diff --git a/js/src/jsapi.cpp b/js/src/jsapi.cpp
index caa407eac58..aecc9020506 100644
--- a/js/src/jsapi.cpp
+++ b/js/src/jsapi.cpp
@@ -4278,7 +4278,7 @@ JS_CloneFunctionObject(JSContext *cx, JSObject *funobj, JSObject *parent)
      * but looking up the property by name instead of frame slot.
      */
     if (FUN_FLAT_CLOSURE(fun)) {
-        JS_ASSERT(DSLOTS_IS_NOT_NULL(funobj));
+        JS_ASSERT(funobj->dslots);
         if (!js_EnsureReservedSlots(cx, clone,
                                     fun->countInterpretedReservedSlots())) {
             return NULL;
diff --git a/js/src/jsarray.cpp b/js/src/jsarray.cpp
index 6dbc702695f..8264b42f515 100644
--- a/js/src/jsarray.cpp
+++ b/js/src/jsarray.cpp
@@ -315,9 +315,9 @@ ResizeSlots(JSContext *cx, JSObject *obj, uint32 oldlen, uint32 newlen,
     jsval *slots, *newslots;
 
     if (newlen == 0) {
-        if (DSLOTS_IS_NOT_NULL(obj)) {
+        if (obj->dslots) {
             cx->free(obj->dslots - 1);
-            obj->dslots = DSLOTS_NULL_RESIZE_SLOTS;
+            obj->dslots = NULL;
         }
         return JS_TRUE;
     }
@@ -327,7 +327,7 @@ ResizeSlots(JSContext *cx, JSObject *obj, uint32 oldlen, uint32 newlen,
         return JS_FALSE;
     }
 
-    slots = DSLOTS_IS_NOT_NULL(obj) ? obj->dslots - 1 : NULL;
+    slots = obj->dslots ? obj->dslots - 1 : NULL;
     newslots = (jsval *) cx->realloc(slots, (size_t(newlen) + 1) * sizeof(jsval));
     if (!newslots)
         return JS_FALSE;
@@ -1210,9 +1210,9 @@ slowarray_enumerate(JSContext *cx, JSObject *obj, JSIterateOp enum_op,
 static void
 array_finalize(JSContext *cx, JSObject *obj)
 {
-    if (DSLOTS_IS_NOT_NULL(obj))
+    if (obj->dslots)
         cx->free(obj->dslots - 1);
-    obj->dslots = DSLOTS_NULL_ARRAY_FINALIZE;
+    obj->dslots = NULL;
 }
 
 static void
@@ -1826,7 +1826,7 @@ array_reverse(JSContext *cx, uintN argc, jsval *vp)
 
     if (OBJ_IS_DENSE_ARRAY(cx, obj) && !js_PrototypeHasIndexedProperties(cx, obj)) {
         /* An empty array or an array with no elements is already reversed. */
-        if (len == 0 || !DSLOTS_IS_NOT_NULL(obj))
+        if (len == 0 || !obj->dslots)
             return JS_TRUE;
 
         /*
@@ -2553,7 +2553,7 @@ array_shift(JSContext *cx, uintN argc, jsval *vp)
 
         if (OBJ_IS_DENSE_ARRAY(cx, obj) && !js_PrototypeHasIndexedProperties(cx, obj) &&
             length < js_DenseArrayCapacity(obj)) {
-            if (JS_LIKELY(DSLOTS_IS_NOT_NULL(obj))) {
+            if (JS_LIKELY(obj->dslots != NULL)) {
                 *vp = obj->dslots[0];
                 if (*vp == JSVAL_HOLE)
                     *vp = JSVAL_VOID;
@@ -3420,7 +3420,7 @@ js_NewEmptyArray(JSContext* cx, JSObject* proto)
     obj->fslots[JSSLOT_ARRAY_COUNT] = 0;
     for (unsigned i = JSSLOT_ARRAY_COUNT + 1; i != JS_INITIAL_NSLOTS; ++i)
         obj->fslots[i] = JSVAL_VOID;
-    obj->dslots = DSLOTS_NULL_NEW_EMPTY_ARRAY;
+    obj->dslots = NULL;
     return obj;
 }
 #ifdef JS_TRACER
diff --git a/js/src/jsarray.h b/js/src/jsarray.h
index ff54ceb326d..9a44afd992b 100644
--- a/js/src/jsarray.h
+++ b/js/src/jsarray.h
@@ -123,14 +123,14 @@ static JS_INLINE uint32
 js_DenseArrayCapacity(JSObject *obj)
 {
     JS_ASSERT(js_IsDenseArray(obj));
-    return DSLOTS_IS_NOT_NULL(obj) ? (uint32) obj->dslots[-1] : 0;
+    return obj->dslots ? (uint32) obj->dslots[-1] : 0;
 }
 
 static JS_INLINE void
 js_SetDenseArrayCapacity(JSObject *obj, uint32 capacity)
 {
     JS_ASSERT(js_IsDenseArray(obj));
-    JS_ASSERT(DSLOTS_IS_NOT_NULL(obj));
+    JS_ASSERT(obj->dslots);
     obj->dslots[-1] = (jsval) capacity;
 }
 
diff --git a/js/src/jsbuiltins.cpp b/js/src/jsbuiltins.cpp
index 6a56e5ba035..c87ba1e4592 100644
--- a/js/src/jsbuiltins.cpp
+++ b/js/src/jsbuiltins.cpp
@@ -422,8 +422,7 @@ js_NewNullClosure(JSContext* cx, JSObject* funobj, JSObject* proto, JSObject* pa
 
     closure->map = scope;
     closure->init(&js_FunctionClass, proto, parent,
-                  reinterpret_cast<jsval>(fun),
-                  DSLOTS_NULL_INIT_CLOSURE);
+                  reinterpret_cast<jsval>(fun));
     return closure;
 }
 JS_DEFINE_CALLINFO_4(extern, OBJECT, js_NewNullClosure, CONTEXT, OBJECT, OBJECT, OBJECT, 0, 0)
diff --git a/js/src/jsdbgapi.cpp b/js/src/jsdbgapi.cpp
index 4ec3a9c9ea8..68063b1e8e2 100644
--- a/js/src/jsdbgapi.cpp
+++ b/js/src/jsdbgapi.cpp
@@ -1595,7 +1595,7 @@ JS_GetObjectTotalSize(JSContext *cx, JSObject *obj)
     JSScope *scope;
 
     nbytes = sizeof *obj;
-    if (DSLOTS_IS_NOT_NULL(obj)) {
+    if (obj->dslots) {
         nbytes += ((uint32)obj->dslots[-1] - JS_INITIAL_NSLOTS + 1)
                   * sizeof obj->dslots[0];
     }
diff --git a/js/src/jsobj.cpp b/js/src/jsobj.cpp
index 9373ce90912..b0d08f8c0f4 100644
--- a/js/src/jsobj.cpp
+++ b/js/src/jsobj.cpp
@@ -2099,7 +2099,6 @@ obj_keys(JSContext *cx, uintN argc, jsval *vp)
         return JS_FALSE;
     *vp = OBJECT_TO_JSVAL(aobj);
 
-    JS_ASSERT(DSLOTS_IS_NOT_NULL(aobj));
     jsval *slots = aobj->dslots;
     size_t len = ida.length();
     JS_ASSERT(js_DenseArrayCapacity(aobj) >= len);
@@ -2194,8 +2193,6 @@ InitScopeForObject(JSContext* cx, JSObject* obj, JSObject* proto, JSObjectOps* o
         scope = OBJ_SCOPE(proto)->getEmptyScope(cx, clasp);
         if (!scope)
             goto bad;
-        if (!DSLOTS_IS_NOT_NULL(obj))
-            DSLOTS_BUMP_1(obj);
     } else {
         scope = JSScope::create(cx, ops, clasp, obj, js_GenerateShape(cx, false));
         if (!scope)
@@ -2262,8 +2259,7 @@ js_NewObjectWithGivenProto(JSContext *cx, JSClass *clasp, JSObject *proto,
     obj->init(clasp,
               proto,
               (!parent && proto) ? proto->getParent() : parent,
-              JSObject::defaultPrivate(clasp),
-              OPS_IS_NATIVE(ops) ? DSLOTS_NULL_INIT_OBJECT_NATIVE : DSLOTS_NULL_INIT_OBJECT_NONNATIVE);
+              JSObject::defaultPrivate(clasp));
 
     if (OPS_IS_NATIVE(ops)) {
         if (!InitScopeForObject(cx, obj, proto, ops)) {
@@ -2354,7 +2350,7 @@ NewNativeObject(JSContext* cx, JSClass* clasp, JSObject* proto,
     if (!obj)
         return NULL;
 
-    obj->init(clasp, proto, parent, privateSlotValue, DSLOTS_NULL_INIT_NATIVE);
+    obj->init(clasp, proto, parent, privateSlotValue);
     return InitScopeForObject(cx, obj, proto, &js_ObjectOps) ? obj : NULL;
 }
 
@@ -2706,7 +2702,7 @@ js_CloneBlockObject(JSContext *cx, JSObject *proto, JSStackFrame *fp)
     JS_ASSERT(scope->freeslot == JSSLOT_BLOCK_DEPTH + 1);
     for (uint32 i = JSSLOT_BLOCK_DEPTH + 1; i < JS_INITIAL_NSLOTS; ++i)
         clone->fslots[i] = JSVAL_VOID;
-    clone->dslots = DSLOTS_NULL_CLONE_BLOCK_OBJECT;
+    clone->dslots = NULL;
     JS_ASSERT(OBJ_IS_CLONED_BLOCK(clone));
     return clone;
 }
@@ -3142,7 +3138,7 @@ bad:
 static bool
 AllocSlots(JSContext *cx, JSObject *obj, size_t nslots)
 {
-    JS_ASSERT(!DSLOTS_IS_NOT_NULL(obj));
+    JS_ASSERT(!obj->dslots);
     JS_ASSERT(nslots > JS_INITIAL_NSLOTS);
 
     jsval* slots;
@@ -3198,7 +3194,7 @@ js_GrowSlots(JSContext *cx, JSObject *obj, size_t nslots)
      * If nothing was allocated yet, treat it as initial allocation (but with
      * the exponential growth algorithm applied).
      */
-    jsval* slots = DSLOTS_NORMALIZE(obj);
+    jsval* slots = obj->dslots;
     if (!slots)
         return AllocSlots(cx, obj, nslots);
 
@@ -3219,7 +3215,7 @@ js_GrowSlots(JSContext *cx, JSObject *obj, size_t nslots)
 void
 js_ShrinkSlots(JSContext *cx, JSObject *obj, size_t nslots)
 {
-    jsval* slots = DSLOTS_NORMALIZE(obj);
+    jsval* slots = obj->dslots;
 
     /* Nothing to shrink? */
     if (!slots)
@@ -3230,7 +3226,7 @@ js_ShrinkSlots(JSContext *cx, JSObject *obj, size_t nslots)
 
     if (nslots <= JS_INITIAL_NSLOTS) {
         cx->free(slots - 1);
-        obj->dslots = DSLOTS_NULL_SHRINK_SLOTS;
+        obj->dslots = NULL;
     } else {
         size_t nwords = SLOTS_TO_DYNAMIC_WORDS(nslots);
         slots = (jsval*) cx->realloc(slots - 1, nwords * sizeof(jsval));
@@ -3243,7 +3239,7 @@ bool
 js_EnsureReservedSlots(JSContext *cx, JSObject *obj, size_t nreserved)
 {
     JS_ASSERT(OBJ_IS_NATIVE(obj));
-    JS_ASSERT(!DSLOTS_IS_NOT_NULL(obj));
+    JS_ASSERT(!obj->dslots);
 
     uintN nslots = JSSLOT_FREE(STOBJ_GET_CLASS(obj)) + nreserved;
     if (nslots > STOBJ_NSLOTS(obj) && !AllocSlots(cx, obj, nslots))
@@ -3299,8 +3295,7 @@ js_NewNativeObject(JSContext *cx, JSClass *clasp, JSObject *proto,
         return NULL;
     }
     obj->map = scope;
-    obj->init(clasp, proto, proto->getParent(), privateSlotValue,
-              DSLOTS_NULL_INIT_JSNATIVE);
+    obj->init(clasp, proto, proto->getParent(), privateSlotValue);
     return obj;
 }
 
@@ -6024,7 +6019,7 @@ js_SetReservedSlot(JSContext *cx, JSObject *obj, uint32 index, jsval v)
         return false;
 
     uint32 slot = JSSLOT_START(clasp) + index;
-    if (slot >= JS_INITIAL_NSLOTS && !DSLOTS_IS_NOT_NULL(obj)) {
+    if (slot >= JS_INITIAL_NSLOTS && !obj->dslots) {
         /*
          * At this point, obj may or may not own scope, and we may or may not
          * need to allocate dslots. If scope is shared, scope->freeslot may not
diff --git a/js/src/jsobj.h b/js/src/jsobj.h
index 92f0bb9d33a..7bbdefe22ad 100644
--- a/js/src/jsobj.h
+++ b/js/src/jsobj.h
@@ -233,7 +233,7 @@ struct JSObject {
 
     /* The map field is not initialized here and should be set separately. */
     void init(JSClass *clasp, JSObject *proto, JSObject *parent,
-              jsval privateSlotValue, jsval *nullPtr) {
+              jsval privateSlotValue) {
         JS_ASSERT(((jsuword) clasp & 3) == 0);
         JS_STATIC_ASSERT(JSSLOT_PRIVATE + 3 == JS_INITIAL_NSLOTS);
         JS_ASSERT_IF(clasp->flags & JSCLASS_HAS_PRIVATE,
@@ -248,7 +248,7 @@ struct JSObject {
         fslots[JSSLOT_PRIVATE] = privateSlotValue;
         fslots[JSSLOT_PRIVATE + 1] = JSVAL_VOID;
         fslots[JSSLOT_PRIVATE + 2] = JSVAL_VOID;
-        dslots = nullPtr;
+        dslots = NULL;
     }
 
     JSBool lookupProperty(JSContext *cx, jsid id,
@@ -349,7 +349,7 @@ struct JSObject {
  */
 
 #define STOBJ_NSLOTS(obj)                                                     \
-    (DSLOTS_IS_NOT_NULL(obj) ? (uint32)(obj)->dslots[-1] : (uint32)JS_INITIAL_NSLOTS)
+    ((obj)->dslots ? (uint32)(obj)->dslots[-1] : (uint32)JS_INITIAL_NSLOTS)
 
 inline jsval&
 STOBJ_GET_SLOT(JSObject *obj, uintN slot)
@@ -663,7 +663,7 @@ js_ShrinkSlots(JSContext *cx, JSObject *obj, size_t nslots);
 static inline void
 js_FreeSlots(JSContext *cx, JSObject *obj)
 {
-    if (DSLOTS_IS_NOT_NULL(obj))
+    if (obj->dslots)
         js_ShrinkSlots(cx, obj, 0);
 }
 
diff --git a/js/src/jsops.cpp b/js/src/jsops.cpp
index fe761515d58..06c6bb1ee61 100644
--- a/js/src/jsops.cpp
+++ b/js/src/jsops.cpp
@@ -1522,10 +1522,6 @@ BEGIN_CASE(JSOP_GETXPROP)
                 } else if (PCVAL_IS_SLOT(entry->vword)) {
                     slot = PCVAL_TO_SLOT(entry->vword);
                     JS_ASSERT(slot < OBJ_SCOPE(obj2)->freeslot);
-                    if (!DSLOTS_IS_NOT_NULL(obj2) &&
-                        OBJ_SHAPE(obj2) >= SHAPE_OVERFLOW_BIT) {
-                        DSLOTS_BUMP_2(obj2);
-                    }
                     rval = LOCKED_OBJ_GET_SLOT(obj2, slot);
                 } else {
                     JS_ASSERT(PCVAL_IS_SPROP(entry->vword));
@@ -2862,7 +2858,7 @@ BEGIN_CASE(JSOP_CALLDSLOT)
     JS_ASSERT(fp->argv);
     obj = JSVAL_TO_OBJECT(fp->argv[-2]);
     JS_ASSERT(obj);
-    JS_ASSERT(DSLOTS_IS_NOT_NULL(obj));
+    JS_ASSERT(obj->dslots);
 
     index = GET_UINT16(regs.pc);
     JS_ASSERT(JS_INITIAL_NSLOTS + index < jsatomid(obj->dslots[-1]));
diff --git a/js/src/jsprvtd.h b/js/src/jsprvtd.h
index 71c2edd5c79..8ce4784f155 100644
--- a/js/src/jsprvtd.h
+++ b/js/src/jsprvtd.h
@@ -370,24 +370,4 @@ extern JSBool js_CStringsAreUTF8;
  */
 #define JS_ARGS_LENGTH_MAX      (JS_BIT(24) - 1)
 
-#define DSLOTS_NULL_SHIFT                 8
-#define DSLOTS_NULL_RESIZE_SLOTS          ((jsval*)  (1 << DSLOTS_NULL_SHIFT))
-#define DSLOTS_NULL_ARRAY_FINALIZE        ((jsval*)  (2 << DSLOTS_NULL_SHIFT))
-#define DSLOTS_NULL_NEW_EMPTY_ARRAY       ((jsval*)  (3 << DSLOTS_NULL_SHIFT))
-#define DSLOTS_NULL_CLONE_BLOCK_OBJECT    ((jsval*)  (4 << DSLOTS_NULL_SHIFT))
-#define DSLOTS_NULL_SHRINK_SLOTS          ((jsval*)  (5 << DSLOTS_NULL_SHIFT))
-
-#define DSLOTS_NULL_INIT_OBJECT_NATIVE    ((jsval*)  (6 << DSLOTS_NULL_SHIFT))
-#define DSLOTS_NULL_INIT_OBJECT_NONNATIVE ((jsval*)  (7 << DSLOTS_NULL_SHIFT))
-#define DSLOTS_NULL_INIT_NATIVE           ((jsval*)  (8 << DSLOTS_NULL_SHIFT))
-#define DSLOTS_NULL_INIT_JSNATIVE         ((jsval*)  (9 << DSLOTS_NULL_SHIFT))
-#define DSLOTS_NULL_INIT_CLOSURE          ((jsval*) (10 << DSLOTS_NULL_SHIFT))
-
-#define DSLOTS_NULL_LIMIT                 (16 << DSLOTS_NULL_SHIFT)
-
-#define DSLOTS_IS_NOT_NULL(obj)           (uintptr_t(obj->dslots) >= DSLOTS_NULL_LIMIT)
-#define DSLOTS_NORMALIZE(obj) (DSLOTS_IS_NOT_NULL(obj) ? (obj)->dslots : NULL)
-#define DSLOTS_BUMP_1(obj)      (obj->dslots = (jsval*) (uintptr_t((obj)->dslots) | (1 << (DSLOTS_NULL_SHIFT-1))))
-#define DSLOTS_BUMP_2(obj)      (obj->dslots = (jsval*) (uintptr_t((obj)->dslots) | (1 << (DSLOTS_NULL_SHIFT-2))))
-
 #endif /* jsprvtd_h___ */
diff --git a/js/src/jstracer.cpp b/js/src/jstracer.cpp
index 86e4be37130..b8f8f872aab 100644
--- a/js/src/jstracer.cpp
+++ b/js/src/jstracer.cpp
@@ -280,7 +280,6 @@ js_InitJITStatsClass(JSContext *cx, JSObject *glob)
 #define INS_ATOM(atom)        INS_CONSTSTR(ATOM_TO_STRING(atom))
 #define INS_NULL()            INS_CONSTPTR(NULL)
 #define INS_VOID()            INS_CONST(JSVAL_TO_SPECIAL(JSVAL_VOID))
-#define INS_DSLOTSNULL(ins)   lir->ins2(LIR_pult, (ins), INS_CONSTPTR((jsval*) DSLOTS_NULL_LIMIT))
 
 static avmplus::AvmCore s_core = avmplus::AvmCore();
 static avmplus::AvmCore* core = &s_core;
@@ -12642,7 +12641,7 @@ TraceRecorder::denseArrayElement(jsval& oval, jsval& ival, jsval*& vp, LIns*& v_
                                    NULL);
 
         /* If dslots is NULL, stay on trace (and read value as undefined). */
-        LIns* br3 = lir->insBranch(LIR_jt, INS_DSLOTSNULL(dslots_ins), NULL);
+        LIns* br3 = lir->insBranch(LIR_jt, lir->ins_peq0(dslots_ins), NULL);
 
         /* If not idx < capacity, stay on trace (and read value as undefined). */
         LIns* br4 = lir->insBranch(LIR_jf,
@@ -12684,7 +12683,7 @@ TraceRecorder::denseArrayElement(jsval& oval, jsval& ival, jsval*& vp, LIns*& v_
 
     /* dslots must not be NULL */
     guard(false,
-          INS_DSLOTSNULL(dslots_ins),
+          lir->ins_peq0(dslots_ins),
           exit);
 
     /* Guard array capacity */