Index: test/Unit/lit.cfg
===================================================================
--- test/Unit/lit.cfg
+++ test/Unit/lit.cfg
@@ -12,6 +12,9 @@
 # suffixes: A list of file extensions to treat as test files.
 config.suffixes = []
 
+# is_early; Request to run this suite early.
+config.is_early = True
+
 # test_source_root: The root path where tests are located.
 # test_exec_root: The root path where tests should be run.
 llvm_obj_root = getattr(config, 'llvm_obj_root', None)
Index: utils/lit/lit/Test.py
===================================================================
--- utils/lit/lit/Test.py
+++ utils/lit/lit/Test.py
@@ -235,6 +235,15 @@
 
         return False
 
+    def isEarlyTest(self):
+        """
+        isEarlyTest() -> bool
+
+        Check whether this test should be executed early in a particular run.
+        This can be used for test suites with long running tests to maximize
+        parallelism or where it is desirable to surface their failures early.
+        """
+        return self.suite.config.is_early
 
     def getJUnitXML(self):
         test_name = self.path_in_suite[-1]
Index: utils/lit/lit/TestingConfig.py
===================================================================
--- utils/lit/lit/TestingConfig.py
+++ utils/lit/lit/TestingConfig.py
@@ -118,7 +118,8 @@
     def __init__(self, parent, name, suffixes, test_format,
                  environment, substitutions, unsupported,
                  test_exec_root, test_source_root, excludes,
-                 available_features, pipefail, limit_to_features = []):
+                 available_features, pipefail, limit_to_features = [],
+                 is_early = False):
         self.parent = parent
         self.name = str(name)
         self.suffixes = set(suffixes)
@@ -135,6 +136,8 @@
         # require one of the features in this list if this list is non-empty.
         # Configurations can set this list to restrict the set of tests to run.
         self.limit_to_features = set(limit_to_features)
+        # Whether the suite should be tested early in a given run.
+        self.is_early = bool(is_early)
 
     def finish(self, litConfig):
         """finish() - Finish this config object, after loading is complete."""
Index: utils/lit/lit/main.py
===================================================================
--- utils/lit/lit/main.py
+++ utils/lit/lit/main.py
@@ -367,7 +367,8 @@
     elif opts.incremental:
         sort_by_incremental_cache(run)
     else:
-        run.tests.sort(key = lambda result_test: result_test.getFullName())
+        run.tests.sort(key = lambda t: (('a' if t.isEarlyTest() else 'b') +
+                                        t.getFullName()))
 
     # Finally limit the number of tests, if desired.
     if opts.maxTests is not None: