Revert "Replace HeapNumber as doublebox with an explicit MutableHeapNumber."

src/x64/stub-cache-x64.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"
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/arguments.h"
 #include "src/codegen.h"
@@ skipping 471 matching lines @@
         if (it.Done()) {
           __ j(not_equal, miss_label);
           break;
         }
         __ j(equal, &do_store, Label::kNear);
       }
       __ bind(&do_store);
     }
   } else if (representation.IsDouble()) {
     Label do_store, heap_number;
-    __ AllocateHeapNumber(storage_reg, scratch1, slow, MUTABLE);
+    __ AllocateHeapNumber(storage_reg, scratch1, slow);
 
     __ JumpIfNotSmi(value_reg, &heap_number);
     __ SmiToInteger32(scratch1, value_reg);
     __ Cvtlsi2sd(xmm0, scratch1);
     __ jmp(&do_store);
 
     __ bind(&heap_number);
     __ CheckMap(value_reg, masm->isolate()->factory()->heap_number_map(),
                 miss_label, DONT_DO_SMI_CHECK);
     __ movsd(xmm0, FieldOperand(value_reg, HeapNumber::kValueOffset));
@@ skipping 930 matching lines @@
   // -----------------------------------
   TailCallBuiltin(masm, Builtins::kKeyedLoadIC_Miss);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64