This makes the moves from constants to the poisoning register
explicit so that the register allocator does not have to burn
a register on it.

Bug: chromium:798964, chromium:820726, v8:7503, v8:7518
Change-Id: Ifc8f9a2f685405dd38fec583bb0e20c3f0320903
Reviewed-on: https://chromium-review.googlesource.com/964202Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51963}