This is a patch teaching ValueTracking that `s/u*.with.overflow` intrinsics do not
create undef/poison and they propagate poison.
I couldn't write a nice example like the one with ctpop; ValueTrackingTest.cpp were simply updated
to check these instead.
This patch helps reducing regression while fixing https://llvm.org/pr49688 .
Reviewed By: nikic
Differential Revision: https://reviews.llvm.org/D99671