[!281] Avoid more no op conditionals

Merge branch 'feature/more-avoiding-of-noop-conditionals' into 'master'

ref:dominic/dune-perftool By looking at the possible values of the condition.

See merge request [dominic/dune-perftool!281]

  [dominic/dune-perftool!281]: gitlab.dune-project.org/dominic/dune-perftool/merge_requests/281

python/dune/perftool/pdelab/localoperator.py

@@ -301,6 +301,17 @@ def boundary_predicates(measure, subdomain_id):
             visitor = get_visitor(measure, subdomain_id)
             subdomain_data = visitor(subdomain_data, do_predicates=True)
 
+        # Often, boundary predicates are just nested conditionals. We try to find
+        # out which of these are unfulfillable in the first place.
+        def possible_values(expr):
+            if isinstance(expr, prim.If):
+                return set(possible_values(expr.then)).union(possible_values(expr.else_))
+            else:
+                return set({expr})
+
+        if subdomain_id not in possible_values(subdomain_data):
+            return frozenset({False})
+
         p = prim.Comparison(subdomain_data, '==', subdomain_id)
 
         # Try to find conditions that are always 0 or always 1
@@ -308,7 +319,7 @@ def boundary_predicates(measure, subdomain_id):
         try:
             eval = evaluate(p)
             if not eval:
-                predicates.append(False)
+                return frozenset({False})
         except:
             predicates.append(p)