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intrinsics.rs
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intrinsics.rs
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//! Compiler intrinsics.
//!
//! The corresponding definitions are in <https://github.com/rust-lang/rust/blob/master/compiler/rustc_codegen_llvm/src/intrinsic.rs>.
//! The corresponding const implementations are in <https://github.com/rust-lang/rust/blob/master/compiler/rustc_const_eval/src/interpret/intrinsics.rs>.
//!
//! # Const intrinsics
//!
//! Note: any changes to the constness of intrinsics should be discussed with the language team.
//! This includes changes in the stability of the constness.
//!
//! In order to make an intrinsic usable at compile-time, one needs to copy the implementation
//! from <https://github.com/rust-lang/miri/blob/master/src/shims/intrinsics> to
//! <https://github.com/rust-lang/rust/blob/master/compiler/rustc_const_eval/src/interpret/intrinsics.rs> and add a
//! `#[rustc_const_unstable(feature = "const_such_and_such", issue = "01234")]` to the intrinsic declaration.
//!
//! If an intrinsic is supposed to be used from a `const fn` with a `rustc_const_stable` attribute,
//! the intrinsic's attribute must be `rustc_const_stable`, too. Such a change should not be done
//! without T-lang consultation, because it bakes a feature into the language that cannot be
//! replicated in user code without compiler support.
//!
//! # Volatiles
//!
//! The volatile intrinsics provide operations intended to act on I/O
//! memory, which are guaranteed to not be reordered by the compiler
//! across other volatile intrinsics. See the LLVM documentation on
//! [[volatile]].
//!
//! [volatile]: https://llvm.org/docs/LangRef.html#volatile-memory-accesses
//!
//! # Atomics
//!
//! The atomic intrinsics provide common atomic operations on machine
//! words, with multiple possible memory orderings. They obey the same
//! semantics as C++11. See the LLVM documentation on [[atomics]].
//!
//! [atomics]: https://llvm.org/docs/Atomics.html
//!
//! A quick refresher on memory ordering:
//!
//! * Acquire - a barrier for acquiring a lock. Subsequent reads and writes
//! take place after the barrier.
//! * Release - a barrier for releasing a lock. Preceding reads and writes
//! take place before the barrier.
//! * Sequentially consistent - sequentially consistent operations are
//! guaranteed to happen in order. This is the standard mode for working
//! with atomic types and is equivalent to Java's `volatile`.
//!
//! # Unwinding
//!
//! Rust intrinsics may, in general, unwind. If an intrinsic can never unwind, add the
//! `#[rustc_nounwind]` attribute so that the compiler can make use of this fact.
//!
//! However, even for intrinsics that may unwind, rustc assumes that a Rust intrinsics will never
//! initiate a foreign (non-Rust) unwind, and thus for panic=abort we can always assume that these
//! intrinsics cannot unwind.
#![unstable(
feature = "core_intrinsics",
reason = "intrinsics are unlikely to ever be stabilized, instead \
they should be used through stabilized interfaces \
in the rest of the standard library",
issue = "none"
)]
#![allow(missing_docs)]
use crate::marker::DiscriminantKind;
use crate::marker::Tuple;
use crate::ptr;
use crate::ub_checks;
pub mod mir;
pub mod simd;
// These imports are used for simplifying intra-doc links
#[allow(unused_imports)]
#[cfg(all(target_has_atomic = "8", target_has_atomic = "32", target_has_atomic = "ptr"))]
use crate::sync::atomic::{self, AtomicBool, AtomicI32, AtomicIsize, AtomicU32, Ordering};
#[stable(feature = "drop_in_place", since = "1.8.0")]
#[rustc_allowed_through_unstable_modules]
#[deprecated(note = "no longer an intrinsic - use `ptr::drop_in_place` directly", since = "1.52.0")]
#[inline]
pub unsafe fn drop_in_place<T: ?Sized>(to_drop: *mut T) {
// SAFETY: see `ptr::drop_in_place`
unsafe { crate::ptr::drop_in_place(to_drop) }
}
extern "rust-intrinsic" {
// N.B., these intrinsics take raw pointers because they mutate aliased
// memory, which is not valid for either `&` or `&mut`.
/// Stores a value if the current value is the same as the `old` value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `compare_exchange` method by passing
/// [`Ordering::Relaxed`] as both the success and failure parameters.
/// For example, [`AtomicBool::compare_exchange`].
#[rustc_nounwind]
pub fn atomic_cxchg_relaxed_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
/// Stores a value if the current value is the same as the `old` value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `compare_exchange` method by passing
/// [`Ordering::Relaxed`] and [`Ordering::Acquire`] as the success and failure parameters.
/// For example, [`AtomicBool::compare_exchange`].
#[rustc_nounwind]
pub fn atomic_cxchg_relaxed_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
/// Stores a value if the current value is the same as the `old` value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `compare_exchange` method by passing
/// [`Ordering::Relaxed`] and [`Ordering::SeqCst`] as the success and failure parameters.
/// For example, [`AtomicBool::compare_exchange`].
#[rustc_nounwind]
pub fn atomic_cxchg_relaxed_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
/// Stores a value if the current value is the same as the `old` value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `compare_exchange` method by passing
/// [`Ordering::Acquire`] and [`Ordering::Relaxed`] as the success and failure parameters.
/// For example, [`AtomicBool::compare_exchange`].
#[rustc_nounwind]
pub fn atomic_cxchg_acquire_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
/// Stores a value if the current value is the same as the `old` value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `compare_exchange` method by passing
/// [`Ordering::Acquire`] as both the success and failure parameters.
/// For example, [`AtomicBool::compare_exchange`].
#[rustc_nounwind]
pub fn atomic_cxchg_acquire_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
/// Stores a value if the current value is the same as the `old` value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `compare_exchange` method by passing
/// [`Ordering::Acquire`] and [`Ordering::SeqCst`] as the success and failure parameters.
/// For example, [`AtomicBool::compare_exchange`].
#[rustc_nounwind]
pub fn atomic_cxchg_acquire_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
/// Stores a value if the current value is the same as the `old` value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `compare_exchange` method by passing
/// [`Ordering::Release`] and [`Ordering::Relaxed`] as the success and failure parameters.
/// For example, [`AtomicBool::compare_exchange`].
#[rustc_nounwind]
pub fn atomic_cxchg_release_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
/// Stores a value if the current value is the same as the `old` value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `compare_exchange` method by passing
/// [`Ordering::Release`] and [`Ordering::Acquire`] as the success and failure parameters.
/// For example, [`AtomicBool::compare_exchange`].
#[rustc_nounwind]
pub fn atomic_cxchg_release_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
/// Stores a value if the current value is the same as the `old` value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `compare_exchange` method by passing
/// [`Ordering::Release`] and [`Ordering::SeqCst`] as the success and failure parameters.
/// For example, [`AtomicBool::compare_exchange`].
#[rustc_nounwind]
pub fn atomic_cxchg_release_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
/// Stores a value if the current value is the same as the `old` value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `compare_exchange` method by passing
/// [`Ordering::AcqRel`] and [`Ordering::Relaxed`] as the success and failure parameters.
/// For example, [`AtomicBool::compare_exchange`].
#[rustc_nounwind]
pub fn atomic_cxchg_acqrel_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
/// Stores a value if the current value is the same as the `old` value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `compare_exchange` method by passing
/// [`Ordering::AcqRel`] and [`Ordering::Acquire`] as the success and failure parameters.
/// For example, [`AtomicBool::compare_exchange`].
#[rustc_nounwind]
pub fn atomic_cxchg_acqrel_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
/// Stores a value if the current value is the same as the `old` value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `compare_exchange` method by passing
/// [`Ordering::AcqRel`] and [`Ordering::SeqCst`] as the success and failure parameters.
/// For example, [`AtomicBool::compare_exchange`].
#[rustc_nounwind]
pub fn atomic_cxchg_acqrel_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
/// Stores a value if the current value is the same as the `old` value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `compare_exchange` method by passing
/// [`Ordering::SeqCst`] and [`Ordering::Relaxed`] as the success and failure parameters.
/// For example, [`AtomicBool::compare_exchange`].
#[rustc_nounwind]
pub fn atomic_cxchg_seqcst_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
/// Stores a value if the current value is the same as the `old` value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `compare_exchange` method by passing
/// [`Ordering::SeqCst`] and [`Ordering::Acquire`] as the success and failure parameters.
/// For example, [`AtomicBool::compare_exchange`].
#[rustc_nounwind]
pub fn atomic_cxchg_seqcst_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
/// Stores a value if the current value is the same as the `old` value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `compare_exchange` method by passing
/// [`Ordering::SeqCst`] as both the success and failure parameters.
/// For example, [`AtomicBool::compare_exchange`].
#[rustc_nounwind]
pub fn atomic_cxchg_seqcst_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
/// Stores a value if the current value is the same as the `old` value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `compare_exchange_weak` method by passing
/// [`Ordering::Relaxed`] as both the success and failure parameters.
/// For example, [`AtomicBool::compare_exchange_weak`].
#[rustc_nounwind]
pub fn atomic_cxchgweak_relaxed_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
/// Stores a value if the current value is the same as the `old` value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `compare_exchange_weak` method by passing
/// [`Ordering::Relaxed`] and [`Ordering::Acquire`] as the success and failure parameters.
/// For example, [`AtomicBool::compare_exchange_weak`].
#[rustc_nounwind]
pub fn atomic_cxchgweak_relaxed_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
/// Stores a value if the current value is the same as the `old` value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `compare_exchange_weak` method by passing
/// [`Ordering::Relaxed`] and [`Ordering::SeqCst`] as the success and failure parameters.
/// For example, [`AtomicBool::compare_exchange_weak`].
#[rustc_nounwind]
pub fn atomic_cxchgweak_relaxed_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
/// Stores a value if the current value is the same as the `old` value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `compare_exchange_weak` method by passing
/// [`Ordering::Acquire`] and [`Ordering::Relaxed`] as the success and failure parameters.
/// For example, [`AtomicBool::compare_exchange_weak`].
#[rustc_nounwind]
pub fn atomic_cxchgweak_acquire_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
/// Stores a value if the current value is the same as the `old` value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `compare_exchange_weak` method by passing
/// [`Ordering::Acquire`] as both the success and failure parameters.
/// For example, [`AtomicBool::compare_exchange_weak`].
#[rustc_nounwind]
pub fn atomic_cxchgweak_acquire_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
/// Stores a value if the current value is the same as the `old` value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `compare_exchange_weak` method by passing
/// [`Ordering::Acquire`] and [`Ordering::SeqCst`] as the success and failure parameters.
/// For example, [`AtomicBool::compare_exchange_weak`].
#[rustc_nounwind]
pub fn atomic_cxchgweak_acquire_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
/// Stores a value if the current value is the same as the `old` value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `compare_exchange_weak` method by passing
/// [`Ordering::Release`] and [`Ordering::Relaxed`] as the success and failure parameters.
/// For example, [`AtomicBool::compare_exchange_weak`].
#[rustc_nounwind]
pub fn atomic_cxchgweak_release_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
/// Stores a value if the current value is the same as the `old` value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `compare_exchange_weak` method by passing
/// [`Ordering::Release`] and [`Ordering::Acquire`] as the success and failure parameters.
/// For example, [`AtomicBool::compare_exchange_weak`].
#[rustc_nounwind]
pub fn atomic_cxchgweak_release_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
/// Stores a value if the current value is the same as the `old` value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `compare_exchange_weak` method by passing
/// [`Ordering::Release`] and [`Ordering::SeqCst`] as the success and failure parameters.
/// For example, [`AtomicBool::compare_exchange_weak`].
#[rustc_nounwind]
pub fn atomic_cxchgweak_release_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
/// Stores a value if the current value is the same as the `old` value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `compare_exchange_weak` method by passing
/// [`Ordering::AcqRel`] and [`Ordering::Relaxed`] as the success and failure parameters.
/// For example, [`AtomicBool::compare_exchange_weak`].
#[rustc_nounwind]
pub fn atomic_cxchgweak_acqrel_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
/// Stores a value if the current value is the same as the `old` value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `compare_exchange_weak` method by passing
/// [`Ordering::AcqRel`] and [`Ordering::Acquire`] as the success and failure parameters.
/// For example, [`AtomicBool::compare_exchange_weak`].
#[rustc_nounwind]
pub fn atomic_cxchgweak_acqrel_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
/// Stores a value if the current value is the same as the `old` value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `compare_exchange_weak` method by passing
/// [`Ordering::AcqRel`] and [`Ordering::SeqCst`] as the success and failure parameters.
/// For example, [`AtomicBool::compare_exchange_weak`].
#[rustc_nounwind]
pub fn atomic_cxchgweak_acqrel_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
/// Stores a value if the current value is the same as the `old` value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `compare_exchange_weak` method by passing
/// [`Ordering::SeqCst`] and [`Ordering::Relaxed`] as the success and failure parameters.
/// For example, [`AtomicBool::compare_exchange_weak`].
#[rustc_nounwind]
pub fn atomic_cxchgweak_seqcst_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
/// Stores a value if the current value is the same as the `old` value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `compare_exchange_weak` method by passing
/// [`Ordering::SeqCst`] and [`Ordering::Acquire`] as the success and failure parameters.
/// For example, [`AtomicBool::compare_exchange_weak`].
#[rustc_nounwind]
pub fn atomic_cxchgweak_seqcst_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
/// Stores a value if the current value is the same as the `old` value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `compare_exchange_weak` method by passing
/// [`Ordering::SeqCst`] as both the success and failure parameters.
/// For example, [`AtomicBool::compare_exchange_weak`].
#[rustc_nounwind]
pub fn atomic_cxchgweak_seqcst_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
/// Loads the current value of the pointer.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `load` method by passing
/// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicBool::load`].
#[rustc_nounwind]
pub fn atomic_load_seqcst<T: Copy>(src: *const T) -> T;
/// Loads the current value of the pointer.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `load` method by passing
/// [`Ordering::Acquire`] as the `order`. For example, [`AtomicBool::load`].
#[rustc_nounwind]
pub fn atomic_load_acquire<T: Copy>(src: *const T) -> T;
/// Loads the current value of the pointer.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `load` method by passing
/// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicBool::load`].
#[rustc_nounwind]
pub fn atomic_load_relaxed<T: Copy>(src: *const T) -> T;
/// Do NOT use this intrinsic; "unordered" operations do not exist in our memory model!
/// In terms of the Rust Abstract Machine, this operation is equivalent to `src.read()`,
/// i.e., it performs a non-atomic read.
#[rustc_nounwind]
pub fn atomic_load_unordered<T: Copy>(src: *const T) -> T;
/// Stores the value at the specified memory location.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `store` method by passing
/// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicBool::store`].
#[rustc_nounwind]
pub fn atomic_store_seqcst<T: Copy>(dst: *mut T, val: T);
/// Stores the value at the specified memory location.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `store` method by passing
/// [`Ordering::Release`] as the `order`. For example, [`AtomicBool::store`].
#[rustc_nounwind]
pub fn atomic_store_release<T: Copy>(dst: *mut T, val: T);
/// Stores the value at the specified memory location.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `store` method by passing
/// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicBool::store`].
#[rustc_nounwind]
pub fn atomic_store_relaxed<T: Copy>(dst: *mut T, val: T);
/// Do NOT use this intrinsic; "unordered" operations do not exist in our memory model!
/// In terms of the Rust Abstract Machine, this operation is equivalent to `dst.write(val)`,
/// i.e., it performs a non-atomic write.
#[rustc_nounwind]
pub fn atomic_store_unordered<T: Copy>(dst: *mut T, val: T);
/// Stores the value at the specified memory location, returning the old value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `swap` method by passing
/// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicBool::swap`].
#[rustc_nounwind]
pub fn atomic_xchg_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
/// Stores the value at the specified memory location, returning the old value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `swap` method by passing
/// [`Ordering::Acquire`] as the `order`. For example, [`AtomicBool::swap`].
#[rustc_nounwind]
pub fn atomic_xchg_acquire<T: Copy>(dst: *mut T, src: T) -> T;
/// Stores the value at the specified memory location, returning the old value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `swap` method by passing
/// [`Ordering::Release`] as the `order`. For example, [`AtomicBool::swap`].
#[rustc_nounwind]
pub fn atomic_xchg_release<T: Copy>(dst: *mut T, src: T) -> T;
/// Stores the value at the specified memory location, returning the old value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `swap` method by passing
/// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicBool::swap`].
#[rustc_nounwind]
pub fn atomic_xchg_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
/// Stores the value at the specified memory location, returning the old value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `swap` method by passing
/// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicBool::swap`].
#[rustc_nounwind]
pub fn atomic_xchg_relaxed<T: Copy>(dst: *mut T, src: T) -> T;
/// Adds to the current value, returning the previous value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `fetch_add` method by passing
/// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicIsize::fetch_add`].
#[rustc_nounwind]
pub fn atomic_xadd_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
/// Adds to the current value, returning the previous value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `fetch_add` method by passing
/// [`Ordering::Acquire`] as the `order`. For example, [`AtomicIsize::fetch_add`].
#[rustc_nounwind]
pub fn atomic_xadd_acquire<T: Copy>(dst: *mut T, src: T) -> T;
/// Adds to the current value, returning the previous value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `fetch_add` method by passing
/// [`Ordering::Release`] as the `order`. For example, [`AtomicIsize::fetch_add`].
#[rustc_nounwind]
pub fn atomic_xadd_release<T: Copy>(dst: *mut T, src: T) -> T;
/// Adds to the current value, returning the previous value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `fetch_add` method by passing
/// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicIsize::fetch_add`].
#[rustc_nounwind]
pub fn atomic_xadd_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
/// Adds to the current value, returning the previous value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `fetch_add` method by passing
/// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicIsize::fetch_add`].
#[rustc_nounwind]
pub fn atomic_xadd_relaxed<T: Copy>(dst: *mut T, src: T) -> T;
/// Subtract from the current value, returning the previous value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `fetch_sub` method by passing
/// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicIsize::fetch_sub`].
#[rustc_nounwind]
pub fn atomic_xsub_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
/// Subtract from the current value, returning the previous value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `fetch_sub` method by passing
/// [`Ordering::Acquire`] as the `order`. For example, [`AtomicIsize::fetch_sub`].
#[rustc_nounwind]
pub fn atomic_xsub_acquire<T: Copy>(dst: *mut T, src: T) -> T;
/// Subtract from the current value, returning the previous value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `fetch_sub` method by passing
/// [`Ordering::Release`] as the `order`. For example, [`AtomicIsize::fetch_sub`].
#[rustc_nounwind]
pub fn atomic_xsub_release<T: Copy>(dst: *mut T, src: T) -> T;
/// Subtract from the current value, returning the previous value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `fetch_sub` method by passing
/// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicIsize::fetch_sub`].
#[rustc_nounwind]
pub fn atomic_xsub_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
/// Subtract from the current value, returning the previous value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `fetch_sub` method by passing
/// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicIsize::fetch_sub`].
#[rustc_nounwind]
pub fn atomic_xsub_relaxed<T: Copy>(dst: *mut T, src: T) -> T;
/// Bitwise and with the current value, returning the previous value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `fetch_and` method by passing
/// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicBool::fetch_and`].
#[rustc_nounwind]
pub fn atomic_and_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
/// Bitwise and with the current value, returning the previous value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `fetch_and` method by passing
/// [`Ordering::Acquire`] as the `order`. For example, [`AtomicBool::fetch_and`].
#[rustc_nounwind]
pub fn atomic_and_acquire<T: Copy>(dst: *mut T, src: T) -> T;
/// Bitwise and with the current value, returning the previous value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `fetch_and` method by passing
/// [`Ordering::Release`] as the `order`. For example, [`AtomicBool::fetch_and`].
#[rustc_nounwind]
pub fn atomic_and_release<T: Copy>(dst: *mut T, src: T) -> T;
/// Bitwise and with the current value, returning the previous value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `fetch_and` method by passing
/// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicBool::fetch_and`].
#[rustc_nounwind]
pub fn atomic_and_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
/// Bitwise and with the current value, returning the previous value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `fetch_and` method by passing
/// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicBool::fetch_and`].
#[rustc_nounwind]
pub fn atomic_and_relaxed<T: Copy>(dst: *mut T, src: T) -> T;
/// Bitwise nand with the current value, returning the previous value.
///
/// The stabilized version of this intrinsic is available on the
/// [`AtomicBool`] type via the `fetch_nand` method by passing
/// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicBool::fetch_nand`].
#[rustc_nounwind]
pub fn atomic_nand_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
/// Bitwise nand with the current value, returning the previous value.
///
/// The stabilized version of this intrinsic is available on the
/// [`AtomicBool`] type via the `fetch_nand` method by passing
/// [`Ordering::Acquire`] as the `order`. For example, [`AtomicBool::fetch_nand`].
#[rustc_nounwind]
pub fn atomic_nand_acquire<T: Copy>(dst: *mut T, src: T) -> T;
/// Bitwise nand with the current value, returning the previous value.
///
/// The stabilized version of this intrinsic is available on the
/// [`AtomicBool`] type via the `fetch_nand` method by passing
/// [`Ordering::Release`] as the `order`. For example, [`AtomicBool::fetch_nand`].
#[rustc_nounwind]
pub fn atomic_nand_release<T: Copy>(dst: *mut T, src: T) -> T;
/// Bitwise nand with the current value, returning the previous value.
///
/// The stabilized version of this intrinsic is available on the
/// [`AtomicBool`] type via the `fetch_nand` method by passing
/// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicBool::fetch_nand`].
#[rustc_nounwind]
pub fn atomic_nand_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
/// Bitwise nand with the current value, returning the previous value.
///
/// The stabilized version of this intrinsic is available on the
/// [`AtomicBool`] type via the `fetch_nand` method by passing
/// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicBool::fetch_nand`].
#[rustc_nounwind]
pub fn atomic_nand_relaxed<T: Copy>(dst: *mut T, src: T) -> T;
/// Bitwise or with the current value, returning the previous value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `fetch_or` method by passing
/// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicBool::fetch_or`].
#[rustc_nounwind]
pub fn atomic_or_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
/// Bitwise or with the current value, returning the previous value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `fetch_or` method by passing
/// [`Ordering::Acquire`] as the `order`. For example, [`AtomicBool::fetch_or`].
#[rustc_nounwind]
pub fn atomic_or_acquire<T: Copy>(dst: *mut T, src: T) -> T;
/// Bitwise or with the current value, returning the previous value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `fetch_or` method by passing
/// [`Ordering::Release`] as the `order`. For example, [`AtomicBool::fetch_or`].
#[rustc_nounwind]
pub fn atomic_or_release<T: Copy>(dst: *mut T, src: T) -> T;
/// Bitwise or with the current value, returning the previous value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `fetch_or` method by passing
/// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicBool::fetch_or`].
#[rustc_nounwind]
pub fn atomic_or_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
/// Bitwise or with the current value, returning the previous value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `fetch_or` method by passing
/// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicBool::fetch_or`].
#[rustc_nounwind]
pub fn atomic_or_relaxed<T: Copy>(dst: *mut T, src: T) -> T;
/// Bitwise xor with the current value, returning the previous value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `fetch_xor` method by passing
/// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicBool::fetch_xor`].
#[rustc_nounwind]
pub fn atomic_xor_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
/// Bitwise xor with the current value, returning the previous value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `fetch_xor` method by passing
/// [`Ordering::Acquire`] as the `order`. For example, [`AtomicBool::fetch_xor`].
#[rustc_nounwind]
pub fn atomic_xor_acquire<T: Copy>(dst: *mut T, src: T) -> T;
/// Bitwise xor with the current value, returning the previous value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `fetch_xor` method by passing
/// [`Ordering::Release`] as the `order`. For example, [`AtomicBool::fetch_xor`].
#[rustc_nounwind]
pub fn atomic_xor_release<T: Copy>(dst: *mut T, src: T) -> T;
/// Bitwise xor with the current value, returning the previous value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `fetch_xor` method by passing
/// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicBool::fetch_xor`].
#[rustc_nounwind]
pub fn atomic_xor_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
/// Bitwise xor with the current value, returning the previous value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] types via the `fetch_xor` method by passing
/// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicBool::fetch_xor`].
#[rustc_nounwind]
pub fn atomic_xor_relaxed<T: Copy>(dst: *mut T, src: T) -> T;
/// Maximum with the current value using a signed comparison.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] signed integer types via the `fetch_max` method by passing
/// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicI32::fetch_max`].
#[rustc_nounwind]
pub fn atomic_max_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
/// Maximum with the current value using a signed comparison.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] signed integer types via the `fetch_max` method by passing
/// [`Ordering::Acquire`] as the `order`. For example, [`AtomicI32::fetch_max`].
#[rustc_nounwind]
pub fn atomic_max_acquire<T: Copy>(dst: *mut T, src: T) -> T;
/// Maximum with the current value using a signed comparison.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] signed integer types via the `fetch_max` method by passing
/// [`Ordering::Release`] as the `order`. For example, [`AtomicI32::fetch_max`].
#[rustc_nounwind]
pub fn atomic_max_release<T: Copy>(dst: *mut T, src: T) -> T;
/// Maximum with the current value using a signed comparison.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] signed integer types via the `fetch_max` method by passing
/// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicI32::fetch_max`].
#[rustc_nounwind]
pub fn atomic_max_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
/// Maximum with the current value.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] signed integer types via the `fetch_max` method by passing
/// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicI32::fetch_max`].
#[rustc_nounwind]
pub fn atomic_max_relaxed<T: Copy>(dst: *mut T, src: T) -> T;
/// Minimum with the current value using a signed comparison.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] signed integer types via the `fetch_min` method by passing
/// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicI32::fetch_min`].
#[rustc_nounwind]
pub fn atomic_min_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
/// Minimum with the current value using a signed comparison.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] signed integer types via the `fetch_min` method by passing
/// [`Ordering::Acquire`] as the `order`. For example, [`AtomicI32::fetch_min`].
#[rustc_nounwind]
pub fn atomic_min_acquire<T: Copy>(dst: *mut T, src: T) -> T;
/// Minimum with the current value using a signed comparison.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] signed integer types via the `fetch_min` method by passing
/// [`Ordering::Release`] as the `order`. For example, [`AtomicI32::fetch_min`].
#[rustc_nounwind]
pub fn atomic_min_release<T: Copy>(dst: *mut T, src: T) -> T;
/// Minimum with the current value using a signed comparison.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] signed integer types via the `fetch_min` method by passing
/// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicI32::fetch_min`].
#[rustc_nounwind]
pub fn atomic_min_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
/// Minimum with the current value using a signed comparison.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] signed integer types via the `fetch_min` method by passing
/// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicI32::fetch_min`].
#[rustc_nounwind]
pub fn atomic_min_relaxed<T: Copy>(dst: *mut T, src: T) -> T;
/// Minimum with the current value using an unsigned comparison.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] unsigned integer types via the `fetch_min` method by passing
/// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicU32::fetch_min`].
#[rustc_nounwind]
pub fn atomic_umin_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
/// Minimum with the current value using an unsigned comparison.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] unsigned integer types via the `fetch_min` method by passing
/// [`Ordering::Acquire`] as the `order`. For example, [`AtomicU32::fetch_min`].
#[rustc_nounwind]
pub fn atomic_umin_acquire<T: Copy>(dst: *mut T, src: T) -> T;
/// Minimum with the current value using an unsigned comparison.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] unsigned integer types via the `fetch_min` method by passing
/// [`Ordering::Release`] as the `order`. For example, [`AtomicU32::fetch_min`].
#[rustc_nounwind]
pub fn atomic_umin_release<T: Copy>(dst: *mut T, src: T) -> T;
/// Minimum with the current value using an unsigned comparison.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] unsigned integer types via the `fetch_min` method by passing
/// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicU32::fetch_min`].
#[rustc_nounwind]
pub fn atomic_umin_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
/// Minimum with the current value using an unsigned comparison.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] unsigned integer types via the `fetch_min` method by passing
/// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicU32::fetch_min`].
#[rustc_nounwind]
pub fn atomic_umin_relaxed<T: Copy>(dst: *mut T, src: T) -> T;
/// Maximum with the current value using an unsigned comparison.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] unsigned integer types via the `fetch_max` method by passing
/// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicU32::fetch_max`].
#[rustc_nounwind]
pub fn atomic_umax_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
/// Maximum with the current value using an unsigned comparison.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] unsigned integer types via the `fetch_max` method by passing
/// [`Ordering::Acquire`] as the `order`. For example, [`AtomicU32::fetch_max`].
#[rustc_nounwind]
pub fn atomic_umax_acquire<T: Copy>(dst: *mut T, src: T) -> T;
/// Maximum with the current value using an unsigned comparison.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] unsigned integer types via the `fetch_max` method by passing
/// [`Ordering::Release`] as the `order`. For example, [`AtomicU32::fetch_max`].
#[rustc_nounwind]
pub fn atomic_umax_release<T: Copy>(dst: *mut T, src: T) -> T;
/// Maximum with the current value using an unsigned comparison.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] unsigned integer types via the `fetch_max` method by passing
/// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicU32::fetch_max`].
#[rustc_nounwind]
pub fn atomic_umax_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
/// Maximum with the current value using an unsigned comparison.
///
/// The stabilized version of this intrinsic is available on the
/// [`atomic`] unsigned integer types via the `fetch_max` method by passing
/// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicU32::fetch_max`].
#[rustc_nounwind]
pub fn atomic_umax_relaxed<T: Copy>(dst: *mut T, src: T) -> T;
/// An atomic fence.
///
/// The stabilized version of this intrinsic is available in
/// [`atomic::fence`] by passing [`Ordering::SeqCst`]
/// as the `order`.
#[rustc_nounwind]
pub fn atomic_fence_seqcst();
/// An atomic fence.
///
/// The stabilized version of this intrinsic is available in
/// [`atomic::fence`] by passing [`Ordering::Acquire`]
/// as the `order`.
#[rustc_nounwind]
pub fn atomic_fence_acquire();
/// An atomic fence.
///
/// The stabilized version of this intrinsic is available in
/// [`atomic::fence`] by passing [`Ordering::Release`]
/// as the `order`.
#[rustc_nounwind]
pub fn atomic_fence_release();
/// An atomic fence.
///
/// The stabilized version of this intrinsic is available in
/// [`atomic::fence`] by passing [`Ordering::AcqRel`]
/// as the `order`.
#[rustc_nounwind]
pub fn atomic_fence_acqrel();
/// A compiler-only memory barrier.
///
/// Memory accesses will never be reordered across this barrier by the
/// compiler, but no instructions will be emitted for it. This is
/// appropriate for operations on the same thread that may be preempted,
/// such as when interacting with signal handlers.
///
/// The stabilized version of this intrinsic is available in
/// [`atomic::compiler_fence`] by passing [`Ordering::SeqCst`]
/// as the `order`.
#[rustc_nounwind]
pub fn atomic_singlethreadfence_seqcst();
/// A compiler-only memory barrier.
///
/// Memory accesses will never be reordered across this barrier by the
/// compiler, but no instructions will be emitted for it. This is
/// appropriate for operations on the same thread that may be preempted,
/// such as when interacting with signal handlers.
///
/// The stabilized version of this intrinsic is available in
/// [`atomic::compiler_fence`] by passing [`Ordering::Acquire`]
/// as the `order`.
#[rustc_nounwind]
pub fn atomic_singlethreadfence_acquire();
/// A compiler-only memory barrier.
///
/// Memory accesses will never be reordered across this barrier by the
/// compiler, but no instructions will be emitted for it. This is
/// appropriate for operations on the same thread that may be preempted,
/// such as when interacting with signal handlers.
///
/// The stabilized version of this intrinsic is available in
/// [`atomic::compiler_fence`] by passing [`Ordering::Release`]
/// as the `order`.
#[rustc_nounwind]
pub fn atomic_singlethreadfence_release();
/// A compiler-only memory barrier.
///
/// Memory accesses will never be reordered across this barrier by the
/// compiler, but no instructions will be emitted for it. This is
/// appropriate for operations on the same thread that may be preempted,
/// such as when interacting with signal handlers.
///
/// The stabilized version of this intrinsic is available in
/// [`atomic::compiler_fence`] by passing [`Ordering::AcqRel`]
/// as the `order`.
#[rustc_nounwind]
pub fn atomic_singlethreadfence_acqrel();
/// The `prefetch` intrinsic is a hint to the code generator to insert a prefetch instruction
/// if supported; otherwise, it is a no-op.
/// Prefetches have no effect on the behavior of the program but can change its performance
/// characteristics.
///
/// The `locality` argument must be a constant integer and is a temporal locality specifier
/// ranging from (0) - no locality, to (3) - extremely local keep in cache.
///
/// This intrinsic does not have a stable counterpart.
#[rustc_nounwind]
pub fn prefetch_read_data<T>(data: *const T, locality: i32);
/// The `prefetch` intrinsic is a hint to the code generator to insert a prefetch instruction
/// if supported; otherwise, it is a no-op.
/// Prefetches have no effect on the behavior of the program but can change its performance
/// characteristics.
///
/// The `locality` argument must be a constant integer and is a temporal locality specifier
/// ranging from (0) - no locality, to (3) - extremely local keep in cache.
///
/// This intrinsic does not have a stable counterpart.
#[rustc_nounwind]
pub fn prefetch_write_data<T>(data: *const T, locality: i32);
/// The `prefetch` intrinsic is a hint to the code generator to insert a prefetch instruction
/// if supported; otherwise, it is a no-op.
/// Prefetches have no effect on the behavior of the program but can change its performance
/// characteristics.
///
/// The `locality` argument must be a constant integer and is a temporal locality specifier
/// ranging from (0) - no locality, to (3) - extremely local keep in cache.
///
/// This intrinsic does not have a stable counterpart.
#[rustc_nounwind]
pub fn prefetch_read_instruction<T>(data: *const T, locality: i32);
/// The `prefetch` intrinsic is a hint to the code generator to insert a prefetch instruction
/// if supported; otherwise, it is a no-op.
/// Prefetches have no effect on the behavior of the program but can change its performance
/// characteristics.
///
/// The `locality` argument must be a constant integer and is a temporal locality specifier
/// ranging from (0) - no locality, to (3) - extremely local keep in cache.
///
/// This intrinsic does not have a stable counterpart.
#[rustc_nounwind]
pub fn prefetch_write_instruction<T>(data: *const T, locality: i32);
/// Magic intrinsic that derives its meaning from attributes
/// attached to the function.
///
/// For example, dataflow uses this to inject static assertions so
/// that `rustc_peek(potentially_uninitialized)` would actually
/// double-check that dataflow did indeed compute that it is
/// uninitialized at that point in the control flow.
///
/// This intrinsic should not be used outside of the compiler.
#[rustc_safe_intrinsic]
#[rustc_nounwind]
pub fn rustc_peek<T>(_: T) -> T;
/// Aborts the execution of the process.
///
/// 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.
///
/// [`std::process::abort`](../../std/process/fn.abort.html) is to be preferred if possible,
/// as its behavior is more user-friendly and more stable.
///
/// The current implementation of `intrinsics::abort` is to invoke an invalid instruction,
/// on most platforms.
/// On Unix, the
/// process will probably terminate with a signal like `SIGABRT`, `SIGILL`, `SIGTRAP`, `SIGSEGV` or
/// `SIGBUS`. The precise behaviour is not guaranteed and not stable.
#[rustc_safe_intrinsic]
#[rustc_nounwind]
pub fn abort() -> !;
/// Informs the optimizer that this point in the code is not reachable,
/// enabling further optimizations.
///
/// N.B., this is very different from the `unreachable!()` macro: Unlike the
/// macro, which panics when it is executed, it is *undefined behavior* to
/// reach code marked with this function.
///
/// The stabilized version of this intrinsic is [`core::hint::unreachable_unchecked`].
#[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.
/// If the condition is false, the behavior is undefined.
///
/// No code is generated for this intrinsic, but the optimizer will try
/// to preserve it (and its condition) between passes, which may interfere
/// with optimization of surrounding code and reduce performance. It should
/// not be used if the invariant can be discovered by the optimizer on its
/// own, or if it does not enable any significant optimizations.
///
/// This intrinsic does not have a stable counterpart.
#[rustc_const_stable(feature = "const_assume", since = "1.77.0")]
#[rustc_nounwind]
#[unstable(feature = "core_intrinsics", issue = "none")]
#[rustc_intrinsic]
pub const unsafe fn assume(b: bool) {
if !b {
// SAFETY: the caller must guarantee the argument is never `false`
unsafe { unreachable() }
}
}
/// Hints to the compiler that branch condition is likely to be true.
/// Returns the value passed to it.
///
/// Any use other than with `if` statements will probably not have an effect.
///
/// 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.
///
/// This intrinsic does not have a stable counterpart.
#[rustc_const_unstable(feature = "const_likely", issue = "none")]
#[unstable(feature = "core_intrinsics", issue = "none")]
#[rustc_intrinsic]
#[rustc_nounwind]
#[miri::intrinsic_fallback_is_spec]
pub const fn likely(b: bool) -> bool {
b
}
/// Hints to the compiler that branch condition is likely to be false.
/// Returns the value passed to it.
///
/// Any use other than with `if` statements will probably not have an effect.
///
/// Note that, unlike most intrinsics, this is safe to call;
/// it does not require an `unsafe` block.