[llvm] [PAC][CodeGen][ELF][AArch64] Support signed GOT (PR #105798)

[Daniil Kovalev via llvm-commits]

kovdan01 wrote:

Comparing to original PR #96164, this one has a couple of differences:

- `LOADgotAUTH` expansion code is moved from expand pseudos pass to asm printer. For other similar PAC-related pseudos, like `LOADgotPAC`, the expansion code is already placed in asm printer, so it's probably better to keep things consistent and add new code to the same place (given that I don't see strong reasons to put it earlier in pipeline in expand pseudos pass).

- If resign is requested, we cannot just do `aut{i|d}a` and then `pac{i|d}a` w/o FPAC bit set. In such a case, if authentication failure occurs, we'll just silently sign the pointer, while we want to check if authentication was successful and somehow fail if it was not. With FPAC, this is done implicitly, w/o that - we need to do that manually. The check+trap sequence code is similar to one used in `AUTPAC` pseudo expansion.



https://github.com/llvm/llvm-project/pull/105798