================
@@ -1056,12 +1056,18 @@ class ConstantPtrAuth final : public Constant {
return !getAddrDiscriminator()->isNullValue();
}
- /// A constant value for the address discriminator which has special
- /// significance to ctors/dtors lowering. Regular address discrimination
can't
- /// be applied for them since uses of llvm.global_{c|d}tors are disallowed
- /// (see Verifier::visitGlobalVariable) and we can't emit getelementptr
- /// expressions referencing these special arrays.
- enum { AddrDiscriminator_CtorsDtors = 1 };
+ /// Constant values for the address discriminator which have special
+ /// significance to lowering in some contexts.
+ /// - For ctors/dtors, regular address discrimination can't
+ /// be applied for them since uses of llvm.global_{c|d}tors are disallowed
+ /// (see Verifier::visitGlobalVariable) and we can't emit getelementptr
+ /// expressions referencing these special arrays.
+ /// - For vtable pointers of std::type_info and classes derived from it,
+ /// we do not know the storage address when emitting ptrauth constant.
----------------
kovdan01 wrote:
> Would it work to wire the storage address through
> `ItaniumRTTIBuilder::BuildVTablePointer` from `BuildTypeInfo` ?
@ahmedbougacha I was unable to find a straight-forward way to do that, but I
might be missing smth (and it might be even smth obvious). I would be glad to
see more detailed suggestions if you have some better implementation in mind -
I agree that having an actual address instead of a placeholder is much better.
> Beyond that, for static ctors, as I mentioned before, I still don't think
> this should have ptrauth at the IR level, but rather should be a backend
> decision made when encoding the IR representation of "a list of static
> ctors/dtors" to some object file format encoding thereof. That would avoid
> needing this address discriminator placeholder dance here. But I suppose
> that's a separate problem.
This sounds nice, it's an interesting suggestion. Anyway, init/fini stuff is
out of scope of this PR
https://github.com/llvm/llvm-project/pull/102199
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