Index: docs/TestingGuide.rst
===================================================================
--- docs/TestingGuide.rst
+++ docs/TestingGuide.rst
@@ -129,6 +129,18 @@
 
 to enable testing with valgrind and with leak checking enabled.
 
+Some tests write their outputs directly to the console and the outputs cannot
+be redirected to a file. These tests are disabled by default. In order to run
+the tests which output to console, please include ``--enable-console`` in the
+``LIT_ARGS`` make variable. For example, you can use:
+
+.. code-block:: bash
+
+    % make check LIT_ARGS="-v --enable-console"
+
+to enable testing that output to the console. On the RUN line of the test body,
+you can use ``/dev/tty`` to refer to the console.
+
 To run individual tests or subsets of tests, you can use the ``llvm-lit``
 script which is built as part of LLVM. For example, to run the
 ``Integer/BitPacked.ll`` test by itself you can run:
Index: utils/lit/lit/LitConfig.py
===================================================================
--- utils/lit/lit/LitConfig.py
+++ utils/lit/lit/LitConfig.py
@@ -21,7 +21,7 @@
 
     def __init__(self, progname, path, quiet,
                  useValgrind, valgrindLeakCheck, valgrindArgs,
-                 noExecute, debug, isWindows,
+                 noExecute, debug, enableConsole, isWindows,
                  params, config_prefix = None,
                  maxIndividualTestTime = 0):
         # The name of the test runner.
@@ -34,6 +34,7 @@
         self.valgrindUserArgs = list(valgrindArgs)
         self.noExecute = noExecute
         self.debug = debug
+        self.enableConsole = enableConsole
         self.isWindows = bool(isWindows)
         self.params = dict(params)
         self.bashPath = None
Index: utils/lit/lit/TestRunner.py
===================================================================
--- utils/lit/lit/TestRunner.py
+++ utils/lit/lit/TestRunner.py
@@ -245,6 +245,10 @@
                 if r[2] is None:
                     if kAvoidDevNull and r[0] == '/dev/null':
                         r[2] = tempfile.TemporaryFile(mode=r[1])
+                    elif kIsWindows and r[0] == '/dev/tty':
+                        # Simulate /dev/tty on Windows.
+                        # "CON" is a special filename for the console.
+                        r[2] = open("CON", r[1])
                     else:
                         # Make sure relative paths are relative to the cwd.
                         redir_filename = os.path.join(cmd_shenv.cwd, r[0])
Index: utils/lit/lit/TestingConfig.py
===================================================================
--- utils/lit/lit/TestingConfig.py
+++ utils/lit/lit/TestingConfig.py
@@ -57,6 +57,8 @@
             available_features.append('valgrind')
             if litConfig.valgrindLeakCheck:
                 available_features.append('vg_leak')
+        if litConfig.enableConsole:
+            available_features.append('console')
 
         return TestingConfig(None,
                              name = '<unnamed>',
Index: utils/lit/lit/discovery.py
===================================================================
--- utils/lit/lit/discovery.py
+++ utils/lit/lit/discovery.py
@@ -244,6 +244,7 @@
                                     valgrindArgs = [],
                                     noExecute = False,
                                     debug = False,
+                                    enableConsole = False,
                                     isWindows = (platform.system()=='Windows'),
                                     params = {})
 
Index: utils/lit/lit/main.py
===================================================================
--- utils/lit/lit/main.py
+++ utils/lit/lit/main.py
@@ -229,6 +229,9 @@
                      help=("Only run tests with paths matching the given "
                            "regular expression"),
                      action="store", default=None)
+    group.add_option("", "--enable-console", dest="enableConsole",
+                     help=("Enable tests that output to the console"),
+                     action="store_true", default=None)
     parser.add_option_group(group)
 
     group = OptionGroup(parser, "Debug and Experimental Options")
@@ -297,6 +300,7 @@
         valgrindArgs = opts.valgrindArgs,
         noExecute = opts.noExecute,
         debug = opts.debug,
+        enableConsole = opts.enableConsole,
         isWindows = isWindows,
         params = userParams,
         config_prefix = opts.configPrefix,