[llvm] [AArch64][PAC] Combine signing with address materialization (PR #130809)

[Anatoly Trosinenko via llvm-commits]

atrosinenko wrote:

> One thing I'd like to see is a test case that tries to induce an oracle using the intrinsics in C

@ojhunt Do you suggest adding a real C source to `clang/test` or just adding LLVM IR emitted for C functions like these to LLVM tests introduced by this PR (and checking both MIR and final asm listing - among other things, this would check that dead instructions left by `EmitInstrWithCustomInserter` are eliminated down the pipeline)?

> In an ideal world - out of scope for this change - I think we'd like to error out if we ever see a read from memory into an unauthenticated sign, or a spill and subsequent read of an authenticated value.

IIUC there are a few cases when the former is valid - such as in a dynamic loader, so an opt-out machinery will be needed (such as maybe some function attribute).

https://github.com/llvm/llvm-project/pull/130809