diff --git a/llvm/utils/UpdateTestChecks/common.py b/llvm/utils/UpdateTestChecks/common.py
--- a/llvm/utils/UpdateTestChecks/common.py
+++ b/llvm/utils/UpdateTestChecks/common.py
@@ -71,7 +71,8 @@
 SCRUB_KILL_COMMENT_RE = re.compile(r'^ *#+ +kill:.*\n')
 SCRUB_LOOP_COMMENT_RE = re.compile(
     r'# =>This Inner Loop Header:.*|# in Loop:.*', flags=re.M)
-
+SCRUB_FILECHECK_REGEX_RE = re.compile(r'{{')
+SCRUB_FILECHECK_REGEX_REPLACEMENT = r'{{[{][{]}}'
 
 def error(msg, test_file=None):
   if test_file:
@@ -91,6 +92,8 @@
   body = string.expandtabs(body, 2)
   # Strip trailing whitespace.
   body = SCRUB_TRAILING_WHITESPACE_RE.sub(r'', body)
+  # Munge anything that could be interpreted as a FileCheck regexp.
+  body = SCRUB_FILECHECK_REGEX_RE.sub(SCRUB_FILECHECK_REGEX_REPLACEMENT, body)
   return body
 
 def do_scrub(body, scrubber, scrubber_args, extra):