[clang] [llvm] [AArch64] FEAT_SPEv1p2 is optional in v8.7-A and v9.2-A (PR #123336)

[Oliver Stannard via llvm-commits]

ostannard wrote:

This is a system register only feature, but not one which we have enabled unconditionally. If we're going to turn it on only for architectures/CPUs which (can) have it, then I think it's better to be precise, which is what this patch does. Since it's only a system register we could go the other way and turn it on unconditionally, but as you say the current bevahiour seems to be intentional.

https://github.com/llvm/llvm-project/pull/123336