rma = a * b
rma
may alias with a
or b
. a
and b
may alias with each other.
Asserts the result fits in rma
. An upper bound on the number of limbs needed by rma is given by a.limbs.len + b.limbs.len
.
limbs_buffer
is used for temporary storage. The amount required is given by calcMulLimbsBufferLen
.