Add pointer masking convenience functions
This PR adds the following public API:
```rust
impl<T: ?Sized> *const T {
fn mask(self, mask: usize) -> *const T;
}
impl<T: ?Sized> *mut T {
fn mask(self, mask: usize) -> *const T;
}
// mod intrinsics
fn mask<T>(ptr: *const T, mask: usize) -> *const T
```
This is equivalent to `ptr.map_addr(|a| a & mask)` but also uses a cool llvm intrinsic.
Proposed in https://github.com/rust-lang/rust/pull/95643#issuecomment-1121562352
cc `@Gankra` `@scottmcm` `@RalfJung`
r? rust-lang/libs-api
Because `PassMode::Cast` is by far the largest variant, but is
relatively rare.
This requires making `PassMode` not impl `Copy`, and `Clone` is no
longer necessary. This causes lots of sigil adjusting, but nothing very
notable.
Add the intrinsic
declare {i8*, i1} @llvm.type.checked.load(i8* %ptr, i32 %offset, metadata %type)
This is used in the VFE optimization when lowering loading functions
from vtables to LLVM IR. The `metadata` is used to map the function to
all vtables this function could belong to. This ensures that functions
from vtables that might be used somewhere won't get removed.
It looks like the last time had left some remaining cfg's -- which made me think
that the stage0 bump was actually successful. This brings us to a released 1.62
beta though.
`Layout` is another type that is sometimes interned, sometimes not, and
we always use references to refer to it so we can't take any advantage
of the uniqueness properties for hashing or equality checks.
This commit renames `Layout` as `LayoutS`, and then introduces a new
`Layout` that is a newtype around an `Interned<LayoutS>`. It also
interns more layouts than before. Previously layouts within layouts
(via the `variants` field) were never interned, but now they are. Hence
the lifetime on the new `Layout` type.
Unlike other interned types, these ones are in `rustc_target` instead of
`rustc_middle`. This reflects the existing structure of the code, which
does layout-specific stuff in `rustc_target` while `TyAndLayout` is
generic over the `Ty`, allowing the type-specific stuff to occur in
`rustc_middle`.
The commit also adds a `HashStable` impl for `Interned`, which was
needed. It hashes the contents, unlike the `Hash` impl which hashes the
pointer.
This commit adds LLVM Control Flow Integrity (CFI) support to the Rust
compiler. It initially provides forward-edge control flow protection for
Rust-compiled code only by aggregating function pointers in groups
identified by their number of arguments.
Forward-edge control flow protection for C or C++ and Rust -compiled
code "mixed binaries" (i.e., for when C or C++ and Rust -compiled code
share the same virtual address space) will be provided in later work as
part of this project by defining and using compatible type identifiers
(see Type metadata in the design document in the tracking issue #89653).
LLVM CFI can be enabled with -Zsanitizer=cfi and requires LTO (i.e.,
-Clto).
