diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/basic/truncateDouble.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/basic/truncateDouble.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,10 @@
+
+// check correctness of truncation of doubles slightly outside the int32_t range.
+
+function truncate(x) {
+  return x | 0;
+}
+
+assertEq(truncate(0xffffffff), -1);
+assertEq(truncate(0xffffffff + 5000.5), 4999);
+assertEq(truncate(-0xffffffff - 5000.5), -4999);