Subzero: Make liveness validation errors easier to interpret.

Subzero: Make liveness validation errors easier to interpret.

A portion of the translation workflow goes like this:

  dump #1
  renumber instructions
  liveness + live range construction
  validateLiveness (exit on failure)
  dump #2

If there are liveness validation errors, instruction numbers are reported with respect to the new instruction numbers, yet the most recent dump output is with respect to the old instruction numbers.  Confusion ensues.

To fix this, we just do dump #2 before validateLiveness.

BUG= none
R=jpp@chromium.org

Review URL: https://codereview.chromium.org/2080633004 .