[clang] [llvm] [AArch64] Add support for C1 CPUs (PR #171124)

[Peter Smith via llvm-commits]

smithp35 wrote:

We do have a convention for CPUs, agreed with the Arm GNU team as we want CPU features to be consistent as possible across toolchains, that for each Arm CPU we enable all optional features (like SME), with crypto being the exception of always being opt-in. This is partly historical as GCC has always modelled it that way and crypto extensions are subject to export control.

I understand that a lot of this will look inconsistent externally.

As statham-arm mentions we want to separate what features the CPU supports from whether it is the right thing to do to make use of them.

https://github.com/llvm/llvm-project/pull/171124