c) {
+  return c == 'p' || c == 'P' || c == 'e' || c == 'E';
+}
+
+bool NumericLiteralParser::GetFixedPointValue(llvm::APInt &StoreVal, unsigned Scale) {
+  assert(radix == 16 || radix == 10);
+
+  // Find how many digits are needed to store the whole literal.
+  unsigned NumDigits = SuffixBegin - DigitsBegin;
+  if (saw_period) --NumDigits;
+
+  // Initial scan of the exponent if it exists
+  bool ExpOverflowOccurred = false;
+  bool NegativeExponent = false;
+  const char *ExponentBegin;
+  uint64_t Exponent = 0;
+  int64_t BaseShift = 0;
+  if (saw_exponent) {
+    const char *Ptr = DigitsBegin;
+
+    while (!IsExponentPart(*Ptr)) ++Ptr;
+    ExponentBegin = Ptr;
+    ++Ptr;
+    NegativeExponent = *Ptr == '-';
+    if (NegativeExponent) ++Ptr;
+
+    unsigned NumExpDigits = SuffixBegin - Ptr;
+    if (alwaysFitsInto64Bits(radix, NumExpDigits)) {
+      llvm::StringRef ExpStr(Ptr, NumExpDigits);
+      llvm::APInt ExpInt(/*numBits=*/64, ExpStr, /*radix=*/10);
+      Exponent = ExpInt.getZExtValue();
+    } else {
+      ExpOverflowOccurred = true;
+    }
+
+    if (NegativeExponent) BaseShift -= Exponent;
+    else BaseShift += Exponent;
+  }
+
+  // Number of bits needed for decimal literal is
+  //   ceil(NumDigits * log2(10))       Integral part
+  // + Scale                            Fractional part
+  // + ceil(Exponent * log2(10))        Exponent
+  // --------------------------------------------------
+  //   ceil((NumDigits + Exponent) * log2(10)) + Scale
+  //
+  // But for simplicity in handling integers, we can round up log2(10) to 4,
+  // making:
+  // 4 * (NumDigits + Exponent) + Scale
+  //
+  // Number of digits needed for hexadecimal literal is
+  //   4 * NumDigits                    Integral part
+  // + Scale                            Fractional part
+  // + Exponent                         Exponent
+  // --------------------------------------------------
+  //   (4 * NumDigits) + Scale + Exponent
+  uint64_t NumBitsNeeded;
+  if (radix == 10)
+    NumBitsNeeded = 4 * (NumDigits + Exponent) + Scale;
+  else
+    NumBitsNeeded = 4 * NumDigits + Exponent + Scale;
+
+  if (NumBitsNeeded > std::numeric_limits<unsigned>::max())
+    ExpOverflowOccurred = true;
+  llvm::APInt Val(static_cast<unsigned>(NumBitsNeeded), 0, /*isSigned=*/false);
+
+  bool FoundDecimal = false;
+
+  int64_t FractBaseShift = 0;
+  const char *End = saw_exponent ? ExponentBegin : SuffixBegin;
+  for (const char *Ptr = DigitsBegin; Ptr < End; ++Ptr) {
+    if (*Ptr == '.') {
+      FoundDecimal = true;
+      continue;
+    }
+
+    // Normal reading of an integer
+    unsigned C = llvm::hexDigitValue(*Ptr);
+    assert(C < radix && "NumericLiteralParser ctor should have rejected this");
+
+    Val *= radix;
+    Val += C;
+
+    if (FoundDecimal)
+      // Keep track of how much we will need to adjust this value by from the
+      // number of digits past the radix point.
+      --FractBaseShift;
+  }
+
+  // For a radix of 16, we will be multiplying by 2 instead of 16.
+  if (radix == 16) FractBaseShift *= 4;
+  BaseShift += FractBaseShift;
+
+  Val <<= Scale;
+
+  uint64_t Base = (radix == 16) ? 2 : 10;
+  if (BaseShift > 0) {
+    for (int64_t i = 0; i < BaseShift; ++i) {
+      Val *= Base;
+    }
+  } else if (BaseShift < 0) {
+    for (int64_t i = BaseShift; i < 0 && !Val.isNullValue(); ++i)
+      Val = Val.udiv(Base);
+  }
+
+  bool IntOverflowOccurred = false;
+  auto MaxVal = llvm::APInt::getMaxValue(StoreVal.getBitWidth());
+  if (Val.getBitWidth() > StoreVal.getBitWidth()) {
+    IntOverflowOccurred |= Val.ugt(MaxVal.zext(Val.getBitWidth()));
+    StoreVal = Val.trunc(StoreVal.getBitWidth());
+  } else if (Val.getBitWidth() < StoreVal.getBitWidth()) {
+    IntOverflowOccurred |= Val.zext(MaxVal.getBitWidth()).ugt(MaxVal);
+    StoreVal = Val.zext(StoreVal.getBitWidth());
+  } else {
+    StoreVal = Val;
+  }
+
+  return IntOverflowOccurred || ExpOverflowOccurred;
+}
+
 /// \verbatim
 ///       user-defined-character-literal: [C++11 lex.ext]
 ///         character-literal ud-suffix
@@ -1585,7 +1750,7 @@ static const char *resyncUTF8(const char *Err, const char *End) {
   return Err;
 }
 
-/// \brief This function copies from Fragment, which is a sequence of bytes
+/// This function copies from Fragment, which is a sequence of bytes
 /// within Tok's contents (which begin at TokBegin) into ResultPtr.
 /// Performs widening for multi-byte characters.
 bool StringLiteralParser::CopyStringFragment(const Token &Tok,
diff --git a/lib/Lex/MacroArgs.cpp b/lib/Lex/MacroArgs.cpp
index 5c0f0623c3e17..3b6e2dc2411a0 100644
--- a/lib/Lex/MacroArgs.cpp
+++ b/lib/Lex/MacroArgs.cpp
@@ -49,7 +49,8 @@ MacroArgs *MacroArgs::create(const MacroInfo *MI,
   if (!ResultEnt) {
     // Allocate memory for a MacroArgs object with the lexer tokens at the end,
     // and construct the MacroArgs object.
-    Result = new (std::malloc(totalSizeToAlloc<Token>(UnexpArgTokens.size())))
+    Result = new (
+        llvm::safe_malloc(totalSizeToAlloc<Token>(UnexpArgTokens.size())))
         MacroArgs(UnexpArgTokens.size(), VarargsElided, MI->getNumParams());
   } else {
     Result = *ResultEnt;
@@ -272,7 +273,7 @@ Token MacroArgs::StringifyArgument(const Token *ArgToks,
   // If the last character of the string is a \, and if it isn't escaped, this
   // is an invalid string literal, diagnose it as specified in C99.
   if (Result.back() == '\\') {
-    // Count the number of consequtive \ characters.  If even, then they are
+    // Count the number of consecutive \ characters.  If even, then they are
     // just escaped backslashes, otherwise it's an error.
     unsigned FirstNonSlash = Result.size()-2;
     // Guaranteed to find the starting " if nothing else.
diff --git a/lib/Lex/MacroInfo.cpp b/lib/Lex/MacroInfo.cpp
index b13767aa1d673..4ed69ecc465db 100644
--- a/lib/Lex/MacroInfo.cpp
+++ b/lib/Lex/MacroInfo.cpp
@@ -65,7 +65,7 @@ unsigned MacroInfo::getDefinitionLengthSlow(const SourceManager &SM) const {
   return DefinitionLength;
 }
 
-/// \brief Return true if the specified macro definition is equal to
+/// Return true if the specified macro definition is equal to
 /// this macro in spelling, arguments, and whitespace.
 ///
 /// \param Syntactically if true, the macro definitions can be identical even
diff --git a/lib/Lex/ModuleMap.cpp b/lib/Lex/ModuleMap.cpp
index b3ac10c5c5ae8..f048a73a8ccc2 100644
--- a/lib/Lex/ModuleMap.cpp
+++ b/lib/Lex/ModuleMap.cpp
@@ -54,6 +54,24 @@
 
 using namespace clang;
 
+void ModuleMap::resolveLinkAsDependencies(Module *Mod) {
+  auto PendingLinkAs = PendingLinkAsModule.find(Mod->Name);
+  if (PendingLinkAs != PendingLinkAsModule.end()) {
+    for (auto &Name : PendingLinkAs->second) {
+      auto *M = findModule(Name.getKey());
+      if (M)
+        M->UseExportAsModuleLinkName = true;
+    }
+  }
+}
+
+void ModuleMap::addLinkAsDependency(Module *Mod) {
+  if (findModule(Mod->ExportAsModule))
+    Mod->UseExportAsModuleLinkName = true;
+  else
+    PendingLinkAsModule[Mod->ExportAsModule].insert(Mod->Name);
+}
+
 Module::HeaderKind ModuleMap::headerRoleToKind(ModuleHeaderRole Role) {
   switch ((int)Role) {
   default: llvm_unreachable("unknown header role");
@@ -133,7 +151,7 @@ Module *ModuleMap::resolveModuleId(const ModuleId &Id, Module *Mod,
   return Context;
 }
 
-/// \brief Append to \p Paths the set of paths needed to get to the 
+/// Append to \p Paths the set of paths needed to get to the 
 /// subframework in which the given module lives.
 static void appendSubframeworkPaths(Module *Mod,
                                     SmallVectorImpl<char> &Path) {
@@ -152,10 +170,13 @@ static void appendSubframeworkPaths(Module *Mod,
     llvm::sys::path::append(Path, "Frameworks", Paths[I-1] + ".framework");
 }
 
-const FileEntry *
-ModuleMap::findHeader(Module *M,
-                      const Module::UnresolvedHeaderDirective &Header,
-                      SmallVectorImpl<char> &RelativePathName) {
+const FileEntry *ModuleMap::findHeader(
+    Module *M, const Module::UnresolvedHeaderDirective &Header,
+    SmallVectorImpl<char> &RelativePathName, bool &NeedsFramework) {
+  // Search for the header file within the module's home directory.
+  auto *Directory = M->Directory;
+  SmallString<128> FullPathName(Directory->getName());
+
   auto GetFile = [&](StringRef Filename) -> const FileEntry * {
     auto *File = SourceMgr.getFileManager().getFile(Filename);
     if (!File ||
@@ -165,18 +186,8 @@ ModuleMap::findHeader(Module *M,
     return File;
   };
 
-  if (llvm::sys::path::is_absolute(Header.FileName)) {
-    RelativePathName.clear();
-    RelativePathName.append(Header.FileName.begin(), Header.FileName.end());
-    return GetFile(Header.FileName);
-  }
-
-  // Search for the header file within the module's home directory.
-  auto *Directory = M->Directory;
-  SmallString<128> FullPathName(Directory->getName());
-  unsigned FullPathLength = FullPathName.size();
-
-  if (M->isPartOfFramework()) {
+  auto GetFrameworkFile = [&]() -> const FileEntry * {
+    unsigned FullPathLength = FullPathName.size();
     appendSubframeworkPaths(M, RelativePathName);
     unsigned RelativePathLength = RelativePathName.size();
 
@@ -201,18 +212,46 @@ ModuleMap::findHeader(Module *M,
                             Header.FileName);
     llvm::sys::path::append(FullPathName, RelativePathName);
     return GetFile(FullPathName);
+  };
+
+  if (llvm::sys::path::is_absolute(Header.FileName)) {
+    RelativePathName.clear();
+    RelativePathName.append(Header.FileName.begin(), Header.FileName.end());
+    return GetFile(Header.FileName);
   }
 
+  if (M->isPartOfFramework())
+    return GetFrameworkFile();
+
   // Lookup for normal headers.
   llvm::sys::path::append(RelativePathName, Header.FileName);
   llvm::sys::path::append(FullPathName, RelativePathName);
-  return GetFile(FullPathName);
+  auto *NormalHdrFile = GetFile(FullPathName);
+
+  if (M && !NormalHdrFile && Directory->getName().endswith(".framework")) {
+    // The lack of 'framework' keyword in a module declaration it's a simple
+    // mistake we can diagnose when the header exists within the proper
+    // framework style path.
+    FullPathName.assign(Directory->getName());
+    RelativePathName.clear();
+    if (GetFrameworkFile()) {
+      Diags.Report(Header.FileNameLoc,
+                   diag::warn_mmap_incomplete_framework_module_declaration)
+          << Header.FileName << M->getFullModuleName();
+      NeedsFramework = true;
+    }
+    return nullptr;
+  }
+
+  return NormalHdrFile;
 }
 
 void ModuleMap::resolveHeader(Module *Mod,
-                              const Module::UnresolvedHeaderDirective &Header) {
+                              const Module::UnresolvedHeaderDirective &Header,
+                              bool &NeedsFramework) {
   SmallString<128> RelativePathName;
-  if (const FileEntry *File = findHeader(Mod, Header, RelativePathName)) {
+  if (const FileEntry *File =
+          findHeader(Mod, Header, RelativePathName, NeedsFramework)) {
     if (Header.IsUmbrella) {
       const DirectoryEntry *UmbrellaDir = File->getDir();
       if (Module *UmbrellaMod = UmbrellaDirs[UmbrellaDir])
@@ -281,6 +320,8 @@ ModuleMap::ModuleMap(SourceManager &SourceMgr, DiagnosticsEngine &Diags,
 ModuleMap::~ModuleMap() {
   for (auto &M : Modules)
     delete M.getValue();
+  for (auto *M : ShadowModules)
+    delete M;
 }
 
 void ModuleMap::setTarget(const TargetInfo &Target) {
@@ -289,7 +330,7 @@ void ModuleMap::setTarget(const TargetInfo &Target) {
   this->Target = &Target;
 }
 
-/// \brief "Sanitize" a filename so that it can be used as an identifier.
+/// "Sanitize" a filename so that it can be used as an identifier.
 static StringRef sanitizeFilenameAsIdentifier(StringRef Name,
                                               SmallVectorImpl<char> &Buffer) {
   if (Name.empty())
@@ -326,7 +367,7 @@ static StringRef sanitizeFilenameAsIdentifier(StringRef Name,
   return Name;
 }
 
-/// \brief Determine whether the given file name is the name of a builtin
+/// Determine whether the given file name is the name of a builtin
 /// header, supplied by Clang to replace, override, or augment existing system
 /// headers.
 bool ModuleMap::isBuiltinHeader(StringRef FileName) {
@@ -473,7 +514,7 @@ void ModuleMap::diagnoseHeaderInclusion(Module *RequestingModule,
   // We have found a module, but we don't use it.
   if (NotUsed) {
     Diags.Report(FilenameLoc, diag::err_undeclared_use_of_module)
-        << RequestingModule->getFullModuleName() << Filename;
+        << RequestingModule->getTopLevelModule()->Name << Filename;
     return;
   }
 
@@ -484,7 +525,7 @@ void ModuleMap::diagnoseHeaderInclusion(Module *RequestingModule,
 
   if (LangOpts.ModulesStrictDeclUse) {
     Diags.Report(FilenameLoc, diag::err_undeclared_use_of_module)
-        << RequestingModule->getFullModuleName() << Filename;
+        << RequestingModule->getTopLevelModule()->Name << Filename;
   } else if (RequestingModule && RequestingModuleIsModuleInterface &&
              LangOpts.isCompilingModule()) {
     // Do not diagnose when we are not compiling a module. 
@@ -751,7 +792,7 @@ std::pair<Module *, bool> ModuleMap::findOrCreateModule(StringRef Name,
   // Try to find an existing module with this name.
   if (Module *Sub = lookupModuleQualified(Name, Parent))
     return std::make_pair(Sub, false);
-  
+
   // Create a new module with this name.
   Module *Result = new Module(Name, SourceLocation(), Parent, IsFramework,
                               IsExplicit, NumCreatedModules++);
@@ -759,6 +800,7 @@ std::pair<Module *, bool> ModuleMap::findOrCreateModule(StringRef Name,
     if (LangOpts.CurrentModule == Name)
       SourceModule = Result;
     Modules[Name] = Result;
+    ModuleScopeIDs[Result] = CurrentModuleScopeID;
   }
   return std::make_pair(Result, true);
 }
@@ -799,7 +841,7 @@ Module *ModuleMap::createModuleForInterfaceUnit(SourceLocation Loc,
   return Result;
 }
 
-/// \brief For a framework module, infer the framework against which we
+/// For a framework module, infer the framework against which we
 /// should link.
 static void inferFrameworkLink(Module *Mod, const DirectoryEntry *FrameworkDir,
                                FileManager &FileMgr) {
@@ -927,6 +969,7 @@ Module *ModuleMap::inferFrameworkModule(const DirectoryEntry *FrameworkDir,
     if (LangOpts.CurrentModule == ModuleName)
       SourceModule = Result;
     Modules[ModuleName] = Result;
+    ModuleScopeIDs[Result] = CurrentModuleScopeID;
   }
 
   Result->IsSystem |= Attrs.IsSystem;
@@ -999,6 +1042,21 @@ Module *ModuleMap::inferFrameworkModule(const DirectoryEntry *FrameworkDir,
   return Result;
 }
 
+Module *ModuleMap::createShadowedModule(StringRef Name, bool IsFramework,
+                                        Module *ShadowingModule) {
+
+  // Create a new module with this name.
+  Module *Result =
+      new Module(Name, SourceLocation(), /*Parent=*/nullptr, IsFramework,
+                 /*IsExplicit=*/false, NumCreatedModules++);
+  Result->ShadowingModule = ShadowingModule;
+  Result->IsAvailable = false;
+  ModuleScopeIDs[Result] = CurrentModuleScopeID;
+  ShadowModules.push_back(Result);
+
+  return Result;
+}
+
 void ModuleMap::setUmbrellaHeader(Module *Mod, const FileEntry *UmbrellaHeader,
                                   Twine NameAsWritten) {
   Headers[UmbrellaHeader].push_back(KnownHeader(Mod, NormalHeader));
@@ -1019,7 +1077,8 @@ void ModuleMap::setUmbrellaDir(Module *Mod, const DirectoryEntry *UmbrellaDir,
 }
 
 void ModuleMap::addUnresolvedHeader(Module *Mod,
-                                    Module::UnresolvedHeaderDirective Header) {
+                                    Module::UnresolvedHeaderDirective Header,
+                                    bool &NeedsFramework) {
   // If there is a builtin counterpart to this file, add it now so it can
   // wrap the system header.
   if (resolveAsBuiltinHeader(Mod, Header)) {
@@ -1050,7 +1109,7 @@ void ModuleMap::addUnresolvedHeader(Module *Mod,
 
   // We don't have stat information or can't defer looking this file up.
   // Perform the lookup now.
-  resolveHeader(Mod, Header);
+  resolveHeader(Mod, Header, NeedsFramework);
 }
 
 void ModuleMap::resolveHeaderDirectives(const FileEntry *File) const {
@@ -1070,10 +1129,11 @@ void ModuleMap::resolveHeaderDirectives(const FileEntry *File) const {
 }
 
 void ModuleMap::resolveHeaderDirectives(Module *Mod) const {
+  bool NeedsFramework = false;
   for (auto &Header : Mod->UnresolvedHeaders)
     // This operation is logically const; we're just changing how we represent
     // the header information for this file.
-    const_cast<ModuleMap*>(this)->resolveHeader(Mod, Header);
+    const_cast<ModuleMap*>(this)->resolveHeader(Mod, Header, NeedsFramework);
   Mod->UnresolvedHeaders.clear();
 }
 
@@ -1207,7 +1267,7 @@ bool ModuleMap::resolveConflicts(Module *Mod, bool Complain) {
 
 namespace clang {
 
-  /// \brief A token in a module map file.
+  /// A token in a module map file.
   struct MMToken {
     enum TokenKind {
       Comma,
@@ -1277,37 +1337,40 @@ namespace clang {
     Lexer &L;
     SourceManager &SourceMgr;
 
-    /// \brief Default target information, used only for string literal
+    /// Default target information, used only for string literal
     /// parsing.
     const TargetInfo *Target;
 
     DiagnosticsEngine &Diags;
     ModuleMap &Map;
 
-    /// \brief The current module map file.
+    /// The current module map file.
     const FileEntry *ModuleMapFile;
-    
-    /// \brief The directory that file names in this module map file should
+
+    /// Source location of most recent parsed module declaration
+    SourceLocation CurrModuleDeclLoc;
+
+    /// The directory that file names in this module map file should
     /// be resolved relative to.
     const DirectoryEntry *Directory;
 
-    /// \brief Whether this module map is in a system header directory.
+    /// Whether this module map is in a system header directory.
     bool IsSystem;
     
-    /// \brief Whether an error occurred.
+    /// Whether an error occurred.
     bool HadError = false;
         
-    /// \brief Stores string data for the various string literals referenced
+    /// Stores string data for the various string literals referenced
     /// during parsing.
     llvm::BumpPtrAllocator StringData;
     
-    /// \brief The current token.
+    /// The current token.
     MMToken Tok;
     
-    /// \brief The active module.
+    /// The active module.
     Module *ActiveModule = nullptr;
 
-    /// \brief Whether a module uses the 'requires excluded' hack to mark its
+    /// Whether a module uses the 'requires excluded' hack to mark its
     /// contents as 'textual'.
     ///
     /// On older Darwin SDK versions, 'requires excluded' is used to mark the
@@ -1317,10 +1380,10 @@ namespace clang {
     /// 'textual' to match the original intent.
     llvm::SmallPtrSet<Module *, 2> UsesRequiresExcludedHack;
 
-    /// \brief Consume the current token and return its location.
+    /// Consume the current token and return its location.
     SourceLocation consumeToken();
-    
-    /// \brief Skip tokens until we reach the a token with the given kind
+
+    /// Skip tokens until we reach the a token with the given kind
     /// (or the end of the file).
     void skipUntil(MMToken::TokenKind K);
 
@@ -1340,25 +1403,29 @@ namespace clang {
     void parseConflict();
     void parseInferredModuleDecl(bool Framework, bool Explicit);
 
+    /// Private modules are canonicalized as Foo_Private. Clang provides extra
+    /// module map search logic to find the appropriate private module when PCH
+    /// is used with implicit module maps. Warn when private modules are written
+    /// in other ways (FooPrivate and Foo.Private), providing notes and fixits.
+    void diagnosePrivateModules(SourceLocation ExplicitLoc,
+                                SourceLocation FrameworkLoc);
+
     using Attributes = ModuleMap::Attributes;
 
     bool parseOptionalAttributes(Attributes &Attrs);
     
   public:
-    explicit ModuleMapParser(Lexer &L, SourceManager &SourceMgr, 
-                             const TargetInfo *Target,
-                             DiagnosticsEngine &Diags,
-                             ModuleMap &Map,
-                             const FileEntry *ModuleMapFile,
-                             const DirectoryEntry *Directory,
-                             bool IsSystem)
+    explicit ModuleMapParser(Lexer &L, SourceManager &SourceMgr,
+                             const TargetInfo *Target, DiagnosticsEngine &Diags,
+                             ModuleMap &Map, const FileEntry *ModuleMapFile,
+                             const DirectoryEntry *Directory, bool IsSystem)
         : L(L), SourceMgr(SourceMgr), Target(Target), Diags(Diags), Map(Map),
           ModuleMapFile(ModuleMapFile), Directory(Directory),
           IsSystem(IsSystem) {
       Tok.clear();
       consumeToken();
     }
-    
+
     bool parseModuleMapFile();
 
     bool terminatedByDirective() { return false; }
@@ -1559,7 +1626,7 @@ void ModuleMapParser::skipUntil(MMToken::TokenKind K) {
   } while (true);
 }
 
-/// \brief Parse a module-id.
+/// Parse a module-id.
 ///
 ///   module-id:
 ///     identifier
@@ -1588,21 +1655,21 @@ bool ModuleMapParser::parseModuleId(ModuleId &Id) {
 
 namespace {
 
-  /// \brief Enumerates the known attributes.
+  /// Enumerates the known attributes.
   enum AttributeKind {
-    /// \brief An unknown attribute.
+    /// An unknown attribute.
     AT_unknown,
 
-    /// \brief The 'system' attribute.
+    /// The 'system' attribute.
     AT_system,
 
-    /// \brief The 'extern_c' attribute.
+    /// The 'extern_c' attribute.
     AT_extern_c,
 
-    /// \brief The 'exhaustive' attribute.
+    /// The 'exhaustive' attribute.
     AT_exhaustive,
 
-    /// \brief The 'no_undeclared_includes' attribute.
+    /// The 'no_undeclared_includes' attribute.
     AT_no_undeclared_includes
   };
 
@@ -1612,16 +1679,14 @@ namespace {
 /// module map search logic to find the appropriate private module when PCH
 /// is used with implicit module maps. Warn when private modules are written
 /// in other ways (FooPrivate and Foo.Private), providing notes and fixits.
-static void diagnosePrivateModules(const ModuleMap &Map,
-                                   DiagnosticsEngine &Diags,
-                                   const Module *ActiveModule) {
-
+void ModuleMapParser::diagnosePrivateModules(SourceLocation ExplicitLoc,
+                                             SourceLocation FrameworkLoc) {
   auto GenNoteAndFixIt = [&](StringRef BadName, StringRef Canonical,
-                             const Module *M) {
+                             const Module *M, SourceRange ReplLoc) {
     auto D = Diags.Report(ActiveModule->DefinitionLoc,
                           diag::note_mmap_rename_top_level_private_module);
     D << BadName << M->Name;
-    D << FixItHint::CreateReplacement(ActiveModule->DefinitionLoc, Canonical);
+    D << FixItHint::CreateReplacement(ReplLoc, Canonical);
   };
 
   for (auto E = Map.module_begin(); E != Map.module_end(); ++E) {
@@ -1632,6 +1697,7 @@ static void diagnosePrivateModules(const ModuleMap &Map,
     SmallString<128> FullName(ActiveModule->getFullModuleName());
     if (!FullName.startswith(M->Name) && !FullName.endswith("Private"))
       continue;
+    SmallString<128> FixedPrivModDecl;
     SmallString<128> Canonical(M->Name);
     Canonical.append("_Private");
 
@@ -1641,7 +1707,20 @@ static void diagnosePrivateModules(const ModuleMap &Map,
       Diags.Report(ActiveModule->DefinitionLoc,
                    diag::warn_mmap_mismatched_private_submodule)
           << FullName;
-      GenNoteAndFixIt(FullName, Canonical, M);
+
+      SourceLocation FixItInitBegin = CurrModuleDeclLoc;
+      if (FrameworkLoc.isValid())
+        FixItInitBegin = FrameworkLoc;
+      if (ExplicitLoc.isValid())
+        FixItInitBegin = ExplicitLoc;
+
+      if (FrameworkLoc.isValid() || ActiveModule->Parent->IsFramework)
+        FixedPrivModDecl.append("framework ");
+      FixedPrivModDecl.append("module ");
+      FixedPrivModDecl.append(Canonical);
+
+      GenNoteAndFixIt(FullName, FixedPrivModDecl, M,
+                      SourceRange(FixItInitBegin, ActiveModule->DefinitionLoc));
       continue;
     }
 
@@ -1651,12 +1730,13 @@ static void diagnosePrivateModules(const ModuleMap &Map,
       Diags.Report(ActiveModule->DefinitionLoc,
                    diag::warn_mmap_mismatched_private_module_name)
           << ActiveModule->Name;
-      GenNoteAndFixIt(ActiveModule->Name, Canonical, M);
+      GenNoteAndFixIt(ActiveModule->Name, Canonical, M,
+                      SourceRange(ActiveModule->DefinitionLoc));
     }
   }
 }
 
-/// \brief Parse a module declaration.
+/// Parse a module declaration.
 ///
 ///   module-declaration:
 ///     'extern' 'module' module-id string-literal
@@ -1684,6 +1764,7 @@ void ModuleMapParser::parseModuleDecl() {
 
   // Parse 'explicit' or 'framework' keyword, if present.
   SourceLocation ExplicitLoc;
+  SourceLocation FrameworkLoc;
   bool Explicit = false;
   bool Framework = false;
 
@@ -1695,7 +1776,7 @@ void ModuleMapParser::parseModuleDecl() {
 
   // Parse 'framework' keyword, if present.
   if (Tok.is(MMToken::FrameworkKeyword)) {
-    consumeToken();
+    FrameworkLoc = consumeToken();
     Framework = true;
   } 
   
@@ -1706,7 +1787,7 @@ void ModuleMapParser::parseModuleDecl() {
     HadError = true;
     return;
   }
-  consumeToken(); // 'module' keyword
+  CurrModuleDeclLoc = consumeToken(); // 'module' keyword
 
   // If we have a wildcard for the module name, this is an inferred submodule.
   // Parse it. 
@@ -1787,6 +1868,7 @@ void ModuleMapParser::parseModuleDecl() {
   SourceLocation LBraceLoc = consumeToken();
   
   // Determine whether this (sub)module has already been defined.
+  Module *ShadowingModule = nullptr;
   if (Module *Existing = Map.lookupModuleQualified(ModuleName, ActiveModule)) {
     // We might see a (re)definition of a module that we already have a
     // definition for in two cases:
@@ -1812,23 +1894,35 @@ void ModuleMapParser::parseModuleDecl() {
       }
       return;
     }
-    
-    Diags.Report(ModuleNameLoc, diag::err_mmap_module_redefinition)
-      << ModuleName;
-    Diags.Report(Existing->DefinitionLoc, diag::note_mmap_prev_definition);
-    
-    // Skip the module definition.
-    skipUntil(MMToken::RBrace);
-    if (Tok.is(MMToken::RBrace))
-      consumeToken();
-    
-    HadError = true;
-    return;
+
+    if (!Existing->Parent && Map.mayShadowNewModule(Existing)) {
+      ShadowingModule = Existing;
+    } else {
+      // This is not a shawdowed module decl, it is an illegal redefinition.
+      Diags.Report(ModuleNameLoc, diag::err_mmap_module_redefinition)
+          << ModuleName;
+      Diags.Report(Existing->DefinitionLoc, diag::note_mmap_prev_definition);
+
+      // Skip the module definition.
+      skipUntil(MMToken::RBrace);
+      if (Tok.is(MMToken::RBrace))
+        consumeToken();
+
+      HadError = true;
+      return;
+    }
   }
 
   // Start defining this module.
-  ActiveModule = Map.findOrCreateModule(ModuleName, ActiveModule, Framework,
-                                        Explicit).first;
+  if (ShadowingModule) {
+    ActiveModule =
+        Map.createShadowedModule(ModuleName, Framework, ShadowingModule);
+  } else {
+    ActiveModule =
+        Map.findOrCreateModule(ModuleName, ActiveModule, Framework, Explicit)
+            .first;
+  }
+
   ActiveModule->DefinitionLoc = ModuleNameLoc;
   if (Attrs.IsSystem || IsSystem)
     ActiveModule->IsSystem = true;
@@ -1839,21 +1933,24 @@ void ModuleMapParser::parseModuleDecl() {
     ActiveModule->NoUndeclaredIncludes = true;
   ActiveModule->Directory = Directory;
 
+  StringRef MapFileName(ModuleMapFile->getName());
+  if (MapFileName.endswith("module.private.modulemap") ||
+      MapFileName.endswith("module_private.map")) {
+    ActiveModule->ModuleMapIsPrivate = true;
+  }
 
   // Private modules named as FooPrivate, Foo.Private or similar are likely a
   // user error; provide warnings, notes and fixits to direct users to use
   // Foo_Private instead.
   SourceLocation StartLoc =
       SourceMgr.getLocForStartOfFile(SourceMgr.getMainFileID());
-  StringRef MapFileName(ModuleMapFile->getName());
   if (Map.HeaderInfo.getHeaderSearchOpts().ImplicitModuleMaps &&
       !Diags.isIgnored(diag::warn_mmap_mismatched_private_submodule,
                        StartLoc) &&
       !Diags.isIgnored(diag::warn_mmap_mismatched_private_module_name,
                        StartLoc) &&
-      (MapFileName.endswith("module.private.modulemap") ||
-       MapFileName.endswith("module_private.map")))
-    diagnosePrivateModules(Map, Diags, ActiveModule);
+      ActiveModule->ModuleMapIsPrivate)
+    diagnosePrivateModules(ExplicitLoc, FrameworkLoc);
 
   bool Done = false;
   do {
@@ -1958,7 +2055,7 @@ void ModuleMapParser::parseModuleDecl() {
   ActiveModule = PreviousActiveModule;
 }
 
-/// \brief Parse an extern module declaration.
+/// Parse an extern module declaration.
 ///
 ///   extern module-declaration:
 ///     'extern' 'module' module-id string-literal
@@ -2036,7 +2133,7 @@ static bool shouldAddRequirement(Module *M, StringRef Feature,
   return true;
 }
 
-/// \brief Parse a requires declaration.
+/// Parse a requires declaration.
 ///
 ///   requires-declaration:
 ///     'requires' feature-list
@@ -2092,7 +2189,7 @@ void ModuleMapParser::parseRequiresDecl() {
   } while (true);
 }
 
-/// \brief Parse a header declaration.
+/// Parse a header declaration.
 ///
 ///   header-declaration:
 ///     'textual'[opt] 'header' string-literal
@@ -2212,7 +2309,13 @@ void ModuleMapParser::parseHeaderDecl(MMToken::TokenKind LeadingToken,
     }
   }
 
-  Map.addUnresolvedHeader(ActiveModule, std::move(Header));
+  bool NeedsFramework = false;
+  Map.addUnresolvedHeader(ActiveModule, std::move(Header), NeedsFramework);
+
+  if (NeedsFramework && ActiveModule)
+    Diags.Report(CurrModuleDeclLoc, diag::note_mmap_add_framework_keyword)
+      << ActiveModule->getFullModuleName()
+      << FixItHint::CreateReplacement(CurrModuleDeclLoc, "framework module");
 }
 
 static int compareModuleHeaders(const Module::Header *A,
@@ -2220,7 +2323,7 @@ static int compareModuleHeaders(const Module::Header *A,
   return A->NameAsWritten.compare(B->NameAsWritten);
 }
 
-/// \brief Parse an umbrella directory declaration.
+/// Parse an umbrella directory declaration.
 ///
 ///   umbrella-dir-declaration:
 ///     umbrella string-literal
@@ -2298,7 +2401,7 @@ void ModuleMapParser::parseUmbrellaDirDecl(SourceLocation UmbrellaLoc) {
   Map.setUmbrellaDir(ActiveModule, Dir, DirName);
 }
 
-/// \brief Parse a module export declaration.
+/// Parse a module export declaration.
 ///
 ///   export-declaration:
 ///     'export' wildcard-module-id
@@ -2346,7 +2449,7 @@ void ModuleMapParser::parseExportDecl() {
   ActiveModule->UnresolvedExports.push_back(Unresolved);
 }
 
-/// \brief Parse a module export_as declaration.
+/// Parse a module export_as declaration.
 ///
 ///   export-as-declaration:
 ///     'export_as' identifier
@@ -2378,10 +2481,12 @@ void ModuleMapParser::parseExportAsDecl() {
   }
   
   ActiveModule->ExportAsModule = Tok.getString();
+  Map.addLinkAsDependency(ActiveModule);
+
   consumeToken();
 }
 
-/// \brief Parse a module use declaration.
+/// Parse a module use declaration.
 ///
 ///   use-declaration:
 ///     'use' wildcard-module-id
@@ -2398,7 +2503,7 @@ void ModuleMapParser::parseUseDecl() {
     ActiveModule->UnresolvedDirectUses.push_back(ParsedModuleId);
 }
 
-/// \brief Parse a link declaration.
+/// Parse a link declaration.
 ///
 ///   module-declaration:
 ///     'link' 'framework'[opt] string-literal
@@ -2427,7 +2532,7 @@ void ModuleMapParser::parseLinkDecl() {
                                                             IsFramework));
 }
 
-/// \brief Parse a configuration macro declaration.
+/// Parse a configuration macro declaration.
 ///
 ///   module-declaration:
 ///     'config_macros' attributes[opt] config-macro-list?
@@ -2484,7 +2589,7 @@ void ModuleMapParser::parseConfigMacros() {
   } while (true);
 }
 
-/// \brief Format a module-id into a string.
+/// Format a module-id into a string.
 static std::string formatModuleId(const ModuleId &Id) {
   std::string result;
   {
@@ -2500,7 +2605,7 @@ static std::string formatModuleId(const ModuleId &Id) {
   return result;
 }
 
-/// \brief Parse a conflict declaration.
+/// Parse a conflict declaration.
 ///
 ///   module-declaration:
 ///     'conflict' module-id ',' string-literal
@@ -2534,7 +2639,7 @@ void ModuleMapParser::parseConflict() {
   ActiveModule->UnresolvedConflicts.push_back(Conflict);
 }
 
-/// \brief Parse an inferred module declaration (wildcard modules).
+/// Parse an inferred module declaration (wildcard modules).
 ///
 ///   module-declaration:
 ///     'explicit'[opt] 'framework'[opt] 'module' * attributes[opt]
@@ -2687,7 +2792,7 @@ void ModuleMapParser::parseInferredModuleDecl(bool Framework, bool Explicit) {
   }
 }
 
-/// \brief Parse optional attributes.
+/// Parse optional attributes.
 ///
 ///   attributes:
 ///     attribute attributes
@@ -2762,7 +2867,7 @@ bool ModuleMapParser::parseOptionalAttributes(Attributes &Attrs) {
   return HadError;
 }
 
-/// \brief Parse a module map file.
+/// Parse a module map file.
 ///
 ///   module-map-file:
 ///     module-declaration*
@@ -2854,5 +2959,6 @@ bool ModuleMap::parseModuleMapFile(const FileEntry *File, bool IsSystem,
   // Notify callbacks that we parsed it.
   for (const auto &Cb : Callbacks)
     Cb->moduleMapFileRead(Start, *File, IsSystem);
+
   return Result;
 }
diff --git a/lib/Lex/PPCaching.cpp b/lib/Lex/PPCaching.cpp
index f5e8cdc25d388..9758557d7b448 100644
--- a/lib/Lex/PPCaching.cpp
+++ b/lib/Lex/PPCaching.cpp
@@ -105,8 +105,10 @@ void Preprocessor::CachingLex(Token &Result) {
 }
 
 void Preprocessor::EnterCachingLexMode() {
-  if (InCachingLexMode())
+  if (InCachingLexMode()) {
+    assert(CurLexerKind == CLK_CachingLexer && "Unexpected lexer kind");
     return;
+  }
 
   PushIncludeMacroStack();
   CurLexerKind = CLK_CachingLexer;
diff --git a/lib/Lex/PPDirectives.cpp b/lib/Lex/PPDirectives.cpp
index ca3e70fd1060e..d8dae73037a89 100644
--- a/lib/Lex/PPDirectives.cpp
+++ b/lib/Lex/PPDirectives.cpp
@@ -8,7 +8,7 @@
 //===----------------------------------------------------------------------===//
 ///
 /// \file
-/// \brief Implements # directive processing for the Preprocessor.
+/// Implements # directive processing for the Preprocessor.
 ///
 //===----------------------------------------------------------------------===//
 
@@ -78,7 +78,7 @@ Preprocessor::AllocateVisibilityMacroDirective(SourceLocation Loc,
   return new (BP) VisibilityMacroDirective(Loc, isPublic);
 }
 
-/// \brief Read and discard all tokens remaining on the current line until
+/// Read and discard all tokens remaining on the current line until
 /// the tok::eod token is found.
 void Preprocessor::DiscardUntilEndOfDirective() {
   Token Tmp;
@@ -88,14 +88,14 @@ void Preprocessor::DiscardUntilEndOfDirective() {
   } while (Tmp.isNot(tok::eod));
 }
 
-/// \brief Enumerates possible cases of #define/#undef a reserved identifier.
+/// Enumerates possible cases of #define/#undef a reserved identifier.
 enum MacroDiag {
   MD_NoWarn,        //> Not a reserved identifier
   MD_KeywordDef,    //> Macro hides keyword, enabled by default
   MD_ReservedMacro  //> #define of #undef reserved id, disabled by default
 };
 
-/// \brief Checks if the specified identifier is reserved in the specified
+/// Checks if the specified identifier is reserved in the specified
 /// language.
 /// This function does not check if the identifier is a keyword.
 static bool isReservedId(StringRef Text, const LangOptions &Lang) {
@@ -115,6 +115,25 @@ static bool isReservedId(StringRef Text, const LangOptions &Lang) {
   return false;
 }
 
+// The -fmodule-name option tells the compiler to textually include headers in
+// the specified module, meaning clang won't build the specified module. This is
+// useful in a number of situations, for instance, when building a library that
+// vends a module map, one might want to avoid hitting intermediate build
+// products containig the the module map or avoid finding the system installed
+// modulemap for that library.
+static bool isForModuleBuilding(Module *M, StringRef CurrentModule,
+                                StringRef ModuleName) {
+  StringRef TopLevelName = M->getTopLevelModuleName();
+
+  // When building framework Foo, we wanna make sure that Foo *and* Foo_Private
+  // are textually included and no modules are built for both.
+  if (M->getTopLevelModule()->IsFramework && CurrentModule == ModuleName &&
+      !CurrentModule.endswith("_Private") && TopLevelName.endswith("_Private"))
+    TopLevelName = TopLevelName.drop_back(8);
+
+  return TopLevelName == CurrentModule;
+}
+
 static MacroDiag shouldWarnOnMacroDef(Preprocessor &PP, IdentifierInfo *II) {
   const LangOptions &Lang = PP.getLangOpts();
   StringRef Text = II->getName();
@@ -277,7 +296,7 @@ bool Preprocessor::CheckMacroName(Token &MacroNameTok, MacroUse isDefineUndef,
   return false;
 }
 
-/// \brief Lex and validate a macro name, which occurs after a
+/// Lex and validate a macro name, which occurs after a
 /// \#define or \#undef.
 ///
 /// This sets the token kind to eod and discards the rest of the macro line if
@@ -309,7 +328,7 @@ void Preprocessor::ReadMacroName(Token &MacroNameTok, MacroUse isDefineUndef,
   }
 }
 
-/// \brief Ensure that the next token is a tok::eod token.
+/// Ensure that the next token is a tok::eod token.
 ///
 /// If not, emit a diagnostic and consume up until the eod.  If EnableMacros is
 /// true, then we consider macros that expand to zero tokens as being ok.
@@ -558,7 +577,9 @@ void Preprocessor::SkipExcludedConditionalBlock(SourceLocation HashTokenLoc,
   // the #if block.
   CurPPLexer->LexingRawMode = false;
 
-  if (Callbacks)
+  // The last skipped range isn't actually skipped yet if it's truncated
+  // by the end of the preamble; we'll resume parsing after the preamble.
+  if (Callbacks && (Tok.isNot(tok::eof) || !isRecordingPreamble()))
     Callbacks->SourceRangeSkipped(
         SourceRange(HashTokenLoc, CurPPLexer->getSourceLocation()),
         Tok.getLocation());
@@ -866,6 +887,22 @@ private:
   bool save;
 };
 
+/// Process a directive while looking for the through header.
+/// Only #include (to check if it is the through header) and #define (to warn
+/// about macros that don't match the PCH) are handled. All other directives
+/// are completely discarded.
+void Preprocessor::HandleSkippedThroughHeaderDirective(Token &Result,
+                                                       SourceLocation HashLoc) {
+  if (const IdentifierInfo *II = Result.getIdentifierInfo()) {
+    if (II->getPPKeywordID() == tok::pp_include)
+      return HandleIncludeDirective(HashLoc, Result);
+    if (II->getPPKeywordID() == tok::pp_define)
+      return HandleDefineDirective(Result,
+                                   /*ImmediatelyAfterHeaderGuard=*/false);
+  }
+  DiscardUntilEndOfDirective();
+}
+
 /// HandleDirective - This callback is invoked when the lexer sees a # token
 /// at the start of a line.  This consumes the directive, modifies the
 /// lexer/preprocessor state, and advances the lexer(s) so that the next token
@@ -927,6 +964,9 @@ void Preprocessor::HandleDirective(Token &Result) {
   // and reset to previous state when returning from this function.
   ResetMacroExpansionHelper helper(this);
 
+  if (SkippingUntilPCHThroughHeader)
+    return HandleSkippedThroughHeaderDirective(Result, SavedHash.getLocation());
+
   switch (Result.getKind()) {
   case tok::eod:
     return;   // null directive.
@@ -1107,7 +1147,7 @@ static bool GetLineValue(Token &DigitTok, unsigned &Val,
   return false;
 }
 
-/// \brief Handle a \#line directive: C99 6.10.4.
+/// Handle a \#line directive: C99 6.10.4.
 ///
 /// The two acceptable forms are:
 /// \verbatim
@@ -1343,7 +1383,7 @@ void Preprocessor::HandleUserDiagnosticDirective(Token &Tok,
   // Read the rest of the line raw.  We do this because we don't want macros
   // to be expanded and we don't require that the tokens be valid preprocessing
   // tokens.  For example, this is allowed: "#warning `   'foo".  GCC does
-  // collapse multiple consequtive white space between tokens, but this isn't
+  // collapse multiple consecutive white space between tokens, but this isn't
   // specified by the standard.
   SmallString<128> Message;
   CurLexer->ReadToEndOfLine(&Message);
@@ -1393,7 +1433,7 @@ void Preprocessor::HandleIdentSCCSDirective(Token &Tok) {
   }
 }
 
-/// \brief Handle a #public directive.
+/// Handle a #public directive.
 void Preprocessor::HandleMacroPublicDirective(Token &Tok) {
   Token MacroNameTok;
   ReadMacroName(MacroNameTok, MU_Undef);
@@ -1420,7 +1460,7 @@ void Preprocessor::HandleMacroPublicDirective(Token &Tok) {
                                 MacroNameTok.getLocation(), /*IsPublic=*/true));
 }
 
-/// \brief Handle a #private directive.
+/// Handle a #private directive.
 void Preprocessor::HandleMacroPrivateDirective() {
   Token MacroNameTok;
   ReadMacroName(MacroNameTok, MU_Undef);
@@ -1496,7 +1536,7 @@ bool Preprocessor::GetIncludeFilenameSpelling(SourceLocation Loc,
   return isAngled;
 }
 
-// \brief Handle cases where the \#include name is expanded from a macro
+// Handle cases where the \#include name is expanded from a macro
 // as multiple tokens, which need to be glued together.
 //
 // This occurs for code like:
@@ -1557,7 +1597,7 @@ bool Preprocessor::ConcatenateIncludeName(SmallString<128> &FilenameBuffer,
   return true;
 }
 
-/// \brief Push a token onto the token stream containing an annotation.
+/// Push a token onto the token stream containing an annotation.
 void Preprocessor::EnterAnnotationToken(SourceRange Range,
                                         tok::TokenKind Kind,
                                         void *AnnotationVal) {
@@ -1572,7 +1612,7 @@ void Preprocessor::EnterAnnotationToken(SourceRange Range,
   EnterTokenStream(std::move(Tok), 1, true);
 }
 
-/// \brief Produce a diagnostic informing the user that a #include or similar
+/// Produce a diagnostic informing the user that a #include or similar
 /// was implicitly treated as a module import.
 static void diagnoseAutoModuleImport(
     Preprocessor &PP, SourceLocation HashLoc, Token &IncludeTok,
@@ -1655,12 +1695,18 @@ bool Preprocessor::checkModuleIsAvailable(const LangOptions &LangOpts,
                                           DiagnosticsEngine &Diags, Module *M) {
   Module::Requirement Requirement;
   Module::UnresolvedHeaderDirective MissingHeader;
-  if (M->isAvailable(LangOpts, TargetInfo, Requirement, MissingHeader))
+  Module *ShadowingModule = nullptr;
+  if (M->isAvailable(LangOpts, TargetInfo, Requirement, MissingHeader,
+                     ShadowingModule))
     return false;
 
   if (MissingHeader.FileNameLoc.isValid()) {
     Diags.Report(MissingHeader.FileNameLoc, diag::err_module_header_missing)
         << MissingHeader.IsUmbrella << MissingHeader.FileName;
+  } else if (ShadowingModule) {
+    Diags.Report(M->DefinitionLoc, diag::err_module_shadowed) << M->Name;
+    Diags.Report(ShadowingModule->DefinitionLoc,
+                 diag::note_previous_definition);
   } else {
     // FIXME: Track the location at which the requirement was specified, and
     // use it here.
@@ -1779,7 +1825,7 @@ void Preprocessor::HandleIncludeDirective(SourceLocation HashLoc,
   SmallString<128> NormalizedPath;
   if (LangOpts.MSVCCompat) {
     NormalizedPath = Filename.str();
-#ifndef LLVM_ON_WIN32
+#ifndef _WIN32
     llvm::sys::path::native(NormalizedPath);
 #endif
   }
@@ -1835,6 +1881,12 @@ void Preprocessor::HandleIncludeDirective(SourceLocation HashLoc,
     }
   }
 
+  if (usingPCHWithThroughHeader() && SkippingUntilPCHThroughHeader) {
+    if (isPCHThroughHeader(File))
+      SkippingUntilPCHThroughHeader = false;
+    return;
+  }
+
   // Should we enter the source file? Set to false if either the source file is
   // known to have no effect beyond its effect on module visibility -- that is,
   // if it's got an include guard that is already defined or is a modular header
@@ -1844,12 +1896,19 @@ void Preprocessor::HandleIncludeDirective(SourceLocation HashLoc,
   if (PPOpts->SingleFileParseMode)
     ShouldEnter = false;
 
+  // Any diagnostics after the fatal error will not be visible. As the
+  // compilation failed already and errors in subsequently included files won't
+  // be visible, avoid preprocessing those files.
+  if (ShouldEnter && Diags->hasFatalErrorOccurred())
+    ShouldEnter = false;
+
   // Determine whether we should try to import the module for this #include, if
   // there is one. Don't do so if precompiled module support is disabled or we
   // are processing this module textually (because we're building the module).
   if (ShouldEnter && File && SuggestedModule && getLangOpts().Modules &&
-      SuggestedModule.getModule()->getTopLevelModuleName() !=
-          getLangOpts().CurrentModule) {
+      !isForModuleBuilding(SuggestedModule.getModule(),
+                           getLangOpts().CurrentModule,
+                           getLangOpts().ModuleName)) {
     // If this include corresponds to a module but that module is
     // unavailable, diagnose the situation and bail out.
     // FIXME: Remove this; loadModule does the same check (but produces
@@ -1940,7 +1999,7 @@ void Preprocessor::HandleIncludeDirective(SourceLocation HashLoc,
         HashLoc, IncludeTok,
         LangOpts.MSVCCompat ? NormalizedPath.c_str() : Filename, isAngled,
         FilenameRange, File, SearchPath, RelativePath,
-        ShouldEnter ? nullptr : SuggestedModule.getModule());
+        ShouldEnter ? nullptr : SuggestedModule.getModule(), FileCharacter);
     if (SkipHeader && !SuggestedModule.getModule())
       Callbacks->FileSkipped(*File, FilenameTok, FileCharacter);
   }
@@ -1996,7 +2055,8 @@ void Preprocessor::HandleIncludeDirective(SourceLocation HashLoc,
       // ShouldEnter is false because we are skipping the header. In that
       // case, We are not importing the specified module.
       if (SkipHeader && getLangOpts().CompilingPCH &&
-          M->getTopLevelModuleName() == getLangOpts().CurrentModule)
+          isForModuleBuilding(M, getLangOpts().CurrentModule,
+                              getLangOpts().ModuleName))
         return;
 
       makeModuleVisible(M, HashLoc);
@@ -2014,7 +2074,7 @@ void Preprocessor::HandleIncludeDirective(SourceLocation HashLoc,
   // If the filename string was the result of macro expansions, set the include
   // position on the file where it will be included and after the expansions.
   if (IncludePos.isMacroID())
-    IncludePos = SourceMgr.getExpansionRange(IncludePos).second;
+    IncludePos = SourceMgr.getExpansionRange(IncludePos).getEnd();
   FileID FID = SourceMgr.createFileID(File, IncludePos, FileCharacter);
   assert(FID.isValid() && "Expected valid file ID");
 
@@ -2024,11 +2084,21 @@ void Preprocessor::HandleIncludeDirective(SourceLocation HashLoc,
 
   // Determine if we're switching to building a new submodule, and which one.
   if (auto *M = SuggestedModule.getModule()) {
+    if (M->getTopLevelModule()->ShadowingModule) {
+      // We are building a submodule that belongs to a shadowed module. This
+      // means we find header files in the shadowed module.
+      Diag(M->DefinitionLoc, diag::err_module_build_shadowed_submodule)
+        << M->getFullModuleName();
+      Diag(M->getTopLevelModule()->ShadowingModule->DefinitionLoc,
+           diag::note_previous_definition);
+      return;
+    }
     // When building a pch, -fmodule-name tells the compiler to textually
     // include headers in the specified module. We are not building the
     // specified module.
     if (getLangOpts().CompilingPCH &&
-        M->getTopLevelModuleName() == getLangOpts().CurrentModule)
+        isForModuleBuilding(M, getLangOpts().CurrentModule,
+                            getLangOpts().ModuleName))
       return;
 
     assert(!CurLexerSubmodule && "should not have marked this as a module yet");
@@ -2548,7 +2618,15 @@ void Preprocessor::HandleDefineDirective(
     }
   }
 
-  
+  // When skipping just warn about macros that do not match.
+  if (SkippingUntilPCHThroughHeader) {
+    const MacroInfo *OtherMI = getMacroInfo(MacroNameTok.getIdentifierInfo());
+    if (!OtherMI || !MI->isIdenticalTo(*OtherMI, *this,
+                             /*Syntactic=*/LangOpts.MicrosoftExt))
+      Diag(MI->getDefinitionLoc(), diag::warn_pp_macro_def_mismatch_with_pch)
+          << MacroNameTok.getIdentifierInfo();
+    return;
+  }
 
   // Finally, if this identifier already had a macro defined for it, verify that
   // the macro bodies are identical, and issue diagnostics if they are not.
diff --git a/lib/Lex/PPExpressions.cpp b/lib/Lex/PPExpressions.cpp
index d8431827e9cde..b1ed0e10c6fc7 100644
--- a/lib/Lex/PPExpressions.cpp
+++ b/lib/Lex/PPExpressions.cpp
@@ -363,7 +363,7 @@ static bool EvaluateValue(PPValue &Result, Token &PeekTok, DefinedTracker &DT,
       NumBits = TI.getChar16Width();
     else if (Literal.isUTF32())
       NumBits = TI.getChar32Width();
-    else
+    else // char or char8_t
       NumBits = TI.getCharWidth();
 
     // Set the width.
diff --git a/lib/Lex/PPLexerChange.cpp b/lib/Lex/PPLexerChange.cpp
index e484e9c4c3a38..352814d715fa9 100644
--- a/lib/Lex/PPLexerChange.cpp
+++ b/lib/Lex/PPLexerChange.cpp
@@ -13,6 +13,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "clang/Lex/Preprocessor.h"
+#include "clang/Lex/PreprocessorOptions.h"
 #include "clang/Basic/FileManager.h"
 #include "clang/Basic/SourceManager.h"
 #include "clang/Lex/HeaderSearch.h"
@@ -226,7 +227,7 @@ void Preprocessor::EnterTokenStream(const Token *Toks, unsigned NumToks,
     CurLexerKind = CLK_TokenLexer;
 }
 
-/// \brief Compute the relative path that names the given file relative to
+/// Compute the relative path that names the given file relative to
 /// the given directory.
 static void computeRelativePath(FileManager &FM, const DirectoryEntry *Dir,
                                 const FileEntry *File,
@@ -264,7 +265,7 @@ void Preprocessor::PropagateLineStartLeadingSpaceInfo(Token &Result) {
   // but it might if they're empty?
 }
 
-/// \brief Determine the location to use as the end of the buffer for a lexer.
+/// Determine the location to use as the end of the buffer for a lexer.
 ///
 /// If the file ends with a newline, form the EOF token on the newline itself,
 /// rather than "on the line following it", which doesn't exist.  This makes
@@ -425,6 +426,8 @@ bool Preprocessor::HandleEndOfFile(Token &Result, bool isEndOfMacro) {
     PragmaAssumeNonNullLoc = SourceLocation();
   }
 
+  bool LeavingPCHThroughHeader = false;
+
   // If this is a #include'd file, pop it off the include stack and continue
   // lexing the #includer file.
   if (!IncludeMacroStack.empty()) {
@@ -444,6 +447,7 @@ bool Preprocessor::HandleEndOfFile(Token &Result, bool isEndOfMacro) {
       }
 
       CurPPLexer = nullptr;
+      recomputeCurLexerKind();
       return true;
     }
 
@@ -480,6 +484,12 @@ bool Preprocessor::HandleEndOfFile(Token &Result, bool isEndOfMacro) {
       Result.setAnnotationValue(M);
     }
 
+    bool FoundPCHThroughHeader = false;
+    if (CurPPLexer && creatingPCHWithThroughHeader() &&
+        isPCHThroughHeader(
+            SourceMgr.getFileEntryForID(CurPPLexer->getFileID())))
+      FoundPCHThroughHeader = true;
+
     // We're done with the #included file.
     RemoveTopOfLexerStack();
 
@@ -499,8 +509,16 @@ bool Preprocessor::HandleEndOfFile(Token &Result, bool isEndOfMacro) {
     if (ExitedFromPredefinesFile)
       replayPreambleConditionalStack();
 
-    // Client should lex another token unless we generated an EOM.
-    return LeavingSubmodule;
+    if (!isEndOfMacro && CurPPLexer && FoundPCHThroughHeader &&
+        (isInPrimaryFile() ||
+         CurPPLexer->getFileID() == getPredefinesFileID())) {
+      // Leaving the through header. Continue directly to end of main file
+      // processing.
+      LeavingPCHThroughHeader = true;
+    } else {
+      // Client should lex another token unless we generated an EOM.
+      return LeavingSubmodule;
+    }
   }
 
   // If this is the end of the main file, form an EOF token.
@@ -521,6 +539,12 @@ bool Preprocessor::HandleEndOfFile(Token &Result, bool isEndOfMacro) {
         Result.setLocation(Result.getLocation().getLocWithOffset(-1));
     }
 
+    if (creatingPCHWithThroughHeader() && !LeavingPCHThroughHeader) {
+      // Reached the end of the compilation without finding the through header.
+      Diag(CurLexer->getFileLoc(), diag::err_pp_through_header_not_seen)
+          << PPOpts->PCHThroughHeader << 0;
+    }
+
     if (!isIncrementalProcessingEnabled())
       // We're done with lexing.
       CurLexer.reset();
diff --git a/lib/Lex/PPMacroExpansion.cpp b/lib/Lex/PPMacroExpansion.cpp
index 41633f90c34da..d9992e00f8c0f 100644
--- a/lib/Lex/PPMacroExpansion.cpp
+++ b/lib/Lex/PPMacroExpansion.cpp
@@ -41,7 +41,6 @@
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/StringSwitch.h"
-#include "llvm/Config/llvm-config.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/Format.h"
@@ -1016,7 +1015,7 @@ MacroArgs *Preprocessor::ReadMacroCallArgumentList(Token &MacroName,
   return MacroArgs::create(MI, ArgTokens, isVarargsElided, *this);
 }
 
-/// \brief Keeps macro expanded tokens for TokenLexers.
+/// Keeps macro expanded tokens for TokenLexers.
 //
 /// Works like a stack; a TokenLexer adds the macro expanded tokens that is
 /// going to lex in the cache and when it finishes the tokens are removed
@@ -1100,183 +1099,11 @@ static bool HasFeature(const Preprocessor &PP, StringRef Feature) {
   if (Feature.startswith("__") && Feature.endswith("__") && Feature.size() >= 4)
     Feature = Feature.substr(2, Feature.size() - 4);
 
+#define FEATURE(Name, Predicate) .Case(#Name, Predicate)
   return llvm::StringSwitch<bool>(Feature)
-      .Case("address_sanitizer",
-            LangOpts.Sanitize.hasOneOf(SanitizerKind::Address |
-                                       SanitizerKind::KernelAddress))
-      .Case("hwaddress_sanitizer",
-            LangOpts.Sanitize.hasOneOf(SanitizerKind::HWAddress))
-      .Case("assume_nonnull", true)
-      .Case("attribute_analyzer_noreturn", true)
-      .Case("attribute_availability", true)
-      .Case("attribute_availability_with_message", true)
-      .Case("attribute_availability_app_extension", true)
-      .Case("attribute_availability_with_version_underscores", true)
-      .Case("attribute_availability_tvos", true)
-      .Case("attribute_availability_watchos", true)
-      .Case("attribute_availability_with_strict", true)
-      .Case("attribute_availability_with_replacement", true)
-      .Case("attribute_availability_in_templates", true)
-      .Case("attribute_cf_returns_not_retained", true)
-      .Case("attribute_cf_returns_retained", true)
-      .Case("attribute_cf_returns_on_parameters", true)
-      .Case("attribute_deprecated_with_message", true)
-      .Case("attribute_deprecated_with_replacement", true)
-      .Case("attribute_ext_vector_type", true)
-      .Case("attribute_ns_returns_not_retained", true)
-      .Case("attribute_ns_returns_retained", true)
-      .Case("attribute_ns_consumes_self", true)
-      .Case("attribute_ns_consumed", true)
-      .Case("attribute_cf_consumed", true)
-      .Case("attribute_objc_ivar_unused", true)
-      .Case("attribute_objc_method_family", true)
-      .Case("attribute_overloadable", true)
-      .Case("attribute_unavailable_with_message", true)
-      .Case("attribute_unused_on_fields", true)
-      .Case("attribute_diagnose_if_objc", true)
-      .Case("blocks", LangOpts.Blocks)
-      .Case("c_thread_safety_attributes", true)
-      .Case("cxx_exceptions", LangOpts.CXXExceptions)
-      .Case("cxx_rtti", LangOpts.RTTI && LangOpts.RTTIData)
-      .Case("enumerator_attributes", true)
-      .Case("nullability", true)
-      .Case("nullability_on_arrays", true)
-      .Case("memory_sanitizer", LangOpts.Sanitize.has(SanitizerKind::Memory))
-      .Case("thread_sanitizer", LangOpts.Sanitize.has(SanitizerKind::Thread))
-      .Case("dataflow_sanitizer",
-            LangOpts.Sanitize.has(SanitizerKind::DataFlow))
-      .Case("efficiency_sanitizer",
-            LangOpts.Sanitize.hasOneOf(SanitizerKind::Efficiency))
-      .Case("scudo", LangOpts.Sanitize.hasOneOf(SanitizerKind::Scudo))
-      // Objective-C features
-      .Case("objc_arr", LangOpts.ObjCAutoRefCount) // FIXME: REMOVE?
-      .Case("objc_arc", LangOpts.ObjCAutoRefCount)
-      .Case("objc_arc_weak", LangOpts.ObjCWeak)
-      .Case("objc_default_synthesize_properties", LangOpts.ObjC2)
-      .Case("objc_fixed_enum", LangOpts.ObjC2)
-      .Case("objc_instancetype", LangOpts.ObjC2)
-      .Case("objc_kindof", LangOpts.ObjC2)
-      .Case("objc_modules", LangOpts.ObjC2 && LangOpts.Modules)
-      .Case("objc_nonfragile_abi", LangOpts.ObjCRuntime.isNonFragile())
-      .Case("objc_property_explicit_atomic",
-            true) // Does clang support explicit "atomic" keyword?
-      .Case("objc_protocol_qualifier_mangling", true)
-      .Case("objc_weak_class", LangOpts.ObjCRuntime.hasWeakClassImport())
-      .Case("ownership_holds", true)
-      .Case("ownership_returns", true)
-      .Case("ownership_takes", true)
-      .Case("objc_bool", true)
-      .Case("objc_subscripting", LangOpts.ObjCRuntime.isNonFragile())
-      .Case("objc_array_literals", LangOpts.ObjC2)
-      .Case("objc_dictionary_literals", LangOpts.ObjC2)
-      .Case("objc_boxed_expressions", LangOpts.ObjC2)
-      .Case("objc_boxed_nsvalue_expressions", LangOpts.ObjC2)
-      .Case("arc_cf_code_audited", true)
-      .Case("objc_bridge_id", true)
-      .Case("objc_bridge_id_on_typedefs", true)
-      .Case("objc_generics", LangOpts.ObjC2)
-      .Case("objc_generics_variance", LangOpts.ObjC2)
-      .Case("objc_class_property", LangOpts.ObjC2)
-      // C11 features
-      .Case("c_alignas", LangOpts.C11)
-      .Case("c_alignof", LangOpts.C11)
-      .Case("c_atomic", LangOpts.C11)
-      .Case("c_generic_selections", LangOpts.C11)
-      .Case("c_static_assert", LangOpts.C11)
-      .Case("c_thread_local",
-            LangOpts.C11 && PP.getTargetInfo().isTLSSupported())
-      // C++11 features
-      .Case("cxx_access_control_sfinae", LangOpts.CPlusPlus11)
-      .Case("cxx_alias_templates", LangOpts.CPlusPlus11)
-      .Case("cxx_alignas", LangOpts.CPlusPlus11)
-      .Case("cxx_alignof", LangOpts.CPlusPlus11)
-      .Case("cxx_atomic", LangOpts.CPlusPlus11)
-      .Case("cxx_attributes", LangOpts.CPlusPlus11)
-      .Case("cxx_auto_type", LangOpts.CPlusPlus11)
-      .Case("cxx_constexpr", LangOpts.CPlusPlus11)
-      .Case("cxx_constexpr_string_builtins", LangOpts.CPlusPlus11)
-      .Case("cxx_decltype", LangOpts.CPlusPlus11)
-      .Case("cxx_decltype_incomplete_return_types", LangOpts.CPlusPlus11)
-      .Case("cxx_default_function_template_args", LangOpts.CPlusPlus11)
-      .Case("cxx_defaulted_functions", LangOpts.CPlusPlus11)
-      .Case("cxx_delegating_constructors", LangOpts.CPlusPlus11)
-      .Case("cxx_deleted_functions", LangOpts.CPlusPlus11)
-      .Case("cxx_explicit_conversions", LangOpts.CPlusPlus11)
-      .Case("cxx_generalized_initializers", LangOpts.CPlusPlus11)
-      .Case("cxx_implicit_moves", LangOpts.CPlusPlus11)
-      .Case("cxx_inheriting_constructors", LangOpts.CPlusPlus11)
-      .Case("cxx_inline_namespaces", LangOpts.CPlusPlus11)
-      .Case("cxx_lambdas", LangOpts.CPlusPlus11)
-      .Case("cxx_local_type_template_args", LangOpts.CPlusPlus11)
-      .Case("cxx_nonstatic_member_init", LangOpts.CPlusPlus11)
-      .Case("cxx_noexcept", LangOpts.CPlusPlus11)
-      .Case("cxx_nullptr", LangOpts.CPlusPlus11)
-      .Case("cxx_override_control", LangOpts.CPlusPlus11)
-      .Case("cxx_range_for", LangOpts.CPlusPlus11)
-      .Case("cxx_raw_string_literals", LangOpts.CPlusPlus11)
-      .Case("cxx_reference_qualified_functions", LangOpts.CPlusPlus11)
-      .Case("cxx_rvalue_references", LangOpts.CPlusPlus11)
-      .Case("cxx_strong_enums", LangOpts.CPlusPlus11)
-      .Case("cxx_static_assert", LangOpts.CPlusPlus11)
-      .Case("cxx_thread_local",
-            LangOpts.CPlusPlus11 && PP.getTargetInfo().isTLSSupported())
-      .Case("cxx_trailing_return", LangOpts.CPlusPlus11)
-      .Case("cxx_unicode_literals", LangOpts.CPlusPlus11)
-      .Case("cxx_unrestricted_unions", LangOpts.CPlusPlus11)
-      .Case("cxx_user_literals", LangOpts.CPlusPlus11)
-      .Case("cxx_variadic_templates", LangOpts.CPlusPlus11)
-      // C++14 features
-      .Case("cxx_aggregate_nsdmi", LangOpts.CPlusPlus14)
-      .Case("cxx_binary_literals", LangOpts.CPlusPlus14)
-      .Case("cxx_contextual_conversions", LangOpts.CPlusPlus14)
-      .Case("cxx_decltype_auto", LangOpts.CPlusPlus14)
-      .Case("cxx_generic_lambdas", LangOpts.CPlusPlus14)
-      .Case("cxx_init_captures", LangOpts.CPlusPlus14)
-      .Case("cxx_relaxed_constexpr", LangOpts.CPlusPlus14)
-      .Case("cxx_return_type_deduction", LangOpts.CPlusPlus14)
-      .Case("cxx_variable_templates", LangOpts.CPlusPlus14)
-      // NOTE: For features covered by SD-6, it is preferable to provide *only*
-      // the SD-6 macro and not a __has_feature check.
-
-      // C++ TSes
-      //.Case("cxx_runtime_arrays", LangOpts.CPlusPlusTSArrays)
-      //.Case("cxx_concepts", LangOpts.CPlusPlusTSConcepts)
-      // FIXME: Should this be __has_feature or __has_extension?
-      //.Case("raw_invocation_type", LangOpts.CPlusPlus)
-      // Type traits
-      // N.B. Additional type traits should not be added to the following list.
-      // Instead, they should be detected by has_extension.
-      .Case("has_nothrow_assign", LangOpts.CPlusPlus)
-      .Case("has_nothrow_copy", LangOpts.CPlusPlus)
-      .Case("has_nothrow_constructor", LangOpts.CPlusPlus)
-      .Case("has_trivial_assign", LangOpts.CPlusPlus)
-      .Case("has_trivial_copy", LangOpts.CPlusPlus)
-      .Case("has_trivial_constructor", LangOpts.CPlusPlus)
-      .Case("has_trivial_destructor", LangOpts.CPlusPlus)
-      .Case("has_virtual_destructor", LangOpts.CPlusPlus)
-      .Case("is_abstract", LangOpts.CPlusPlus)
-      .Case("is_base_of", LangOpts.CPlusPlus)
-      .Case("is_class", LangOpts.CPlusPlus)
-      .Case("is_constructible", LangOpts.CPlusPlus)
-      .Case("is_convertible_to", LangOpts.CPlusPlus)
-      .Case("is_empty", LangOpts.CPlusPlus)
-      .Case("is_enum", LangOpts.CPlusPlus)
-      .Case("is_final", LangOpts.CPlusPlus)
-      .Case("is_literal", LangOpts.CPlusPlus)
-      .Case("is_standard_layout", LangOpts.CPlusPlus)
-      .Case("is_pod", LangOpts.CPlusPlus)
-      .Case("is_polymorphic", LangOpts.CPlusPlus)
-      .Case("is_sealed", LangOpts.CPlusPlus && LangOpts.MicrosoftExt)
-      .Case("is_trivial", LangOpts.CPlusPlus)
-      .Case("is_trivially_assignable", LangOpts.CPlusPlus)
-      .Case("is_trivially_constructible", LangOpts.CPlusPlus)
-      .Case("is_trivially_copyable", LangOpts.CPlusPlus)
-      .Case("is_union", LangOpts.CPlusPlus)
-      .Case("modules", LangOpts.Modules)
-      .Case("safe_stack", LangOpts.Sanitize.has(SanitizerKind::SafeStack))
-      .Case("tls", PP.getTargetInfo().isTLSSupported())
-      .Case("underlying_type", LangOpts.CPlusPlus)
+#include "clang/Basic/Features.def"
       .Default(false);
+#undef FEATURE
 }
 
 /// HasExtension - Return true if we recognize and implement the feature
@@ -1299,35 +1126,13 @@ static bool HasExtension(const Preprocessor &PP, StringRef Extension) {
       Extension.size() >= 4)
     Extension = Extension.substr(2, Extension.size() - 4);
 
-  // Because we inherit the feature list from HasFeature, this string switch
-  // must be less restrictive than HasFeature's.
+    // Because we inherit the feature list from HasFeature, this string switch
+    // must be less restrictive than HasFeature's.
+#define EXTENSION(Name, Predicate) .Case(#Name, Predicate)
   return llvm::StringSwitch<bool>(Extension)
-           // C11 features supported by other languages as extensions.
-           .Case("c_alignas", true)
-           .Case("c_alignof", true)
-           .Case("c_atomic", true)
-           .Case("c_generic_selections", true)
-           .Case("c_static_assert", true)
-           .Case("c_thread_local", PP.getTargetInfo().isTLSSupported())
-           // C++11 features supported by other languages as extensions.
-           .Case("cxx_atomic", LangOpts.CPlusPlus)
-           .Case("cxx_deleted_functions", LangOpts.CPlusPlus)
-           .Case("cxx_explicit_conversions", LangOpts.CPlusPlus)
-           .Case("cxx_inline_namespaces", LangOpts.CPlusPlus)
-           .Case("cxx_local_type_template_args", LangOpts.CPlusPlus)
-           .Case("cxx_nonstatic_member_init", LangOpts.CPlusPlus)
-           .Case("cxx_override_control", LangOpts.CPlusPlus)
-           .Case("cxx_range_for", LangOpts.CPlusPlus)
-           .Case("cxx_reference_qualified_functions", LangOpts.CPlusPlus)
-           .Case("cxx_rvalue_references", LangOpts.CPlusPlus)
-           .Case("cxx_variadic_templates", LangOpts.CPlusPlus)
-           // C++14 features supported by other languages as extensions.
-           .Case("cxx_binary_literals", true)
-           .Case("cxx_init_captures", LangOpts.CPlusPlus11)
-           .Case("cxx_variable_templates", LangOpts.CPlusPlus)
-           // Miscellaneous language extensions
-           .Case("overloadable_unmarked", true)
-           .Default(false);
+#include "clang/Basic/Features.def"
+      .Default(false);
+#undef EXTENSION
 }
 
 /// EvaluateHasIncludeCommon - Process a '__has_include("path")'
@@ -1343,7 +1148,7 @@ static bool EvaluateHasIncludeCommon(Token &Tok,
 
   // These expressions are only allowed within a preprocessor directive.
   if (!PP.isParsingIfOrElifDirective()) {
-    PP.Diag(LParenLoc, diag::err_pp_directive_required) << II->getName();
+    PP.Diag(LParenLoc, diag::err_pp_directive_required) << II;
     // Return a valid identifier token.
     assert(Tok.is(tok::identifier));
     Tok.setIdentifierInfo(II);
@@ -1482,7 +1287,7 @@ static bool EvaluateHasIncludeNext(Token &Tok,
   return EvaluateHasIncludeCommon(Tok, II, PP, Lookup, LookupFromFile);
 }
 
-/// \brief Process single-argument builtin feature-like macros that return
+/// Process single-argument builtin feature-like macros that return
 /// integer values.
 static void EvaluateFeatureLikeBuiltinMacro(llvm::raw_svector_ostream& OS,
                                             Token &Tok, IdentifierInfo *II,
@@ -1585,7 +1390,7 @@ already_lexed:
   }
 }
 
-/// \brief Helper function to return the IdentifierInfo structure of a Token
+/// Helper function to return the IdentifierInfo structure of a Token
 /// or generate a diagnostic if none available.
 static IdentifierInfo *ExpectFeatureIdentifierInfo(Token &Tok,
                                                    Preprocessor &PP,
@@ -1686,7 +1491,7 @@ void Preprocessor::ExpandBuiltinMacro(Token &Tok) {
     // can matter for a function-like macro that expands to contain __LINE__.
     // Skip down through expansion points until we find a file loc for the
     // end of the expansion history.
-    Loc = SourceMgr.getExpansionRange(Loc).second;
+    Loc = SourceMgr.getExpansionRange(Loc).getEnd();
     PresumedLoc PLoc = SourceMgr.getPresumedLoc(Loc);
 
     // __LINE__ expands to a simple numeric value.
@@ -1800,12 +1605,21 @@ void Preprocessor::ExpandBuiltinMacro(Token &Tok) {
       [this](Token &Tok, bool &HasLexedNextToken) -> int {
         IdentifierInfo *II = ExpectFeatureIdentifierInfo(Tok, *this,
                                            diag::err_feature_check_malformed);
+        const LangOptions &LangOpts = getLangOpts();
         if (!II)
           return false;
-        else if (II->getBuiltinID() != 0)
+        else if (II->getBuiltinID() != 0) {
+          switch (II->getBuiltinID()) {
+          case Builtin::BI__builtin_operator_new:
+          case Builtin::BI__builtin_operator_delete:
+            // denotes date of behavior change to support calling arbitrary
+            // usual allocation and deallocation functions. Required by libc++
+            return 201802;
+          default:
+            return true;
+          }
           return true;
-        else {
-          const LangOptions &LangOpts = getLangOpts();
+        } else {
           return llvm::StringSwitch<bool>(II->getName())
                       .Case("__make_integer_seq", LangOpts.CPlusPlus)
                       .Case("__type_pack_element", LangOpts.CPlusPlus)
diff --git a/lib/Lex/PTHLexer.cpp b/lib/Lex/PTHLexer.cpp
index d6c20a13d27be..45cff56dcaa11 100644
--- a/lib/Lex/PTHLexer.cpp
+++ b/lib/Lex/PTHLexer.cpp
@@ -23,8 +23,8 @@
 #include "clang/Lex/Preprocessor.h"
 #include "clang/Lex/Token.h"
 #include "llvm/ADT/STLExtras.h"
-#include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringRef.h"
+#include "llvm/Support/DJB.h"
 #include "llvm/Support/Endian.h"
 #include "llvm/Support/ErrorOr.h"
 #include "llvm/Support/FileSystem.h"
@@ -145,7 +145,7 @@ bool PTHLexer::LexEndOfFile(Token &Result) {
     ParsingPreprocessorDirective = false; // Done parsing the "line".
     return true;  // Have a token.
   }
-  
+
   assert(!LexingRawMode);
 
   // If we are in a #if directive, emit an error.
@@ -215,7 +215,7 @@ bool PTHLexer::SkipBlock() {
     // Compute the actual memory address of the '#' token data for this entry.
     HashEntryI = TokBuf + Offset;
 
-    // Optmization: "Sibling jumping".  #if...#else...#endif blocks can
+    // Optimization: "Sibling jumping".  #if...#else...#endif blocks can
     //  contain nested blocks.  In the side-table we can jump over these
     //  nested blocks instead of doing a linear search if the next "sibling"
     //  entry is not at a location greater than LastHashTokPtr.
@@ -336,7 +336,7 @@ public:
   using offset_type = unsigned;
 
   static hash_value_type ComputeHash(internal_key_type x) {
-    return llvm::HashString(x.second);
+    return llvm::djbHash(x.second);
   }
 
   static std::pair<unsigned, unsigned>
@@ -396,7 +396,7 @@ public:
   }
 
   static hash_value_type ComputeHash(const internal_key_type& a) {
-    return llvm::HashString(StringRef(a.first, a.second));
+    return llvm::djbHash(StringRef(a.first, a.second));
   }
 
   // This hopefully will just get inlined and removed by the optimizer.
diff --git a/lib/Lex/Pragma.cpp b/lib/Lex/Pragma.cpp
index b8acd92521fb5..930c5f6b069c8 100644
--- a/lib/Lex/Pragma.cpp
+++ b/lib/Lex/Pragma.cpp
@@ -148,7 +148,7 @@ void Preprocessor::HandlePragmaDirective(SourceLocation IntroducerLoc,
 
 namespace {
 
-/// \brief Helper class for \see Preprocessor::Handle_Pragma.
+/// Helper class for \see Preprocessor::Handle_Pragma.
 class LexingFor_PragmaRAII {
   Preprocessor &PP;
   bool InMacroArgPreExpansion;
@@ -588,7 +588,7 @@ IdentifierInfo *Preprocessor::ParsePragmaPushOrPopMacro(Token &Tok) {
   return LookUpIdentifierInfo(MacroTok);
 }
 
-/// \brief Handle \#pragma push_macro.
+/// Handle \#pragma push_macro.
 ///
 /// The syntax is:
 /// \code
@@ -611,7 +611,7 @@ void Preprocessor::HandlePragmaPushMacro(Token &PushMacroTok) {
   PragmaPushMacroInfo[IdentInfo].push_back(MI);
 }
 
-/// \brief Handle \#pragma pop_macro.
+/// Handle \#pragma pop_macro.
 ///
 /// The syntax is:
 /// \code
@@ -1053,6 +1053,20 @@ struct PragmaDebugHandler : public PragmaHandler {
         PP.Diag(Identifier, diag::warn_pragma_debug_missing_argument)
             << II->getName();
       }
+    } else if (II->isStr("diag_mapping")) {
+      Token DiagName;
+      PP.LexUnexpandedToken(DiagName);
+      if (DiagName.is(tok::eod))
+        PP.getDiagnostics().dump();
+      else if (DiagName.is(tok::string_literal) && !DiagName.hasUDSuffix()) {
+        StringLiteralParser Literal(DiagName, PP);
+        if (Literal.hadError)
+          return;
+        PP.getDiagnostics().dump(Literal.GetString());
+      } else {
+        PP.Diag(DiagName, diag::warn_pragma_debug_missing_argument)
+            << II->getName();
+      }
     } else if (II->isStr("llvm_fatal_error")) {
       llvm::report_fatal_error("#pragma clang __debug llvm_fatal_error");
     } else if (II->isStr("llvm_unreachable")) {
@@ -1601,44 +1615,6 @@ struct PragmaPopMacroHandler : public PragmaHandler {
   }
 };
 
-// Pragma STDC implementations.
-
-/// PragmaSTDC_FENV_ACCESSHandler - "\#pragma STDC FENV_ACCESS ...".
-struct PragmaSTDC_FENV_ACCESSHandler : public PragmaHandler {
-  PragmaSTDC_FENV_ACCESSHandler() : PragmaHandler("FENV_ACCESS") {}
-
-  void HandlePragma(Preprocessor &PP, PragmaIntroducerKind Introducer,
-                    Token &Tok) override {
-    tok::OnOffSwitch OOS;
-    if (PP.LexOnOffSwitch(OOS))
-     return;
-    if (OOS == tok::OOS_ON)
-      PP.Diag(Tok, diag::warn_stdc_fenv_access_not_supported);
-  }
-};
-
-/// PragmaSTDC_CX_LIMITED_RANGEHandler - "\#pragma STDC CX_LIMITED_RANGE ...".
-struct PragmaSTDC_CX_LIMITED_RANGEHandler : public PragmaHandler {
-  PragmaSTDC_CX_LIMITED_RANGEHandler() : PragmaHandler("CX_LIMITED_RANGE") {}
-
-  void HandlePragma(Preprocessor &PP, PragmaIntroducerKind Introducer,
-                    Token &Tok) override {
-    tok::OnOffSwitch OOS;
-    PP.LexOnOffSwitch(OOS);
-  }
-};
-
-/// PragmaSTDC_UnknownHandler - "\#pragma STDC ...".
-struct PragmaSTDC_UnknownHandler : public PragmaHandler {
-  PragmaSTDC_UnknownHandler() = default;
-
-  void HandlePragma(Preprocessor &PP, PragmaIntroducerKind Introducer,
-                    Token &UnknownTok) override {
-    // C99 6.10.6p2, unknown forms are not allowed.
-    PP.Diag(UnknownTok, diag::ext_stdc_pragma_ignored);
-  }
-};
-
 /// PragmaARCCFCodeAuditedHandler - 
 ///   \#pragma clang arc_cf_code_audited begin/end
 struct PragmaARCCFCodeAuditedHandler : public PragmaHandler {
@@ -1754,7 +1730,7 @@ struct PragmaAssumeNonNullHandler : public PragmaHandler {
   }
 };
 
-/// \brief Handle "\#pragma region [...]"
+/// Handle "\#pragma region [...]"
 ///
 /// The syntax is
 /// \code
@@ -1814,17 +1790,15 @@ void Preprocessor::RegisterBuiltinPragmas() {
   ModuleHandler->AddPragma(new PragmaModuleEndHandler());
   ModuleHandler->AddPragma(new PragmaModuleBuildHandler());
   ModuleHandler->AddPragma(new PragmaModuleLoadHandler());
-
-  AddPragmaHandler("STDC", new PragmaSTDC_FENV_ACCESSHandler());
-  AddPragmaHandler("STDC", new PragmaSTDC_CX_LIMITED_RANGEHandler());
-  AddPragmaHandler("STDC", new PragmaSTDC_UnknownHandler());
+    
+  // Add region pragmas.
+  AddPragmaHandler(new PragmaRegionHandler("region"));
+  AddPragmaHandler(new PragmaRegionHandler("endregion"));
 
   // MS extensions.
   if (LangOpts.MicrosoftExt) {
     AddPragmaHandler(new PragmaWarningHandler());
     AddPragmaHandler(new PragmaIncludeAliasHandler());
-    AddPragmaHandler(new PragmaRegionHandler("region"));
-    AddPragmaHandler(new PragmaRegionHandler("endregion"));
   }
 
   // Pragmas added by plugins
@@ -1843,17 +1817,4 @@ void Preprocessor::IgnorePragmas() {
   // in Preprocessor::RegisterBuiltinPragmas().
   AddPragmaHandler("GCC", new EmptyPragmaHandler());
   AddPragmaHandler("clang", new EmptyPragmaHandler());
-  if (PragmaHandler *NS = PragmaHandlers->FindHandler("STDC")) {
-    // Preprocessor::RegisterBuiltinPragmas() already registers
-    // PragmaSTDC_UnknownHandler as the empty handler, so remove it first,
-    // otherwise there will be an assert about a duplicate handler.
-    PragmaNamespace *STDCNamespace = NS->getIfNamespace();
-    assert(STDCNamespace &&
-           "Invalid namespace, registered as a regular pragma handler!");
-    if (PragmaHandler *Existing = STDCNamespace->FindHandler("", false)) {
-      RemovePragmaHandler("STDC", Existing);
-      delete Existing;
-    }
-  }
-  AddPragmaHandler("STDC", new EmptyPragmaHandler());
 }
diff --git a/lib/Lex/PreprocessingRecord.cpp b/lib/Lex/PreprocessingRecord.cpp
index af439dbfa5842..b59820003b56a 100644
--- a/lib/Lex/PreprocessingRecord.cpp
+++ b/lib/Lex/PreprocessingRecord.cpp
@@ -54,7 +54,7 @@ InclusionDirective::InclusionDirective(PreprocessingRecord &PPRec,
 
 PreprocessingRecord::PreprocessingRecord(SourceManager &SM) : SourceMgr(SM) {}
 
-/// \brief Returns a pair of [Begin, End) iterators of preprocessed entities
+/// Returns a pair of [Begin, End) iterators of preprocessed entities
 /// that source range \p Range encompasses.
 llvm::iterator_range<PreprocessingRecord::iterator>
 PreprocessingRecord::getPreprocessedEntitiesInRange(SourceRange Range) {
@@ -88,7 +88,7 @@ static bool isPreprocessedEntityIfInFileID(PreprocessedEntity *PPE, FileID FID,
   return SM.isInFileID(SM.getFileLoc(Loc), FID);
 }
 
-/// \brief Returns true if the preprocessed entity that \arg PPEI iterator
+/// Returns true if the preprocessed entity that \arg PPEI iterator
 /// points to is coming from the file \arg FID.
 ///
 /// Can be used to avoid implicit deserializations of preallocated
@@ -132,7 +132,7 @@ bool PreprocessingRecord::isEntityInFileID(iterator PPEI, FileID FID) {
                                         FID, SourceMgr);
 }
 
-/// \brief Returns a pair of [Begin, End) iterators of preprocessed entities
+/// Returns a pair of [Begin, End) iterators of preprocessed entities
 /// that source range \arg R encompasses.
 std::pair<int, int>
 PreprocessingRecord::getPreprocessedEntitiesInRangeSlow(SourceRange Range) {
@@ -329,12 +329,29 @@ unsigned PreprocessingRecord::allocateLoadedEntities(unsigned NumEntities) {
   return Result;
 }
 
+unsigned PreprocessingRecord::allocateSkippedRanges(unsigned NumRanges) {
+  unsigned Result = SkippedRanges.size();
+  SkippedRanges.resize(SkippedRanges.size() + NumRanges);
+  SkippedRangesAllLoaded = false;
+  return Result;
+}
+
+void PreprocessingRecord::ensureSkippedRangesLoaded() {
+  if (SkippedRangesAllLoaded || !ExternalSource)
+    return;
+  for (unsigned Index = 0; Index != SkippedRanges.size(); ++Index) {
+    if (SkippedRanges[Index].isInvalid())
+      SkippedRanges[Index] = ExternalSource->ReadSkippedRange(Index);
+  }
+  SkippedRangesAllLoaded = true;
+}
+
 void PreprocessingRecord::RegisterMacroDefinition(MacroInfo *Macro,
                                                   MacroDefinitionRecord *Def) {
   MacroDefinitions[Macro] = Def;
 }
 
-/// \brief Retrieve the preprocessed entity at the given ID.
+/// Retrieve the preprocessed entity at the given ID.
 PreprocessedEntity *PreprocessingRecord::getPreprocessedEntity(PPEntityID PPID){
   if (PPID.ID < 0) {
     unsigned Index = -PPID.ID - 1;
@@ -351,7 +368,7 @@ PreprocessedEntity *PreprocessingRecord::getPreprocessedEntity(PPEntityID PPID){
   return PreprocessedEntities[Index];
 }
 
-/// \brief Retrieve the loaded preprocessed entity at the given index.
+/// Retrieve the loaded preprocessed entity at the given index.
 PreprocessedEntity *
 PreprocessingRecord::getLoadedPreprocessedEntity(unsigned Index) {
   assert(Index < LoadedPreprocessedEntities.size() && 
@@ -418,6 +435,7 @@ void PreprocessingRecord::Defined(const Token &MacroNameTok,
 
 void PreprocessingRecord::SourceRangeSkipped(SourceRange Range,
                                              SourceLocation EndifLoc) {
+  assert(Range.isValid());
   SkippedRanges.emplace_back(Range.getBegin(), EndifLoc);
 }
 
@@ -453,7 +471,8 @@ void PreprocessingRecord::InclusionDirective(
     const FileEntry *File,
     StringRef SearchPath,
     StringRef RelativePath,
-    const Module *Imported) {
+    const Module *Imported, 
+    SrcMgr::CharacteristicKind FileType) {
   InclusionDirective::InclusionKind Kind = InclusionDirective::Include;
   
   switch (IncludeTok.getIdentifierInfo()->getPPKeywordID()) {
@@ -497,5 +516,6 @@ size_t PreprocessingRecord::getTotalMemory() const {
   return BumpAlloc.getTotalMemory()
     + llvm::capacity_in_bytes(MacroDefinitions)
     + llvm::capacity_in_bytes(PreprocessedEntities)
-    + llvm::capacity_in_bytes(LoadedPreprocessedEntities);
+    + llvm::capacity_in_bytes(LoadedPreprocessedEntities)
+    + llvm::capacity_in_bytes(SkippedRanges);
 }
diff --git a/lib/Lex/Preprocessor.cpp b/lib/Lex/Preprocessor.cpp
index 7d789e780113c..0217a2e60ede8 100644
--- a/lib/Lex/Preprocessor.cpp
+++ b/lib/Lex/Preprocessor.cpp
@@ -85,12 +85,14 @@ Preprocessor::Preprocessor(std::shared_ptr<PreprocessorOptions> PPOpts,
                            IdentifierInfoLookup *IILookup, bool OwnsHeaders,
                            TranslationUnitKind TUKind)
     : PPOpts(std::move(PPOpts)), Diags(&diags), LangOpts(opts),
-      FileMgr(Headers.getFileMgr()), SourceMgr(SM),
-      PCMCache(PCMCache), ScratchBuf(new ScratchBuffer(SourceMgr)),
-      HeaderInfo(Headers), TheModuleLoader(TheModuleLoader),
-      ExternalSource(nullptr), Identifiers(opts, IILookup),
-      PragmaHandlers(new PragmaNamespace(StringRef())), TUKind(TUKind),
-      SkipMainFilePreamble(0, true),
+      FileMgr(Headers.getFileMgr()), SourceMgr(SM), PCMCache(PCMCache),
+      ScratchBuf(new ScratchBuffer(SourceMgr)), HeaderInfo(Headers),
+      TheModuleLoader(TheModuleLoader), ExternalSource(nullptr),
+      // As the language options may have not been loaded yet (when
+      // deserializing an ASTUnit), adding keywords to the identifier table is
+      // deferred to Preprocessor::Initialize().
+      Identifiers(IILookup), PragmaHandlers(new PragmaNamespace(StringRef())),
+      TUKind(TUKind), SkipMainFilePreamble(0, true),
       CurSubmoduleState(&NullSubmoduleState) {
   OwnsHeaderSearch = OwnsHeaders;
   
@@ -147,6 +149,11 @@ Preprocessor::Preprocessor(std::shared_ptr<PreprocessorOptions> PPOpts,
     Ident_AbnormalTermination = nullptr;
   }
 
+  // If using a PCH with a through header, start skipping tokens.
+  if (!this->PPOpts->PCHThroughHeader.empty() &&
+      !this->PPOpts->ImplicitPCHInclude.empty())
+    SkippingUntilPCHThroughHeader = true;
+
   if (this->PPOpts->GeneratePreamble)
     PreambleConditionalStack.startRecording();
 }
@@ -190,6 +197,9 @@ void Preprocessor::Initialize(const TargetInfo &Target,
   // Initialize information about built-ins.
   BuiltinInfo.InitializeTarget(Target, AuxTarget);
   HeaderInfo.setTarget(Target);
+
+  // Populate the identifier table with info about keywords for the current language.
+  Identifiers.AddKeywords(LangOpts);
 }
 
 void Preprocessor::InitializeForModelFile() {
@@ -328,7 +338,7 @@ Preprocessor::macro_end(bool IncludeExternalMacros) const {
   return CurSubmoduleState->Macros.end();
 }
 
-/// \brief Compares macro tokens with a specified token value sequence.
+/// Compares macro tokens with a specified token value sequence.
 static bool MacroDefinitionEquals(const MacroInfo *MI,
                                   ArrayRef<TokenValue> Tokens) {
   return Tokens.size() == MI->getNumTokens() &&
@@ -482,6 +492,22 @@ void Preprocessor::CreateString(StringRef Str, Token &Tok,
     Tok.setLiteralData(DestPtr);
 }
 
+SourceLocation Preprocessor::SplitToken(SourceLocation Loc, unsigned Length) {
+  auto &SM = getSourceManager();
+  SourceLocation SpellingLoc = SM.getSpellingLoc(Loc);
+  std::pair<FileID, unsigned> LocInfo = SM.getDecomposedLoc(SpellingLoc);
+  bool Invalid = false;
+  StringRef Buffer = SM.getBufferData(LocInfo.first, &Invalid);
+  if (Invalid)
+    return SourceLocation();
+
+  // FIXME: We could consider re-using spelling for tokens we see repeatedly.
+  const char *DestPtr;
+  SourceLocation Spelling =
+      ScratchBuf->getToken(Buffer.data() + LocInfo.second, Length, DestPtr);
+  return SM.createTokenSplitLoc(Spelling, Loc, Loc.getLocWithOffset(Length));
+}
+
 Module *Preprocessor::getCurrentModule() {
   if (!getLangOpts().isCompilingModule())
     return nullptr;
@@ -530,6 +556,72 @@ void Preprocessor::EnterMainSourceFile() {
 
   // Start parsing the predefines.
   EnterSourceFile(FID, nullptr, SourceLocation());
+
+  if (!PPOpts->PCHThroughHeader.empty()) {
+    // Lookup and save the FileID for the through header. If it isn't found
+    // in the search path, it's a fatal error.
+    const DirectoryLookup *CurDir;
+    const FileEntry *File = LookupFile(
+        SourceLocation(), PPOpts->PCHThroughHeader,
+        /*isAngled=*/false, /*FromDir=*/nullptr, /*FromFile=*/nullptr, CurDir,
+        /*SearchPath=*/nullptr, /*RelativePath=*/nullptr,
+        /*SuggestedModule=*/nullptr, /*IsMapped=*/nullptr);
+    if (!File) {
+      Diag(SourceLocation(), diag::err_pp_through_header_not_found)
+          << PPOpts->PCHThroughHeader;
+      return;
+    }
+    setPCHThroughHeaderFileID(
+        SourceMgr.createFileID(File, SourceLocation(), SrcMgr::C_User));
+  }
+
+  // Skip tokens from the Predefines and if needed the main file.
+  if (usingPCHWithThroughHeader() && SkippingUntilPCHThroughHeader)
+    SkipTokensUntilPCHThroughHeader();
+}
+
+void Preprocessor::setPCHThroughHeaderFileID(FileID FID) {
+  assert(PCHThroughHeaderFileID.isInvalid() &&
+         "PCHThroughHeaderFileID already set!");
+  PCHThroughHeaderFileID = FID;
+}
+
+bool Preprocessor::isPCHThroughHeader(const FileEntry *FE) {
+  assert(PCHThroughHeaderFileID.isValid() &&
+         "Invalid PCH through header FileID");
+  return FE == SourceMgr.getFileEntryForID(PCHThroughHeaderFileID);
+}
+
+bool Preprocessor::creatingPCHWithThroughHeader() {
+  return TUKind == TU_Prefix && !PPOpts->PCHThroughHeader.empty() &&
+         PCHThroughHeaderFileID.isValid();
+}
+
+bool Preprocessor::usingPCHWithThroughHeader() {
+  return TUKind != TU_Prefix && !PPOpts->PCHThroughHeader.empty() &&
+         PCHThroughHeaderFileID.isValid();
+}
+
+/// Skip tokens until after the #include of the through header.
+/// Tokens in the predefines file and the main file may be skipped. If the end
+/// of the predefines file is reached, skipping continues into the main file.
+/// If the end of the main file is reached, it's a fatal error.
+void Preprocessor::SkipTokensUntilPCHThroughHeader() {
+  bool ReachedMainFileEOF = false;
+  Token Tok;
+  while (true) {
+    bool InPredefines = (CurLexer->getFileID() == getPredefinesFileID());
+    CurLexer->Lex(Tok);
+    if (Tok.is(tok::eof) && !InPredefines) {
+      ReachedMainFileEOF = true;
+      break;
+    }
+    if (!SkippingUntilPCHThroughHeader)
+      break;
+  }
+  if (ReachedMainFileEOF)
+    Diag(SourceLocation(), diag::err_pp_through_header_not_seen)
+        << PPOpts->PCHThroughHeader << 1;
 }
 
 void Preprocessor::replayPreambleConditionalStack() {
@@ -624,7 +716,7 @@ void Preprocessor::HandlePoisonedIdentifier(Token & Identifier) {
     Diag(Identifier,it->second) << Identifier.getIdentifierInfo();
 }
 
-/// \brief Returns a diagnostic message kind for reporting a future keyword as
+/// Returns a diagnostic message kind for reporting a future keyword as
 /// appropriate for the identifier and specified language.
 static diag::kind getFutureCompatDiagKind(const IdentifierInfo &II,
                                           const LangOptions &LangOpts) {
@@ -773,13 +865,18 @@ void Preprocessor::Lex(Token &Result) {
     }
   } while (!ReturnedToken);
 
-  if (Result.is(tok::code_completion))
+  if (Result.is(tok::code_completion) && Result.getIdentifierInfo()) {
+    // Remember the identifier before code completion token.
     setCodeCompletionIdentifierInfo(Result.getIdentifierInfo());
+    // Set IdenfitierInfo to null to avoid confusing code that handles both
+    // identifiers and completion tokens.
+    Result.setIdentifierInfo(nullptr);
+  }
 
   LastTokenWasAt = Result.is(tok::at);
 }
 
-/// \brief Lex a token following the 'import' contextual keyword.
+/// Lex a token following the 'import' contextual keyword.
 ///
 void Preprocessor::LexAfterModuleImport(Token &Result) {
   // Figure out what kind of lexer we actually have.
diff --git a/lib/Lex/PreprocessorLexer.cpp b/lib/Lex/PreprocessorLexer.cpp
index 2e85f46f52c59..9f930c3a3c6a0 100644
--- a/lib/Lex/PreprocessorLexer.cpp
+++ b/lib/Lex/PreprocessorLexer.cpp
@@ -28,7 +28,7 @@ PreprocessorLexer::PreprocessorLexer(Preprocessor *pp, FileID fid)
     InitialNumSLocEntries = pp->getSourceManager().local_sloc_entry_size();
 }
 
-/// \brief After the preprocessor has parsed a \#include, lex and
+/// After the preprocessor has parsed a \#include, lex and
 /// (potentially) macro expand the filename.
 void PreprocessorLexer::LexIncludeFilename(Token &FilenameTok) {
   assert(ParsingPreprocessorDirective &&
diff --git a/lib/Lex/ScratchBuffer.cpp b/lib/Lex/ScratchBuffer.cpp
index e0f3966fce480..dc03e16daa8b6 100644
--- a/lib/Lex/ScratchBuffer.cpp
+++ b/lib/Lex/ScratchBuffer.cpp
@@ -74,11 +74,11 @@ void ScratchBuffer::AllocScratchBuffer(unsigned RequestLen) {
 
   // Get scratch buffer. Zero-initialize it so it can be dumped into a PCH file
   // deterministically.
-  std::unique_ptr<llvm::MemoryBuffer> OwnBuf =
-      llvm::MemoryBuffer::getNewMemBuffer(RequestLen, "<scratch space>");
-  llvm::MemoryBuffer &Buf = *OwnBuf;
+  std::unique_ptr<llvm::WritableMemoryBuffer> OwnBuf =
+      llvm::WritableMemoryBuffer::getNewMemBuffer(RequestLen,
+                                                  "<scratch space>");
+  CurBuffer = OwnBuf->getBufferStart();
   FileID FID = SourceMgr.createFileID(std::move(OwnBuf));
   BufferStartLoc = SourceMgr.getLocForStartOfFile(FID);
-  CurBuffer = const_cast<char*>(Buf.getBufferStart());
   BytesUsed = 0;
 }
diff --git a/lib/Lex/TokenLexer.cpp b/lib/Lex/TokenLexer.cpp
index d7f1c7a93fdae..184b1b390287a 100644
--- a/lib/Lex/TokenLexer.cpp
+++ b/lib/Lex/TokenLexer.cpp
@@ -483,7 +483,7 @@ void TokenLexer::ExpandFunctionArguments() {
       bool VaArgsPseudoPaste = false;
       // If this is the GNU ", ## __VA_ARGS__" extension, and we just learned
       // that __VA_ARGS__ expands to multiple tokens, avoid a pasting error when
-      // the expander trys to paste ',' with the first token of the __VA_ARGS__
+      // the expander tries to paste ',' with the first token of the __VA_ARGS__
       // expansion.
       if (NonEmptyPasteBefore && ResultToks.size() >= 2 &&
           ResultToks[ResultToks.size()-2].is(tok::comma) &&
@@ -574,7 +574,7 @@ void TokenLexer::ExpandFunctionArguments() {
   }
 }
 
-/// \brief Checks if two tokens form wide string literal.
+/// Checks if two tokens form wide string literal.
 static bool isWideStringLiteralFromMacro(const Token &FirstTok,
                                          const Token &SecondTok) {
   return FirstTok.is(tok::identifier) &&
@@ -865,9 +865,9 @@ bool TokenLexer::pasteTokens(Token &LHSTok, ArrayRef<Token> TokenStream,
     EndLoc = getExpansionLocForMacroDefLoc(EndLoc);
   FileID MacroFID = SM.getFileID(MacroExpansionStart);
   while (SM.getFileID(StartLoc) != MacroFID)
-    StartLoc = SM.getImmediateExpansionRange(StartLoc).first;
+    StartLoc = SM.getImmediateExpansionRange(StartLoc).getBegin();
   while (SM.getFileID(EndLoc) != MacroFID)
-    EndLoc = SM.getImmediateExpansionRange(EndLoc).second;
+    EndLoc = SM.getImmediateExpansionRange(EndLoc).getEnd();
     
   LHSTok.setLocation(SM.createExpansionLoc(LHSTok.getLocation(), StartLoc, EndLoc,
                                         LHSTok.getLength()));
@@ -918,7 +918,7 @@ void TokenLexer::HandleMicrosoftCommentPaste(Token &Tok, SourceLocation OpLoc) {
   PP.HandleMicrosoftCommentPaste(Tok);
 }
 
-/// \brief If \arg loc is a file ID and points inside the current macro
+/// If \arg loc is a file ID and points inside the current macro
 /// definition, returns the appropriate source location pointing at the
 /// macro expansion source location entry, otherwise it returns an invalid
 /// SourceLocation.
@@ -937,7 +937,7 @@ TokenLexer::getExpansionLocForMacroDefLoc(SourceLocation loc) const {
   return MacroExpansionStart.getLocWithOffset(relativeOffset);
 }
 
-/// \brief Finds the tokens that are consecutive (from the same FileID)
+/// Finds the tokens that are consecutive (from the same FileID)
 /// creates a single SLocEntry, and assigns SourceLocations to each token that
 /// point to that SLocEntry. e.g for
 ///   assert(foo == bar);
@@ -1007,7 +1007,7 @@ static void updateConsecutiveMacroArgTokens(SourceManager &SM,
   }
 }
 
-/// \brief Creates SLocEntries and updates the locations of macro argument
+/// Creates SLocEntries and updates the locations of macro argument
 /// tokens to their new expanded locations.
 ///
 /// \param ArgIdSpellLoc the location of the macro argument id inside the macro