Index: mlir/lib/IR/AffineExpr.cpp
===================================================================
--- mlir/lib/IR/AffineExpr.cpp
+++ mlir/lib/IR/AffineExpr.cpp
@@ -601,7 +601,10 @@
     return getAffineConstantExpr(lhsConst.getValue() * rhsConst.getValue(),
                                  lhs.getContext());
 
-  assert(lhs.isSymbolicOrConstant() || rhs.isSymbolicOrConstant());
+  // Even though it is not legal to multiply two dimensions it may happen as an
+  // intermediate state during composition.
+  if(!lhs.isSymbolicOrConstant() && !rhs.isSymbolicOrConstant())
+    return nullptr;
 
   // Canonicalize the mul expression so that the constant/symbolic term is the
   // RHS. If both the lhs and rhs are symbolic, swap them if the lhs is a
Index: mlir/test/Dialect/Affine/canonicalize.mlir
===================================================================
--- mlir/test/Dialect/Affine/canonicalize.mlir
+++ mlir/test/Dialect/Affine/canonicalize.mlir
@@ -43,7 +43,8 @@
 // CHECK-DAG: [[$MAP_mix_dims_and_symbols_e:#map[0-9]+]] = affine_map<()[s0, s1] -> ((s1 * 4 + s0 * 168 - 4) floordiv 3)>
 
 // Affine maps for test case: $symbolic_semi_affine
-// CHECK-DAG: [[$symbolic_semi_affine:#map[0-9]+]] = affine_map<(d0)[s0] -> (d0 floordiv (s0 + 1))>
+// CHECK-DAG: [[$symbolic_semi_affine_1:#map[0-9]+]] = affine_map<(d0)[s0] -> (d0 floordiv (s0 + 1))>
+// CHECK-DAG: [[$symbolic_semi_affine_2:#map[0-9]+]] = affine_map<(d0)[s0] -> (d0 * (s0 + 1))>
 
 // CHECK-LABEL: func @compose_affine_maps_1dto2d_no_symbols() {
 func @compose_affine_maps_1dto2d_no_symbols() {
@@ -382,8 +383,11 @@
   affine.for %i0 = 1 to 100 {
     %1 = affine.apply affine_map<()[s0] -> (s0 + 1)> ()[%M]
     %2 = affine.apply affine_map<(d0)[s0] -> (d0 floordiv s0)> (%i0)[%1]
-    // CHECK-DAG: {{.*}} = affine.apply [[$symbolic_semi_affine]](%{{.*}})[%{{.*}}]
+    // CHECK-DAG: {{.*}} = affine.apply [[$symbolic_semi_affine_1]](%{{.*}})[%{{.*}}]
     store %f1, %A[%2] : memref<?xf32>
+    %3 = affine.apply affine_map<(d0)[s0] -> (d0 * s0)> (%i0)[%1]
+    // CHECK-DAG: {{.*}} = affine.apply [[$symbolic_semi_affine_2]](%{{.*}})[%{{.*}}]
+    store %f1, %A[%3] : memref<?xf32>
   }
   return
 }