[clang] [llvm] [IR][clang][CodeGen] Introduce `!llvm.errno.tbaa` for errno alias disambiguation (PR #125258)

[Antonio Frighetto via llvm-commits]

antoniofrighetto wrote:

> It would probably be best to split up the LLVM and the Clang changes.

Thank you, moved AA changes separately, addressed reviews. Updated this PR as well, pending an update on tests due to https://github.com/llvm/llvm-project/pull/147670.

> (I do wonder whether we should instead be making this a module flag with AppendUnique behavior. I'm not sure clear on what the tradeoff is between a module flag and separate named metadata.)

Looks like IRLinker::linkNamedMDNodes already disallows duplicated nodes, both are map lookups, thus took the choice of favouring a named metadata here (IR less verbose, getModuleFlag() would come with further checks in TBAA::aliasErrno; if I haven't missed anything).

https://github.com/llvm/llvm-project/pull/125258