compiler: Revert incorrect modifications to DAG construction

Author: EdCaunt

devito/ir/support/basic.py

@@ -363,7 +363,6 @@ def distance(self, other):
                 # Case 1: `sit` is an IterationInterval with statically known
                 # trip count. E.g. it ranges from 0 to 3; `other` performs a
                 # constant access at 4
-                # TODO: This case represents the majority of time constructing a DAG
                 for v in (self[n], other[n]):
                     try:
                         if bool(v < sit.symbolic_min or v > sit.symbolic_max):
@@ -1123,10 +1122,6 @@ def d_anti(self):
         """Anti (or "write-after-read") dependences."""
         return DependenceGroup(self.d_anti_gen())
 
-    @cached_property
-    def has_antidependencies(self):
-        return any(i.cause for i in self.d_anti_gen())
-
     @memoized_generator
     def d_output_gen(self):
         """Generate the output (or "write-after-write") dependences."""

devito/passes/clusters/misc.py

@@ -362,8 +362,9 @@ def is_cross(source, sink):
                 # (intuitively, "the loop nests are to be kept separated")
                 # * All ClusterGroups between `cg0` and `cg1` must precede `cg1`
                 # * All ClusterGroups after `cg1` cannot precede `cg1`
-                # TODO: Check that this is indeed what the attribute does
-                if prefix and scope.has_antidependencies:
+
+                # FIXME: Slow
+                if any(i.cause & prefix for i in scope.d_anti_gen()):
                     for cg2 in cgroups[n:cgroups.index(cg1)]:
                         dag.add_edge(cg2, cg1)
                     for cg2 in cgroups[cgroups.index(cg1)+1:]: