What does `std::kill_dependency` do, and why would I want to use it?

Question

I\'ve been reading about the new C++11 memory model and I\'ve come upon the std::kill_dependency function (§29.3/14-15). I\'m struggling to understand why

Answer 1

My guess is that it enables this optimization.

r1 = x.load(memory_order_consume);
do_something_with(a[r1->index]);