Index: lib/Format/ContinuationIndenter.cpp
===================================================================
--- lib/Format/ContinuationIndenter.cpp
+++ lib/Format/ContinuationIndenter.cpp
@@ -1599,12 +1599,10 @@
     // FIXME: Store Prefix and Suffix (or PrefixLength and SuffixLength to
     // reduce the overhead) for each FormatToken, which is a string, so that we
     // don't run multiple checks here on the hot path.
-    if ((Text.endswith(Postfix = "\"") &&
-         (Text.startswith(Prefix = "@\"") || Text.startswith(Prefix = "\"") ||
-          Text.startswith(Prefix = "u\"") || Text.startswith(Prefix = "U\"") ||
-          Text.startswith(Prefix = "u8\"") ||
-          Text.startswith(Prefix = "L\""))) ||
-        (Text.startswith(Prefix = "_T(\"") && Text.endswith(Postfix = "\")"))) {
+    if (Text.endswith(Postfix = "\"") &&
+        (Text.startswith(Prefix = "@\"") || Text.startswith(Prefix = "\"") ||
+         Text.startswith(Prefix = "u\"") || Text.startswith(Prefix = "U\"") ||
+         Text.startswith(Prefix = "u8\"") || Text.startswith(Prefix = "L\""))) {
       // We need this to address the case where there is an unbreakable tail
       // only if certain other formatting decisions have been taken. The
       // UnbreakableTailLength of Current is an overapproximation is that case
@@ -1616,6 +1614,25 @@
           Current, StartColumn, Prefix, Postfix, UnbreakableTailLength,
           State.Line->InPPDirective, Encoding, Style);
     }
+    if (Current.TMacroStringLiteral && Text.endswith(Postfix = "\")")) {
+      // If we're inside tmacro we know that we have something like _T(" at the
+      // beginning of the literal.
+      size_t pos = Text.find('"');
+      if (pos != StringRef::npos) {
+        Prefix = Text.substr(0, pos + 1);
+
+        // We need this to address the case where there is an unbreakable tail
+        // only if certain other formatting decisions have been taken. The
+        // UnbreakableTailLength of Current is an overapproximation is that case
+        // and we need to be correct here.
+        unsigned UnbreakableTailLength = (State.NextToken && canBreak(State))
+                                             ? 0
+                                             : Current.UnbreakableTailLength;
+        return llvm::make_unique<BreakableStringLiteral>(
+            Current, StartColumn, Prefix, Postfix, UnbreakableTailLength,
+            State.Line->InPPDirective, Encoding, Style);
+      }
+    }
   } else if (Current.is(TT_BlockComment)) {
     if (!Style.ReflowComments ||
         // If a comment token switches formatting, like
Index: lib/Format/FormatToken.h
===================================================================
--- lib/Format/FormatToken.h
+++ lib/Format/FormatToken.h
@@ -134,6 +134,9 @@
   /// Token.
   bool HasUnescapedNewline = false;
 
+  /// \brief Whether this is a string literal similar to _T("sdfsdf").
+  bool TMacroStringLiteral = false;
+
   /// \brief The range of the whitespace immediately preceding the \c Token.
   SourceRange WhitespaceRange;
 
Index: lib/Format/FormatTokenLexer.cpp
===================================================================
--- lib/Format/FormatTokenLexer.cpp
+++ lib/Format/FormatTokenLexer.cpp
@@ -368,7 +368,7 @@
     return false;
 
   FormatToken *Macro = Tokens[Tokens.size() - 4];
-  if (Macro->TokenText != "_T")
+  if (Macro->TokenText.empty() || !String->TokenText.startswith("\"") || !String->TokenText.endswith("\""))
     return false;
 
   const char *Start = Macro->TokenText.data();
@@ -382,6 +382,7 @@
       String->TokenText, String->OriginalColumn, Style.TabWidth, Encoding);
   String->NewlinesBefore = Macro->NewlinesBefore;
   String->HasUnescapedNewline = Macro->HasUnescapedNewline;
+  String->TMacroStringLiteral = true;
 
   Tokens.pop_back();
   Tokens.pop_back();
Index: unittests/Format/FormatTest.cpp
===================================================================
--- unittests/Format/FormatTest.cpp
+++ unittests/Format/FormatTest.cpp
@@ -7935,6 +7935,47 @@
                    "_T(\"XXXXXXXXXXXXXXXXXXXXXXXXXXXXXn\"));"));
 }
 
+TEST_F(FormatTest, BreaksStringLiteralsWithin_GenericTMacro) {
+  FormatStyle Style = getLLVMStyleWithColumns(25);
+  EXPECT_EQ(
+      "blablaT(\"aaaaaaaaaaaaaa\")\n"
+      "blablaT(\"aaaaaaaaaaaaaa\")\n"
+      "blablaT(\"aaaaaaaaaaaa\")",
+      format("  blablaT(\"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\")", Style));
+  EXPECT_EQ("f(x,\n"
+            "  blablaT(\"aaaaaaaaaaaa\")\n"
+            "  blablaT(\"aaa\"),\n"
+            "  z);",
+            format("f(x, blablaT(\"aaaaaaaaaaaaaaa\"), z);", Style));
+
+  // FIXME: Handle embedded spaces in one iteration.
+  //  EXPECT_EQ("blablaT(\"aaaaaaaaaaaaa\")\n"
+  //            "blablaT(\"aaaaaaaaaaaaa\")\n"
+  //            "blablaT(\"aaaaaaaaaaaaa\")\n"
+  //            "blablaT(\"a\")",
+  //            format("  blablaT ( \"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\" )",
+  //                   getLLVMStyleWithColumns(20)));
+  EXPECT_EQ(
+      "blablaT ( \"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\" )",
+      format("  blablaT ( \"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\" )", Style));
+  EXPECT_EQ("f(\n"
+            "#if !TEST\n"
+            "    blablaT(\"XXXXXXXXXXXXXXXXXXXXXXXXXXXXXn\")\n"
+            "#endif\n"
+            ");",
+            format("f(\n"
+                   "#if !TEST\n"
+                   "blablaT(\"XXXXXXXXXXXXXXXXXXXXXXXXXXXXXn\")\n"
+                   "#endif\n"
+                   ");"));
+  EXPECT_EQ("f(\n"
+            "\n"
+            "    blablaT(\"XXXXXXXXXXXXXXXXXXXXXXXXXXXXXn\"));",
+            format("f(\n"
+                   "\n"
+                   "blablaT(\"XXXXXXXXXXXXXXXXXXXXXXXXXXXXXn\"));"));
+}
+
 TEST_F(FormatTest, BreaksStringLiteralOperands) {
   // In a function call with two operands, the second can be broken with no line
   // break before it.