Delay the computation of frozen evars in legacy unification.

This source of slowness has been observed in VST, but it is probably
pervasive. Most of the unification problems are not mentioning evars,
it is thus useless to compute the set of frozen evars upfront.

We also seize the opportunity to reverse the flag, because it is always
used negatively.

1 files changed, 1 insertions, 1 deletions

diff --git a/tactics/auto.ml b/tactics/auto.ml
index 499e7a63d7..67f49f0074 100644
--- a/tactics/auto.ml
+++ b/tactics/auto.ml
@@ -49,7 +49,7 @@ let auto_core_unif_flags_of st1 st2 = {
   check_applied_meta_types = false;
   use_pattern_unification = false;
   use_meta_bound_pattern_unification = true;
-  frozen_evars = Evar.Set.empty;
+  allowed_evars = AllowAll;
   restrict_conv_on_strict_subterms = false; (* Compat *)
   modulo_betaiota = false;
   modulo_eta = true;