[clang] [compiler-rt] [llvm] [AArch64] Split FeatureMTE to FEAT_MTE and FEAT_MTE2. (PR #109299)

[Alexandros Lamprineas via cfe-commits]

labrinea wrote:

> From the patch it is clear all CPUs that implement MTE only support MTE2 - and it seems unlikely this will change.

Not quite true. I didn't change those CPU entries to keep the behavior NFC, which may have been a mistake actually. The reference manual suggests that Neoverse N2, or Cortex-X2 for example only have FEAT_MTE (or at least there is no mention of FEAT_MTE2 in the documents).

> Note the extra MTE2 instructions are only available in EL1 IIRC. So there is no use for differentiating between them for the purpose of FMV (which targets EL0). 
 
This is actually a convincing argument.
 
> Also adding new +mte/+mte2 options on the commandline will create incompatibilities with GCC and binutils unless we did the same.

I am not exposing any of +mte/+mte2 on the commandline, so there shouldn't be any concerns for compatibility with GCC.

https://github.com/llvm/llvm-project/pull/109299