Canvas2D Performance: fix the bottleneck of hasInstance during JS binding -- overloading

Source/bindings/scripts/v8_types.py

 # Copyright (C) 2013 Google Inc. All rights reserved.
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@@ skipping 516 matching lines @@
     if base_idl_type in V8_VALUE_TO_CPP_VALUE:
         cpp_expression_format = V8_VALUE_TO_CPP_VALUE[base_idl_type]
     elif idl_type.is_typed_array_element_type:
         cpp_expression_format = (
             '{v8_value}->Is{idl_type}() ? '
             'V8{idl_type}::toImpl(v8::Handle<v8::{idl_type}>::Cast({v8_value})) : 0')
     elif idl_type.is_dictionary:
         cpp_expression_format = 'V8{idl_type}::toImpl({isolate}, {v8_value}, exceptionState)'
     else:
         cpp_expression_format = (
-            'V8{idl_type}::toImplWithTypeCheck({isolate}, {v8_value})')
+            'V8{idl_type}::toImpl(v8::Handle<v8::Object>::Cast({v8_value}))')

[Jens Widell, 2014/09/29 10:04:46]

So what you did here is remove the only type-check for a whole lot of arguments.
That's not a valid change.

This is only valid if the argument was already type-checked because of
[TypeChecking=Interface] *or* if the argument took part in overload resolution
(and was thus type-checked by the overload resolution function.)

And even then, it's also sometimes possible for the argument to be null or
undefined, in which case the cast here is still invalid.

 
     return cpp_expression_format.format(arguments=arguments, idl_type=base_idl_type, v8_value=v8_value, isolate=isolate)
 
 
 def v8_value_to_cpp_value_array_or_sequence(native_array_element_type, v8_value, index, isolate='info.GetIsolate()'):
     # Index is None for setters, index (starting at 0) for method arguments,
     # and is used to provide a human-readable exception message
     if index is None:
         index = 0  # special case, meaning "setter"
     else:
@@ skipping 316 matching lines @@
 
 
 def is_explicit_nullable(idl_type):
     # Nullable type that isn't implicit nullable (see above.) For such types,
     # we use Nullable<T> or similar explicit ways to represent a null value.
     return idl_type.is_nullable and not idl_type.is_implicit_nullable
 
 IdlTypeBase.is_implicit_nullable = property(is_implicit_nullable)
 IdlUnionType.is_implicit_nullable = False
 IdlTypeBase.is_explicit_nullable = property(is_explicit_nullable)