[Refactor] Simplify logic in the `CompleteBufferFragment` (#1226)

* fix

* Fix logging level in LayoutNode::InverseWithLevel method from WARNING to DLOG for symbolic layout fallback.

* lint fix

---------
Co-authored-by: Zhiwen Mo <zm125@ic.ac.uk>

src/layout/layout.cc

@@ -250,7 +250,7 @@ std::pair<Layout, arith::IterMapLevel> LayoutNode::InverseWithLevel() const {
   if (!is_static_shape) {
     // Runtime guards keep dynamic tails safe, so we allow NoCheck here and
     // warn.
-    LOG(WARNING) << "Layout::Inverse on symbolic layout, falling back to "
+    DLOG(WARNING) << "Layout::Inverse on symbolic layout, falling back to "
                      "NoCheck; symbolic dims: "
                   << symbolic_dims;
   }

src/op/parallel.cc

@@ -649,37 +649,8 @@ Fragment ParallelOpNode::CompleteBufferFragment(const Buffer &buffer) const {
       DivideUnusedIterators(indice_map_[buffer], loop_vars_, &analyzer_));
   auto bijective_indice = indice_map_[buffer];
   bijective_indice.push_back(rep_b);
-  Layout layout_before_inv = Layout(loop_vars_, bijective_indice);
-
-  // Pre-check cardinality to guard non-bijective combinations after adding
-  // rep_b.
-  PrimExpr in_prod = 1;
-  for (const auto &iv : loop_vars_)
-    in_prod *= iv->dom->extent;
-  PrimExpr out_prod = 1;
-  for (const auto &d : layout_before_inv->OutputShape())
-    out_prod *= d;
-
-  if (!analyzer_.CanProveEqual(in_prod, out_prod)) {
-    DLOG(WARNING) << "  Non-bijective mapping after appending rep_b; falling "
-                     "back to no-rep inversion.";
-    Layout ind_inv_fallback =
-        Layout(loop_vars_, indice_map_[buffer])->Inverse();
-    PrimExpr indice_rep_extent = 1;
-    PrimExpr loop_rep_extent = loop_layout_->ReplicateExtent();
-    PrimExpr dest_buffer_rep_extent = indice_rep_extent * loop_rep_extent;
-    Array<PrimExpr> fwd2;
-    for (size_t i = 0; i < buffer->shape.size(); i++) {
-      fwd2.push_back(InputPlaceholder(i));
-    }
-    PrimExpr thd_b = loop_layout_->ForwardThread(
-        ind_inv_fallback->Forward(fwd2), std::nullopt);
-    return Fragment(buffer->shape, {}, thd_b, dest_buffer_rep_extent,
-                    std::nullopt)
-        ->CondenseReplicateVar();
-  }
+  Layout ind_inv = Layout(loop_vars_, bijective_indice)->Inverse();
 
-  Layout ind_inv = layout_before_inv->Inverse();
   PrimExpr indice_rep_extent =
       ind_inv->InputShape().back(); // this is the size of rep_b
   PrimExpr loop_rep_extent = loop_layout_->ReplicateExtent();