32c6e16246
Add a new named module-level frontend-annotated metadata that specifies the TBAA node for an integer access, for which, C/C++ `errno` accesses are guaranteed to use (under strict aliasing). This should allow LLVM to prove the involved memory location/ accesses may not alias `errno`; thus, to perform optimizations around errno-writing libcalls (store-to-load forwarding amongst others). Previous discussion: https://discourse.llvm.org/t/rfc-modelling-errno-memory-effects/82972.