Add allocation support to x64 macro assembler

src/ia32/builtins-ia32.cc

 // Copyright 2006-2008 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 140 matching lines @@
       __ lea(ecx, Operand(ebx, JSObject::kHeaderSize));
       __ jmp(&entry);
       __ bind(&loop);
       __ mov(Operand(ecx, 0), edx);
       __ add(Operand(ecx), Immediate(kPointerSize));
       __ bind(&entry);
       __ cmp(ecx, Operand(edi));
       __ j(less, &loop);
     }
 
-    // Mostly done with the JSObject. Add the heap tag and store the new top, so
-    // that we can continue and jump into the continuation code at any time from
-    // now on. Any failures need to undo the setting of the new top, so that the
-    // heap is in a consistent state and verifiable.
+    // Add the object tag to make the JSObject real, so that we can continue and
+    // jump into the continuation code at any time from now on. Any failures
+    // need to undo the allocation, so that the heap is in a consistent state
+    // and verifiable.
     // eax: initial map
     // ebx: JSObject
     // edi: start of next object
     __ or_(Operand(ebx), Immediate(kHeapObjectTag));
 
     // Check if a non-empty properties array is needed.
     // Allocate and initialize a FixedArray if it is.
     // eax: initial map
     // ebx: JSObject
     // edi: start of next object
@@ skipping 594 matching lines @@
   // Dont adapt arguments.
   // -------------------------------------------
   __ bind(&dont_adapt_arguments);
   __ jmp(Operand(edx));
 }
 
 
 #undef __
 
 } }  // namespace v8::internal