Make stack_parameter_count a plain register.

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 144 matching lines @@
   graph()->set_undefined_constant(undefined_constant);
 
   for (int i = 0; i < param_count; ++i) {
     HParameter* param =
         Add<HParameter>(i, HParameter::REGISTER_PARAMETER);
     start_environment->Bind(i, param);
     parameters_[i] = param;
   }
 
   HInstruction* stack_parameter_count;
-  if (descriptor_->stack_parameter_count_ != NULL) {
+  if (descriptor_->stack_parameter_count_.is_valid()) {
     ASSERT(descriptor_->environment_length() == (param_count + 1));
     stack_parameter_count = New<HParameter>(param_count,
                                             HParameter::REGISTER_PARAMETER,
                                             Representation::Integer32());
     stack_parameter_count->set_type(HType::Smi());
     // It's essential to bind this value to the environment in case of deopt.
     AddInstruction(stack_parameter_count);
     start_environment->Bind(param_count, stack_parameter_count);
     arguments_length_ = stack_parameter_count;
   } else {
@@ skipping 115 matching lines @@
   CodeStubInterfaceDescriptor* descriptor =
       isolate->code_stub_interface_descriptor(major_key);
   if (descriptor->register_param_count_ < 0) {
     stub->InitializeInterfaceDescriptor(isolate, descriptor);
   }
 
   // If we are uninitialized we can use a light-weight stub to enter
   // the runtime that is significantly faster than using the standard
   // stub-failure deopt mechanism.
   if (stub->IsUninitialized() && descriptor->has_miss_handler()) {
-    ASSERT(descriptor->stack_parameter_count_ == NULL);
+    ASSERT(!descriptor->stack_parameter_count_.is_valid());
     return stub->GenerateLightweightMissCode(isolate);
   }
   ElapsedTimer timer;
   if (FLAG_profile_hydrogen_code_stub_compilation) {
     timer.Start();
   }
   CodeStubGraphBuilder<Stub> builder(isolate, stub);
   LChunk* chunk = OptimizeGraph(builder.CreateGraph());
   Handle<Code> code = chunk->Codegen();
   if (FLAG_profile_hydrogen_code_stub_compilation) {
@@ skipping 930 matching lines @@
   return js_function;
 }
 
 
 Handle<Code> FastNewClosureStub::GenerateCode(Isolate* isolate) {
   return DoGenerateCode(isolate, this);
 }
 
 
 } }  // namespace v8::internal