Loop variable analysis doesn't recognize that the initial type of the
loop variable phi combined with the increment type may produce a NaN
result through the addition of two infinities of differing sign.

This leads to unreachable code and a SIGINT crash.

The fix is to consider this case before typing the loop variable phi,
falling back to more conservative typing if discovered.

R=neis@chromium.org

Bug: chromium:1028863
Change-Id: Ic4b5189c4c50c5bbe29e46050de630fd0673de9f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1946352
Commit-Queue: Michael Stanton <mvstanton@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65291}