1 //! Compiler intrinsics.
3 //! The corresponding definitions are in `compiler/rustc_codegen_llvm/src/intrinsic.rs`.
4 //! The corresponding const implementations are in `compiler/rustc_mir/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 //! `compiler/rustc_mir/src/interpret/intrinsics.rs` and add a
14 //! `#[rustc_const_unstable(feature = "foo", issue = "01234")]` to the intrinsic.
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]: http://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]: http://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")]
67 reason
= "no longer an intrinsic - use `ptr::drop_in_place` directly",
71 pub unsafe fn drop_in_place
<T
: ?Sized
>(to_drop
: *mut T
) {
72 // SAFETY: see `ptr::drop_in_place`
73 unsafe { crate::ptr::drop_in_place(to_drop) }
76 extern "rust-intrinsic" {
77 // N.B., these intrinsics take raw pointers because they mutate aliased
78 // memory, which is not valid for either `&` or `&mut`.
80 /// Stores a value if the current value is the same as the `old` value.
82 /// The stabilized version of this intrinsic is available on the
83 /// [`atomic`] types via the `compare_exchange` method by passing
84 /// [`Ordering::SeqCst`] as both the `success` and `failure` parameters.
85 /// For example, [`AtomicBool::compare_exchange`].
86 pub fn atomic_cxchg
<T
: Copy
>(dst
: *mut T
, old
: T
, src
: T
) -> (T
, bool
);
87 /// Stores a value if the current value is the same as the `old` value.
89 /// The stabilized version of this intrinsic is available on the
90 /// [`atomic`] types via the `compare_exchange` method by passing
91 /// [`Ordering::Acquire`] as both the `success` and `failure` parameters.
92 /// For example, [`AtomicBool::compare_exchange`].
93 pub fn atomic_cxchg_acq
<T
: Copy
>(dst
: *mut T
, old
: T
, src
: T
) -> (T
, bool
);
94 /// Stores a value if the current value is the same as the `old` value.
96 /// The stabilized version of this intrinsic is available on the
97 /// [`atomic`] types via the `compare_exchange` method by passing
98 /// [`Ordering::Release`] as the `success` and [`Ordering::Relaxed`] as the
99 /// `failure` parameters. For example, [`AtomicBool::compare_exchange`].
100 pub fn atomic_cxchg_rel
<T
: Copy
>(dst
: *mut T
, old
: T
, src
: T
) -> (T
, bool
);
101 /// Stores a value if the current value is the same as the `old` value.
103 /// The stabilized version of this intrinsic is available on the
104 /// [`atomic`] types via the `compare_exchange` method by passing
105 /// [`Ordering::AcqRel`] as the `success` and [`Ordering::Acquire`] as the
106 /// `failure` parameters. For example, [`AtomicBool::compare_exchange`].
107 pub fn atomic_cxchg_acqrel
<T
: Copy
>(dst
: *mut T
, old
: T
, src
: T
) -> (T
, bool
);
108 /// Stores a value if the current value is the same as the `old` value.
110 /// The stabilized version of this intrinsic is available on the
111 /// [`atomic`] types via the `compare_exchange` method by passing
112 /// [`Ordering::Relaxed`] as both the `success` and `failure` parameters.
113 /// For example, [`AtomicBool::compare_exchange`].
114 pub fn atomic_cxchg_relaxed
<T
: Copy
>(dst
: *mut T
, old
: T
, src
: T
) -> (T
, bool
);
115 /// Stores a value if the current value is the same as the `old` value.
117 /// The stabilized version of this intrinsic is available on the
118 /// [`atomic`] types via the `compare_exchange` method by passing
119 /// [`Ordering::SeqCst`] as the `success` and [`Ordering::Relaxed`] as the
120 /// `failure` parameters. For example, [`AtomicBool::compare_exchange`].
121 pub fn atomic_cxchg_failrelaxed
<T
: Copy
>(dst
: *mut T
, old
: T
, src
: T
) -> (T
, bool
);
122 /// Stores a value if the current value is the same as the `old` value.
124 /// The stabilized version of this intrinsic is available on the
125 /// [`atomic`] types via the `compare_exchange` method by passing
126 /// [`Ordering::SeqCst`] as the `success` and [`Ordering::Acquire`] as the
127 /// `failure` parameters. For example, [`AtomicBool::compare_exchange`].
128 pub fn atomic_cxchg_failacq
<T
: Copy
>(dst
: *mut T
, old
: T
, src
: T
) -> (T
, bool
);
129 /// Stores a value if the current value is the same as the `old` value.
131 /// The stabilized version of this intrinsic is available on the
132 /// [`atomic`] types via the `compare_exchange` method by passing
133 /// [`Ordering::Acquire`] as the `success` and [`Ordering::Relaxed`] as the
134 /// `failure` parameters. For example, [`AtomicBool::compare_exchange`].
135 pub fn atomic_cxchg_acq_failrelaxed
<T
: Copy
>(dst
: *mut T
, old
: T
, src
: T
) -> (T
, bool
);
136 /// Stores a value if the current value is the same as the `old` value.
138 /// The stabilized version of this intrinsic is available on the
139 /// [`atomic`] types via the `compare_exchange` method by passing
140 /// [`Ordering::AcqRel`] as the `success` and [`Ordering::Relaxed`] as the
141 /// `failure` parameters. For example, [`AtomicBool::compare_exchange`].
142 pub fn atomic_cxchg_acqrel_failrelaxed
<T
: Copy
>(dst
: *mut T
, old
: T
, src
: T
) -> (T
, bool
);
144 /// Stores a value if the current value is the same as the `old` value.
146 /// The stabilized version of this intrinsic is available on the
147 /// [`atomic`] types via the `compare_exchange_weak` method by passing
148 /// [`Ordering::SeqCst`] as both the `success` and `failure` parameters.
149 /// For example, [`AtomicBool::compare_exchange_weak`].
150 pub fn atomic_cxchgweak
<T
: Copy
>(dst
: *mut T
, old
: T
, src
: T
) -> (T
, bool
);
151 /// Stores a value if the current value is the same as the `old` value.
153 /// The stabilized version of this intrinsic is available on the
154 /// [`atomic`] types via the `compare_exchange_weak` method by passing
155 /// [`Ordering::Acquire`] as both the `success` and `failure` parameters.
156 /// For example, [`AtomicBool::compare_exchange_weak`].
157 pub fn atomic_cxchgweak_acq
<T
: Copy
>(dst
: *mut T
, old
: T
, src
: T
) -> (T
, bool
);
158 /// Stores a value if the current value is the same as the `old` value.
160 /// The stabilized version of this intrinsic is available on the
161 /// [`atomic`] types via the `compare_exchange_weak` method by passing
162 /// [`Ordering::Release`] as the `success` and [`Ordering::Relaxed`] as the
163 /// `failure` parameters. For example, [`AtomicBool::compare_exchange_weak`].
164 pub fn atomic_cxchgweak_rel
<T
: Copy
>(dst
: *mut T
, old
: T
, src
: T
) -> (T
, bool
);
165 /// Stores a value if the current value is the same as the `old` value.
167 /// The stabilized version of this intrinsic is available on the
168 /// [`atomic`] types via the `compare_exchange_weak` method by passing
169 /// [`Ordering::AcqRel`] as the `success` and [`Ordering::Acquire`] as the
170 /// `failure` parameters. For example, [`AtomicBool::compare_exchange_weak`].
171 pub fn atomic_cxchgweak_acqrel
<T
: Copy
>(dst
: *mut T
, old
: T
, src
: T
) -> (T
, bool
);
172 /// Stores a value if the current value is the same as the `old` value.
174 /// The stabilized version of this intrinsic is available on the
175 /// [`atomic`] types via the `compare_exchange_weak` method by passing
176 /// [`Ordering::Relaxed`] as both the `success` and `failure` parameters.
177 /// For example, [`AtomicBool::compare_exchange_weak`].
178 pub fn atomic_cxchgweak_relaxed
<T
: Copy
>(dst
: *mut T
, old
: T
, src
: T
) -> (T
, bool
);
179 /// Stores a value if the current value is the same as the `old` value.
181 /// The stabilized version of this intrinsic is available on the
182 /// [`atomic`] types via the `compare_exchange_weak` method by passing
183 /// [`Ordering::SeqCst`] as the `success` and [`Ordering::Relaxed`] as the
184 /// `failure` parameters. For example, [`AtomicBool::compare_exchange_weak`].
185 pub fn atomic_cxchgweak_failrelaxed
<T
: Copy
>(dst
: *mut T
, old
: T
, src
: T
) -> (T
, bool
);
186 /// Stores a value if the current value is the same as the `old` value.
188 /// The stabilized version of this intrinsic is available on the
189 /// [`atomic`] types via the `compare_exchange_weak` method by passing
190 /// [`Ordering::SeqCst`] as the `success` and [`Ordering::Acquire`] as the
191 /// `failure` parameters. For example, [`AtomicBool::compare_exchange_weak`].
192 pub fn atomic_cxchgweak_failacq
<T
: Copy
>(dst
: *mut T
, old
: T
, src
: T
) -> (T
, bool
);
193 /// Stores a value if the current value is the same as the `old` value.
195 /// The stabilized version of this intrinsic is available on the
196 /// [`atomic`] types via the `compare_exchange_weak` method by passing
197 /// [`Ordering::Acquire`] as the `success` and [`Ordering::Relaxed`] as the
198 /// `failure` parameters. For example, [`AtomicBool::compare_exchange_weak`].
199 pub fn atomic_cxchgweak_acq_failrelaxed
<T
: Copy
>(dst
: *mut T
, old
: T
, src
: T
) -> (T
, bool
);
200 /// Stores a value if the current value is the same as the `old` value.
202 /// The stabilized version of this intrinsic is available on the
203 /// [`atomic`] types via the `compare_exchange_weak` method by passing
204 /// [`Ordering::AcqRel`] as the `success` and [`Ordering::Relaxed`] as the
205 /// `failure` parameters. For example, [`AtomicBool::compare_exchange_weak`].
206 pub fn atomic_cxchgweak_acqrel_failrelaxed
<T
: Copy
>(dst
: *mut T
, old
: T
, src
: T
) -> (T
, bool
);
208 /// Loads the current value of the pointer.
210 /// The stabilized version of this intrinsic is available on the
211 /// [`atomic`] types via the `load` method by passing
212 /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicBool::load`].
213 pub fn atomic_load
<T
: Copy
>(src
: *const T
) -> T
;
214 /// Loads the current value of the pointer.
216 /// The stabilized version of this intrinsic is available on the
217 /// [`atomic`] types via the `load` method by passing
218 /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicBool::load`].
219 pub fn atomic_load_acq
<T
: Copy
>(src
: *const T
) -> T
;
220 /// Loads the current value of the pointer.
222 /// The stabilized version of this intrinsic is available on the
223 /// [`atomic`] types via the `load` method by passing
224 /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicBool::load`].
225 pub fn atomic_load_relaxed
<T
: Copy
>(src
: *const T
) -> T
;
226 pub fn atomic_load_unordered
<T
: Copy
>(src
: *const T
) -> T
;
228 /// Stores the value at the specified memory location.
230 /// The stabilized version of this intrinsic is available on the
231 /// [`atomic`] types via the `store` method by passing
232 /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicBool::store`].
233 pub fn atomic_store
<T
: Copy
>(dst
: *mut T
, val
: T
);
234 /// Stores the value at the specified memory location.
236 /// The stabilized version of this intrinsic is available on the
237 /// [`atomic`] types via the `store` method by passing
238 /// [`Ordering::Release`] as the `order`. For example, [`AtomicBool::store`].
239 pub fn atomic_store_rel
<T
: Copy
>(dst
: *mut T
, val
: T
);
240 /// Stores the value at the specified memory location.
242 /// The stabilized version of this intrinsic is available on the
243 /// [`atomic`] types via the `store` method by passing
244 /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicBool::store`].
245 pub fn atomic_store_relaxed
<T
: Copy
>(dst
: *mut T
, val
: T
);
246 pub fn atomic_store_unordered
<T
: Copy
>(dst
: *mut T
, val
: T
);
248 /// Stores the value at the specified memory location, returning the old value.
250 /// The stabilized version of this intrinsic is available on the
251 /// [`atomic`] types via the `swap` method by passing
252 /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicBool::swap`].
253 pub fn atomic_xchg
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
254 /// Stores the value at the specified memory location, returning the old value.
256 /// The stabilized version of this intrinsic is available on the
257 /// [`atomic`] types via the `swap` method by passing
258 /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicBool::swap`].
259 pub fn atomic_xchg_acq
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
260 /// Stores the value at the specified memory location, returning the old value.
262 /// The stabilized version of this intrinsic is available on the
263 /// [`atomic`] types via the `swap` method by passing
264 /// [`Ordering::Release`] as the `order`. For example, [`AtomicBool::swap`].
265 pub fn atomic_xchg_rel
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
266 /// Stores the value at the specified memory location, returning the old value.
268 /// The stabilized version of this intrinsic is available on the
269 /// [`atomic`] types via the `swap` method by passing
270 /// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicBool::swap`].
271 pub fn atomic_xchg_acqrel
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
272 /// Stores the value at the specified memory location, returning the old value.
274 /// The stabilized version of this intrinsic is available on the
275 /// [`atomic`] types via the `swap` method by passing
276 /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicBool::swap`].
277 pub fn atomic_xchg_relaxed
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
279 /// Adds to the current value, returning the previous value.
281 /// The stabilized version of this intrinsic is available on the
282 /// [`atomic`] types via the `fetch_add` method by passing
283 /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicIsize::fetch_add`].
284 pub fn atomic_xadd
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
285 /// Adds to the current value, returning the previous value.
287 /// The stabilized version of this intrinsic is available on the
288 /// [`atomic`] types via the `fetch_add` method by passing
289 /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicIsize::fetch_add`].
290 pub fn atomic_xadd_acq
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
291 /// Adds to the current value, returning the previous value.
293 /// The stabilized version of this intrinsic is available on the
294 /// [`atomic`] types via the `fetch_add` method by passing
295 /// [`Ordering::Release`] as the `order`. For example, [`AtomicIsize::fetch_add`].
296 pub fn atomic_xadd_rel
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
297 /// Adds to the current value, returning the previous value.
299 /// The stabilized version of this intrinsic is available on the
300 /// [`atomic`] types via the `fetch_add` method by passing
301 /// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicIsize::fetch_add`].
302 pub fn atomic_xadd_acqrel
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
303 /// Adds to the current value, returning the previous value.
305 /// The stabilized version of this intrinsic is available on the
306 /// [`atomic`] types via the `fetch_add` method by passing
307 /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicIsize::fetch_add`].
308 pub fn atomic_xadd_relaxed
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
310 /// Subtract from the current value, returning the previous value.
312 /// The stabilized version of this intrinsic is available on the
313 /// [`atomic`] types via the `fetch_sub` method by passing
314 /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicIsize::fetch_sub`].
315 pub fn atomic_xsub
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
316 /// Subtract from the current value, returning the previous value.
318 /// The stabilized version of this intrinsic is available on the
319 /// [`atomic`] types via the `fetch_sub` method by passing
320 /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicIsize::fetch_sub`].
321 pub fn atomic_xsub_acq
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
322 /// Subtract from the current value, returning the previous value.
324 /// The stabilized version of this intrinsic is available on the
325 /// [`atomic`] types via the `fetch_sub` method by passing
326 /// [`Ordering::Release`] as the `order`. For example, [`AtomicIsize::fetch_sub`].
327 pub fn atomic_xsub_rel
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
328 /// Subtract from the current value, returning the previous value.
330 /// The stabilized version of this intrinsic is available on the
331 /// [`atomic`] types via the `fetch_sub` method by passing
332 /// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicIsize::fetch_sub`].
333 pub fn atomic_xsub_acqrel
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
334 /// Subtract from the current value, returning the previous value.
336 /// The stabilized version of this intrinsic is available on the
337 /// [`atomic`] types via the `fetch_sub` method by passing
338 /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicIsize::fetch_sub`].
339 pub fn atomic_xsub_relaxed
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
341 /// Bitwise and with the current value, returning the previous value.
343 /// The stabilized version of this intrinsic is available on the
344 /// [`atomic`] types via the `fetch_and` method by passing
345 /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicBool::fetch_and`].
346 pub fn atomic_and
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
347 /// Bitwise and with the current value, returning the previous value.
349 /// The stabilized version of this intrinsic is available on the
350 /// [`atomic`] types via the `fetch_and` method by passing
351 /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicBool::fetch_and`].
352 pub fn atomic_and_acq
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
353 /// Bitwise and with the current value, returning the previous value.
355 /// The stabilized version of this intrinsic is available on the
356 /// [`atomic`] types via the `fetch_and` method by passing
357 /// [`Ordering::Release`] as the `order`. For example, [`AtomicBool::fetch_and`].
358 pub fn atomic_and_rel
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
359 /// Bitwise and with the current value, returning the previous value.
361 /// The stabilized version of this intrinsic is available on the
362 /// [`atomic`] types via the `fetch_and` method by passing
363 /// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicBool::fetch_and`].
364 pub fn atomic_and_acqrel
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
365 /// Bitwise and with the current value, returning the previous value.
367 /// The stabilized version of this intrinsic is available on the
368 /// [`atomic`] types via the `fetch_and` method by passing
369 /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicBool::fetch_and`].
370 pub fn atomic_and_relaxed
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
372 /// Bitwise nand with the current value, returning the previous value.
374 /// The stabilized version of this intrinsic is available on the
375 /// [`AtomicBool`] type via the `fetch_nand` method by passing
376 /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicBool::fetch_nand`].
377 pub fn atomic_nand
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
378 /// Bitwise nand with the current value, returning the previous value.
380 /// The stabilized version of this intrinsic is available on the
381 /// [`AtomicBool`] type via the `fetch_nand` method by passing
382 /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicBool::fetch_nand`].
383 pub fn atomic_nand_acq
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
384 /// Bitwise nand with the current value, returning the previous value.
386 /// The stabilized version of this intrinsic is available on the
387 /// [`AtomicBool`] type via the `fetch_nand` method by passing
388 /// [`Ordering::Release`] as the `order`. For example, [`AtomicBool::fetch_nand`].
389 pub fn atomic_nand_rel
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
390 /// Bitwise nand with the current value, returning the previous value.
392 /// The stabilized version of this intrinsic is available on the
393 /// [`AtomicBool`] type via the `fetch_nand` method by passing
394 /// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicBool::fetch_nand`].
395 pub fn atomic_nand_acqrel
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
396 /// Bitwise nand with the current value, returning the previous value.
398 /// The stabilized version of this intrinsic is available on the
399 /// [`AtomicBool`] type via the `fetch_nand` method by passing
400 /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicBool::fetch_nand`].
401 pub fn atomic_nand_relaxed
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
403 /// Bitwise or with the current value, returning the previous value.
405 /// The stabilized version of this intrinsic is available on the
406 /// [`atomic`] types via the `fetch_or` method by passing
407 /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicBool::fetch_or`].
408 pub fn atomic_or
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
409 /// Bitwise or with the current value, returning the previous value.
411 /// The stabilized version of this intrinsic is available on the
412 /// [`atomic`] types via the `fetch_or` method by passing
413 /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicBool::fetch_or`].
414 pub fn atomic_or_acq
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
415 /// Bitwise or with the current value, returning the previous value.
417 /// The stabilized version of this intrinsic is available on the
418 /// [`atomic`] types via the `fetch_or` method by passing
419 /// [`Ordering::Release`] as the `order`. For example, [`AtomicBool::fetch_or`].
420 pub fn atomic_or_rel
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
421 /// Bitwise or with the current value, returning the previous value.
423 /// The stabilized version of this intrinsic is available on the
424 /// [`atomic`] types via the `fetch_or` method by passing
425 /// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicBool::fetch_or`].
426 pub fn atomic_or_acqrel
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
427 /// Bitwise or with the current value, returning the previous value.
429 /// The stabilized version of this intrinsic is available on the
430 /// [`atomic`] types via the `fetch_or` method by passing
431 /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicBool::fetch_or`].
432 pub fn atomic_or_relaxed
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
434 /// Bitwise xor with the current value, returning the previous value.
436 /// The stabilized version of this intrinsic is available on the
437 /// [`atomic`] types via the `fetch_xor` method by passing
438 /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicBool::fetch_xor`].
439 pub fn atomic_xor
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
440 /// Bitwise xor with the current value, returning the previous value.
442 /// The stabilized version of this intrinsic is available on the
443 /// [`atomic`] types via the `fetch_xor` method by passing
444 /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicBool::fetch_xor`].
445 pub fn atomic_xor_acq
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
446 /// Bitwise xor with the current value, returning the previous value.
448 /// The stabilized version of this intrinsic is available on the
449 /// [`atomic`] types via the `fetch_xor` method by passing
450 /// [`Ordering::Release`] as the `order`. For example, [`AtomicBool::fetch_xor`].
451 pub fn atomic_xor_rel
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
452 /// Bitwise xor with the current value, returning the previous value.
454 /// The stabilized version of this intrinsic is available on the
455 /// [`atomic`] types via the `fetch_xor` method by passing
456 /// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicBool::fetch_xor`].
457 pub fn atomic_xor_acqrel
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
458 /// Bitwise xor with the current value, returning the previous value.
460 /// The stabilized version of this intrinsic is available on the
461 /// [`atomic`] types via the `fetch_xor` method by passing
462 /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicBool::fetch_xor`].
463 pub fn atomic_xor_relaxed
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
465 /// Maximum with the current value using a signed comparison.
467 /// The stabilized version of this intrinsic is available on the
468 /// [`atomic`] signed integer types via the `fetch_max` method by passing
469 /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicI32::fetch_max`].
470 pub fn atomic_max
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
471 /// Maximum with the current value using a signed comparison.
473 /// The stabilized version of this intrinsic is available on the
474 /// [`atomic`] signed integer types via the `fetch_max` method by passing
475 /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicI32::fetch_max`].
476 pub fn atomic_max_acq
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
477 /// Maximum with the current value using a signed comparison.
479 /// The stabilized version of this intrinsic is available on the
480 /// [`atomic`] signed integer types via the `fetch_max` method by passing
481 /// [`Ordering::Release`] as the `order`. For example, [`AtomicI32::fetch_max`].
482 pub fn atomic_max_rel
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
483 /// Maximum with the current value using a signed comparison.
485 /// The stabilized version of this intrinsic is available on the
486 /// [`atomic`] signed integer types via the `fetch_max` method by passing
487 /// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicI32::fetch_max`].
488 pub fn atomic_max_acqrel
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
489 /// Maximum with the current value.
491 /// The stabilized version of this intrinsic is available on the
492 /// [`atomic`] signed integer types via the `fetch_max` method by passing
493 /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicI32::fetch_max`].
494 pub fn atomic_max_relaxed
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
496 /// Minimum with the current value using a signed comparison.
498 /// The stabilized version of this intrinsic is available on the
499 /// [`atomic`] signed integer types via the `fetch_min` method by passing
500 /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicI32::fetch_min`].
501 pub fn atomic_min
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
502 /// Minimum with the current value using a signed comparison.
504 /// The stabilized version of this intrinsic is available on the
505 /// [`atomic`] signed integer types via the `fetch_min` method by passing
506 /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicI32::fetch_min`].
507 pub fn atomic_min_acq
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
508 /// Minimum with the current value using a signed comparison.
510 /// The stabilized version of this intrinsic is available on the
511 /// [`atomic`] signed integer types via the `fetch_min` method by passing
512 /// [`Ordering::Release`] as the `order`. For example, [`AtomicI32::fetch_min`].
513 pub fn atomic_min_rel
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
514 /// Minimum with the current value using a signed comparison.
516 /// The stabilized version of this intrinsic is available on the
517 /// [`atomic`] signed integer types via the `fetch_min` method by passing
518 /// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicI32::fetch_min`].
519 pub fn atomic_min_acqrel
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
520 /// Minimum with the current value using a signed comparison.
522 /// The stabilized version of this intrinsic is available on the
523 /// [`atomic`] signed integer types via the `fetch_min` method by passing
524 /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicI32::fetch_min`].
525 pub fn atomic_min_relaxed
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
527 /// Minimum with the current value using an unsigned comparison.
529 /// The stabilized version of this intrinsic is available on the
530 /// [`atomic`] unsigned integer types via the `fetch_min` method by passing
531 /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicU32::fetch_min`].
532 pub fn atomic_umin
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
533 /// Minimum with the current value using an unsigned comparison.
535 /// The stabilized version of this intrinsic is available on the
536 /// [`atomic`] unsigned integer types via the `fetch_min` method by passing
537 /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicU32::fetch_min`].
538 pub fn atomic_umin_acq
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
539 /// Minimum with the current value using an unsigned comparison.
541 /// The stabilized version of this intrinsic is available on the
542 /// [`atomic`] unsigned integer types via the `fetch_min` method by passing
543 /// [`Ordering::Release`] as the `order`. For example, [`AtomicU32::fetch_min`].
544 pub fn atomic_umin_rel
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
545 /// Minimum with the current value using an unsigned comparison.
547 /// The stabilized version of this intrinsic is available on the
548 /// [`atomic`] unsigned integer types via the `fetch_min` method by passing
549 /// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicU32::fetch_min`].
550 pub fn atomic_umin_acqrel
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
551 /// Minimum with the current value using an unsigned comparison.
553 /// The stabilized version of this intrinsic is available on the
554 /// [`atomic`] unsigned integer types via the `fetch_min` method by passing
555 /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicU32::fetch_min`].
556 pub fn atomic_umin_relaxed
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
558 /// Maximum with the current value using an unsigned comparison.
560 /// The stabilized version of this intrinsic is available on the
561 /// [`atomic`] unsigned integer types via the `fetch_max` method by passing
562 /// [`Ordering::SeqCst`] as the `order`. For example, [`AtomicU32::fetch_max`].
563 pub fn atomic_umax
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
564 /// Maximum with the current value using an unsigned comparison.
566 /// The stabilized version of this intrinsic is available on the
567 /// [`atomic`] unsigned integer types via the `fetch_max` method by passing
568 /// [`Ordering::Acquire`] as the `order`. For example, [`AtomicU32::fetch_max`].
569 pub fn atomic_umax_acq
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
570 /// Maximum with the current value using an unsigned comparison.
572 /// The stabilized version of this intrinsic is available on the
573 /// [`atomic`] unsigned integer types via the `fetch_max` method by passing
574 /// [`Ordering::Release`] as the `order`. For example, [`AtomicU32::fetch_max`].
575 pub fn atomic_umax_rel
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
576 /// Maximum with the current value using an unsigned comparison.
578 /// The stabilized version of this intrinsic is available on the
579 /// [`atomic`] unsigned integer types via the `fetch_max` method by passing
580 /// [`Ordering::AcqRel`] as the `order`. For example, [`AtomicU32::fetch_max`].
581 pub fn atomic_umax_acqrel
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
582 /// Maximum with the current value using an unsigned comparison.
584 /// The stabilized version of this intrinsic is available on the
585 /// [`atomic`] unsigned integer types via the `fetch_max` method by passing
586 /// [`Ordering::Relaxed`] as the `order`. For example, [`AtomicU32::fetch_max`].
587 pub fn atomic_umax_relaxed
<T
: Copy
>(dst
: *mut T
, src
: T
) -> T
;
589 /// The `prefetch` intrinsic is a hint to the code generator to insert a prefetch instruction
590 /// if supported; otherwise, it is a no-op.
591 /// Prefetches have no effect on the behavior of the program but can change its performance
594 /// The `locality` argument must be a constant integer and is a temporal locality specifier
595 /// ranging from (0) - no locality, to (3) - extremely local keep in cache.
597 /// This intrinsic does not have a stable counterpart.
598 pub fn prefetch_read_data
<T
>(data
: *const T
, locality
: i32);
599 /// The `prefetch` intrinsic is a hint to the code generator to insert a prefetch instruction
600 /// if supported; otherwise, it is a no-op.
601 /// Prefetches have no effect on the behavior of the program but can change its performance
604 /// The `locality` argument must be a constant integer and is a temporal locality specifier
605 /// ranging from (0) - no locality, to (3) - extremely local keep in cache.
607 /// This intrinsic does not have a stable counterpart.
608 pub fn prefetch_write_data
<T
>(data
: *const T
, locality
: i32);
609 /// The `prefetch` intrinsic is a hint to the code generator to insert a prefetch instruction
610 /// if supported; otherwise, it is a no-op.
611 /// Prefetches have no effect on the behavior of the program but can change its performance
614 /// The `locality` argument must be a constant integer and is a temporal locality specifier
615 /// ranging from (0) - no locality, to (3) - extremely local keep in cache.
617 /// This intrinsic does not have a stable counterpart.
618 pub fn prefetch_read_instruction
<T
>(data
: *const T
, locality
: i32);
619 /// The `prefetch` intrinsic is a hint to the code generator to insert a prefetch instruction
620 /// if supported; otherwise, it is a no-op.
621 /// Prefetches have no effect on the behavior of the program but can change its performance
624 /// The `locality` argument must be a constant integer and is a temporal locality specifier
625 /// ranging from (0) - no locality, to (3) - extremely local keep in cache.
627 /// This intrinsic does not have a stable counterpart.
628 pub fn prefetch_write_instruction
<T
>(data
: *const T
, locality
: i32);
631 extern "rust-intrinsic" {
634 /// The stabilized version of this intrinsic is available in
635 /// [`atomic::fence`] by passing [`Ordering::SeqCst`]
637 pub fn atomic_fence();
640 /// The stabilized version of this intrinsic is available in
641 /// [`atomic::fence`] by passing [`Ordering::Acquire`]
643 pub fn atomic_fence_acq();
646 /// The stabilized version of this intrinsic is available in
647 /// [`atomic::fence`] by passing [`Ordering::Release`]
649 pub fn atomic_fence_rel();
652 /// The stabilized version of this intrinsic is available in
653 /// [`atomic::fence`] by passing [`Ordering::AcqRel`]
655 pub fn atomic_fence_acqrel();
657 /// A compiler-only memory barrier.
659 /// Memory accesses will never be reordered across this barrier by the
660 /// compiler, but no instructions will be emitted for it. This is
661 /// appropriate for operations on the same thread that may be preempted,
662 /// such as when interacting with signal handlers.
664 /// The stabilized version of this intrinsic is available in
665 /// [`atomic::compiler_fence`] by passing [`Ordering::SeqCst`]
667 pub fn atomic_singlethreadfence();
668 /// A compiler-only memory barrier.
670 /// Memory accesses will never be reordered across this barrier by the
671 /// compiler, but no instructions will be emitted for it. This is
672 /// appropriate for operations on the same thread that may be preempted,
673 /// such as when interacting with signal handlers.
675 /// The stabilized version of this intrinsic is available in
676 /// [`atomic::compiler_fence`] by passing [`Ordering::Acquire`]
678 pub fn atomic_singlethreadfence_acq();
679 /// A compiler-only memory barrier.
681 /// Memory accesses will never be reordered across this barrier by the
682 /// compiler, but no instructions will be emitted for it. This is
683 /// appropriate for operations on the same thread that may be preempted,
684 /// such as when interacting with signal handlers.
686 /// The stabilized version of this intrinsic is available in
687 /// [`atomic::compiler_fence`] by passing [`Ordering::Release`]
689 pub fn atomic_singlethreadfence_rel();
690 /// A compiler-only memory barrier.
692 /// Memory accesses will never be reordered across this barrier by the
693 /// compiler, but no instructions will be emitted for it. This is
694 /// appropriate for operations on the same thread that may be preempted,
695 /// such as when interacting with signal handlers.
697 /// The stabilized version of this intrinsic is available in
698 /// [`atomic::compiler_fence`] by passing [`Ordering::AcqRel`]
700 pub fn atomic_singlethreadfence_acqrel();
702 /// Magic intrinsic that derives its meaning from attributes
703 /// attached to the function.
705 /// For example, dataflow uses this to inject static assertions so
706 /// that `rustc_peek(potentially_uninitialized)` would actually
707 /// double-check that dataflow did indeed compute that it is
708 /// uninitialized at that point in the control flow.
710 /// This intrinsic should not be used outside of the compiler.
711 pub fn rustc_peek
<T
>(_
: T
) -> T
;
713 /// Aborts the execution of the process.
715 /// A more user-friendly and stable version of this operation is
716 /// [`std::process::abort`](../../std/process/fn.abort.html).
719 /// Informs the optimizer that this point in the code is not reachable,
720 /// enabling further optimizations.
722 /// N.B., this is very different from the `unreachable!()` macro: Unlike the
723 /// macro, which panics when it is executed, it is *undefined behavior* to
724 /// reach code marked with this function.
726 /// The stabilized version of this intrinsic is [`core::hint::unreachable_unchecked`](crate::hint::unreachable_unchecked).
727 #[rustc_const_unstable(feature = "const_unreachable_unchecked", issue = "53188")]
728 pub fn unreachable() -> !;
730 /// Informs the optimizer that a condition is always true.
731 /// If the condition is false, the behavior is undefined.
733 /// No code is generated for this intrinsic, but the optimizer will try
734 /// to preserve it (and its condition) between passes, which may interfere
735 /// with optimization of surrounding code and reduce performance. It should
736 /// not be used if the invariant can be discovered by the optimizer on its
737 /// own, or if it does not enable any significant optimizations.
739 /// This intrinsic does not have a stable counterpart.
740 #[rustc_const_unstable(feature = "const_assume", issue = "76972")]
741 pub fn assume(b
: bool
);
743 /// Hints to the compiler that branch condition is likely to be true.
744 /// Returns the value passed to it.
746 /// Any use other than with `if` statements will probably not have an effect.
748 /// This intrinsic does not have a stable counterpart.
749 #[rustc_const_unstable(feature = "const_likely", issue = "none")]
750 pub fn likely(b
: bool
) -> bool
;
752 /// Hints to the compiler that branch condition is likely to be false.
753 /// Returns the value passed to it.
755 /// Any use other than with `if` statements will probably not have an effect.
757 /// This intrinsic does not have a stable counterpart.
758 #[rustc_const_unstable(feature = "const_likely", issue = "none")]
759 pub fn unlikely(b
: bool
) -> bool
;
761 /// Executes a breakpoint trap, for inspection by a debugger.
763 /// This intrinsic does not have a stable counterpart.
766 /// The size of a type in bytes.
768 /// More specifically, this is the offset in bytes between successive
769 /// items of the same type, including alignment padding.
771 /// The stabilized version of this intrinsic is [`core::mem::size_of`](crate::mem::size_of).
772 #[rustc_const_stable(feature = "const_size_of", since = "1.40.0")]
773 pub fn size_of
<T
>() -> usize;
775 /// The minimum alignment of a type.
777 /// The stabilized version of this intrinsic is [`core::mem::align_of`](crate::mem::align_of).
778 #[rustc_const_stable(feature = "const_min_align_of", since = "1.40.0")]
779 pub fn min_align_of
<T
>() -> usize;
780 /// The preferred alignment of a type.
782 /// This intrinsic does not have a stable counterpart.
783 #[rustc_const_unstable(feature = "const_pref_align_of", issue = "none")]
784 pub fn pref_align_of
<T
>() -> usize;
786 /// The size of the referenced value in bytes.
788 /// The stabilized version of this intrinsic is [`mem::size_of_val`].
789 #[rustc_const_unstable(feature = "const_size_of_val", issue = "46571")]
790 pub fn size_of_val
<T
: ?Sized
>(_
: *const T
) -> usize;
791 /// The required alignment of the referenced value.
793 /// The stabilized version of this intrinsic is [`core::mem::align_of_val`](crate::mem::align_of_val).
794 #[rustc_const_unstable(feature = "const_align_of_val", issue = "46571")]
795 pub fn min_align_of_val
<T
: ?Sized
>(_
: *const T
) -> usize;
797 /// Gets a static string slice containing the name of a type.
799 /// The stabilized version of this intrinsic is [`core::any::type_name`](crate::any::type_name).
800 #[rustc_const_unstable(feature = "const_type_name", issue = "63084")]
801 pub fn type_name
<T
: ?Sized
>() -> &'
static str;
803 /// Gets an identifier which is globally unique to the specified type. This
804 /// function will return the same value for a type regardless of whichever
805 /// crate it is invoked in.
807 /// The stabilized version of this intrinsic is [`core::any::TypeId::of`](crate::any::TypeId::of).
808 #[rustc_const_unstable(feature = "const_type_id", issue = "77125")]
809 pub fn type_id
<T
: ?Sized
+ '
static>() -> u64;
811 /// A guard for unsafe functions that cannot ever be executed if `T` is uninhabited:
812 /// This will statically either panic, or do nothing.
814 /// This intrinsic does not have a stable counterpart.
815 #[rustc_const_unstable(feature = "const_assert_type", issue = "none")]
816 pub fn assert_inhabited
<T
>();
818 /// A guard for unsafe functions that cannot ever be executed if `T` does not permit
819 /// zero-initialization: This will statically either panic, or do nothing.
821 /// This intrinsic does not have a stable counterpart.
822 pub fn assert_zero_valid
<T
>();
824 /// A guard for unsafe functions that cannot ever be executed if `T` has invalid
825 /// bit patterns: This will statically either panic, or do nothing.
827 /// This intrinsic does not have a stable counterpart.
828 pub fn assert_uninit_valid
<T
>();
830 /// Gets a reference to a static `Location` indicating where it was called.
832 /// Consider using [`core::panic::Location::caller`](crate::panic::Location::caller) instead.
833 #[rustc_const_unstable(feature = "const_caller_location", issue = "76156")]
834 pub fn caller_location() -> &'
static crate::panic
::Location
<'
static>;
836 /// Moves a value out of scope without running drop glue.
838 /// This exists solely for [`mem::forget_unsized`]; normal `forget` uses
839 /// `ManuallyDrop` instead.
840 #[rustc_const_unstable(feature = "const_intrinsic_forget", issue = "none")]
841 pub fn forget
<T
: ?Sized
>(_
: T
);
843 /// Reinterprets the bits of a value of one type as another type.
845 /// Both types must have the same size. Neither the original, nor the result,
846 /// may be an [invalid value](../../nomicon/what-unsafe-does.html).
848 /// `transmute` is semantically equivalent to a bitwise move of one type
849 /// into another. It copies the bits from the source value into the
850 /// destination value, then forgets the original. It's equivalent to C's
851 /// `memcpy` under the hood, just like `transmute_copy`.
853 /// Because `transmute` is a by-value operation, alignment of the *transmuted values
854 /// themselves* is not a concern. As with any other function, the compiler already ensures
855 /// both `T` and `U` are properly aligned. However, when transmuting values that *point
856 /// elsewhere* (such as pointers, references, boxes…), the caller has to ensure proper
857 /// alignment of the pointed-to values.
859 /// `transmute` is **incredibly** unsafe. There are a vast number of ways to
860 /// cause [undefined behavior][ub] with this function. `transmute` should be
861 /// the absolute last resort.
863 /// The [nomicon](../../nomicon/transmutes.html) has additional
866 /// [ub]: ../../reference/behavior-considered-undefined.html
870 /// There are a few things that `transmute` is really useful for.
872 /// Turning a pointer into a function pointer. This is *not* portable to
873 /// machines where function pointers and data pointers have different sizes.
876 /// fn foo() -> i32 {
879 /// let pointer = foo as *const ();
880 /// let function = unsafe {
881 /// std::mem::transmute::<*const (), fn() -> i32>(pointer)
883 /// assert_eq!(function(), 0);
886 /// Extending a lifetime, or shortening an invariant lifetime. This is
887 /// advanced, very unsafe Rust!
890 /// struct R<'a>(&'a i32);
891 /// unsafe fn extend_lifetime<'b>(r: R<'b>) -> R<'static> {
892 /// std::mem::transmute::<R<'b>, R<'static>>(r)
895 /// unsafe fn shorten_invariant_lifetime<'b, 'c>(r: &'b mut R<'static>)
896 /// -> &'b mut R<'c> {
897 /// std::mem::transmute::<&'b mut R<'static>, &'b mut R<'c>>(r)
903 /// Don't despair: many uses of `transmute` can be achieved through other means.
904 /// Below are common applications of `transmute` which can be replaced with safer
907 /// Turning raw bytes(`&[u8]`) to `u32`, `f64`, etc.:
910 /// let raw_bytes = [0x78, 0x56, 0x34, 0x12];
912 /// let num = unsafe {
913 /// std::mem::transmute::<[u8; 4], u32>(raw_bytes)
916 /// // use `u32::from_ne_bytes` instead
917 /// let num = u32::from_ne_bytes(raw_bytes);
918 /// // or use `u32::from_le_bytes` or `u32::from_be_bytes` to specify the endianness
919 /// let num = u32::from_le_bytes(raw_bytes);
920 /// assert_eq!(num, 0x12345678);
921 /// let num = u32::from_be_bytes(raw_bytes);
922 /// assert_eq!(num, 0x78563412);
925 /// Turning a pointer into a `usize`:
929 /// let ptr_num_transmute = unsafe {
930 /// std::mem::transmute::<&i32, usize>(ptr)
933 /// // Use an `as` cast instead
934 /// let ptr_num_cast = ptr as *const i32 as usize;
937 /// Turning a `*mut T` into an `&mut T`:
940 /// let ptr: *mut i32 = &mut 0;
941 /// let ref_transmuted = unsafe {
942 /// std::mem::transmute::<*mut i32, &mut i32>(ptr)
945 /// // Use a reborrow instead
946 /// let ref_casted = unsafe { &mut *ptr };
949 /// Turning an `&mut T` into an `&mut U`:
952 /// let ptr = &mut 0;
953 /// let val_transmuted = unsafe {
954 /// std::mem::transmute::<&mut i32, &mut u32>(ptr)
957 /// // Now, put together `as` and reborrowing - note the chaining of `as`
958 /// // `as` is not transitive
959 /// let val_casts = unsafe { &mut *(ptr as *mut i32 as *mut u32) };
962 /// Turning an `&str` into an `&[u8]`:
965 /// // this is not a good way to do this.
966 /// let slice = unsafe { std::mem::transmute::<&str, &[u8]>("Rust") };
967 /// assert_eq!(slice, &[82, 117, 115, 116]);
969 /// // You could use `str::as_bytes`
970 /// let slice = "Rust".as_bytes();
971 /// assert_eq!(slice, &[82, 117, 115, 116]);
973 /// // Or, just use a byte string, if you have control over the string
975 /// assert_eq!(b"Rust", &[82, 117, 115, 116]);
978 /// Turning a `Vec<&T>` into a `Vec<Option<&T>>`.
980 /// To transmute the inner type of the contents of a container, you must make sure to not
981 /// violate any of the container's invariants. For `Vec`, this means that both the size
982 /// *and alignment* of the inner types have to match. Other containers might rely on the
983 /// size of the type, alignment, or even the `TypeId`, in which case transmuting wouldn't
984 /// be possible at all without violating the container invariants.
987 /// let store = [0, 1, 2, 3];
988 /// let v_orig = store.iter().collect::<Vec<&i32>>();
990 /// // clone the vector as we will reuse them later
991 /// let v_clone = v_orig.clone();
993 /// // Using transmute: this relies on the unspecified data layout of `Vec`, which is a
994 /// // bad idea and could cause Undefined Behavior.
995 /// // However, it is no-copy.
996 /// let v_transmuted = unsafe {
997 /// std::mem::transmute::<Vec<&i32>, Vec<Option<&i32>>>(v_clone)
1000 /// let v_clone = v_orig.clone();
1002 /// // This is the suggested, safe way.
1003 /// // It does copy the entire vector, though, into a new array.
1004 /// let v_collected = v_clone.into_iter()
1006 /// .collect::<Vec<Option<&i32>>>();
1008 /// let v_clone = v_orig.clone();
1010 /// // This is the proper no-copy, unsafe way of "transmuting" a `Vec`, without relying on the
1011 /// // data layout. Instead of literally calling `transmute`, we perform a pointer cast, but
1012 /// // in terms of converting the original inner type (`&i32`) to the new one (`Option<&i32>`),
1013 /// // this has all the same caveats. Besides the information provided above, also consult the
1014 /// // [`from_raw_parts`] documentation.
1015 /// let v_from_raw = unsafe {
1016 // FIXME Update this when vec_into_raw_parts is stabilized
1017 /// // Ensure the original vector is not dropped.
1018 /// let mut v_clone = std::mem::ManuallyDrop::new(v_clone);
1019 /// Vec::from_raw_parts(v_clone.as_mut_ptr() as *mut Option<&i32>,
1021 /// v_clone.capacity())
1025 /// [`from_raw_parts`]: ../../std/vec/struct.Vec.html#method.from_raw_parts
1027 /// Implementing `split_at_mut`:
1030 /// use std::{slice, mem};
1032 /// // There are multiple ways to do this, and there are multiple problems
1033 /// // with the following (transmute) way.
1034 /// fn split_at_mut_transmute<T>(slice: &mut [T], mid: usize)
1035 /// -> (&mut [T], &mut [T]) {
1036 /// let len = slice.len();
1037 /// assert!(mid <= len);
1039 /// let slice2 = mem::transmute::<&mut [T], &mut [T]>(slice);
1040 /// // first: transmute is not type safe; all it checks is that T and
1041 /// // U are of the same size. Second, right here, you have two
1042 /// // mutable references pointing to the same memory.
1043 /// (&mut slice[0..mid], &mut slice2[mid..len])
1047 /// // This gets rid of the type safety problems; `&mut *` will *only* give
1048 /// // you an `&mut T` from an `&mut T` or `*mut T`.
1049 /// fn split_at_mut_casts<T>(slice: &mut [T], mid: usize)
1050 /// -> (&mut [T], &mut [T]) {
1051 /// let len = slice.len();
1052 /// assert!(mid <= len);
1054 /// let slice2 = &mut *(slice as *mut [T]);
1055 /// // however, you still have two mutable references pointing to
1056 /// // the same memory.
1057 /// (&mut slice[0..mid], &mut slice2[mid..len])
1061 /// // This is how the standard library does it. This is the best method, if
1062 /// // you need to do something like this
1063 /// fn split_at_stdlib<T>(slice: &mut [T], mid: usize)
1064 /// -> (&mut [T], &mut [T]) {
1065 /// let len = slice.len();
1066 /// assert!(mid <= len);
1068 /// let ptr = slice.as_mut_ptr();
1069 /// // This now has three mutable references pointing at the same
1070 /// // memory. `slice`, the rvalue ret.0, and the rvalue ret.1.
1071 /// // `slice` is never used after `let ptr = ...`, and so one can
1072 /// // treat it as "dead", and therefore, you only have two real
1073 /// // mutable slices.
1074 /// (slice::from_raw_parts_mut(ptr, mid),
1075 /// slice::from_raw_parts_mut(ptr.add(mid), len - mid))
1079 #[stable(feature = "rust1", since = "1.0.0")]
1080 // NOTE: While this makes the intrinsic const stable, we have some custom code in const fn
1081 // checks that prevent its use within `const fn`.
1082 #[rustc_const_stable(feature = "const_transmute", since = "1.46.0")]
1083 #[rustc_diagnostic_item = "transmute"]
1084 pub fn transmute
<T
, U
>(e
: T
) -> U
;
1086 /// Returns `true` if the actual type given as `T` requires drop
1087 /// glue; returns `false` if the actual type provided for `T`
1088 /// implements `Copy`.
1090 /// If the actual type neither requires drop glue nor implements
1091 /// `Copy`, then the return value of this function is unspecified.
1093 /// The stabilized version of this intrinsic is [`mem::needs_drop`](crate::mem::needs_drop).
1094 #[rustc_const_stable(feature = "const_needs_drop", since = "1.40.0")]
1095 pub fn needs_drop
<T
>() -> bool
;
1097 /// Calculates the offset from a pointer.
1099 /// This is implemented as an intrinsic to avoid converting to and from an
1100 /// integer, since the conversion would throw away aliasing information.
1104 /// Both the starting and resulting pointer must be either in bounds or one
1105 /// byte past the end of an allocated object. If either pointer is out of
1106 /// bounds or arithmetic overflow occurs then any further use of the
1107 /// returned value will result in undefined behavior.
1109 /// The stabilized version of this intrinsic is [`pointer::offset`].
1110 #[must_use = "returns a new pointer rather than modifying its argument"]
1111 #[rustc_const_unstable(feature = "const_ptr_offset", issue = "71499")]
1112 pub fn offset
<T
>(dst
: *const T
, offset
: isize) -> *const T
;
1114 /// Calculates the offset from a pointer, potentially wrapping.
1116 /// This is implemented as an intrinsic to avoid converting to and from an
1117 /// integer, since the conversion inhibits certain optimizations.
1121 /// Unlike the `offset` intrinsic, this intrinsic does not restrict the
1122 /// resulting pointer to point into or one byte past the end of an allocated
1123 /// object, and it wraps with two's complement arithmetic. The resulting
1124 /// value is not necessarily valid to be used to actually access memory.
1126 /// The stabilized version of this intrinsic is [`pointer::wrapping_offset`].
1127 #[must_use = "returns a new pointer rather than modifying its argument"]
1128 #[rustc_const_unstable(feature = "const_ptr_offset", issue = "71499")]
1129 pub fn arith_offset
<T
>(dst
: *const T
, offset
: isize) -> *const T
;
1131 /// Equivalent to the appropriate `llvm.memcpy.p0i8.0i8.*` intrinsic, with
1132 /// a size of `count` * `size_of::<T>()` and an alignment of
1133 /// `min_align_of::<T>()`
1135 /// The volatile parameter is set to `true`, so it will not be optimized out
1136 /// unless size is equal to zero.
1138 /// This intrinsic does not have a stable counterpart.
1139 pub fn volatile_copy_nonoverlapping_memory
<T
>(dst
: *mut T
, src
: *const T
, count
: usize);
1140 /// Equivalent to the appropriate `llvm.memmove.p0i8.0i8.*` intrinsic, with
1141 /// a size of `count * size_of::<T>()` and an alignment of
1142 /// `min_align_of::<T>()`
1144 /// The volatile parameter is set to `true`, so it will not be optimized out
1145 /// unless size is equal to zero.
1147 /// This intrinsic does not have a stable counterpart.
1148 pub fn volatile_copy_memory
<T
>(dst
: *mut T
, src
: *const T
, count
: usize);
1149 /// Equivalent to the appropriate `llvm.memset.p0i8.*` intrinsic, with a
1150 /// size of `count * size_of::<T>()` and an alignment of
1151 /// `min_align_of::<T>()`.
1153 /// The volatile parameter is set to `true`, so it will not be optimized out
1154 /// unless size is equal to zero.
1156 /// This intrinsic does not have a stable counterpart.
1157 pub fn volatile_set_memory
<T
>(dst
: *mut T
, val
: u8, count
: usize);
1159 /// Performs a volatile load from the `src` pointer.
1161 /// The stabilized version of this intrinsic is [`core::ptr::read_volatile`](crate::ptr::read_volatile).
1162 pub fn volatile_load
<T
>(src
: *const T
) -> T
;
1163 /// Performs a volatile store to the `dst` pointer.
1165 /// The stabilized version of this intrinsic is [`core::ptr::write_volatile`](crate::ptr::write_volatile).
1166 pub fn volatile_store
<T
>(dst
: *mut T
, val
: T
);
1168 /// Performs a volatile load from the `src` pointer
1169 /// The pointer is not required to be aligned.
1171 /// This intrinsic does not have a stable counterpart.
1172 pub fn unaligned_volatile_load
<T
>(src
: *const T
) -> T
;
1173 /// Performs a volatile store to the `dst` pointer.
1174 /// The pointer is not required to be aligned.
1176 /// This intrinsic does not have a stable counterpart.
1177 pub fn unaligned_volatile_store
<T
>(dst
: *mut T
, val
: T
);
1179 /// Returns the square root of an `f32`
1181 /// The stabilized version of this intrinsic is
1182 /// [`f32::sqrt`](../../std/primitive.f32.html#method.sqrt)
1183 pub fn sqrtf32(x
: f32) -> f32;
1184 /// Returns the square root of an `f64`
1186 /// The stabilized version of this intrinsic is
1187 /// [`f64::sqrt`](../../std/primitive.f64.html#method.sqrt)
1188 pub fn sqrtf64(x
: f64) -> f64;
1190 /// Raises an `f32` to an integer power.
1192 /// The stabilized version of this intrinsic is
1193 /// [`f32::powi`](../../std/primitive.f32.html#method.powi)
1194 pub fn powif32(a
: f32, x
: i32) -> f32;
1195 /// Raises an `f64` to an integer power.
1197 /// The stabilized version of this intrinsic is
1198 /// [`f64::powi`](../../std/primitive.f64.html#method.powi)
1199 pub fn powif64(a
: f64, x
: i32) -> f64;
1201 /// Returns the sine of an `f32`.
1203 /// The stabilized version of this intrinsic is
1204 /// [`f32::sin`](../../std/primitive.f32.html#method.sin)
1205 pub fn sinf32(x
: f32) -> f32;
1206 /// Returns the sine of an `f64`.
1208 /// The stabilized version of this intrinsic is
1209 /// [`f64::sin`](../../std/primitive.f64.html#method.sin)
1210 pub fn sinf64(x
: f64) -> f64;
1212 /// Returns the cosine of an `f32`.
1214 /// The stabilized version of this intrinsic is
1215 /// [`f32::cos`](../../std/primitive.f32.html#method.cos)
1216 pub fn cosf32(x
: f32) -> f32;
1217 /// Returns the cosine of an `f64`.
1219 /// The stabilized version of this intrinsic is
1220 /// [`f64::cos`](../../std/primitive.f64.html#method.cos)
1221 pub fn cosf64(x
: f64) -> f64;
1223 /// Raises an `f32` to an `f32` power.
1225 /// The stabilized version of this intrinsic is
1226 /// [`f32::powf`](../../std/primitive.f32.html#method.powf)
1227 pub fn powf32(a
: f32, x
: f32) -> f32;
1228 /// Raises an `f64` to an `f64` power.
1230 /// The stabilized version of this intrinsic is
1231 /// [`f64::powf`](../../std/primitive.f64.html#method.powf)
1232 pub fn powf64(a
: f64, x
: f64) -> f64;
1234 /// Returns the exponential of an `f32`.
1236 /// The stabilized version of this intrinsic is
1237 /// [`f32::exp`](../../std/primitive.f32.html#method.exp)
1238 pub fn expf32(x
: f32) -> f32;
1239 /// Returns the exponential of an `f64`.
1241 /// The stabilized version of this intrinsic is
1242 /// [`f64::exp`](../../std/primitive.f64.html#method.exp)
1243 pub fn expf64(x
: f64) -> f64;
1245 /// Returns 2 raised to the power of an `f32`.
1247 /// The stabilized version of this intrinsic is
1248 /// [`f32::exp2`](../../std/primitive.f32.html#method.exp2)
1249 pub fn exp2f32(x
: f32) -> f32;
1250 /// Returns 2 raised to the power of an `f64`.
1252 /// The stabilized version of this intrinsic is
1253 /// [`f64::exp2`](../../std/primitive.f64.html#method.exp2)
1254 pub fn exp2f64(x
: f64) -> f64;
1256 /// Returns the natural logarithm of an `f32`.
1258 /// The stabilized version of this intrinsic is
1259 /// [`f32::ln`](../../std/primitive.f32.html#method.ln)
1260 pub fn logf32(x
: f32) -> f32;
1261 /// Returns the natural logarithm of an `f64`.
1263 /// The stabilized version of this intrinsic is
1264 /// [`f64::ln`](../../std/primitive.f64.html#method.ln)
1265 pub fn logf64(x
: f64) -> f64;
1267 /// Returns the base 10 logarithm of an `f32`.
1269 /// The stabilized version of this intrinsic is
1270 /// [`f32::log10`](../../std/primitive.f32.html#method.log10)
1271 pub fn log10f32(x
: f32) -> f32;
1272 /// Returns the base 10 logarithm of an `f64`.
1274 /// The stabilized version of this intrinsic is
1275 /// [`f64::log10`](../../std/primitive.f64.html#method.log10)
1276 pub fn log10f64(x
: f64) -> f64;
1278 /// Returns the base 2 logarithm of an `f32`.
1280 /// The stabilized version of this intrinsic is
1281 /// [`f32::log2`](../../std/primitive.f32.html#method.log2)
1282 pub fn log2f32(x
: f32) -> f32;
1283 /// Returns the base 2 logarithm of an `f64`.
1285 /// The stabilized version of this intrinsic is
1286 /// [`f64::log2`](../../std/primitive.f64.html#method.log2)
1287 pub fn log2f64(x
: f64) -> f64;
1289 /// Returns `a * b + c` for `f32` values.
1291 /// The stabilized version of this intrinsic is
1292 /// [`f32::mul_add`](../../std/primitive.f32.html#method.mul_add)
1293 pub fn fmaf32(a
: f32, b
: f32, c
: f32) -> f32;
1294 /// Returns `a * b + c` for `f64` values.
1296 /// The stabilized version of this intrinsic is
1297 /// [`f64::mul_add`](../../std/primitive.f64.html#method.mul_add)
1298 pub fn fmaf64(a
: f64, b
: f64, c
: f64) -> f64;
1300 /// Returns the absolute value of an `f32`.
1302 /// The stabilized version of this intrinsic is
1303 /// [`f32::abs`](../../std/primitive.f32.html#method.abs)
1304 pub fn fabsf32(x
: f32) -> f32;
1305 /// Returns the absolute value of an `f64`.
1307 /// The stabilized version of this intrinsic is
1308 /// [`f64::abs`](../../std/primitive.f64.html#method.abs)
1309 pub fn fabsf64(x
: f64) -> f64;
1311 /// Returns the minimum of two `f32` values.
1313 /// The stabilized version of this intrinsic is
1315 pub fn minnumf32(x
: f32, y
: f32) -> f32;
1316 /// Returns the minimum of two `f64` values.
1318 /// The stabilized version of this intrinsic is
1320 pub fn minnumf64(x
: f64, y
: f64) -> f64;
1321 /// Returns the maximum of two `f32` values.
1323 /// The stabilized version of this intrinsic is
1325 pub fn maxnumf32(x
: f32, y
: f32) -> f32;
1326 /// Returns the maximum of two `f64` values.
1328 /// The stabilized version of this intrinsic is
1330 pub fn maxnumf64(x
: f64, y
: f64) -> f64;
1332 /// Copies the sign from `y` to `x` for `f32` values.
1334 /// The stabilized version of this intrinsic is
1335 /// [`f32::copysign`](../../std/primitive.f32.html#method.copysign)
1336 pub fn copysignf32(x
: f32, y
: f32) -> f32;
1337 /// Copies the sign from `y` to `x` for `f64` values.
1339 /// The stabilized version of this intrinsic is
1340 /// [`f64::copysign`](../../std/primitive.f64.html#method.copysign)
1341 pub fn copysignf64(x
: f64, y
: f64) -> f64;
1343 /// Returns the largest integer less than or equal to an `f32`.
1345 /// The stabilized version of this intrinsic is
1346 /// [`f32::floor`](../../std/primitive.f32.html#method.floor)
1347 pub fn floorf32(x
: f32) -> f32;
1348 /// Returns the largest integer less than or equal to an `f64`.
1350 /// The stabilized version of this intrinsic is
1351 /// [`f64::floor`](../../std/primitive.f64.html#method.floor)
1352 pub fn floorf64(x
: f64) -> f64;
1354 /// Returns the smallest integer greater than or equal to an `f32`.
1356 /// The stabilized version of this intrinsic is
1357 /// [`f32::ceil`](../../std/primitive.f32.html#method.ceil)
1358 pub fn ceilf32(x
: f32) -> f32;
1359 /// Returns the smallest integer greater than or equal to an `f64`.
1361 /// The stabilized version of this intrinsic is
1362 /// [`f64::ceil`](../../std/primitive.f64.html#method.ceil)
1363 pub fn ceilf64(x
: f64) -> f64;
1365 /// Returns the integer part of an `f32`.
1367 /// The stabilized version of this intrinsic is
1368 /// [`f32::trunc`](../../std/primitive.f32.html#method.trunc)
1369 pub fn truncf32(x
: f32) -> f32;
1370 /// Returns the integer part of an `f64`.
1372 /// The stabilized version of this intrinsic is
1373 /// [`f64::trunc`](../../std/primitive.f64.html#method.trunc)
1374 pub fn truncf64(x
: f64) -> f64;
1376 /// Returns the nearest integer to an `f32`. May raise an inexact floating-point exception
1377 /// if the argument is not an integer.
1378 pub fn rintf32(x
: f32) -> f32;
1379 /// Returns the nearest integer to an `f64`. May raise an inexact floating-point exception
1380 /// if the argument is not an integer.
1381 pub fn rintf64(x
: f64) -> f64;
1383 /// Returns the nearest integer to an `f32`.
1385 /// This intrinsic does not have a stable counterpart.
1386 pub fn nearbyintf32(x
: f32) -> f32;
1387 /// Returns the nearest integer to an `f64`.
1389 /// This intrinsic does not have a stable counterpart.
1390 pub fn nearbyintf64(x
: f64) -> f64;
1392 /// Returns the nearest integer to an `f32`. Rounds half-way cases away from zero.
1394 /// The stabilized version of this intrinsic is
1395 /// [`f32::round`](../../std/primitive.f32.html#method.round)
1396 pub fn roundf32(x
: f32) -> f32;
1397 /// Returns the nearest integer to an `f64`. Rounds half-way cases away from zero.
1399 /// The stabilized version of this intrinsic is
1400 /// [`f64::round`](../../std/primitive.f64.html#method.round)
1401 pub fn roundf64(x
: f64) -> f64;
1403 /// Float addition that allows optimizations based on algebraic rules.
1404 /// May assume inputs are finite.
1406 /// This intrinsic does not have a stable counterpart.
1407 pub fn fadd_fast
<T
: Copy
>(a
: T
, b
: T
) -> T
;
1409 /// Float subtraction that allows optimizations based on algebraic rules.
1410 /// May assume inputs are finite.
1412 /// This intrinsic does not have a stable counterpart.
1413 pub fn fsub_fast
<T
: Copy
>(a
: T
, b
: T
) -> T
;
1415 /// Float multiplication that allows optimizations based on algebraic rules.
1416 /// May assume inputs are finite.
1418 /// This intrinsic does not have a stable counterpart.
1419 pub fn fmul_fast
<T
: Copy
>(a
: T
, b
: T
) -> T
;
1421 /// Float division that allows optimizations based on algebraic rules.
1422 /// May assume inputs are finite.
1424 /// This intrinsic does not have a stable counterpart.
1425 pub fn fdiv_fast
<T
: Copy
>(a
: T
, b
: T
) -> T
;
1427 /// Float remainder that allows optimizations based on algebraic rules.
1428 /// May assume inputs are finite.
1430 /// This intrinsic does not have a stable counterpart.
1431 pub fn frem_fast
<T
: Copy
>(a
: T
, b
: T
) -> T
;
1433 /// Convert with LLVM’s fptoui/fptosi, which may return undef for values out of range
1434 /// (<https://github.com/rust-lang/rust/issues/10184>)
1436 /// Stabilized as [`f32::to_int_unchecked`] and [`f64::to_int_unchecked`].
1437 pub fn float_to_int_unchecked
<Float
: Copy
, Int
: Copy
>(value
: Float
) -> Int
;
1439 /// Returns the number of bits set in an integer type `T`
1441 /// The stabilized versions of this intrinsic are available on the integer
1442 /// primitives via the `count_ones` method. For example,
1443 /// [`u32::count_ones`]
1444 #[rustc_const_stable(feature = "const_ctpop", since = "1.40.0")]
1445 pub fn ctpop
<T
: Copy
>(x
: T
) -> T
;
1447 /// Returns the number of leading unset bits (zeroes) in an integer type `T`.
1449 /// The stabilized versions of this intrinsic are available on the integer
1450 /// primitives via the `leading_zeros` method. For example,
1451 /// [`u32::leading_zeros`]
1456 /// #![feature(core_intrinsics)]
1458 /// use std::intrinsics::ctlz;
1460 /// let x = 0b0001_1100_u8;
1461 /// let num_leading = ctlz(x);
1462 /// assert_eq!(num_leading, 3);
1465 /// An `x` with value `0` will return the bit width of `T`.
1468 /// #![feature(core_intrinsics)]
1470 /// use std::intrinsics::ctlz;
1473 /// let num_leading = ctlz(x);
1474 /// assert_eq!(num_leading, 16);
1476 #[rustc_const_stable(feature = "const_ctlz", since = "1.40.0")]
1477 pub fn ctlz
<T
: Copy
>(x
: T
) -> T
;
1479 /// Like `ctlz`, but extra-unsafe as it returns `undef` when
1480 /// given an `x` with value `0`.
1482 /// This intrinsic does not have a stable counterpart.
1487 /// #![feature(core_intrinsics)]
1489 /// use std::intrinsics::ctlz_nonzero;
1491 /// let x = 0b0001_1100_u8;
1492 /// let num_leading = unsafe { ctlz_nonzero(x) };
1493 /// assert_eq!(num_leading, 3);
1495 #[rustc_const_stable(feature = "constctlz", since = "1.50.0")]
1496 pub fn ctlz_nonzero
<T
: Copy
>(x
: T
) -> T
;
1498 /// Returns the number of trailing unset bits (zeroes) in an integer type `T`.
1500 /// The stabilized versions of this intrinsic are available on the integer
1501 /// primitives via the `trailing_zeros` method. For example,
1502 /// [`u32::trailing_zeros`]
1507 /// #![feature(core_intrinsics)]
1509 /// use std::intrinsics::cttz;
1511 /// let x = 0b0011_1000_u8;
1512 /// let num_trailing = cttz(x);
1513 /// assert_eq!(num_trailing, 3);
1516 /// An `x` with value `0` will return the bit width of `T`:
1519 /// #![feature(core_intrinsics)]
1521 /// use std::intrinsics::cttz;
1524 /// let num_trailing = cttz(x);
1525 /// assert_eq!(num_trailing, 16);
1527 #[rustc_const_stable(feature = "const_cttz", since = "1.40.0")]
1528 pub fn cttz
<T
: Copy
>(x
: T
) -> T
;
1530 /// Like `cttz`, but extra-unsafe as it returns `undef` when
1531 /// given an `x` with value `0`.
1533 /// This intrinsic does not have a stable counterpart.
1538 /// #![feature(core_intrinsics)]
1540 /// use std::intrinsics::cttz_nonzero;
1542 /// let x = 0b0011_1000_u8;
1543 /// let num_trailing = unsafe { cttz_nonzero(x) };
1544 /// assert_eq!(num_trailing, 3);
1546 #[rustc_const_unstable(feature = "const_cttz", issue = "none")]
1547 pub fn cttz_nonzero
<T
: Copy
>(x
: T
) -> T
;
1549 /// Reverses the bytes in an integer type `T`.
1551 /// The stabilized versions of this intrinsic are available on the integer
1552 /// primitives via the `swap_bytes` method. For example,
1553 /// [`u32::swap_bytes`]
1554 #[rustc_const_stable(feature = "const_bswap", since = "1.40.0")]
1555 pub fn bswap
<T
: Copy
>(x
: T
) -> T
;
1557 /// Reverses the bits in an integer type `T`.
1559 /// The stabilized versions of this intrinsic are available on the integer
1560 /// primitives via the `reverse_bits` method. For example,
1561 /// [`u32::reverse_bits`]
1562 #[rustc_const_stable(feature = "const_bitreverse", since = "1.40.0")]
1563 pub fn bitreverse
<T
: Copy
>(x
: T
) -> T
;
1565 /// Performs checked integer addition.
1567 /// The stabilized versions of this intrinsic are available on the integer
1568 /// primitives via the `overflowing_add` method. For example,
1569 /// [`u32::overflowing_add`]
1570 #[rustc_const_stable(feature = "const_int_overflow", since = "1.40.0")]
1571 pub fn add_with_overflow
<T
: Copy
>(x
: T
, y
: T
) -> (T
, bool
);
1573 /// Performs checked integer subtraction
1575 /// The stabilized versions of this intrinsic are available on the integer
1576 /// primitives via the `overflowing_sub` method. For example,
1577 /// [`u32::overflowing_sub`]
1578 #[rustc_const_stable(feature = "const_int_overflow", since = "1.40.0")]
1579 pub fn sub_with_overflow
<T
: Copy
>(x
: T
, y
: T
) -> (T
, bool
);
1581 /// Performs checked integer multiplication
1583 /// The stabilized versions of this intrinsic are available on the integer
1584 /// primitives via the `overflowing_mul` method. For example,
1585 /// [`u32::overflowing_mul`]
1586 #[rustc_const_stable(feature = "const_int_overflow", since = "1.40.0")]
1587 pub fn mul_with_overflow
<T
: Copy
>(x
: T
, y
: T
) -> (T
, bool
);
1589 /// Performs an exact division, resulting in undefined behavior where
1590 /// `x % y != 0` or `y == 0` or `x == T::MIN && y == -1`
1592 /// This intrinsic does not have a stable counterpart.
1593 pub fn exact_div
<T
: Copy
>(x
: T
, y
: T
) -> T
;
1595 /// Performs an unchecked division, resulting in undefined behavior
1596 /// where `y == 0` or `x == T::MIN && y == -1`
1598 /// Safe wrappers for this intrinsic are available on the integer
1599 /// primitives via the `checked_div` method. For example,
1600 /// [`u32::checked_div`]
1601 #[rustc_const_stable(feature = "const_int_unchecked_arith", since = "1.52.0")]
1602 pub fn unchecked_div
<T
: Copy
>(x
: T
, y
: T
) -> T
;
1603 /// Returns the remainder of an unchecked division, resulting in
1604 /// undefined behavior when `y == 0` or `x == T::MIN && y == -1`
1606 /// Safe wrappers for this intrinsic are available on the integer
1607 /// primitives via the `checked_rem` method. For example,
1608 /// [`u32::checked_rem`]
1609 #[rustc_const_stable(feature = "const_int_unchecked_arith", since = "1.52.0")]
1610 pub fn unchecked_rem
<T
: Copy
>(x
: T
, y
: T
) -> T
;
1612 /// Performs an unchecked left shift, resulting in undefined behavior when
1613 /// `y < 0` or `y >= N`, where N is the width of T in bits.
1615 /// Safe wrappers for this intrinsic are available on the integer
1616 /// primitives via the `checked_shl` method. For example,
1617 /// [`u32::checked_shl`]
1618 #[rustc_const_stable(feature = "const_int_unchecked", since = "1.40.0")]
1619 pub fn unchecked_shl
<T
: Copy
>(x
: T
, y
: T
) -> T
;
1620 /// Performs an unchecked right shift, resulting in undefined behavior when
1621 /// `y < 0` or `y >= N`, where N is the width of T in bits.
1623 /// Safe wrappers for this intrinsic are available on the integer
1624 /// primitives via the `checked_shr` method. For example,
1625 /// [`u32::checked_shr`]
1626 #[rustc_const_stable(feature = "const_int_unchecked", since = "1.40.0")]
1627 pub fn unchecked_shr
<T
: Copy
>(x
: T
, y
: T
) -> T
;
1629 /// Returns the result of an unchecked addition, resulting in
1630 /// undefined behavior when `x + y > T::MAX` or `x + y < T::MIN`.
1632 /// This intrinsic does not have a stable counterpart.
1633 #[rustc_const_unstable(feature = "const_int_unchecked_arith", issue = "none")]
1634 pub fn unchecked_add
<T
: Copy
>(x
: T
, y
: T
) -> T
;
1636 /// Returns the result of an unchecked subtraction, resulting in
1637 /// undefined behavior when `x - y > T::MAX` or `x - y < T::MIN`.
1639 /// This intrinsic does not have a stable counterpart.
1640 #[rustc_const_unstable(feature = "const_int_unchecked_arith", issue = "none")]
1641 pub fn unchecked_sub
<T
: Copy
>(x
: T
, y
: T
) -> T
;
1643 /// Returns the result of an unchecked multiplication, resulting in
1644 /// undefined behavior when `x * y > T::MAX` or `x * y < T::MIN`.
1646 /// This intrinsic does not have a stable counterpart.
1647 #[rustc_const_unstable(feature = "const_int_unchecked_arith", issue = "none")]
1648 pub fn unchecked_mul
<T
: Copy
>(x
: T
, y
: T
) -> T
;
1650 /// Performs rotate left.
1652 /// The stabilized versions of this intrinsic are available on the integer
1653 /// primitives via the `rotate_left` method. For example,
1654 /// [`u32::rotate_left`]
1655 #[rustc_const_stable(feature = "const_int_rotate", since = "1.40.0")]
1656 pub fn rotate_left
<T
: Copy
>(x
: T
, y
: T
) -> T
;
1658 /// Performs rotate right.
1660 /// The stabilized versions of this intrinsic are available on the integer
1661 /// primitives via the `rotate_right` method. For example,
1662 /// [`u32::rotate_right`]
1663 #[rustc_const_stable(feature = "const_int_rotate", since = "1.40.0")]
1664 pub fn rotate_right
<T
: Copy
>(x
: T
, y
: T
) -> T
;
1666 /// Returns (a + b) mod 2<sup>N</sup>, where N is the width of T in bits.
1668 /// The stabilized versions of this intrinsic are available on the integer
1669 /// primitives via the `wrapping_add` method. For example,
1670 /// [`u32::wrapping_add`]
1671 #[rustc_const_stable(feature = "const_int_wrapping", since = "1.40.0")]
1672 pub fn wrapping_add
<T
: Copy
>(a
: T
, b
: T
) -> T
;
1673 /// Returns (a - b) mod 2<sup>N</sup>, where N is the width of T in bits.
1675 /// The stabilized versions of this intrinsic are available on the integer
1676 /// primitives via the `wrapping_sub` method. For example,
1677 /// [`u32::wrapping_sub`]
1678 #[rustc_const_stable(feature = "const_int_wrapping", since = "1.40.0")]
1679 pub fn wrapping_sub
<T
: Copy
>(a
: T
, b
: T
) -> T
;
1680 /// Returns (a * b) mod 2<sup>N</sup>, where N is the width of T in bits.
1682 /// The stabilized versions of this intrinsic are available on the integer
1683 /// primitives via the `wrapping_mul` method. For example,
1684 /// [`u32::wrapping_mul`]
1685 #[rustc_const_stable(feature = "const_int_wrapping", since = "1.40.0")]
1686 pub fn wrapping_mul
<T
: Copy
>(a
: T
, b
: T
) -> T
;
1688 /// Computes `a + b`, saturating at numeric bounds.
1690 /// The stabilized versions of this intrinsic are available on the integer
1691 /// primitives via the `saturating_add` method. For example,
1692 /// [`u32::saturating_add`]
1693 #[rustc_const_stable(feature = "const_int_saturating", since = "1.40.0")]
1694 pub fn saturating_add
<T
: Copy
>(a
: T
, b
: T
) -> T
;
1695 /// Computes `a - b`, saturating at numeric bounds.
1697 /// The stabilized versions of this intrinsic are available on the integer
1698 /// primitives via the `saturating_sub` method. For example,
1699 /// [`u32::saturating_sub`]
1700 #[rustc_const_stable(feature = "const_int_saturating", since = "1.40.0")]
1701 pub fn saturating_sub
<T
: Copy
>(a
: T
, b
: T
) -> T
;
1703 /// Returns the value of the discriminant for the variant in 'v';
1704 /// if `T` has no discriminant, returns `0`.
1706 /// The stabilized version of this intrinsic is [`core::mem::discriminant`](crate::mem::discriminant).
1707 #[rustc_const_unstable(feature = "const_discriminant", issue = "69821")]
1708 pub fn discriminant_value
<T
>(v
: &T
) -> <T
as DiscriminantKind
>::Discriminant
;
1710 /// Returns the number of variants of the type `T` cast to a `usize`;
1711 /// if `T` has no variants, returns `0`. Uninhabited variants will be counted.
1713 /// The to-be-stabilized version of this intrinsic is [`mem::variant_count`].
1714 #[rustc_const_unstable(feature = "variant_count", issue = "73662")]
1715 pub fn variant_count
<T
>() -> usize;
1717 /// Rust's "try catch" construct which invokes the function pointer `try_fn`
1718 /// with the data pointer `data`.
1720 /// The third argument is a function called if a panic occurs. This function
1721 /// takes the data pointer and a pointer to the target-specific exception
1722 /// object that was caught. For more information see the compiler's
1723 /// source as well as std's catch implementation.
1724 pub fn r
#try(try_fn: fn(*mut u8), data: *mut u8, catch_fn: fn(*mut u8, *mut u8)) -> i32;
1726 /// Emits a `!nontemporal` store according to LLVM (see their docs).
1727 /// Probably will never become stable.
1728 pub fn nontemporal_store
<T
>(ptr
: *mut T
, val
: T
);
1730 /// See documentation of `<*const T>::offset_from` for details.
1731 #[rustc_const_unstable(feature = "const_ptr_offset_from", issue = "41079")]
1732 pub fn ptr_offset_from
<T
>(ptr
: *const T
, base
: *const T
) -> isize;
1734 /// See documentation of `<*const T>::guaranteed_eq` for details.
1735 #[rustc_const_unstable(feature = "const_raw_ptr_comparison", issue = "53020")]
1736 pub fn ptr_guaranteed_eq
<T
>(ptr
: *const T
, other
: *const T
) -> bool
;
1738 /// See documentation of `<*const T>::guaranteed_ne` for details.
1739 #[rustc_const_unstable(feature = "const_raw_ptr_comparison", issue = "53020")]
1740 pub fn ptr_guaranteed_ne
<T
>(ptr
: *const T
, other
: *const T
) -> bool
;
1742 /// Allocate at compile time. Should not be called at runtime.
1743 #[rustc_const_unstable(feature = "const_heap", issue = "79597")]
1744 pub fn const_allocate(size
: usize, align
: usize) -> *mut u8;
1746 /// Copies `count * size_of::<T>()` bytes from `src` to `dst`. The source
1747 /// and destination must *not* overlap.
1749 /// For regions of memory which might overlap, use [`copy`] instead.
1751 /// `copy_nonoverlapping` is semantically equivalent to C's [`memcpy`], but
1752 /// with the argument order swapped.
1754 /// [`memcpy`]: https://en.cppreference.com/w/c/string/byte/memcpy
1758 /// Behavior is undefined if any of the following conditions are violated:
1760 /// * `src` must be [valid] for reads of `count * size_of::<T>()` bytes.
1762 /// * `dst` must be [valid] for writes of `count * size_of::<T>()` bytes.
1764 /// * Both `src` and `dst` must be properly aligned.
1766 /// * The region of memory beginning at `src` with a size of `count *
1767 /// size_of::<T>()` bytes must *not* overlap with the region of memory
1768 /// beginning at `dst` with the same size.
1770 /// Like [`read`], `copy_nonoverlapping` creates a bitwise copy of `T`, regardless of
1771 /// whether `T` is [`Copy`]. If `T` is not [`Copy`], using *both* the values
1772 /// in the region beginning at `*src` and the region beginning at `*dst` can
1773 /// [violate memory safety][read-ownership].
1775 /// Note that even if the effectively copied size (`count * size_of::<T>()`) is
1776 /// `0`, the pointers must be non-NULL and properly aligned.
1778 /// [`read`]: crate::ptr::read
1779 /// [read-ownership]: crate::ptr::read#ownership-of-the-returned-value
1780 /// [valid]: crate::ptr#safety
1784 /// Manually implement [`Vec::append`]:
1789 /// /// Moves all the elements of `src` into `dst`, leaving `src` empty.
1790 /// fn append<T>(dst: &mut Vec<T>, src: &mut Vec<T>) {
1791 /// let src_len = src.len();
1792 /// let dst_len = dst.len();
1794 /// // Ensure that `dst` has enough capacity to hold all of `src`.
1795 /// dst.reserve(src_len);
1798 /// // The call to offset is always safe because `Vec` will never
1799 /// // allocate more than `isize::MAX` bytes.
1800 /// let dst_ptr = dst.as_mut_ptr().offset(dst_len as isize);
1801 /// let src_ptr = src.as_ptr();
1803 /// // Truncate `src` without dropping its contents. We do this first,
1804 /// // to avoid problems in case something further down panics.
1807 /// // The two regions cannot overlap because mutable references do
1808 /// // not alias, and two different vectors cannot own the same
1810 /// ptr::copy_nonoverlapping(src_ptr, dst_ptr, src_len);
1812 /// // Notify `dst` that it now holds the contents of `src`.
1813 /// dst.set_len(dst_len + src_len);
1817 /// let mut a = vec!['r'];
1818 /// let mut b = vec!['u', 's', 't'];
1820 /// append(&mut a, &mut b);
1822 /// assert_eq!(a, &['r', 'u', 's', 't']);
1823 /// assert!(b.is_empty());
1826 /// [`Vec::append`]: ../../std/vec/struct.Vec.html#method.append
1827 #[doc(alias = "memcpy")]
1828 #[stable(feature = "rust1", since = "1.0.0")]
1829 #[rustc_const_unstable(feature = "const_intrinsic_copy", issue = "80697")]
1830 pub fn copy_nonoverlapping
<T
>(src
: *const T
, dst
: *mut T
, count
: usize);
1832 /// Copies `count * size_of::<T>()` bytes from `src` to `dst`. The source
1833 /// and destination may overlap.
1835 /// If the source and destination will *never* overlap,
1836 /// [`copy_nonoverlapping`] can be used instead.
1838 /// `copy` is semantically equivalent to C's [`memmove`], but with the argument
1839 /// order swapped. Copying takes place as if the bytes were copied from `src`
1840 /// to a temporary array and then copied from the array to `dst`.
1842 /// [`memmove`]: https://en.cppreference.com/w/c/string/byte/memmove
1846 /// Behavior is undefined if any of the following conditions are violated:
1848 /// * `src` must be [valid] for reads of `count * size_of::<T>()` bytes.
1850 /// * `dst` must be [valid] for writes of `count * size_of::<T>()` bytes.
1852 /// * Both `src` and `dst` must be properly aligned.
1854 /// Like [`read`], `copy` creates a bitwise copy of `T`, regardless of
1855 /// whether `T` is [`Copy`]. If `T` is not [`Copy`], using both the values
1856 /// in the region beginning at `*src` and the region beginning at `*dst` can
1857 /// [violate memory safety][read-ownership].
1859 /// Note that even if the effectively copied size (`count * size_of::<T>()`) is
1860 /// `0`, the pointers must be non-NULL and properly aligned.
1862 /// [`read`]: crate::ptr::read
1863 /// [read-ownership]: crate::ptr::read#ownership-of-the-returned-value
1864 /// [valid]: crate::ptr#safety
1868 /// Efficiently create a Rust vector from an unsafe buffer:
1875 /// /// * `ptr` must be correctly aligned for its type and non-zero.
1876 /// /// * `ptr` must be valid for reads of `elts` contiguous elements of type `T`.
1877 /// /// * Those elements must not be used after calling this function unless `T: Copy`.
1878 /// # #[allow(dead_code)]
1879 /// unsafe fn from_buf_raw<T>(ptr: *const T, elts: usize) -> Vec<T> {
1880 /// let mut dst = Vec::with_capacity(elts);
1882 /// // SAFETY: Our precondition ensures the source is aligned and valid,
1883 /// // and `Vec::with_capacity` ensures that we have usable space to write them.
1884 /// ptr::copy(ptr, dst.as_mut_ptr(), elts);
1886 /// // SAFETY: We created it with this much capacity earlier,
1887 /// // and the previous `copy` has initialized these elements.
1888 /// dst.set_len(elts);
1892 #[doc(alias = "memmove")]
1893 #[stable(feature = "rust1", since = "1.0.0")]
1894 #[rustc_const_unstable(feature = "const_intrinsic_copy", issue = "80697")]
1895 pub fn copy
<T
>(src
: *const T
, dst
: *mut T
, count
: usize);
1898 // Some functions are defined here because they accidentally got made
1899 // available in this module on stable. See <https://github.com/rust-lang/rust/issues/15702>.
1900 // (`transmute` also falls into this category, but it cannot be wrapped due to the
1901 // check that `T` and `U` have the same size.)
1903 /// Checks whether `ptr` is properly aligned with respect to
1904 /// `align_of::<T>()`.
1905 pub(crate) fn is_aligned_and_not_null
<T
>(ptr
: *const T
) -> bool
{
1906 !ptr
.is_null() && ptr
as usize % mem
::align_of
::<T
>() == 0
1909 /// Sets `count * size_of::<T>()` bytes of memory starting at `dst` to
1912 /// `write_bytes` is similar to C's [`memset`], but sets `count *
1913 /// size_of::<T>()` bytes to `val`.
1915 /// [`memset`]: https://en.cppreference.com/w/c/string/byte/memset
1919 /// Behavior is undefined if any of the following conditions are violated:
1921 /// * `dst` must be [valid] for writes of `count * size_of::<T>()` bytes.
1923 /// * `dst` must be properly aligned.
1925 /// Additionally, the caller must ensure that writing `count *
1926 /// size_of::<T>()` bytes to the given region of memory results in a valid
1927 /// value of `T`. Using a region of memory typed as a `T` that contains an
1928 /// invalid value of `T` is undefined behavior.
1930 /// Note that even if the effectively copied size (`count * size_of::<T>()`) is
1931 /// `0`, the pointer must be non-NULL and properly aligned.
1933 /// [valid]: crate::ptr#safety
1942 /// let mut vec = vec![0u32; 4];
1944 /// let vec_ptr = vec.as_mut_ptr();
1945 /// ptr::write_bytes(vec_ptr, 0xfe, 2);
1947 /// assert_eq!(vec, [0xfefefefe, 0xfefefefe, 0, 0]);
1950 /// Creating an invalid value:
1955 /// let mut v = Box::new(0i32);
1958 /// // Leaks the previously held value by overwriting the `Box<T>` with
1959 /// // a null pointer.
1960 /// ptr::write_bytes(&mut v as *mut Box<i32>, 0, 1);
1963 /// // At this point, using or dropping `v` results in undefined behavior.
1964 /// // drop(v); // ERROR
1966 /// // Even leaking `v` "uses" it, and hence is undefined behavior.
1967 /// // mem::forget(v); // ERROR
1969 /// // In fact, `v` is invalid according to basic type layout invariants, so *any*
1970 /// // operation touching it is undefined behavior.
1971 /// // let v2 = v; // ERROR
1974 /// // Let us instead put in a valid value
1975 /// ptr::write(&mut v as *mut Box<i32>, Box::new(42i32));
1978 /// // Now the box is fine
1979 /// assert_eq!(*v, 42);
1981 #[stable(feature = "rust1", since = "1.0.0")]
1983 pub unsafe fn write_bytes
<T
>(dst
: *mut T
, val
: u8, count
: usize) {
1984 extern "rust-intrinsic" {
1985 fn write_bytes
<T
>(dst
: *mut T
, val
: u8, count
: usize);
1988 debug_assert
!(is_aligned_and_not_null(dst
), "attempt to write to unaligned or null pointer");
1990 // SAFETY: the safety contract for `write_bytes` must be upheld by the caller.
1991 unsafe { write_bytes(dst, val, count) }