3X speedup is a definite improvement. I don't use rust regularly, so have been relying on community news for updates and while they have mentioned planned work to increase compilation speed a few times they haven't really talked about any landing (that I saw anyways).
Also cold start speed is not really what I care about. I am more concerned with compiler speed while working and running tests. I find that if a language compiler is to slow it breaks flow while testing changes. I haven't seen much mention of the improvements the incremental compiler gives in a while. Last I read was the 2017 blog post [1] during beta and it only showed modest improvements and more recently I only see talk of how it still needs a lot of work [2].
Incremental compilation was a big improvement over the status quo.
I don't follow compiler performance developments. I'm just responding to clarify that there has been performance improvements. They have likely just built up over time. I don't think there was any one specific change that dramatically improved things.
Also cold start speed is not really what I care about. I am more concerned with compiler speed while working and running tests. I find that if a language compiler is to slow it breaks flow while testing changes. I haven't seen much mention of the improvements the incremental compiler gives in a while. Last I read was the 2017 blog post [1] during beta and it only showed modest improvements and more recently I only see talk of how it still needs a lot of work [2].
[1] https://internals.rust-lang.org/t/incremental-compilation-be...
[2] https://nicoburns.com/blog/rust-2019/#compile-times-especial...