This patch introduces preliminary support for additional memory
locations.
They are: target_mem0 and target_mem1 and they model memory locations
that cannot be represented with existing memory locations.
It was a solution suggested in :
https://discourse.llvm.org/t/rfc-improving-fpmr-handling-for-fp8-intrinsics-in-llvm/86868/6
Currently, these locations are not yet target-specific. The goal is to
enable the compiler to express read/write effects on these resources.
Model C/C++ `errno` macro by adding a corresponding `errno`
memory location kind to the IR. Preliminary work to separate
`errno` writes from other memory accesses, to the benefit of
alias analyses and optimization correctness.
Previous discussion: https://discourse.llvm.org/t/rfc-modelling-errno-memory-effects/82972.
