Index: lib/Format/ContinuationIndenter.cpp
===================================================================
--- lib/Format/ContinuationIndenter.cpp
+++ lib/Format/ContinuationIndenter.cpp
@@ -958,6 +958,12 @@
         break;
       }
 
+      // When breaking before a tab character, it may be moved by a few columns,
+      // but will still be expanded to the next tab stop, so we don't save any
+      // columns.
+      if (NewRemainingTokenColumns == RemainingTokenColumns)
+        break;
+
       assert(NewRemainingTokenColumns < RemainingTokenColumns);
       if (!DryRun)
         Token->insertBreak(LineIndex, TailOffset, Split, Whitespaces);
Index: unittests/Format/FormatTest.cpp
===================================================================
--- unittests/Format/FormatTest.cpp
+++ unittests/Format/FormatTest.cpp
@@ -6366,7 +6366,7 @@
                    67, 0, getLLVMStyle()));
 }
 
-TEST_F(FormatTest, BreakStringLiterals) {
+TEST_F(FormatTest, BreaksStringLiterals) {
   EXPECT_EQ("\"some text \"\n"
             "\"other\";",
             format("\"some text other\";", getLLVMStyleWithColumns(12)));
@@ -6526,6 +6526,16 @@
       format("#define A \"some text other\";", AlignLeft));
 }
 
+TEST_F(FormatTest, BreaksStringLiteralsWithTabs) {
+  EXPECT_EQ(
+      "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
+      "(\n"
+      "    \"x\t\");",
+      format("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
+             "aaaaaaa("
+             "\"x\t\");"));
+}
+
 TEST_F(FormatTest, BreaksWideAndNSStringLiterals) {
   EXPECT_EQ(
       "u8\"utf8 string \"\n"