On 11/26/20 12:57 AM, Joseph Myers wrote:
I think it would be a pain to maintain test coverage for unnormals (and
presumably all the other kinds of unsupported operands, and you'd need to
work out what semantics you want for pseudo-denormals as well since those
are the one kind of such representation the processor doesn't raise
"invalid" for) for all the functions with floating-point arguments - and
claiming to handle those consistently requires having such test coverage
(there are only a few tests for such format-specific representations in
sysdeps/ieee754/ldbl-96 at present).
pseudo-denormals are still considered valid, so I'm admittedly punting
them for later since the processor manual still claims to handle them
correctly.
But maybe you could set up some mechanism by which, when gen-libm-test.py
processes a test using snan_value or snan_value_ld (but not
snan_value_pl), and the relevant format is one of the format variants that
has these representations, it automatically generates tests for all those
variants (that the processor raises "invalid" for when handling as
operands, i.e. treats much like sNaN). I'm not sure if it's actually
possible to generate a static initializer for a long double value with one
of those representations, or only for a union containing a long double
where another member is initialized; if a union type needs to be used in
the tables of test inputs, that further complicates things.
It would have to either be a union type with various bit patterns or a
bit string copied into a long double; the CPU will never generate any of
the pseudo numbers on its own.
Siddhesh
