Remove harmful antipattern

python/dune/perftool/loopy/transformations/collect_precompute.py

@@ -19,7 +19,7 @@ from loopy.kernel.creation import parse_domains
 from loopy.symbolic import pw_aff_to_expr
 from loopy.match import Tagged
 
-from loopy.symbolic import DependencyMapper
+from loopy.symbolic import DependencyMapper, IdentityMapper
 from pytools import product
 
 import pymbolic.primitives as prim
@@ -65,6 +65,23 @@ class VectorIndices(object):
         return prim.Variable(name)
 
 
+class AntiPatternRemover(IdentityMapper):
+    def map_floor_div(self, expr):
+        """ (y + (x % n)) // n -> y // n """
+        num = expr.numerator
+        den = expr.denominator
+
+        if isinstance(num, prim.Remainder) and num.denominator == den:
+            return 0
+
+        if isinstance(num, prim.Sum) and len(num.children) == 2:
+            c0, c1 = num.children
+            if isinstance(c1, prim.Remainder) and c1.denominator == den:
+                return c0 // den
+
+        return IdentityMapper.map_floor_div(self, expr)
+
+
 def collect_vector_data_precompute(knl):
     #
     # Process/Assert/Standardize the input
@@ -189,7 +206,7 @@ def collect_vector_data_precompute(knl):
                 # Add substitution rules
                 for expr in quantity_exprs:
                     assert isinstance(expr, prim.Subscript)
-                    last_index = expr.index[-1] // vertical
+                    last_index = AntiPatternRemover()(expr.index[-1] // vertical)
                     replacemap[expr] = prim.Subscript(prim.Variable(get_vector_view_name(quantity)),
                                                       (vector_indices.get(horizontal) + last_index, prim.Variable(vec_iname)),
                                                       )
@@ -230,7 +247,7 @@ def collect_vector_data_precompute(knl):
             tag = get_pymbolic_tag(insn.assignee)
             horizontal, vertical = tuple(int(i) for i in re.match("vecsumfac_h(.*)_v(.*)", tag).groups())
             if horizontal > 1:
-                last_index = insn.assignee.index[-1] // vertical
+                last_index = AntiPatternRemover()(insn.assignee.index[-1] // vertical)
             else:
                 last_index = 0
         else: