MaskRay added a comment. Sorry, I still don't understand this response:
> We have 3 sets weak symbols here: weak_func, profc_weak_foo, profd_weak_func. > We can't ensure that binder always choose 3 of them from same object. So this part of the description isn't clear to me: > However, on AIX, the current binder can NOT discard the weak symbols if we > put all of them into the same csect, as binder can NOT discard only part of a > csect. > > This creates a unique challenge for using those symbols to calculate some > relative offset. Say a.o has a weak `foo, __profc_foo, __profd_foo`. The `__profd_foo` references the `__profc_foo` b.o has another set of weak `foo, __profc_foo, __profd_foo`. The `__profd_foo` references the `__profc_foo`. What's the linker (called binder?) behavior? "We can't ensure that binder always choose 3 of them from same object."? But is that a problem? For linkonce_odr functions, they should have identical semantics in a.o and b.o. (There can be ODR issues if you use advanced PGO techniques like value profiling, but I assume that it does not work and will be difficult to make work and more importantly, it is also of lower value anyway.) So the linker picking the a.o `foo` and the b.o `__profc_foo/__profd_foo` isn't a poblem. I understand that PrivateLinkage can avoid the issues but you need to justify the complexity in `InstrProfiling.cpp` with the value. Currently I don't think using weak symbol is a big problem, especially if the AIX linker will be fixed anyway in the future. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D110422/new/ https://reviews.llvm.org/D110422 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
