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

[joseph at codesourcery dot com]

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

--- Comment #2 from joseph at codesourcery dot com <joseph at codesourcery dot com> ---
If you use -fexcess-precision=standard, the classification built-in 
functions should convert values with excess range and precision to their 
semantic types as required by ISO C (see c-typeck.c:convert_arguments).  
Without -fexcess-precision=standard, the front end can't do that because 
the excess range and precision is all hidden by the back end.