Index: lib/Format/Format.cpp
===================================================================
--- lib/Format/Format.cpp
+++ lib/Format/Format.cpp
@@ -109,10 +109,8 @@
   }
 };
 
-template <>
-struct ScalarEnumerationTraits<FormatStyle::PointerAlignmentStyle> {
-  static void enumeration(IO &IO,
-                          FormatStyle::PointerAlignmentStyle &Value) {
+template <> struct ScalarEnumerationTraits<FormatStyle::PointerAlignmentStyle> {
+  static void enumeration(IO &IO, FormatStyle::PointerAlignmentStyle &Value) {
     IO.enumCase(Value, "Middle", FormatStyle::PAS_Middle);
     IO.enumCase(Value, "Left", FormatStyle::PAS_Left);
     IO.enumCase(Value, "Right", FormatStyle::PAS_Right);
@@ -144,8 +142,8 @@
     IO.mapOptional("Language", Style.Language);
 
     if (IO.outputting()) {
-      StringRef StylesArray[] = { "LLVM",    "Google", "Chromium",
-                                  "Mozilla", "WebKit", "GNU" };
+      StringRef StylesArray[] = {"LLVM",    "Google", "Chromium",
+                                 "Mozilla", "WebKit", "GNU"};
       ArrayRef<StringRef> Styles(StylesArray);
       for (size_t i = 0, e = Styles.size(); i < e; ++i) {
         StringRef StyleName(Styles[i]);
@@ -273,7 +271,7 @@
 // will be used to get default values for missing keys.
 // If the first element has no Language specified, it will be treated as the
 // default one for the following elements.
-template <> struct DocumentListTraits<std::vector<FormatStyle> > {
+template <> struct DocumentListTraits<std::vector<FormatStyle>> {
   static size_t size(IO &IO, std::vector<FormatStyle> &Seq) {
     return Seq.size();
   }
@@ -600,10 +598,10 @@
   FormatTokenLexer(SourceManager &SourceMgr, FileID ID, FormatStyle &Style,
                    encoding::Encoding Encoding)
       : FormatTok(nullptr), IsFirstToken(true), GreaterStashed(false),
-        Column(0), TrailingWhitespace(0), SourceMgr(SourceMgr), ID(ID),
-        Style(Style), IdentTable(getFormattingLangOpts(Style)),
-        Keywords(IdentTable), Encoding(Encoding), FirstInLineIndex(0),
-        FormattingDisabled(false) {
+        LessStashed(false), Column(0), TrailingWhitespace(0),
+        SourceMgr(SourceMgr), ID(ID), Style(Style),
+        IdentTable(getFormattingLangOpts(Style)), Keywords(IdentTable),
+        Encoding(Encoding), FirstInLineIndex(0), FormattingDisabled(false) {
     Lex.reset(new Lexer(ID, SourceMgr.getBuffer(ID), SourceMgr,
                         getFormattingLangOpts(Style)));
     Lex->SetKeepWhitespaceMode(true);
@@ -633,6 +631,8 @@
       return;
     if (tryMergeConflictMarkers())
       return;
+    if (tryMergeLessLess())
+      return;
 
     if (Style.Language == FormatStyle::LK_JavaScript) {
       if (tryMergeJSRegexLiteral())
@@ -640,11 +640,11 @@
       if (tryMergeEscapeSequence())
         return;
 
-      static tok::TokenKind JSIdentity[] = { tok::equalequal, tok::equal };
-      static tok::TokenKind JSNotIdentity[] = { tok::exclaimequal, tok::equal };
-      static tok::TokenKind JSShiftEqual[] = { tok::greater, tok::greater,
-                                               tok::greaterequal };
-      static tok::TokenKind JSRightArrow[] = { tok::equal, tok::greater };
+      static tok::TokenKind JSIdentity[] = {tok::equalequal, tok::equal};
+      static tok::TokenKind JSNotIdentity[] = {tok::exclaimequal, tok::equal};
+      static tok::TokenKind JSShiftEqual[] = {tok::greater, tok::greater,
+                                              tok::greaterequal};
+      static tok::TokenKind JSRightArrow[] = {tok::equal, tok::greater};
       // FIXME: We probably need to change token type to mimic operator with the
       // correct priority.
       if (tryMergeTokens(JSIdentity))
@@ -658,6 +658,43 @@
     }
   }
 
+  bool tryMergeLessLess() {
+    // Merge X,less,less,Y into X,lessless,Y unless X or Y is less.
+    if (Tokens.size() < 4) {
+      // Merge <,<,eof to <<,eof
+      if (Tokens.back()->Tok.is(tok::eof)) {
+        auto &eof = Tokens.back();
+        Tokens.pop_back();
+        static tok::TokenKind LessLess[] = {tok::less, tok::less};
+        if (tryMergeTokens(LessLess)) {
+          Tokens.back()->Tok.setKind(tok::lessless);
+          Tokens.push_back(eof);
+          return true;
+        }
+        Tokens.push_back(eof);
+        return false;
+      }
+
+      return false;
+    }
+
+    SmallVectorImpl<FormatToken *>::const_iterator First = Tokens.end() - 4;
+    if (First[3]->is(tok::less) || First[2]->isNot(tok::less) ||
+        First[1]->isNot(tok::less) || First[0]->is(tok::less))
+      return false;
+
+    // Only merge if there currently is no whitespace between the two "<".
+    if (First[2]->WhitespaceRange.getBegin() !=
+        First[2]->WhitespaceRange.getEnd())
+      return false;
+
+    First[1]->Tok.setKind(tok::lessless);
+    First[1]->TokenText = "<<";
+    First[1]->ColumnWidth += 1;
+    Tokens.erase(Tokens.end() - 2);
+    return true;
+  }
+
   bool tryMergeTokens(ArrayRef<tok::TokenKind> Kinds) {
     if (Tokens.size() < Kinds.size())
       return false;
@@ -668,8 +705,9 @@
       return false;
     unsigned AddLength = 0;
     for (unsigned i = 1; i < Kinds.size(); ++i) {
-      if (!First[i]->is(Kinds[i]) || First[i]->WhitespaceRange.getBegin() !=
-                                         First[i]->WhitespaceRange.getEnd())
+      if (!First[i]->is(Kinds[i]) ||
+          First[i]->WhitespaceRange.getBegin() !=
+              First[i]->WhitespaceRange.getEnd())
         return false;
       AddLength += First[i]->TokenText.size();
     }
@@ -842,22 +880,31 @@
     return false;
   }
 
+  FormatToken *getStashedToken() {
+    // Create a synthesized second '>' or '<' token.
+    Token Tok = FormatTok->Tok;
+    StringRef TokenText = FormatTok->TokenText;
+
+    unsigned OriginalColumn = FormatTok->OriginalColumn;
+    FormatTok = new (Allocator.Allocate()) FormatToken;
+    FormatTok->Tok = Tok;
+    SourceLocation TokLocation =
+        FormatTok->Tok.getLocation().getLocWithOffset(1);
+    FormatTok->WhitespaceRange = SourceRange(TokLocation, TokLocation);
+    FormatTok->TokenText = TokenText;
+    FormatTok->ColumnWidth = 1;
+    FormatTok->OriginalColumn = OriginalColumn;
+    return FormatTok;
+  }
+
   FormatToken *getNextToken() {
     if (GreaterStashed) {
-      // Create a synthesized second '>' token.
-      Token Greater = FormatTok->Tok;
-      unsigned OriginalColumn = FormatTok->OriginalColumn;
-      FormatTok = new (Allocator.Allocate()) FormatToken;
-      FormatTok->Tok = Greater;
-      SourceLocation GreaterLocation =
-          FormatTok->Tok.getLocation().getLocWithOffset(1);
-      FormatTok->WhitespaceRange =
-          SourceRange(GreaterLocation, GreaterLocation);
-      FormatTok->TokenText = ">";
-      FormatTok->ColumnWidth = 1;
-      FormatTok->OriginalColumn = OriginalColumn;
       GreaterStashed = false;
-      return FormatTok;
+      return getStashedToken();
+    }
+    if (LessStashed) {
+      LessStashed = false;
+      return getStashedToken();
     }
 
     FormatTok = new (Allocator.Allocate()) FormatToken;
@@ -952,6 +999,10 @@
       FormatTok->Tok.setKind(tok::greater);
       FormatTok->TokenText = FormatTok->TokenText.substr(0, 1);
       GreaterStashed = true;
+    } else if (FormatTok->Tok.is(tok::lessless)) {
+      FormatTok->Tok.setKind(tok::less);
+      FormatTok->TokenText = FormatTok->TokenText.substr(0, 1);
+      LessStashed = true;
     }
 
     // Now FormatTok is the next non-whitespace token.
@@ -988,7 +1039,7 @@
 
   FormatToken *FormatTok;
   bool IsFirstToken;
-  bool GreaterStashed;
+  bool GreaterStashed, LessStashed;
   unsigned Column;
   unsigned TrailingWhitespace;
   std::unique_ptr<Lexer> Lex;
Index: lib/Format/TokenAnnotator.cpp
===================================================================
--- lib/Format/TokenAnnotator.cpp
+++ lib/Format/TokenAnnotator.cpp
@@ -902,7 +902,7 @@
       return false;
 
     if (Tok.Previous->is(TT_LeadingJavaAnnotation))
-        return false;
+      return false;
 
     // Skip "const" as it does not have an influence on whether this is a name.
     FormatToken *PreviousNotConst = Tok.Previous;
@@ -2024,8 +2024,8 @@
   if (Right.is(TT_CtorInitializerComma) &&
       Style.BreakConstructorInitializersBeforeComma)
     return true;
-  if (Left.is(tok::greater) && Right.is(tok::greater) &&
-      Left.isNot(TT_TemplateCloser))
+  if ((Left.is(tok::greater) && Right.is(tok::greater)) ||
+      (Left.is(tok::less) && Right.is(tok::less)))
     return false;
   if (Right.is(TT_BinaryOperator) &&
       Style.BreakBeforeBinaryOperators != FormatStyle::BOS_None &&
Index: unittests/Format/FormatTest.cpp
===================================================================
--- unittests/Format/FormatTest.cpp
+++ unittests/Format/FormatTest.cpp
@@ -9737,6 +9737,27 @@
   verifyFormat("A<A<int>>();", Spaces);
 }
 
+TEST_F(FormatTest, TripleAngleBrackets) {
+  verifyFormat("f<<<1, 1>>>();");
+  verifyFormat("f<<<1, 1, 1, s>>>();");
+  verifyFormat("f<<<a, b, c, d>>>();");
+  EXPECT_EQ("f<<<1, 1>>>();",
+            format("f <<< 1, 1 >>> ();"));
+  verifyFormat("f<param><<<1, 1>>>();");
+  verifyFormat("f<1><<<1, 1>>>();");
+  EXPECT_EQ("f<param><<<1, 1>>>();",
+            format("f< param > <<< 1, 1 >>> ();"));
+  verifyFormat("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
+               "aaaaaaaaaaa<<<\n    1, 1>>>();");
+}
+
+TEST_F(FormatTest, MergeLessLessAtEnd) {
+  verifyFormat("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
+               "aaallvm::outs() <<");
+  verifyFormat("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
+               "aaaallvm::outs()\n    <<");
+}
+
 TEST_F(FormatTest, HandleUnbalancedImplicitBracesAcrossPPBranches) {
   std::string code = "#if A\n"
                      "#if B\n"