feat: support binary backend in compiled mode

lib/emlx.ex

@@ -318,25 +318,32 @@ defmodule EMLX do
 
   @impl Nx.Defn.Compiler
   def __jit__(key, vars, fun, args_list, opts) do
-    # TODO: instead of checking the backend here,
-    # we should automatically convert from binary backend to EMLX backend
-    # given a device optionsg
-    case Nx.default_backend() do
-      EMLX.Backend ->
-        :ok
-
-      {EMLX.Backend, _} ->
-        :ok
-
-      other ->
-        raise ArgumentError, "EMLX can only be used with the EMLX backend, got: #{inspect(other)}"
-    end
-
     __compile__(key, vars, fun, opts).(args_list)
   end
 
   @impl Nx.Defn.Compiler
   def __compile__(key, vars, fun, opts) do
+    backend = Nx.default_backend()
+
+    target_backend =
+      case backend do
+        EMLX.Backend ->
+          backend
+
+        {EMLX.Backend, _} ->
+          backend
+
+        Nx.BinaryBackend ->
+          EMLX.Backend
+
+        {Nx.BinaryBackend, _} ->
+          EMLX.Backend
+
+        other ->
+          raise ArgumentError,
+                "EMLX can only be used with the EMLX.Backend or Nx.BinaryBackend, got: #{inspect(other)}"
+      end
+
     expr = fun.(vars)
 
     fn [args] ->
@@ -346,6 +353,12 @@ defmodule EMLX do
             %Nx.Tensor{data: %EMLX.Backend{ref: {device, ref}}} ->
               {device, ref}
 
+            %Nx.Tensor{data: %Nx.BinaryBackend{}} = t ->
+              %Nx.Tensor{data: %EMLX.Backend{ref: {device, ref}}} =
+                Nx.backend_copy(t, target_backend)
+
+              {device, ref}
+
             other ->
               %Nx.Tensor{data: %EMLX.Backend{ref: {device, ref}}} = Nx.to_tensor(other)
               {device, ref}

test/emlx_test.exs

@@ -9,4 +9,30 @@ defmodule EMLXTest do
     assert_equal(left, Nx.tensor(3))
     assert_equal(right, Nx.tensor(-1))
   end
+
+  test "__jit__ supports binary backend in arguments" do
+    {left, right} =
+      Nx.Defn.jit_apply(
+        &{Nx.add(&1, &2), Nx.subtract(&1, &2)},
+        [Nx.tensor(1, backend: Nx.BinaryBackend), 2],
+        compiler: EMLX
+      )
+
+    assert_equal(left, Nx.tensor(3))
+    assert_equal(right, Nx.tensor(-1))
+  end
+
+  test "__jit__ supports binary backend as the default backend" do
+    Nx.with_default_backend(Nx.BinaryBackend, fn ->
+      {left, right} =
+        Nx.Defn.jit_apply(
+          &{Nx.add(&1, &2), Nx.subtract(&1, &2)},
+          [Nx.tensor(1), 2],
+          compiler: EMLX
+        )
+
+      assert_equal(left, Nx.tensor(3))
+      assert_equal(right, Nx.tensor(-1))
+    end)
+  end
 end