Index: lib/Support/CommandLine.cpp
===================================================================
--- lib/Support/CommandLine.cpp
+++ lib/Support/CommandLine.cpp
@@ -515,8 +515,6 @@
 
 static bool isQuote(char C) { return C == '\"' || C == '\''; }
 
-static bool isGNUSpecial(char C) { return strchr("\\\"\' ", C); }
-
 void cl::TokenizeGNUCommandLine(StringRef Src, StringSaver &Saver,
                                 SmallVectorImpl<const char *> &NewArgv,
                                 bool MarkEOLs) {
@@ -534,9 +532,8 @@
         break;
     }
 
-    // Backslashes can escape backslashes, spaces, and other quotes.  Otherwise
-    // they are literal.  This makes it much easier to read Windows file paths.
-    if (I + 1 < E && Src[I] == '\\' && isGNUSpecial(Src[I + 1])) {
+    // Backslashe escapes the next character.
+    if (I + 1 < E && Src[I] == '\\') {
       ++I; // Skip the escape.
       Token.push_back(Src[I]);
       continue;
@@ -546,8 +543,8 @@
     if (isQuote(Src[I])) {
       char Quote = Src[I++];
       while (I != E && Src[I] != Quote) {
-        // Backslashes are literal, unless they escape a special character.
-        if (Src[I] == '\\' && I + 1 != E && isGNUSpecial(Src[I + 1]))
+        // Backslashes escape the next character.
+        if (Src[I] == '\\' && I + 1 != E)
           ++I;
         Token.push_back(Src[I]);
         ++I;
Index: unittests/Support/CommandLineTest.cpp
===================================================================
--- unittests/Support/CommandLineTest.cpp
+++ unittests/Support/CommandLineTest.cpp
@@ -165,11 +165,12 @@
 }
 
 TEST(CommandLineTest, TokenizeGNUCommandLine) {
-  const char *Input = "foo\\ bar \"foo bar\" \'foo bar\' 'foo\\\\bar' "
-                      "foo\"bar\"baz C:\\src\\foo.cpp \"C:\\src\\foo.cpp\"";
-  const char *const Output[] = { "foo bar", "foo bar", "foo bar", "foo\\bar",
-                                 "foobarbaz", "C:\\src\\foo.cpp",
-                                 "C:\\src\\foo.cpp" };
+  const char *Input =
+      "foo\\ bar \"foo bar\" \'foo bar\' 'foo\\\\bar' -DFOO=bar\\(\\) "
+      "foo\"bar\"baz C:\\\\src\\\\foo.cpp \"C:\\\\src\\\\foo.cpp\"";
+  const char *const Output[] = {
+      "foo bar",     "foo bar",   "foo bar",          "foo\\bar",
+      "-DFOO=bar()", "foobarbaz", "C:\\src\\foo.cpp", "C:\\src\\foo.cpp"};
   testCommandLineTokenizer(cl::TokenizeGNUCommandLine, Input, Output,
                            array_lengthof(Output));
 }