We don't have memory alignment yet, so using memory operands will cause
segv if we try to access the unaligned operands (on non-AVX systems).

The fix here is kept simple (the logic can be cleaned up a bit and
optimized to not use unique registers), in order to keep the cherry-pick
and back-merge as small and safe as possible.

Bug: chromium:1204071
Change-Id: Ieda23dcc097a06c6db20b952d7061708c3be0d24
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2869986Reviewed-by: Bill Budge <bbudge@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74363}