Simplify Hydrogen code stubs with variable argument count

src/code-stubs.h

Index: src/code-stubs.h
diff --git a/src/code-stubs.h b/src/code-stubs.h
index b56a3ecfcb24b94535408b6734aeb8364aa0924a..8f1b686743317a39f95b764933a901de4b788214 100644
--- a/src/code-stubs.h
+++ b/src/code-stubs.h
@@ -277,23 +277,23 @@ class PlatformCodeStub : public CodeStub {
 
 
 enum StubFunctionMode { NOT_JS_FUNCTION_STUB_MODE, JS_FUNCTION_STUB_MODE };
-
+enum HandlerArgumentsMode { DONT_PASS_ARGUMENTS, PASS_ARGUMENTS };
 
 struct CodeStubInterfaceDescriptor {
   CodeStubInterfaceDescriptor();
   int register_param_count_;
+
   Register stack_parameter_count_;
   // if hint_stack_parameter_count_ > 0, the code stub can optimize the
   // return sequence. Default value is -1, which means it is ignored.
   int hint_stack_parameter_count_;
   StubFunctionMode function_mode_;
   Register* register_params_;
+
   Address deoptimization_handler_;
+  HandlerArgumentsMode handler_arguments_mode_;
 
   int environment_length() const {
-    if (stack_parameter_count_.is_valid()) {
-      return register_param_count_ + 1;
-    }
     return register_param_count_;
   }
 
@@ -302,6 +302,9 @@ struct CodeStubInterfaceDescriptor {
   void SetMissHandler(ExternalReference handler) {
     miss_handler_ = handler;
     has_miss_handler_ = true;
+    // Our miss handler infrastructure doesn't currently support
+    // variable stack parameter counts.
+    ASSERT(!stack_parameter_count_.is_valid());
   }
 
   ExternalReference miss_handler() {
@@ -313,18 +316,27 @@ struct CodeStubInterfaceDescriptor {
     return has_miss_handler_;
   }
 
+  Register GetParameterRegister(int index) {
+    return register_params_[index];
+  }
+
+  bool IsParameterCountRegister(int index) {
+    return GetParameterRegister(index).is(stack_parameter_count_);
+  }
+
+  int GetHandlerParameterCount() {
+    int params = environment_length();
+    if (handler_arguments_mode_ == PASS_ARGUMENTS) {
+      params += 1;
+    }
+    return params;
+  }
+
  private:
   ExternalReference miss_handler_;
   bool has_miss_handler_;
 };
 
-// A helper to make up for the fact that type Register is not fully
-// defined outside of the platform directories
-#define DESCRIPTOR_GET_PARAMETER_REGISTER(descriptor, index) \
-  ((index) == (descriptor)->register_param_count_)           \
-      ? (descriptor)->stack_parameter_count_                 \
-      : (descriptor)->register_params_[(index)]
-
 
 class HydrogenCodeStub : public CodeStub {
  public: