[llvm] [ARM] Allow tTAILJMPd on v8-M Baseline (PR #216747)

[Ahmed Bougacha via llvm-commits]

https://github.com/ahmedbougacha approved this pull request.

That v8-m.base is subsetting v6t2 makes this (and a1189106d5a1b9e9ff57ea6fa53c24e891f1d09c, looking at it now) quite puzzling at first, but this makes sense, thanks!

I have to imagine we compute the Requires for pseudo-expand defs, in which case you could drop it altogether?  But eh it kinda makes it unreadable, and it's a bit too late for that now anyway, so probably best to leave it as-is?

https://github.com/llvm/llvm-project/pull/216747