On Fri, Sep 04, 2026 at 04:05:01PM +0200, Florian Weimer via devel wrote:
> * Benjamin Beasley:
>
> > On the other hand, if this change is less about packages that
> > currently can’t use LTO and more about trying to save build time for
> > packages that already successfully build with fat LTO objects, then
> > how much builder time can be saved? And what, if any, effect on the
> > performance of the compiled programs can be expected? If this is a
> > compile-time/runtime performance tradeoff, it’s hard to make an
> > informed decision without knowing what is being traded for what.
>
> Assuming this is about not using -ffat-lto-objects with GCC, there
> should not be a change in generated machine code as a result of this.
> It just drops non-LTO code generation that we currently discard anyway.
We don't discard it in all cases though.
It is ignored when linking binaries/shared libraries with -flto and where
the LTO sections are present too.
We strip the LTO sections in *.a libraries included in packages (or in the
rare case where packages include *.o objects), and in that case without
-ffat-lto-objects it wouldn't work at all.
So, sure, we could drop -ffat-lto-objects for packages which don't include
in %files any *.a/*.o files (most of them), but packages which include those
(even when just in some binary subpackages) wouldn't work without it (or one
would need to judge what should be compiled with that flag and what can
avoid it depending on in what it will be linked or archived).
Jakub
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