> > > On Sep 26, 2018, at 10:06 AM, Jan Hubicka <hubi...@ucw.cz> wrote: > > > >> On Wed, Sep 26, 2018 at 10:45 AM, Jeff Law <l...@redhat.com> wrote: > >>> On 9/26/18 7:38 AM, Jason Merrill wrote: > >>>> On Wed, Sep 26, 2018 at 9:24 AM, Richard Biener <rguent...@suse.de> > >>>> wrote: > >>>>> IIRC he explicitely wanted 'static' not 'hidden' linkage. Not sure > >>>>> what 'internal' would mean in this context. > >>>> > >>>> I mean internal linkage as in the C and C++ standards. > >> > >>> Since this is primarily for kernel hot patching, I think we're looking > >>> to restrict inlining to functions that have visibility limited to a > >>> compilation unit. > >> > >> Right, which is internal linkage. > >> > >> C11: "Within one translation unit, each declaration of an identifier > >> with internal linkage denotes the same object or function." > >> C++17: "When a name has internal linkage, the entity it denotes can be > >> referred to by names from other scopes in the same translation unit." > >> > >> Or perhaps we want to say "not external linkage", i.e. !TREE_PUBLIC as > >> richi suggested. > > > > I am not quite sure if we can relate visibility flags we have at this stage > > to visibility in source languge in very coherent way. They change a lot > > with > > LTO and we may want to make this option incompatible with LTO, but even w/o > > we can turn function static that previously wasn’t. > > Looks like both LTO and whole_program need to be made incompatible with > -finline-only-static. > from my study of the function “cgraph_externally_visible_p”, comdat functions > can ONLY be turned into > static when either “in_lto_p” or “whole_program” is true.
This is not quite the case, because, we can still clone them to static functions or derive fact about their side effects (such that information if they write/read memory, particular global var etc). All this inter-procedural propagation is guarded by get_availability predicate returning at least AVAILABLE. If you make this to be INTERPOSABLE (which means it can be replaced by different implementation by linker and that is probably what we want for live patching) then also inliner, ipa-sra and other optimization will give up on these. Honza > > > > For example comdat that was cloned by IPA-SRA. See can_be_local_p and > > comdat_can_be_unshared_p predicates. Similar problem happens to clones > > created > > by ipa-cp. > > > > I guess we want to disable localization and cloning in this case as well. > > I wonder what else. > > Yes, I think we should make -finline-only-static incompatible with cloning > and tree-sra too. > > Qing > > > > Honza >
