vcperf miss some templates

[qnope]

Hello

I am trying to optimize the compile time of a home made library.
Until now, I was using clang -ftime-trace option that gives us a nice json to read, with the time of each template instantiation.

I saw that we can do the same with vcperf. However, when we compile simple code, vc perf does not output anything useful.... We get the time to parse includes, but nothing relevant about template instantiation.
However, on "heavy" templates, we do obtain information on the heavy one, and sometimes about the little also. (It is funny because vcperf does not catch them when there is only small ones)

Here a code sample :

template <int... is> struct seq {};

template <int Size, int... Is>
struct make_seqImpl : make_seqImpl<Size - 1, Size - 1, Is...> {};

template <int... Is> struct make_seqImpl<0, Is...> { using type = seq<Is...>; };

template <int generate> using make_seq = typename make_seqImpl<generate>::type;

int main() {
  constexpr auto seq = make_seq<5>{};
  return 0;
}

Here the command lines

vcperf.exe /start /level3 a
compilation from QtCreator or visual studio using MSVC
vcperf.exe /stop /templates a output.etl

What can I do?

Thanks :)

[kevcadieux]

Hi qnope,

For scalability reasons, vcperf discards templates that don't have a significant impact on build time. If you still wish to see them, you can either:

1. Modify vcperf to keep all instantiations (see ExpensiveTemplateInstantiationCache::DetermineTopPrimaryTemplates)
2. Write your own analyzer using the C++ Build Insights SDK, where you'll have full control (example here).

Please be aware that option 1 will result in very large traces for long builds.

I hope this helps,

Kevin

[qnope]

Thanks for your answer :-)

Do you want me to do a Pull Request to add a "--full" option ?

Sorry for the late answer :-)