[Bug middle-end/107702] {,unsigned} __int128 to _Float16 conversion shouldn't use libgcc routines

[joseph at codesourcery dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107702

--- Comment #2 from joseph at codesourcery dot com <joseph at codesourcery dot com> ---
(Where "check for any high bits being set" needs appropriate adjustment in 
the case of negative values for conversion from signed __int128, e.g. "the 
high 64 bits aren't the sign-extension of the low 64 bits" would be an 
appropriate condition to know there must be an overflow.)