diff --git a/llvm/docs/CommandGuide/lit.rst b/llvm/docs/CommandGuide/lit.rst
--- a/llvm/docs/CommandGuide/lit.rst
+++ b/llvm/docs/CommandGuide/lit.rst
@@ -224,6 +224,11 @@
 
  List all of the discovered tests and exit.
 
+.. option:: --repeat=N
+
+ Run each test ``N`` times.  Currently this is primarily useful for catching
+ failures in flaky tests.
+
 EXIT STATUS
 -----------
 
diff --git a/llvm/utils/lit/lit/Test.py b/llvm/utils/lit/lit/Test.py
--- a/llvm/utils/lit/lit/Test.py
+++ b/llvm/utils/lit/lit/Test.py
@@ -244,6 +244,15 @@
         # The test result, once complete.
         self.result = None
 
+        # The repeat index of this test, or None.
+        self.index = None
+
+    def copyWithIndex(self, index):
+        import copy
+        res = copy.copy(self)
+        res.index = index
+        return res
+
     def setResult(self, result):
         assert self.result is None, "result already set"
         assert isinstance(result, Result), "unexpected result type"
diff --git a/llvm/utils/lit/lit/TestRunner.py b/llvm/utils/lit/lit/TestRunner.py
--- a/llvm/utils/lit/lit/TestRunner.py
+++ b/llvm/utils/lit/lit/TestRunner.py
@@ -1061,6 +1061,8 @@
     execdir,execbase = os.path.split(execpath)
     tmpDir = os.path.join(execdir, 'Output')
     tmpBase = os.path.join(tmpDir, execbase)
+    if test.index is not None:
+        tmpBase += '_%d' % test.index
     return tmpDir, tmpBase
 
 def colonNormalizePath(path):
diff --git a/llvm/utils/lit/lit/cl_arguments.py b/llvm/utils/lit/lit/cl_arguments.py
--- a/llvm/utils/lit/lit/cl_arguments.py
+++ b/llvm/utils/lit/lit/cl_arguments.py
@@ -163,6 +163,11 @@
     debug_group.add_argument("--show-tests",
             help="Show all discovered tests and exit",
             action="store_true")
+    debug_group.add_argument("--repeat",
+            dest="repeatTests",
+            metavar="N",
+            help="Repeat tests N times",
+            type=_positive_int)
     debug_group.add_argument("--show-used-features",
             help="Show all features used in the test suite (in XFAIL, UNSUPPORTED and REQUIRES) and exit",
             action="store_true")
diff --git a/llvm/utils/lit/lit/main.py b/llvm/utils/lit/lit/main.py
--- a/llvm/utils/lit/lit/main.py
+++ b/llvm/utils/lit/lit/main.py
@@ -66,6 +66,11 @@
 
     determine_order(discovered_tests, opts.order)
 
+    if opts.repeatTests:
+        discovered_tests = [t.copyWithIndex(i)
+                            for t in discovered_tests
+                            for i in range(opts.repeatTests)]
+
     selected_tests = [t for t in discovered_tests if
                       opts.filter.search(t.getFullName())]
     if not selected_tests: