Details:
- Added a num_t datatype bitfield to the obj_t in the form of a new
info2 field in the obj_t. This change was made primarily so that in
the case of mixed-datatype gemm, the alpha scalar would not need to
be cast to the storage datatype of B (or A) before then being cast to
the computation datatype just before the macrokernel is called. This
double-casting regime could result in loss of precision if the storage
datatype of B (or A) is less than the computation precision. In
practice, it was likely not going to be a big deal since most usage of
alpha is for -1.0, 0.0, and 1.0 (or integer multiples thereof), which
can all be represented exactly in single or double precision.
- The type of objbits_t was changed to uint32_t, so the new format
potentially takes up the same space as the previous obj_t definition,
assuming no padding inserted by the compiler. Shrinking info to 32
bits and spilling over into a second field was chosen over using the
high 32 bits of a single 64-bit objbits_t info field because many of
the bitwise operations are performed with enums such as num_t, dom_t,
and prec_t, which may take on the type of 32-bit ints. It's easier to
just keep all of those bitwise operations in 32 bits than perform a
million typecasts throughout bli_type_defs.h and bli_obj_macro_defs.h
to ensure that the integers are treated as 64-bit for the purposes of
the ANDs, ORs, and bitshifts.
- Many comment updates.
- Thanks to Devin Matthews and Devangi Parikh for their feedback and
involvement during this commit cycle.
1d8aae220b