The LoadElimination (and potentially earlier passes too) might have
removed or lowered side-effecting operations, which allows for further
combining of check points in the graph, removing unnecessary StateValue
uses for the later truncation analysis.

BUG=chromium:709398
R=jarin@chromium.org

Review-Url: https://codereview.chromium.org/2807563002
Cr-Commit-Position: refs/heads/master@{#44486}