[AArch64] Lower ptrauth.sign of constant as PtrAuthGlobalAddress. #133788
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This lets us guarantee the emission of one of our hardened constant signed pointer materialization sequences, rather than emitting the sign intrinsic as a naked sign, and exposing the raw pointer. Do that in the builder to help guarantee that through the backend. At the IR level, there aren't great ways to enforce that the constant operand to the intrinsic stays there, but we might be able to do that by generalizing immarg to be applicable to callsites rather than just Intrinsic definitions. That's all theoretical either way, and there's rarely a good reason to hoist a constant op from an intrinsic anyway. This is pretty tolerant of weird discriminators, which should cover the interesting cases.
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This lets us guarantee the emission of one of our hardened constant signed pointer materialization sequences, rather than emitting the sign intrinsic as a naked sign, and exposing the raw pointer.
Do that in the builder to help guarantee that through the backend.
At the IR level, there aren't great ways to enforce that the constant operand to the intrinsic stays there, but we might be able to do that by generalizing immarg to be applicable to callsites rather than just Intrinsic definitions. That's all theoretical either way, and there's rarely a good reason to hoist a constant op from an intrinsic anyway.
This is pretty tolerant of weird discriminators, which should cover the interesting cases.