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Re: help with improving compile times
- From: Markus Trippelsdorf <markus at trippelsdorf dot de>
- To: Matthias Kretz <m dot kretz at gsi dot de>
- Cc: gcc-help at gcc dot gnu dot org
- Date: Mon, 15 May 2017 14:01:26 +0200
- Subject: Re: help with improving compile times
- Authentication-results: sourceware.org; auth=none
- References: <7758193.5tzhTicriZ@mars>
On 2017.05.15 at 12:11 +0200, Matthias Kretz wrote:
> Hi,
>
> 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>
--
Markus