Survey memory usage of compiler symbols: how can it be reduced?

[gafter]

I noticed that source symbols have a side bag with a boolean for every possibly applicable well-known attribute. That is horribly space-inefficient. How much space do our symbols use? How can we reduce the space used? At the very least we should consider sharing the (same) empty bag among all symbols with no attributes.

[CyrusNajmabadi]

@jaredpar is it worth having these issues? Or should this just fall under a more holistic: "we should profile the CPU and memory used during compilation and invest in areas with large wins"?