Unlike BitSel, which enforces a strict one-hot mask encoding, this type permits any number of bits to be set or cleared. This is used to accumulate selections for batched operations on a register in real memory.
R: The register element that this mask governs.This must only be constructed by combining BitSel selection masks produced through the accepted chains of custody beginning with BitIdx values. Bit-masks not constructed in this manner are not guaranteed to be correct in the caller’s context and may lead to incorrect memory behaviors.