It was assuming that the input is always a register, but it isn't.

Bug: chromium:1078399
Change-Id: If14abb8ea34f9febfc04a67a8da260a7e66af7f1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2182176Reviewed-by: Deepti Gandluri <gdeepti@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67578}