Adapt Danno's Track Allocation Info idea to fast literals. When allocating a literal array,

test/mjsunit/array-natives-elements.js

 // 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 39 matching lines @@
 
   // Ensure small array literals start in specific element kind mode.
   assertTrue(%HasFastSmiElements([]));
   assertTrue(%HasFastSmiElements([1]));
   assertTrue(%HasFastSmiElements([1,2]));
   assertTrue(%HasFastDoubleElements([1.1]));
   assertTrue(%HasFastDoubleElements([1.1,2]));
 
   // Push
   var a0 = [1, 2, 3];
-  assertTrue(%HasFastSmiElements(a0));
-  a0.push(4);
-  assertTrue(%HasFastSmiElements(a0));
-  a0.push(1.3);
-  assertTrue(%HasFastDoubleElements(a0));
-  a0.push(1.5);
-  assertTrue(%HasFastDoubleElements(a0));
-  a0.push({});
-  assertTrue(%HasFastObjectElements(a0));
-  a0.push({});
-  assertTrue(%HasFastObjectElements(a0));
+  if (%HasFastSmiElements(a0)) {
+    assertTrue(%HasFastSmiElements(a0));
+    a0.push(4);
+    assertTrue(%HasFastSmiElements(a0));
+    a0.push(1.3);
+    assertTrue(%HasFastDoubleElements(a0));
+    a0.push(1.5);
+    assertTrue(%HasFastDoubleElements(a0));
+    a0.push({});
+    assertTrue(%HasFastObjectElements(a0));
+    a0.push({});
+    assertTrue(%HasFastObjectElements(a0));
+  } else {
+    assertTrue(%HasFastObjectElements(a0));
+    a0.push(4);
+    a0.push(1.3);
+    a0.push(1.5);
+    a0.push({});
+    a0.push({});
+    assertTrue(%HasFastObjectElements(a0));
+  }
   assertEquals([1,2,3,4,1.3,1.5,{},{}], a0);
 
   // Concat
   var a1;
   a1 = [1,2,3].concat([]);
   assertTrue(%HasFastSmiElements(a1));
   assertEquals([1,2,3], a1);
   a1 = [1,2,3].concat([4,5,6]);
   assertTrue(%HasFastSmiElements(a1));
   assertEquals([1,2,3,4,5,6], a1);
@@ skipping 217 matching lines @@
   assertEquals([1.1,{},2,3], a4);
 }
 
 if (support_smi_only_arrays) {
   for (var i = 0; i < 3; i++) {
     array_natives_test();
   }
   %OptimizeFunctionOnNextCall(array_natives_test);
   array_natives_test();
 }