[llvm] [DataLayout] Introduce DataLayout::getPointerAddressSize(AS) (PR #139347)

[David Chisnall via llvm-commits]

davidchisnall wrote:

This looks like a good approach.  The function names convey intent, and will allow us to differentiate address and index size later if necessary.  The proposed use case for different addresses that I've seen was in the context of a RV128 ABI that would want a 64-bit `size_t` but a 128-bit `intptr_t` (single allocations can't be larger than 2^64 bytes, but can be anywhere in the address space).  

https://github.com/llvm/llvm-project/pull/139347