Misc grappler improvements:

 * Avoid copying optimized graphs since that takes time.
 * Avoid optimizing a pruned graph, since it's already been pruned there isn't much to gain

PiperOrigin-RevId: 163842122

tensorflow/core/common_runtime/simple_graph_execution_state.cc

@@ -290,6 +290,10 @@ Status SimpleGraphExecutionState::InitBaseGraph(
 Status SimpleGraphExecutionState::OptimizeGraph(
     const BuildGraphOptions& options, std::unique_ptr<Graph>* optimized_graph) {
 #ifndef IS_MOBILE_PLATFORM
+  if (session_options_->config.graph_options().place_pruned_graph()) {
+    return errors::InvalidArgument("Can't optimize a pruned graph");
+  }
+
   const RewriterConfig& rewrite_options =
       session_options_->config.graph_options().rewrite_options();
 

tensorflow/core/grappler/grappler_item.cc

@@ -26,6 +26,16 @@ limitations under the License.
 namespace tensorflow {
 namespace grappler {
 
+GrapplerItem::GrapplerItem(const GrapplerItem& other, GraphDef&& graphDef) {
+  id = other.id;
+  feed = other.feed;
+  fetch = other.fetch;
+  init_ops = other.init_ops;
+  expected_init_time = other.expected_init_time;
+  queue_runners = other.queue_runners;
+  graph.Swap(&graphDef);
+}
+
 std::vector<const NodeDef*> GrapplerItem::MainOpsFanin() const {
   return ComputeTransitiveFanin(graph, fetch);
 }

tensorflow/core/grappler/grappler_item.h

@@ -34,6 +34,9 @@ namespace grappler {
 // nodes, and potentially a set of nodes to feed.
 // TODO(volunteer_needed): turn this struct into a class.
 struct GrapplerItem {
+  GrapplerItem() {}
+  GrapplerItem(const GrapplerItem& other, GraphDef&& graphDef);
+
   string id;  // A unique id for this item
 
   // Inputs

tensorflow/core/grappler/optimizers/meta_optimizer.cc

@@ -103,8 +103,7 @@ Status MetaOptimizer::Optimize(Cluster* cluster, const GrapplerItem& item,
       TF_RETURN_IF_ERROR(optimizer->Optimize(cluster, item, optimized_graph));
       already_optimized = true;
     } else {
-      GrapplerItem optimized_item = item;
-      optimized_item.graph = *optimized_graph;
+      GrapplerItem optimized_item(item, std::move(*optimized_graph));
       TF_RETURN_IF_ERROR(
           optimizer->Optimize(cluster, optimized_item, optimized_graph));
     }