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Note that Apple only shipped pointer authentication so far, not memory tagging.

Memory tagging only will ship on ARMv9 products in practice, across the board.

Thanks for the correction. The Apple A14 and M1 implement the ARMv8.4 spec, whereas memory tagging became part of the spec in 8.5.

Those chips implement almost all of ARMv8.5, and this is what LLVM identifies them as.

Outside ARM world, SPARC has had hardware memory tagging for ages and it used on Solaris by default.

IBM s/370 (possibly even s/360) too had memory page tagging -- see instructions ISK / ISKE.

Yes, Burroughs as well in 1961.

The point was more about systems where we have to deal with C, or derived systems languages, and the related culture that performance trumps safety.