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Rollup merge of #127337 - celinval:intrinsics-fallback, r=oli-obk
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Move a few intrinsics to Rust abi

Move a few more intrinsic functions to the convention added in #121192. In the second commit, I added documentation about their safety requirements. Let me know if you would like me to move the second commit to a different PR.

Note: I kept the same signature of `pref_align_of`, but I was wondering why this function is considered unsafe?
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@matthiaskrgr
matthiaskrgr authored Jul 17, 2024
2 parents 0472b2a + b096c08 commit 3ddfd97
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Showing 3 changed files with 166 additions and 63 deletions.
221 changes: 162 additions & 59 deletions library/core/src/intrinsics.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -947,7 +947,6 @@ extern "rust-intrinsic" {
#[rustc_const_stable(feature = "const_unreachable_unchecked", since = "1.57.0")]
#[rustc_nounwind]
pub fn unreachable() -> !;

}

/// Informs the optimizer that a condition is always true.
Expand Down Expand Up @@ -1018,78 +1017,40 @@ extern "rust-intrinsic" {
#[rustc_nounwind]
pub fn breakpoint();

/// The size of a type in bytes.
///
/// Note that, unlike most intrinsics, this is safe to call;
/// it does not require an `unsafe` block.
/// Therefore, implementations must not require the user to uphold
/// any safety invariants.
///
/// More specifically, this is the offset in bytes between successive
/// items of the same type, including alignment padding.
///
/// The stabilized version of this intrinsic is [`core::mem::size_of`].
#[cfg(bootstrap)]
#[rustc_const_stable(feature = "const_size_of", since = "1.40.0")]
#[rustc_safe_intrinsic]
#[rustc_nounwind]
pub fn size_of<T>() -> usize;

/// The minimum alignment of a type.
///
/// Note that, unlike most intrinsics, this is safe to call;
/// it does not require an `unsafe` block.
/// Therefore, implementations must not require the user to uphold
/// any safety invariants.
///
/// The stabilized version of this intrinsic is [`core::mem::align_of`].
#[cfg(bootstrap)]
#[rustc_const_stable(feature = "const_min_align_of", since = "1.40.0")]
#[rustc_safe_intrinsic]
#[rustc_nounwind]
pub fn min_align_of<T>() -> usize;
/// The preferred alignment of a type.
///
/// This intrinsic does not have a stable counterpart.
/// It's "tracking issue" is [#91971](https://github.com/rust-lang/rust/issues/91971).

#[cfg(bootstrap)]
#[rustc_const_unstable(feature = "const_pref_align_of", issue = "91971")]
#[rustc_nounwind]
pub fn pref_align_of<T>() -> usize;

/// The size of the referenced value in bytes.
///
/// The stabilized version of this intrinsic is [`crate::mem::size_of_val`].
#[cfg(bootstrap)]
#[rustc_const_unstable(feature = "const_size_of_val", issue = "46571")]
#[rustc_nounwind]
pub fn size_of_val<T: ?Sized>(_: *const T) -> usize;
/// The required alignment of the referenced value.
///
/// The stabilized version of this intrinsic is [`core::mem::align_of_val`].

#[cfg(bootstrap)]
#[rustc_const_unstable(feature = "const_align_of_val", issue = "46571")]
#[rustc_nounwind]
pub fn min_align_of_val<T: ?Sized>(_: *const T) -> usize;

/// Gets a static string slice containing the name of a type.
///
/// Note that, unlike most intrinsics, this is safe to call;
/// it does not require an `unsafe` block.
/// Therefore, implementations must not require the user to uphold
/// any safety invariants.
///
/// The stabilized version of this intrinsic is [`core::any::type_name`].
#[cfg(bootstrap)]
#[rustc_const_unstable(feature = "const_type_name", issue = "63084")]
#[rustc_safe_intrinsic]
#[rustc_nounwind]
pub fn type_name<T: ?Sized>() -> &'static str;

/// Gets an identifier which is globally unique to the specified type. This
/// function will return the same value for a type regardless of whichever
/// crate it is invoked in.
///
/// Note that, unlike most intrinsics, this is safe to call;
/// it does not require an `unsafe` block.
/// Therefore, implementations must not require the user to uphold
/// any safety invariants.
///
/// The stabilized version of this intrinsic is [`core::any::TypeId::of`].
#[cfg(bootstrap)]
#[rustc_const_unstable(feature = "const_type_id", issue = "77125")]
#[rustc_safe_intrinsic]
#[rustc_nounwind]
Expand Down Expand Up @@ -2424,15 +2385,7 @@ extern "rust-intrinsic" {
#[rustc_nounwind]
pub fn discriminant_value<T>(v: &T) -> <T as DiscriminantKind>::Discriminant;

/// Returns the number of variants of the type `T` cast to a `usize`;
/// if `T` has no variants, returns `0`. Uninhabited variants will be counted.
///
/// Note that, unlike most intrinsics, this is safe to call;
/// it does not require an `unsafe` block.
/// Therefore, implementations must not require the user to uphold
/// any safety invariants.
///
/// The to-be-stabilized version of this intrinsic is [`crate::mem::variant_count`].
#[cfg(bootstrap)]
#[rustc_const_unstable(feature = "variant_count", issue = "73662")]
#[rustc_safe_intrinsic]
#[rustc_nounwind]
Expand Down Expand Up @@ -2773,8 +2726,11 @@ pub const unsafe fn const_deallocate(_ptr: *mut u8, _size: usize, _align: usize)
// Runtime NOP
}

/// `ptr` must point to a vtable.
/// The intrinsic will return the size stored in that vtable.
///
/// # Safety
///
/// `ptr` must point to a vtable.
#[rustc_nounwind]
#[unstable(feature = "core_intrinsics", issue = "none")]
#[rustc_intrinsic]
Expand All @@ -2783,8 +2739,11 @@ pub unsafe fn vtable_size(_ptr: *const ()) -> usize {
unreachable!()
}

/// `ptr` must point to a vtable.
/// The intrinsic will return the alignment stored in that vtable.
///
/// # Safety
///
/// `ptr` must point to a vtable.
#[rustc_nounwind]
#[unstable(feature = "core_intrinsics", issue = "none")]
#[rustc_intrinsic]
Expand All @@ -2793,6 +2752,150 @@ pub unsafe fn vtable_align(_ptr: *const ()) -> usize {
unreachable!()
}

/// The size of a type in bytes.
///
/// Note that, unlike most intrinsics, this is safe to call;
/// it does not require an `unsafe` block.
/// Therefore, implementations must not require the user to uphold
/// any safety invariants.
///
/// More specifically, this is the offset in bytes between successive
/// items of the same type, including alignment padding.
///
/// The stabilized version of this intrinsic is [`core::mem::size_of`].
#[rustc_nounwind]
#[unstable(feature = "core_intrinsics", issue = "none")]
#[rustc_const_stable(feature = "const_size_of", since = "1.40.0")]
#[rustc_intrinsic]
#[rustc_intrinsic_must_be_overridden]
#[cfg(not(bootstrap))]
pub const fn size_of<T>() -> usize {
unreachable!()
}

/// The minimum alignment of a type.
///
/// Note that, unlike most intrinsics, this is safe to call;
/// it does not require an `unsafe` block.
/// Therefore, implementations must not require the user to uphold
/// any safety invariants.
///
/// The stabilized version of this intrinsic is [`core::mem::align_of`].
#[rustc_nounwind]
#[unstable(feature = "core_intrinsics", issue = "none")]
#[rustc_const_stable(feature = "const_min_align_of", since = "1.40.0")]
#[rustc_intrinsic]
#[rustc_intrinsic_must_be_overridden]
#[cfg(not(bootstrap))]
pub const fn min_align_of<T>() -> usize {
unreachable!()
}

/// The preferred alignment of a type.
///
/// This intrinsic does not have a stable counterpart.
/// It's "tracking issue" is [#91971](https://github.com/rust-lang/rust/issues/91971).
#[rustc_nounwind]
#[unstable(feature = "core_intrinsics", issue = "none")]
#[rustc_const_unstable(feature = "const_pref_align_of", issue = "91971")]
#[rustc_intrinsic]
#[rustc_intrinsic_must_be_overridden]
#[cfg(not(bootstrap))]
pub const unsafe fn pref_align_of<T>() -> usize {
unreachable!()
}

/// Returns the number of variants of the type `T` cast to a `usize`;
/// if `T` has no variants, returns `0`. Uninhabited variants will be counted.
///
/// Note that, unlike most intrinsics, this is safe to call;
/// it does not require an `unsafe` block.
/// Therefore, implementations must not require the user to uphold
/// any safety invariants.
///
/// The to-be-stabilized version of this intrinsic is [`crate::mem::variant_count`].
#[rustc_nounwind]
#[unstable(feature = "core_intrinsics", issue = "none")]
#[rustc_const_unstable(feature = "variant_count", issue = "73662")]
#[rustc_intrinsic]
#[rustc_intrinsic_must_be_overridden]
#[cfg(not(bootstrap))]
pub const fn variant_count<T>() -> usize {
unreachable!()
}

/// The size of the referenced value in bytes.
///
/// The stabilized version of this intrinsic is [`crate::mem::size_of_val`].
///
/// # Safety
///
/// See [`crate::mem::size_of_val_raw`] for safety conditions.
#[rustc_nounwind]
#[unstable(feature = "core_intrinsics", issue = "none")]
#[rustc_const_unstable(feature = "const_size_of_val", issue = "46571")]
#[rustc_intrinsic]
#[rustc_intrinsic_must_be_overridden]
#[cfg(not(bootstrap))]
pub const unsafe fn size_of_val<T: ?Sized>(_ptr: *const T) -> usize {
unreachable!()
}

/// The required alignment of the referenced value.
///
/// The stabilized version of this intrinsic is [`core::mem::align_of_val`].
///
/// # Safety
///
/// See [`crate::mem::align_of_val_raw`] for safety conditions.
#[rustc_nounwind]
#[unstable(feature = "core_intrinsics", issue = "none")]
#[rustc_const_unstable(feature = "const_align_of_val", issue = "46571")]
#[rustc_intrinsic]
#[rustc_intrinsic_must_be_overridden]
#[cfg(not(bootstrap))]
pub const unsafe fn min_align_of_val<T: ?Sized>(_ptr: *const T) -> usize {
unreachable!()
}

/// Gets a static string slice containing the name of a type.
///
/// Note that, unlike most intrinsics, this is safe to call;
/// it does not require an `unsafe` block.
/// Therefore, implementations must not require the user to uphold
/// any safety invariants.
///
/// The stabilized version of this intrinsic is [`core::any::type_name`].
#[rustc_nounwind]
#[unstable(feature = "core_intrinsics", issue = "none")]
#[rustc_const_unstable(feature = "const_type_name", issue = "63084")]
#[rustc_intrinsic]
#[rustc_intrinsic_must_be_overridden]
#[cfg(not(bootstrap))]
pub const fn type_name<T: ?Sized>() -> &'static str {
unreachable!()
}

/// Gets an identifier which is globally unique to the specified type. This
/// function will return the same value for a type regardless of whichever
/// crate it is invoked in.
///
/// Note that, unlike most intrinsics, this is safe to call;
/// it does not require an `unsafe` block.
/// Therefore, implementations must not require the user to uphold
/// any safety invariants.
///
/// The stabilized version of this intrinsic is [`core::any::TypeId::of`].
#[rustc_nounwind]
#[unstable(feature = "core_intrinsics", issue = "none")]
#[rustc_const_unstable(feature = "const_type_id", issue = "77125")]
#[rustc_intrinsic]
#[rustc_intrinsic_must_be_overridden]
#[cfg(not(bootstrap))]
pub const fn type_id<T: ?Sized + 'static>() -> u128 {
unreachable!()
}

/// Lowers in MIR to `Rvalue::Aggregate` with `AggregateKind::RawPtr`.
///
/// This is used to implement functions like `slice::from_raw_parts_mut` and
Expand Down
4 changes: 2 additions & 2 deletions tests/mir-opt/lower_intrinsics.non_const.LowerIntrinsics.panic-abort.diff
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Original file line number Diff line number Diff line change
Expand Up @@ -3,8 +3,8 @@

fn non_const() -> usize {
let mut _0: usize;
let _1: extern "rust-intrinsic" fn() -> usize {std::intrinsics::size_of::<T>};
let mut _2: extern "rust-intrinsic" fn() -> usize {std::intrinsics::size_of::<T>};
let _1: fn() -> usize {std::intrinsics::size_of::<T>};
let mut _2: fn() -> usize {std::intrinsics::size_of::<T>};
scope 1 {
debug size_of_t => _1;
}
Expand Down
4 changes: 2 additions & 2 deletions tests/mir-opt/lower_intrinsics.non_const.LowerIntrinsics.panic-unwind.diff
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Original file line number Diff line number Diff line change
Expand Up @@ -3,8 +3,8 @@

fn non_const() -> usize {
let mut _0: usize;
let _1: extern "rust-intrinsic" fn() -> usize {std::intrinsics::size_of::<T>};
let mut _2: extern "rust-intrinsic" fn() -> usize {std::intrinsics::size_of::<T>};
let _1: fn() -> usize {std::intrinsics::size_of::<T>};
let mut _2: fn() -> usize {std::intrinsics::size_of::<T>};
scope 1 {
debug size_of_t => _1;
}
Expand Down

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