Fix GVN for polymorphic loads....

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
===================================================================
--- src/hydrogen-instructions.h	(revision 6079)
+++ src/hydrogen-instructions.h	(working copy)
@@ -2552,7 +2552,8 @@
   HLoadNamedField(HValue* object, bool is_in_object, int offset)

[Kevin Millikin (Chromium), 2010/12/20 12:34:34]

I'd rather pass is_polymorphic to the constructor and get rid of
set_is_polymorphic completely.

The way it's written, it's effectively a default parameter value (slightly worse
because it's artificially mutable), and more verbose too.

       : HUnaryOperation(object),
         is_in_object_(is_in_object),
-        offset_(offset) {
+        offset_(offset),
+        is_polymorphic_(false) {
     set_representation(Representation::Tagged());
     SetFlag(kUseGVN);
     if (is_in_object) {
@@ -2566,6 +2567,9 @@
   bool is_in_object() const { return is_in_object_; }
   int offset() const { return offset_; }
 
+  bool is_polymorphic() const { return is_polymorphic_; }
+  void set_is_polymorphic(bool b) { is_polymorphic_ = b; }
+
   virtual Representation RequiredInputRepresentation(int index) const {
     return Representation::Tagged();
   }
@@ -2582,6 +2586,7 @@
  private:
   bool is_in_object_;
   int offset_;
+  bool is_polymorphic_;
 };