1 // Copyright 2013 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! rustc compiler intrinsics.
13 //! The corresponding definitions are in librustc_codegen_llvm/intrinsic.rs.
17 //! The volatile intrinsics provide operations intended to act on I/O
18 //! memory, which are guaranteed to not be reordered by the compiler
19 //! across other volatile intrinsics. See the LLVM documentation on
22 //! [volatile]: http://llvm.org/docs/LangRef.html#volatile-memory-accesses
26 //! The atomic intrinsics provide common atomic operations on machine
27 //! words, with multiple possible memory orderings. They obey the same
28 //! semantics as C++11. See the LLVM documentation on [[atomics]].
30 //! [atomics]: http://llvm.org/docs/Atomics.html
32 //! A quick refresher on memory ordering:
34 //! * Acquire - a barrier for acquiring a lock. Subsequent reads and writes
35 //! take place after the barrier.
36 //! * Release - a barrier for releasing a lock. Preceding reads and writes
37 //! take place before the barrier.
38 //! * Sequentially consistent - sequentially consistent operations are
39 //! guaranteed to happen in order. This is the standard mode for working
40 //! with atomic types and is equivalent to Java's `volatile`.
42 #![unstable(feature = "core_intrinsics",
43 reason = "intrinsics are unlikely to ever be stabilized, instead \
44 they should be used through stabilized interfaces \
45 in the rest of the standard library",
47 #![allow(missing_docs)]
49 #[stable(feature = "drop_in_place", since = "1.8.0")]
50 #[rustc_deprecated(reason = "no longer an intrinsic - use `ptr::drop_in_place` directly",
52 pub use ptr::drop_in_place;
54 extern "rust-intrinsic" {
55 // NB: These intrinsics take raw pointers because they mutate aliased
56 // memory, which is not valid for either `&` or `&mut`.
58 /// Stores a value if the current value is the same as the `old` value.
59 /// The stabilized version of this intrinsic is available on the
60 /// `std::sync::atomic` types via the `compare_exchange` method by passing
61 /// [`Ordering::SeqCst`](../../std/sync/atomic/enum.Ordering.html)
62 /// as both the `success` and `failure` parameters. For example,
63 /// [`AtomicBool::compare_exchange`][compare_exchange].
65 /// [compare_exchange]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange
66 pub fn atomic_cxchg<T>(dst: *mut T, old: T, src: T) -> (T, bool);
67 /// Stores a value if the current value is the same as the `old` value.
68 /// The stabilized version of this intrinsic is available on the
69 /// `std::sync::atomic` types via the `compare_exchange` method by passing
70 /// [`Ordering::Acquire`](../../std/sync/atomic/enum.Ordering.html)
71 /// as both the `success` and `failure` parameters. For example,
72 /// [`AtomicBool::compare_exchange`][compare_exchange].
74 /// [compare_exchange]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange
75 pub fn atomic_cxchg_acq<T>(dst: *mut T, old: T, src: T) -> (T, bool);
76 /// Stores a value if the current value is the same as the `old` value.
77 /// The stabilized version of this intrinsic is available on the
78 /// `std::sync::atomic` types via the `compare_exchange` method by passing
79 /// [`Ordering::Release`](../../std/sync/atomic/enum.Ordering.html)
80 /// as the `success` and
81 /// [`Ordering::Relaxed`](../../std/sync/atomic/enum.Ordering.html)
82 /// as the `failure` parameters. For example,
83 /// [`AtomicBool::compare_exchange`][compare_exchange].
85 /// [compare_exchange]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange
86 pub fn atomic_cxchg_rel<T>(dst: *mut T, old: T, src: T) -> (T, bool);
87 /// Stores a value if the current value is the same as the `old` value.
88 /// The stabilized version of this intrinsic is available on the
89 /// `std::sync::atomic` types via the `compare_exchange` method by passing
90 /// [`Ordering::AcqRel`](../../std/sync/atomic/enum.Ordering.html)
91 /// as the `success` and
92 /// [`Ordering::Acquire`](../../std/sync/atomic/enum.Ordering.html)
93 /// as the `failure` parameters. For example,
94 /// [`AtomicBool::compare_exchange`][compare_exchange].
96 /// [compare_exchange]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange
97 pub fn atomic_cxchg_acqrel<T>(dst: *mut T, old: T, src: T) -> (T, bool);
98 /// Stores a value if the current value is the same as the `old` value.
99 /// The stabilized version of this intrinsic is available on the
100 /// `std::sync::atomic` types via the `compare_exchange` method by passing
101 /// [`Ordering::Relaxed`](../../std/sync/atomic/enum.Ordering.html)
102 /// as both the `success` and `failure` parameters. For example,
103 /// [`AtomicBool::compare_exchange`][compare_exchange].
105 /// [compare_exchange]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange
106 pub fn atomic_cxchg_relaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool);
107 /// 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 /// `std::sync::atomic` types via the `compare_exchange` method by passing
110 /// [`Ordering::SeqCst`](../../std/sync/atomic/enum.Ordering.html)
111 /// as the `success` and
112 /// [`Ordering::Relaxed`](../../std/sync/atomic/enum.Ordering.html)
113 /// as the `failure` parameters. For example,
114 /// [`AtomicBool::compare_exchange`][compare_exchange].
116 /// [compare_exchange]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange
117 pub fn atomic_cxchg_failrelaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool);
118 /// Stores a value if the current value is the same as the `old` value.
119 /// The stabilized version of this intrinsic is available on the
120 /// `std::sync::atomic` types via the `compare_exchange` method by passing
121 /// [`Ordering::SeqCst`](../../std/sync/atomic/enum.Ordering.html)
122 /// as the `success` and
123 /// [`Ordering::Acquire`](../../std/sync/atomic/enum.Ordering.html)
124 /// as the `failure` parameters. For example,
125 /// [`AtomicBool::compare_exchange`][compare_exchange].
127 /// [compare_exchange]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange
128 pub fn atomic_cxchg_failacq<T>(dst: *mut T, old: T, src: T) -> (T, bool);
129 /// Stores a value if the current value is the same as the `old` value.
130 /// The stabilized version of this intrinsic is available on the
131 /// `std::sync::atomic` types via the `compare_exchange` method by passing
132 /// [`Ordering::Acquire`](../../std/sync/atomic/enum.Ordering.html)
133 /// as the `success` and
134 /// [`Ordering::Relaxed`](../../std/sync/atomic/enum.Ordering.html)
135 /// as the `failure` parameters. For example,
136 /// [`AtomicBool::compare_exchange`][compare_exchange].
138 /// [compare_exchange]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange
139 pub fn atomic_cxchg_acq_failrelaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool);
140 /// Stores a value if the current value is the same as the `old` value.
141 /// The stabilized version of this intrinsic is available on the
142 /// `std::sync::atomic` types via the `compare_exchange` method by passing
143 /// [`Ordering::AcqRel`](../../std/sync/atomic/enum.Ordering.html)
144 /// as the `success` and
145 /// [`Ordering::Relaxed`](../../std/sync/atomic/enum.Ordering.html)
146 /// as the `failure` parameters. For example,
147 /// [`AtomicBool::compare_exchange`][compare_exchange].
149 /// [compare_exchange]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange
150 pub fn atomic_cxchg_acqrel_failrelaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool);
152 /// 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 /// `std::sync::atomic` types via the `compare_exchange_weak` method by passing
155 /// [`Ordering::SeqCst`](../../std/sync/atomic/enum.Ordering.html)
156 /// as both the `success` and `failure` parameters. For example,
157 /// [`AtomicBool::compare_exchange_weak`][cew].
159 /// [cew]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange_weak
160 pub fn atomic_cxchgweak<T>(dst: *mut T, old: T, src: T) -> (T, bool);
161 /// Stores a value if the current value is the same as the `old` value.
162 /// The stabilized version of this intrinsic is available on the
163 /// `std::sync::atomic` types via the `compare_exchange_weak` method by passing
164 /// [`Ordering::Acquire`](../../std/sync/atomic/enum.Ordering.html)
165 /// as both the `success` and `failure` parameters. For example,
166 /// [`AtomicBool::compare_exchange_weak`][cew].
168 /// [cew]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange_weak
169 pub fn atomic_cxchgweak_acq<T>(dst: *mut T, old: T, src: T) -> (T, bool);
170 /// 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 /// `std::sync::atomic` types via the `compare_exchange_weak` method by passing
173 /// [`Ordering::Release`](../../std/sync/atomic/enum.Ordering.html)
174 /// as the `success` and
175 /// [`Ordering::Relaxed`](../../std/sync/atomic/enum.Ordering.html)
176 /// as the `failure` parameters. For example,
177 /// [`AtomicBool::compare_exchange_weak`][cew].
179 /// [cew]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange_weak
180 pub fn atomic_cxchgweak_rel<T>(dst: *mut T, old: T, src: T) -> (T, bool);
181 /// Stores a value if the current value is the same as the `old` value.
182 /// The stabilized version of this intrinsic is available on the
183 /// `std::sync::atomic` types via the `compare_exchange_weak` method by passing
184 /// [`Ordering::AcqRel`](../../std/sync/atomic/enum.Ordering.html)
185 /// as the `success` and
186 /// [`Ordering::Acquire`](../../std/sync/atomic/enum.Ordering.html)
187 /// as the `failure` parameters. For example,
188 /// [`AtomicBool::compare_exchange_weak`][cew].
190 /// [cew]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange_weak
191 pub fn atomic_cxchgweak_acqrel<T>(dst: *mut T, old: T, src: T) -> (T, bool);
192 /// 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 /// `std::sync::atomic` types via the `compare_exchange_weak` method by passing
195 /// [`Ordering::Relaxed`](../../std/sync/atomic/enum.Ordering.html)
196 /// as both the `success` and `failure` parameters. For example,
197 /// [`AtomicBool::compare_exchange_weak`][cew].
199 /// [cew]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange_weak
200 pub fn atomic_cxchgweak_relaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool);
201 /// 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 /// `std::sync::atomic` types via the `compare_exchange_weak` method by passing
204 /// [`Ordering::SeqCst`](../../std/sync/atomic/enum.Ordering.html)
205 /// as the `success` and
206 /// [`Ordering::Relaxed`](../../std/sync/atomic/enum.Ordering.html)
207 /// as the `failure` parameters. For example,
208 /// [`AtomicBool::compare_exchange_weak`][cew].
210 /// [cew]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange_weak
211 pub fn atomic_cxchgweak_failrelaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool);
212 /// Stores a value if the current value is the same as the `old` value.
213 /// The stabilized version of this intrinsic is available on the
214 /// `std::sync::atomic` types via the `compare_exchange_weak` method by passing
215 /// [`Ordering::SeqCst`](../../std/sync/atomic/enum.Ordering.html)
216 /// as the `success` and
217 /// [`Ordering::Acquire`](../../std/sync/atomic/enum.Ordering.html)
218 /// as the `failure` parameters. For example,
219 /// [`AtomicBool::compare_exchange_weak`][cew].
221 /// [cew]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange_weak
222 pub fn atomic_cxchgweak_failacq<T>(dst: *mut T, old: T, src: T) -> (T, bool);
223 /// Stores a value if the current value is the same as the `old` value.
224 /// The stabilized version of this intrinsic is available on the
225 /// `std::sync::atomic` types via the `compare_exchange_weak` method by passing
226 /// [`Ordering::Acquire`](../../std/sync/atomic/enum.Ordering.html)
227 /// as the `success` and
228 /// [`Ordering::Relaxed`](../../std/sync/atomic/enum.Ordering.html)
229 /// as the `failure` parameters. For example,
230 /// [`AtomicBool::compare_exchange_weak`][cew].
232 /// [cew]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange_weak
233 pub fn atomic_cxchgweak_acq_failrelaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool);
234 /// 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 /// `std::sync::atomic` types via the `compare_exchange_weak` method by passing
237 /// [`Ordering::AcqRel`](../../std/sync/atomic/enum.Ordering.html)
238 /// as the `success` and
239 /// [`Ordering::Relaxed`](../../std/sync/atomic/enum.Ordering.html)
240 /// as the `failure` parameters. For example,
241 /// [`AtomicBool::compare_exchange_weak`][cew].
243 /// [cew]: ../../std/sync/atomic/struct.AtomicBool.html#method.compare_exchange_weak
244 pub fn atomic_cxchgweak_acqrel_failrelaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool);
246 /// Loads the current value of the pointer.
247 /// The stabilized version of this intrinsic is available on the
248 /// `std::sync::atomic` types via the `load` method by passing
249 /// [`Ordering::SeqCst`](../../std/sync/atomic/enum.Ordering.html)
250 /// as the `order`. For example,
251 /// [`AtomicBool::load`](../../std/sync/atomic/struct.AtomicBool.html#method.load).
252 pub fn atomic_load<T>(src: *const T) -> T;
253 /// Loads the current value of the pointer.
254 /// The stabilized version of this intrinsic is available on the
255 /// `std::sync::atomic` types via the `load` method by passing
256 /// [`Ordering::Acquire`](../../std/sync/atomic/enum.Ordering.html)
257 /// as the `order`. For example,
258 /// [`AtomicBool::load`](../../std/sync/atomic/struct.AtomicBool.html#method.load).
259 pub fn atomic_load_acq<T>(src: *const T) -> T;
260 /// Loads the current value of the pointer.
261 /// The stabilized version of this intrinsic is available on the
262 /// `std::sync::atomic` types via the `load` method by passing
263 /// [`Ordering::Relaxed`](../../std/sync/atomic/enum.Ordering.html)
264 /// as the `order`. For example,
265 /// [`AtomicBool::load`](../../std/sync/atomic/struct.AtomicBool.html#method.load).
266 pub fn atomic_load_relaxed<T>(src: *const T) -> T;
267 pub fn atomic_load_unordered<T>(src: *const T) -> T;
269 /// Stores the value at the specified memory location.
270 /// The stabilized version of this intrinsic is available on the
271 /// `std::sync::atomic` types via the `store` method by passing
272 /// [`Ordering::SeqCst`](../../std/sync/atomic/enum.Ordering.html)
273 /// as the `order`. For example,
274 /// [`AtomicBool::store`](../../std/sync/atomic/struct.AtomicBool.html#method.store).
275 pub fn atomic_store<T>(dst: *mut T, val: T);
276 /// Stores the value at the specified memory location.
277 /// The stabilized version of this intrinsic is available on the
278 /// `std::sync::atomic` types via the `store` method by passing
279 /// [`Ordering::Release`](../../std/sync/atomic/enum.Ordering.html)
280 /// as the `order`. For example,
281 /// [`AtomicBool::store`](../../std/sync/atomic/struct.AtomicBool.html#method.store).
282 pub fn atomic_store_rel<T>(dst: *mut T, val: T);
283 /// Stores the value at the specified memory location.
284 /// The stabilized version of this intrinsic is available on the
285 /// `std::sync::atomic` types via the `store` method by passing
286 /// [`Ordering::Relaxed`](../../std/sync/atomic/enum.Ordering.html)
287 /// as the `order`. For example,
288 /// [`AtomicBool::store`](../../std/sync/atomic/struct.AtomicBool.html#method.store).
289 pub fn atomic_store_relaxed<T>(dst: *mut T, val: T);
290 pub fn atomic_store_unordered<T>(dst: *mut T, val: T);
292 /// Stores the value at the specified memory location, returning the old value.
293 /// The stabilized version of this intrinsic is available on the
294 /// `std::sync::atomic` types via the `swap` method by passing
295 /// [`Ordering::SeqCst`](../../std/sync/atomic/enum.Ordering.html)
296 /// as the `order`. For example,
297 /// [`AtomicBool::swap`](../../std/sync/atomic/struct.AtomicBool.html#method.swap).
298 pub fn atomic_xchg<T>(dst: *mut T, src: T) -> T;
299 /// Stores the value at the specified memory location, returning the old value.
300 /// The stabilized version of this intrinsic is available on the
301 /// `std::sync::atomic` types via the `swap` method by passing
302 /// [`Ordering::Acquire`](../../std/sync/atomic/enum.Ordering.html)
303 /// as the `order`. For example,
304 /// [`AtomicBool::swap`](../../std/sync/atomic/struct.AtomicBool.html#method.swap).
305 pub fn atomic_xchg_acq<T>(dst: *mut T, src: T) -> T;
306 /// Stores the value at the specified memory location, returning the old value.
307 /// The stabilized version of this intrinsic is available on the
308 /// `std::sync::atomic` types via the `swap` method by passing
309 /// [`Ordering::Release`](../../std/sync/atomic/enum.Ordering.html)
310 /// as the `order`. For example,
311 /// [`AtomicBool::swap`](../../std/sync/atomic/struct.AtomicBool.html#method.swap).
312 pub fn atomic_xchg_rel<T>(dst: *mut T, src: T) -> T;
313 /// Stores the value at the specified memory location, returning the old value.
314 /// The stabilized version of this intrinsic is available on the
315 /// `std::sync::atomic` types via the `swap` method by passing
316 /// [`Ordering::AcqRel`](../../std/sync/atomic/enum.Ordering.html)
317 /// as the `order`. For example,
318 /// [`AtomicBool::swap`](../../std/sync/atomic/struct.AtomicBool.html#method.swap).
319 pub fn atomic_xchg_acqrel<T>(dst: *mut T, src: T) -> T;
320 /// Stores the value at the specified memory location, returning the old value.
321 /// The stabilized version of this intrinsic is available on the
322 /// `std::sync::atomic` types via the `swap` method by passing
323 /// [`Ordering::Relaxed`](../../std/sync/atomic/enum.Ordering.html)
324 /// as the `order`. For example,
325 /// [`AtomicBool::swap`](../../std/sync/atomic/struct.AtomicBool.html#method.swap).
326 pub fn atomic_xchg_relaxed<T>(dst: *mut T, src: T) -> T;
328 /// Add to the current value, returning the previous value.
329 /// The stabilized version of this intrinsic is available on the
330 /// `std::sync::atomic` types via the `fetch_add` method by passing
331 /// [`Ordering::SeqCst`](../../std/sync/atomic/enum.Ordering.html)
332 /// as the `order`. For example,
333 /// [`AtomicIsize::fetch_add`](../../std/sync/atomic/struct.AtomicIsize.html#method.fetch_add).
334 pub fn atomic_xadd<T>(dst: *mut T, src: T) -> T;
335 /// Add to the current value, returning the previous value.
336 /// The stabilized version of this intrinsic is available on the
337 /// `std::sync::atomic` types via the `fetch_add` method by passing
338 /// [`Ordering::Acquire`](../../std/sync/atomic/enum.Ordering.html)
339 /// as the `order`. For example,
340 /// [`AtomicIsize::fetch_add`](../../std/sync/atomic/struct.AtomicIsize.html#method.fetch_add).
341 pub fn atomic_xadd_acq<T>(dst: *mut T, src: T) -> T;
342 /// Add to the current value, returning the previous value.
343 /// The stabilized version of this intrinsic is available on the
344 /// `std::sync::atomic` types via the `fetch_add` method by passing
345 /// [`Ordering::Release`](../../std/sync/atomic/enum.Ordering.html)
346 /// as the `order`. For example,
347 /// [`AtomicIsize::fetch_add`](../../std/sync/atomic/struct.AtomicIsize.html#method.fetch_add).
348 pub fn atomic_xadd_rel<T>(dst: *mut T, src: T) -> T;
349 /// Add to the current value, returning the previous value.
350 /// The stabilized version of this intrinsic is available on the
351 /// `std::sync::atomic` types via the `fetch_add` method by passing
352 /// [`Ordering::AcqRel`](../../std/sync/atomic/enum.Ordering.html)
353 /// as the `order`. For example,
354 /// [`AtomicIsize::fetch_add`](../../std/sync/atomic/struct.AtomicIsize.html#method.fetch_add).
355 pub fn atomic_xadd_acqrel<T>(dst: *mut T, src: T) -> T;
356 /// Add to the current value, returning the previous value.
357 /// The stabilized version of this intrinsic is available on the
358 /// `std::sync::atomic` types via the `fetch_add` method by passing
359 /// [`Ordering::Relaxed`](../../std/sync/atomic/enum.Ordering.html)
360 /// as the `order`. For example,
361 /// [`AtomicIsize::fetch_add`](../../std/sync/atomic/struct.AtomicIsize.html#method.fetch_add).
362 pub fn atomic_xadd_relaxed<T>(dst: *mut T, src: T) -> T;
364 /// Subtract from the current value, returning the previous value.
365 /// The stabilized version of this intrinsic is available on the
366 /// `std::sync::atomic` types via the `fetch_sub` method by passing
367 /// [`Ordering::SeqCst`](../../std/sync/atomic/enum.Ordering.html)
368 /// as the `order`. For example,
369 /// [`AtomicIsize::fetch_sub`](../../std/sync/atomic/struct.AtomicIsize.html#method.fetch_sub).
370 pub fn atomic_xsub<T>(dst: *mut T, src: T) -> T;
371 /// Subtract from the current value, returning the previous value.
372 /// The stabilized version of this intrinsic is available on the
373 /// `std::sync::atomic` types via the `fetch_sub` method by passing
374 /// [`Ordering::Acquire`](../../std/sync/atomic/enum.Ordering.html)
375 /// as the `order`. For example,
376 /// [`AtomicIsize::fetch_sub`](../../std/sync/atomic/struct.AtomicIsize.html#method.fetch_sub).
377 pub fn atomic_xsub_acq<T>(dst: *mut T, src: T) -> T;
378 /// Subtract from the current value, returning the previous value.
379 /// The stabilized version of this intrinsic is available on the
380 /// `std::sync::atomic` types via the `fetch_sub` method by passing
381 /// [`Ordering::Release`](../../std/sync/atomic/enum.Ordering.html)
382 /// as the `order`. For example,
383 /// [`AtomicIsize::fetch_sub`](../../std/sync/atomic/struct.AtomicIsize.html#method.fetch_sub).
384 pub fn atomic_xsub_rel<T>(dst: *mut T, src: T) -> T;
385 /// Subtract from the current value, returning the previous value.
386 /// The stabilized version of this intrinsic is available on the
387 /// `std::sync::atomic` types via the `fetch_sub` method by passing
388 /// [`Ordering::AcqRel`](../../std/sync/atomic/enum.Ordering.html)
389 /// as the `order`. For example,
390 /// [`AtomicIsize::fetch_sub`](../../std/sync/atomic/struct.AtomicIsize.html#method.fetch_sub).
391 pub fn atomic_xsub_acqrel<T>(dst: *mut T, src: T) -> T;
392 /// Subtract from the current value, returning the previous value.
393 /// The stabilized version of this intrinsic is available on the
394 /// `std::sync::atomic` types via the `fetch_sub` method by passing
395 /// [`Ordering::Relaxed`](../../std/sync/atomic/enum.Ordering.html)
396 /// as the `order`. For example,
397 /// [`AtomicIsize::fetch_sub`](../../std/sync/atomic/struct.AtomicIsize.html#method.fetch_sub).
398 pub fn atomic_xsub_relaxed<T>(dst: *mut T, src: T) -> T;
400 /// Bitwise and with the current value, returning the previous value.
401 /// The stabilized version of this intrinsic is available on the
402 /// `std::sync::atomic` types via the `fetch_and` method by passing
403 /// [`Ordering::SeqCst`](../../std/sync/atomic/enum.Ordering.html)
404 /// as the `order`. For example,
405 /// [`AtomicBool::fetch_and`](../../std/sync/atomic/struct.AtomicBool.html#method.fetch_and).
406 pub fn atomic_and<T>(dst: *mut T, src: T) -> T;
407 /// Bitwise and with the current value, returning the previous value.
408 /// The stabilized version of this intrinsic is available on the
409 /// `std::sync::atomic` types via the `fetch_and` method by passing
410 /// [`Ordering::Acquire`](../../std/sync/atomic/enum.Ordering.html)
411 /// as the `order`. For example,
412 /// [`AtomicBool::fetch_and`](../../std/sync/atomic/struct.AtomicBool.html#method.fetch_and).
413 pub fn atomic_and_acq<T>(dst: *mut T, src: T) -> T;
414 /// Bitwise and with the current value, returning the previous value.
415 /// The stabilized version of this intrinsic is available on the
416 /// `std::sync::atomic` types via the `fetch_and` method by passing
417 /// [`Ordering::Release`](../../std/sync/atomic/enum.Ordering.html)
418 /// as the `order`. For example,
419 /// [`AtomicBool::fetch_and`](../../std/sync/atomic/struct.AtomicBool.html#method.fetch_and).
420 pub fn atomic_and_rel<T>(dst: *mut T, src: T) -> T;
421 /// Bitwise and with the current value, returning the previous value.
422 /// The stabilized version of this intrinsic is available on the
423 /// `std::sync::atomic` types via the `fetch_and` method by passing
424 /// [`Ordering::AcqRel`](../../std/sync/atomic/enum.Ordering.html)
425 /// as the `order`. For example,
426 /// [`AtomicBool::fetch_and`](../../std/sync/atomic/struct.AtomicBool.html#method.fetch_and).
427 pub fn atomic_and_acqrel<T>(dst: *mut T, src: T) -> T;
428 /// Bitwise and with the current value, returning the previous value.
429 /// The stabilized version of this intrinsic is available on the
430 /// `std::sync::atomic` types via the `fetch_and` method by passing
431 /// [`Ordering::Relaxed`](../../std/sync/atomic/enum.Ordering.html)
432 /// as the `order`. For example,
433 /// [`AtomicBool::fetch_and`](../../std/sync/atomic/struct.AtomicBool.html#method.fetch_and).
434 pub fn atomic_and_relaxed<T>(dst: *mut T, src: T) -> T;
436 /// Bitwise nand with the current value, returning the previous value.
437 /// The stabilized version of this intrinsic is available on the
438 /// `std::sync::atomic::AtomicBool` type via the `fetch_nand` method by passing
439 /// [`Ordering::SeqCst`](../../std/sync/atomic/enum.Ordering.html)
440 /// as the `order`. For example,
441 /// [`AtomicBool::fetch_nand`](../../std/sync/atomic/struct.AtomicBool.html#method.fetch_nand).
442 pub fn atomic_nand<T>(dst: *mut T, src: T) -> T;
443 /// Bitwise nand with the current value, returning the previous value.
444 /// The stabilized version of this intrinsic is available on the
445 /// `std::sync::atomic::AtomicBool` type via the `fetch_nand` method by passing
446 /// [`Ordering::Acquire`](../../std/sync/atomic/enum.Ordering.html)
447 /// as the `order`. For example,
448 /// [`AtomicBool::fetch_nand`](../../std/sync/atomic/struct.AtomicBool.html#method.fetch_nand).
449 pub fn atomic_nand_acq<T>(dst: *mut T, src: T) -> T;
450 /// Bitwise nand with the current value, returning the previous value.
451 /// The stabilized version of this intrinsic is available on the
452 /// `std::sync::atomic::AtomicBool` type via the `fetch_nand` method by passing
453 /// [`Ordering::Release`](../../std/sync/atomic/enum.Ordering.html)
454 /// as the `order`. For example,
455 /// [`AtomicBool::fetch_nand`](../../std/sync/atomic/struct.AtomicBool.html#method.fetch_nand).
456 pub fn atomic_nand_rel<T>(dst: *mut T, src: T) -> T;
457 /// Bitwise nand with the current value, returning the previous value.
458 /// The stabilized version of this intrinsic is available on the
459 /// `std::sync::atomic::AtomicBool` type via the `fetch_nand` method by passing
460 /// [`Ordering::AcqRel`](../../std/sync/atomic/enum.Ordering.html)
461 /// as the `order`. For example,
462 /// [`AtomicBool::fetch_nand`](../../std/sync/atomic/struct.AtomicBool.html#method.fetch_nand).
463 pub fn atomic_nand_acqrel<T>(dst: *mut T, src: T) -> T;
464 /// Bitwise nand with the current value, returning the previous value.
465 /// The stabilized version of this intrinsic is available on the
466 /// `std::sync::atomic::AtomicBool` type via the `fetch_nand` method by passing
467 /// [`Ordering::Relaxed`](../../std/sync/atomic/enum.Ordering.html)
468 /// as the `order`. For example,
469 /// [`AtomicBool::fetch_nand`](../../std/sync/atomic/struct.AtomicBool.html#method.fetch_nand).
470 pub fn atomic_nand_relaxed<T>(dst: *mut T, src: T) -> T;
472 /// Bitwise or with the current value, returning the previous value.
473 /// The stabilized version of this intrinsic is available on the
474 /// `std::sync::atomic` types via the `fetch_or` method by passing
475 /// [`Ordering::SeqCst`](../../std/sync/atomic/enum.Ordering.html)
476 /// as the `order`. For example,
477 /// [`AtomicBool::fetch_or`](../../std/sync/atomic/struct.AtomicBool.html#method.fetch_or).
478 pub fn atomic_or<T>(dst: *mut T, src: T) -> T;
479 /// Bitwise or with the current value, returning the previous value.
480 /// The stabilized version of this intrinsic is available on the
481 /// `std::sync::atomic` types via the `fetch_or` method by passing
482 /// [`Ordering::Acquire`](../../std/sync/atomic/enum.Ordering.html)
483 /// as the `order`. For example,
484 /// [`AtomicBool::fetch_or`](../../std/sync/atomic/struct.AtomicBool.html#method.fetch_or).
485 pub fn atomic_or_acq<T>(dst: *mut T, src: T) -> T;
486 /// Bitwise or with the current value, returning the previous value.
487 /// The stabilized version of this intrinsic is available on the
488 /// `std::sync::atomic` types via the `fetch_or` method by passing
489 /// [`Ordering::Release`](../../std/sync/atomic/enum.Ordering.html)
490 /// as the `order`. For example,
491 /// [`AtomicBool::fetch_or`](../../std/sync/atomic/struct.AtomicBool.html#method.fetch_or).
492 pub fn atomic_or_rel<T>(dst: *mut T, src: T) -> T;
493 /// Bitwise or with the current value, returning the previous value.
494 /// The stabilized version of this intrinsic is available on the
495 /// `std::sync::atomic` types via the `fetch_or` method by passing
496 /// [`Ordering::AcqRel`](../../std/sync/atomic/enum.Ordering.html)
497 /// as the `order`. For example,
498 /// [`AtomicBool::fetch_or`](../../std/sync/atomic/struct.AtomicBool.html#method.fetch_or).
499 pub fn atomic_or_acqrel<T>(dst: *mut T, src: T) -> T;
500 /// Bitwise or with the current value, returning the previous value.
501 /// The stabilized version of this intrinsic is available on the
502 /// `std::sync::atomic` types via the `fetch_or` method by passing
503 /// [`Ordering::Relaxed`](../../std/sync/atomic/enum.Ordering.html)
504 /// as the `order`. For example,
505 /// [`AtomicBool::fetch_or`](../../std/sync/atomic/struct.AtomicBool.html#method.fetch_or).
506 pub fn atomic_or_relaxed<T>(dst: *mut T, src: T) -> T;
508 /// Bitwise xor with the current value, returning the previous value.
509 /// The stabilized version of this intrinsic is available on the
510 /// `std::sync::atomic` types via the `fetch_xor` method by passing
511 /// [`Ordering::SeqCst`](../../std/sync/atomic/enum.Ordering.html)
512 /// as the `order`. For example,
513 /// [`AtomicBool::fetch_xor`](../../std/sync/atomic/struct.AtomicBool.html#method.fetch_xor).
514 pub fn atomic_xor<T>(dst: *mut T, src: T) -> T;
515 /// Bitwise xor with the current value, returning the previous value.
516 /// The stabilized version of this intrinsic is available on the
517 /// `std::sync::atomic` types via the `fetch_xor` method by passing
518 /// [`Ordering::Acquire`](../../std/sync/atomic/enum.Ordering.html)
519 /// as the `order`. For example,
520 /// [`AtomicBool::fetch_xor`](../../std/sync/atomic/struct.AtomicBool.html#method.fetch_xor).
521 pub fn atomic_xor_acq<T>(dst: *mut T, src: T) -> T;
522 /// Bitwise xor with the current value, returning the previous value.
523 /// The stabilized version of this intrinsic is available on the
524 /// `std::sync::atomic` types via the `fetch_xor` method by passing
525 /// [`Ordering::Release`](../../std/sync/atomic/enum.Ordering.html)
526 /// as the `order`. For example,
527 /// [`AtomicBool::fetch_xor`](../../std/sync/atomic/struct.AtomicBool.html#method.fetch_xor).
528 pub fn atomic_xor_rel<T>(dst: *mut T, src: T) -> T;
529 /// Bitwise xor with the current value, returning the previous value.
530 /// The stabilized version of this intrinsic is available on the
531 /// `std::sync::atomic` types via the `fetch_xor` method by passing
532 /// [`Ordering::AcqRel`](../../std/sync/atomic/enum.Ordering.html)
533 /// as the `order`. For example,
534 /// [`AtomicBool::fetch_xor`](../../std/sync/atomic/struct.AtomicBool.html#method.fetch_xor).
535 pub fn atomic_xor_acqrel<T>(dst: *mut T, src: T) -> T;
536 /// Bitwise xor with the current value, returning the previous value.
537 /// The stabilized version of this intrinsic is available on the
538 /// `std::sync::atomic` types via the `fetch_xor` method by passing
539 /// [`Ordering::Relaxed`](../../std/sync/atomic/enum.Ordering.html)
540 /// as the `order`. For example,
541 /// [`AtomicBool::fetch_xor`](../../std/sync/atomic/struct.AtomicBool.html#method.fetch_xor).
542 pub fn atomic_xor_relaxed<T>(dst: *mut T, src: T) -> T;
544 pub fn atomic_max<T>(dst: *mut T, src: T) -> T;
545 pub fn atomic_max_acq<T>(dst: *mut T, src: T) -> T;
546 pub fn atomic_max_rel<T>(dst: *mut T, src: T) -> T;
547 pub fn atomic_max_acqrel<T>(dst: *mut T, src: T) -> T;
548 pub fn atomic_max_relaxed<T>(dst: *mut T, src: T) -> T;
550 pub fn atomic_min<T>(dst: *mut T, src: T) -> T;
551 pub fn atomic_min_acq<T>(dst: *mut T, src: T) -> T;
552 pub fn atomic_min_rel<T>(dst: *mut T, src: T) -> T;
553 pub fn atomic_min_acqrel<T>(dst: *mut T, src: T) -> T;
554 pub fn atomic_min_relaxed<T>(dst: *mut T, src: T) -> T;
556 pub fn atomic_umin<T>(dst: *mut T, src: T) -> T;
557 pub fn atomic_umin_acq<T>(dst: *mut T, src: T) -> T;
558 pub fn atomic_umin_rel<T>(dst: *mut T, src: T) -> T;
559 pub fn atomic_umin_acqrel<T>(dst: *mut T, src: T) -> T;
560 pub fn atomic_umin_relaxed<T>(dst: *mut T, src: T) -> T;
562 pub fn atomic_umax<T>(dst: *mut T, src: T) -> T;
563 pub fn atomic_umax_acq<T>(dst: *mut T, src: T) -> T;
564 pub fn atomic_umax_rel<T>(dst: *mut T, src: T) -> T;
565 pub fn atomic_umax_acqrel<T>(dst: *mut T, src: T) -> T;
566 pub fn atomic_umax_relaxed<T>(dst: *mut T, src: T) -> T;
568 /// The `prefetch` intrinsic is a hint to the code generator to insert a prefetch instruction
569 /// if supported; otherwise, it is a noop.
570 /// Prefetches have no effect on the behavior of the program but can change its performance
573 /// The `locality` argument must be a constant integer and is a temporal locality specifier
574 /// ranging from (0) - no locality, to (3) - extremely local keep in cache
575 pub fn prefetch_read_data<T>(data: *const T, locality: i32);
576 /// The `prefetch` intrinsic is a hint to the code generator to insert a prefetch instruction
577 /// if supported; otherwise, it is a noop.
578 /// Prefetches have no effect on the behavior of the program but can change its performance
581 /// The `locality` argument must be a constant integer and is a temporal locality specifier
582 /// ranging from (0) - no locality, to (3) - extremely local keep in cache
583 pub fn prefetch_write_data<T>(data: *const T, locality: i32);
584 /// The `prefetch` intrinsic is a hint to the code generator to insert a prefetch instruction
585 /// if supported; otherwise, it is a noop.
586 /// Prefetches have no effect on the behavior of the program but can change its performance
589 /// The `locality` argument must be a constant integer and is a temporal locality specifier
590 /// ranging from (0) - no locality, to (3) - extremely local keep in cache
591 pub fn prefetch_read_instruction<T>(data: *const T, locality: i32);
592 /// The `prefetch` intrinsic is a hint to the code generator to insert a prefetch instruction
593 /// if supported; otherwise, it is a noop.
594 /// Prefetches have no effect on the behavior of the program but can change its performance
597 /// The `locality` argument must be a constant integer and is a temporal locality specifier
598 /// ranging from (0) - no locality, to (3) - extremely local keep in cache
599 pub fn prefetch_write_instruction<T>(data: *const T, locality: i32);
602 extern "rust-intrinsic" {
604 pub fn atomic_fence();
605 pub fn atomic_fence_acq();
606 pub fn atomic_fence_rel();
607 pub fn atomic_fence_acqrel();
609 /// A compiler-only memory barrier.
611 /// Memory accesses will never be reordered across this barrier by the
612 /// compiler, but no instructions will be emitted for it. This is
613 /// appropriate for operations on the same thread that may be preempted,
614 /// such as when interacting with signal handlers.
615 pub fn atomic_singlethreadfence();
616 pub fn atomic_singlethreadfence_acq();
617 pub fn atomic_singlethreadfence_rel();
618 pub fn atomic_singlethreadfence_acqrel();
620 /// Magic intrinsic that derives its meaning from attributes
621 /// attached to the function.
623 /// For example, dataflow uses this to inject static assertions so
624 /// that `rustc_peek(potentially_uninitialized)` would actually
625 /// double-check that dataflow did indeed compute that it is
626 /// uninitialized at that point in the control flow.
627 pub fn rustc_peek<T>(_: T) -> T;
629 /// Aborts the execution of the process.
631 /// The stabilized version of this intrinsic is
632 /// [`std::process::abort`](../../std/process/fn.abort.html)
635 /// Tells LLVM that this point in the code is not reachable, enabling
636 /// further optimizations.
638 /// NB: This is very different from the `unreachable!()` macro: Unlike the
639 /// macro, which panics when it is executed, it is *undefined behavior* to
640 /// reach code marked with this function.
642 /// The stabilized version of this intrinsic is
643 /// [`std::hint::unreachable_unchecked`](../../std/hint/fn.unreachable_unchecked.html).
644 pub fn unreachable() -> !;
646 /// Informs the optimizer that a condition is always true.
647 /// If the condition is false, the behavior is undefined.
649 /// No code is generated for this intrinsic, but the optimizer will try
650 /// to preserve it (and its condition) between passes, which may interfere
651 /// with optimization of surrounding code and reduce performance. It should
652 /// not be used if the invariant can be discovered by the optimizer on its
653 /// own, or if it does not enable any significant optimizations.
654 pub fn assume(b: bool);
656 /// Hints to the compiler that branch condition is likely to be true.
657 /// Returns the value passed to it.
659 /// Any use other than with `if` statements will probably not have an effect.
660 pub fn likely(b: bool) -> bool;
662 /// Hints to the compiler that branch condition is likely to be false.
663 /// Returns the value passed to it.
665 /// Any use other than with `if` statements will probably not have an effect.
666 pub fn unlikely(b: bool) -> bool;
668 /// Executes a breakpoint trap, for inspection by a debugger.
671 /// The size of a type in bytes.
673 /// More specifically, this is the offset in bytes between successive
674 /// items of the same type, including alignment padding.
675 pub fn size_of<T>() -> usize;
677 /// Moves a value to an uninitialized memory location.
679 /// Drop glue is not run on the destination.
680 pub fn move_val_init<T>(dst: *mut T, src: T);
682 pub fn min_align_of<T>() -> usize;
683 pub fn pref_align_of<T>() -> usize;
685 /// The size of the referenced value in bytes.
687 /// The stabilized version of this intrinsic is
688 /// [`std::mem::size_of_val`](../../std/mem/fn.size_of_val.html).
689 pub fn size_of_val<T: ?Sized>(_: &T) -> usize;
690 pub fn min_align_of_val<T: ?Sized>(_: &T) -> usize;
692 /// Gets a static string slice containing the name of a type.
693 pub fn type_name<T: ?Sized>() -> &'static str;
695 /// Gets an identifier which is globally unique to the specified type. This
696 /// function will return the same value for a type regardless of whichever
697 /// crate it is invoked in.
698 pub fn type_id<T: ?Sized + 'static>() -> u64;
700 /// Creates a value initialized to zero.
702 /// `init` is unsafe because it returns a zeroed-out datum,
703 /// which is unsafe unless T is `Copy`. Also, even if T is
704 /// `Copy`, an all-zero value may not correspond to any legitimate
705 /// state for the type in question.
706 pub fn init<T>() -> T;
708 /// Creates an uninitialized value.
710 /// `uninit` is unsafe because there is no guarantee of what its
711 /// contents are. In particular its drop-flag may be set to any
712 /// state, which means it may claim either dropped or
713 /// undropped. In the general case one must use `ptr::write` to
714 /// initialize memory previous set to the result of `uninit`.
715 pub fn uninit<T>() -> T;
717 /// Reinterprets the bits of a value of one type as another type.
719 /// Both types must have the same size. Neither the original, nor the result,
720 /// may be an [invalid value](../../nomicon/what-unsafe-does.html).
722 /// `transmute` is semantically equivalent to a bitwise move of one type
723 /// into another. It copies the bits from the source value into the
724 /// destination value, then forgets the original. It's equivalent to C's
725 /// `memcpy` under the hood, just like `transmute_copy`.
727 /// `transmute` is **incredibly** unsafe. There are a vast number of ways to
728 /// cause [undefined behavior][ub] with this function. `transmute` should be
729 /// the absolute last resort.
731 /// The [nomicon](../../nomicon/transmutes.html) has additional
734 /// [ub]: ../../reference/behavior-considered-undefined.html
738 /// There are a few things that `transmute` is really useful for.
740 /// Getting the bitpattern of a floating point type (or, more generally,
741 /// type punning, when `T` and `U` aren't pointers):
744 /// let bitpattern = unsafe {
745 /// std::mem::transmute::<f32, u32>(1.0)
747 /// assert_eq!(bitpattern, 0x3F800000);
750 /// Turning a pointer into a function pointer. This is *not* portable to
751 /// machines where function pointers and data pointers have different sizes.
754 /// fn foo() -> i32 {
757 /// let pointer = foo as *const ();
758 /// let function = unsafe {
759 /// std::mem::transmute::<*const (), fn() -> i32>(pointer)
761 /// assert_eq!(function(), 0);
764 /// Extending a lifetime, or shortening an invariant lifetime. This is
765 /// advanced, very unsafe Rust!
768 /// struct R<'a>(&'a i32);
769 /// unsafe fn extend_lifetime<'b>(r: R<'b>) -> R<'static> {
770 /// std::mem::transmute::<R<'b>, R<'static>>(r)
773 /// unsafe fn shorten_invariant_lifetime<'b, 'c>(r: &'b mut R<'static>)
774 /// -> &'b mut R<'c> {
775 /// std::mem::transmute::<&'b mut R<'static>, &'b mut R<'c>>(r)
781 /// Don't despair: many uses of `transmute` can be achieved through other means.
782 /// Below are common applications of `transmute` which can be replaced with safer
785 /// Turning a pointer into a `usize`:
789 /// let ptr_num_transmute = unsafe {
790 /// std::mem::transmute::<&i32, usize>(ptr)
793 /// // Use an `as` cast instead
794 /// let ptr_num_cast = ptr as *const i32 as usize;
797 /// Turning a `*mut T` into an `&mut T`:
800 /// let ptr: *mut i32 = &mut 0;
801 /// let ref_transmuted = unsafe {
802 /// std::mem::transmute::<*mut i32, &mut i32>(ptr)
805 /// // Use a reborrow instead
806 /// let ref_casted = unsafe { &mut *ptr };
809 /// Turning an `&mut T` into an `&mut U`:
812 /// let ptr = &mut 0;
813 /// let val_transmuted = unsafe {
814 /// std::mem::transmute::<&mut i32, &mut u32>(ptr)
817 /// // Now, put together `as` and reborrowing - note the chaining of `as`
818 /// // `as` is not transitive
819 /// let val_casts = unsafe { &mut *(ptr as *mut i32 as *mut u32) };
822 /// Turning an `&str` into an `&[u8]`:
825 /// // this is not a good way to do this.
826 /// let slice = unsafe { std::mem::transmute::<&str, &[u8]>("Rust") };
827 /// assert_eq!(slice, &[82, 117, 115, 116]);
829 /// // You could use `str::as_bytes`
830 /// let slice = "Rust".as_bytes();
831 /// assert_eq!(slice, &[82, 117, 115, 116]);
833 /// // Or, just use a byte string, if you have control over the string
835 /// assert_eq!(b"Rust", &[82, 117, 115, 116]);
838 /// Turning a `Vec<&T>` into a `Vec<Option<&T>>`:
841 /// let store = [0, 1, 2, 3];
842 /// let mut v_orig = store.iter().collect::<Vec<&i32>>();
844 /// // Using transmute: this is Undefined Behavior, and a bad idea.
845 /// // However, it is no-copy.
846 /// let v_transmuted = unsafe {
847 /// std::mem::transmute::<Vec<&i32>, Vec<Option<&i32>>>(
851 /// // This is the suggested, safe way.
852 /// // It does copy the entire vector, though, into a new array.
853 /// let v_collected = v_orig.clone()
855 /// .map(|r| Some(r))
856 /// .collect::<Vec<Option<&i32>>>();
858 /// // The no-copy, unsafe way, still using transmute, but not UB.
859 /// // This is equivalent to the original, but safer, and reuses the
860 /// // same Vec internals. Therefore the new inner type must have the
861 /// // exact same size, and the same alignment, as the old type.
862 /// // The same caveats exist for this method as transmute, for
863 /// // the original inner type (`&i32`) to the converted inner type
864 /// // (`Option<&i32>`), so read the nomicon pages linked above.
865 /// let v_from_raw = unsafe {
866 /// Vec::from_raw_parts(v_orig.as_mut_ptr() as *mut Option<&i32>,
868 /// v_orig.capacity())
870 /// std::mem::forget(v_orig);
873 /// Implementing `split_at_mut`:
876 /// use std::{slice, mem};
878 /// // There are multiple ways to do this; and there are multiple problems
879 /// // with the following, transmute, way.
880 /// fn split_at_mut_transmute<T>(slice: &mut [T], mid: usize)
881 /// -> (&mut [T], &mut [T]) {
882 /// let len = slice.len();
883 /// assert!(mid <= len);
885 /// let slice2 = mem::transmute::<&mut [T], &mut [T]>(slice);
886 /// // first: transmute is not typesafe; all it checks is that T and
887 /// // U are of the same size. Second, right here, you have two
888 /// // mutable references pointing to the same memory.
889 /// (&mut slice[0..mid], &mut slice2[mid..len])
893 /// // This gets rid of the typesafety problems; `&mut *` will *only* give
894 /// // you an `&mut T` from an `&mut T` or `*mut T`.
895 /// fn split_at_mut_casts<T>(slice: &mut [T], mid: usize)
896 /// -> (&mut [T], &mut [T]) {
897 /// let len = slice.len();
898 /// assert!(mid <= len);
900 /// let slice2 = &mut *(slice as *mut [T]);
901 /// // however, you still have two mutable references pointing to
902 /// // the same memory.
903 /// (&mut slice[0..mid], &mut slice2[mid..len])
907 /// // This is how the standard library does it. This is the best method, if
908 /// // you need to do something like this
909 /// fn split_at_stdlib<T>(slice: &mut [T], mid: usize)
910 /// -> (&mut [T], &mut [T]) {
911 /// let len = slice.len();
912 /// assert!(mid <= len);
914 /// let ptr = slice.as_mut_ptr();
915 /// // This now has three mutable references pointing at the same
916 /// // memory. `slice`, the rvalue ret.0, and the rvalue ret.1.
917 /// // `slice` is never used after `let ptr = ...`, and so one can
918 /// // treat it as "dead", and therefore, you only have two real
919 /// // mutable slices.
920 /// (slice::from_raw_parts_mut(ptr, mid),
921 /// slice::from_raw_parts_mut(ptr.add(mid), len - mid))
925 #[stable(feature = "rust1", since = "1.0.0")]
926 pub fn transmute<T, U>(e: T) -> U;
928 /// Returns `true` if the actual type given as `T` requires drop
929 /// glue; returns `false` if the actual type provided for `T`
930 /// implements `Copy`.
932 /// If the actual type neither requires drop glue nor implements
933 /// `Copy`, then may return `true` or `false`.
935 /// The stabilized version of this intrinsic is
936 /// [`std::mem::needs_drop`](../../std/mem/fn.needs_drop.html).
937 pub fn needs_drop<T>() -> bool;
939 /// Calculates the offset from a pointer.
941 /// This is implemented as an intrinsic to avoid converting to and from an
942 /// integer, since the conversion would throw away aliasing information.
946 /// Both the starting and resulting pointer must be either in bounds or one
947 /// byte past the end of an allocated object. If either pointer is out of
948 /// bounds or arithmetic overflow occurs then any further use of the
949 /// returned value will result in undefined behavior.
950 pub fn offset<T>(dst: *const T, offset: isize) -> *const T;
952 /// Calculates the offset from a pointer, potentially wrapping.
954 /// This is implemented as an intrinsic to avoid converting to and from an
955 /// integer, since the conversion inhibits certain optimizations.
959 /// Unlike the `offset` intrinsic, this intrinsic does not restrict the
960 /// resulting pointer to point into or one byte past the end of an allocated
961 /// object, and it wraps with two's complement arithmetic. The resulting
962 /// value is not necessarily valid to be used to actually access memory.
963 pub fn arith_offset<T>(dst: *const T, offset: isize) -> *const T;
965 /// Copies `count * size_of::<T>()` bytes from `src` to `dst`. The source
966 /// and destination must *not* overlap.
968 /// For regions of memory which might overlap, use [`copy`] instead.
970 /// `copy_nonoverlapping` is semantically equivalent to C's [`memcpy`].
972 /// [`copy`]: ./fn.copy.html
973 /// [`memcpy`]: https://www.gnu.org/software/libc/manual/html_node/Copying-Strings-and-Arrays.html#index-memcpy
977 /// Behavior is undefined if any of the following conditions are violated:
979 /// * Both `src` and `dst` must be [valid].
981 /// * Both `src` and `dst` must be properly aligned.
983 /// * `src.offset(count-1)` must be [valid]. In other words, the region of
984 /// memory which begins at `src` and has a length of `count *
985 /// size_of::<T>()` bytes must belong to a single, live allocation.
987 /// * `dst.offset(count-1)` must be [valid]. In other words, the region of
988 /// memory which begins at `dst` and has a length of `count *
989 /// size_of::<T>()` bytes must belong to a single, live allocation.
991 /// * The two regions of memory must *not* overlap.
993 /// Like [`read`], `copy` creates a bitwise copy of `T`, regardless of
994 /// whether `T` is [`Copy`]. If `T` is not [`Copy`], using both the values
995 /// in the region beginning at `*src` and the region beginning at `*dst` can
996 /// [violate memory safety][read-ownership].
998 /// [`Copy`]: ../marker/trait.Copy.html
999 /// [`read`]: ../ptr/fn.read.html
1000 /// [read-ownership]: ../ptr/fn.read.html#ownership-of-the-returned-value
1001 /// [valid]: ../ptr/index.html#safety
1005 /// Manually implement [`Vec::append`]:
1010 /// /// Moves all the elements of `src` into `dst`, leaving `src` empty.
1011 /// fn append<T>(dst: &mut Vec<T>, src: &mut Vec<T>) {
1012 /// let src_len = src.len();
1013 /// let dst_len = dst.len();
1015 /// // Ensure that `dst` has enough capacity to hold all of `src`.
1016 /// dst.reserve(src_len);
1019 /// // The call to offset is always safe because `Vec` will never
1020 /// // allocate more than `isize::MAX` bytes.
1021 /// let dst = dst.as_mut_ptr().offset(dst_len as isize);
1022 /// let src = src.as_ptr();
1024 /// // The two regions cannot overlap becuase mutable references do
1025 /// // not alias, and two different vectors cannot own the same
1027 /// ptr::copy_nonoverlapping(src, dst, src_len);
1031 /// // Truncate `src` without dropping its contents.
1034 /// // Notify `dst` that it now holds the contents of `src`.
1035 /// dst.set_len(dst_len + src_len);
1039 /// let mut a = vec!['r'];
1040 /// let mut b = vec!['u', 's', 't'];
1042 /// append(&mut a, &mut b);
1044 /// assert_eq!(a, &['r', 'u', 's', 't']);
1045 /// assert!(b.is_empty());
1048 /// [`Vec::append`]: ../../std/vec/struct.Vec.html#method.append
1049 #[stable(feature = "rust1", since = "1.0.0")]
1050 pub fn copy_nonoverlapping<T>(src: *const T, dst: *mut T, count: usize);
1052 /// Copies `count * size_of::<T>()` bytes from `src` to `dst`. The source
1053 /// and destination may overlap.
1055 /// If the source and destination will *never* overlap,
1056 /// [`copy_nonoverlapping`] can be used instead.
1058 /// `copy` is semantically equivalent to C's [`memmove`].
1060 /// [`copy_nonoverlapping`]: ./fn.copy_nonoverlapping.html
1061 /// [`memmove`]: https://www.gnu.org/software/libc/manual/html_node/Copying-Strings-and-Arrays.html#index-memmove
1065 /// Behavior is undefined if any of the following conditions are violated:
1067 /// * Both `src` and `dst` must be [valid].
1069 /// * Both `src` and `dst` must be properly aligned.
1071 /// * `src.offset(count-1)` must be [valid]. In other words, the region of
1072 /// memory which begins at `src` and has a length of `count *
1073 /// size_of::<T>()` bytes must belong to a single, live allocation.
1075 /// * `dst.offset(count-1)` must be [valid]. In other words, the region of
1076 /// memory which begins at `dst` and has a length of `count *
1077 /// size_of::<T>()` bytes must belong to a single, live allocation.
1079 /// Like [`read`], `copy` creates a bitwise copy of `T`, regardless of
1080 /// whether `T` is [`Copy`]. If `T` is not [`Copy`], using both the values
1081 /// in the region beginning at `*src` and the region beginning at `*dst` can
1082 /// [violate memory safety][read-ownership].
1084 /// [`Copy`]: ../marker/trait.Copy.html
1085 /// [`read`]: ../ptr/fn.read.html
1086 /// [read-ownership]: ../ptr/fn.read.html#ownership-of-the-returned-value
1087 /// [valid]: ../ptr/index.html#safety
1091 /// Efficiently create a Rust vector from an unsafe buffer:
1096 /// # #[allow(dead_code)]
1097 /// unsafe fn from_buf_raw<T>(ptr: *const T, elts: usize) -> Vec<T> {
1098 /// let mut dst = Vec::with_capacity(elts);
1099 /// dst.set_len(elts);
1100 /// ptr::copy(ptr, dst.as_mut_ptr(), elts);
1104 #[stable(feature = "rust1", since = "1.0.0")]
1105 pub fn copy<T>(src: *const T, dst: *mut T, count: usize);
1107 /// Sets `count * size_of::<T>()` bytes of memory starting at `dst` to
1110 /// `write_bytes` is similar to C's [`memset`], but sets `count *
1111 /// size_of::<T>()` bytes to `val`.
1113 /// [`memset`]: https://www.gnu.org/software/libc/manual/html_node/Copying-Strings-and-Arrays.html#index-memset
1117 /// Behavior is undefined if any of the following conditions are violated:
1119 /// * `dst` must be [valid].
1121 /// * `dst.offset(count-1)` must be [valid]. In other words, the region of
1122 /// memory which begins at `dst` and has a length of `count *
1123 /// size_of::<T>()` bytes must belong to a single, live allocation.
1125 /// * `dst` must be properly aligned.
1127 /// Additionally, the caller must ensure that writing `count *
1128 /// size_of::<T>()` bytes to the given region of memory results in a valid
1129 /// value of `T`. Creating an invalid value of `T` can result in undefined
1132 /// [valid]: ../ptr/index.html#safety
1141 /// let mut vec = vec![0u32; 4];
1143 /// let vec_ptr = vec.as_mut_ptr();
1144 /// ptr::write_bytes(vec_ptr, 0xfe, 2);
1146 /// assert_eq!(vec, [0xfefefefe, 0xfefefefe, 0, 0]);
1149 /// Creating an invalid value:
1154 /// let mut v = Box::new(0i32);
1157 /// // Leaks the previously held value by overwriting the `Box<T>` with
1158 /// // a null pointer.
1159 /// ptr::write_bytes(&mut v, 0, 1);
1162 /// // At this point, using or dropping `v` results in undefined behavior.
1163 /// // v = Box::new(0i32); // ERROR
1165 #[stable(feature = "rust1", since = "1.0.0")]
1166 pub fn write_bytes<T>(dst: *mut T, val: u8, count: usize);
1168 /// Equivalent to the appropriate `llvm.memcpy.p0i8.0i8.*` intrinsic, with
1169 /// a size of `count` * `size_of::<T>()` and an alignment of
1170 /// `min_align_of::<T>()`
1172 /// The volatile parameter is set to `true`, so it will not be optimized out
1173 /// unless size is equal to zero.
1174 pub fn volatile_copy_nonoverlapping_memory<T>(dst: *mut T, src: *const T,
1176 /// Equivalent to the appropriate `llvm.memmove.p0i8.0i8.*` intrinsic, with
1177 /// a size of `count` * `size_of::<T>()` and an alignment of
1178 /// `min_align_of::<T>()`
1180 /// The volatile parameter is set to `true`, so it will not be optimized out
1181 /// unless size is equal to zero..
1182 pub fn volatile_copy_memory<T>(dst: *mut T, src: *const T, count: usize);
1183 /// Equivalent to the appropriate `llvm.memset.p0i8.*` intrinsic, with a
1184 /// size of `count` * `size_of::<T>()` and an alignment of
1185 /// `min_align_of::<T>()`.
1187 /// The volatile parameter is set to `true`, so it will not be optimized out
1188 /// unless size is equal to zero.
1189 pub fn volatile_set_memory<T>(dst: *mut T, val: u8, count: usize);
1191 /// Perform a volatile load from the `src` pointer.
1192 /// The stabilized version of this intrinsic is
1193 /// [`std::ptr::read_volatile`](../../std/ptr/fn.read_volatile.html).
1194 pub fn volatile_load<T>(src: *const T) -> T;
1195 /// Perform a volatile store to the `dst` pointer.
1196 /// The stabilized version of this intrinsic is
1197 /// [`std::ptr::write_volatile`](../../std/ptr/fn.write_volatile.html).
1198 pub fn volatile_store<T>(dst: *mut T, val: T);
1200 /// Perform a volatile load from the `src` pointer
1201 /// The pointer is not required to be aligned.
1202 pub fn unaligned_volatile_load<T>(src: *const T) -> T;
1203 /// Perform a volatile store to the `dst` pointer.
1204 /// The pointer is not required to be aligned.
1205 pub fn unaligned_volatile_store<T>(dst: *mut T, val: T);
1207 /// Returns the square root of an `f32`
1208 pub fn sqrtf32(x: f32) -> f32;
1209 /// Returns the square root of an `f64`
1210 pub fn sqrtf64(x: f64) -> f64;
1212 /// Raises an `f32` to an integer power.
1213 pub fn powif32(a: f32, x: i32) -> f32;
1214 /// Raises an `f64` to an integer power.
1215 pub fn powif64(a: f64, x: i32) -> f64;
1217 /// Returns the sine of an `f32`.
1218 pub fn sinf32(x: f32) -> f32;
1219 /// Returns the sine of an `f64`.
1220 pub fn sinf64(x: f64) -> f64;
1222 /// Returns the cosine of an `f32`.
1223 pub fn cosf32(x: f32) -> f32;
1224 /// Returns the cosine of an `f64`.
1225 pub fn cosf64(x: f64) -> f64;
1227 /// Raises an `f32` to an `f32` power.
1228 pub fn powf32(a: f32, x: f32) -> f32;
1229 /// Raises an `f64` to an `f64` power.
1230 pub fn powf64(a: f64, x: f64) -> f64;
1232 /// Returns the exponential of an `f32`.
1233 pub fn expf32(x: f32) -> f32;
1234 /// Returns the exponential of an `f64`.
1235 pub fn expf64(x: f64) -> f64;
1237 /// Returns 2 raised to the power of an `f32`.
1238 pub fn exp2f32(x: f32) -> f32;
1239 /// Returns 2 raised to the power of an `f64`.
1240 pub fn exp2f64(x: f64) -> f64;
1242 /// Returns the natural logarithm of an `f32`.
1243 pub fn logf32(x: f32) -> f32;
1244 /// Returns the natural logarithm of an `f64`.
1245 pub fn logf64(x: f64) -> f64;
1247 /// Returns the base 10 logarithm of an `f32`.
1248 pub fn log10f32(x: f32) -> f32;
1249 /// Returns the base 10 logarithm of an `f64`.
1250 pub fn log10f64(x: f64) -> f64;
1252 /// Returns the base 2 logarithm of an `f32`.
1253 pub fn log2f32(x: f32) -> f32;
1254 /// Returns the base 2 logarithm of an `f64`.
1255 pub fn log2f64(x: f64) -> f64;
1257 /// Returns `a * b + c` for `f32` values.
1258 pub fn fmaf32(a: f32, b: f32, c: f32) -> f32;
1259 /// Returns `a * b + c` for `f64` values.
1260 pub fn fmaf64(a: f64, b: f64, c: f64) -> f64;
1262 /// Returns the absolute value of an `f32`.
1263 pub fn fabsf32(x: f32) -> f32;
1264 /// Returns the absolute value of an `f64`.
1265 pub fn fabsf64(x: f64) -> f64;
1267 /// Copies the sign from `y` to `x` for `f32` values.
1268 pub fn copysignf32(x: f32, y: f32) -> f32;
1269 /// Copies the sign from `y` to `x` for `f64` values.
1270 pub fn copysignf64(x: f64, y: f64) -> f64;
1272 /// Returns the largest integer less than or equal to an `f32`.
1273 pub fn floorf32(x: f32) -> f32;
1274 /// Returns the largest integer less than or equal to an `f64`.
1275 pub fn floorf64(x: f64) -> f64;
1277 /// Returns the smallest integer greater than or equal to an `f32`.
1278 pub fn ceilf32(x: f32) -> f32;
1279 /// Returns the smallest integer greater than or equal to an `f64`.
1280 pub fn ceilf64(x: f64) -> f64;
1282 /// Returns the integer part of an `f32`.
1283 pub fn truncf32(x: f32) -> f32;
1284 /// Returns the integer part of an `f64`.
1285 pub fn truncf64(x: f64) -> f64;
1287 /// Returns the nearest integer to an `f32`. May raise an inexact floating-point exception
1288 /// if the argument is not an integer.
1289 pub fn rintf32(x: f32) -> f32;
1290 /// Returns the nearest integer to an `f64`. May raise an inexact floating-point exception
1291 /// if the argument is not an integer.
1292 pub fn rintf64(x: f64) -> f64;
1294 /// Returns the nearest integer to an `f32`.
1295 pub fn nearbyintf32(x: f32) -> f32;
1296 /// Returns the nearest integer to an `f64`.
1297 pub fn nearbyintf64(x: f64) -> f64;
1299 /// Returns the nearest integer to an `f32`. Rounds half-way cases away from zero.
1300 pub fn roundf32(x: f32) -> f32;
1301 /// Returns the nearest integer to an `f64`. Rounds half-way cases away from zero.
1302 pub fn roundf64(x: f64) -> f64;
1304 /// Float addition that allows optimizations based on algebraic rules.
1305 /// May assume inputs are finite.
1306 pub fn fadd_fast<T>(a: T, b: T) -> T;
1308 /// Float subtraction that allows optimizations based on algebraic rules.
1309 /// May assume inputs are finite.
1310 pub fn fsub_fast<T>(a: T, b: T) -> T;
1312 /// Float multiplication that allows optimizations based on algebraic rules.
1313 /// May assume inputs are finite.
1314 pub fn fmul_fast<T>(a: T, b: T) -> T;
1316 /// Float division that allows optimizations based on algebraic rules.
1317 /// May assume inputs are finite.
1318 pub fn fdiv_fast<T>(a: T, b: T) -> T;
1320 /// Float remainder that allows optimizations based on algebraic rules.
1321 /// May assume inputs are finite.
1322 pub fn frem_fast<T>(a: T, b: T) -> T;
1325 /// Returns the number of bits set in an integer type `T`
1326 pub fn ctpop<T>(x: T) -> T;
1328 /// Returns the number of leading unset bits (zeroes) in an integer type `T`.
1333 /// #![feature(core_intrinsics)]
1335 /// use std::intrinsics::ctlz;
1337 /// let x = 0b0001_1100_u8;
1338 /// let num_leading = unsafe { ctlz(x) };
1339 /// assert_eq!(num_leading, 3);
1342 /// An `x` with value `0` will return the bit width of `T`.
1345 /// #![feature(core_intrinsics)]
1347 /// use std::intrinsics::ctlz;
1350 /// let num_leading = unsafe { ctlz(x) };
1351 /// assert_eq!(num_leading, 16);
1353 pub fn ctlz<T>(x: T) -> T;
1355 /// Like `ctlz`, but extra-unsafe as it returns `undef` when
1356 /// given an `x` with value `0`.
1361 /// #![feature(core_intrinsics)]
1363 /// use std::intrinsics::ctlz_nonzero;
1365 /// let x = 0b0001_1100_u8;
1366 /// let num_leading = unsafe { ctlz_nonzero(x) };
1367 /// assert_eq!(num_leading, 3);
1369 pub fn ctlz_nonzero<T>(x: T) -> T;
1371 /// Returns the number of trailing unset bits (zeroes) in an integer type `T`.
1376 /// #![feature(core_intrinsics)]
1378 /// use std::intrinsics::cttz;
1380 /// let x = 0b0011_1000_u8;
1381 /// let num_trailing = unsafe { cttz(x) };
1382 /// assert_eq!(num_trailing, 3);
1385 /// An `x` with value `0` will return the bit width of `T`:
1388 /// #![feature(core_intrinsics)]
1390 /// use std::intrinsics::cttz;
1393 /// let num_trailing = unsafe { cttz(x) };
1394 /// assert_eq!(num_trailing, 16);
1396 pub fn cttz<T>(x: T) -> T;
1398 /// Like `cttz`, but extra-unsafe as it returns `undef` when
1399 /// given an `x` with value `0`.
1404 /// #![feature(core_intrinsics)]
1406 /// use std::intrinsics::cttz_nonzero;
1408 /// let x = 0b0011_1000_u8;
1409 /// let num_trailing = unsafe { cttz_nonzero(x) };
1410 /// assert_eq!(num_trailing, 3);
1412 pub fn cttz_nonzero<T>(x: T) -> T;
1414 /// Reverses the bytes in an integer type `T`.
1415 pub fn bswap<T>(x: T) -> T;
1417 /// Reverses the bits in an integer type `T`.
1418 pub fn bitreverse<T>(x: T) -> T;
1420 /// Performs checked integer addition.
1421 /// The stabilized versions of this intrinsic are available on the integer
1422 /// primitives via the `overflowing_add` method. For example,
1423 /// [`std::u32::overflowing_add`](../../std/primitive.u32.html#method.overflowing_add)
1424 pub fn add_with_overflow<T>(x: T, y: T) -> (T, bool);
1426 /// Performs checked integer subtraction
1427 /// The stabilized versions of this intrinsic are available on the integer
1428 /// primitives via the `overflowing_sub` method. For example,
1429 /// [`std::u32::overflowing_sub`](../../std/primitive.u32.html#method.overflowing_sub)
1430 pub fn sub_with_overflow<T>(x: T, y: T) -> (T, bool);
1432 /// Performs checked integer multiplication
1433 /// The stabilized versions of this intrinsic are available on the integer
1434 /// primitives via the `overflowing_mul` method. For example,
1435 /// [`std::u32::overflowing_mul`](../../std/primitive.u32.html#method.overflowing_mul)
1436 pub fn mul_with_overflow<T>(x: T, y: T) -> (T, bool);
1438 /// Performs an exact division, resulting in undefined behavior where
1439 /// `x % y != 0` or `y == 0` or `x == T::min_value() && y == -1`
1440 pub fn exact_div<T>(x: T, y: T) -> T;
1442 /// Performs an unchecked division, resulting in undefined behavior
1443 /// where y = 0 or x = `T::min_value()` and y = -1
1444 pub fn unchecked_div<T>(x: T, y: T) -> T;
1445 /// Returns the remainder of an unchecked division, resulting in
1446 /// undefined behavior where y = 0 or x = `T::min_value()` and y = -1
1447 pub fn unchecked_rem<T>(x: T, y: T) -> T;
1449 /// Performs an unchecked left shift, resulting in undefined behavior when
1450 /// y < 0 or y >= N, where N is the width of T in bits.
1451 pub fn unchecked_shl<T>(x: T, y: T) -> T;
1452 /// Performs an unchecked right shift, resulting in undefined behavior when
1453 /// y < 0 or y >= N, where N is the width of T in bits.
1454 pub fn unchecked_shr<T>(x: T, y: T) -> T;
1456 /// Returns (a + b) mod 2<sup>N</sup>, where N is the width of T in bits.
1457 /// The stabilized versions of this intrinsic are available on the integer
1458 /// primitives via the `wrapping_add` method. For example,
1459 /// [`std::u32::wrapping_add`](../../std/primitive.u32.html#method.wrapping_add)
1460 pub fn overflowing_add<T>(a: T, b: T) -> T;
1461 /// Returns (a - b) mod 2<sup>N</sup>, where N is the width of T in bits.
1462 /// The stabilized versions of this intrinsic are available on the integer
1463 /// primitives via the `wrapping_sub` method. For example,
1464 /// [`std::u32::wrapping_sub`](../../std/primitive.u32.html#method.wrapping_sub)
1465 pub fn overflowing_sub<T>(a: T, b: T) -> T;
1466 /// Returns (a * b) mod 2<sup>N</sup>, where N is the width of T in bits.
1467 /// The stabilized versions of this intrinsic are available on the integer
1468 /// primitives via the `wrapping_mul` method. For example,
1469 /// [`std::u32::wrapping_mul`](../../std/primitive.u32.html#method.wrapping_mul)
1470 pub fn overflowing_mul<T>(a: T, b: T) -> T;
1472 /// Returns the value of the discriminant for the variant in 'v',
1473 /// cast to a `u64`; if `T` has no discriminant, returns 0.
1474 pub fn discriminant_value<T>(v: &T) -> u64;
1476 /// Rust's "try catch" construct which invokes the function pointer `f` with
1477 /// the data pointer `data`.
1479 /// The third pointer is a target-specific data pointer which is filled in
1480 /// with the specifics of the exception that occurred. For examples on Unix
1481 /// platforms this is a `*mut *mut T` which is filled in by the compiler and
1482 /// on MSVC it's `*mut [usize; 2]`. For more information see the compiler's
1483 /// source as well as std's catch implementation.
1484 pub fn try(f: fn(*mut u8), data: *mut u8, local_ptr: *mut u8) -> i32;
1486 /// Emits a `!nontemporal` store according to LLVM (see their docs).
1487 /// Probably will never become stable.
1488 pub fn nontemporal_store<T>(ptr: *mut T, val: T);