diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/parallel/Array-reducePar-bail.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/parallel/Array-reducePar-bail.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,32 @@
+load(libdir + "parallelarray-helpers.js");
+
+// Tests that reduce saves its intermediate state correctly by
+// inducing a bailout in the middle of the reduction.  This test may
+// fail to test what it is intended to test if the wrong number of
+// worker threads etc are present.  It reproduced an existing bug when
+// used with 8 worker threads.
+
+function testReduce() {
+  var aCounter = 0;
+  function sum(a, b) {
+    var r = a + b;
+    if (r == 234) // occurs once per slice
+      aCounter++;
+    return r;
+  }
+
+  // We use a big array, to make sure that the test runs with 64 slices.
+  var array = build(8 * 4096, function() { return 1; });
+  var seqResult = array.reduce(sum);
+  var seqCounter = aCounter;
+
+  aCounter = 0;
+  var parResult = array.reducePar(sum);
+  var parCounter = aCounter;
+
+  assertEq(true, parCounter >= seqCounter);
+  assertStructuralEq(parResult, seqResult);
+}
+
+if (getBuildConfiguration().parallelJS)
+  testReduce();