Who can make Phobos faster to import?

[RazvanN]

On Thursday, 21 December 2017 at 03:31:16 UTC, Joakim wrote:
> On Wednesday, 20 December 2017 at 18:21:33 UTC, Andrei 
> Alexandrescu wrote:
>> On 12/15/2017 02:10 PM, Seb wrote:
>>> [...]
>>
>> Dmitry wrote a nice PR for that, and I wrote two:
>>
>> https://github.com/dlang/phobos/pull/5942
>> https://github.com/dlang/phobos/pull/5931
>> https://github.com/dlang/phobos/pull/5948
>>
>> My approach has been the following:
>>
>> * First I tried to clarify which module imports what by means 
>> of replacing "import std.xxx;" with "import std.xxx : yyy, 
>> zzz, ...;" That has been of tremendous help in assessing each 
>> module's dependency liability.
>>
>> * Then I tried to figure which imports are most costly. I 
>> inserted __EOF__ in the module at different parts and measure 
>> how long it takes to just import that module. After a few 
>> attempts it becomes clear which imports are heaviest.
>>
>> * Then I pushed those heavy imports down where they're needed. 
>> An import placed in a function will not be opened while that 
>> function's module gets imported. Same goes about template 
>> types, but not structs or classes. (That should be fixed; see 
>> Seb's comment in my last PR.)
>>
>> Not only such work reduces import times, but it's illuminating 
>> for maintenance because it represents dependencies in a 
>> simple, fine-grained matter.
>>
>> A tool (call it depend - heh) to automate that would be 
>> awesome. For example, this run would make all imported names 
>> explicit:
>>
>> depend --explicit *.d
>>
>> This run would push all imports down to the innermost scope of 
>> usage:
>>
>> depend --pushdown *.d
>>
>>
>> Andrei
>
> I'm on it.  I tried using a version of Seb's frontend library 
> yesterday but with the standard dmd main and tried running it 
> on std.stdio, but it asserted in asmSemantic because of an asm 
> block somewhere in druntime, so I'm back to using a tweaked 
> full dmd with the backend simply disabled again:

I ran into the same issue. The problem was that currently the 
frontend
doesn't set the version identifiers. There's a PR which tries to 
fix it [1],
but if you want to go back at using the compiler library via 
Seb's interface
you just have to call this method [2] in the initialization step.

Anyway I am working on this sort of tool also, so maybe we can 
unite our efforts.
Ping me if you wish so,

[1] https://github.com/dlang/dmd/pull/7524
[2] https://github.com/dlang/dmd/blob/master/src/dmd/mars.d#L1314
>
> https://github.com/dlang/dmd/pull/7425
> https://github.com/dlang/dmd/blob/master/src/dmd/gluelayer.d#L47
> https://gist.github.com/joakim-noah/09cf49bee3d82b03a54f
>
> Once I have something basic working, I'll put it up on github, 
> so others who are interested can play with it and pitch in to 
> make it a real tool.

Best regards,
RazvanN