Generates
bit masks for elements in the return vector. For each doubleword element
in d, a bit mask is generated. The mask consists
of bits set to one starting at the bit position specified by a and
ending with the bit position specified by b. All
other bit positions are set to zero.
Notes:
If a or b is greater than 64,
the operation is performed as if the value gets modulo by 64.
If a is greater than b, the
operation is perform as if b equals 63.