Skip canonicalization check in LStoreKeyedFastDoubleElement when it is not needed:

src/ia32/lithium-codegen-ia32.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 3442 matching lines @@
                    kSaveFPRegs,
                    EMIT_REMEMBERED_SET,
                    check_needed);
   }
 }
 
 
 void LCodeGen::DoStoreKeyedFastDoubleElement(
     LStoreKeyedFastDoubleElement* instr) {
   XMMRegister value = ToDoubleRegister(instr->value());
-  Label have_value;
 
-  __ ucomisd(value, value);
-  __ j(parity_odd, &have_value);  // NaN.
+  if (instr->NeedsCanonicalization()) {
+    Label have_value;
 
-  ExternalReference canonical_nan_reference =
-      ExternalReference::address_of_canonical_non_hole_nan();
-  __ movdbl(value, Operand::StaticVariable(canonical_nan_reference));
-  __ bind(&have_value);
+    __ ucomisd(value, value);
+    __ j(parity_odd, &have_value);  // NaN.
+
+    ExternalReference canonical_nan_reference =
+        ExternalReference::address_of_canonical_non_hole_nan();
+    __ movdbl(value, Operand::StaticVariable(canonical_nan_reference));
+    __ bind(&have_value);
+  }
 
   Operand double_store_operand = BuildFastArrayOperand(
       instr->elements(), instr->key(), FAST_DOUBLE_ELEMENTS,
       FixedDoubleArray::kHeaderSize - kHeapObjectTag);
   __ movdbl(double_store_operand, value);
 }
 
 
 void LCodeGen::DoStoreKeyedGeneric(LStoreKeyedGeneric* instr) {
   ASSERT(ToRegister(instr->context()).is(esi));
@@ skipping 1513 matching lines @@
                               FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32