For PPC/s390 the case is missing where reference=attachedreference
how_to_code=kFromCode and  where_to_point=kStartOfObject. On PPC/s390
IsCodedSpecially always return true, hence how_to_code will not be a
straight pointer.
This should also fix the similar issue on mipsel.
The testcase was added as part of https://codereview.chromium.org/2205973003/

R=mtrofin@chromium.org, yangguo@chromium.org, titzer@chromium.org

BUG=
LOG=N

Review-Url: https://codereview.chromium.org/2247093002
Cr-Commit-Position: refs/heads/master@{#38789}