Optimize reduce for maps

Signed-off-by: José Valim <[email protected]>

Author: José Valim

lib/elixir/lib/enum.ex

@@ -1261,6 +1261,15 @@ defmodule Enum do
     :lists.foldl(fun, acc, collection)
   end
 
+  def reduce(%{__struct__: _} = collection, acc, fun) do
+    Enumerable.reduce(collection, {:cont, acc},
+                      fn x, acc -> {:cont, fun.(x, acc)} end) |> elem(1)
+  end
+
+  def reduce(%{} = collection, acc, fun) do
+    :maps.fold(fn k, v, acc -> fun.({k, v}, acc) end, acc, collection)
+  end
+
   def reduce(collection, acc, fun) do
     Enumerable.reduce(collection, {:cont, acc},
                       fn x, acc -> {:cont, fun.(x, acc)} end) |> elem(1)

lib/elixir/src/elixir_for.erl

@@ -126,29 +126,6 @@ collect_filters([H|T], Acc) ->
 collect_filters([], Acc) ->
   {Acc, []}.
 
-%% If all we have is one enum generator, we check if it is a list
-%% for optimization otherwise fallback to the reduce generator.
-build_inline(Line, [{enum, Meta, Left, Right, Filters}] = Orig, Expr, Into, Var, Acc, S) ->
-  case Right of
-    {cons, _, _, _} ->
-      build_comprehension(Line, Orig, Expr, Into);
-    {Other, _, _} when Other == tuple; Other == map ->
-      build_reduce(Orig, Expr, Into, Acc, S);
-    _ ->
-      Clauses = [{enum, Meta, Left, Var, Filters}],
-
-      {'case', -1, Right, [
-        {clause, -1,
-          [Var],
-          [[elixir_utils:erl_call(Line, erlang, is_list, [Var])]],
-          [build_comprehension(Line, Clauses, Expr, Into)]},
-        {clause, -1,
-          [Var],
-          [],
-          [build_reduce(Clauses, Expr, Into, Acc, S)]}
-      ]}
-  end;
-
 build_inline(Line, Clauses, Expr, Into, _Var, Acc, S) ->
   case lists:all(fun(Clause) -> element(1, Clause) == bin end, Clauses) of
     true  -> build_comprehension(Line, Clauses, Expr, Into);
@@ -165,7 +142,7 @@ build_into(Line, Clauses, Expr, Into, Fun, Acc, S) ->
   MatchExpr = {match, Line,
     {tuple, Line, [Acc, Fun]},
     elixir_utils:erl_call(Line, 'Elixir.Collectable', into, [Into])
- },
+  },
 
   TryExpr =
     {'try', Line,
@@ -199,10 +176,8 @@ build_reduce(Clauses, Expr, {bin, _, _} = Into, Acc, S) ->
 
 build_reduce_clause([{enum, Meta, Left, Right, Filters}|T], Expr, Arg, Acc, S) ->
   Line  = ?line(Meta),
-  Inner = build_reduce_clause(T, Expr, Acc, Acc, S),
-
-  True  = pair(Line, cont, Inner),
-  False = pair(Line, cont, Acc),
+  True  = build_reduce_clause(T, Expr, Acc, Acc, S),
+  False = Acc,
 
   Clauses0 =
     case is_var(Left) of
@@ -218,11 +193,8 @@ build_reduce_clause([{enum, Meta, Left, Right, Filters}|T], Expr, Arg, Acc, S) -
       [Left, Acc], [],
       [join_filters(Line, Filters, True, False)]}|Clauses0],
 
-  Args  = [Right, pair(Line, cont, Arg), {'fun', Line, {clauses, Clauses1}}],
-  Tuple = elixir_utils:erl_call(Line, 'Elixir.Enumerable', reduce, Args),
-
-  %% Use -1 because in case of no returns we don't care about the result
-  elixir_utils:erl_call(-1, erlang, element, [{integer, Line, 2}, Tuple]);
+  Args  = [Right, Arg, {'fun', Line, {clauses, Clauses1}}],
+  elixir_utils:erl_call(Line, 'Elixir.Enum', reduce, Args);
 
 build_reduce_clause([{bin, Meta, Left, Right, Filters}|T], Expr, Arg, Acc, S) ->
   Line = ?line(Meta),