diff --git a/clang/test/3C/3c-regtest.py b/clang/test/3C/3c-regtest.py
new file mode 100755
index 000000000000..d615ba765a36
--- /dev/null
+++ b/clang/test/3C/3c-regtest.py
@@ -0,0 +1,101 @@
+#!/usr/bin/env python
+#
+# Usage: 3c-regtest -t TMPNAME [options...] SRC_FILE
+#
+# TMPNAME corresponds to %t and SRC_FILE corresponds to %s. Both are required.
+#
+# --subst can be used for things such as %clang, for example (assuming single
+# --quotes are removed by the shell):
+#
+# --subst %clang 'clang -some-flag'
+#
+# (Note: A literal % has to be represented as %% in a RUN line. If we instead
+# established the convention of automatically prepending the % here, then the
+# RUN line would trip the "Do not use 'clang' in tests, use '%clang'." error.)
+#
+# Example RUN line:
+#
+# // RUN: %S/3c-regtest.py -t %t --subst %%clang '%clang' %s
+#
+# Soon, we'll add options for different kinds of 3C regression tests.
+
+# TODO: Add Windows compatibility code once we have an easy way to test on Windows.
+
+import sys
+import os
+import platform
+import argparse
+
+sys.path.insert(0, os.path.dirname(__file__) + '/../../../llvm/utils/lit')
+import lit.TestRunner
+
+print "NOTICE: cwd is %s" % os.getcwd()
+
+def die(msg):
+    sys.stderr.write('Error: %s\n' % msg)
+    sys.exit(1)
+
+parser = argparse.ArgumentParser(description='Run a 3C regression test.')
+# TODO: Add help
+parser.add_argument('test_file')
+parser.add_argument('-t', required=True)
+parser.add_argument('--subst', action='append', nargs=2, default=[])
+args = parser.parse_args()
+
+test_dir = os.path.dirname(args.test_file)
+if test_dir == '':
+    test_dir = '.'
+
+tmpName = args.t
+tmpNameSuffix = '.tmp'
+if tmpName.endswith(tmpNameSuffix):
+    tmpBase = tmpName[:-len(tmpNameSuffix)]
+else:
+    die('-t argument %s does not end with %s' % (tmpName, tmpNameSuffix))
+
+substitutions = [
+  ('%%', '#_MARKER_#'),
+  ('%s', args.test_file),
+  ('%S', test_dir),
+  ('%t', tmpName),
+]
+substitutions.extend(args.subst)
+substitutions.append(('#_MARKER_#', '%'))
+
+# Starting with processor.py because it's always the same.
+commands = [
+    # FIXME: 'foo.c' + 'hecked.c' is a terrible hack; find the right way to do this.
+    '3c -alltypes -addcr %s -- | FileCheck -match-full-lines -check-prefixes="CHECK_ALL","CHECK" %s',
+    '3c -addcr %s -- | FileCheck -match-full-lines -check-prefixes="CHECK_NOALL","CHECK" %s',
+    '3c -addcr %s -- | %clang -c -fcheckedc-extension -x c -o /dev/null -',
+    '3c -output-postfix=checked -alltypes %s',
+    '3c -alltypes %shecked.c -- | count 0',
+    'rm %shecked.c',
+]
+commands = lit.TestRunner.applySubstitutions(commands, substitutions)
+
+class FakeTestConfig:
+    def __init__(self):
+        self.pipefail = True  # Is this always OK?
+        self.environment = dict(os.environ)
+
+class FakeTest:
+    def __init__(self):
+        self.config = FakeTestConfig()
+
+class FakeLitConfig:
+    def __init__(self):
+        self.isWindows = platform.system() == 'windows'
+        # Let the calling `lit` handle any timeout.
+        self.maxIndividualTestTime = 0
+
+res = lit.TestRunner.executeScriptInternal(
+    FakeTest(), FakeLitConfig(), tmpBase, commands, os.getcwd())
+if isinstance(res, lit.Test.Result):
+    die('Error: executeScriptInternal returned unexpected Result(%s, %r)' %
+        (res.code.name, res.output))
+
+out, err, exitCode, timeoutInfo = res
+sys.stdout.write(out)
+sys.stderr.write(err)
+sys.exit(exitCode)
diff --git a/clang/test/3C/b9_allsafestructp.c b/clang/test/3C/b9_allsafestructp.c
index 4925a2be2450..453694c343be 100644
--- a/clang/test/3C/b9_allsafestructp.c
+++ b/clang/test/3C/b9_allsafestructp.c
@@ -1,9 +1,4 @@
-// RUN: 3c -alltypes -addcr %s -- | FileCheck -match-full-lines -check-prefixes="CHECK_ALL","CHECK" %s
-// RUN: 3c -addcr %s -- | FileCheck -match-full-lines -check-prefixes="CHECK_NOALL","CHECK" %s
-// RUN: 3c -addcr %s -- | %clang -c -fcheckedc-extension -x c -o /dev/null -
-// RUN: 3c -output-postfix=checked -alltypes %s
-// RUN: 3c -alltypes %S/b9_allsafestructp.checked.c -- | count 0
-// RUN: rm %S/b9_allsafestructp.checked.c
+// RUN: %S/3c-regtest.py -t %t --subst %%clang '%clang' %s
 #include <stddef.h>
 #include <stddef.h>
 extern _Itype_for_any(T) void *calloc(size_t nmemb, size_t size) : itype(_Array_ptr<T>) byte_count(nmemb * size);