> On 4/22/20 8:11 PM, Jan Hubicka wrote:
> > > On Mon, 2020-04-20 at 11:34 +0200, Martin Liška wrote:
> > > > Hi.
> > > >
> > > > The patch prevents a ifunc alias from removal in remove unreachable
> > > > nodes.
> > > > Note that ifunc alias lives in a COMDAT section and so that
> > > > cgraph_node::can_remove_if_no_direct_calls_and_refs_p returned true for
> > > > it.
> > > >
> > > > Patch can bootstrap on x86_64-linux-gnu and survives regression tests.
> > > > I was unable to create a lto test-case where a linked binary could be
> > > > scanned for assembly.
> > > >
> > > > Ready to be installed?
> > > > Thanks,
> > > > Martin
> > > >
> > > > gcc/ChangeLog:
> > > >
> > > > 2020-04-20 Martin Liska <mli...@suse.cz>
> > > >
> > > > PR lto/94659
> > > > * cgraph.h
> > > > (cgraph_node::can_remove_if_no_direct_calls_and_refs_p):
> > > > Do not remove ifunc_resolvers in remove unreachable nodes in
> > > > LTO.
> > > OK
> > Is it intended to keep the comdat group alive even when the function is
> > not used by the current translation unit?
>
> Yes, if you take a look at the mentioned PR, the function is exported and used
> by a different TU.
>
> Or do you have a particular test-case which you're talking about?
Well, first I think you want to use force_output flag when you create
the alias instead of modifying can_remove_if_no_direct_calls_and_refs_p.
I wonder what happens when your function is static and we optimize away
all uses of it - then I think GCC should optimize it away.
Similarly if the function is comdat:
__attribute__((target_clones("default,avx")))
inline
int f1()
{
return 2;
}
int
main()
{
return f1();
}
We should avoid outputting it to every compilation unit that includes
the header.
I do not recall, why that function is comdat at first place?
Honza
