Index: lib/Format/TokenAnnotator.cpp
===================================================================
--- lib/Format/TokenAnnotator.cpp
+++ lib/Format/TokenAnnotator.cpp
@@ -1711,6 +1711,10 @@
   return true;
 }
 
+static bool noPrecedingWhitespace(const FormatToken &Tok) {
+  return Tok.WhitespaceRange.getBegin() == Tok.WhitespaceRange.getEnd();
+}
+
 bool TokenAnnotator::spaceRequiredBefore(const AnnotatedLine &Line,
                                          const FormatToken &Right) {
   const FormatToken &Left = *Right.Previous;
@@ -1792,6 +1796,26 @@
              Left.isOneOf(TT_TemplateCloser, TT_TemplateOpener));
   if ((Left.is(TT_TemplateOpener)) != (Right.is(TT_TemplateCloser)))
     return Style.SpacesInAngles;
+  // No space needed between "<<" and "<" in "<<<".
+  if (Left.is(tok::lessless) && Right.is(tok::less) &&
+      noPrecedingWhitespace(Right))
+    return false;
+  // No space needed between identifier and "<<<". This avoids changing "f<<<"
+  // to "f <<<"
+  if (Left.Tok.getIdentifierInfo() && Right.is(tok::lessless) && Right.Next &&
+      Right.Next->is(tok::less) && noPrecedingWhitespace(*Right.Next))
+    return false;
+  // No space needed between ">" and "<<<". Avoids changing "f<t><<<" to
+  // "f<t> <<<".
+  if (Left.is(tok::greater) && Right.is(tok::lessless) && Right.Next &&
+      Right.Next->is(tok::less) && noPrecedingWhitespace(*Right.Next))
+    return false;
+  // No space needed between ">>>" and "("
+  if (Right.is(tok::l_paren) && Left.is(tok::greater) && Left.Previous &&
+      Left.Previous->is(tok::greater) && Left.Previous->Previous &&
+      Left.Previous->Previous->is(tok::greater) &&
+      noPrecedingWhitespace(Left) && noPrecedingWhitespace(*Left.Previous))
+    return false;
   if ((Right.is(TT_BinaryOperator) && !Left.is(tok::l_paren)) ||
       Left.isOneOf(TT_BinaryOperator, TT_ConditionalExpr))
     return true;
Index: unittests/Format/FormatTest.cpp
===================================================================
--- unittests/Format/FormatTest.cpp
+++ unittests/Format/FormatTest.cpp
@@ -9613,6 +9613,15 @@
   verifyFormat("A<A<int>>();", Spaces);
 }
 
+TEST_F(FormatTest, TrippleAngleBraces) {
+  verifyFormat("f<<<1, 1>>>();");
+  EXPECT_EQ("f<<<1, 1>>>();",
+            format("f <<< 1, 1 >>> ();"));
+  verifyFormat("f<param><<<1, 1>>>();");
+  EXPECT_EQ("f<param><<<1, 1>>>();",
+            format("f< param > <<< 1, 1 >>> ();"));
+}
+
 TEST_F(FormatTest, HandleUnbalancedImplicitBracesAcrossPPBranches) {
   std::string code = "#if A\n"
                      "#if B\n"