docs: to-do comment

nx/lib/nx/defn/sharding_compiler/passes/graph_splitter.ex

@@ -57,6 +57,7 @@ defmodule Nx.Defn.ShardingCompiler.Passes.GraphSplitter do
 
           argument_sources = Map.take(state.args, Map.keys(arg_remapping))
 
+          # TO-DO: collect shards for expr and arguments here and annotate them in the chain below
           [{id, category, expr, argument_sources} | acc]
         end
       )
@@ -129,6 +130,9 @@ defmodule Nx.Defn.ShardingCompiler.Passes.GraphSplitter do
     not (left_valid and right_valid)
   end
 
+  # default to true so that we can optimize this gradually
+  defp must_split_expr?(_, _, _), do: true
+
   defp split_expr(expr, args, category, {cache, state}) do
     # We need to save this so that each previous stage
     # isn't affected by following ones