This assumes that Phi nodes never point to untagged values and
TemporaryRegisters are always general registers.

Bug: v8:7700
Change-Id: I74a6c43ff9f1ba87dd258e90a193f683d666b8ec
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3598883Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Victor Gomes <victorgomes@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80144}