diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/ion/bug848319.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/ion/bug848319.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,25 @@
+function test() {
+  for(var i=0; i<2; i++) {
+    var a = /a/;
+    assertEq(a.lastIndex, 0);
+    a.exec("aaa");
+    assertEq(a.lastIndex, 0);
+  }
+
+  for(var i=0; i<2; i++) {
+    var a = /a/g;
+    assertEq(a.lastIndex, 0);
+    a.exec("aaa");
+    assertEq(a.lastIndex, 1);
+  }
+
+  for(var i=0; i<2; i++) {
+    var a = /a/y;
+    assertEq(a.lastIndex, 0);
+    a.exec("aaa");
+    assertEq(a.lastIndex, 1);
+  }
+}
+
+test();
+test();