<blockquote>
<p>I can see -flto=auto being useful for the average upstream makefile defaults but I'm not convinced this is the right thing to do in rpm context: we'd want our parallel activities controlled via the same central tunables ($RPM_BUILD_NCPUS / %{_smp_ncpus_max}).</p>
</blockquote>
<p>Which is way you want to controll a build system (make). Note that <code>-flto=N</code> is used for parallel linking phase and with the new option <code>-flto=auto</code> we can respect make's jobserver parallelism level<br>
and communication with it. And as a fallback we want to make linking as parallel as possible. That's what we do in openSUSE right now.</p>
<blockquote>
<p>If LTO falls back to detecting number of cores on its own, that goal was missed.</p>
<p>Is there a summary of the gcc community reasoning someplace or can you provide one?</p>
</blockquote>
<p>The main problem is that we see a lot of differences due to package builds with different <code>-flto=N</code> values. That's because some packages embed options (for <code>--help</code>) option. And mainly we want to have a bitwise identical <code>rpm</code> for reproducible builds. That's why we want to leave <code>-flto=N</code> option.</p>

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