Use mutable heapnumbers to store doubles in fields.

src/arm/ic-arm.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 1162 matching lines @@
   __ Push(r2, r1, r0);
 
   ExternalReference ref = miss_mode == MISS_FORCE_GENERIC
       ? ExternalReference(IC_Utility(kKeyedStoreIC_MissForceGeneric),
                           masm->isolate())
       : ExternalReference(IC_Utility(kKeyedStoreIC_Miss), masm->isolate());
   __ TailCallExternalReference(ref, 3, 1);
 }
 
 
+void StoreIC::GenerateSlow(MacroAssembler* masm) {
+  // ---------- S t a t e --------------
+  //  -- r0     : value
+  //  -- r2     : key
+  //  -- r1     : receiver
+  //  -- lr     : return address
+  // -----------------------------------
+
+  // Push receiver, key and value for runtime call.
+  __ Push(r1, r2, r0);
+
+  // The slow case calls into the runtime to complete the store without causing
+  // an IC miss that would otherwise cause a transition to the generic stub.
+  ExternalReference ref =
+      ExternalReference(IC_Utility(kKeyedStoreIC_Slow), masm->isolate());
+  __ TailCallExternalReference(ref, 3, 1);
+}
+
+
 void KeyedStoreIC::GenerateSlow(MacroAssembler* masm) {
   // ---------- S t a t e --------------
   //  -- r0     : value
   //  -- r1     : key
   //  -- r2     : receiver
   //  -- lr     : return address
   // -----------------------------------
 
   // Push receiver, key and value for runtime call.
   __ Push(r2, r1, r0);
@@ skipping 483 matching lines @@
   } else {
     ASSERT(Assembler::GetCondition(branch_instr) == ne);
     patcher.EmitCondition(eq);
   }
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM