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 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
792 pub fn rustc_peek<T>(_: T) -> T;
794 /// Aborts the execution of the process.
796 /// Note that, unlike most intrinsics, this is safe to call;
797 /// it does not require an `unsafe` block.
798 /// Therefore, implementations must not require the user to uphold
799 /// any safety invariants.
801 /// [`std::process::abort`](../../std/process/fn.abort.html) is to be preferred if possible,
802 /// as its behavior is more user-friendly and more stable.
804 /// The current implementation of `intrinsics::abort` is to invoke an invalid instruction,
805 /// on most platforms.
807 /// process will probably terminate with a signal like `SIGABRT`, `SIGILL`, `SIGTRAP`, `SIGSEGV` or
808 /// `SIGBUS`. The precise behaviour is not guaranteed and not stable.
809 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
812 /// Informs the optimizer that this point in the code is not reachable,
813 /// enabling further optimizations.
815 /// N.B., this is very different from the `unreachable!()` macro: Unlike the
816 /// macro, which panics when it is executed, it is *undefined behavior* to
817 /// reach code marked with this function.
819 /// The stabilized version of this intrinsic is [`core::hint::unreachable_unchecked`].
820 #[rustc_const_stable(feature = "const_unreachable_unchecked", since = "1.57.0")]
821 pub fn unreachable() -> !;
823 /// Informs the optimizer that a condition is always true.
824 /// If the condition is false, the behavior is undefined.
826 /// No code is generated for this intrinsic, but the optimizer will try
827 /// to preserve it (and its condition) between passes, which may interfere
828 /// with optimization of surrounding code and reduce performance. It should
829 /// not be used if the invariant can be discovered by the optimizer on its
830 /// own, or if it does not enable any significant optimizations.
832 /// This intrinsic does not have a stable counterpart.
833 #[rustc_const_unstable(feature = "const_assume", issue = "76972")]
834 pub fn assume(b: bool);
836 /// Hints to the compiler that branch condition is likely to be true.
837 /// Returns the value passed to it.
839 /// Any use other than with `if` statements will probably not have an effect.
841 /// Note that, unlike most intrinsics, this is safe to call;
842 /// it does not require an `unsafe` block.
843 /// Therefore, implementations must not require the user to uphold
844 /// any safety invariants.
846 /// This intrinsic does not have a stable counterpart.
847 #[rustc_const_unstable(feature = "const_likely", issue = "none")]
848 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
849 pub fn likely(b: bool) -> bool;
851 /// Hints to the compiler that branch condition is likely to be false.
852 /// Returns the value passed to it.
854 /// Any use other than with `if` statements will probably not have an effect.
856 /// Note that, unlike most intrinsics, this is safe to call;
857 /// it does not require an `unsafe` block.
858 /// Therefore, implementations must not require the user to uphold
859 /// any safety invariants.
861 /// This intrinsic does not have a stable counterpart.
862 #[rustc_const_unstable(feature = "const_likely", issue = "none")]
863 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
864 pub fn unlikely(b: bool) -> bool;
866 /// Executes a breakpoint trap, for inspection by a debugger.
868 /// This intrinsic does not have a stable counterpart.
871 /// The size of a type in bytes.
873 /// Note that, unlike most intrinsics, this is safe to call;
874 /// it does not require an `unsafe` block.
875 /// Therefore, implementations must not require the user to uphold
876 /// any safety invariants.
878 /// More specifically, this is the offset in bytes between successive
879 /// items of the same type, including alignment padding.
881 /// The stabilized version of this intrinsic is [`core::mem::size_of`].
882 #[rustc_const_stable(feature = "const_size_of", since = "1.40.0")]
883 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
884 pub fn size_of<T>() -> usize;
886 /// The minimum alignment of a type.
888 /// Note that, unlike most intrinsics, this is safe to call;
889 /// it does not require an `unsafe` block.
890 /// Therefore, implementations must not require the user to uphold
891 /// any safety invariants.
893 /// The stabilized version of this intrinsic is [`core::mem::align_of`].
894 #[rustc_const_stable(feature = "const_min_align_of", since = "1.40.0")]
895 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
896 pub fn min_align_of<T>() -> usize;
897 /// The preferred alignment of a type.
899 /// This intrinsic does not have a stable counterpart.
900 /// It's "tracking issue" is [#91971](https://github.com/rust-lang/rust/issues/91971).
901 #[rustc_const_unstable(feature = "const_pref_align_of", issue = "91971")]
902 pub fn pref_align_of<T>() -> usize;
904 /// The size of the referenced value in bytes.
906 /// The stabilized version of this intrinsic is [`mem::size_of_val`].
907 #[rustc_const_unstable(feature = "const_size_of_val", issue = "46571")]
908 pub fn size_of_val<T: ?Sized>(_: *const T) -> usize;
909 /// The required alignment of the referenced value.
911 /// The stabilized version of this intrinsic is [`core::mem::align_of_val`].
912 #[rustc_const_unstable(feature = "const_align_of_val", issue = "46571")]
913 pub fn min_align_of_val<T: ?Sized>(_: *const T) -> usize;
915 /// Gets a static string slice containing the name of a type.
917 /// Note that, unlike most intrinsics, this is safe to call;
918 /// it does not require an `unsafe` block.
919 /// Therefore, implementations must not require the user to uphold
920 /// any safety invariants.
922 /// The stabilized version of this intrinsic is [`core::any::type_name`].
923 #[rustc_const_unstable(feature = "const_type_name", issue = "63084")]
924 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
925 pub fn type_name<T: ?Sized>() -> &'static str;
927 /// Gets an identifier which is globally unique to the specified type. This
928 /// function will return the same value for a type regardless of whichever
929 /// crate it is invoked in.
931 /// Note that, unlike most intrinsics, this is safe to call;
932 /// it does not require an `unsafe` block.
933 /// Therefore, implementations must not require the user to uphold
934 /// any safety invariants.
936 /// The stabilized version of this intrinsic is [`core::any::TypeId::of`].
937 #[rustc_const_unstable(feature = "const_type_id", issue = "77125")]
938 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
939 pub fn type_id<T: ?Sized + 'static>() -> u64;
941 /// A guard for unsafe functions that cannot ever be executed if `T` is uninhabited:
942 /// This will statically either panic, or do nothing.
944 /// This intrinsic does not have a stable counterpart.
945 #[rustc_const_stable(feature = "const_assert_type", since = "1.59.0")]
946 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
947 pub fn assert_inhabited<T>();
949 /// A guard for unsafe functions that cannot ever be executed if `T` does not permit
950 /// zero-initialization: This will statically either panic, or do nothing.
952 /// This intrinsic does not have a stable counterpart.
953 #[rustc_const_unstable(feature = "const_assert_type2", issue = "none")]
954 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
955 pub fn assert_zero_valid<T>();
957 /// A guard for unsafe functions that cannot ever be executed if `T` has invalid
958 /// bit patterns: This will statically either panic, or do nothing.
960 /// This intrinsic does not have a stable counterpart.
961 #[rustc_const_unstable(feature = "const_assert_type2", issue = "none")]
962 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
963 pub fn assert_uninit_valid<T>();
965 /// Gets a reference to a static `Location` indicating where it was called.
967 /// Note that, unlike most intrinsics, this is safe to call;
968 /// it does not require an `unsafe` block.
969 /// Therefore, implementations must not require the user to uphold
970 /// any safety invariants.
972 /// Consider using [`core::panic::Location::caller`] instead.
973 #[rustc_const_unstable(feature = "const_caller_location", issue = "76156")]
974 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
975 pub fn caller_location() -> &'static crate::panic::Location<'static>;
977 /// Moves a value out of scope without running drop glue.
979 /// This exists solely for [`mem::forget_unsized`]; normal `forget` uses
980 /// `ManuallyDrop` instead.
982 /// Note that, unlike most intrinsics, this is safe to call;
983 /// it does not require an `unsafe` block.
984 /// Therefore, implementations must not require the user to uphold
985 /// any safety invariants.
986 #[rustc_const_unstable(feature = "const_intrinsic_forget", issue = "none")]
987 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
988 pub fn forget<T: ?Sized>(_: T);
990 /// Reinterprets the bits of a value of one type as another type.
992 /// Both types must have the same size. Compilation will fail if this is not guaranteed.
994 /// `transmute` is semantically equivalent to a bitwise move of one type
995 /// into another. It copies the bits from the source value into the
996 /// destination value, then forgets the original. Note that source and destination
997 /// are passed by-value, which means if `T` or `U` contain padding, that padding
998 /// is *not* guaranteed to be preserved by `transmute`.
1000 /// Both the argument and the result must be [valid](../../nomicon/what-unsafe-does.html) at
1001 /// their given type. Violating this condition leads to [undefined behavior][ub]. The compiler
1002 /// will generate code *assuming that you, the programmer, ensure that there will never be
1003 /// undefined behavior*. It is therefore your responsibility to guarantee that every value
1004 /// passed to `transmute` is valid at both types `T` and `U`. Failing to uphold this condition
1005 /// may lead to unexpected and unstable compilation results. This makes `transmute` **incredibly
1006 /// unsafe**. `transmute` should be the absolute last resort.
1008 /// Transmuting pointers to integers in a `const` context is [undefined behavior][ub].
1009 /// Any attempt to use the resulting value for integer operations will abort const-evaluation.
1010 /// (And even outside `const`, such transmutation is touching on many unspecified aspects of the
1011 /// Rust memory model and should be avoided. See below for alternatives.)
1013 /// Because `transmute` is a by-value operation, alignment of the *transmuted values
1014 /// themselves* is not a concern. As with any other function, the compiler already ensures
1015 /// both `T` and `U` are properly aligned. However, when transmuting values that *point
1016 /// elsewhere* (such as pointers, references, boxes…), the caller has to ensure proper
1017 /// alignment of the pointed-to values.
1019 /// The [nomicon](../../nomicon/transmutes.html) has additional documentation.
1021 /// [ub]: ../../reference/behavior-considered-undefined.html
1025 /// There are a few things that `transmute` is really useful for.
1027 /// Turning a pointer into a function pointer. This is *not* portable to
1028 /// machines where function pointers and data pointers have different sizes.
1031 /// fn foo() -> i32 {
1034 /// // Crucially, we `as`-cast to a raw pointer before `transmute`ing to a function pointer.
1035 /// // This avoids an integer-to-pointer `transmute`, which can be problematic.
1036 /// // Transmuting between raw pointers and function pointers (i.e., two pointer types) is fine.
1037 /// let pointer = foo as *const ();
1038 /// let function = unsafe {
1039 /// std::mem::transmute::<*const (), fn() -> i32>(pointer)
1041 /// assert_eq!(function(), 0);
1044 /// Extending a lifetime, or shortening an invariant lifetime. This is
1045 /// advanced, very unsafe Rust!
1048 /// struct R<'a>(&'a i32);
1049 /// unsafe fn extend_lifetime<'b>(r: R<'b>) -> R<'static> {
1050 /// std::mem::transmute::<R<'b>, R<'static>>(r)
1053 /// unsafe fn shorten_invariant_lifetime<'b, 'c>(r: &'b mut R<'static>)
1054 /// -> &'b mut R<'c> {
1055 /// std::mem::transmute::<&'b mut R<'static>, &'b mut R<'c>>(r)
1061 /// Don't despair: many uses of `transmute` can be achieved through other means.
1062 /// Below are common applications of `transmute` which can be replaced with safer
1065 /// Turning raw bytes (`&[u8]`) into `u32`, `f64`, etc.:
1068 /// let raw_bytes = [0x78, 0x56, 0x34, 0x12];
1070 /// let num = unsafe {
1071 /// std::mem::transmute::<[u8; 4], u32>(raw_bytes)
1074 /// // use `u32::from_ne_bytes` instead
1075 /// let num = u32::from_ne_bytes(raw_bytes);
1076 /// // or use `u32::from_le_bytes` or `u32::from_be_bytes` to specify the endianness
1077 /// let num = u32::from_le_bytes(raw_bytes);
1078 /// assert_eq!(num, 0x12345678);
1079 /// let num = u32::from_be_bytes(raw_bytes);
1080 /// assert_eq!(num, 0x78563412);
1083 /// Turning a pointer into a `usize`:
1087 /// let ptr_num_transmute = unsafe {
1088 /// std::mem::transmute::<&i32, usize>(ptr)
1091 /// // Use an `as` cast instead
1092 /// let ptr_num_cast = ptr as *const i32 as usize;
1095 /// Note that using `transmute` to turn a pointer to a `usize` is (as noted above) [undefined
1096 /// behavior][ub] in `const` contexts. Also outside of consts, this operation might not behave
1097 /// as expected -- this is touching on many unspecified aspects of the Rust memory model.
1098 /// Depending on what the code is doing, the following alternatives are preferable to
1099 /// pointer-to-integer transmutation:
1100 /// - If the code just wants to store data of arbitrary type in some buffer and needs to pick a
1101 /// type for that buffer, it can use [`MaybeUninit`][mem::MaybeUninit].
1102 /// - If the code actually wants to work on the address the pointer points to, it can use `as`
1103 /// casts or [`ptr.addr()`][pointer::addr].
1105 /// Turning a `*mut T` into an `&mut T`:
1108 /// let ptr: *mut i32 = &mut 0;
1109 /// let ref_transmuted = unsafe {
1110 /// std::mem::transmute::<*mut i32, &mut i32>(ptr)
1113 /// // Use a reborrow instead
1114 /// let ref_casted = unsafe { &mut *ptr };
1117 /// Turning an `&mut T` into an `&mut U`:
1120 /// let ptr = &mut 0;
1121 /// let val_transmuted = unsafe {
1122 /// std::mem::transmute::<&mut i32, &mut u32>(ptr)
1125 /// // Now, put together `as` and reborrowing - note the chaining of `as`
1126 /// // `as` is not transitive
1127 /// let val_casts = unsafe { &mut *(ptr as *mut i32 as *mut u32) };
1130 /// Turning an `&str` into a `&[u8]`:
1133 /// // this is not a good way to do this.
1134 /// let slice = unsafe { std::mem::transmute::<&str, &[u8]>("Rust") };
1135 /// assert_eq!(slice, &[82, 117, 115, 116]);
1137 /// // You could use `str::as_bytes`
1138 /// let slice = "Rust".as_bytes();
1139 /// assert_eq!(slice, &[82, 117, 115, 116]);
1141 /// // Or, just use a byte string, if you have control over the string
1143 /// assert_eq!(b"Rust", &[82, 117, 115, 116]);
1146 /// Turning a `Vec<&T>` into a `Vec<Option<&T>>`.
1148 /// To transmute the inner type of the contents of a container, you must make sure to not
1149 /// violate any of the container's invariants. For `Vec`, this means that both the size
1150 /// *and alignment* of the inner types have to match. Other containers might rely on the
1151 /// size of the type, alignment, or even the `TypeId`, in which case transmuting wouldn't
1152 /// be possible at all without violating the container invariants.
1155 /// let store = [0, 1, 2, 3];
1156 /// let v_orig = store.iter().collect::<Vec<&i32>>();
1158 /// // clone the vector as we will reuse them later
1159 /// let v_clone = v_orig.clone();
1161 /// // Using transmute: this relies on the unspecified data layout of `Vec`, which is a
1162 /// // bad idea and could cause Undefined Behavior.
1163 /// // However, it is no-copy.
1164 /// let v_transmuted = unsafe {
1165 /// std::mem::transmute::<Vec<&i32>, Vec<Option<&i32>>>(v_clone)
1168 /// let v_clone = v_orig.clone();
1170 /// // This is the suggested, safe way.
1171 /// // It does copy the entire vector, though, into a new array.
1172 /// let v_collected = v_clone.into_iter()
1174 /// .collect::<Vec<Option<&i32>>>();
1176 /// let v_clone = v_orig.clone();
1178 /// // This is the proper no-copy, unsafe way of "transmuting" a `Vec`, without relying on the
1179 /// // data layout. Instead of literally calling `transmute`, we perform a pointer cast, but
1180 /// // in terms of converting the original inner type (`&i32`) to the new one (`Option<&i32>`),
1181 /// // this has all the same caveats. Besides the information provided above, also consult the
1182 /// // [`from_raw_parts`] documentation.
1183 /// let v_from_raw = unsafe {
1184 // FIXME Update this when vec_into_raw_parts is stabilized
1185 /// // Ensure the original vector is not dropped.
1186 /// let mut v_clone = std::mem::ManuallyDrop::new(v_clone);
1187 /// Vec::from_raw_parts(v_clone.as_mut_ptr() as *mut Option<&i32>,
1189 /// v_clone.capacity())
1193 /// [`from_raw_parts`]: ../../std/vec/struct.Vec.html#method.from_raw_parts
1195 /// Implementing `split_at_mut`:
1198 /// use std::{slice, mem};
1200 /// // There are multiple ways to do this, and there are multiple problems
1201 /// // with the following (transmute) way.
1202 /// fn split_at_mut_transmute<T>(slice: &mut [T], mid: usize)
1203 /// -> (&mut [T], &mut [T]) {
1204 /// let len = slice.len();
1205 /// assert!(mid <= len);
1207 /// let slice2 = mem::transmute::<&mut [T], &mut [T]>(slice);
1208 /// // first: transmute is not type safe; all it checks is that T and
1209 /// // U are of the same size. Second, right here, you have two
1210 /// // mutable references pointing to the same memory.
1211 /// (&mut slice[0..mid], &mut slice2[mid..len])
1215 /// // This gets rid of the type safety problems; `&mut *` will *only* give
1216 /// // you an `&mut T` from an `&mut T` or `*mut T`.
1217 /// fn split_at_mut_casts<T>(slice: &mut [T], mid: usize)
1218 /// -> (&mut [T], &mut [T]) {
1219 /// let len = slice.len();
1220 /// assert!(mid <= len);
1222 /// let slice2 = &mut *(slice as *mut [T]);
1223 /// // however, you still have two mutable references pointing to
1224 /// // the same memory.
1225 /// (&mut slice[0..mid], &mut slice2[mid..len])
1229 /// // This is how the standard library does it. This is the best method, if
1230 /// // you need to do something like this
1231 /// fn split_at_stdlib<T>(slice: &mut [T], mid: usize)
1232 /// -> (&mut [T], &mut [T]) {
1233 /// let len = slice.len();
1234 /// assert!(mid <= len);
1236 /// let ptr = slice.as_mut_ptr();
1237 /// // This now has three mutable references pointing at the same
1238 /// // memory. `slice`, the rvalue ret.0, and the rvalue ret.1.
1239 /// // `slice` is never used after `let ptr = ...`, and so one can
1240 /// // treat it as "dead", and therefore, you only have two real
1241 /// // mutable slices.
1242 /// (slice::from_raw_parts_mut(ptr, mid),
1243 /// slice::from_raw_parts_mut(ptr.add(mid), len - mid))
1247 #[stable(feature = "rust1", since = "1.0.0")]
1248 #[rustc_allowed_through_unstable_modules]
1249 #[rustc_const_stable(feature = "const_transmute", since = "1.56.0")]
1250 #[rustc_diagnostic_item = "transmute"]
1251 pub fn transmute<T, U>(e: T) -> U;
1253 /// Returns `true` if the actual type given as `T` requires drop
1254 /// glue; returns `false` if the actual type provided for `T`
1255 /// implements `Copy`.
1257 /// If the actual type neither requires drop glue nor implements
1258 /// `Copy`, then the return value of this function is unspecified.
1260 /// Note that, unlike most intrinsics, this is safe to call;
1261 /// it does not require an `unsafe` block.
1262 /// Therefore, implementations must not require the user to uphold
1263 /// any safety invariants.
1265 /// The stabilized version of this intrinsic is [`mem::needs_drop`](crate::mem::needs_drop).
1266 #[rustc_const_stable(feature = "const_needs_drop", since = "1.40.0")]
1267 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
1268 pub fn needs_drop<T: ?Sized>() -> bool;
1270 /// Calculates the offset from a pointer.
1272 /// This is implemented as an intrinsic to avoid converting to and from an
1273 /// integer, since the conversion would throw away aliasing information.
1277 /// Both the starting and resulting pointer must be either in bounds or one
1278 /// byte past the end of an allocated object. If either pointer is out of
1279 /// bounds or arithmetic overflow occurs then any further use of the
1280 /// returned value will result in undefined behavior.
1282 /// The stabilized version of this intrinsic is [`pointer::offset`].
1283 #[must_use = "returns a new pointer rather than modifying its argument"]
1284 #[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
1285 pub fn offset<T>(dst: *const T, offset: isize) -> *const T;
1287 /// Calculates the offset from a pointer, potentially wrapping.
1289 /// This is implemented as an intrinsic to avoid converting to and from an
1290 /// integer, since the conversion inhibits certain optimizations.
1294 /// Unlike the `offset` intrinsic, this intrinsic does not restrict the
1295 /// resulting pointer to point into or one byte past the end of an allocated
1296 /// object, and it wraps with two's complement arithmetic. The resulting
1297 /// value is not necessarily valid to be used to actually access memory.
1299 /// The stabilized version of this intrinsic is [`pointer::wrapping_offset`].
1300 #[must_use = "returns a new pointer rather than modifying its argument"]
1301 #[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
1302 pub fn arith_offset<T>(dst: *const T, offset: isize) -> *const T;
1304 /// Masks out bits of the pointer according to a mask.
1306 /// Note that, unlike most intrinsics, this is safe to call;
1307 /// it does not require an `unsafe` block.
1308 /// Therefore, implementations must not require the user to uphold
1309 /// any safety invariants.
1311 /// Consider using [`pointer::mask`] instead.
1312 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
1313 pub fn ptr_mask<T>(ptr: *const T, mask: usize) -> *const T;
1315 /// Equivalent to the appropriate `llvm.memcpy.p0i8.0i8.*` intrinsic, with
1316 /// a size of `count` * `size_of::<T>()` and an alignment of
1317 /// `min_align_of::<T>()`
1319 /// The volatile parameter is set to `true`, so it will not be optimized out
1320 /// unless size is equal to zero.
1322 /// This intrinsic does not have a stable counterpart.
1323 pub fn volatile_copy_nonoverlapping_memory<T>(dst: *mut T, src: *const T, count: usize);
1324 /// Equivalent to the appropriate `llvm.memmove.p0i8.0i8.*` intrinsic, with
1325 /// a size of `count * size_of::<T>()` and an alignment of
1326 /// `min_align_of::<T>()`
1328 /// The volatile parameter is set to `true`, so it will not be optimized out
1329 /// unless size is equal to zero.
1331 /// This intrinsic does not have a stable counterpart.
1332 pub fn volatile_copy_memory<T>(dst: *mut T, src: *const T, count: usize);
1333 /// Equivalent to the appropriate `llvm.memset.p0i8.*` intrinsic, with a
1334 /// size of `count * size_of::<T>()` and an alignment of
1335 /// `min_align_of::<T>()`.
1337 /// The volatile parameter is set to `true`, so it will not be optimized out
1338 /// unless size is equal to zero.
1340 /// This intrinsic does not have a stable counterpart.
1341 pub fn volatile_set_memory<T>(dst: *mut T, val: u8, count: usize);
1343 /// Performs a volatile load from the `src` pointer.
1345 /// The stabilized version of this intrinsic is [`core::ptr::read_volatile`].
1346 pub fn volatile_load<T>(src: *const T) -> T;
1347 /// Performs a volatile store to the `dst` pointer.
1349 /// The stabilized version of this intrinsic is [`core::ptr::write_volatile`].
1350 pub fn volatile_store<T>(dst: *mut T, val: T);
1352 /// Performs a volatile load from the `src` pointer
1353 /// The pointer is not required to be aligned.
1355 /// This intrinsic does not have a stable counterpart.
1356 pub fn unaligned_volatile_load<T>(src: *const T) -> T;
1357 /// Performs a volatile store to the `dst` pointer.
1358 /// The pointer is not required to be aligned.
1360 /// This intrinsic does not have a stable counterpart.
1361 pub fn unaligned_volatile_store<T>(dst: *mut T, val: T);
1363 /// Returns the square root of an `f32`
1365 /// The stabilized version of this intrinsic is
1366 /// [`f32::sqrt`](../../std/primitive.f32.html#method.sqrt)
1367 pub fn sqrtf32(x: f32) -> f32;
1368 /// Returns the square root of an `f64`
1370 /// The stabilized version of this intrinsic is
1371 /// [`f64::sqrt`](../../std/primitive.f64.html#method.sqrt)
1372 pub fn sqrtf64(x: f64) -> f64;
1374 /// Raises an `f32` to an integer power.
1376 /// The stabilized version of this intrinsic is
1377 /// [`f32::powi`](../../std/primitive.f32.html#method.powi)
1378 pub fn powif32(a: f32, x: i32) -> f32;
1379 /// Raises an `f64` to an integer power.
1381 /// The stabilized version of this intrinsic is
1382 /// [`f64::powi`](../../std/primitive.f64.html#method.powi)
1383 pub fn powif64(a: f64, x: i32) -> f64;
1385 /// Returns the sine of an `f32`.
1387 /// The stabilized version of this intrinsic is
1388 /// [`f32::sin`](../../std/primitive.f32.html#method.sin)
1389 pub fn sinf32(x: f32) -> f32;
1390 /// Returns the sine of an `f64`.
1392 /// The stabilized version of this intrinsic is
1393 /// [`f64::sin`](../../std/primitive.f64.html#method.sin)
1394 pub fn sinf64(x: f64) -> f64;
1396 /// Returns the cosine of an `f32`.
1398 /// The stabilized version of this intrinsic is
1399 /// [`f32::cos`](../../std/primitive.f32.html#method.cos)
1400 pub fn cosf32(x: f32) -> f32;
1401 /// Returns the cosine of an `f64`.
1403 /// The stabilized version of this intrinsic is
1404 /// [`f64::cos`](../../std/primitive.f64.html#method.cos)
1405 pub fn cosf64(x: f64) -> f64;
1407 /// Raises an `f32` to an `f32` power.
1409 /// The stabilized version of this intrinsic is
1410 /// [`f32::powf`](../../std/primitive.f32.html#method.powf)
1411 pub fn powf32(a: f32, x: f32) -> f32;
1412 /// Raises an `f64` to an `f64` power.
1414 /// The stabilized version of this intrinsic is
1415 /// [`f64::powf`](../../std/primitive.f64.html#method.powf)
1416 pub fn powf64(a: f64, x: f64) -> f64;
1418 /// Returns the exponential of an `f32`.
1420 /// The stabilized version of this intrinsic is
1421 /// [`f32::exp`](../../std/primitive.f32.html#method.exp)
1422 pub fn expf32(x: f32) -> f32;
1423 /// Returns the exponential of an `f64`.
1425 /// The stabilized version of this intrinsic is
1426 /// [`f64::exp`](../../std/primitive.f64.html#method.exp)
1427 pub fn expf64(x: f64) -> f64;
1429 /// Returns 2 raised to the power of an `f32`.
1431 /// The stabilized version of this intrinsic is
1432 /// [`f32::exp2`](../../std/primitive.f32.html#method.exp2)
1433 pub fn exp2f32(x: f32) -> f32;
1434 /// Returns 2 raised to the power of an `f64`.
1436 /// The stabilized version of this intrinsic is
1437 /// [`f64::exp2`](../../std/primitive.f64.html#method.exp2)
1438 pub fn exp2f64(x: f64) -> f64;
1440 /// Returns the natural logarithm of an `f32`.
1442 /// The stabilized version of this intrinsic is
1443 /// [`f32::ln`](../../std/primitive.f32.html#method.ln)
1444 pub fn logf32(x: f32) -> f32;
1445 /// Returns the natural logarithm of an `f64`.
1447 /// The stabilized version of this intrinsic is
1448 /// [`f64::ln`](../../std/primitive.f64.html#method.ln)
1449 pub fn logf64(x: f64) -> f64;
1451 /// Returns the base 10 logarithm of an `f32`.
1453 /// The stabilized version of this intrinsic is
1454 /// [`f32::log10`](../../std/primitive.f32.html#method.log10)
1455 pub fn log10f32(x: f32) -> f32;
1456 /// Returns the base 10 logarithm of an `f64`.
1458 /// The stabilized version of this intrinsic is
1459 /// [`f64::log10`](../../std/primitive.f64.html#method.log10)
1460 pub fn log10f64(x: f64) -> f64;
1462 /// Returns the base 2 logarithm of an `f32`.
1464 /// The stabilized version of this intrinsic is
1465 /// [`f32::log2`](../../std/primitive.f32.html#method.log2)
1466 pub fn log2f32(x: f32) -> f32;
1467 /// Returns the base 2 logarithm of an `f64`.
1469 /// The stabilized version of this intrinsic is
1470 /// [`f64::log2`](../../std/primitive.f64.html#method.log2)
1471 pub fn log2f64(x: f64) -> f64;
1473 /// Returns `a * b + c` for `f32` values.
1475 /// The stabilized version of this intrinsic is
1476 /// [`f32::mul_add`](../../std/primitive.f32.html#method.mul_add)
1477 pub fn fmaf32(a: f32, b: f32, c: f32) -> f32;
1478 /// Returns `a * b + c` for `f64` values.
1480 /// The stabilized version of this intrinsic is
1481 /// [`f64::mul_add`](../../std/primitive.f64.html#method.mul_add)
1482 pub fn fmaf64(a: f64, b: f64, c: f64) -> f64;
1484 /// Returns the absolute value of an `f32`.
1486 /// The stabilized version of this intrinsic is
1487 /// [`f32::abs`](../../std/primitive.f32.html#method.abs)
1488 pub fn fabsf32(x: f32) -> f32;
1489 /// Returns the absolute value of an `f64`.
1491 /// The stabilized version of this intrinsic is
1492 /// [`f64::abs`](../../std/primitive.f64.html#method.abs)
1493 pub fn fabsf64(x: f64) -> f64;
1495 /// Returns the minimum of two `f32` values.
1497 /// Note that, unlike most intrinsics, this is safe to call;
1498 /// it does not require an `unsafe` block.
1499 /// Therefore, implementations must not require the user to uphold
1500 /// any safety invariants.
1502 /// The stabilized version of this intrinsic is
1504 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
1505 pub fn minnumf32(x: f32, y: f32) -> f32;
1506 /// Returns the minimum of two `f64` values.
1508 /// Note that, unlike most intrinsics, this is safe to call;
1509 /// it does not require an `unsafe` block.
1510 /// Therefore, implementations must not require the user to uphold
1511 /// any safety invariants.
1513 /// The stabilized version of this intrinsic is
1515 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
1516 pub fn minnumf64(x: f64, y: f64) -> f64;
1517 /// Returns the maximum of two `f32` values.
1519 /// Note that, unlike most intrinsics, this is safe to call;
1520 /// it does not require an `unsafe` block.
1521 /// Therefore, implementations must not require the user to uphold
1522 /// any safety invariants.
1524 /// The stabilized version of this intrinsic is
1526 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
1527 pub fn maxnumf32(x: f32, y: f32) -> f32;
1528 /// Returns the maximum of two `f64` values.
1530 /// Note that, unlike most intrinsics, this is safe to call;
1531 /// it does not require an `unsafe` block.
1532 /// Therefore, implementations must not require the user to uphold
1533 /// any safety invariants.
1535 /// The stabilized version of this intrinsic is
1537 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
1538 pub fn maxnumf64(x: f64, y: f64) -> f64;
1540 /// Copies the sign from `y` to `x` for `f32` values.
1542 /// The stabilized version of this intrinsic is
1543 /// [`f32::copysign`](../../std/primitive.f32.html#method.copysign)
1544 pub fn copysignf32(x: f32, y: f32) -> f32;
1545 /// Copies the sign from `y` to `x` for `f64` values.
1547 /// The stabilized version of this intrinsic is
1548 /// [`f64::copysign`](../../std/primitive.f64.html#method.copysign)
1549 pub fn copysignf64(x: f64, y: f64) -> f64;
1551 /// Returns the largest integer less than or equal to an `f32`.
1553 /// The stabilized version of this intrinsic is
1554 /// [`f32::floor`](../../std/primitive.f32.html#method.floor)
1555 pub fn floorf32(x: f32) -> f32;
1556 /// Returns the largest integer less than or equal to an `f64`.
1558 /// The stabilized version of this intrinsic is
1559 /// [`f64::floor`](../../std/primitive.f64.html#method.floor)
1560 pub fn floorf64(x: f64) -> f64;
1562 /// Returns the smallest integer greater than or equal to an `f32`.
1564 /// The stabilized version of this intrinsic is
1565 /// [`f32::ceil`](../../std/primitive.f32.html#method.ceil)
1566 pub fn ceilf32(x: f32) -> f32;
1567 /// Returns the smallest integer greater than or equal to an `f64`.
1569 /// The stabilized version of this intrinsic is
1570 /// [`f64::ceil`](../../std/primitive.f64.html#method.ceil)
1571 pub fn ceilf64(x: f64) -> f64;
1573 /// Returns the integer part of an `f32`.
1575 /// The stabilized version of this intrinsic is
1576 /// [`f32::trunc`](../../std/primitive.f32.html#method.trunc)
1577 pub fn truncf32(x: f32) -> f32;
1578 /// Returns the integer part of an `f64`.
1580 /// The stabilized version of this intrinsic is
1581 /// [`f64::trunc`](../../std/primitive.f64.html#method.trunc)
1582 pub fn truncf64(x: f64) -> f64;
1584 /// Returns the nearest integer to an `f32`. May raise an inexact floating-point exception
1585 /// if the argument is not an integer.
1586 pub fn rintf32(x: f32) -> f32;
1587 /// Returns the nearest integer to an `f64`. May raise an inexact floating-point exception
1588 /// if the argument is not an integer.
1589 pub fn rintf64(x: f64) -> f64;
1591 /// Returns the nearest integer to an `f32`.
1593 /// This intrinsic does not have a stable counterpart.
1594 pub fn nearbyintf32(x: f32) -> f32;
1595 /// Returns the nearest integer to an `f64`.
1597 /// This intrinsic does not have a stable counterpart.
1598 pub fn nearbyintf64(x: f64) -> f64;
1600 /// Returns the nearest integer to an `f32`. Rounds half-way cases away from zero.
1602 /// The stabilized version of this intrinsic is
1603 /// [`f32::round`](../../std/primitive.f32.html#method.round)
1604 pub fn roundf32(x: f32) -> f32;
1605 /// Returns the nearest integer to an `f64`. Rounds half-way cases away from zero.
1607 /// The stabilized version of this intrinsic is
1608 /// [`f64::round`](../../std/primitive.f64.html#method.round)
1609 pub fn roundf64(x: f64) -> f64;
1611 /// Float addition that allows optimizations based on algebraic rules.
1612 /// May assume inputs are finite.
1614 /// This intrinsic does not have a stable counterpart.
1615 pub fn fadd_fast<T: Copy>(a: T, b: T) -> T;
1617 /// Float subtraction that allows optimizations based on algebraic rules.
1618 /// May assume inputs are finite.
1620 /// This intrinsic does not have a stable counterpart.
1621 pub fn fsub_fast<T: Copy>(a: T, b: T) -> T;
1623 /// Float multiplication that allows optimizations based on algebraic rules.
1624 /// May assume inputs are finite.
1626 /// This intrinsic does not have a stable counterpart.
1627 pub fn fmul_fast<T: Copy>(a: T, b: T) -> T;
1629 /// Float division that allows optimizations based on algebraic rules.
1630 /// May assume inputs are finite.
1632 /// This intrinsic does not have a stable counterpart.
1633 pub fn fdiv_fast<T: Copy>(a: T, b: T) -> T;
1635 /// Float remainder that allows optimizations based on algebraic rules.
1636 /// May assume inputs are finite.
1638 /// This intrinsic does not have a stable counterpart.
1639 pub fn frem_fast<T: Copy>(a: T, b: T) -> T;
1641 /// Convert with LLVM’s fptoui/fptosi, which may return undef for values out of range
1642 /// (<https://github.com/rust-lang/rust/issues/10184>)
1644 /// Stabilized as [`f32::to_int_unchecked`] and [`f64::to_int_unchecked`].
1645 pub fn float_to_int_unchecked<Float: Copy, Int: Copy>(value: Float) -> Int;
1647 /// Returns the number of bits set in an integer type `T`
1649 /// Note that, unlike most intrinsics, this is safe to call;
1650 /// it does not require an `unsafe` block.
1651 /// Therefore, implementations must not require the user to uphold
1652 /// any safety invariants.
1654 /// The stabilized versions of this intrinsic are available on the integer
1655 /// primitives via the `count_ones` method. For example,
1656 /// [`u32::count_ones`]
1657 #[rustc_const_stable(feature = "const_ctpop", since = "1.40.0")]
1658 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
1659 pub fn ctpop<T: Copy>(x: T) -> T;
1661 /// Returns the number of leading unset bits (zeroes) in an integer type `T`.
1663 /// Note that, unlike most intrinsics, this is safe to call;
1664 /// it does not require an `unsafe` block.
1665 /// Therefore, implementations must not require the user to uphold
1666 /// any safety invariants.
1668 /// The stabilized versions of this intrinsic are available on the integer
1669 /// primitives via the `leading_zeros` method. For example,
1670 /// [`u32::leading_zeros`]
1675 /// #![feature(core_intrinsics)]
1677 /// use std::intrinsics::ctlz;
1679 /// let x = 0b0001_1100_u8;
1680 /// let num_leading = ctlz(x);
1681 /// assert_eq!(num_leading, 3);
1684 /// An `x` with value `0` will return the bit width of `T`.
1687 /// #![feature(core_intrinsics)]
1689 /// use std::intrinsics::ctlz;
1692 /// let num_leading = ctlz(x);
1693 /// assert_eq!(num_leading, 16);
1695 #[rustc_const_stable(feature = "const_ctlz", since = "1.40.0")]
1696 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
1697 pub fn ctlz<T: Copy>(x: T) -> T;
1699 /// Like `ctlz`, but extra-unsafe as it returns `undef` when
1700 /// given an `x` with value `0`.
1702 /// This intrinsic does not have a stable counterpart.
1707 /// #![feature(core_intrinsics)]
1709 /// use std::intrinsics::ctlz_nonzero;
1711 /// let x = 0b0001_1100_u8;
1712 /// let num_leading = unsafe { ctlz_nonzero(x) };
1713 /// assert_eq!(num_leading, 3);
1715 #[rustc_const_stable(feature = "constctlz", since = "1.50.0")]
1716 pub fn ctlz_nonzero<T: Copy>(x: T) -> T;
1718 /// Returns the number of trailing unset bits (zeroes) in an integer type `T`.
1720 /// Note that, unlike most intrinsics, this is safe to call;
1721 /// it does not require an `unsafe` block.
1722 /// Therefore, implementations must not require the user to uphold
1723 /// any safety invariants.
1725 /// The stabilized versions of this intrinsic are available on the integer
1726 /// primitives via the `trailing_zeros` method. For example,
1727 /// [`u32::trailing_zeros`]
1732 /// #![feature(core_intrinsics)]
1734 /// use std::intrinsics::cttz;
1736 /// let x = 0b0011_1000_u8;
1737 /// let num_trailing = cttz(x);
1738 /// assert_eq!(num_trailing, 3);
1741 /// An `x` with value `0` will return the bit width of `T`:
1744 /// #![feature(core_intrinsics)]
1746 /// use std::intrinsics::cttz;
1749 /// let num_trailing = cttz(x);
1750 /// assert_eq!(num_trailing, 16);
1752 #[rustc_const_stable(feature = "const_cttz", since = "1.40.0")]
1753 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
1754 pub fn cttz<T: Copy>(x: T) -> T;
1756 /// Like `cttz`, but extra-unsafe as it returns `undef` when
1757 /// given an `x` with value `0`.
1759 /// This intrinsic does not have a stable counterpart.
1764 /// #![feature(core_intrinsics)]
1766 /// use std::intrinsics::cttz_nonzero;
1768 /// let x = 0b0011_1000_u8;
1769 /// let num_trailing = unsafe { cttz_nonzero(x) };
1770 /// assert_eq!(num_trailing, 3);
1772 #[rustc_const_stable(feature = "const_cttz_nonzero", since = "1.53.0")]
1773 pub fn cttz_nonzero<T: Copy>(x: T) -> T;
1775 /// Reverses the bytes in an integer type `T`.
1777 /// Note that, unlike most intrinsics, this is safe to call;
1778 /// it does not require an `unsafe` block.
1779 /// Therefore, implementations must not require the user to uphold
1780 /// any safety invariants.
1782 /// The stabilized versions of this intrinsic are available on the integer
1783 /// primitives via the `swap_bytes` method. For example,
1784 /// [`u32::swap_bytes`]
1785 #[rustc_const_stable(feature = "const_bswap", since = "1.40.0")]
1786 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
1787 pub fn bswap<T: Copy>(x: T) -> T;
1789 /// Reverses the bits in an integer type `T`.
1791 /// Note that, unlike most intrinsics, this is safe to call;
1792 /// it does not require an `unsafe` block.
1793 /// Therefore, implementations must not require the user to uphold
1794 /// any safety invariants.
1796 /// The stabilized versions of this intrinsic are available on the integer
1797 /// primitives via the `reverse_bits` method. For example,
1798 /// [`u32::reverse_bits`]
1799 #[rustc_const_stable(feature = "const_bitreverse", since = "1.40.0")]
1800 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
1801 pub fn bitreverse<T: Copy>(x: T) -> T;
1803 /// Performs checked integer addition.
1805 /// Note that, unlike most intrinsics, this is safe to call;
1806 /// it does not require an `unsafe` block.
1807 /// Therefore, implementations must not require the user to uphold
1808 /// any safety invariants.
1810 /// The stabilized versions of this intrinsic are available on the integer
1811 /// primitives via the `overflowing_add` method. For example,
1812 /// [`u32::overflowing_add`]
1813 #[rustc_const_stable(feature = "const_int_overflow", since = "1.40.0")]
1814 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
1815 pub fn add_with_overflow<T: Copy>(x: T, y: T) -> (T, bool);
1817 /// Performs checked integer subtraction
1819 /// Note that, unlike most intrinsics, this is safe to call;
1820 /// it does not require an `unsafe` block.
1821 /// Therefore, implementations must not require the user to uphold
1822 /// any safety invariants.
1824 /// The stabilized versions of this intrinsic are available on the integer
1825 /// primitives via the `overflowing_sub` method. For example,
1826 /// [`u32::overflowing_sub`]
1827 #[rustc_const_stable(feature = "const_int_overflow", since = "1.40.0")]
1828 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
1829 pub fn sub_with_overflow<T: Copy>(x: T, y: T) -> (T, bool);
1831 /// Performs checked integer multiplication
1833 /// Note that, unlike most intrinsics, this is safe to call;
1834 /// it does not require an `unsafe` block.
1835 /// Therefore, implementations must not require the user to uphold
1836 /// any safety invariants.
1838 /// The stabilized versions of this intrinsic are available on the integer
1839 /// primitives via the `overflowing_mul` method. For example,
1840 /// [`u32::overflowing_mul`]
1841 #[rustc_const_stable(feature = "const_int_overflow", since = "1.40.0")]
1842 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
1843 pub fn mul_with_overflow<T: Copy>(x: T, y: T) -> (T, bool);
1845 /// Performs an exact division, resulting in undefined behavior where
1846 /// `x % y != 0` or `y == 0` or `x == T::MIN && y == -1`
1848 /// This intrinsic does not have a stable counterpart.
1849 pub fn exact_div<T: Copy>(x: T, y: T) -> T;
1851 /// Performs an unchecked division, resulting in undefined behavior
1852 /// where `y == 0` or `x == T::MIN && y == -1`
1854 /// Safe wrappers for this intrinsic are available on the integer
1855 /// primitives via the `checked_div` method. For example,
1856 /// [`u32::checked_div`]
1857 #[rustc_const_stable(feature = "const_int_unchecked_div", since = "1.52.0")]
1858 pub fn unchecked_div<T: Copy>(x: T, y: T) -> T;
1859 /// Returns the remainder of an unchecked division, resulting in
1860 /// undefined behavior when `y == 0` or `x == T::MIN && y == -1`
1862 /// Safe wrappers for this intrinsic are available on the integer
1863 /// primitives via the `checked_rem` method. For example,
1864 /// [`u32::checked_rem`]
1865 #[rustc_const_stable(feature = "const_int_unchecked_rem", since = "1.52.0")]
1866 pub fn unchecked_rem<T: Copy>(x: T, y: T) -> T;
1868 /// Performs an unchecked left shift, resulting in undefined behavior when
1869 /// `y < 0` or `y >= N`, where N is the width of T in bits.
1871 /// Safe wrappers for this intrinsic are available on the integer
1872 /// primitives via the `checked_shl` method. For example,
1873 /// [`u32::checked_shl`]
1874 #[rustc_const_stable(feature = "const_int_unchecked", since = "1.40.0")]
1875 pub fn unchecked_shl<T: Copy>(x: T, y: T) -> T;
1876 /// Performs an unchecked right shift, resulting in undefined behavior when
1877 /// `y < 0` or `y >= N`, where N is the width of T in bits.
1879 /// Safe wrappers for this intrinsic are available on the integer
1880 /// primitives via the `checked_shr` method. For example,
1881 /// [`u32::checked_shr`]
1882 #[rustc_const_stable(feature = "const_int_unchecked", since = "1.40.0")]
1883 pub fn unchecked_shr<T: Copy>(x: T, y: T) -> T;
1885 /// Returns the result of an unchecked addition, resulting in
1886 /// undefined behavior when `x + y > T::MAX` or `x + y < T::MIN`.
1888 /// This intrinsic does not have a stable counterpart.
1889 #[rustc_const_unstable(feature = "const_int_unchecked_arith", issue = "none")]
1890 pub fn unchecked_add<T: Copy>(x: T, y: T) -> T;
1892 /// Returns the result of an unchecked subtraction, resulting in
1893 /// undefined behavior when `x - y > T::MAX` or `x - y < T::MIN`.
1895 /// This intrinsic does not have a stable counterpart.
1896 #[rustc_const_unstable(feature = "const_int_unchecked_arith", issue = "none")]
1897 pub fn unchecked_sub<T: Copy>(x: T, y: T) -> T;
1899 /// Returns the result of an unchecked multiplication, resulting in
1900 /// undefined behavior when `x * y > T::MAX` or `x * y < T::MIN`.
1902 /// This intrinsic does not have a stable counterpart.
1903 #[rustc_const_unstable(feature = "const_int_unchecked_arith", issue = "none")]
1904 pub fn unchecked_mul<T: Copy>(x: T, y: T) -> T;
1906 /// Performs rotate left.
1908 /// Note that, unlike most intrinsics, this is safe to call;
1909 /// it does not require an `unsafe` block.
1910 /// Therefore, implementations must not require the user to uphold
1911 /// any safety invariants.
1913 /// The stabilized versions of this intrinsic are available on the integer
1914 /// primitives via the `rotate_left` method. For example,
1915 /// [`u32::rotate_left`]
1916 #[rustc_const_stable(feature = "const_int_rotate", since = "1.40.0")]
1917 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
1918 pub fn rotate_left<T: Copy>(x: T, y: T) -> T;
1920 /// Performs rotate right.
1922 /// Note that, unlike most intrinsics, this is safe to call;
1923 /// it does not require an `unsafe` block.
1924 /// Therefore, implementations must not require the user to uphold
1925 /// any safety invariants.
1927 /// The stabilized versions of this intrinsic are available on the integer
1928 /// primitives via the `rotate_right` method. For example,
1929 /// [`u32::rotate_right`]
1930 #[rustc_const_stable(feature = "const_int_rotate", since = "1.40.0")]
1931 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
1932 pub fn rotate_right<T: Copy>(x: T, y: T) -> T;
1934 /// Returns (a + b) mod 2<sup>N</sup>, where N is the width of T in bits.
1936 /// Note that, unlike most intrinsics, this is safe to call;
1937 /// it does not require an `unsafe` block.
1938 /// Therefore, implementations must not require the user to uphold
1939 /// any safety invariants.
1941 /// The stabilized versions of this intrinsic are available on the integer
1942 /// primitives via the `wrapping_add` method. For example,
1943 /// [`u32::wrapping_add`]
1944 #[rustc_const_stable(feature = "const_int_wrapping", since = "1.40.0")]
1945 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
1946 pub fn wrapping_add<T: Copy>(a: T, b: T) -> T;
1947 /// Returns (a - b) mod 2<sup>N</sup>, where N is the width of T in bits.
1949 /// Note that, unlike most intrinsics, this is safe to call;
1950 /// it does not require an `unsafe` block.
1951 /// Therefore, implementations must not require the user to uphold
1952 /// any safety invariants.
1954 /// The stabilized versions of this intrinsic are available on the integer
1955 /// primitives via the `wrapping_sub` method. For example,
1956 /// [`u32::wrapping_sub`]
1957 #[rustc_const_stable(feature = "const_int_wrapping", since = "1.40.0")]
1958 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
1959 pub fn wrapping_sub<T: Copy>(a: T, b: T) -> T;
1960 /// Returns (a * b) mod 2<sup>N</sup>, where N is the width of T in bits.
1962 /// Note that, unlike most intrinsics, this is safe to call;
1963 /// it does not require an `unsafe` block.
1964 /// Therefore, implementations must not require the user to uphold
1965 /// any safety invariants.
1967 /// The stabilized versions of this intrinsic are available on the integer
1968 /// primitives via the `wrapping_mul` method. For example,
1969 /// [`u32::wrapping_mul`]
1970 #[rustc_const_stable(feature = "const_int_wrapping", since = "1.40.0")]
1971 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
1972 pub fn wrapping_mul<T: Copy>(a: T, b: T) -> T;
1974 /// Computes `a + b`, saturating at numeric bounds.
1976 /// Note that, unlike most intrinsics, this is safe to call;
1977 /// it does not require an `unsafe` block.
1978 /// Therefore, implementations must not require the user to uphold
1979 /// any safety invariants.
1981 /// The stabilized versions of this intrinsic are available on the integer
1982 /// primitives via the `saturating_add` method. For example,
1983 /// [`u32::saturating_add`]
1984 #[rustc_const_stable(feature = "const_int_saturating", since = "1.40.0")]
1985 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
1986 pub fn saturating_add<T: Copy>(a: T, b: T) -> T;
1987 /// Computes `a - b`, saturating at numeric bounds.
1989 /// Note that, unlike most intrinsics, this is safe to call;
1990 /// it does not require an `unsafe` block.
1991 /// Therefore, implementations must not require the user to uphold
1992 /// any safety invariants.
1994 /// The stabilized versions of this intrinsic are available on the integer
1995 /// primitives via the `saturating_sub` method. For example,
1996 /// [`u32::saturating_sub`]
1997 #[rustc_const_stable(feature = "const_int_saturating", since = "1.40.0")]
1998 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
1999 pub fn saturating_sub<T: Copy>(a: T, b: T) -> T;
2001 /// Returns the value of the discriminant for the variant in 'v';
2002 /// if `T` has no discriminant, returns `0`.
2004 /// Note that, unlike most intrinsics, this is safe to call;
2005 /// it does not require an `unsafe` block.
2006 /// Therefore, implementations must not require the user to uphold
2007 /// any safety invariants.
2009 /// The stabilized version of this intrinsic is [`core::mem::discriminant`].
2010 #[rustc_const_unstable(feature = "const_discriminant", issue = "69821")]
2011 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
2012 pub fn discriminant_value<T>(v: &T) -> <T as DiscriminantKind>::Discriminant;
2014 /// Returns the number of variants of the type `T` cast to a `usize`;
2015 /// if `T` has no variants, returns `0`. Uninhabited variants will be counted.
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.
2022 /// The to-be-stabilized version of this intrinsic is [`mem::variant_count`].
2023 #[rustc_const_unstable(feature = "variant_count", issue = "73662")]
2024 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
2025 pub fn variant_count<T>() -> usize;
2027 /// Rust's "try catch" construct which invokes the function pointer `try_fn`
2028 /// with the data pointer `data`.
2030 /// The third argument is a function called if a panic occurs. This function
2031 /// takes the data pointer and a pointer to the target-specific exception
2032 /// object that was caught. For more information see the compiler's
2033 /// source as well as std's catch implementation.
2034 pub fn r#try(try_fn: fn(*mut u8), data: *mut u8, catch_fn: fn(*mut u8, *mut u8)) -> i32;
2036 /// Emits a `!nontemporal` store according to LLVM (see their docs).
2037 /// Probably will never become stable.
2038 pub fn nontemporal_store<T>(ptr: *mut T, val: T);
2040 /// See documentation of `<*const T>::offset_from` for details.
2041 #[rustc_const_stable(feature = "const_ptr_offset_from", since = "1.65.0")]
2042 pub fn ptr_offset_from<T>(ptr: *const T, base: *const T) -> isize;
2044 /// See documentation of `<*const T>::sub_ptr` for details.
2045 #[rustc_const_unstable(feature = "const_ptr_sub_ptr", issue = "95892")]
2046 pub fn ptr_offset_from_unsigned<T>(ptr: *const T, base: *const T) -> usize;
2048 /// See documentation of `<*const T>::guaranteed_eq` for details.
2049 /// Returns `2` if the result is unknown.
2050 /// Returns `1` if the pointers are guaranteed equal
2051 /// Returns `0` if the pointers are guaranteed inequal
2053 /// Note that, unlike most intrinsics, this is safe to call;
2054 /// it does not require an `unsafe` block.
2055 /// Therefore, implementations must not require the user to uphold
2056 /// any safety invariants.
2057 #[rustc_const_unstable(feature = "const_raw_ptr_comparison", issue = "53020")]
2058 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
2059 pub fn ptr_guaranteed_cmp<T>(ptr: *const T, other: *const T) -> u8;
2061 /// Allocates a block of memory at compile time.
2062 /// At runtime, just returns a null pointer.
2066 /// - The `align` argument must be a power of two.
2067 /// - At compile time, a compile error occurs if this constraint is violated.
2068 /// - At runtime, it is not checked.
2069 #[rustc_const_unstable(feature = "const_heap", issue = "79597")]
2070 pub fn const_allocate(size: usize, align: usize) -> *mut u8;
2072 /// Deallocates a memory which allocated by `intrinsics::const_allocate` at compile time.
2073 /// At runtime, does nothing.
2077 /// - The `align` argument must be a power of two.
2078 /// - At compile time, a compile error occurs if this constraint is violated.
2079 /// - At runtime, it is not checked.
2080 /// - If the `ptr` is created in an another const, this intrinsic doesn't deallocate it.
2081 /// - If the `ptr` is pointing to a local variable, this intrinsic doesn't deallocate it.
2082 #[rustc_const_unstable(feature = "const_heap", issue = "79597")]
2083 pub fn const_deallocate(ptr: *mut u8, size: usize, align: usize);
2085 /// Determines whether the raw bytes of the two values are equal.
2087 /// This is particularly handy for arrays, since it allows things like just
2088 /// comparing `i96`s instead of forcing `alloca`s for `[6 x i16]`.
2090 /// Above some backend-decided threshold this will emit calls to `memcmp`,
2091 /// like slice equality does, instead of causing massive code size.
2095 /// It's UB to call this if any of the *bytes* in `*a` or `*b` are uninitialized or carry a
2097 /// Note that this is a stricter criterion than just the *values* being
2098 /// fully-initialized: if `T` has padding, it's UB to call this intrinsic.
2100 /// (The implementation is allowed to branch on the results of comparisons,
2101 /// which is UB if any of their inputs are `undef`.)
2102 #[rustc_const_unstable(feature = "const_intrinsic_raw_eq", issue = "none")]
2103 pub fn raw_eq<T>(a: &T, b: &T) -> bool;
2105 /// See documentation of [`std::hint::black_box`] for details.
2107 /// [`std::hint::black_box`]: crate::hint::black_box
2108 #[rustc_const_unstable(feature = "const_black_box", issue = "none")]
2109 #[cfg_attr(not(bootstrap), rustc_safe_intrinsic)]
2110 pub fn black_box<T>(dummy: T) -> T;
2112 /// `ptr` must point to a vtable.
2113 /// The intrinsic will return the size stored in that vtable.
2114 pub fn vtable_size(ptr: *const ()) -> usize;
2116 /// `ptr` must point to a vtable.
2117 /// The intrinsic will return the alignment stored in that vtable.
2118 pub fn vtable_align(ptr: *const ()) -> usize;
2120 /// Selects which function to call depending on the context.
2122 /// If this function is evaluated at compile-time, then a call to this
2123 /// intrinsic will be replaced with a call to `called_in_const`. It gets
2124 /// replaced with a call to `called_at_rt` otherwise.
2126 /// # Type Requirements
2128 /// The two functions must be both function items. They cannot be function
2129 /// pointers or closures. The first function must be a `const fn`.
2131 /// `arg` will be the tupled arguments that will be passed to either one of
2132 /// the two functions, therefore, both functions must accept the same type of
2133 /// arguments. Both functions must return RET.
2137 /// The two functions must behave observably equivalent. Safe code in other
2138 /// crates may assume that calling a `const fn` at compile-time and at run-time
2139 /// produces the same result. A function that produces a different result when
2140 /// evaluated at run-time, or has any other observable side-effects, is
2143 /// Here is an example of how this could cause a problem:
2145 /// #![feature(const_eval_select)]
2146 /// #![feature(core_intrinsics)]
2147 /// use std::hint::unreachable_unchecked;
2148 /// use std::intrinsics::const_eval_select;
2151 /// pub const fn inconsistent() -> i32 {
2152 /// fn runtime() -> i32 { 1 }
2153 /// const fn compiletime() -> i32 { 2 }
2156 // // ⚠ This code violates the required equivalence of `compiletime`
2157 /// // and `runtime`.
2158 /// const_eval_select((), compiletime, runtime)
2163 /// const X: i32 = inconsistent();
2164 /// let x = inconsistent();
2165 /// if x != X { unsafe { unreachable_unchecked(); }}
2168 /// This code causes Undefined Behavior when being run, since the
2169 /// `unreachable_unchecked` is actually being reached. The bug is in *crate A*,
2170 /// which violates the principle that a `const fn` must behave the same at
2171 /// compile-time and at run-time. The unsafe code in crate B is fine.
2172 #[rustc_const_unstable(feature = "const_eval_select", issue = "none")]
2173 pub fn const_eval_select<ARG, F, G, RET>(arg: ARG, called_in_const: F, called_at_rt: G) -> RET
2175 G: FnOnce<ARG, Output = RET>,
2176 F: FnOnce<ARG, Output = RET>;
2179 // Some functions are defined here because they accidentally got made
2180 // available in this module on stable. See <https://github.com/rust-lang/rust/issues/15702>.
2181 // (`transmute` also falls into this category, but it cannot be wrapped due to the
2182 // check that `T` and `U` have the same size.)
2184 /// Check that the preconditions of an unsafe function are followed, if debug_assertions are on,
2185 /// and only at runtime.
2187 /// This macro should be called as `assert_unsafe_precondition!([Generics](name: Type) => Expression)`
2188 /// where the names specified will be moved into the macro as captured variables, and defines an item
2189 /// to call `const_eval_select` on. The tokens inside the square brackets are used to denote generics
2190 /// for the function declaractions and can be omitted if there is no generics.
2194 /// Invoking this macro is only sound if the following code is already UB when the passed
2195 /// expression evaluates to false.
2197 /// This macro expands to a check at runtime if debug_assertions is set. It has no effect at
2198 /// compile time, but the semantics of the contained `const_eval_select` must be the same at
2199 /// runtime and at compile time. Thus if the expression evaluates to false, this macro produces
2200 /// different behavior at compile time and at runtime, and invoking it is incorrect.
2202 /// So in a sense it is UB if this macro is useful, but we expect callers of `unsafe fn` to make
2203 /// the occasional mistake, and this check should help them figure things out.
2204 #[allow_internal_unstable(const_eval_select)] // permit this to be called in stably-const fn
2205 macro_rules! assert_unsafe_precondition {
2206 ($([$($tt:tt)*])?($($i:ident:$ty:ty),*$(,)?) => $e:expr) => {
2207 if cfg!(debug_assertions) {
2208 // allow non_snake_case to allow capturing const generics
2209 #[allow(non_snake_case)]
2211 fn runtime$(<$($tt)*>)?($($i:$ty),*) {
2213 // abort instead of panicking to reduce impact on code size
2214 ::core::intrinsics::abort();
2217 #[allow(non_snake_case)]
2218 const fn comptime$(<$($tt)*>)?($(_:$ty),*) {}
2220 ::core::intrinsics::const_eval_select(($($i,)*), comptime, runtime);
2224 pub(crate) use assert_unsafe_precondition;
2226 /// Checks whether `ptr` is properly aligned with respect to
2227 /// `align_of::<T>()`.
2228 pub(crate) fn is_aligned_and_not_null<T>(ptr: *const T) -> bool {
2229 !ptr.is_null() && ptr.is_aligned()
2232 /// Checks whether the regions of memory starting at `src` and `dst` of size
2233 /// `count * size_of::<T>()` do *not* overlap.
2234 pub(crate) fn is_nonoverlapping<T>(src: *const T, dst: *const T, count: usize) -> bool {
2235 let src_usize = src.addr();
2236 let dst_usize = dst.addr();
2237 let size = mem::size_of::<T>().checked_mul(count).unwrap();
2238 let diff = if src_usize > dst_usize { src_usize - dst_usize } else { dst_usize - src_usize };
2239 // If the absolute distance between the ptrs is at least as big as the size of the buffer,
2240 // they do not overlap.
2244 /// Copies `count * size_of::<T>()` bytes from `src` to `dst`. The source
2245 /// and destination must *not* overlap.
2247 /// For regions of memory which might overlap, use [`copy`] instead.
2249 /// `copy_nonoverlapping` is semantically equivalent to C's [`memcpy`], but
2250 /// with the argument order swapped.
2252 /// The copy is "untyped" in the sense that data may be uninitialized or otherwise violate the
2253 /// requirements of `T`. The initialization state is preserved exactly.
2255 /// [`memcpy`]: https://en.cppreference.com/w/c/string/byte/memcpy
2259 /// Behavior is undefined if any of the following conditions are violated:
2261 /// * `src` must be [valid] for reads of `count * size_of::<T>()` bytes.
2263 /// * `dst` must be [valid] for writes of `count * size_of::<T>()` bytes.
2265 /// * Both `src` and `dst` must be properly aligned.
2267 /// * The region of memory beginning at `src` with a size of `count *
2268 /// size_of::<T>()` bytes must *not* overlap with the region of memory
2269 /// beginning at `dst` with the same size.
2271 /// Like [`read`], `copy_nonoverlapping` creates a bitwise copy of `T`, regardless of
2272 /// whether `T` is [`Copy`]. If `T` is not [`Copy`], using *both* the values
2273 /// in the region beginning at `*src` and the region beginning at `*dst` can
2274 /// [violate memory safety][read-ownership].
2276 /// Note that even if the effectively copied size (`count * size_of::<T>()`) is
2277 /// `0`, the pointers must be non-null and properly aligned.
2279 /// [`read`]: crate::ptr::read
2280 /// [read-ownership]: crate::ptr::read#ownership-of-the-returned-value
2281 /// [valid]: crate::ptr#safety
2285 /// Manually implement [`Vec::append`]:
2290 /// /// Moves all the elements of `src` into `dst`, leaving `src` empty.
2291 /// fn append<T>(dst: &mut Vec<T>, src: &mut Vec<T>) {
2292 /// let src_len = src.len();
2293 /// let dst_len = dst.len();
2295 /// // Ensure that `dst` has enough capacity to hold all of `src`.
2296 /// dst.reserve(src_len);
2299 /// // The call to add is always safe because `Vec` will never
2300 /// // allocate more than `isize::MAX` bytes.
2301 /// let dst_ptr = dst.as_mut_ptr().add(dst_len);
2302 /// let src_ptr = src.as_ptr();
2304 /// // Truncate `src` without dropping its contents. We do this first,
2305 /// // to avoid problems in case something further down panics.
2308 /// // The two regions cannot overlap because mutable references do
2309 /// // not alias, and two different vectors cannot own the same
2311 /// ptr::copy_nonoverlapping(src_ptr, dst_ptr, src_len);
2313 /// // Notify `dst` that it now holds the contents of `src`.
2314 /// dst.set_len(dst_len + src_len);
2318 /// let mut a = vec!['r'];
2319 /// let mut b = vec!['u', 's', 't'];
2321 /// append(&mut a, &mut b);
2323 /// assert_eq!(a, &['r', 'u', 's', 't']);
2324 /// assert!(b.is_empty());
2327 /// [`Vec::append`]: ../../std/vec/struct.Vec.html#method.append
2328 #[doc(alias = "memcpy")]
2329 #[stable(feature = "rust1", since = "1.0.0")]
2330 #[rustc_allowed_through_unstable_modules]
2331 #[rustc_const_stable(feature = "const_intrinsic_copy", since = "1.63.0")]
2333 #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
2334 pub const unsafe fn copy_nonoverlapping<T>(src: *const T, dst: *mut T, count: usize) {
2335 extern "rust-intrinsic" {
2336 #[rustc_const_stable(feature = "const_intrinsic_copy", since = "1.63.0")]
2337 pub fn copy_nonoverlapping<T>(src: *const T, dst: *mut T, count: usize);
2340 // SAFETY: the safety contract for `copy_nonoverlapping` must be
2341 // upheld by the caller.
2343 assert_unsafe_precondition!([T](src: *const T, dst: *mut T, count: usize) =>
2344 is_aligned_and_not_null(src)
2345 && is_aligned_and_not_null(dst)
2346 && is_nonoverlapping(src, dst, count)
2348 copy_nonoverlapping(src, dst, count)
2352 /// Copies `count * size_of::<T>()` bytes from `src` to `dst`. The source
2353 /// and destination may overlap.
2355 /// If the source and destination will *never* overlap,
2356 /// [`copy_nonoverlapping`] can be used instead.
2358 /// `copy` is semantically equivalent to C's [`memmove`], but with the argument
2359 /// order swapped. Copying takes place as if the bytes were copied from `src`
2360 /// to a temporary array and then copied from the array to `dst`.
2362 /// The copy is "untyped" in the sense that data may be uninitialized or otherwise violate the
2363 /// requirements of `T`. The initialization state is preserved exactly.
2365 /// [`memmove`]: https://en.cppreference.com/w/c/string/byte/memmove
2369 /// Behavior is undefined if any of the following conditions are violated:
2371 /// * `src` must be [valid] for reads of `count * size_of::<T>()` bytes.
2373 /// * `dst` must be [valid] for writes of `count * size_of::<T>()` bytes.
2375 /// * Both `src` and `dst` must be properly aligned.
2377 /// Like [`read`], `copy` creates a bitwise copy of `T`, regardless of
2378 /// whether `T` is [`Copy`]. If `T` is not [`Copy`], using both the values
2379 /// in the region beginning at `*src` and the region beginning at `*dst` can
2380 /// [violate memory safety][read-ownership].
2382 /// Note that even if the effectively copied size (`count * size_of::<T>()`) is
2383 /// `0`, the pointers must be non-null and properly aligned.
2385 /// [`read`]: crate::ptr::read
2386 /// [read-ownership]: crate::ptr::read#ownership-of-the-returned-value
2387 /// [valid]: crate::ptr#safety
2391 /// Efficiently create a Rust vector from an unsafe buffer:
2398 /// /// * `ptr` must be correctly aligned for its type and non-zero.
2399 /// /// * `ptr` must be valid for reads of `elts` contiguous elements of type `T`.
2400 /// /// * Those elements must not be used after calling this function unless `T: Copy`.
2401 /// # #[allow(dead_code)]
2402 /// unsafe fn from_buf_raw<T>(ptr: *const T, elts: usize) -> Vec<T> {
2403 /// let mut dst = Vec::with_capacity(elts);
2405 /// // SAFETY: Our precondition ensures the source is aligned and valid,
2406 /// // and `Vec::with_capacity` ensures that we have usable space to write them.
2407 /// ptr::copy(ptr, dst.as_mut_ptr(), elts);
2409 /// // SAFETY: We created it with this much capacity earlier,
2410 /// // and the previous `copy` has initialized these elements.
2411 /// dst.set_len(elts);
2415 #[doc(alias = "memmove")]
2416 #[stable(feature = "rust1", since = "1.0.0")]
2417 #[rustc_allowed_through_unstable_modules]
2418 #[rustc_const_stable(feature = "const_intrinsic_copy", since = "1.63.0")]
2420 #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
2421 pub const unsafe fn copy<T>(src: *const T, dst: *mut T, count: usize) {
2422 extern "rust-intrinsic" {
2423 #[rustc_const_stable(feature = "const_intrinsic_copy", since = "1.63.0")]
2424 fn copy<T>(src: *const T, dst: *mut T, count: usize);
2427 // SAFETY: the safety contract for `copy` must be upheld by the caller.
2429 assert_unsafe_precondition!([T](src: *const T, dst: *mut T) =>
2430 is_aligned_and_not_null(src) && is_aligned_and_not_null(dst));
2431 copy(src, dst, count)
2435 /// Sets `count * size_of::<T>()` bytes of memory starting at `dst` to
2438 /// `write_bytes` is similar to C's [`memset`], but sets `count *
2439 /// size_of::<T>()` bytes to `val`.
2441 /// [`memset`]: https://en.cppreference.com/w/c/string/byte/memset
2445 /// Behavior is undefined if any of the following conditions are violated:
2447 /// * `dst` must be [valid] for writes of `count * size_of::<T>()` bytes.
2449 /// * `dst` must be properly aligned.
2451 /// Note that even if the effectively copied size (`count * size_of::<T>()`) is
2452 /// `0`, the pointer must be non-null and properly aligned.
2454 /// Additionally, note that changing `*dst` in this way can easily lead to undefined behavior (UB)
2455 /// later if the written bytes are not a valid representation of some `T`. For instance, the
2456 /// following is an **incorrect** use of this function:
2460 /// let mut value: u8 = 0;
2461 /// let ptr: *mut bool = &mut value as *mut u8 as *mut bool;
2462 /// let _bool = ptr.read(); // This is fine, `ptr` points to a valid `bool`.
2463 /// ptr.write_bytes(42u8, 1); // This function itself does not cause UB...
2464 /// let _bool = ptr.read(); // ...but it makes this operation UB! ⚠️
2468 /// [valid]: crate::ptr#safety
2477 /// let mut vec = vec![0u32; 4];
2479 /// let vec_ptr = vec.as_mut_ptr();
2480 /// ptr::write_bytes(vec_ptr, 0xfe, 2);
2482 /// assert_eq!(vec, [0xfefefefe, 0xfefefefe, 0, 0]);
2484 #[doc(alias = "memset")]
2485 #[stable(feature = "rust1", since = "1.0.0")]
2486 #[rustc_allowed_through_unstable_modules]
2487 #[rustc_const_unstable(feature = "const_ptr_write", issue = "86302")]
2489 #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
2490 pub const unsafe fn write_bytes<T>(dst: *mut T, val: u8, count: usize) {
2491 extern "rust-intrinsic" {
2492 #[rustc_const_unstable(feature = "const_ptr_write", issue = "86302")]
2493 fn write_bytes<T>(dst: *mut T, val: u8, count: usize);
2496 // SAFETY: the safety contract for `write_bytes` must be upheld by the caller.
2498 assert_unsafe_precondition!([T](dst: *mut T) => is_aligned_and_not_null(dst));
2499 write_bytes(dst, val, count)
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