diff --git a/js/src/builtins.tbl b/js/src/builtins.tbl
index 655955c7c1d1..aaccbd629c7c 100644
--- a/js/src/builtins.tbl
+++ b/js/src/builtins.tbl
@@ -47,3 +47,4 @@ BUILTIN1(Math_sin,              F,      F,      jsdouble,  jsdouble,
 BUILTIN1(Math_cos,              F,      F,      jsdouble,  jsdouble,                           1, 1)
 BUILTIN2(Math_pow,              F,  F,  F,      jsdouble,  jsdouble, jsdouble,                 1, 1)
 BUILTIN1(Math_sqrt,             F,      F,      jsdouble,  jsdouble,                           1, 1)
+BUILTIN4(Array_dense_setelem,   LO, LO, LO, LO, LO, bool, JSContext*, JSObject*, jsint, jsval, 1, 1)
diff --git a/js/src/jsbuiltins.cpp b/js/src/jsbuiltins.cpp
index 5abba6df33e7..179f6fdaafce 100644
--- a/js/src/jsbuiltins.cpp
+++ b/js/src/jsbuiltins.cpp
@@ -42,6 +42,8 @@
 #include <math.h>
 
 #include "jsapi.h"
+#include "jsarray.h"
+#include "jsbool.h"
 #include "jsnum.h"
 #include "jsgc.h"
 #include "jscntxt.h"
@@ -151,6 +153,23 @@ jsdouble FASTCALL builtin_Math_sqrt(jsdouble d)
     return sqrt(d);
 }
 
+bool FASTCALL builtin_Array_dense_setelem(JSContext *cx, JSObject *obj, jsint i, jsval v)
+{
+    JS_ASSERT(OBJ_IS_DENSE_ARRAY(cx, obj));
+
+    jsuint length = ARRAY_DENSE_LENGTH(obj);
+    if ((jsuint)i < length) {
+        if (obj->dslots[i] == JSVAL_HOLE) {
+            if (i >= obj->fslots[JSSLOT_ARRAY_LENGTH])
+                obj->fslots[JSSLOT_ARRAY_LENGTH] = i + 1;
+            obj->fslots[JSSLOT_ARRAY_COUNT]++;
+        }
+        obj->dslots[i] = v;
+        return true;
+    }
+    return OBJ_SET_PROPERTY(cx, obj, INT_TO_JSID(i), &v);
+}
+
 #define LO ARGSIZE_LO
 #define F  ARGSIZE_F
 #define Q  ARGSIZE_Q
@@ -167,6 +186,8 @@ jsdouble FASTCALL builtin_Math_sqrt(jsdouble d)
     { (intptr_t)&builtin_##op, (at0 << 4) | (at1 << 2) | atr, cse, fold NAME(op) },
 #define BUILTIN3(op, at0, at1, at2, atr, tr, t0, t1, t2, cse, fold) \
     { (intptr_t)&builtin_##op, (at0 << 6) | (at1 << 4) | (at2 << 2) | atr, cse, fold NAME(op) },
+#define BUILTIN4(op, at0, at1, at2, at3, atr, tr, t0, t1, t2, t3, cse, fold)    \
+    { (intptr_t)&builtin_##op, (at0 << 8) | (at1 << 6) | (at2 << 4) | (at3 << 2) | atr, cse, fold NAME(op) },
 
 struct CallInfo builtins[] = {
 #include "builtins.tbl"
diff --git a/js/src/jstracer.cpp b/js/src/jstracer.cpp
index 0505bf206e97..aafb1a07075f 100644
--- a/js/src/jstracer.cpp
+++ b/js/src/jstracer.cpp
@@ -2326,31 +2326,19 @@ bool TraceRecorder::record_JSOP_SETELEM()
         ABORT_TRACE("not a dense array");
 
     /* check that the index is within bounds */
-    jsint idx = JSVAL_TO_INT(r);
     LIns* idx_ins = f2i(get(&r));
 
     /* we have to check that its really an integer, but this check will to go away
        once we peel the loop type down to integer for this slot */
     guard(true, lir->ins2(LIR_feq, get(&r), lir->ins1(LIR_i2f, idx_ins)));
-    if (!guardDenseArrayIndexWithinBounds(obj, idx, obj_ins, dslots_ins, idx_ins))
-        ABORT_TRACE("index out of bounds");
-
-    /* get us the address of the array slot */
-    LIns* addr = lir->ins2(LIR_add, dslots_ins,
-                           lir->ins2i(LIR_lsh, idx_ins, JS_BYTES_PER_WORD_LOG2));
-    LIns* oldval = lir->insLoad(LIR_ld, addr, 0);
-    LIns* isHole = lir->ins2(LIR_eq, oldval, lir->insImmPtr((void*)JSVAL_HOLE));
-    LIns* count = lir->insLoadi(obj_ins,
-                                offsetof(JSObject, fslots[JSSLOT_ARRAY_COUNT]));
-    lir->insStorei(lir->ins2(LIR_add, count, isHole), obj_ins,
-                   offsetof(JSObject, fslots[JSSLOT_ARRAY_COUNT]));
-
     /* ok, box the value we are storing, store it and we are done */
     LIns* v_ins = get(&v);
     LIns* boxed_ins = v_ins;
     if (!box_jsval(v, boxed_ins))
         return false;
-    lir->insStorei(boxed_ins, addr, 0);
+    LIns* args[] = { boxed_ins, idx_ins, obj_ins, cx_ins };
+    LIns* res_ins = lir->insCall(F_Array_dense_setelem, args);
+    guard(false, lir->ins_eq0(res_ins));
     set(&l, v_ins);
     return true;
 }
diff --git a/js/src/nanojit/vm_fops.h b/js/src/nanojit/vm_fops.h
index 738211f05efd..7bc47ac6793d 100644
--- a/js/src/nanojit/vm_fops.h
+++ b/js/src/nanojit/vm_fops.h
@@ -38,6 +38,7 @@
 #define BUILTIN1(op, at0,      atr, tr, t0, cse, fold)              F_##op,
 #define BUILTIN2(op, at0, at1, atr, tr, t0, t1, cse, fold)          F_##op,
 #define BUILTIN3(op, at0, at1, at2, atr, tr, t0, t1, t2, cse, fold) F_##op,
+#define BUILTIN4(op, at0, at1, at2, at3, atr, tr, t0, t1, t2, t3, cse, fold) F_##op,
 
 INTERP_FOPCODE_LIST_BEGIN
 #include "builtins.tbl"
@@ -46,3 +47,4 @@ INTERP_FOPCODE_LIST_END
 #undef BUILTIN1
 #undef BUILTIN2
 #undef BUILTIN3
+#undef BUILTIN4