Merge pull request #2392 from devitocodes/fix-cond-placement

compiler: Patch CSE in presence of conditionals

devito/passes/clusters/cse.py

@@ -98,24 +98,26 @@ def _cse(maybe_exprs, make, min_cost=1, mode='default'):
 
  # Create temporaries
  hit = max(targets.values())
- temps = [Eq(make(), k) for k, v in targets.items() if v == hit]
+ chosen = [(k, make()) for k, v in targets.items() if v == hit]
 
  # Apply replacements
  # The extracted temporaries are inserted before the first expression
  # that contains it
+ scheduled = []
  updated = []
  for e in processed:
  pe = e
- for t in temps:
- pe, changed = _uxreplace(pe, {t.rhs: t.lhs})
- if changed and t not in updated:
- updated.append(t)
+ for k, v in chosen:
+ pe, changed = _uxreplace(pe, {k: v})
+ if changed and v not in scheduled:
+ updated.append(pe.func(v, k, operation=None))
+ scheduled.append(v)
  updated.append(pe)
  processed = updated
 
  # Update `exclude` for the same reasons as above -- to rule out CSE across
  # Dimension-independent data dependences
- exclude.update({t.lhs for t in temps})
+ exclude.update(scheduled)
 
  # At this point we may have useless temporaries (e.g., r0=r1). Let's drop them
  processed = _compact_temporaries(processed, exclude)

tests/test_dse.py

@@ -13,7 +13,7 @@
  ConditionalDimension, DefaultDimension, Grid, Operator,
  norm, grad, div, dimensions, switchconfig, configuration,
  centered, first_derivative, solve, transpose, Abs, cos,
- sin, sqrt)
+ sin, sqrt, Ge)
 from devito.exceptions import InvalidArgument, InvalidOperator
 from devito.finite_differences.differentiable import diffify
 from devito.ir import (Conditional, DummyEq, Expression, Iteration, FindNodes,
@@ -168,6 +168,29 @@ def test_cse_temp_order():
  assert type(args[2]) is CTemp
 
 
+def test_cse_w_conditionals():
+ grid = Grid(shape=(10, 10, 10))
+ x, _, _ = grid.dimensions
+
+ cd = ConditionalDimension(name='cd', parent=x, condition=Ge(x, 4),
+ indirect=True)
+
+ f = Function(name='f', grid=grid)
+ g = Function(name='g', grid=grid)
+ h = Function(name='h', grid=grid)
+ a0 = Function(name='a0', grid=grid)
+ a1 = Function(name='a1', grid=grid)
+
+ eqns = [Eq(h, a0, implicit_dims=cd),
+ Eq(a0, a0 + f*g, implicit_dims=cd),
+ Eq(a1, a1 + f*g, implicit_dims=cd)]
+
+ op = Operator(eqns)
+
+ assert_structure(op, ['x,y,z'], 'xyz')
+ assert len(FindNodes(Conditional).visit(op)) == 1
+
+
 @pytest.mark.parametrize('expr,expected', [
  ('2*fa[x] + fb[x]', '2*fa[x] + fb[x]'),
  ('fa[x]**2', 'fa[x]*fa[x]'),