(mutually_exclusive_p): Fix the regression from commit 6fad73d7cc53

Commit 6fad73d7cc53 throws away some useful optimization because
it misfired in some cases (as seen in bug#657260).  Here we try to
recover those useful optimizations with a slightly more careful
algorithm.

* src/regex-emacs.c (mutually_exclusive_aux): Rename from
`mutually_exclusive_p`.  Add two new args.  Improve the
case where we need to recurse.
(mutually_exclusive_p): New function defined on top of it.

* test/src/regex-emacs-tests.el (regexp-tests-backtrack-optimization):
Re-enable the test.

1 files changed, 0 insertions, 1 deletions

diff --git a/test/src/regex-emacs-tests.el b/test/src/regex-emacs-tests.el
index ed0dc4c5a9d..f2bee713864 100644
--- a/test/src/regex-emacs-tests.el
+++ b/test/src/regex-emacs-tests.el
@@ -873,7 +873,6 @@ This evaluates the TESTS test cases from glibc."
   (should (equal (string-match "\\`a\\{2\\}*\\'" "a") nil)))
 
 (ert-deftest regexp-tests-backtrack-optimization () ;bug#61514
-  :expected-result :failed
   ;; Make sure we don't use up the regexp stack needlessly.
   (with-current-buffer (get-buffer-create "*bug*")
     (erase-buffer)