Skip canonicalization check in LStoreKeyedFastDoubleElement when it is not needed:

src/hydrogen-instructions.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2072 matching lines @@
   visited->Add(id());
   // Propagate to the left argument. If the left argument cannot be -0, then
   // the result of the sub operation cannot be either.
   if (range() == NULL || range()->CanBeMinusZero()) {
     return left();
   }
   return NULL;
 }
 
 
+bool HStoreKeyedFastDoubleElement::NeedsCanonicalization() {
+  // If value was loaded from unboxed double backing store or
+  // converted from an integer then we don't have to canonicalize it.
+  if (value()->IsLoadKeyedFastDoubleElement() ||
+      (value()->IsChange() && HChange::cast(value())->from().IsInteger32())) {
+    return false;
+  }
+  return true;
+}
+
+
 #define H_CONSTANT_INT32(val)                                                  \
 new(zone) HConstant(FACTORY->NewNumberFromInt(val, TENURED),                   \
                     Representation::Integer32())
 #define H_CONSTANT_DOUBLE(val)                                                 \
 new(zone) HConstant(FACTORY->NewNumber(val, TENURED),                          \
                     Representation::Double())
 
 #define DEFINE_NEW_H_SIMPLE_ARITHMETIC_INSTR(HInstr, op)                       \
 HInstruction* HInstr::New##HInstr(Zone* zone,                                  \
                                   HValue* context,                             \
@@ skipping 235 matching lines @@
 
 
 void HCheckPrototypeMaps::Verify() {
   HInstruction::Verify();
   ASSERT(HasNoUses());
 }
 
 #endif
 
 } }  // namespace v8::internal