- Dup (broadcast) shuffles are always swizzles (single operand),
  which are canonicalized to only use the first input, so we don't
  need to check the index and switch operands.

Bug: v8:6020
Change-Id: I3ef8ba8071775dfbd21c0cab3fdf24db17f496bb
Reviewed-on: https://chromium-review.googlesource.com/1129540Reviewed-by: Deepti Gandluri <gdeepti@chromium.org>
Commit-Queue: Bill Budge <bbudge@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54367}