Elide unnecessary context reload in generated stubs.

src/code-stubs-hydrogen.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 33 matching lines @@
   LChunk* chunk = LChunk::NewChunk(graph);
   ASSERT(chunk != NULL);
   Handle<Code> stub = chunk->Codegen(Code::COMPILED_STUB);
   return stub;
 }
 
 
 class CodeStubGraphBuilderBase : public HGraphBuilder {
  public:
   CodeStubGraphBuilderBase(Isolate* isolate, HydrogenCodeStub* stub)
-      : HGraphBuilder(&info_), info_(stub, isolate) {}
+      : HGraphBuilder(&info_), info_(stub, isolate), context_(NULL) {}
   virtual bool BuildGraph();
 
  protected:
   virtual void BuildCodeStub() = 0;
   HParameter* GetParameter(int parameter) { return parameters_[parameter]; }
   HydrogenCodeStub* stub() { return info_.code_stub(); }
+  HContext* context() { return context_; }
 
  private:
   SmartArrayPointer<HParameter*> parameters_;
   CompilationInfoWithZone info_;
+  HContext* context_;
 };
 
 
 bool CodeStubGraphBuilderBase::BuildGraph() {
   if (FLAG_trace_hydrogen) {
     PrintF("-----------------------------------------------------------\n");
     PrintF("Compiling stub using hydrogen\n");
     HTracer::Instance()->TraceCompilation(&info_);
   }
   HBasicBlock* next_block = graph()->CreateBasicBlock();
   next_block->SetInitialEnvironment(graph()->start_environment());
   HGoto* jump = new(zone()) HGoto(next_block);
   graph()->entry_block()->Finish(jump);
   set_current_block(next_block);
 
+  context_ = new(zone()) HContext();
+  AddInstruction(context_);
+
   int major_key = stub()->MajorKey();
   CodeStubInterfaceDescriptor* descriptor =
       info_.isolate()->code_stub_interface_descriptor(major_key);
   if (descriptor->register_param_count_ < 0) {
     stub()->InitializeInterfaceDescriptor(info_.isolate(), descriptor);
   }
   parameters_.Reset(new HParameter*[descriptor->register_param_count_]);
 
   HGraph* graph = this->graph();
   Zone* zone = this->zone();
@@ skipping 24 matching lines @@
 
 template <>
 void CodeStubGraphBuilder<KeyedLoadFastElementStub>::BuildCodeStub() {
   Zone* zone = this->zone();
 
   HInstruction* load = BuildUncheckedMonomorphicElementAccess(
       GetParameter(0), GetParameter(1), NULL, NULL,
       casted_stub()->is_js_array(), casted_stub()->elements_kind(), false);
   AddInstruction(load);
 
-  HReturn* ret = new(zone) HReturn(load);
+  HReturn* ret = new(zone) HReturn(load, context());
   current_block()->Finish(ret);
 }
 
 
 Handle<Code> KeyedLoadFastElementStub::GenerateCode() {
   CodeStubGraphBuilder<KeyedLoadFastElementStub> builder(this);
   return CodeFromGraph(builder.CreateGraph());
 }
 
 
 } }  // namespace v8::internal