[strong] Implement strong mode semantics for the count operation.

src/hydrogen-instructions.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/base/bits.h"
 #include "src/double.h"
 #include "src/elements.h"
 #include "src/factory.h"
@@ skipping 3386 matching lines @@
     // calling ToPrimitive() on their arguments.  The standard Crankshaft
     // tagged-to-double conversion to ensure the HCompareNumericAndBranch's
     // inputs are doubles caused 'undefined' to be converted to NaN. That's
     // compatible out-of-the box with ordered relational comparisons (<, >, <=,
     // >=). However, for equality comparisons (and for 'in' and 'instanceof'),
     // it is not consistent with the spec. For example, it would cause undefined
     // == undefined (should be true) to be evaluated as NaN == NaN
     // (false). Therefore, any comparisons other than ordered relational
     // comparisons must cause a deopt when one of their arguments is undefined.
     // See also v8:1434
-    if (Token::IsOrderedRelationalCompareOp(token_)) {
+    if (Token::IsOrderedRelationalCompareOp(token_) && !is_strong(strength())) {
       SetFlag(kAllowUndefinedAsNaN);
     }
   }
   ChangeRepresentation(rep);
 }
 
 
 std::ostream& HParameter::PrintDataTo(std::ostream& os) const {  // NOLINT
   return os << index();
 }
@@ skipping 1290 matching lines @@
     case HObjectAccess::kExternalMemory:
       os << "[external-memory]";
       break;
   }
 
   return os << "@" << access.offset();
 }
 
 }  // namespace internal
 }  // namespace v8