[Bug tree-optimization/57994] Constant folding of infinity

[vincent-gcc at vinc17 dot net]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57994
--- Comment #13 from Vincent Lefèvre <vincent-gcc at vinc17 dot net> ---
A difference that may occur in the future if the C library adds a rsqrt
function (based on the IEEE 754-2008 rSqrt function) or constant folding is
used on builtins: in MPFR, mpfr_rec_sqrt on -0 gives +Inf, not -Inf.