Reland r25551: Allow inlining of closures with a context change.

runtime/vm/flow_graph_inliner.cc

Index: runtime/vm/flow_graph_inliner.cc
===================================================================
--- runtime/vm/flow_graph_inliner.cc	(revision 25559)
+++ runtime/vm/flow_graph_inliner.cc	(working copy)
@@ -668,11 +668,30 @@
                      &CompilerStats::graphinliner_subst_timer,
                      Isolate::Current());
 
+    // For closure calls: Store context value.
+    FlowGraph* callee_graph = call_data->callee_graph;
+    TargetEntryInstr* callee_entry =
+        callee_graph->graph_entry()->normal_entry();
+    ClosureCallInstr* closure_call = call_data->call->AsClosureCall();
+    if (closure_call != NULL) {
+      // TODO(fschneider): Avoid setting the context, if not needed.
+      Definition* closure =
+          closure_call->PushArgumentAt(0)->value()->definition();
+      LoadFieldInstr* context =
+          new LoadFieldInstr(new Value(closure),
+                             Closure::context_offset(),
+                             Type::ZoneHandle());
+      context->set_ssa_temp_index(caller_graph()->alloc_ssa_temp_index());
+      context->InsertAfter(callee_entry);
+      StoreContextInstr* set_context =
+          new StoreContextInstr(new Value(context));
+      set_context->InsertAfter(context);
+    }
+
     // Plug result in the caller graph.
-    FlowGraph* callee_graph = call_data->callee_graph;
     InlineExitCollector* exit_collector = call_data->exit_collector;
     exit_collector->PrepareGraphs(callee_graph);
-    exit_collector->ReplaceCall(callee_graph->graph_entry()->normal_entry());
+    exit_collector->ReplaceCall(callee_entry);
 
     // Replace each stub with the actual argument or the caller's constant.
     // Nulls denote optional parameters for which no actual was given.