What happened to phobos compile time?

[Andrei Alexandrescu]

On 8/4/20 12:41 AM, Mathias LANG wrote:
> On Tuesday, 4 August 2020 at 03:54:53 UTC, RazvanN wrote:
>> Hello everyone!
>>
>> I just tried compiling phobos on machine to get updated with the 
>> latest changes and I noticed an explosion in compile time. On my 
>> machine it takes roughly 5 minutes (!!!) to compile it while last year 
>> it took somewhere around 15-30 seconds. Does anyone know what has 
>> caused this serious performance regression?
>>
>> Thanks for answers,
>> RazvanN
> 
> Welcome to the wonderful world of DMD inliner, we hope you enjoy your stay.
> 
> ```
> $ make -f posix.mak -j8  88.90s user 0.89s system 99% cpu 1:30.25 total
> $ git show HEAD | head -n 5
> commit 2f0ea3fdedc2889b63f266de908cb8658ce98ec9
> Author: Walter Bright <walter at walterbright.com>
> Date:   Tue Jul 21 01:12:35 2020 -0700
> 
>      sha: inline critical functions
> $ git checkout HEAD^
> Previous HEAD position was 2f0ea3fde sha: inline critical functions
> HEAD is now at e364edfc8 Merge pull request #7561 from 
> WalterBright/fabs-float
> $ make -f posix.mak -j8  9.42s user 0.55s system 98% cpu 10.128 total
> ```

That's a large penalty. I hope at least the debug build hasn't been 
affected.

I recall the change was made to get performance parity with gdc and ldc 
for the sha code. So I wonder (a) how the resulting performance of the 
sha functions compares with those, and (b) how long it takes to build 
phobos with gdc and ldc.