[llvm] [AArch64] Refactor @plt, @gotpcrel, and @AUTH to use parseDataExpr (PR #134202)

[David Benjamin via llvm-commits]

davidben wrote:

The relevant source file is actually synthesized from a perl script (don't ask; it's OpenSSL's fault) that transforms ELF-style `:pg_hi21:foo` into Apple-style `foo at PAGE` and whatnot. Looks like the regex did not capture the `-64` and put the `@PAGE` suffix in the middle of the term. It is a little odd that it got emitted that way, but I guess it worked and no one noticed?

I take it `Lone_mont-64 at PAGE` would be more correct? After someone confirms that is indeed the right syntax (been trying to find an official reference and not succeeding), I can fix BoringSSL to emit that.

That said, it looks like OpenSSL (which has a similar file) does the same thing, so I suspect LLVM will need to support `Lone_mont at PAGE-64`, as ridiculous as this looks. (You won't find it in OpenSSL's source tree because they run the Perl scripts as part of the build.)

https://github.com/llvm/llvm-project/pull/134202