VM: Explicitly load function and context before calling a closure.

runtime/vm/object.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/object.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/cpu.h"
@@ skipping 13830 matching lines @@
   if (IsCanonical() || IsMalformed()) {
     ASSERT(IsMalformed() || TypeArguments::Handle(arguments()).IsOld());
     return this->raw();
   }
   Isolate* isolate = Isolate::Current();
   Type& type = Type::Handle(isolate);
   const Class& cls = Class::Handle(isolate, type_class());
   if (cls.raw() == Object::dynamic_class() && (isolate != Dart::vm_isolate())) {
     return Object::dynamic_type();
   }
+  if (cls.raw() == Object::function_class() &&

[srdjan, 2014/04/30 15:41:58]

cls.IsFunctionClass()

[Florian Schneider, 2014/04/30 16:02:19]

This seems equivalent and consistent with the code above, so I'd rather leave it
as is.

+      (isolate != Dart::vm_isolate())) {
+    return Object::dynamic_type();

[srdjan, 2014/04/30 15:41:58]

I would like to have Regis look into this change.

[Florian Schneider, 2014/04/30 16:02:19]

Now that I look at it again, actually, this should return 
Isolate::Current()->object_store()->function_type();

The problem here is that the flow-graph propagation want to canonicalize a type
that's stored in the VM isolate heap (read-only).

This occurs because we pass a Function value around in the IL (as input operand
to closure calls). 

[Florian Schneider, 2014/04/30 16:05:24]

No, not function_type, but the type corresponding to the RawFunction VM class,
not the Dart class.

[regis, 2014/04/30 16:46:39]

I fail to see what problem you are trying to solve here.
Why do you need a canonical Function type across all isolates?

+  }
   // Fast canonical lookup/registry for simple types.
   if ((cls.NumTypeArguments() == 0) && !cls.IsSignatureClass()) {
     type = cls.CanonicalType();
     if (type.IsNull()) {
       ASSERT(!cls.raw()->IsVMHeapObject() || (isolate == Dart::vm_isolate()));
       cls.set_canonical_types(*this);
       SetCanonical();
       return this->raw();
     }
     ASSERT(this->Equals(type));
@@ skipping 4808 matching lines @@
   return tag_label.ToCString();
 }
 
 
 void UserTag::PrintJSONImpl(JSONStream* stream, bool ref) const {
   Instance::PrintJSONImpl(stream, ref);
 }
 
 
 }  // namespace dart