After the runtime call for dynamic tiering, the instance cache is
invalidated. This was assumed to be done in {SpillAllRegisters}, but the
instance is still being accessed after that call, so the instance cache
register might still be set after the runtime call.

R=ahaas@chromium.org

Bug: chromium:1179065
Change-Id: I375e7c388e5a74789050e374db50d21c2efe27e2
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2714544Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72958}