x86 unsupported formats

[Peter Farkas]

   The extended format on x86 permits bit patterns that do not fall in
the "standard" categories (normal, denormal, pseudodenormal, infinity,
NaN).  These are patterns with non-zero biased exponent and zero
leading bit of the significand.  According to the Intel486 Programmers
Reference Manual they are not supported.  The Intel486 processor raises
the invalid-operation exception when they are encountered as operands.
   I am seeking opinions on the following statement: in the spirit of
IEEE 754, software should treat these bit patterns as if they were
NaN.
   Specifically, 1) math functions (e.g. expl(x), long double
exponential of long double x) should return NaN when x is represented
by such a bit pattern  2) isnanl(x) (which is meant to return 1 if x is
NaN and zero otherwise) should return 1 when x is represented by such a
bit pattern.
                                               Peter Farkas
                                               SunPro