As the comment already indicates, performing an operation with
nnan/ninf flags on a nan/inf or undef results in poison. Now that
we have a proper poison value, we no longer need to relax it to
undef.
This is part of the IR sibling for:
D75576
(I'm splitting part of the transform as a separate commit
to reduce risk. I don't know of any bugs that might be
exposed by this improved folding, but it's hard to see
those in advance...)
As it's causing some bot failures (and per request from kbarton).
This reverts commit r358543/ab70da07286e618016e78247e4a24fcb84077fda.
llvm-svn: 358546
Nikita Popov