nir: always set the exact_trip_count_unknown loop terminator property

Previously we only cared if this was set for the limiting
terminator. However in the following patch we will make use of this
information on other terminators to decide if we can eliminate them.

Reviewed-by: Emma Anholt <emma@anholt.net>
Reviewed-by: Jason Ekstrand <jason.ekstrand@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16399>

src/compiler/nir/nir_loop_analyze.c

@@ -1072,6 +1072,7 @@ find_trip_count(loop_info_state *state, unsigned execution_mode)
           * nir_opt_dead_cf pass.
           */
          trip_count_known = false;
+         terminator->exact_trip_count_unknown = true;
          continue;
       }
 
@@ -1105,6 +1106,7 @@ find_trip_count(loop_info_state *state, unsigned execution_mode)
        */
       if (!basic_ind.def) {
          trip_count_known = false;
+         terminator->exact_trip_count_unknown = true;
          continue;
       }
 
@@ -1120,6 +1122,7 @@ find_trip_count(loop_info_state *state, unsigned execution_mode)
          if (!try_find_limit_of_alu(limit, &limit_val, terminator, state)) {
             /* Guess loop limit based on array access */
             if (!guess_loop_limit(state, &limit_val, basic_ind)) {
+               terminator->exact_trip_count_unknown = true;
                continue;
             }
 
@@ -1174,11 +1177,13 @@ find_trip_count(loop_info_state *state, unsigned execution_mode)
       if (iterations == -1) {
          trip_count_known = false;
          guessed_trip_count = false;
+         terminator->exact_trip_count_unknown = true;
          continue;
       }
 
       if (guessed_trip_count) {
          guessed_trip_count = false;
+         terminator->exact_trip_count_unknown = true;
          if (state->loop->info->guessed_trip_count == 0 ||
              state->loop->info->guessed_trip_count > iterations)
             state->loop->info->guessed_trip_count = iterations;