[llvm] [BasicAA][TLI] Local-linkage or non-thread-local globals may not alias errno (PR #170290)

[Antonio Frighetto via llvm-commits]

antoniofrighetto wrote:

Updated by dropping IsErrnoThreadLocal.

> Unusual/baremetal environments usually end up using -ffreestanding for various reasons. So we don't really care what happens there, as long as we don't do errno checks with -ffreestanding. I'm not sure we actually suppress the checks currently, though.

I believe the only way to infer -ffreestanding is from the target triple. From https://clang.llvm.org/docs/CrossCompilation.html:

>  The system name is generally the OS (linux, darwin), but could be special like the bare-metal “none”.

Triple.cpp also considers none as environment to model freestanding:

https://github.com/llvm/llvm-project/blob/7ac29007187e43c2b5224a0334f82800f5109a34/llvm/lib/TargetParser/Triple.cpp#L1435-L1438

Not doing any assumptions on 1) unknown environments unless Darwin 2) "none" OS.

https://github.com/llvm/llvm-project/pull/170290