Huge increase in UT compile time

[Saurabh Das]

On Wednesday, 11 October 2017 at 08:11:37 UTC, Jonathan M Davis 
wrote:
> On Wednesday, October 11, 2017 06:25:19 Dhananjay via 
> Digitalmars-d-learn wrote:
>> Hello,
>>
>> I am upgrading to DMD 2.076.1 from DMD 2.069.2 (similar 
>> results on 2.075.1), and seeing a huge increase in unittest 
>> compilation time when the -deps parameter is also passed to 
>> dmd. This is on both OSX and linux. What can be the cause of 
>> this?
>
> Well, that's a pretty big version jump. So, a lot could have 
> changed. One thing that comes to mind would be that imports 
> were overhauled pretty thoroughly to try and fix various import 
> bugs. This blog article talks about some of that:
>
> http://www.schveiguy.com/blog/2016/03/import-changes-in-d-2-071/
>
> Or the change could be the result of something else entirely. 
> Figuring it out would likely require doing a fair bit of 
> debugging to narrow down when the change happened (and that's 
> assuming that it's caused by a single commit or small set of 
> commits rather than simply getting worse over time due to a 
> variety of factors).
>
> - Jonathan M Davis

The following observations (for the above test program) were 
recorded on Mac OS X 10.11.6:

DMD64 D Compiler v2.073.1
real    0m0.091s
user    0m0.067s
sys 0m0.020s

DMD64 D Compiler v2.074.0
real    0m0.105s
user    0m0.072s
sys 0m0.022s

DMD64 D Compiler v2.075.1
real    0m44.932s
user    0m35.732s
sys 0m7.098s

DMD64 D Compiler v2.076.1
real    0m46.833s
user    0m37.827s
sys 0m7.254s

Furthermore, 2.075.1 gave a bunch of deprecation warnings in 
std/string.d. The -de switch had to be removed before running.

Hope this helps,
Saurabh