Two ideas for faster builds

[Jonathan M Davis via Digitalmars-d]

On Thursday, 11 June 2015 at 07:49:35 UTC, Dmitry Olshansky wrote:
> On 11-Jun-2015 03:50, Andrei Alexandrescu wrote:
>> https://issues.dlang.org/show_bug.cgi?id=14679
>> https://issues.dlang.org/show_bug.cgi?id=14680
>>
>> Andrei
>
> Not processing templates is cool idea.
> However the main problem with DMD's build times on moderately 
> sized projects is a huge memory leak in the compiler, mostly 
> having to do with CTFE.

Yeah. Pretty much any and all performance improvements that we 
can make should be made, and I don't think that they should be 
discouraged unless there's actually something wrong with them. 
But CTFE is the real killer. Improving that would probably 
improve build times by at least an order of magnitude for 
CTFE-heavy builds. Unfortunately, Don hasn't had time to work on 
CTFE for the last year+, and while Daniel has some definite ideas 
of how to improve it, he doesn't want to do that until we're 
fully switched over to D for the compiler, since it'll be easier 
to implement the changes there. So, we're unlikely to see any 
improvements there until we've fully switched to ddmd unless 
another compiler dev decides to take the plunge. At least we're 
getting close to ddmd though.

The other fun one is the insane number of template instantations 
we get for stuff like std.algorithm thanks to all of those helper 
templates like isInputRange. IIRC, std.algorithm's unit tests 
instantiate over a million different template instances - and 
much of that is simply for template constraints and static ifs. 
So, improving build times with regards to templates which are 
instantiated would probably be the second largest gain to be had 
behind CTFE if we could improve it, but obviously, we'd have to 
make such improvements to be sure.

Regardless, the more that we can reasonably do to improve build 
times, the better. And while we want to fix the big problems, 
every little bit helps.

- Jonathan M Davis