Make context register implicit for CallInterfaceDescriptors

src/interface-descriptors.h

Index: src/interface-descriptors.h
diff --git a/src/interface-descriptors.h b/src/interface-descriptors.h
index ff6c2c3ccb75b8e17f45de630d5bf8243601d8d8..f206b55841443bd19a6ff7b37ec7334fd87e5b90 100644
--- a/src/interface-descriptors.h
+++ b/src/interface-descriptors.h
@@ -140,13 +140,15 @@ class CallInterfaceDescriptor {
   CallInterfaceDescriptor(Isolate* isolate, CallDescriptors::Key key)
       : data_(isolate->call_descriptor_data(key)) {}
 
-  int GetEnvironmentLength() const { return data()->register_param_count(); }
-
   int GetRegisterParameterCount() const {
     return data()->register_param_count();
   }
 
-  Register GetParameterRegister(int index) const {
+  int GetStackParameterCount() const {
+    return data()->function_type()->Arity() - data()->register_param_count();
+  }
+
+  Register GetRegisterParameter(int index) const {
     return data()->register_param(index);
   }
 
@@ -155,20 +157,6 @@ class CallInterfaceDescriptor {
     return data()->register_param_type(index);
   }
 
-  // "Environment" versions of parameter functions. The first register
-  // parameter (context) is not included.
-  int GetEnvironmentParameterCount() const {
-    return GetEnvironmentLength() - 1;
-  }
-
-  Register GetEnvironmentParameterRegister(int index) const {
-    return GetParameterRegister(index + 1);
-  }
-
-  Type* GetEnvironmentParameterType(int index) const {
-    return GetParameterType(index + 1);
-  }
-
   // Some platforms have extra information to associate with the descriptor.
   PlatformInterfaceDescriptor* platform_specific_descriptor() const {
     return data()->platform_specific_descriptor();