Operands in Arm can be encoded as (8-bit value, 2*N bit left rotate).
This encoding is checked for with the FitsShifter function.

Previously, this encoding was exhaustively searched for by checking all
16 possible rotations. However, we can simply classify the different
possible rotations as shifting away trailing zeros (without rotation),
or rotating an 8-bit value split over the beginning and end of the
32-bit value (which, after one rotation, becomes the first case).

Hence, we can replace the exhaustive search with a couple of trailing
zeros calculations within these classes.

Change-Id: Id896539c376f695b54bdf31133b2a103b0cf9736
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2831479
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Patrick Thier <pthier@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74012}