[WIP] 3 - FPTR_TYPE_DISCR in ABI Version#159075
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This patch brings: * unified handling of pointer authentication options through: `-Zpointer-authentication`, with possible values: `aarch64-jump-table-hardening`, `auth-traps`, `calls`, `elf-got`, `function-pointer-type-discrimination`, `indirect-gotos`, `init-fini`, `init-fini-address-discrimination`, `return-addresses`. Toggled with `+`/`-`. * centralized handling of pointer authentication features. Session holds `pointer_auth_config: Option<PointerAuthConfig>` * encapsulation of schema for function pointers and init/fini through `PointerAuthSchema`. This allowed for retiring of `PacMetadata`. * refactor enabling of pointer authentication in code, instead of relying on the target (`pauthtest`) use the session
Also improve the API design of pointer_authentication_functions, by making it return Option<&PointerAuthSchema>, rather than bool.
This patch implements Rust's equivalent of Clang's function pointer type discriminator computation used in pointer authentication. Compatibility with Clang is a primary goal. The discriminator produced for a given external "C" function type must match the value computed by Clang so that function pointers can be exchanged safely between Rust and C code while preserving pointer authentication semantics. The implementation mirrors Clang's behavior in `ASTContext::encodeTypeForFunctionPointerAuth`, ensuring that identical C-compatible function types produce identical discriminators. See: <https://clang.llvm.org/doxygen/ASTContext_8cpp.html#abb1375e068e807917527842d05cadea3>.
This patch introduces the following: * Extends `FnAbi` (`callconv`) with a `ptrauth_type_discriminator` field. This field is only used when emitting pointer authentication call bundles. It is stored in `FnAbi` because the call site is not guaranteed to have access to an `Instance`, so the discriminator cannot always be computed on demand. * Adds support for `llvm.ptrauth.resign`. This intrinsic will be used when support for semantic transmute is added. * Performs a minor API redesign as groundwork for allowing call sites to modify schemas in place.
Also remove error messages/tests that used to guarded it.
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This was referenced Jul 10, 2026
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This patch extends ABI version to contain FPTR_TYPE_DISCR. It also removes error messages/tests that used to guarded (previously unsupported) function pointer type discrimination.
This is part 3 of a sequence of 8 PRs, that together aim to bring function pointer type discrimination support:
Useful links:
pauthtestintroduction: Introduce aarch64-unknown-linux-pauthtest target #155722