https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100152
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |vmakarov at gcc dot gnu.org
--- Comment #33 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Iain Sandoe from comment #32)
> (In reply to Iain Sandoe from comment #31)
> > (In reply to Richard Biener from comment #30)
> > > (In reply to Iain Sandoe from comment #29)
> > > > what is also somewhat peculiar is that replacing the first function in
> > > > the
> > > > reduced test case with "extern void ___UTF_8_put(char *a, int b);"
> > > > changes
> > > > the code-gen for the second function.
> > >
> > > That might hint at IPA RA which you can try disabling via -fno-ipa-ra
> > > which
> > > in turn hints at a target issue.
> >
> > yeah, it does switch back to using rbx, at least on the reduced test case.
>
> (also on the original).
>
> I wonder if the problem is that IPA can't "see" the lazy symbol resolver, so
> it just sees a call to ___UTF_8_put and doesn't know that this will be
> resolved indirectly.
>
> .. but something similar must apply to PLT and targets with linker veneers ?
I don't know how IPA RA works in detail but obviously the target has to
expose this detail. It looks like IPA RA causes us to add some notes to
call insns which are supposed to describe those details and there's
collect_fn_hard_reg_usage which looks at the target function (but likely
does not include the ABI details of the call itself, in this case the
resolver).
