It's sometimes useful to know whether a use of a stack variable (as opposed to a physical register) is the last use of that variable.  For example, in a code sequence like:
  movl %edx, 24(%esp)
  movl 24(%esp), %edx
it would be nice to know whether the code sequence is merely bad (i.e., 24(%esp) will be used later), or horrible (i.e., this ends 24(%esp)'s live range).

We add stack variables to the per-instruction live-range-end annotation, but not to the per-block live-in and live-out annotations, because the latter would clutter the output greatly while adding very little actionable information.

BUG= https://code.google.com/p/nativeclient/issues/detail?id=4135
R=jvoung@chromium.org

Review URL: https://codereview.chromium.org/1113133002