It seems like they were originally added in https://crrev.com/23654026
(Sep 2013) to break dependences in the OOO pipeline. This code pattern
was then later copied for other instructions too
(https://crrev.com/1424333002).
The reason for the xorpd is not mentioned in the code though, and I
found no other compiler doing this. So maybe it's obsolete by now, and
only increases code size.

Let's remove them and see if we get any performance regressions.

R=ahaas@chromium.org
CC=yangguo@chromium.org

Change-Id: I0e6d65afa67f0ee286e5b0ba95c91092c5261c8f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1926427Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65077}