[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

1 files changed, 4 insertions, 0 deletions

diff --git a/clang/test/utils/update_cc_test_checks/lit.local.cfg b/clang/test/utils/update_cc_test_checks/lit.local.cfg
index b78c4ff..b461878 100644
--- a/clang/test/utils/update_cc_test_checks/lit.local.cfg
+++ b/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)