[Bug c/79117] __builtin_isfinite edge case incorrect on i386

[jtaylor.debian at googlemail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79117

--- Comment #3 from Julian Taylor <jtaylor.debian at googlemail dot com> ---
using isinf is not correct as isinf(nan) == 0
why does isinf do the truncation on x87 and isfinite does not?