compiler: Fix space conditions with loop blocking

devito/passes/clusters/blocking.py

@@ -344,14 +344,16 @@ def callback(self, clusters, prefix, blk_size_gen=None):
                 ispace = decompose(c.ispace, d, block_dims)
 
                 # Use the innermost BlockDimension in place of `d`
-                exprs = [uxreplace(e, {d: bd}) for e in c.exprs]
+                subs = {d: bd}
+                exprs = [uxreplace(e, subs) for e in c.exprs]
+                guards = {subs.get(i, i): v for i, v in c.guards.items()}
 
                 # The new Cluster properties -- TILABLE is dropped after blocking
                 properties = c.properties.drop(d)
                 properties = properties.add(block_dims, c.properties[d] - TILABLES)
 
                 processed.append(c.rebuild(exprs=exprs, ispace=ispace,
-                                           properties=properties))
+                                           guards=guards, properties=properties))
             else:
                 processed.append(c)
 

tests/test_dimension.py

@@ -891,6 +891,38 @@ def test_spacial_subsampling(self, opt):
         # Verify that u2[x,y]= u[2*x, 2*y]
         assert np.allclose(u.data[:-1, 0::2, 0::2], u2.data[:-1, :, :])
 
+    def test_spacial_filtering(self):
+        grid = Grid(shape=(4, 4))
+        x, y = grid.dimensions
+
+        f = Function(name='f', grid=grid)
+        g = Function(name='g', grid=grid)
+
+        g.data[:] = [[-.7, -.8, 0, .4],
+                     [-.3, -.5, 0, .6],
+                     [.1, .2, -.1, .8],
+                     [.5, .7, 0, .9]]
+
+        condition = And(Ge(g, -0.5), Le(g, 0.5))
+        cd = ConditionalDimension(name='cd1', parent=y, condition=condition)
+
+        eqn = Eq(f, g, implicit_dims=cd)
+
+        # NOTE: bypass heuristics and enforce loop blocking. Now `cd` is defined
+        # along `y` but loop blocking will generate two different BlockDimensions,
+        # `y0_blk0` and `Y`, in place of `y`. So the compiler must be smart
+        # enough to stick `cd` inside `Y`
+        opt = ('advanced', {'blockrelax': 'device-aware'})
+
+        op = Operator(eqn, opt=opt)
+
+        op()
+
+        assert np.all(f.data == np.array([[0, 0, 0, .4],
+                                          [-.3, -.5, 0, 0],
+                                          [.1, .2, -.1, 0],
+                                          [.5, 0, 0, 0]], dtype=f.dtype))
+
     def test_time_subsampling_fd(self):
         nt = 19
         grid = Grid(shape=(11, 11))