wg.Done()
			return nil
		})

		// Start the queue at the halfway point.
		if i == numValues/2 {
			go q.Run(stop)
		}
	}

	// wait for all task processed
	wg.Wait()

	if len(out) != numValues {
		t.Fatalf("expected output array length %d to equal %d", len(out), numValues)
	}

	for i := 0; i < numValues; i++ {
		if i != out[i] {
			t.Fatalf("expected out[%d] %v to equal %v", i, out[i], i)
		}
	}
}

// when they are done with the return values.
func liveValues(f *Func, reachable []bool) (live []bool, liveOrderStmts []*Value) {
	live = f.Cache.allocBoolSlice(f.NumValues())
	liveOrderStmts = f.Cache.allocValueSlice(f.NumValues())[:0]

	// After regalloc, consider all values to be live.
	// See the comment at the top of regalloc.go and in deadcode for details.
	if f.RegAlloc != nil {
		for i := range live {