Count closures using the feedback vector cell map, specialize if count==1.

src/compiler/pipeline.cc

Index: src/compiler/pipeline.cc
diff --git a/src/compiler/pipeline.cc b/src/compiler/pipeline.cc
index 8a11656b526f16053e6dbc645317d62e66bb7af1..584ae021da811ad93ad65f4ac05f8173c7a2cf44 100644
--- a/src/compiler/pipeline.cc
+++ b/src/compiler/pipeline.cc
@@ -587,6 +587,10 @@ PipelineCompilationJob::Status PipelineCompilationJob::PrepareJobImpl() {
     if (FLAG_turbo_loop_peeling) {
       info()->MarkAsLoopPeelingEnabled();
     }
+    if (info()->closure()->feedback_vector_cell()->map() ==
+        isolate()->heap()->one_closure_cell_map()) {
+      info()->MarkAsFunctionContextSpecializing();

[Michael Starzinger, 2017/02/10 14:04:27]

suggestion: As discussed offline, we could move this down two or three lines
into the below condition to make sure we only enable the optimization in cases
where we have deoptimization support enabled.

[Jarin, 2017/02/10 14:53:06]

Done.

+    }
   }
   if (info()->is_optimizing_from_bytecode() ||
       !info()->shared_info()->asm_function()) {