fmin, fmax and their f and l forms tested their operands with std::isnan,
which GCC compiles to a compare that raises FE_INVALID for a signalling
NaN. FreeBSD's s_fmax.c and s_fmin.c read the exponent and significand
bits instead, "to avoid raising spurious exceptions", and return the
other operand. The NaN test now reads the bits of float, double and the
80-bit long double.
GuestFminf checks that a signalling NaN on either side returns the other
operand and leaves FE_INVALID clear, for all three types.
The failure was first caught by the numeric helper test of
boykopovar/AnyPS5#2280 (Привалов Александр Владимирович).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
