[llvm] [BOLT][AArch64] Support for pointer authentication (v2) (PR #120064)

[Paschalis Mpeis via llvm-commits]

paschalis-mpeis wrote:

>
> > Since this is a new feature, do you think it might be worth guarding it with a flag to make it more explicit to users? For example, fail with some advice when the flag is not present, otherwise process Negate-RA CFIs.
> 
> Good point, will do.
> 
> >  Regardless, I think it would be helpful to emit a BOLT-INFO stat summarizing what was done. So users are aware that this feature was used and applied to N places.
> 
> I am not sure if this would be very useful for users.
>

My reasoning was to output information so users are aware of what's happening under the hood.
Guarding this with a flag is even better (and my preference).

---

> Possibly, target-specific hooks like [getAuthenticatedReg](https://github.com/llvm/llvm-project/blob/main/bolt/lib/Target/AArch64/AArch64MCPlusBuilder.cpp#L199) and getTrustedLiveInRegs (to guess "the LR" without referring to AArch64::LR from target-independent code) could be reused.

@atrosinenko sounds like a good idea.


https://github.com/llvm/llvm-project/pull/120064