diff --git a/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/on_the_fly_arg_change.ll.initially_disabled.expected b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/on_the_fly_arg_change.ll.initially_disabled.expected
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/on_the_fly_arg_change.ll.initially_disabled.expected
@@ -0,0 +1,42 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature --scrub-attributes --disable
+; RUN: opt -S < %s | FileCheck %s
+
+declare void @foo()
+
+define void @check_lines_1() {
+  ret void
+}
+
+; UTC_ARGS: --disable
+
+; A check line that would not be auto generated.
+; CHECK: define void @no_check_lines() {
+define void @no_check_lines() {
+  ret void
+}
+
+; UTC_ARGS: --enable
+
+define void @check_lines_2() {
+; CHECK-LABEL: define {{[^@]+}}@check_lines_2()
+; CHECK-NEXT:    ret void
+;
+  ret void
+}
+
+define void @scrub() {
+; CHECK-LABEL: define {{[^@]+}}@scrub()
+; CHECK-NEXT:    call void @foo()
+; CHECK-NEXT:    ret void
+;
+  call void @foo() readnone
+  ret void
+}
+
+define i32 @signature(i32 %arg) {
+; CHECK-LABEL: define {{[^@]+}}@signature
+; CHECK-SAME: (i32 [[ARG:%.*]])
+; CHECK-NEXT:    ret i32 [[ARG]]
+;
+  ret i32 %arg
+}
diff --git a/llvm/test/tools/UpdateTestChecks/update_test_checks/on_the_fly_arg_change.test b/llvm/test/tools/UpdateTestChecks/update_test_checks/on_the_fly_arg_change.test
--- a/llvm/test/tools/UpdateTestChecks/update_test_checks/on_the_fly_arg_change.test
+++ b/llvm/test/tools/UpdateTestChecks/update_test_checks/on_the_fly_arg_change.test
@@ -4,3 +4,13 @@
 ## Check that running the script again does not change the result:
 # RUN: %update_test_checks %t.ll
 # RUN: diff -u %t.ll %S/Inputs/on_the_fly_arg_change.ll.expected
+## Check that the --disable flag is added to the initial UTC_ARGS:
+# RUN: cp -f %S/Inputs/on_the_fly_arg_change.ll %t.ll
+# RUN: %update_test_checks --function-signature --scrub-attributes --disable %t.ll
+# RUN: diff -u %t.ll %S/Inputs/on_the_fly_arg_change.ll.initially_disabled.expected
+## Check that the --disable flag from UTC_ARGS is used:
+# RUN: %update_test_checks %t.ll
+# RUN: diff -u %t.ll %S/Inputs/on_the_fly_arg_change.ll.initially_disabled.expected
+## Check that UTC_ARGS: is parsed after the real command line arguments:
+# RUN: %update_test_checks --enable %t.ll
+# RUN: diff -u %t.ll %S/Inputs/on_the_fly_arg_change.ll.initially_disabled.expected
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
@@ -396,19 +396,30 @@
         if prefixes.count(prefix) > 1:
           warn("Supplied prefix '%s' is not unique in the prefix list." % (prefix,))
 
+
 def get_autogennote_suffix(parser, args):
-    autogenerated_note_args = ''
-    for k, v in args._get_kwargs():
-        if parser.get_default(k) == v or k == 'tests' or k == 'update_only' or k == 'opt_binary':
-            continue
-        k = k.replace('_', '-')
-        if type(v) is bool:
-            autogenerated_note_args += '--%s ' % (k)
-        else:
-            autogenerated_note_args += '--%s %s ' % (k, v)
-    if autogenerated_note_args:
-        autogenerated_note_args = ' %s %s' % (UTC_ARGS_KEY, autogenerated_note_args[:-1])
-    return autogenerated_note_args
+  autogenerated_note_args = ''
+  for action in parser._actions:
+    if not hasattr(args, action.dest):
+      continue  # Ignore options such as --help that aren't included in args
+    # Ignore parameters such as paths to the binary or the list of tests
+    if action.dest in ('tests', 'update_only', 'opt_binary', 'llc_binary',
+                       'clang', 'opt', 'llvm_bin', 'verbose'):
+      continue
+    value = getattr(args, action.dest)
+    if action.const is not None:  # action stores a constant (usually True/False)
+      # Skip actions with different constant values (this happens with boolean
+      # --foo/--no-foo options)
+      if value != action.const:
+        continue
+    if parser.get_default(action.dest) == value:
+      continue  # Don't add default values
+    autogenerated_note_args += action.option_strings[0] + ' '
+    if action.const is None:  # action takes a parameter
+      autogenerated_note_args += '%s ' % value
+  if autogenerated_note_args:
+    autogenerated_note_args = ' %s %s' % (UTC_ARGS_KEY, autogenerated_note_args[:-1])
+  return autogenerated_note_args
 
 
 def check_for_command(line, parser, args, argv):