> On Sep 26, 2018, at 12:16 PM, Jan Hubicka <hubi...@ucw.cz > <mailto:hubi...@ucw.cz>> wrote: > >>> >>> On Sep 26, 2018, at 10:06 AM, Jan Hubicka <hubi...@ucw.cz >>> <mailto:hubi...@ucw.cz>> wrote: >>> >>>> On Wed, Sep 26, 2018 at 10:45 AM, Jeff Law <l...@redhat.com >>>> <mailto: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 >>>>>> <mailto: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.
Okay, I see. > > 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. do you suggest that to set the global function as AVAIL_INTERPOSABLE when -finline-only-static is present? then we should avoid all issues? Qing > 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
