Revert a recent change. Otherwise some tests break in FAST_COMPILE and we end up…

theano/tensor/subtensor.py

@@ -576,8 +576,11 @@ class Subtensor(Op):
         if x.dtype.find('int') != -1:
             first = x.zeros_like().astype(theano.config.floatX)
         else:
-            first = IncSubtensor(self.idx_list,
-                                 set_instead_of_inc=True)(x.zeros_like(),
+            # For best optimization, we let this as an inc.
+            # This allow the opt local_IncSubtensor_serialize to apply first.
+            # We need to implement an optimization that will convert this to a
+            # set subtensor.
+            first = IncSubtensor(self.idx_list)(x.zeros_like(),
                                                 gz, *rest)
         return ([first] + [DisconnectedType()()] * len(rest))