[Bug libgcc/67624] arm/fp16.c __gnu_f2h_internal has wrong pattern for INF/NAN

[joseph at codesourcery dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67624

--- Comment #2 from joseph at codesourcery dot com <joseph at codesourcery dot com> ---
All NaNs should have the top mantissa bit set in the result of the 
conversion (i.e. the result of the conversion should always be a quiet 
NaN, not a signaling NaN) - setting that bit also ensures the result is 
not an infinity.  Then I think the remaining bits in the mantissa of the 
result should match the corresponding high bits in the mantissa of the 
source (which appears to be what the hardware conversion instructions are 
documented to do).