diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/pic/shape_regen.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/pic/shape_regen.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,33 @@
+// Try to test that we handle shape regeneration correctly.
+// This is a fragile test, but as of this writing, on dmandelin's
+// windows box, we have the same shape number with different
+// logical shapes in the two assertEq lines.
+
+var o;
+var p;
+var zz;
+var o2;
+
+function f(x) {
+  return x.a;
+}
+
+gczeal(1);
+gc();
+
+zz = { q: 11 };
+o = { a: 77, b: 88 };
+o2 = { c: 11 };
+p = { b: 99, a: 11 };
+
+//print('s ' + shapeOf(zz) + ' ' + shapeOf(o) + ' ' + shapeOf(o2) + ' ' + shapeOf(p));
+
+assertEq(f(o), 77);
+
+o = undefined;
+
+gczeal(1);
+gc();
+//print('s ' + 'x' + ' ' + shapeOf(p));
+
+assertEq(f(p), 11);