Very modestly. It's better to provide simple 4 bit "hotness" probability similar to what CPUs do on their own in branch prediction and cache allocation. Consid

Very modestly. It's better to provide simple 4 bit "hotness" probability similar to what CPUs do on their own in branch prediction and cache allocation. Considering all the "blobby" multicore and SMT architecture, you could argue CPU has better information about registers. Just keep register format even and you'd be fine. Not too much to allocate when you have a lot of them and fast. The general hotness would especially help with reducing execution costs in JIT compilation, where new code is generated and CPU does not have accurate prediction data.