[llvm] [AArch64][PAC] Don't skip global legalization for AUTH_TCRETURN (PR #182513)

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eleviant wrote:

> can hardly materialize a pointer in x0 with a valid signature in its top-most bits, as the range for adrp is only 4GiB

You do have a GOT for this. https://en.wikipedia.org/wiki/Global_Offset_Table
I've updated the test file. For your C example you can use -fPIC

https://github.com/llvm/llvm-project/pull/182513