Purity, memoization and parallelization of dmd

[Paul Backus]

On Thursday, 16 July 2020 at 18:21:11 UTC, Per Nordlöw wrote:
> What's the status/progress on making dmd (completely) pure?
>
> Is this task on somebody's agenda? If so, are there any big 
> obstacles that currently has no clear solution or is just a 
> very large pile of small ones?
>
> And, in the long run, will a pure compiler (finally) enable 
> caching/memoization of, for instance, template 
> instantiations/ctfe-evaluations and, perhaps further into 
> future, parallelization of the compiler?

DMD uses mutable state for basically everything, so I don't think 
it is likely to ever be completely pure. I believe there is an 
ongoing effort to make individual functions pure when possible, 
though I'm not sure how much progress is being made.

Template instantiations are already cached (which actually causes 
buggy behavior, because they are not quite pure [1]).

[1] https://issues.dlang.org/show_bug.cgi?id=19458