[UTC] Add --version argument

We have a number of pending changes to update_test_checks.py
(and friends) that are essentially blocked on test churn:
If the output of UTC for an existing flag combination changes,
then the next time a test is regenerated, it will contain many
spurious changes. This makes changes to UTC default
behavior essentially impossible.

Examples of such changes are:

* D133943/D142373 want --function-signature to also check the
  return type/attributes.
* D139006/D140212 want to make --function-signature the default
  behavior.
* D142452 wants to add wildcards for block labels.

This patch tries to resolve this issue by adding a --version
argument, which works as follows:

* When regenerating an old test, the default version is 1.
* When generating a new test, the default version is the newest.
 When an explicit version is specified, that of course wins.

This means that any currently existing tests will keep using
--version 1 format, while any new tests will automatically embed
--version N where N is the latest version, and then keep using
that test format from then on.

This patch only implements the --version flag without bumping
the default version, so it does not have any visible behavior
change by itself.

Differential Revision: https://reviews.llvm.org/D142473

clang/test/utils/update_cc_test_checks/lit.local.cfg

@@ -26,6 +26,10 @@ else:
     extra_args = '--clang ' + shell_quote(clang_path)
     opt_path = os.path.join(config.llvm_tools_dir, 'opt')
     extra_args += ' --opt ' + shell_quote(opt_path)
+    # Specify an explicit default version in UTC tests, so that the --version
+    # embedded in UTC_ARGS does not change in all test expectations every time
+    # the default is bumped.
+    extra_args += ' --version=1'
     script_path = os.path.join(config.llvm_src_root, 'utils',
                                'update_cc_test_checks.py')
     assert os.path.isfile(script_path)

llvm/test/tools/UpdateTestChecks/lit.local.cfg

@@ -15,6 +15,10 @@ def add_update_script_substition(name, python_exe=config.python_executable,
     assert name.startswith('%')
     script_path = os.path.join(config.llvm_src_root, 'utils', name[1:] + '.py')
     assert os.path.isfile(script_path)
+    # Specify an explicit default version in UTC tests, so that the --version
+    # embedded in UTC_ARGS does not change in all test expectations every time
+    # the default is bumped.
+    extra_args += ' --version=1'
     config.substitutions.append(
         (name, "'%s' %s %s" % (python_exe, script_path, extra_args)))
 

llvm/utils/UpdateTestChecks/common.py

@@ -18,6 +18,13 @@ from typing import List
 _verbose = False
 _prefix_filecheck_ir_name = ''
 
+"""
+Version changelog:
+
+1: Initial version, used by tests that don't specify --version explicitly.
+"""
+DEFAULT_VERSION = 1
+
 class Regex(object):
   """Wrap a compiled regular expression object to allow deep copy of a regexp.
   This is required for the deep copy done in do_scrub.
@@ -138,6 +145,10 @@ def parse_commandline_args(parser):
                       dest='gen_unused_prefix_body',
                       default=True,
                       help='Generate a function body that always matches for unused prefixes. This is useful when unused prefixes are desired, and it avoids needing to annotate each FileCheck as allowing them.')
+  # This is the default when regenerating existing tests. The default when
+  # generating new tests is determined by DEFAULT_VERSION.
+  parser.add_argument('--version', type=int, default=1,
+                      help='The version of output format')
   args = parser.parse_args()
   global _verbose, _global_value_regex, _global_hex_value_regex
   _verbose = args.verbose
@@ -226,12 +237,18 @@ def itertests(test_patterns, parser, script_name, comment_prefix=None, argparse_
     for test in tests_list:
       with open(test) as f:
         input_lines = [l.rstrip() for l in f]
-      args = parser.parse_args()
+      first_line = input_lines[0] if input_lines else ""
+      is_regenerate = UTC_ADVERT in first_line
+
+      # If we're generating a new test, set the default version to the latest.
+      argv = sys.argv[:]
+      if not is_regenerate:
+        argv.insert(1, '--version=' + str(DEFAULT_VERSION))
+
+      args = parser.parse_args(argv[1:])
       if argparse_callback is not None:
         argparse_callback(args)
-      argv = sys.argv[:]
-      first_line = input_lines[0] if input_lines else ""
-      if UTC_ADVERT in first_line:
+      if is_regenerate:
         if script_name not in first_line and not args.force_update:
           warn("Skipping test which wasn't autogenerated by " + script_name, test)
           continue