Index: lib/Support/CommandLine.cpp
===================================================================
--- lib/Support/CommandLine.cpp
+++ lib/Support/CommandLine.cpp
@@ -708,6 +708,7 @@
                                 SmallVectorImpl<const char *> &NewArgv,
                                 bool MarkEOLs) {
   SmallString<128> Token;
+  bool NonWhitespaceSeenInLine = false;
   for (size_t I = 0, E = Src.size(); I != E; ++I) {
     // Consume runs of whitespace.
     if (Token.empty()) {
@@ -719,11 +720,27 @@
       }
       if (I == E)
         break;
+      // Skip comment line.
+      if (!NonWhitespaceSeenInLine && Src[I] == '#') {
+        ++I;
+        while (I != E && Src[I] != '\n')
+          ++I;
+        if (I == E)
+          break;
+        continue;
+      }
+      NonWhitespaceSeenInLine = true;
     }
 
     // Backslash escapes the next character.
     if (I + 1 < E && Src[I] == '\\') {
       ++I; // Skip the escape.
+      if (Src[I] == '\n')
+        continue; // Ignore backlash followed by '\n'.
+      if (Src[I] == '\r' && I + 1 < E && Src[I + 1] == '\n') {
+        ++I;
+        continue; // Ignore backlash followed by \r\n.
+      }
       Token.push_back(Src[I]);
       continue;
     }
@@ -748,6 +765,8 @@
       if (!Token.empty())
         NewArgv.push_back(Saver.save(StringRef(Token)).data());
       Token.clear();
+      if (Src[I] == '\n')
+        NonWhitespaceSeenInLine = false;
       continue;
     }
 
@@ -809,6 +828,7 @@
   // This is a small state machine to consume characters until it reaches the
   // end of the source string.
   enum { INIT, UNQUOTED, QUOTED } State = INIT;
+  bool NonWhitespaceSeenInLine = false;
   for (size_t I = 0, E = Src.size(); I != E; ++I) {
     // INIT state indicates that the current input index is at the start of
     // the string or between tokens.
@@ -819,6 +839,18 @@
           NewArgv.push_back(nullptr);
         continue;
       }
+
+      // Skip comment line.
+      if (!NonWhitespaceSeenInLine && Src[I] == '#') {
+        ++I;
+        while (I != E && Src[I] != '\n')
+          ++I;
+        if (I == E)
+          break;
+        continue;
+      }
+      NonWhitespaceSeenInLine = true;
+
       if (Src[I] == '"') {
         State = QUOTED;
         continue;
@@ -841,9 +873,12 @@
         NewArgv.push_back(Saver.save(StringRef(Token)).data());
         Token.clear();
         State = INIT;
-        // Mark the end of lines in response files
-        if (MarkEOLs && Src[I] == '\n')
-          NewArgv.push_back(nullptr);
+        if (Src[I] == '\n') {
+          NonWhitespaceSeenInLine = false;
+          // Mark the end of lines in response files
+          if (MarkEOLs)
+            NewArgv.push_back(nullptr);
+        }
         continue;
       }
       if (Src[I] == '"') {
Index: unittests/Support/CommandLineTest.cpp
===================================================================
--- unittests/Support/CommandLineTest.cpp
+++ unittests/Support/CommandLineTest.cpp
@@ -198,6 +198,56 @@
                            array_lengthof(Output));
 }
 
+TEST(CommandLineTest, TokenizeGNUCommandLineBS) {
+  const char *Input = "\\";
+  const char *Output[1] = { "\\" };
+  testCommandLineTokenizer(cl::TokenizeGNUCommandLine, Input, Output, 1);
+
+  Input = "abc\\";
+  Output[0] = "abc\\";
+  testCommandLineTokenizer(cl::TokenizeGNUCommandLine, Input, Output, 1);
+
+  Input = "\\abc";
+  Output[0] = "abc";
+  testCommandLineTokenizer(cl::TokenizeGNUCommandLine, Input, Output, 1);
+
+  Input = "abc\\123";
+  Output[0] = "abc123";
+  testCommandLineTokenizer(cl::TokenizeGNUCommandLine, Input, Output, 1);
+
+  Input = "abc\\1";
+  Output[0] = "abc1";
+  testCommandLineTokenizer(cl::TokenizeGNUCommandLine, Input, Output, 1);
+
+  Input = "abc\\\\123";
+  Output[0] = "abc\\123";
+  testCommandLineTokenizer(cl::TokenizeGNUCommandLine, Input, Output, 1);
+
+  Input = "\\\nabc";
+  Output[0] = "abc";
+  testCommandLineTokenizer(cl::TokenizeGNUCommandLine, Input, Output, 1);
+
+  Input = "\\\r\nabc";
+  Output[0] = "abc";
+  testCommandLineTokenizer(cl::TokenizeGNUCommandLine, Input, Output, 1);
+
+  Input = "abc\\\n123";
+  Output[0] = "abc123";
+  testCommandLineTokenizer(cl::TokenizeGNUCommandLine, Input, Output, 1);
+
+  Input = "abc\\\r\n123";
+  Output[0] = "abc123";
+  testCommandLineTokenizer(cl::TokenizeGNUCommandLine, Input, Output, 1);
+
+  Input = "abc\\\n";
+  Output[0] = "abc";
+  testCommandLineTokenizer(cl::TokenizeGNUCommandLine, Input, Output, 1);
+
+  Input = "abc\\\r\n";
+  Output[0] = "abc";
+  testCommandLineTokenizer(cl::TokenizeGNUCommandLine, Input, Output, 1);
+}
+
 TEST(CommandLineTest, TokenizeWindowsCommandLine) {
   const char Input[] = "a\\b c\\\\d e\\\\\"f g\" h\\\"i j\\\\\\\"k \"lmn\" o pqr "
                       "\"st \\\"u\" \\v";
@@ -207,6 +257,38 @@
                            array_lengthof(Output));
 }
 
+TEST(CommandLineTest, TokenizeCommandLineComment) {
+  for (auto Tokenizer : { cl::TokenizeGNUCommandLine ,
+                          cl::TokenizeWindowsCommandLine }) {
+    const char *Input = "# abc\n"
+                        "123";
+    const char *Output[3] = { "123" };
+    testCommandLineTokenizer(Tokenizer, Input, Output, 1);
+
+    Input = "  # abc\n"
+            "123";
+    Output[0] = "123";
+    testCommandLineTokenizer(Tokenizer, Input, Output, 1);
+
+    Input = "123 # abc";
+    Output[0] = "123";
+    Output[1] = "#";
+    Output[2] = "abc";
+    testCommandLineTokenizer(Tokenizer, Input, Output, 3);
+
+    Input = "abc\n"
+            "#123";
+    Output[0] = "abc";
+    testCommandLineTokenizer(Tokenizer, Input, Output, 1);
+
+    Input = "abc def\n"
+            "#123";
+    Output[0] = "abc";
+    Output[1] = "def";
+    testCommandLineTokenizer(Tokenizer, Input, Output, 2);
+  }
+}
+
 TEST(CommandLineTest, AliasesWithArguments) {
   static const size_t ARGC = 3;
   const char *const Inputs[][ARGC] = {