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

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Wilco1 wrote:

> I think this difference would be ok in practice, since I can't imagine any scenario in which it would be beneficial to choose a +memtag version of a function when FEAT_MTE2 is not supported. However, if we include +memtag in FMV with this discrepancy, then we do have to be careful to avoid indirection elimination optimisations that assume that a function with +memtag enabled (via the command line or attributes) will always call a "memtag" function version at runtime.

Isn't the latter true for many features? A feature may be enabled on the command-line, but the kernel may turn it off.

Also HWCAP2_MTE is correct in the sense that it is only enabled when MTE can be used on the system. There is no point in selecting an MTE function if the kernel or system does not support MTE anyway...



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