help with improving compile times

[Mason]

On 15/05/2017 14:01, Markus Trippelsdorf wrote:

> On 2017.05.15 at 12:11 +0200, Matthias Kretz wrote:
>
>> I'm looking for help on improving the compile times of my unit tests. Compile 
>> times of >60s per TU is making my life hard.
>> Alternatively, if you can tell me there's nothing I can do, then I can accept 
>> my fate and stop worrying about compile time optimizations.
>>
>> Picking one example from my ~500 unit test TUs:
>> You can see the source at https://github.com/VcDevel/Vc/blob/
>> c807aa0c841950e50ec7d370c9c22d6038c7e068/tests/loadstore.cpp
>>
>> Note that TEST_TYPES (line 109) produces 91 instantiations of the 
>> `load_store<VU>` function template from an outer product of two type lists. 
>> (I'd actually like to make the type list larger by a factor of 13, but that 
>> just blows the compiler up.)
>>
>> Attached is the output of -ftime-report. I must say I was surprised to see 
>> "phase opt and generate" with 62.5s and 95% of the total time, as well as 84% 
>> of the memory usage. Though, OTOH, the resulting binary is 4.4MiB large with 
>> about 3/4 of it being the .text section.
>>
>> If you have any ideas what I could do (other than "test less"), I'd like to 
>> try it.
> 
> Enabling Link Time Optimization may help: -flto=<some number, e.g. the
> number of cores you have>

I'm confused. Are you suggesting that requesting /more/ optimizations
might reduce compile+link time?

Regards.