[llvm] [AArch64][SelectionDAG] Add CodeGen support for scalar FEAT_CPA (PR #105669)

[Alexander Richardson via llvm-commits]

arichardson wrote:

It should be possible to drop the inverted flag once https://github.com/llvm/llvm-project/pull/125279 lands.

One more nit: maybe the commit message should link to https://developer.arm.com/documentation/ddi0602/2024-12/Base-Instructions/ADDPT--Add-checked-pointer- instead of the top-level instruction reference?

https://github.com/llvm/llvm-project/pull/105669