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

src/compiler/pipeline.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/pipeline.h"
 
 #include <fstream>  // NOLINT(readability/streams)
 #include <memory>
 #include <sstream>
 
@@ skipping 569 matching lines @@
       info()->MarkAsFrameSpecializing();
     }
     info()->MarkAsFunctionContextSpecializing();
   } else {
     if (!FLAG_always_opt) {
       info()->MarkAsBailoutOnUninitialized();
     }
     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()) {
     info()->MarkAsDeoptimizationEnabled();
     if (FLAG_inline_accessors) {
       info()->MarkAsAccessorInliningEnabled();
     }
   }
   if (!info()->is_optimizing_from_bytecode()) {
     if (!Compiler::EnsureDeoptimizationSupport(info())) return FAILED;
@@ skipping 1415 matching lines @@
   data->DeleteRegisterAllocationZone();
 }
 
 CompilationInfo* PipelineImpl::info() const { return data_->info(); }
 
 Isolate* PipelineImpl::isolate() const { return info()->isolate(); }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8