diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/basic/testInitSlowify.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/basic/testInitSlowify.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,41 @@
+
+var x = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,gc(),
+         1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,gc(),
+         1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,gc(),
+         1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,gc(),
+         1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,gc(),
+         1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,gc(),
+         1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,gc(),
+         1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,gc(),
+         1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,gc(),
+         1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,gc(),
+         1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,gc(),
+         1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,gc(),
+         1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,gc(),
+         1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,gc(),
+         1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,gc(),
+         1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,gc(),
+         1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,gc(),
+         1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,gc(),
+         1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,gc(),
+         1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,gc(),
+         1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,gc(),
+         1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,gc(),
+         1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,gc(),
+         1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,gc(),
+         1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,gc(),
+         ];
+assertEq(x.length, 500);
+assertEq(x[10], 11);
+assertEq(x[90], 11);
+
+function stringify(a) {
+  var b = "";
+  for (var c in a) { b += c + ","; }
+  return b;
+}
+
+var y = {a:1,b:2,c:3,d:4,e:gc(),f:6,g:7,h:8,i:9,j:gc(),
+         k:11,l:12,m:13,n:14,o:gc(),p:16,q:17,r:18,s:19,t:gc()};
+
+assertEq(stringify(y), "a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,");