[account4mypc]

i tried to evaluate whether they would help build times at all. this is the only reason i want them. based on some research, they don't if you have parallel builds (since a module must be built before its users/not in parallel). so i think this lessened excitement from users/compiler devs/build tool makers. and it was enough to convince me to just buy more cores to parallelize builds more rather than put in work for half baked modules

[veselin]

There are already precompiled headers. They are a big speedup as far as I know, but semantically problematic. Maybe if you use them, you will not see a speedup.