As we're going to replace this ambiguous option with more precise
instruction-level fast-math description, some tests need to be updated
and the option doesn't play any role in some of them.
Exploit native VSX rounding instruction, x(v|s)r(d|s)pic, which does
rounding using current rounding mode.
According to C standard library, rint may raise INEXACT exception while
nearbyint won't.
Reviewed By: lkail
Differential Revision: https://reviews.llvm.org/D72685