This change helps mostly to reduce register pressure. By default, we
compile LoadStackPointer into a move from the stack register into some
general purpose register and then later use that register. This might
trigger a spill to free up space, which is particularly costly in
loops.

Change-Id: I886233f890b7833f873fc24773f621add7cf0588
Reviewed-on: https://chromium-review.googlesource.com/1104351
Commit-Queue: Stephan Herhut <herhut@chromium.org>
Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54126}