Just an idea: we could get rid of compact classes, which would give us additional 6 bits (5 bits from the compact class index plus 1 bit from the header type because there would only be 2 header types left). This would increase the identity hash values from 4096 to 262144. In a PharoCore1.0 image there are 148589 instances of compact classes, hence this would cost 580k. Or, we could just add an additional word and use the spare bits from the old identity hash for other stuff, e.g., immutability ;)
I like the first idea, we could even have the 17 continuous bits for identity hash the 1 separate bit for immutability.
Yes please, I love it :-)
Lukas