Performance impact of packing on alignment and padding

Ascertain the performance impact of packing struct members into bitfields, which alters native alignment and padding and introduces implicit bit-shift and masking operations on access.

Background

The proposed C++ annotations pack booleans, enums, and bounded-range integers into a shared bitfield to reduce memory footprint and potentially improve cache utilization.

While packing can decrease bandwidth usage, it also removes native alignment and requires conversion operations on every access. The authors explicitly note that the net performance effect is not known a priori.