Deoptimizer support for hydrogen stubs that accept a variable number of arguments.

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 106 matching lines @@
   graph()->set_undefined_constant(undefined_constant);
 
   for (int i = 0; i < param_count; ++i) {
     HParameter* param =
         new(zone) HParameter(i, HParameter::REGISTER_PARAMETER);
     AddInstruction(param);
     start_environment->Bind(i, param);
     parameters_[i] = param;
   }
 
+  HInstruction* stack_pop_count;

[danno, 2013/03/20 21:07:33]

nit: Can you define this down where you initially set its value?

[mvstanton, 2013/03/21 11:47:35]

Done.

   HInstruction* stack_parameter_count;
   if (descriptor_->stack_parameter_count_ != NULL) {
     ASSERT(descriptor_->environment_length() == (param_count + 1));
     stack_parameter_count = new(zone) HParameter(param_count,
-        HParameter::REGISTER_PARAMETER);
+                                                 HParameter::REGISTER_PARAMETER,
+                                                 Representation::Integer32());
     // it's essential to bind this value to the environment in case of deopt
     start_environment->Bind(param_count, stack_parameter_count);
     AddInstruction(stack_parameter_count);
     arguments_length_ = stack_parameter_count;
   } else {
     ASSERT(descriptor_->environment_length() == param_count);
     stack_parameter_count = graph()->GetConstantMinus1();
     arguments_length_ = graph()->GetConstant0();
   }
 
+  stack_pop_count = stack_parameter_count;
+
   context_ = new(zone) HContext();
   AddInstruction(context_);
   start_environment->BindContext(context_);
 
   AddSimulate(BailoutId::StubEntry());
 
   HValue* return_value = BuildCodeStub();
+
+  // We might have extra expressions to pop from the stack in addition to the
+  // arguments above
+  if (descriptor_->acting_as_js_function_) {
+    HInstruction* amount = graph()->GetConstant1();
+    stack_pop_count = AddInstruction(
+        HAdd::New(zone, context_, stack_parameter_count, amount));
+    stack_pop_count->ChangeRepresentation(Representation::Integer32());
+    stack_pop_count->ClearFlag(HValue::kCanOverflow);
+  }
+
   HReturn* hreturn_instruction = new(zone) HReturn(return_value,
                                                    context_,
-                                                   stack_parameter_count);
+                                                   stack_pop_count);
   current_block()->Finish(hreturn_instruction);
   return true;
 }
 
+
 template <class Stub>
 class CodeStubGraphBuilder: public CodeStubGraphBuilderBase {
  public:
   explicit CodeStubGraphBuilder(Stub* stub)
       : CodeStubGraphBuilderBase(Isolate::Current(), stub) {}
 
  protected:
   virtual HValue* BuildCodeStub();
   Stub* casted_stub() { return static_cast<Stub*>(stub()); }
 };
@@ skipping 209 matching lines @@
 }
 
 
 Handle<Code> ArrayNArgumentsConstructorStub::GenerateCode() {
   CodeStubGraphBuilder<ArrayNArgumentsConstructorStub> builder(this);
   LChunk* chunk = OptimizeGraph(builder.CreateGraph());
   return chunk->Codegen(Code::COMPILED_STUB);
 }
 
 } }  // namespace v8::internal