1 //! Compiler intrinsics.
3 //! The corresponding definitions are in <https://github.com/rust-lang/rust/blob/master/compiler/rustc_codegen_llvm/src/intrinsic.rs>.
4 //! The corresponding const implementations are in <https://github.com/rust-lang/rust/blob/master/compiler/rustc_const_eval/src/interpret/intrinsics.rs>.
8 //! Note: any changes to the constness of intrinsics should be discussed with the language team.
9 //! This includes changes in the stability of the constness.
11 //! In order to make an intrinsic usable at compile-time, one needs to copy the implementation
12 //! from <https://github.com/rust-lang/miri/blob/master/src/shims/intrinsics.rs> to
13 //! <https://github.com/rust-lang/rust/blob/master/compiler/rustc_const_eval/src/interpret/intrinsics.rs> and add a
14 //! `#[rustc_const_unstable(feature = "const_such_and_such", issue = "01234")]` to the intrinsic declaration.
16 //! If an intrinsic is supposed to be used from a `const fn` with a `rustc_const_stable` attribute,
17 //! the intrinsic's attribute must be `rustc_const_stable`, too. Such a change should not be done
18 //! without T-lang consultation, because it bakes a feature into the language that cannot be
19 //! replicated in user code without compiler support.
23 //! The volatile intrinsics provide operations intended to act on I/O
24 //! memory, which are guaranteed to not be reordered by the compiler
25 //! across other volatile intrinsics. See the LLVM documentation on
28 //! [volatile]: https://llvm.org/docs/LangRef.html#volatile-memory-accesses
32 //! The atomic intrinsics provide common atomic operations on machine
33 //! words, with multiple possible memory orderings. They obey the same
34 //! semantics as C++11. See the LLVM documentation on [[atomics]].
36 //! [atomics]: https://llvm.org/docs/Atomics.html
38 //! A quick refresher on memory ordering:
40 //! * Acquire - a barrier for acquiring a lock. Subsequent reads and writes
41 //! take place after the barrier.
42 //! * Release - a barrier for releasing a lock. Preceding reads and writes
43 //! take place before the barrier.
44 //! * Sequentially consistent - sequentially consistent operations are
45 //! guaranteed to happen in order. This is the standard mode for working
46 //! with atomic types and is equivalent to Java's `volatile`.
49 feature = "core_intrinsics",
50 reason = "intrinsics are unlikely to ever be stabilized, instead \
51 they should be used through stabilized interfaces \
52 in the rest of the standard library",
55 #![allow(missing_docs)]
57 use crate::marker::DiscriminantKind;
60 // These imports are used for simplifying intra-doc links
61 #[allow(unused_imports)]
62 #[cfg(all(target_has_atomic = "8", target_has_atomic = "32", target_has_atomic = "ptr"))]
63 use crate::sync::atomic::{self, AtomicBool, AtomicI32, AtomicIsize, AtomicU32, Ordering};
65 #[stable(feature = "drop_in_place", since = "1.8.0")]
66 #[rustc_allowed_through_unstable_modules]
67 #[deprecated(note = "no longer an intrinsic - use `ptr::drop_in_place` directly", since = "1.52.0")]
69 pub unsafe fn drop_in_place<T: ?Sized>(to_drop: *mut T) {
70 // SAFETY: see `ptr::drop_in_place`
71 unsafe { crate::ptr::drop_in_place(to_drop) }
74 extern "rust-intrinsic" {
75 // N.B., these intrinsics take raw pointers because they mutate aliased
76 // memory, which is not valid for either `&` or `&mut`.
78 /// Stores a value if the current value is the same as the `old` value.
80 /// The stabilized version of this intrinsic is available on the
81 /// [`atomic`] types via the `compare_exchange` method by passing
82 /// [`Ordering::Relaxed`] as both the success and failure parameters.
83 /// For example, [`AtomicBool::compare_exchange`].
84 pub fn atomic_cxchg_relaxed_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
85 /// Stores a value if the current value is the same as the `old` value.
87 /// The stabilized version of this intrinsic is available on the
88 /// [`atomic`] types via the `compare_exchange` method by passing
89 /// [`Ordering::Relaxed`] and [`Ordering::Acquire`] as the success and failure parameters.
90 /// For example, [`AtomicBool::compare_exchange`].
91 pub fn atomic_cxchg_relaxed_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
92 /// Stores a value if the current value is the same as the `old` value.
94 /// The stabilized version of this intrinsic is available on the
95 /// [`atomic`] types via the `compare_exchange` method by passing
96 /// [`Ordering::Relaxed`] and [`Ordering::SeqCst`] as the success and failure parameters.
97 /// For example, [`AtomicBool::compare_exchange`].
98 pub fn atomic_cxchg_relaxed_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
99 /// Stores a value if the current value is the same as the `old` value.
101 /// The stabilized version of this intrinsic is available on the
102 /// [`atomic`] types via the `compare_exchange` method by passing
103 /// [`Ordering::Acquire`] and [`Ordering::Relaxed`] as the success and failure parameters.
104 /// For example, [`AtomicBool::compare_exchange`].
105 pub fn atomic_cxchg_acquire_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
106 /// Stores a value if the current value is the same as the `old` value.
108 /// The stabilized version of this intrinsic is available on the
109 /// [`atomic`] types via the `compare_exchange` method by passing
110 /// [`Ordering::Acquire`] as both the success and failure parameters.
111 /// For example, [`AtomicBool::compare_exchange`].
112 pub fn atomic_cxchg_acquire_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
113 /// Stores a value if the current value is the same as the `old` value.
115 /// The stabilized version of this intrinsic is available on the
116 /// [`atomic`] types via the `compare_exchange` method by passing
117 /// [`Ordering::Acquire`] and [`Ordering::SeqCst`] as the success and failure parameters.
118 /// For example, [`AtomicBool::compare_exchange`].
119 pub fn atomic_cxchg_acquire_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
120 /// Stores a value if the current value is the same as the `old` value.
122 /// The stabilized version of this intrinsic is available on the
123 /// [`atomic`] types via the `compare_exchange` method by passing
124 /// [`Ordering::Release`] and [`Ordering::Relaxed`] as the success and failure parameters.
125 /// For example, [`AtomicBool::compare_exchange`].
126 pub fn atomic_cxchg_release_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
127 /// Stores a value if the current value is the same as the `old` value.
129 /// The stabilized version of this intrinsic is available on the
130 /// [`atomic`] types via the `compare_exchange` method by passing
131 /// [`Ordering::Release`] and [`Ordering::Acquire`] as the success and failure parameters.
132 /// For example, [`AtomicBool::compare_exchange`].
133 pub fn atomic_cxchg_release_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
134 /// Stores a value if the current value is the same as the `old` value.
136 /// The stabilized version of this intrinsic is available on the
137 /// [`atomic`] types via the `compare_exchange` method by passing
138 /// [`Ordering::Release`] and [`Ordering::SeqCst`] as the success and failure parameters.
139 /// For example, [`AtomicBool::compare_exchange`].
140 pub fn atomic_cxchg_release_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
141 /// Stores a value if the current value is the same as the `old` value.
143 /// The stabilized version of this intrinsic is available on the
144 /// [`atomic`] types via the `compare_exchange` method by passing
145 /// [`Ordering::AcqRel`] and [`Ordering::Relaxed`] as the success and failure parameters.
146 /// For example, [`AtomicBool::compare_exchange`].
147 pub fn atomic_cxchg_acqrel_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
148 /// Stores a value if the current value is the same as the `old` value.
150 /// The stabilized version of this intrinsic is available on the
151 /// [`atomic`] types via the `compare_exchange` method by passing
152 /// [`Ordering::AcqRel`] and [`Ordering::Acquire`] as the success and failure parameters.
153 /// For example, [`AtomicBool::compare_exchange`].
154 pub fn atomic_cxchg_acqrel_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
155 /// Stores a value if the current value is the same as the `old` value.
157 /// The stabilized version of this intrinsic is available on the
158 /// [`atomic`] types via the `compare_exchange` method by passing
159 /// [`Ordering::AcqRel`] and [`Ordering::SeqCst`] as the success and failure parameters.
160 /// For example, [`AtomicBool::compare_exchange`].
161 pub fn atomic_cxchg_acqrel_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
162 /// Stores a value if the current value is the same as the `old` value.
164 /// The stabilized version of this intrinsic is available on the
165 /// [`atomic`] types via the `compare_exchange` method by passing
166 /// [`Ordering::SeqCst`] and [`Ordering::Relaxed`] as the success and failure parameters.
167 /// For example, [`AtomicBool::compare_exchange`].
168 pub fn atomic_cxchg_seqcst_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
169 /// Stores a value if the current value is the same as the `old` value.
171 /// The stabilized version of this intrinsic is available on the
172 /// [`atomic`] types via the `compare_exchange` method by passing
173 /// [`Ordering::SeqCst`] and [`Ordering::Acquire`] as the success and failure parameters.
174 /// For example, [`AtomicBool::compare_exchange`].
175 pub fn atomic_cxchg_seqcst_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
176 /// Stores a value if the current value is the same as the `old` value.
178 /// The stabilized version of this intrinsic is available on the
179 /// [`atomic`] types via the `compare_exchange` method by passing
180 /// [`Ordering::SeqCst`] as both the success and failure parameters.
181 /// For example, [`AtomicBool::compare_exchange`].
182 pub fn atomic_cxchg_seqcst_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
184 /// Stores a value if the current value is the same as the `old` value.
186 /// The stabilized version of this intrinsic is available on the
187 /// [`atomic`] types via the `compare_exchange_weak` method by passing
188 /// [`Ordering::Relaxed`] as both the success and failure parameters.
189 /// For example, [`AtomicBool::compare_exchange_weak`].
190 pub fn atomic_cxchgweak_relaxed_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
191 /// Stores a value if the current value is the same as the `old` value.
193 /// The stabilized version of this intrinsic is available on the
194 /// [`atomic`] types via the `compare_exchange_weak` method by passing
195 /// [`Ordering::Relaxed`] and [`Ordering::Acquire`] as the success and failure parameters.
196 /// For example, [`AtomicBool::compare_exchange_weak`].
197 pub fn atomic_cxchgweak_relaxed_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
198 /// Stores a value if the current value is the same as the `old` value.
200 /// The stabilized version of this intrinsic is available on the
201 /// [`atomic`] types via the `compare_exchange_weak` method by passing
202 /// [`Ordering::Relaxed`] and [`Ordering::SeqCst`] as the success and failure parameters.
203 /// For example, [`AtomicBool::compare_exchange_weak`].
204 pub fn atomic_cxchgweak_relaxed_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
205 /// Stores a value if the current value is the same as the `old` value.
207 /// The stabilized version of this intrinsic is available on the
208 /// [`atomic`] types via the `compare_exchange_weak` method by passing
209 /// [`Ordering::Acquire`] and [`Ordering::Relaxed`] as the success and failure parameters.
210 /// For example, [`AtomicBool::compare_exchange_weak`].
211 pub fn atomic_cxchgweak_acquire_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
212 /// Stores a value if the current value is the same as the `old` value.
214 /// The stabilized version of this intrinsic is available on the
215 /// [`atomic`] types via the `compare_exchange_weak` method by passing
216 /// [`Ordering::Acquire`] as both the success and failure parameters.
217 /// For example, [`AtomicBool::compare_exchange_weak`].
218 pub fn atomic_cxchgweak_acquire_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
219 /// Stores a value if the current value is the same as the `old` value.
221 /// The stabilized version of this intrinsic is available on the
222 /// [`atomic`] types via the `compare_exchange_weak` method by passing
223 /// [`Ordering::Acquire`] and [`Ordering::SeqCst`] as the success and failure parameters.
224 /// For example, [`AtomicBool::compare_exchange_weak`].
225 pub fn atomic_cxchgweak_acquire_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
226 /// Stores a value if the current value is the same as the `old` value.
228 /// The stabilized version of this intrinsic is available on the
229 /// [`atomic`] types via the `compare_exchange_weak` method by passing
230 /// [`Ordering::Release`] and [`Ordering::Relaxed`] as the success and failure parameters.
231 /// For example, [`AtomicBool::compare_exchange_weak`].
232 pub fn atomic_cxchgweak_release_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
233 /// Stores a value if the current value is the same as the `old` value.
235 /// The stabilized version of this intrinsic is available on the
236 /// [`atomic`] types via the `compare_exchange_weak` method by passing
237 /// [`Ordering::Release`] and [`Ordering::Acquire`] as the success and failure parameters.
238 /// For example, [`AtomicBool::compare_exchange_weak`].
239 pub fn atomic_cxchgweak_release_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
240 /// Stores a value if the current value is the same as the `old` value.
242 /// The stabilized version of this intrinsic is available on the
243 /// [`atomic`] types via the `compare_exchange_weak` method by passing
244 /// [`Ordering::Release`] and [`Ordering::SeqCst`] as the success and failure parameters.
245 /// For example, [`AtomicBool::compare_exchange_weak`].
246 pub fn atomic_cxchgweak_release_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
247 /// Stores a value if the current value is the same as the `old` value.
249 /// The stabilized version of this intrinsic is available on the
250 /// [`atomic`] types via the `compare_exchange_weak` method by passing
251 /// [`Ordering::AcqRel`] and [`Ordering::Relaxed`] as the success and failure parameters.
252 /// For example, [`AtomicBool::compare_exchange_weak`].
253 pub fn atomic_cxchgweak_acqrel_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
254 /// Stores a value if the current value is the same as the `old` value.
256 /// The stabilized version of this intrinsic is available on the
257 /// [`atomic`] types via the `compare_exchange_weak` method by passing
258 /// [`Ordering::AcqRel`] and [`Ordering::Acquire`] as the success and failure parameters.
259 /// For example, [`AtomicBool::compare_exchange_weak`].
260 pub fn atomic_cxchgweak_acqrel_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
261 /// Stores a value if the current value is the same as the `old` value.
263 /// The stabilized version of this intrinsic is available on the
264 /// [`atomic`] types via the `compare_exchange_weak` method by passing
265 /// [`Ordering::AcqRel`] and [`Ordering::SeqCst`] as the success and failure parameters.
266 /// For example, [`AtomicBool::compare_exchange_weak`].
267 pub fn atomic_cxchgweak_acqrel_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
268 /// Stores a value if the current value is the same as the `old` value.
270 /// The stabilized version of this intrinsic is available on the
271 /// [`atomic`] types via the `compare_exchange_weak` method by passing
272 /// [`Ordering::SeqCst`] and [`Ordering::Relaxed`] as the success and failure parameters.
273 /// For example, [`AtomicBool::compare_exchange_weak`].
274 pub fn atomic_cxchgweak_seqcst_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
275 /// Stores a value if the current value is the same as the `old` value.
277 /// The stabilized version of this intrinsic is available on the
278 /// [`atomic`] types via the `compare_exchange_weak` method by passing
279 /// [`Ordering::SeqCst`] and [`Ordering::Acquire`] as the success and failure parameters.
280 /// For example, [`AtomicBool::compare_exchange_weak`].
281 pub fn atomic_cxchgweak_seqcst_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
282 /// Stores a value if the current value is the same as the `old` value.
284 /// The stabilized version of this intrinsic is available on the
285 /// [`atomic`] types via the `compare_exchange_weak` method by passing
286 /// [`Ordering::SeqCst`] as both the success and failure parameters.
287 /// For example, [`AtomicBool::compare_exchange_weak`].
288 pub fn atomic_cxchgweak_seqcst_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
290 /// Loads the current value of the pointer.
292 /// The stabilized version of this intrinsic is available on the
293 /// [`atomic`] types via the `load` method by passing
294 /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicBool::load`].
295 pub fn atomic_load_seqcst<T: Copy>(src: *const T) -> T;
296 /// Loads the current value of the pointer.
298 /// The stabilized version of this intrinsic is available on the
299 /// [`atomic`] types via the `load` method by passing
300 /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicBool::load`].
301 pub fn atomic_load_acquire<T: Copy>(src: *const T) -> T;
302 /// Loads the current value of the pointer.
304 /// The stabilized version of this intrinsic is available on the
305 /// [`atomic`] types via the `load` method by passing
306 /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicBool::load`].
307 pub fn atomic_load_relaxed<T: Copy>(src: *const T) -> T;
308 pub fn atomic_load_unordered<T: Copy>(src: *const T) -> T;
310 /// Stores the value at the specified memory location.
312 /// The stabilized version of this intrinsic is available on the
313 /// [`atomic`] types via the `store` method by passing
314 /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicBool::store`].
315 pub fn atomic_store_seqcst<T: Copy>(dst: *mut T, val: T);
316 /// Stores the value at the specified memory location.
318 /// The stabilized version of this intrinsic is available on the
319 /// [`atomic`] types via the `store` method by passing
320 /// [`Ordering::Release`] as the `order`. For example, [`AtomicBool::store`].
321 pub fn atomic_store_release<T: Copy>(dst: *mut T, val: T);
322 /// Stores the value at the specified memory location.
324 /// The stabilized version of this intrinsic is available on the
325 /// [`atomic`] types via the `store` method by passing
326 /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicBool::store`].
327 pub fn atomic_store_relaxed<T: Copy>(dst: *mut T, val: T);
328 pub fn atomic_store_unordered<T: Copy>(dst: *mut T, val: T);
330 /// Stores the value at the specified memory location, returning the old value.
332 /// The stabilized version of this intrinsic is available on the
333 /// [`atomic`] types via the `swap` method by passing
334 /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicBool::swap`].
335 pub fn atomic_xchg_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
336 /// Stores the value at the specified memory location, returning the old value.
338 /// The stabilized version of this intrinsic is available on the
339 /// [`atomic`] types via the `swap` method by passing
340 /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicBool::swap`].
341 pub fn atomic_xchg_acquire<T: Copy>(dst: *mut T, src: T) -> T;
342 /// Stores the value at the specified memory location, returning the old value.
344 /// The stabilized version of this intrinsic is available on the
345 /// [`atomic`] types via the `swap` method by passing
346 /// [`Ordering::Release`] as the `order`. For example, [`AtomicBool::swap`].
347 pub fn atomic_xchg_release<T: Copy>(dst: *mut T, src: T) -> T;
348 /// Stores the value at the specified memory location, returning the old value.
350 /// The stabilized version of this intrinsic is available on the
351 /// [`atomic`] types via the `swap` method by passing
352 /// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicBool::swap`].
353 pub fn atomic_xchg_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
354 /// Stores the value at the specified memory location, returning the old value.
356 /// The stabilized version of this intrinsic is available on the
357 /// [`atomic`] types via the `swap` method by passing
358 /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicBool::swap`].
359 pub fn atomic_xchg_relaxed<T: Copy>(dst: *mut T, src: T) -> T;
361 /// Adds to the current value, returning the previous value.
363 /// The stabilized version of this intrinsic is available on the
364 /// [`atomic`] types via the `fetch_add` method by passing
365 /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicIsize::fetch_add`].
366 pub fn atomic_xadd_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
367 /// Adds to the current value, returning the previous value.
369 /// The stabilized version of this intrinsic is available on the
370 /// [`atomic`] types via the `fetch_add` method by passing
371 /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicIsize::fetch_add`].
372 pub fn atomic_xadd_acquire<T: Copy>(dst: *mut T, src: T) -> T;
373 /// Adds to the current value, returning the previous value.
375 /// The stabilized version of this intrinsic is available on the
376 /// [`atomic`] types via the `fetch_add` method by passing
377 /// [`Ordering::Release`] as the `order`. For example, [`AtomicIsize::fetch_add`].
378 pub fn atomic_xadd_release<T: Copy>(dst: *mut T, src: T) -> T;
379 /// Adds to the current value, returning the previous value.
381 /// The stabilized version of this intrinsic is available on the
382 /// [`atomic`] types via the `fetch_add` method by passing
383 /// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicIsize::fetch_add`].
384 pub fn atomic_xadd_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
385 /// Adds to the current value, returning the previous value.
387 /// The stabilized version of this intrinsic is available on the
388 /// [`atomic`] types via the `fetch_add` method by passing
389 /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicIsize::fetch_add`].
390 pub fn atomic_xadd_relaxed<T: Copy>(dst: *mut T, src: T) -> T;
392 /// Subtract from the current value, returning the previous value.
394 /// The stabilized version of this intrinsic is available on the
395 /// [`atomic`] types via the `fetch_sub` method by passing
396 /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicIsize::fetch_sub`].
397 pub fn atomic_xsub_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
398 /// Subtract from the current value, returning the previous value.
400 /// The stabilized version of this intrinsic is available on the
401 /// [`atomic`] types via the `fetch_sub` method by passing
402 /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicIsize::fetch_sub`].
403 pub fn atomic_xsub_acquire<T: Copy>(dst: *mut T, src: T) -> T;
404 /// Subtract from the current value, returning the previous value.
406 /// The stabilized version of this intrinsic is available on the
407 /// [`atomic`] types via the `fetch_sub` method by passing
408 /// [`Ordering::Release`] as the `order`. For example, [`AtomicIsize::fetch_sub`].
409 pub fn atomic_xsub_release<T: Copy>(dst: *mut T, src: T) -> T;
410 /// Subtract from the current value, returning the previous value.
412 /// The stabilized version of this intrinsic is available on the
413 /// [`atomic`] types via the `fetch_sub` method by passing
414 /// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicIsize::fetch_sub`].
415 pub fn atomic_xsub_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
416 /// Subtract from the current value, returning the previous value.
418 /// The stabilized version of this intrinsic is available on the
419 /// [`atomic`] types via the `fetch_sub` method by passing
420 /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicIsize::fetch_sub`].
421 pub fn atomic_xsub_relaxed<T: Copy>(dst: *mut T, src: T) -> T;
423 /// Bitwise and with the current value, returning the previous value.
425 /// The stabilized version of this intrinsic is available on the
426 /// [`atomic`] types via the `fetch_and` method by passing
427 /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicBool::fetch_and`].
428 pub fn atomic_and_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
429 /// Bitwise and with the current value, returning the previous value.
431 /// The stabilized version of this intrinsic is available on the
432 /// [`atomic`] types via the `fetch_and` method by passing
433 /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicBool::fetch_and`].
434 pub fn atomic_and_acquire<T: Copy>(dst: *mut T, src: T) -> T;
435 /// Bitwise and with the current value, returning the previous value.
437 /// The stabilized version of this intrinsic is available on the
438 /// [`atomic`] types via the `fetch_and` method by passing
439 /// [`Ordering::Release`] as the `order`. For example, [`AtomicBool::fetch_and`].
440 pub fn atomic_and_release<T: Copy>(dst: *mut T, src: T) -> T;
441 /// Bitwise and with the current value, returning the previous value.
443 /// The stabilized version of this intrinsic is available on the
444 /// [`atomic`] types via the `fetch_and` method by passing
445 /// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicBool::fetch_and`].
446 pub fn atomic_and_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
447 /// Bitwise and with the current value, returning the previous value.
449 /// The stabilized version of this intrinsic is available on the
450 /// [`atomic`] types via the `fetch_and` method by passing
451 /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicBool::fetch_and`].
452 pub fn atomic_and_relaxed<T: Copy>(dst: *mut T, src: T) -> T;
454 /// Bitwise nand with the current value, returning the previous value.
456 /// The stabilized version of this intrinsic is available on the
457 /// [`AtomicBool`] type via the `fetch_nand` method by passing
458 /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicBool::fetch_nand`].
459 pub fn atomic_nand_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
460 /// Bitwise nand with the current value, returning the previous value.
462 /// The stabilized version of this intrinsic is available on the
463 /// [`AtomicBool`] type via the `fetch_nand` method by passing
464 /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicBool::fetch_nand`].
465 pub fn atomic_nand_acquire<T: Copy>(dst: *mut T, src: T) -> T;
466 /// Bitwise nand with the current value, returning the previous value.
468 /// The stabilized version of this intrinsic is available on the
469 /// [`AtomicBool`] type via the `fetch_nand` method by passing
470 /// [`Ordering::Release`] as the `order`. For example, [`AtomicBool::fetch_nand`].
471 pub fn atomic_nand_release<T: Copy>(dst: *mut T, src: T) -> T;
472 /// Bitwise nand with the current value, returning the previous value.
474 /// The stabilized version of this intrinsic is available on the
475 /// [`AtomicBool`] type via the `fetch_nand` method by passing
476 /// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicBool::fetch_nand`].
477 pub fn atomic_nand_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
478 /// Bitwise nand with the current value, returning the previous value.
480 /// The stabilized version of this intrinsic is available on the
481 /// [`AtomicBool`] type via the `fetch_nand` method by passing
482 /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicBool::fetch_nand`].
483 pub fn atomic_nand_relaxed<T: Copy>(dst: *mut T, src: T) -> T;
485 /// Bitwise or with the current value, returning the previous value.
487 /// The stabilized version of this intrinsic is available on the
488 /// [`atomic`] types via the `fetch_or` method by passing
489 /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicBool::fetch_or`].
490 pub fn atomic_or_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
491 /// Bitwise or with the current value, returning the previous value.
493 /// The stabilized version of this intrinsic is available on the
494 /// [`atomic`] types via the `fetch_or` method by passing
495 /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicBool::fetch_or`].
496 pub fn atomic_or_acquire<T: Copy>(dst: *mut T, src: T) -> T;
497 /// Bitwise or with the current value, returning the previous value.
499 /// The stabilized version of this intrinsic is available on the
500 /// [`atomic`] types via the `fetch_or` method by passing
501 /// [`Ordering::Release`] as the `order`. For example, [`AtomicBool::fetch_or`].
502 pub fn atomic_or_release<T: Copy>(dst: *mut T, src: T) -> T;
503 /// Bitwise or with the current value, returning the previous value.
505 /// The stabilized version of this intrinsic is available on the
506 /// [`atomic`] types via the `fetch_or` method by passing
507 /// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicBool::fetch_or`].
508 pub fn atomic_or_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
509 /// Bitwise or with the current value, returning the previous value.
511 /// The stabilized version of this intrinsic is available on the
512 /// [`atomic`] types via the `fetch_or` method by passing
513 /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicBool::fetch_or`].
514 pub fn atomic_or_relaxed<T: Copy>(dst: *mut T, src: T) -> T;
516 /// Bitwise xor with the current value, returning the previous value.
518 /// The stabilized version of this intrinsic is available on the
519 /// [`atomic`] types via the `fetch_xor` method by passing
520 /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicBool::fetch_xor`].
521 pub fn atomic_xor_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
522 /// Bitwise xor with the current value, returning the previous value.
524 /// The stabilized version of this intrinsic is available on the
525 /// [`atomic`] types via the `fetch_xor` method by passing
526 /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicBool::fetch_xor`].
527 pub fn atomic_xor_acquire<T: Copy>(dst: *mut T, src: T) -> T;
528 /// Bitwise xor with the current value, returning the previous value.
530 /// The stabilized version of this intrinsic is available on the
531 /// [`atomic`] types via the `fetch_xor` method by passing
532 /// [`Ordering::Release`] as the `order`. For example, [`AtomicBool::fetch_xor`].
533 pub fn atomic_xor_release<T: Copy>(dst: *mut T, src: T) -> T;
534 /// Bitwise xor with the current value, returning the previous value.
536 /// The stabilized version of this intrinsic is available on the
537 /// [`atomic`] types via the `fetch_xor` method by passing
538 /// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicBool::fetch_xor`].
539 pub fn atomic_xor_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
540 /// Bitwise xor with the current value, returning the previous value.
542 /// The stabilized version of this intrinsic is available on the
543 /// [`atomic`] types via the `fetch_xor` method by passing
544 /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicBool::fetch_xor`].
545 pub fn atomic_xor_relaxed<T: Copy>(dst: *mut T, src: T) -> T;
547 /// Maximum with the current value using a signed comparison.
549 /// The stabilized version of this intrinsic is available on the
550 /// [`atomic`] signed integer types via the `fetch_max` method by passing
551 /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicI32::fetch_max`].
552 pub fn atomic_max_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
553 /// Maximum with the current value using a signed comparison.
555 /// The stabilized version of this intrinsic is available on the
556 /// [`atomic`] signed integer types via the `fetch_max` method by passing
557 /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicI32::fetch_max`].
558 pub fn atomic_max_acquire<T: Copy>(dst: *mut T, src: T) -> T;
559 /// Maximum with the current value using a signed comparison.
561 /// The stabilized version of this intrinsic is available on the
562 /// [`atomic`] signed integer types via the `fetch_max` method by passing
563 /// [`Ordering::Release`] as the `order`. For example, [`AtomicI32::fetch_max`].
564 pub fn atomic_max_release<T: Copy>(dst: *mut T, src: T) -> T;
565 /// Maximum with the current value using a signed comparison.
567 /// The stabilized version of this intrinsic is available on the
568 /// [`atomic`] signed integer types via the `fetch_max` method by passing
569 /// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicI32::fetch_max`].
570 pub fn atomic_max_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
571 /// Maximum with the current value.
573 /// The stabilized version of this intrinsic is available on the
574 /// [`atomic`] signed integer types via the `fetch_max` method by passing
575 /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicI32::fetch_max`].
576 pub fn atomic_max_relaxed<T: Copy>(dst: *mut T, src: T) -> T;
578 /// Minimum with the current value using a signed comparison.
580 /// The stabilized version of this intrinsic is available on the
581 /// [`atomic`] signed integer types via the `fetch_min` method by passing
582 /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicI32::fetch_min`].
583 pub fn atomic_min_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
584 /// Minimum with the current value using a signed comparison.
586 /// The stabilized version of this intrinsic is available on the
587 /// [`atomic`] signed integer types via the `fetch_min` method by passing
588 /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicI32::fetch_min`].
589 pub fn atomic_min_acquire<T: Copy>(dst: *mut T, src: T) -> T;
590 /// Minimum with the current value using a signed comparison.
592 /// The stabilized version of this intrinsic is available on the
593 /// [`atomic`] signed integer types via the `fetch_min` method by passing
594 /// [`Ordering::Release`] as the `order`. For example, [`AtomicI32::fetch_min`].
595 pub fn atomic_min_release<T: Copy>(dst: *mut T, src: T) -> T;
596 /// Minimum with the current value using a signed comparison.
598 /// The stabilized version of this intrinsic is available on the
599 /// [`atomic`] signed integer types via the `fetch_min` method by passing
600 /// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicI32::fetch_min`].
601 pub fn atomic_min_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
602 /// Minimum with the current value using a signed comparison.
604 /// The stabilized version of this intrinsic is available on the
605 /// [`atomic`] signed integer types via the `fetch_min` method by passing
606 /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicI32::fetch_min`].
607 pub fn atomic_min_relaxed<T: Copy>(dst: *mut T, src: T) -> T;
609 /// Minimum with the current value using an unsigned comparison.
611 /// The stabilized version of this intrinsic is available on the
612 /// [`atomic`] unsigned integer types via the `fetch_min` method by passing
613 /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicU32::fetch_min`].
614 pub fn atomic_umin_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
615 /// Minimum with the current value using an unsigned comparison.
617 /// The stabilized version of this intrinsic is available on the
618 /// [`atomic`] unsigned integer types via the `fetch_min` method by passing
619 /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicU32::fetch_min`].
620 pub fn atomic_umin_acquire<T: Copy>(dst: *mut T, src: T) -> T;
621 /// Minimum with the current value using an unsigned comparison.
623 /// The stabilized version of this intrinsic is available on the
624 /// [`atomic`] unsigned integer types via the `fetch_min` method by passing
625 /// [`Ordering::Release`] as the `order`. For example, [`AtomicU32::fetch_min`].
626 pub fn atomic_umin_release<T: Copy>(dst: *mut T, src: T) -> T;
627 /// Minimum with the current value using an unsigned comparison.
629 /// The stabilized version of this intrinsic is available on the
630 /// [`atomic`] unsigned integer types via the `fetch_min` method by passing
631 /// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicU32::fetch_min`].
632 pub fn atomic_umin_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
633 /// Minimum with the current value using an unsigned comparison.
635 /// The stabilized version of this intrinsic is available on the
636 /// [`atomic`] unsigned integer types via the `fetch_min` method by passing
637 /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicU32::fetch_min`].
638 pub fn atomic_umin_relaxed<T: Copy>(dst: *mut T, src: T) -> T;
640 /// Maximum with the current value using an unsigned comparison.
642 /// The stabilized version of this intrinsic is available on the
643 /// [`atomic`] unsigned integer types via the `fetch_max` method by passing
644 /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicU32::fetch_max`].
645 pub fn atomic_umax_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
646 /// Maximum with the current value using an unsigned comparison.
648 /// The stabilized version of this intrinsic is available on the
649 /// [`atomic`] unsigned integer types via the `fetch_max` method by passing
650 /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicU32::fetch_max`].
651 pub fn atomic_umax_acquire<T: Copy>(dst: *mut T, src: T) -> T;
652 /// Maximum with the current value using an unsigned comparison.
654 /// The stabilized version of this intrinsic is available on the
655 /// [`atomic`] unsigned integer types via the `fetch_max` method by passing
656 /// [`Ordering::Release`] as the `order`. For example, [`AtomicU32::fetch_max`].
657 pub fn atomic_umax_release<T: Copy>(dst: *mut T, src: T) -> T;
658 /// Maximum with the current value using an unsigned comparison.
660 /// The stabilized version of this intrinsic is available on the
661 /// [`atomic`] unsigned integer types via the `fetch_max` method by passing
662 /// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicU32::fetch_max`].
663 pub fn atomic_umax_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
664 /// Maximum with the current value using an unsigned comparison.
666 /// The stabilized version of this intrinsic is available on the
667 /// [`atomic`] unsigned integer types via the `fetch_max` method by passing
668 /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicU32::fetch_max`].
669 pub fn atomic_umax_relaxed<T: Copy>(dst: *mut T, src: T) -> T;
673 /// The stabilized version of this intrinsic is available in
674 /// [`atomic::fence`] by passing [`Ordering::SeqCst`]
676 pub fn atomic_fence_seqcst();
679 /// The stabilized version of this intrinsic is available in
680 /// [`atomic::fence`] by passing [`Ordering::Acquire`]
682 pub fn atomic_fence_acquire();
685 /// The stabilized version of this intrinsic is available in
686 /// [`atomic::fence`] by passing [`Ordering::Release`]
688 pub fn atomic_fence_release();
691 /// The stabilized version of this intrinsic is available in
692 /// [`atomic::fence`] by passing [`Ordering::AcqRel`]
694 pub fn atomic_fence_acqrel();
696 /// A compiler-only memory barrier.
698 /// Memory accesses will never be reordered across this barrier by the
699 /// compiler, but no instructions will be emitted for it. This is
700 /// appropriate for operations on the same thread that may be preempted,
701 /// such as when interacting with signal handlers.
703 /// The stabilized version of this intrinsic is available in
704 /// [`atomic::compiler_fence`] by passing [`Ordering::SeqCst`]
706 pub fn atomic_singlethreadfence_seqcst();
707 /// A compiler-only memory barrier.
709 /// Memory accesses will never be reordered across this barrier by the
710 /// compiler, but no instructions will be emitted for it. This is
711 /// appropriate for operations on the same thread that may be preempted,
712 /// such as when interacting with signal handlers.
714 /// The stabilized version of this intrinsic is available in
715 /// [`atomic::compiler_fence`] by passing [`Ordering::Acquire`]
717 pub fn atomic_singlethreadfence_acquire();
718 /// A compiler-only memory barrier.
720 /// Memory accesses will never be reordered across this barrier by the
721 /// compiler, but no instructions will be emitted for it. This is
722 /// appropriate for operations on the same thread that may be preempted,
723 /// such as when interacting with signal handlers.
725 /// The stabilized version of this intrinsic is available in
726 /// [`atomic::compiler_fence`] by passing [`Ordering::Release`]
728 pub fn atomic_singlethreadfence_release();
729 /// A compiler-only memory barrier.
731 /// Memory accesses will never be reordered across this barrier by the
732 /// compiler, but no instructions will be emitted for it. This is
733 /// appropriate for operations on the same thread that may be preempted,
734 /// such as when interacting with signal handlers.
736 /// The stabilized version of this intrinsic is available in
737 /// [`atomic::compiler_fence`] by passing [`Ordering::AcqRel`]
739 pub fn atomic_singlethreadfence_acqrel();
741 /// The `prefetch` intrinsic is a hint to the code generator to insert a prefetch instruction
742 /// if supported; otherwise, it is a no-op.
743 /// Prefetches have no effect on the behavior of the program but can change its performance
746 /// The `locality` argument must be a constant integer and is a temporal locality specifier
747 /// ranging from (0) - no locality, to (3) - extremely local keep in cache.
749 /// This intrinsic does not have a stable counterpart.
750 pub fn prefetch_read_data<T>(data: *const T, locality: i32);
751 /// The `prefetch` intrinsic is a hint to the code generator to insert a prefetch instruction
752 /// if supported; otherwise, it is a no-op.
753 /// Prefetches have no effect on the behavior of the program but can change its performance
756 /// The `locality` argument must be a constant integer and is a temporal locality specifier
757 /// ranging from (0) - no locality, to (3) - extremely local keep in cache.
759 /// This intrinsic does not have a stable counterpart.
760 pub fn prefetch_write_data<T>(data: *const T, locality: i32);
761 /// The `prefetch` intrinsic is a hint to the code generator to insert a prefetch instruction
762 /// if supported; otherwise, it is a no-op.
763 /// Prefetches have no effect on the behavior of the program but can change its performance
766 /// The `locality` argument must be a constant integer and is a temporal locality specifier
767 /// ranging from (0) - no locality, to (3) - extremely local keep in cache.
769 /// This intrinsic does not have a stable counterpart.
770 pub fn prefetch_read_instruction<T>(data: *const T, locality: i32);
771 /// The `prefetch` intrinsic is a hint to the code generator to insert a prefetch instruction
772 /// if supported; otherwise, it is a no-op.
773 /// Prefetches have no effect on the behavior of the program but can change its performance
776 /// The `locality` argument must be a constant integer and is a temporal locality specifier
777 /// ranging from (0) - no locality, to (3) - extremely local keep in cache.
779 /// This intrinsic does not have a stable counterpart.
780 pub fn prefetch_write_instruction<T>(data: *const T, locality: i32);
782 /// Magic intrinsic that derives its meaning from attributes
783 /// attached to the function.
785 /// For example, dataflow uses this to inject static assertions so
786 /// that `rustc_peek(potentially_uninitialized)` would actually
787 /// double-check that dataflow did indeed compute that it is
788 /// uninitialized at that point in the control flow.
790 /// This intrinsic should not be used outside of the compiler.
791 pub fn rustc_peek<T>(_: T) -> T;
793 /// Aborts the execution of the process.
795 /// Note that, unlike most intrinsics, this is safe to call;
796 /// it does not require an `unsafe` block.
797 /// Therefore, implementations must not require the user to uphold
798 /// any safety invariants.
800 /// [`std::process::abort`](../../std/process/fn.abort.html) is to be preferred if possible,
801 /// as its behavior is more user-friendly and more stable.
803 /// The current implementation of `intrinsics::abort` is to invoke an invalid instruction,
804 /// on most platforms.
806 /// process will probably terminate with a signal like `SIGABRT`, `SIGILL`, `SIGTRAP`, `SIGSEGV` or
807 /// `SIGBUS`. The precise behaviour is not guaranteed and not stable.
810 /// Informs the optimizer that this point in the code is not reachable,
811 /// enabling further optimizations.
813 /// N.B., this is very different from the `unreachable!()` macro: Unlike the
814 /// macro, which panics when it is executed, it is *undefined behavior* to
815 /// reach code marked with this function.
817 /// The stabilized version of this intrinsic is [`core::hint::unreachable_unchecked`].
818 #[rustc_const_stable(feature = "const_unreachable_unchecked", since = "1.57.0")]
819 pub fn unreachable() -> !;
821 /// Informs the optimizer that a condition is always true.
822 /// If the condition is false, the behavior is undefined.
824 /// No code is generated for this intrinsic, but the optimizer will try
825 /// to preserve it (and its condition) between passes, which may interfere
826 /// with optimization of surrounding code and reduce performance. It should
827 /// not be used if the invariant can be discovered by the optimizer on its
828 /// own, or if it does not enable any significant optimizations.
830 /// This intrinsic does not have a stable counterpart.
831 #[rustc_const_unstable(feature = "const_assume", issue = "76972")]
832 pub fn assume(b: bool);
834 /// Hints to the compiler that branch condition is likely to be true.
835 /// Returns the value passed to it.
837 /// Any use other than with `if` statements will probably not have an effect.
839 /// Note that, unlike most intrinsics, this is safe to call;
840 /// it does not require an `unsafe` block.
841 /// Therefore, implementations must not require the user to uphold
842 /// any safety invariants.
844 /// This intrinsic does not have a stable counterpart.
845 #[rustc_const_unstable(feature = "const_likely", issue = "none")]
846 pub fn likely(b: bool) -> bool;
848 /// Hints to the compiler that branch condition is likely to be false.
849 /// Returns the value passed to it.
851 /// Any use other than with `if` statements will probably not have an effect.
853 /// Note that, unlike most intrinsics, this is safe to call;
854 /// it does not require an `unsafe` block.
855 /// Therefore, implementations must not require the user to uphold
856 /// any safety invariants.
858 /// This intrinsic does not have a stable counterpart.
859 #[rustc_const_unstable(feature = "const_likely", issue = "none")]
860 pub fn unlikely(b: bool) -> bool;
862 /// Executes a breakpoint trap, for inspection by a debugger.
864 /// This intrinsic does not have a stable counterpart.
867 /// The size of a type in bytes.
869 /// Note that, unlike most intrinsics, this is safe to call;
870 /// it does not require an `unsafe` block.
871 /// Therefore, implementations must not require the user to uphold
872 /// any safety invariants.
874 /// More specifically, this is the offset in bytes between successive
875 /// items of the same type, including alignment padding.
877 /// The stabilized version of this intrinsic is [`core::mem::size_of`].
878 #[rustc_const_stable(feature = "const_size_of", since = "1.40.0")]
879 pub fn size_of<T>() -> usize;
881 /// The minimum alignment of a type.
883 /// Note that, unlike most intrinsics, this is safe to call;
884 /// it does not require an `unsafe` block.
885 /// Therefore, implementations must not require the user to uphold
886 /// any safety invariants.
888 /// The stabilized version of this intrinsic is [`core::mem::align_of`].
889 #[rustc_const_stable(feature = "const_min_align_of", since = "1.40.0")]
890 pub fn min_align_of<T>() -> usize;
891 /// The preferred alignment of a type.
893 /// This intrinsic does not have a stable counterpart.
894 /// It's "tracking issue" is [#91971](https://github.com/rust-lang/rust/issues/91971).
895 #[rustc_const_unstable(feature = "const_pref_align_of", issue = "91971")]
896 pub fn pref_align_of<T>() -> usize;
898 /// The size of the referenced value in bytes.
900 /// The stabilized version of this intrinsic is [`mem::size_of_val`].
901 #[rustc_const_unstable(feature = "const_size_of_val", issue = "46571")]
902 pub fn size_of_val<T: ?Sized>(_: *const T) -> usize;
903 /// The required alignment of the referenced value.
905 /// The stabilized version of this intrinsic is [`core::mem::align_of_val`].
906 #[rustc_const_unstable(feature = "const_align_of_val", issue = "46571")]
907 pub fn min_align_of_val<T: ?Sized>(_: *const T) -> usize;
909 /// Gets a static string slice containing the name of a type.
911 /// Note that, unlike most intrinsics, this is safe to call;
912 /// it does not require an `unsafe` block.
913 /// Therefore, implementations must not require the user to uphold
914 /// any safety invariants.
916 /// The stabilized version of this intrinsic is [`core::any::type_name`].
917 #[rustc_const_unstable(feature = "const_type_name", issue = "63084")]
918 pub fn type_name<T: ?Sized>() -> &'static str;
920 /// Gets an identifier which is globally unique to the specified type. This
921 /// function will return the same value for a type regardless of whichever
922 /// crate it is invoked in.
924 /// Note that, unlike most intrinsics, this is safe to call;
925 /// it does not require an `unsafe` block.
926 /// Therefore, implementations must not require the user to uphold
927 /// any safety invariants.
929 /// The stabilized version of this intrinsic is [`core::any::TypeId::of`].
930 #[rustc_const_unstable(feature = "const_type_id", issue = "77125")]
931 pub fn type_id<T: ?Sized + 'static>() -> u64;
933 /// A guard for unsafe functions that cannot ever be executed if `T` is uninhabited:
934 /// This will statically either panic, or do nothing.
936 /// This intrinsic does not have a stable counterpart.
937 #[rustc_const_stable(feature = "const_assert_type", since = "1.59.0")]
938 pub fn assert_inhabited<T>();
940 /// A guard for unsafe functions that cannot ever be executed if `T` does not permit
941 /// zero-initialization: This will statically either panic, or do nothing.
943 /// This intrinsic does not have a stable counterpart.
944 #[rustc_const_unstable(feature = "const_assert_type2", issue = "none")]
945 pub fn assert_zero_valid<T>();
947 /// A guard for unsafe functions that cannot ever be executed if `T` has invalid
948 /// bit patterns: This will statically either panic, or do nothing.
950 /// This intrinsic does not have a stable counterpart.
951 #[rustc_const_unstable(feature = "const_assert_type2", issue = "none")]
952 pub fn assert_uninit_valid<T>();
954 /// Gets a reference to a static `Location` indicating where it was called.
956 /// Note that, unlike most intrinsics, this is safe to call;
957 /// it does not require an `unsafe` block.
958 /// Therefore, implementations must not require the user to uphold
959 /// any safety invariants.
961 /// Consider using [`core::panic::Location::caller`] instead.
962 #[rustc_const_unstable(feature = "const_caller_location", issue = "76156")]
963 pub fn caller_location() -> &'static crate::panic::Location<'static>;
965 /// Moves a value out of scope without running drop glue.
967 /// This exists solely for [`mem::forget_unsized`]; normal `forget` uses
968 /// `ManuallyDrop` instead.
970 /// Note that, unlike most intrinsics, this is safe to call;
971 /// it does not require an `unsafe` block.
972 /// Therefore, implementations must not require the user to uphold
973 /// any safety invariants.
974 #[rustc_const_unstable(feature = "const_intrinsic_forget", issue = "none")]
975 pub fn forget<T: ?Sized>(_: T);
977 /// Reinterprets the bits of a value of one type as another type.
979 /// Both types must have the same size. Compilation will fail if this is not guaranteed.
981 /// `transmute` is semantically equivalent to a bitwise move of one type
982 /// into another. It copies the bits from the source value into the
983 /// destination value, then forgets the original. Note that source and destination
984 /// are passed by-value, which means if `T` or `U` contain padding, that padding
985 /// is *not* guaranteed to be preserved by `transmute`.
987 /// Both the argument and the result must be [valid](../../nomicon/what-unsafe-does.html) at
988 /// their given type. Violating this condition leads to [undefined behavior][ub]. The compiler
989 /// will generate code *assuming that you, the programmer, ensure that there will never be
990 /// undefined behavior*. It is therefore your responsibility to guarantee that every value
991 /// passed to `transmute` is valid at both types `T` and `U`. Failing to uphold this condition
992 /// may lead to unexpected and unstable compilation results. This makes `transmute` **incredibly
993 /// unsafe**. `transmute` should be the absolute last resort.
995 /// Transmuting pointers to integers in a `const` context is [undefined behavior][ub].
996 /// Any attempt to use the resulting value for integer operations will abort const-evaluation.
997 /// (And even outside `const`, such transmutation is touching on many unspecified aspects of the
998 /// Rust memory model and should be avoided. See below for alternatives.)
1000 /// Because `transmute` is a by-value operation, alignment of the *transmuted values
1001 /// themselves* is not a concern. As with any other function, the compiler already ensures
1002 /// both `T` and `U` are properly aligned. However, when transmuting values that *point
1003 /// elsewhere* (such as pointers, references, boxes…), the caller has to ensure proper
1004 /// alignment of the pointed-to values.
1006 /// The [nomicon](../../nomicon/transmutes.html) has additional documentation.
1008 /// [ub]: ../../reference/behavior-considered-undefined.html
1012 /// There are a few things that `transmute` is really useful for.
1014 /// Turning a pointer into a function pointer. This is *not* portable to
1015 /// machines where function pointers and data pointers have different sizes.
1018 /// fn foo() -> i32 {
1021 /// // Crucially, we `as`-cast to a raw pointer before `transmute`ing to a function pointer.
1022 /// // This avoids an integer-to-pointer `transmute`, which can be problematic.
1023 /// // Transmuting between raw pointers and function pointers (i.e., two pointer types) is fine.
1024 /// let pointer = foo as *const ();
1025 /// let function = unsafe {
1026 /// std::mem::transmute::<*const (), fn() -> i32>(pointer)
1028 /// assert_eq!(function(), 0);
1031 /// Extending a lifetime, or shortening an invariant lifetime. This is
1032 /// advanced, very unsafe Rust!
1035 /// struct R<'a>(&'a i32);
1036 /// unsafe fn extend_lifetime<'b>(r: R<'b>) -> R<'static> {
1037 /// std::mem::transmute::<R<'b>, R<'static>>(r)
1040 /// unsafe fn shorten_invariant_lifetime<'b, 'c>(r: &'b mut R<'static>)
1041 /// -> &'b mut R<'c> {
1042 /// std::mem::transmute::<&'b mut R<'static>, &'b mut R<'c>>(r)
1048 /// Don't despair: many uses of `transmute` can be achieved through other means.
1049 /// Below are common applications of `transmute` which can be replaced with safer
1052 /// Turning raw bytes (`&[u8]`) into `u32`, `f64`, etc.:
1055 /// let raw_bytes = [0x78, 0x56, 0x34, 0x12];
1057 /// let num = unsafe {
1058 /// std::mem::transmute::<[u8; 4], u32>(raw_bytes)
1061 /// // use `u32::from_ne_bytes` instead
1062 /// let num = u32::from_ne_bytes(raw_bytes);
1063 /// // or use `u32::from_le_bytes` or `u32::from_be_bytes` to specify the endianness
1064 /// let num = u32::from_le_bytes(raw_bytes);
1065 /// assert_eq!(num, 0x12345678);
1066 /// let num = u32::from_be_bytes(raw_bytes);
1067 /// assert_eq!(num, 0x78563412);
1070 /// Turning a pointer into a `usize`:
1074 /// let ptr_num_transmute = unsafe {
1075 /// std::mem::transmute::<&i32, usize>(ptr)
1078 /// // Use an `as` cast instead
1079 /// let ptr_num_cast = ptr as *const i32 as usize;
1082 /// Note that using `transmute` to turn a pointer to a `usize` is (as noted above) [undefined
1083 /// behavior][ub] in `const` contexts. Also outside of consts, this operation might not behave
1084 /// as expected -- this is touching on many unspecified aspects of the Rust memory model.
1085 /// Depending on what the code is doing, the following alternatives are preferable to
1086 /// pointer-to-integer transmutation:
1087 /// - If the code just wants to store data of arbitrary type in some buffer and needs to pick a
1088 /// type for that buffer, it can use [`MaybeUninit`][mem::MaybeUninit].
1089 /// - If the code actually wants to work on the address the pointer points to, it can use `as`
1090 /// casts or [`ptr.addr()`][pointer::addr].
1092 /// Turning a `*mut T` into an `&mut T`:
1095 /// let ptr: *mut i32 = &mut 0;
1096 /// let ref_transmuted = unsafe {
1097 /// std::mem::transmute::<*mut i32, &mut i32>(ptr)
1100 /// // Use a reborrow instead
1101 /// let ref_casted = unsafe { &mut *ptr };
1104 /// Turning an `&mut T` into an `&mut U`:
1107 /// let ptr = &mut 0;
1108 /// let val_transmuted = unsafe {
1109 /// std::mem::transmute::<&mut i32, &mut u32>(ptr)
1112 /// // Now, put together `as` and reborrowing - note the chaining of `as`
1113 /// // `as` is not transitive
1114 /// let val_casts = unsafe { &mut *(ptr as *mut i32 as *mut u32) };
1117 /// Turning an `&str` into a `&[u8]`:
1120 /// // this is not a good way to do this.
1121 /// let slice = unsafe { std::mem::transmute::<&str, &[u8]>("Rust") };
1122 /// assert_eq!(slice, &[82, 117, 115, 116]);
1124 /// // You could use `str::as_bytes`
1125 /// let slice = "Rust".as_bytes();
1126 /// assert_eq!(slice, &[82, 117, 115, 116]);
1128 /// // Or, just use a byte string, if you have control over the string
1130 /// assert_eq!(b"Rust", &[82, 117, 115, 116]);
1133 /// Turning a `Vec<&T>` into a `Vec<Option<&T>>`.
1135 /// To transmute the inner type of the contents of a container, you must make sure to not
1136 /// violate any of the container's invariants. For `Vec`, this means that both the size
1137 /// *and alignment* of the inner types have to match. Other containers might rely on the
1138 /// size of the type, alignment, or even the `TypeId`, in which case transmuting wouldn't
1139 /// be possible at all without violating the container invariants.
1142 /// let store = [0, 1, 2, 3];
1143 /// let v_orig = store.iter().collect::<Vec<&i32>>();
1145 /// // clone the vector as we will reuse them later
1146 /// let v_clone = v_orig.clone();
1148 /// // Using transmute: this relies on the unspecified data layout of `Vec`, which is a
1149 /// // bad idea and could cause Undefined Behavior.
1150 /// // However, it is no-copy.
1151 /// let v_transmuted = unsafe {
1152 /// std::mem::transmute::<Vec<&i32>, Vec<Option<&i32>>>(v_clone)
1155 /// let v_clone = v_orig.clone();
1157 /// // This is the suggested, safe way.
1158 /// // It does copy the entire vector, though, into a new array.
1159 /// let v_collected = v_clone.into_iter()
1161 /// .collect::<Vec<Option<&i32>>>();
1163 /// let v_clone = v_orig.clone();
1165 /// // This is the proper no-copy, unsafe way of "transmuting" a `Vec`, without relying on the
1166 /// // data layout. Instead of literally calling `transmute`, we perform a pointer cast, but
1167 /// // in terms of converting the original inner type (`&i32`) to the new one (`Option<&i32>`),
1168 /// // this has all the same caveats. Besides the information provided above, also consult the
1169 /// // [`from_raw_parts`] documentation.
1170 /// let v_from_raw = unsafe {
1171 // FIXME Update this when vec_into_raw_parts is stabilized
1172 /// // Ensure the original vector is not dropped.
1173 /// let mut v_clone = std::mem::ManuallyDrop::new(v_clone);
1174 /// Vec::from_raw_parts(v_clone.as_mut_ptr() as *mut Option<&i32>,
1176 /// v_clone.capacity())
1180 /// [`from_raw_parts`]: ../../std/vec/struct.Vec.html#method.from_raw_parts
1182 /// Implementing `split_at_mut`:
1185 /// use std::{slice, mem};
1187 /// // There are multiple ways to do this, and there are multiple problems
1188 /// // with the following (transmute) way.
1189 /// fn split_at_mut_transmute<T>(slice: &mut [T], mid: usize)
1190 /// -> (&mut [T], &mut [T]) {
1191 /// let len = slice.len();
1192 /// assert!(mid <= len);
1194 /// let slice2 = mem::transmute::<&mut [T], &mut [T]>(slice);
1195 /// // first: transmute is not type safe; all it checks is that T and
1196 /// // U are of the same size. Second, right here, you have two
1197 /// // mutable references pointing to the same memory.
1198 /// (&mut slice[0..mid], &mut slice2[mid..len])
1202 /// // This gets rid of the type safety problems; `&mut *` will *only* give
1203 /// // you an `&mut T` from an `&mut T` or `*mut T`.
1204 /// fn split_at_mut_casts<T>(slice: &mut [T], mid: usize)
1205 /// -> (&mut [T], &mut [T]) {
1206 /// let len = slice.len();
1207 /// assert!(mid <= len);
1209 /// let slice2 = &mut *(slice as *mut [T]);
1210 /// // however, you still have two mutable references pointing to
1211 /// // the same memory.
1212 /// (&mut slice[0..mid], &mut slice2[mid..len])
1216 /// // This is how the standard library does it. This is the best method, if
1217 /// // you need to do something like this
1218 /// fn split_at_stdlib<T>(slice: &mut [T], mid: usize)
1219 /// -> (&mut [T], &mut [T]) {
1220 /// let len = slice.len();
1221 /// assert!(mid <= len);
1223 /// let ptr = slice.as_mut_ptr();
1224 /// // This now has three mutable references pointing at the same
1225 /// // memory. `slice`, the rvalue ret.0, and the rvalue ret.1.
1226 /// // `slice` is never used after `let ptr = ...`, and so one can
1227 /// // treat it as "dead", and therefore, you only have two real
1228 /// // mutable slices.
1229 /// (slice::from_raw_parts_mut(ptr, mid),
1230 /// slice::from_raw_parts_mut(ptr.add(mid), len - mid))
1234 #[stable(feature = "rust1", since = "1.0.0")]
1235 #[rustc_allowed_through_unstable_modules]
1236 #[rustc_const_stable(feature = "const_transmute", since = "1.56.0")]
1237 #[rustc_diagnostic_item = "transmute"]
1238 pub fn transmute<T, U>(e: T) -> U;
1240 /// Returns `true` if the actual type given as `T` requires drop
1241 /// glue; returns `false` if the actual type provided for `T`
1242 /// implements `Copy`.
1244 /// If the actual type neither requires drop glue nor implements
1245 /// `Copy`, then the return value of this function is unspecified.
1247 /// Note that, unlike most intrinsics, this is safe to call;
1248 /// it does not require an `unsafe` block.
1249 /// Therefore, implementations must not require the user to uphold
1250 /// any safety invariants.
1252 /// The stabilized version of this intrinsic is [`mem::needs_drop`](crate::mem::needs_drop).
1253 #[rustc_const_stable(feature = "const_needs_drop", since = "1.40.0")]
1254 pub fn needs_drop<T: ?Sized>() -> bool;
1256 /// Calculates the offset from a pointer.
1258 /// This is implemented as an intrinsic to avoid converting to and from an
1259 /// integer, since the conversion would throw away aliasing information.
1263 /// Both the starting and resulting pointer must be either in bounds or one
1264 /// byte past the end of an allocated object. If either pointer is out of
1265 /// bounds or arithmetic overflow occurs then any further use of the
1266 /// returned value will result in undefined behavior.
1268 /// The stabilized version of this intrinsic is [`pointer::offset`].
1269 #[must_use = "returns a new pointer rather than modifying its argument"]
1270 #[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
1271 pub fn offset<T>(dst: *const T, offset: isize) -> *const T;
1273 /// Calculates the offset from a pointer, potentially wrapping.
1275 /// This is implemented as an intrinsic to avoid converting to and from an
1276 /// integer, since the conversion inhibits certain optimizations.
1280 /// Unlike the `offset` intrinsic, this intrinsic does not restrict the
1281 /// resulting pointer to point into or one byte past the end of an allocated
1282 /// object, and it wraps with two's complement arithmetic. The resulting
1283 /// value is not necessarily valid to be used to actually access memory.
1285 /// The stabilized version of this intrinsic is [`pointer::wrapping_offset`].
1286 #[must_use = "returns a new pointer rather than modifying its argument"]
1287 #[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
1288 pub fn arith_offset<T>(dst: *const T, offset: isize) -> *const T;
1290 /// Masks out bits of the pointer according to a mask.
1292 /// Note that, unlike most intrinsics, this is safe to call;
1293 /// it does not require an `unsafe` block.
1294 /// Therefore, implementations must not require the user to uphold
1295 /// any safety invariants.
1297 /// Consider using [`pointer::mask`] instead.
1298 pub fn ptr_mask<T>(ptr: *const T, mask: usize) -> *const T;
1300 /// Equivalent to the appropriate `llvm.memcpy.p0i8.0i8.*` intrinsic, with
1301 /// a size of `count` * `size_of::<T>()` and an alignment of
1302 /// `min_align_of::<T>()`
1304 /// The volatile parameter is set to `true`, so it will not be optimized out
1305 /// unless size is equal to zero.
1307 /// This intrinsic does not have a stable counterpart.
1308 pub fn volatile_copy_nonoverlapping_memory<T>(dst: *mut T, src: *const T, count: usize);
1309 /// Equivalent to the appropriate `llvm.memmove.p0i8.0i8.*` intrinsic, with
1310 /// a size of `count * size_of::<T>()` and an alignment of
1311 /// `min_align_of::<T>()`
1313 /// The volatile parameter is set to `true`, so it will not be optimized out
1314 /// unless size is equal to zero.
1316 /// This intrinsic does not have a stable counterpart.
1317 pub fn volatile_copy_memory<T>(dst: *mut T, src: *const T, count: usize);
1318 /// Equivalent to the appropriate `llvm.memset.p0i8.*` intrinsic, with a
1319 /// size of `count * size_of::<T>()` and an alignment of
1320 /// `min_align_of::<T>()`.
1322 /// The volatile parameter is set to `true`, so it will not be optimized out
1323 /// unless size is equal to zero.
1325 /// This intrinsic does not have a stable counterpart.
1326 pub fn volatile_set_memory<T>(dst: *mut T, val: u8, count: usize);
1328 /// Performs a volatile load from the `src` pointer.
1330 /// The stabilized version of this intrinsic is [`core::ptr::read_volatile`].
1331 pub fn volatile_load<T>(src: *const T) -> T;
1332 /// Performs a volatile store to the `dst` pointer.
1334 /// The stabilized version of this intrinsic is [`core::ptr::write_volatile`].
1335 pub fn volatile_store<T>(dst: *mut T, val: T);
1337 /// Performs a volatile load from the `src` pointer
1338 /// The pointer is not required to be aligned.
1340 /// This intrinsic does not have a stable counterpart.
1341 pub fn unaligned_volatile_load<T>(src: *const T) -> T;
1342 /// Performs a volatile store to the `dst` pointer.
1343 /// The pointer is not required to be aligned.
1345 /// This intrinsic does not have a stable counterpart.
1346 pub fn unaligned_volatile_store<T>(dst: *mut T, val: T);
1348 /// Returns the square root of an `f32`
1350 /// The stabilized version of this intrinsic is
1351 /// [`f32::sqrt`](../../std/primitive.f32.html#method.sqrt)
1352 pub fn sqrtf32(x: f32) -> f32;
1353 /// Returns the square root of an `f64`
1355 /// The stabilized version of this intrinsic is
1356 /// [`f64::sqrt`](../../std/primitive.f64.html#method.sqrt)
1357 pub fn sqrtf64(x: f64) -> f64;
1359 /// Raises an `f32` to an integer power.
1361 /// The stabilized version of this intrinsic is
1362 /// [`f32::powi`](../../std/primitive.f32.html#method.powi)
1363 pub fn powif32(a: f32, x: i32) -> f32;
1364 /// Raises an `f64` to an integer power.
1366 /// The stabilized version of this intrinsic is
1367 /// [`f64::powi`](../../std/primitive.f64.html#method.powi)
1368 pub fn powif64(a: f64, x: i32) -> f64;
1370 /// Returns the sine of an `f32`.
1372 /// The stabilized version of this intrinsic is
1373 /// [`f32::sin`](../../std/primitive.f32.html#method.sin)
1374 pub fn sinf32(x: f32) -> f32;
1375 /// Returns the sine of an `f64`.
1377 /// The stabilized version of this intrinsic is
1378 /// [`f64::sin`](../../std/primitive.f64.html#method.sin)
1379 pub fn sinf64(x: f64) -> f64;
1381 /// Returns the cosine of an `f32`.
1383 /// The stabilized version of this intrinsic is
1384 /// [`f32::cos`](../../std/primitive.f32.html#method.cos)
1385 pub fn cosf32(x: f32) -> f32;
1386 /// Returns the cosine of an `f64`.
1388 /// The stabilized version of this intrinsic is
1389 /// [`f64::cos`](../../std/primitive.f64.html#method.cos)
1390 pub fn cosf64(x: f64) -> f64;
1392 /// Raises an `f32` to an `f32` power.
1394 /// The stabilized version of this intrinsic is
1395 /// [`f32::powf`](../../std/primitive.f32.html#method.powf)
1396 pub fn powf32(a: f32, x: f32) -> f32;
1397 /// Raises an `f64` to an `f64` power.
1399 /// The stabilized version of this intrinsic is
1400 /// [`f64::powf`](../../std/primitive.f64.html#method.powf)
1401 pub fn powf64(a: f64, x: f64) -> f64;
1403 /// Returns the exponential of an `f32`.
1405 /// The stabilized version of this intrinsic is
1406 /// [`f32::exp`](../../std/primitive.f32.html#method.exp)
1407 pub fn expf32(x: f32) -> f32;
1408 /// Returns the exponential of an `f64`.
1410 /// The stabilized version of this intrinsic is
1411 /// [`f64::exp`](../../std/primitive.f64.html#method.exp)
1412 pub fn expf64(x: f64) -> f64;
1414 /// Returns 2 raised to the power of an `f32`.
1416 /// The stabilized version of this intrinsic is
1417 /// [`f32::exp2`](../../std/primitive.f32.html#method.exp2)
1418 pub fn exp2f32(x: f32) -> f32;
1419 /// Returns 2 raised to the power of an `f64`.
1421 /// The stabilized version of this intrinsic is
1422 /// [`f64::exp2`](../../std/primitive.f64.html#method.exp2)
1423 pub fn exp2f64(x: f64) -> f64;
1425 /// Returns the natural logarithm of an `f32`.
1427 /// The stabilized version of this intrinsic is
1428 /// [`f32::ln`](../../std/primitive.f32.html#method.ln)
1429 pub fn logf32(x: f32) -> f32;
1430 /// Returns the natural logarithm of an `f64`.
1432 /// The stabilized version of this intrinsic is
1433 /// [`f64::ln`](../../std/primitive.f64.html#method.ln)
1434 pub fn logf64(x: f64) -> f64;
1436 /// Returns the base 10 logarithm of an `f32`.
1438 /// The stabilized version of this intrinsic is
1439 /// [`f32::log10`](../../std/primitive.f32.html#method.log10)
1440 pub fn log10f32(x: f32) -> f32;
1441 /// Returns the base 10 logarithm of an `f64`.
1443 /// The stabilized version of this intrinsic is
1444 /// [`f64::log10`](../../std/primitive.f64.html#method.log10)
1445 pub fn log10f64(x: f64) -> f64;
1447 /// Returns the base 2 logarithm of an `f32`.
1449 /// The stabilized version of this intrinsic is
1450 /// [`f32::log2`](../../std/primitive.f32.html#method.log2)
1451 pub fn log2f32(x: f32) -> f32;
1452 /// Returns the base 2 logarithm of an `f64`.
1454 /// The stabilized version of this intrinsic is
1455 /// [`f64::log2`](../../std/primitive.f64.html#method.log2)
1456 pub fn log2f64(x: f64) -> f64;
1458 /// Returns `a * b + c` for `f32` values.
1460 /// The stabilized version of this intrinsic is
1461 /// [`f32::mul_add`](../../std/primitive.f32.html#method.mul_add)
1462 pub fn fmaf32(a: f32, b: f32, c: f32) -> f32;
1463 /// Returns `a * b + c` for `f64` values.
1465 /// The stabilized version of this intrinsic is
1466 /// [`f64::mul_add`](../../std/primitive.f64.html#method.mul_add)
1467 pub fn fmaf64(a: f64, b: f64, c: f64) -> f64;
1469 /// Returns the absolute value of an `f32`.
1471 /// The stabilized version of this intrinsic is
1472 /// [`f32::abs`](../../std/primitive.f32.html#method.abs)
1473 pub fn fabsf32(x: f32) -> f32;
1474 /// Returns the absolute value of an `f64`.
1476 /// The stabilized version of this intrinsic is
1477 /// [`f64::abs`](../../std/primitive.f64.html#method.abs)
1478 pub fn fabsf64(x: f64) -> f64;
1480 /// Returns the minimum of two `f32` values.
1482 /// Note that, unlike most intrinsics, this is safe to call;
1483 /// it does not require an `unsafe` block.
1484 /// Therefore, implementations must not require the user to uphold
1485 /// any safety invariants.
1487 /// The stabilized version of this intrinsic is
1489 pub fn minnumf32(x: f32, y: f32) -> f32;
1490 /// Returns the minimum of two `f64` values.
1492 /// Note that, unlike most intrinsics, this is safe to call;
1493 /// it does not require an `unsafe` block.
1494 /// Therefore, implementations must not require the user to uphold
1495 /// any safety invariants.
1497 /// The stabilized version of this intrinsic is
1499 pub fn minnumf64(x: f64, y: f64) -> f64;
1500 /// Returns the maximum of two `f32` values.
1502 /// Note that, unlike most intrinsics, this is safe to call;
1503 /// it does not require an `unsafe` block.
1504 /// Therefore, implementations must not require the user to uphold
1505 /// any safety invariants.
1507 /// The stabilized version of this intrinsic is
1509 pub fn maxnumf32(x: f32, y: f32) -> f32;
1510 /// Returns the maximum of two `f64` values.
1512 /// Note that, unlike most intrinsics, this is safe to call;
1513 /// it does not require an `unsafe` block.
1514 /// Therefore, implementations must not require the user to uphold
1515 /// any safety invariants.
1517 /// The stabilized version of this intrinsic is
1519 pub fn maxnumf64(x: f64, y: f64) -> f64;
1521 /// Copies the sign from `y` to `x` for `f32` values.
1523 /// The stabilized version of this intrinsic is
1524 /// [`f32::copysign`](../../std/primitive.f32.html#method.copysign)
1525 pub fn copysignf32(x: f32, y: f32) -> f32;
1526 /// Copies the sign from `y` to `x` for `f64` values.
1528 /// The stabilized version of this intrinsic is
1529 /// [`f64::copysign`](../../std/primitive.f64.html#method.copysign)
1530 pub fn copysignf64(x: f64, y: f64) -> f64;
1532 /// Returns the largest integer less than or equal to an `f32`.
1534 /// The stabilized version of this intrinsic is
1535 /// [`f32::floor`](../../std/primitive.f32.html#method.floor)
1536 pub fn floorf32(x: f32) -> f32;
1537 /// Returns the largest integer less than or equal to an `f64`.
1539 /// The stabilized version of this intrinsic is
1540 /// [`f64::floor`](../../std/primitive.f64.html#method.floor)
1541 pub fn floorf64(x: f64) -> f64;
1543 /// Returns the smallest integer greater than or equal to an `f32`.
1545 /// The stabilized version of this intrinsic is
1546 /// [`f32::ceil`](../../std/primitive.f32.html#method.ceil)
1547 pub fn ceilf32(x: f32) -> f32;
1548 /// Returns the smallest integer greater than or equal to an `f64`.
1550 /// The stabilized version of this intrinsic is
1551 /// [`f64::ceil`](../../std/primitive.f64.html#method.ceil)
1552 pub fn ceilf64(x: f64) -> f64;
1554 /// Returns the integer part of an `f32`.
1556 /// The stabilized version of this intrinsic is
1557 /// [`f32::trunc`](../../std/primitive.f32.html#method.trunc)
1558 pub fn truncf32(x: f32) -> f32;
1559 /// Returns the integer part of an `f64`.
1561 /// The stabilized version of this intrinsic is
1562 /// [`f64::trunc`](../../std/primitive.f64.html#method.trunc)
1563 pub fn truncf64(x: f64) -> f64;
1565 /// Returns the nearest integer to an `f32`. May raise an inexact floating-point exception
1566 /// if the argument is not an integer.
1567 pub fn rintf32(x: f32) -> f32;
1568 /// Returns the nearest integer to an `f64`. May raise an inexact floating-point exception
1569 /// if the argument is not an integer.
1570 pub fn rintf64(x: f64) -> f64;
1572 /// Returns the nearest integer to an `f32`.
1574 /// This intrinsic does not have a stable counterpart.
1575 pub fn nearbyintf32(x: f32) -> f32;
1576 /// Returns the nearest integer to an `f64`.
1578 /// This intrinsic does not have a stable counterpart.
1579 pub fn nearbyintf64(x: f64) -> f64;
1581 /// Returns the nearest integer to an `f32`. Rounds half-way cases away from zero.
1583 /// The stabilized version of this intrinsic is
1584 /// [`f32::round`](../../std/primitive.f32.html#method.round)
1585 pub fn roundf32(x: f32) -> f32;
1586 /// Returns the nearest integer to an `f64`. Rounds half-way cases away from zero.
1588 /// The stabilized version of this intrinsic is
1589 /// [`f64::round`](../../std/primitive.f64.html#method.round)
1590 pub fn roundf64(x: f64) -> f64;
1592 /// Float addition that allows optimizations based on algebraic rules.
1593 /// May assume inputs are finite.
1595 /// This intrinsic does not have a stable counterpart.
1596 pub fn fadd_fast<T: Copy>(a: T, b: T) -> T;
1598 /// Float subtraction that allows optimizations based on algebraic rules.
1599 /// May assume inputs are finite.
1601 /// This intrinsic does not have a stable counterpart.
1602 pub fn fsub_fast<T: Copy>(a: T, b: T) -> T;
1604 /// Float multiplication that allows optimizations based on algebraic rules.
1605 /// May assume inputs are finite.
1607 /// This intrinsic does not have a stable counterpart.
1608 pub fn fmul_fast<T: Copy>(a: T, b: T) -> T;
1610 /// Float division that allows optimizations based on algebraic rules.
1611 /// May assume inputs are finite.
1613 /// This intrinsic does not have a stable counterpart.
1614 pub fn fdiv_fast<T: Copy>(a: T, b: T) -> T;
1616 /// Float remainder that allows optimizations based on algebraic rules.
1617 /// May assume inputs are finite.
1619 /// This intrinsic does not have a stable counterpart.
1620 pub fn frem_fast<T: Copy>(a: T, b: T) -> T;
1622 /// Convert with LLVM’s fptoui/fptosi, which may return undef for values out of range
1623 /// (<https://github.com/rust-lang/rust/issues/10184>)
1625 /// Stabilized as [`f32::to_int_unchecked`] and [`f64::to_int_unchecked`].
1626 pub fn float_to_int_unchecked<Float: Copy, Int: Copy>(value: Float) -> Int;
1628 /// Returns the number of bits set in an integer type `T`
1630 /// Note that, unlike most intrinsics, this is safe to call;
1631 /// it does not require an `unsafe` block.
1632 /// Therefore, implementations must not require the user to uphold
1633 /// any safety invariants.
1635 /// The stabilized versions of this intrinsic are available on the integer
1636 /// primitives via the `count_ones` method. For example,
1637 /// [`u32::count_ones`]
1638 #[rustc_const_stable(feature = "const_ctpop", since = "1.40.0")]
1639 pub fn ctpop<T: Copy>(x: T) -> T;
1641 /// Returns the number of leading unset bits (zeroes) in an integer type `T`.
1643 /// Note that, unlike most intrinsics, this is safe to call;
1644 /// it does not require an `unsafe` block.
1645 /// Therefore, implementations must not require the user to uphold
1646 /// any safety invariants.
1648 /// The stabilized versions of this intrinsic are available on the integer
1649 /// primitives via the `leading_zeros` method. For example,
1650 /// [`u32::leading_zeros`]
1655 /// #![feature(core_intrinsics)]
1657 /// use std::intrinsics::ctlz;
1659 /// let x = 0b0001_1100_u8;
1660 /// let num_leading = ctlz(x);
1661 /// assert_eq!(num_leading, 3);
1664 /// An `x` with value `0` will return the bit width of `T`.
1667 /// #![feature(core_intrinsics)]
1669 /// use std::intrinsics::ctlz;
1672 /// let num_leading = ctlz(x);
1673 /// assert_eq!(num_leading, 16);
1675 #[rustc_const_stable(feature = "const_ctlz", since = "1.40.0")]
1676 pub fn ctlz<T: Copy>(x: T) -> T;
1678 /// Like `ctlz`, but extra-unsafe as it returns `undef` when
1679 /// given an `x` with value `0`.
1681 /// This intrinsic does not have a stable counterpart.
1686 /// #![feature(core_intrinsics)]
1688 /// use std::intrinsics::ctlz_nonzero;
1690 /// let x = 0b0001_1100_u8;
1691 /// let num_leading = unsafe { ctlz_nonzero(x) };
1692 /// assert_eq!(num_leading, 3);
1694 #[rustc_const_stable(feature = "constctlz", since = "1.50.0")]
1695 pub fn ctlz_nonzero<T: Copy>(x: T) -> T;
1697 /// Returns the number of trailing unset bits (zeroes) in an integer type `T`.
1699 /// Note that, unlike most intrinsics, this is safe to call;
1700 /// it does not require an `unsafe` block.
1701 /// Therefore, implementations must not require the user to uphold
1702 /// any safety invariants.
1704 /// The stabilized versions of this intrinsic are available on the integer
1705 /// primitives via the `trailing_zeros` method. For example,
1706 /// [`u32::trailing_zeros`]
1711 /// #![feature(core_intrinsics)]
1713 /// use std::intrinsics::cttz;
1715 /// let x = 0b0011_1000_u8;
1716 /// let num_trailing = cttz(x);
1717 /// assert_eq!(num_trailing, 3);
1720 /// An `x` with value `0` will return the bit width of `T`:
1723 /// #![feature(core_intrinsics)]
1725 /// use std::intrinsics::cttz;
1728 /// let num_trailing = cttz(x);
1729 /// assert_eq!(num_trailing, 16);
1731 #[rustc_const_stable(feature = "const_cttz", since = "1.40.0")]
1732 pub fn cttz<T: Copy>(x: T) -> T;
1734 /// Like `cttz`, but extra-unsafe as it returns `undef` when
1735 /// given an `x` with value `0`.
1737 /// This intrinsic does not have a stable counterpart.
1742 /// #![feature(core_intrinsics)]
1744 /// use std::intrinsics::cttz_nonzero;
1746 /// let x = 0b0011_1000_u8;
1747 /// let num_trailing = unsafe { cttz_nonzero(x) };
1748 /// assert_eq!(num_trailing, 3);
1750 #[rustc_const_stable(feature = "const_cttz_nonzero", since = "1.53.0")]
1751 pub fn cttz_nonzero<T: Copy>(x: T) -> T;
1753 /// Reverses the bytes in an integer type `T`.
1755 /// Note that, unlike most intrinsics, this is safe to call;
1756 /// it does not require an `unsafe` block.
1757 /// Therefore, implementations must not require the user to uphold
1758 /// any safety invariants.
1760 /// The stabilized versions of this intrinsic are available on the integer
1761 /// primitives via the `swap_bytes` method. For example,
1762 /// [`u32::swap_bytes`]
1763 #[rustc_const_stable(feature = "const_bswap", since = "1.40.0")]
1764 pub fn bswap<T: Copy>(x: T) -> T;
1766 /// Reverses the bits in an integer type `T`.
1768 /// Note that, unlike most intrinsics, this is safe to call;
1769 /// it does not require an `unsafe` block.
1770 /// Therefore, implementations must not require the user to uphold
1771 /// any safety invariants.
1773 /// The stabilized versions of this intrinsic are available on the integer
1774 /// primitives via the `reverse_bits` method. For example,
1775 /// [`u32::reverse_bits`]
1776 #[rustc_const_stable(feature = "const_bitreverse", since = "1.40.0")]
1777 pub fn bitreverse<T: Copy>(x: T) -> T;
1779 /// Performs checked integer addition.
1781 /// Note that, unlike most intrinsics, this is safe to call;
1782 /// it does not require an `unsafe` block.
1783 /// Therefore, implementations must not require the user to uphold
1784 /// any safety invariants.
1786 /// The stabilized versions of this intrinsic are available on the integer
1787 /// primitives via the `overflowing_add` method. For example,
1788 /// [`u32::overflowing_add`]
1789 #[rustc_const_stable(feature = "const_int_overflow", since = "1.40.0")]
1790 pub fn add_with_overflow<T: Copy>(x: T, y: T) -> (T, bool);
1792 /// Performs checked integer subtraction
1794 /// Note that, unlike most intrinsics, this is safe to call;
1795 /// it does not require an `unsafe` block.
1796 /// Therefore, implementations must not require the user to uphold
1797 /// any safety invariants.
1799 /// The stabilized versions of this intrinsic are available on the integer
1800 /// primitives via the `overflowing_sub` method. For example,
1801 /// [`u32::overflowing_sub`]
1802 #[rustc_const_stable(feature = "const_int_overflow", since = "1.40.0")]
1803 pub fn sub_with_overflow<T: Copy>(x: T, y: T) -> (T, bool);
1805 /// Performs checked integer multiplication
1807 /// Note that, unlike most intrinsics, this is safe to call;
1808 /// it does not require an `unsafe` block.
1809 /// Therefore, implementations must not require the user to uphold
1810 /// any safety invariants.
1812 /// The stabilized versions of this intrinsic are available on the integer
1813 /// primitives via the `overflowing_mul` method. For example,
1814 /// [`u32::overflowing_mul`]
1815 #[rustc_const_stable(feature = "const_int_overflow", since = "1.40.0")]
1816 pub fn mul_with_overflow<T: Copy>(x: T, y: T) -> (T, bool);
1818 /// Performs an exact division, resulting in undefined behavior where
1819 /// `x % y != 0` or `y == 0` or `x == T::MIN && y == -1`
1821 /// This intrinsic does not have a stable counterpart.
1822 pub fn exact_div<T: Copy>(x: T, y: T) -> T;
1824 /// Performs an unchecked division, resulting in undefined behavior
1825 /// where `y == 0` or `x == T::MIN && y == -1`
1827 /// Safe wrappers for this intrinsic are available on the integer
1828 /// primitives via the `checked_div` method. For example,
1829 /// [`u32::checked_div`]
1830 #[rustc_const_stable(feature = "const_int_unchecked_div", since = "1.52.0")]
1831 pub fn unchecked_div<T: Copy>(x: T, y: T) -> T;
1832 /// Returns the remainder of an unchecked division, resulting in
1833 /// undefined behavior when `y == 0` or `x == T::MIN && y == -1`
1835 /// Safe wrappers for this intrinsic are available on the integer
1836 /// primitives via the `checked_rem` method. For example,
1837 /// [`u32::checked_rem`]
1838 #[rustc_const_stable(feature = "const_int_unchecked_rem", since = "1.52.0")]
1839 pub fn unchecked_rem<T: Copy>(x: T, y: T) -> T;
1841 /// Performs an unchecked left shift, resulting in undefined behavior when
1842 /// `y < 0` or `y >= N`, where N is the width of T in bits.
1844 /// Safe wrappers for this intrinsic are available on the integer
1845 /// primitives via the `checked_shl` method. For example,
1846 /// [`u32::checked_shl`]
1847 #[rustc_const_stable(feature = "const_int_unchecked", since = "1.40.0")]
1848 pub fn unchecked_shl<T: Copy>(x: T, y: T) -> T;
1849 /// Performs an unchecked right shift, resulting in undefined behavior when
1850 /// `y < 0` or `y >= N`, where N is the width of T in bits.
1852 /// Safe wrappers for this intrinsic are available on the integer
1853 /// primitives via the `checked_shr` method. For example,
1854 /// [`u32::checked_shr`]
1855 #[rustc_const_stable(feature = "const_int_unchecked", since = "1.40.0")]
1856 pub fn unchecked_shr<T: Copy>(x: T, y: T) -> T;
1858 /// Returns the result of an unchecked addition, resulting in
1859 /// undefined behavior when `x + y > T::MAX` or `x + y < T::MIN`.
1861 /// This intrinsic does not have a stable counterpart.
1862 #[rustc_const_unstable(feature = "const_int_unchecked_arith", issue = "none")]
1863 pub fn unchecked_add<T: Copy>(x: T, y: T) -> T;
1865 /// Returns the result of an unchecked subtraction, resulting in
1866 /// undefined behavior when `x - y > T::MAX` or `x - y < T::MIN`.
1868 /// This intrinsic does not have a stable counterpart.
1869 #[rustc_const_unstable(feature = "const_int_unchecked_arith", issue = "none")]
1870 pub fn unchecked_sub<T: Copy>(x: T, y: T) -> T;
1872 /// Returns the result of an unchecked multiplication, resulting in
1873 /// undefined behavior when `x * y > T::MAX` or `x * y < T::MIN`.
1875 /// This intrinsic does not have a stable counterpart.
1876 #[rustc_const_unstable(feature = "const_int_unchecked_arith", issue = "none")]
1877 pub fn unchecked_mul<T: Copy>(x: T, y: T) -> T;
1879 /// Performs rotate left.
1881 /// Note that, unlike most intrinsics, this is safe to call;
1882 /// it does not require an `unsafe` block.
1883 /// Therefore, implementations must not require the user to uphold
1884 /// any safety invariants.
1886 /// The stabilized versions of this intrinsic are available on the integer
1887 /// primitives via the `rotate_left` method. For example,
1888 /// [`u32::rotate_left`]
1889 #[rustc_const_stable(feature = "const_int_rotate", since = "1.40.0")]
1890 pub fn rotate_left<T: Copy>(x: T, y: T) -> T;
1892 /// Performs rotate right.
1894 /// Note that, unlike most intrinsics, this is safe to call;
1895 /// it does not require an `unsafe` block.
1896 /// Therefore, implementations must not require the user to uphold
1897 /// any safety invariants.
1899 /// The stabilized versions of this intrinsic are available on the integer
1900 /// primitives via the `rotate_right` method. For example,
1901 /// [`u32::rotate_right`]
1902 #[rustc_const_stable(feature = "const_int_rotate", since = "1.40.0")]
1903 pub fn rotate_right<T: Copy>(x: T, y: T) -> T;
1905 /// Returns (a + b) mod 2<sup>N</sup>, where N is the width of T in bits.
1907 /// Note that, unlike most intrinsics, this is safe to call;
1908 /// it does not require an `unsafe` block.
1909 /// Therefore, implementations must not require the user to uphold
1910 /// any safety invariants.
1912 /// The stabilized versions of this intrinsic are available on the integer
1913 /// primitives via the `wrapping_add` method. For example,
1914 /// [`u32::wrapping_add`]
1915 #[rustc_const_stable(feature = "const_int_wrapping", since = "1.40.0")]
1916 pub fn wrapping_add<T: Copy>(a: T, b: T) -> T;
1917 /// Returns (a - b) mod 2<sup>N</sup>, where N is the width of T in bits.
1919 /// Note that, unlike most intrinsics, this is safe to call;
1920 /// it does not require an `unsafe` block.
1921 /// Therefore, implementations must not require the user to uphold
1922 /// any safety invariants.
1924 /// The stabilized versions of this intrinsic are available on the integer
1925 /// primitives via the `wrapping_sub` method. For example,
1926 /// [`u32::wrapping_sub`]
1927 #[rustc_const_stable(feature = "const_int_wrapping", since = "1.40.0")]
1928 pub fn wrapping_sub<T: Copy>(a: T, b: T) -> T;
1929 /// Returns (a * b) mod 2<sup>N</sup>, where N is the width of T in bits.
1931 /// Note that, unlike most intrinsics, this is safe to call;
1932 /// it does not require an `unsafe` block.
1933 /// Therefore, implementations must not require the user to uphold
1934 /// any safety invariants.
1936 /// The stabilized versions of this intrinsic are available on the integer
1937 /// primitives via the `wrapping_mul` method. For example,
1938 /// [`u32::wrapping_mul`]
1939 #[rustc_const_stable(feature = "const_int_wrapping", since = "1.40.0")]
1940 pub fn wrapping_mul<T: Copy>(a: T, b: T) -> T;
1942 /// Computes `a + b`, saturating at numeric bounds.
1944 /// Note that, unlike most intrinsics, this is safe to call;
1945 /// it does not require an `unsafe` block.
1946 /// Therefore, implementations must not require the user to uphold
1947 /// any safety invariants.
1949 /// The stabilized versions of this intrinsic are available on the integer
1950 /// primitives via the `saturating_add` method. For example,
1951 /// [`u32::saturating_add`]
1952 #[rustc_const_stable(feature = "const_int_saturating", since = "1.40.0")]
1953 pub fn saturating_add<T: Copy>(a: T, b: T) -> T;
1954 /// Computes `a - b`, saturating at numeric bounds.
1956 /// Note that, unlike most intrinsics, this is safe to call;
1957 /// it does not require an `unsafe` block.
1958 /// Therefore, implementations must not require the user to uphold
1959 /// any safety invariants.
1961 /// The stabilized versions of this intrinsic are available on the integer
1962 /// primitives via the `saturating_sub` method. For example,
1963 /// [`u32::saturating_sub`]
1964 #[rustc_const_stable(feature = "const_int_saturating", since = "1.40.0")]
1965 pub fn saturating_sub<T: Copy>(a: T, b: T) -> T;
1967 /// Returns the value of the discriminant for the variant in 'v';
1968 /// if `T` has no discriminant, returns `0`.
1970 /// Note that, unlike most intrinsics, this is safe to call;
1971 /// it does not require an `unsafe` block.
1972 /// Therefore, implementations must not require the user to uphold
1973 /// any safety invariants.
1975 /// The stabilized version of this intrinsic is [`core::mem::discriminant`].
1976 #[rustc_const_unstable(feature = "const_discriminant", issue = "69821")]
1977 pub fn discriminant_value<T>(v: &T) -> <T as DiscriminantKind>::Discriminant;
1979 /// Returns the number of variants of the type `T` cast to a `usize`;
1980 /// if `T` has no variants, returns `0`. Uninhabited variants will be counted.
1982 /// Note that, unlike most intrinsics, this is safe to call;
1983 /// it does not require an `unsafe` block.
1984 /// Therefore, implementations must not require the user to uphold
1985 /// any safety invariants.
1987 /// The to-be-stabilized version of this intrinsic is [`mem::variant_count`].
1988 #[rustc_const_unstable(feature = "variant_count", issue = "73662")]
1989 pub fn variant_count<T>() -> usize;
1991 /// Rust's "try catch" construct which invokes the function pointer `try_fn`
1992 /// with the data pointer `data`.
1994 /// The third argument is a function called if a panic occurs. This function
1995 /// takes the data pointer and a pointer to the target-specific exception
1996 /// object that was caught. For more information see the compiler's
1997 /// source as well as std's catch implementation.
1998 pub fn r#try(try_fn: fn(*mut u8), data: *mut u8, catch_fn: fn(*mut u8, *mut u8)) -> i32;
2000 /// Emits a `!nontemporal` store according to LLVM (see their docs).
2001 /// Probably will never become stable.
2002 pub fn nontemporal_store<T>(ptr: *mut T, val: T);
2004 /// See documentation of `<*const T>::offset_from` for details.
2005 #[rustc_const_stable(feature = "const_ptr_offset_from", since = "1.65.0")]
2006 pub fn ptr_offset_from<T>(ptr: *const T, base: *const T) -> isize;
2008 /// See documentation of `<*const T>::sub_ptr` for details.
2009 #[rustc_const_unstable(feature = "const_ptr_sub_ptr", issue = "95892")]
2010 pub fn ptr_offset_from_unsigned<T>(ptr: *const T, base: *const T) -> usize;
2012 /// See documentation of `<*const T>::guaranteed_eq` for details.
2013 /// Returns `2` if the result is unknown.
2014 /// Returns `1` if the pointers are guaranteed equal
2015 /// Returns `0` if the pointers are guaranteed inequal
2017 /// Note that, unlike most intrinsics, this is safe to call;
2018 /// it does not require an `unsafe` block.
2019 /// Therefore, implementations must not require the user to uphold
2020 /// any safety invariants.
2021 #[rustc_const_unstable(feature = "const_raw_ptr_comparison", issue = "53020")]
2022 pub fn ptr_guaranteed_cmp<T>(ptr: *const T, other: *const T) -> u8;
2024 /// Allocates a block of memory at compile time.
2025 /// At runtime, just returns a null pointer.
2029 /// - The `align` argument must be a power of two.
2030 /// - At compile time, a compile error occurs if this constraint is violated.
2031 /// - At runtime, it is not checked.
2032 #[rustc_const_unstable(feature = "const_heap", issue = "79597")]
2033 pub fn const_allocate(size: usize, align: usize) -> *mut u8;
2035 /// Deallocates a memory which allocated by `intrinsics::const_allocate` at compile time.
2036 /// At runtime, does nothing.
2040 /// - The `align` argument must be a power of two.
2041 /// - At compile time, a compile error occurs if this constraint is violated.
2042 /// - At runtime, it is not checked.
2043 /// - If the `ptr` is created in an another const, this intrinsic doesn't deallocate it.
2044 /// - If the `ptr` is pointing to a local variable, this intrinsic doesn't deallocate it.
2045 #[rustc_const_unstable(feature = "const_heap", issue = "79597")]
2046 pub fn const_deallocate(ptr: *mut u8, size: usize, align: usize);
2048 /// Determines whether the raw bytes of the two values are equal.
2050 /// This is particularly handy for arrays, since it allows things like just
2051 /// comparing `i96`s instead of forcing `alloca`s for `[6 x i16]`.
2053 /// Above some backend-decided threshold this will emit calls to `memcmp`,
2054 /// like slice equality does, instead of causing massive code size.
2058 /// It's UB to call this if any of the *bytes* in `*a` or `*b` are uninitialized or carry a
2060 /// Note that this is a stricter criterion than just the *values* being
2061 /// fully-initialized: if `T` has padding, it's UB to call this intrinsic.
2063 /// (The implementation is allowed to branch on the results of comparisons,
2064 /// which is UB if any of their inputs are `undef`.)
2065 #[rustc_const_unstable(feature = "const_intrinsic_raw_eq", issue = "none")]
2066 pub fn raw_eq<T>(a: &T, b: &T) -> bool;
2068 /// See documentation of [`std::hint::black_box`] for details.
2070 /// [`std::hint::black_box`]: crate::hint::black_box
2071 #[rustc_const_unstable(feature = "const_black_box", issue = "none")]
2072 pub fn black_box<T>(dummy: T) -> T;
2074 /// `ptr` must point to a vtable.
2075 /// The intrinsic will return the size stored in that vtable.
2076 pub fn vtable_size(ptr: *const ()) -> usize;
2078 /// `ptr` must point to a vtable.
2079 /// The intrinsic will return the alignment stored in that vtable.
2080 pub fn vtable_align(ptr: *const ()) -> usize;
2082 /// Selects which function to call depending on the context.
2084 /// If this function is evaluated at compile-time, then a call to this
2085 /// intrinsic will be replaced with a call to `called_in_const`. It gets
2086 /// replaced with a call to `called_at_rt` otherwise.
2088 /// # Type Requirements
2090 /// The two functions must be both function items. They cannot be function
2091 /// pointers or closures. The first function must be a `const fn`.
2093 /// `arg` will be the tupled arguments that will be passed to either one of
2094 /// the two functions, therefore, both functions must accept the same type of
2095 /// arguments. Both functions must return RET.
2099 /// The two functions must behave observably equivalent. Safe code in other
2100 /// crates may assume that calling a `const fn` at compile-time and at run-time
2101 /// produces the same result. A function that produces a different result when
2102 /// evaluated at run-time, or has any other observable side-effects, is
2105 /// Here is an example of how this could cause a problem:
2107 /// #![feature(const_eval_select)]
2108 /// #![feature(core_intrinsics)]
2109 /// use std::hint::unreachable_unchecked;
2110 /// use std::intrinsics::const_eval_select;
2113 /// pub const fn inconsistent() -> i32 {
2114 /// fn runtime() -> i32 { 1 }
2115 /// const fn compiletime() -> i32 { 2 }
2118 // // ⚠ This code violates the required equivalence of `compiletime`
2119 /// // and `runtime`.
2120 /// const_eval_select((), compiletime, runtime)
2125 /// const X: i32 = inconsistent();
2126 /// let x = inconsistent();
2127 /// if x != X { unsafe { unreachable_unchecked(); }}
2130 /// This code causes Undefined Behavior when being run, since the
2131 /// `unreachable_unchecked` is actually being reached. The bug is in *crate A*,
2132 /// which violates the principle that a `const fn` must behave the same at
2133 /// compile-time and at run-time. The unsafe code in crate B is fine.
2134 #[rustc_const_unstable(feature = "const_eval_select", issue = "none")]
2135 pub fn const_eval_select<ARG, F, G, RET>(arg: ARG, called_in_const: F, called_at_rt: G) -> RET
2137 G: FnOnce<ARG, Output = RET>,
2138 F: FnOnce<ARG, Output = RET>;
2141 // Some functions are defined here because they accidentally got made
2142 // available in this module on stable. See <https://github.com/rust-lang/rust/issues/15702>.
2143 // (`transmute` also falls into this category, but it cannot be wrapped due to the
2144 // check that `T` and `U` have the same size.)
2146 /// Check that the preconditions of an unsafe function are followed, if debug_assertions are on,
2147 /// and only at runtime.
2149 /// This macro should be called as `assert_unsafe_precondition!([Generics](name: Type) => Expression)`
2150 /// where the names specified will be moved into the macro as captured variables, and defines an item
2151 /// to call `const_eval_select` on. The tokens inside the square brackets are used to denote generics
2152 /// for the function declaractions and can be omitted if there is no generics.
2156 /// Invoking this macro is only sound if the following code is already UB when the passed
2157 /// expression evaluates to false.
2159 /// This macro expands to a check at runtime if debug_assertions is set. It has no effect at
2160 /// compile time, but the semantics of the contained `const_eval_select` must be the same at
2161 /// runtime and at compile time. Thus if the expression evaluates to false, this macro produces
2162 /// different behavior at compile time and at runtime, and invoking it is incorrect.
2164 /// So in a sense it is UB if this macro is useful, but we expect callers of `unsafe fn` to make
2165 /// the occasional mistake, and this check should help them figure things out.
2166 #[allow_internal_unstable(const_eval_select)] // permit this to be called in stably-const fn
2167 macro_rules! assert_unsafe_precondition {
2168 ($([$($tt:tt)*])?($($i:ident:$ty:ty),*$(,)?) => $e:expr) => {
2169 if cfg!(debug_assertions) {
2170 // allow non_snake_case to allow capturing const generics
2171 #[allow(non_snake_case)]
2173 fn runtime$(<$($tt)*>)?($($i:$ty),*) {
2175 // abort instead of panicking to reduce impact on code size
2176 ::core::intrinsics::abort();
2179 #[allow(non_snake_case)]
2180 const fn comptime$(<$($tt)*>)?($(_:$ty),*) {}
2182 ::core::intrinsics::const_eval_select(($($i,)*), comptime, runtime);
2186 pub(crate) use assert_unsafe_precondition;
2188 /// Checks whether `ptr` is properly aligned with respect to
2189 /// `align_of::<T>()`.
2190 pub(crate) fn is_aligned_and_not_null<T>(ptr: *const T) -> bool {
2191 !ptr.is_null() && ptr.is_aligned()
2194 /// Checks whether the regions of memory starting at `src` and `dst` of size
2195 /// `count * size_of::<T>()` do *not* overlap.
2196 pub(crate) fn is_nonoverlapping<T>(src: *const T, dst: *const T, count: usize) -> bool {
2197 let src_usize = src.addr();
2198 let dst_usize = dst.addr();
2199 let size = mem::size_of::<T>().checked_mul(count).unwrap();
2200 let diff = if src_usize > dst_usize { src_usize - dst_usize } else { dst_usize - src_usize };
2201 // If the absolute distance between the ptrs is at least as big as the size of the buffer,
2202 // they do not overlap.
2206 /// Copies `count * size_of::<T>()` bytes from `src` to `dst`. The source
2207 /// and destination must *not* overlap.
2209 /// For regions of memory which might overlap, use [`copy`] instead.
2211 /// `copy_nonoverlapping` is semantically equivalent to C's [`memcpy`], but
2212 /// with the argument order swapped.
2214 /// The copy is "untyped" in the sense that data may be uninitialized or otherwise violate the
2215 /// requirements of `T`. The initialization state is preserved exactly.
2217 /// [`memcpy`]: https://en.cppreference.com/w/c/string/byte/memcpy
2221 /// Behavior is undefined if any of the following conditions are violated:
2223 /// * `src` must be [valid] for reads of `count * size_of::<T>()` bytes.
2225 /// * `dst` must be [valid] for writes of `count * size_of::<T>()` bytes.
2227 /// * Both `src` and `dst` must be properly aligned.
2229 /// * The region of memory beginning at `src` with a size of `count *
2230 /// size_of::<T>()` bytes must *not* overlap with the region of memory
2231 /// beginning at `dst` with the same size.
2233 /// Like [`read`], `copy_nonoverlapping` creates a bitwise copy of `T`, regardless of
2234 /// whether `T` is [`Copy`]. If `T` is not [`Copy`], using *both* the values
2235 /// in the region beginning at `*src` and the region beginning at `*dst` can
2236 /// [violate memory safety][read-ownership].
2238 /// Note that even if the effectively copied size (`count * size_of::<T>()`) is
2239 /// `0`, the pointers must be non-null and properly aligned.
2241 /// [`read`]: crate::ptr::read
2242 /// [read-ownership]: crate::ptr::read#ownership-of-the-returned-value
2243 /// [valid]: crate::ptr#safety
2247 /// Manually implement [`Vec::append`]:
2252 /// /// Moves all the elements of `src` into `dst`, leaving `src` empty.
2253 /// fn append<T>(dst: &mut Vec<T>, src: &mut Vec<T>) {
2254 /// let src_len = src.len();
2255 /// let dst_len = dst.len();
2257 /// // Ensure that `dst` has enough capacity to hold all of `src`.
2258 /// dst.reserve(src_len);
2261 /// // The call to add is always safe because `Vec` will never
2262 /// // allocate more than `isize::MAX` bytes.
2263 /// let dst_ptr = dst.as_mut_ptr().add(dst_len);
2264 /// let src_ptr = src.as_ptr();
2266 /// // Truncate `src` without dropping its contents. We do this first,
2267 /// // to avoid problems in case something further down panics.
2270 /// // The two regions cannot overlap because mutable references do
2271 /// // not alias, and two different vectors cannot own the same
2273 /// ptr::copy_nonoverlapping(src_ptr, dst_ptr, src_len);
2275 /// // Notify `dst` that it now holds the contents of `src`.
2276 /// dst.set_len(dst_len + src_len);
2280 /// let mut a = vec!['r'];
2281 /// let mut b = vec!['u', 's', 't'];
2283 /// append(&mut a, &mut b);
2285 /// assert_eq!(a, &['r', 'u', 's', 't']);
2286 /// assert!(b.is_empty());
2289 /// [`Vec::append`]: ../../std/vec/struct.Vec.html#method.append
2290 #[doc(alias = "memcpy")]
2291 #[stable(feature = "rust1", since = "1.0.0")]
2292 #[rustc_allowed_through_unstable_modules]
2293 #[rustc_const_stable(feature = "const_intrinsic_copy", since = "1.63.0")]
2295 #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
2296 pub const unsafe fn copy_nonoverlapping<T>(src: *const T, dst: *mut T, count: usize) {
2297 extern "rust-intrinsic" {
2298 #[rustc_const_stable(feature = "const_intrinsic_copy", since = "1.63.0")]
2299 pub fn copy_nonoverlapping<T>(src: *const T, dst: *mut T, count: usize);
2302 // SAFETY: the safety contract for `copy_nonoverlapping` must be
2303 // upheld by the caller.
2305 assert_unsafe_precondition!([T](src: *const T, dst: *mut T, count: usize) =>
2306 is_aligned_and_not_null(src)
2307 && is_aligned_and_not_null(dst)
2308 && is_nonoverlapping(src, dst, count)
2310 copy_nonoverlapping(src, dst, count)
2314 /// Copies `count * size_of::<T>()` bytes from `src` to `dst`. The source
2315 /// and destination may overlap.
2317 /// If the source and destination will *never* overlap,
2318 /// [`copy_nonoverlapping`] can be used instead.
2320 /// `copy` is semantically equivalent to C's [`memmove`], but with the argument
2321 /// order swapped. Copying takes place as if the bytes were copied from `src`
2322 /// to a temporary array and then copied from the array to `dst`.
2324 /// The copy is "untyped" in the sense that data may be uninitialized or otherwise violate the
2325 /// requirements of `T`. The initialization state is preserved exactly.
2327 /// [`memmove`]: https://en.cppreference.com/w/c/string/byte/memmove
2331 /// Behavior is undefined if any of the following conditions are violated:
2333 /// * `src` must be [valid] for reads of `count * size_of::<T>()` bytes.
2335 /// * `dst` must be [valid] for writes of `count * size_of::<T>()` bytes.
2337 /// * Both `src` and `dst` must be properly aligned.
2339 /// Like [`read`], `copy` creates a bitwise copy of `T`, regardless of
2340 /// whether `T` is [`Copy`]. If `T` is not [`Copy`], using both the values
2341 /// in the region beginning at `*src` and the region beginning at `*dst` can
2342 /// [violate memory safety][read-ownership].
2344 /// Note that even if the effectively copied size (`count * size_of::<T>()`) is
2345 /// `0`, the pointers must be non-null and properly aligned.
2347 /// [`read`]: crate::ptr::read
2348 /// [read-ownership]: crate::ptr::read#ownership-of-the-returned-value
2349 /// [valid]: crate::ptr#safety
2353 /// Efficiently create a Rust vector from an unsafe buffer:
2360 /// /// * `ptr` must be correctly aligned for its type and non-zero.
2361 /// /// * `ptr` must be valid for reads of `elts` contiguous elements of type `T`.
2362 /// /// * Those elements must not be used after calling this function unless `T: Copy`.
2363 /// # #[allow(dead_code)]
2364 /// unsafe fn from_buf_raw<T>(ptr: *const T, elts: usize) -> Vec<T> {
2365 /// let mut dst = Vec::with_capacity(elts);
2367 /// // SAFETY: Our precondition ensures the source is aligned and valid,
2368 /// // and `Vec::with_capacity` ensures that we have usable space to write them.
2369 /// ptr::copy(ptr, dst.as_mut_ptr(), elts);
2371 /// // SAFETY: We created it with this much capacity earlier,
2372 /// // and the previous `copy` has initialized these elements.
2373 /// dst.set_len(elts);
2377 #[doc(alias = "memmove")]
2378 #[stable(feature = "rust1", since = "1.0.0")]
2379 #[rustc_allowed_through_unstable_modules]
2380 #[rustc_const_stable(feature = "const_intrinsic_copy", since = "1.63.0")]
2382 #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
2383 pub const unsafe fn copy<T>(src: *const T, dst: *mut T, count: usize) {
2384 extern "rust-intrinsic" {
2385 #[rustc_const_stable(feature = "const_intrinsic_copy", since = "1.63.0")]
2386 fn copy<T>(src: *const T, dst: *mut T, count: usize);
2389 // SAFETY: the safety contract for `copy` must be upheld by the caller.
2391 assert_unsafe_precondition!([T](src: *const T, dst: *mut T) =>
2392 is_aligned_and_not_null(src) && is_aligned_and_not_null(dst));
2393 copy(src, dst, count)
2397 /// Sets `count * size_of::<T>()` bytes of memory starting at `dst` to
2400 /// `write_bytes` is similar to C's [`memset`], but sets `count *
2401 /// size_of::<T>()` bytes to `val`.
2403 /// [`memset`]: https://en.cppreference.com/w/c/string/byte/memset
2407 /// Behavior is undefined if any of the following conditions are violated:
2409 /// * `dst` must be [valid] for writes of `count * size_of::<T>()` bytes.
2411 /// * `dst` must be properly aligned.
2413 /// Note that even if the effectively copied size (`count * size_of::<T>()`) is
2414 /// `0`, the pointer must be non-null and properly aligned.
2416 /// Additionally, note that changing `*dst` in this way can easily lead to undefined behavior (UB)
2417 /// later if the written bytes are not a valid representation of some `T`. For instance, the
2418 /// following is an **incorrect** use of this function:
2422 /// let mut value: u8 = 0;
2423 /// let ptr: *mut bool = &mut value as *mut u8 as *mut bool;
2424 /// let _bool = ptr.read(); // This is fine, `ptr` points to a valid `bool`.
2425 /// ptr.write_bytes(42u8, 1); // This function itself does not cause UB...
2426 /// let _bool = ptr.read(); // ...but it makes this operation UB! ⚠️
2430 /// [valid]: crate::ptr#safety
2439 /// let mut vec = vec![0u32; 4];
2441 /// let vec_ptr = vec.as_mut_ptr();
2442 /// ptr::write_bytes(vec_ptr, 0xfe, 2);
2444 /// assert_eq!(vec, [0xfefefefe, 0xfefefefe, 0, 0]);
2446 #[doc(alias = "memset")]
2447 #[stable(feature = "rust1", since = "1.0.0")]
2448 #[rustc_allowed_through_unstable_modules]
2449 #[rustc_const_unstable(feature = "const_ptr_write", issue = "86302")]
2451 #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
2452 pub const unsafe fn write_bytes<T>(dst: *mut T, val: u8, count: usize) {
2453 extern "rust-intrinsic" {
2454 #[rustc_const_unstable(feature = "const_ptr_write", issue = "86302")]
2455 fn write_bytes<T>(dst: *mut T, val: u8, count: usize);
2458 // SAFETY: the safety contract for `write_bytes` must be upheld by the caller.
2460 assert_unsafe_precondition!([T](dst: *mut T) => is_aligned_and_not_null(dst));
2461 write_bytes(dst, val, count)