src/libcore/intrinsics.rs

   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.
   4 //
   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.
  10
  11 //! rustc compiler intrinsics.
  12 //!
  13 //! The corresponding definitions are in librustc_trans/trans/intrinsic.rs.
  14 //!
  15 //! # Volatiles
  16 //!
  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
  20 //! [[volatile]].
  21 //!
  22 //! [volatile]: http://llvm.org/docs/LangRef.html#volatile-memory-accesses
  23 //!
  24 //! # Atomics
  25 //!
  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]].
  29 //!
  30 //! [atomics]: http://llvm.org/docs/Atomics.html
  31 //!
  32 //! A quick refresher on memory ordering:
  33 //!
  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`.
  41
  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",
  46             issue = "0")]
  47 #![allow(missing_docs)]
  48
  49 use marker::Sized;
  50
  51 extern "rust-intrinsic" {
  52
  53     // NB: These intrinsics take raw pointers because they mutate aliased
  54     // memory, which is not valid for either `&` or `&mut`.
  55
  56     #[cfg(all(stage0, not(cargobuild)))]
  57     pub fn atomic_cxchg<T>(dst: *mut T, old: T, src: T) -> T;
  58     #[cfg(all(stage0, not(cargobuild)))]
  59     pub fn atomic_cxchg_acq<T>(dst: *mut T, old: T, src: T) -> T;
  60     #[cfg(all(stage0, not(cargobuild)))]
  61     pub fn atomic_cxchg_rel<T>(dst: *mut T, old: T, src: T) -> T;
  62     #[cfg(all(stage0, not(cargobuild)))]
  63     pub fn atomic_cxchg_acqrel<T>(dst: *mut T, old: T, src: T) -> T;
  64     #[cfg(all(stage0, not(cargobuild)))]
  65     pub fn atomic_cxchg_relaxed<T>(dst: *mut T, old: T, src: T) -> T;
  66
  67     #[cfg(any(not(stage0), cargobuild))]
  68     pub fn atomic_cxchg<T>(dst: *mut T, old: T, src: T) -> (T, bool);
  69     #[cfg(any(not(stage0), cargobuild))]
  70     pub fn atomic_cxchg_acq<T>(dst: *mut T, old: T, src: T) -> (T, bool);
  71     #[cfg(any(not(stage0), cargobuild))]
  72     pub fn atomic_cxchg_rel<T>(dst: *mut T, old: T, src: T) -> (T, bool);
  73     #[cfg(any(not(stage0), cargobuild))]
  74     pub fn atomic_cxchg_acqrel<T>(dst: *mut T, old: T, src: T) -> (T, bool);
  75     #[cfg(any(not(stage0), cargobuild))]
  76     pub fn atomic_cxchg_relaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool);
  77     #[cfg(any(not(stage0), cargobuild))]
  78     pub fn atomic_cxchg_failrelaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool);
  79     #[cfg(any(not(stage0), cargobuild))]
  80     pub fn atomic_cxchg_failacq<T>(dst: *mut T, old: T, src: T) -> (T, bool);
  81     #[cfg(any(not(stage0), cargobuild))]
  82     pub fn atomic_cxchg_acq_failrelaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool);
  83     #[cfg(any(not(stage0), cargobuild))]
  84     pub fn atomic_cxchg_acqrel_failrelaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool);
  85
  86     pub fn atomic_cxchgweak<T>(dst: *mut T, old: T, src: T) -> (T, bool);
  87     pub fn atomic_cxchgweak_acq<T>(dst: *mut T, old: T, src: T) -> (T, bool);
  88     pub fn atomic_cxchgweak_rel<T>(dst: *mut T, old: T, src: T) -> (T, bool);
  89     pub fn atomic_cxchgweak_acqrel<T>(dst: *mut T, old: T, src: T) -> (T, bool);
  90     pub fn atomic_cxchgweak_relaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool);
  91     pub fn atomic_cxchgweak_failrelaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool);
  92     pub fn atomic_cxchgweak_failacq<T>(dst: *mut T, old: T, src: T) -> (T, bool);
  93     pub fn atomic_cxchgweak_acq_failrelaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool);
  94     pub fn atomic_cxchgweak_acqrel_failrelaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool);
  95
  96     pub fn atomic_load<T>(src: *const T) -> T;
  97     pub fn atomic_load_acq<T>(src: *const T) -> T;
  98     pub fn atomic_load_relaxed<T>(src: *const T) -> T;
  99     pub fn atomic_load_unordered<T>(src: *const T) -> T;
 100
 101     pub fn atomic_store<T>(dst: *mut T, val: T);
 102     pub fn atomic_store_rel<T>(dst: *mut T, val: T);
 103     pub fn atomic_store_relaxed<T>(dst: *mut T, val: T);
 104     pub fn atomic_store_unordered<T>(dst: *mut T, val: T);
 105
 106     pub fn atomic_xchg<T>(dst: *mut T, src: T) -> T;
 107     pub fn atomic_xchg_acq<T>(dst: *mut T, src: T) -> T;
 108     pub fn atomic_xchg_rel<T>(dst: *mut T, src: T) -> T;
 109     pub fn atomic_xchg_acqrel<T>(dst: *mut T, src: T) -> T;
 110     pub fn atomic_xchg_relaxed<T>(dst: *mut T, src: T) -> T;
 111
 112     pub fn atomic_xadd<T>(dst: *mut T, src: T) -> T;
 113     pub fn atomic_xadd_acq<T>(dst: *mut T, src: T) -> T;
 114     pub fn atomic_xadd_rel<T>(dst: *mut T, src: T) -> T;
 115     pub fn atomic_xadd_acqrel<T>(dst: *mut T, src: T) -> T;
 116     pub fn atomic_xadd_relaxed<T>(dst: *mut T, src: T) -> T;
 117
 118     pub fn atomic_xsub<T>(dst: *mut T, src: T) -> T;
 119     pub fn atomic_xsub_acq<T>(dst: *mut T, src: T) -> T;
 120     pub fn atomic_xsub_rel<T>(dst: *mut T, src: T) -> T;
 121     pub fn atomic_xsub_acqrel<T>(dst: *mut T, src: T) -> T;
 122     pub fn atomic_xsub_relaxed<T>(dst: *mut T, src: T) -> T;
 123
 124     pub fn atomic_and<T>(dst: *mut T, src: T) -> T;
 125     pub fn atomic_and_acq<T>(dst: *mut T, src: T) -> T;
 126     pub fn atomic_and_rel<T>(dst: *mut T, src: T) -> T;
 127     pub fn atomic_and_acqrel<T>(dst: *mut T, src: T) -> T;
 128     pub fn atomic_and_relaxed<T>(dst: *mut T, src: T) -> T;
 129
 130     pub fn atomic_nand<T>(dst: *mut T, src: T) -> T;
 131     pub fn atomic_nand_acq<T>(dst: *mut T, src: T) -> T;
 132     pub fn atomic_nand_rel<T>(dst: *mut T, src: T) -> T;
 133     pub fn atomic_nand_acqrel<T>(dst: *mut T, src: T) -> T;
 134     pub fn atomic_nand_relaxed<T>(dst: *mut T, src: T) -> T;
 135
 136     pub fn atomic_or<T>(dst: *mut T, src: T) -> T;
 137     pub fn atomic_or_acq<T>(dst: *mut T, src: T) -> T;
 138     pub fn atomic_or_rel<T>(dst: *mut T, src: T) -> T;
 139     pub fn atomic_or_acqrel<T>(dst: *mut T, src: T) -> T;
 140     pub fn atomic_or_relaxed<T>(dst: *mut T, src: T) -> T;
 141
 142     pub fn atomic_xor<T>(dst: *mut T, src: T) -> T;
 143     pub fn atomic_xor_acq<T>(dst: *mut T, src: T) -> T;
 144     pub fn atomic_xor_rel<T>(dst: *mut T, src: T) -> T;
 145     pub fn atomic_xor_acqrel<T>(dst: *mut T, src: T) -> T;
 146     pub fn atomic_xor_relaxed<T>(dst: *mut T, src: T) -> T;
 147
 148     pub fn atomic_max<T>(dst: *mut T, src: T) -> T;
 149     pub fn atomic_max_acq<T>(dst: *mut T, src: T) -> T;
 150     pub fn atomic_max_rel<T>(dst: *mut T, src: T) -> T;
 151     pub fn atomic_max_acqrel<T>(dst: *mut T, src: T) -> T;
 152     pub fn atomic_max_relaxed<T>(dst: *mut T, src: T) -> T;
 153
 154     pub fn atomic_min<T>(dst: *mut T, src: T) -> T;
 155     pub fn atomic_min_acq<T>(dst: *mut T, src: T) -> T;
 156     pub fn atomic_min_rel<T>(dst: *mut T, src: T) -> T;
 157     pub fn atomic_min_acqrel<T>(dst: *mut T, src: T) -> T;
 158     pub fn atomic_min_relaxed<T>(dst: *mut T, src: T) -> T;
 159
 160     pub fn atomic_umin<T>(dst: *mut T, src: T) -> T;
 161     pub fn atomic_umin_acq<T>(dst: *mut T, src: T) -> T;
 162     pub fn atomic_umin_rel<T>(dst: *mut T, src: T) -> T;
 163     pub fn atomic_umin_acqrel<T>(dst: *mut T, src: T) -> T;
 164     pub fn atomic_umin_relaxed<T>(dst: *mut T, src: T) -> T;
 165
 166     pub fn atomic_umax<T>(dst: *mut T, src: T) -> T;
 167     pub fn atomic_umax_acq<T>(dst: *mut T, src: T) -> T;
 168     pub fn atomic_umax_rel<T>(dst: *mut T, src: T) -> T;
 169     pub fn atomic_umax_acqrel<T>(dst: *mut T, src: T) -> T;
 170     pub fn atomic_umax_relaxed<T>(dst: *mut T, src: T) -> T;
 171 }
 172
 173 extern "rust-intrinsic" {
 174
 175     pub fn atomic_fence();
 176     pub fn atomic_fence_acq();
 177     pub fn atomic_fence_rel();
 178     pub fn atomic_fence_acqrel();
 179
 180     /// A compiler-only memory barrier.
 181     ///
 182     /// Memory accesses will never be reordered across this barrier by the
 183     /// compiler, but no instructions will be emitted for it. This is
 184     /// appropriate for operations on the same thread that may be preempted,
 185     /// such as when interacting with signal handlers.
 186     pub fn atomic_singlethreadfence();
 187     pub fn atomic_singlethreadfence_acq();
 188     pub fn atomic_singlethreadfence_rel();
 189     pub fn atomic_singlethreadfence_acqrel();
 190
 191     /// Aborts the execution of the process.
 192     pub fn abort() -> !;
 193
 194     /// Tells LLVM that this point in the code is not reachable,
 195     /// enabling further optimizations.
 196     ///
 197     /// NB: This is very different from the `unreachable!()` macro!
 198     pub fn unreachable() -> !;
 199
 200     /// Informs the optimizer that a condition is always true.
 201     /// If the condition is false, the behavior is undefined.
 202     ///
 203     /// No code is generated for this intrinsic, but the optimizer will try
 204     /// to preserve it (and its condition) between passes, which may interfere
 205     /// with optimization of surrounding code and reduce performance. It should
 206     /// not be used if the invariant can be discovered by the optimizer on its
 207     /// own, or if it does not enable any significant optimizations.
 208     pub fn assume(b: bool);
 209
 210     /// Executes a breakpoint trap, for inspection by a debugger.
 211     pub fn breakpoint();
 212
 213     /// The size of a type in bytes.
 214     ///
 215     /// This is the exact number of bytes in memory taken up by a
 216     /// value of the given type. In other words, a memset of this size
 217     /// would *exactly* overwrite a value. When laid out in vectors
 218     /// and structures there may be additional padding between
 219     /// elements.
 220     pub fn size_of<T>() -> usize;
 221
 222     /// Moves a value to an uninitialized memory location.
 223     ///
 224     /// Drop glue is not run on the destination.
 225     pub fn move_val_init<T>(dst: *mut T, src: T);
 226
 227     pub fn min_align_of<T>() -> usize;
 228     pub fn pref_align_of<T>() -> usize;
 229
 230     pub fn size_of_val<T: ?Sized>(_: &T) -> usize;
 231     pub fn min_align_of_val<T: ?Sized>(_: &T) -> usize;
 232
 233     /// Executes the destructor (if any) of the pointed-to value.
 234     ///
 235     /// This has two use cases:
 236     ///
 237     /// * It is *required* to use `drop_in_place` to drop unsized types like
 238     ///   trait objects, because they can't be read out onto the stack and
 239     ///   dropped normally.
 240     ///
 241     /// * It is friendlier to the optimizer to do this over `ptr::read` when
 242     ///   dropping manually allocated memory (e.g. when writing Box/Rc/Vec),
 243     ///   as the compiler doesn't need to prove that it's sound to elide the
 244     ///   copy.
 245     ///
 246     /// # Undefined Behavior
 247     ///
 248     /// This has all the same safety problems as `ptr::read` with respect to
 249     /// invalid pointers, types, and double drops.
 250     #[stable(feature = "drop_in_place", since = "1.8.0")]
 251     pub fn drop_in_place<T: ?Sized>(to_drop: *mut T);
 252
 253     /// Gets a static string slice containing the name of a type.
 254     pub fn type_name<T: ?Sized>() -> &'static str;
 255
 256     /// Gets an identifier which is globally unique to the specified type. This
 257     /// function will return the same value for a type regardless of whichever
 258     /// crate it is invoked in.
 259     pub fn type_id<T: ?Sized + 'static>() -> u64;
 260
 261     /// Creates a value initialized to so that its drop flag,
 262     /// if any, says that it has been dropped.
 263     ///
 264     /// `init_dropped` is unsafe because it returns a datum with all
 265     /// of its bytes set to the drop flag, which generally does not
 266     /// correspond to a valid value.
 267     ///
 268     /// This intrinsic is likely to be deprecated in the future when
 269     /// Rust moves to non-zeroing dynamic drop (and thus removes the
 270     /// embedded drop flags that are being established by this
 271     /// intrinsic).
 272     pub fn init_dropped<T>() -> T;
 273
 274     /// Creates a value initialized to zero.
 275     ///
 276     /// `init` is unsafe because it returns a zeroed-out datum,
 277     /// which is unsafe unless T is `Copy`.  Also, even if T is
 278     /// `Copy`, an all-zero value may not correspond to any legitimate
 279     /// state for the type in question.
 280     pub fn init<T>() -> T;
 281
 282     /// Creates an uninitialized value.
 283     ///
 284     /// `uninit` is unsafe because there is no guarantee of what its
 285     /// contents are. In particular its drop-flag may be set to any
 286     /// state, which means it may claim either dropped or
 287     /// undropped. In the general case one must use `ptr::write` to
 288     /// initialize memory previous set to the result of `uninit`.
 289     pub fn uninit<T>() -> T;
 290
 291     /// Moves a value out of scope without running drop glue.
 292     pub fn forget<T>(_: T) -> ();
 293
 294     /// Unsafely transforms a value of one type into a value of another type.
 295     ///
 296     /// Both types must have the same size.
 297     ///
 298     /// # Examples
 299     ///
 300     /// ```
 301     /// use std::mem;
 302     ///
 303     /// let array: &[u8] = unsafe { mem::transmute("Rust") };
 304     /// assert_eq!(array, [82, 117, 115, 116]);
 305     /// ```
 306     #[stable(feature = "rust1", since = "1.0.0")]
 307     pub fn transmute<T, U>(e: T) -> U;
 308
 309     /// Gives the address for the return value of the enclosing function.
 310     ///
 311     /// Using this intrinsic in a function that does not use an out pointer
 312     /// will trigger a compiler error.
 313     pub fn return_address() -> *const u8;
 314
 315     /// Returns `true` if the actual type given as `T` requires drop
 316     /// glue; returns `false` if the actual type provided for `T`
 317     /// implements `Copy`.
 318     ///
 319     /// If the actual type neither requires drop glue nor implements
 320     /// `Copy`, then may return `true` or `false`.
 321     pub fn needs_drop<T>() -> bool;
 322
 323     /// Calculates the offset from a pointer.
 324     ///
 325     /// This is implemented as an intrinsic to avoid converting to and from an
 326     /// integer, since the conversion would throw away aliasing information.
 327     ///
 328     /// # Safety
 329     ///
 330     /// Both the starting and resulting pointer must be either in bounds or one
 331     /// byte past the end of an allocated object. If either pointer is out of
 332     /// bounds or arithmetic overflow occurs then any further use of the
 333     /// returned value will result in undefined behavior.
 334     pub fn offset<T>(dst: *const T, offset: isize) -> *const T;
 335
 336     /// Calculates the offset from a pointer, potentially wrapping.
 337     ///
 338     /// This is implemented as an intrinsic to avoid converting to and from an
 339     /// integer, since the conversion inhibits certain optimizations.
 340     ///
 341     /// # Safety
 342     ///
 343     /// Unlike the `offset` intrinsic, this intrinsic does not restrict the
 344     /// resulting pointer to point into or one byte past the end of an allocated
 345     /// object, and it wraps with two's complement arithmetic. The resulting
 346     /// value is not necessarily valid to be used to actually access memory.
 347     pub fn arith_offset<T>(dst: *const T, offset: isize) -> *const T;
 348
 349     /// Copies `count * size_of<T>` bytes from `src` to `dst`. The source
 350     /// and destination may *not* overlap.
 351     ///
 352     /// `copy_nonoverlapping` is semantically equivalent to C's `memcpy`.
 353     ///
 354     /// # Safety
 355     ///
 356     /// Beyond requiring that the program must be allowed to access both regions
 357     /// of memory, it is Undefined Behavior for source and destination to
 358     /// overlap. Care must also be taken with the ownership of `src` and
 359     /// `dst`. This method semantically moves the values of `src` into `dst`.
 360     /// However it does not drop the contents of `dst`, or prevent the contents
 361     /// of `src` from being dropped or used.
 362     ///
 363     /// # Examples
 364     ///
 365     /// A safe swap function:
 366     ///
 367     /// ```
 368     /// use std::mem;
 369     /// use std::ptr;
 370     ///
 371     /// # #[allow(dead_code)]
 372     /// fn swap<T>(x: &mut T, y: &mut T) {
 373     ///     unsafe {
 374     ///         // Give ourselves some scratch space to work with
 375     ///         let mut t: T = mem::uninitialized();
 376     ///
 377     ///         // Perform the swap, `&mut` pointers never alias
 378     ///         ptr::copy_nonoverlapping(x, &mut t, 1);
 379     ///         ptr::copy_nonoverlapping(y, x, 1);
 380     ///         ptr::copy_nonoverlapping(&t, y, 1);
 381     ///
 382     ///         // y and t now point to the same thing, but we need to completely forget `tmp`
 383     ///         // because it's no longer relevant.
 384     ///         mem::forget(t);
 385     ///     }
 386     /// }
 387     /// ```
 388     #[stable(feature = "rust1", since = "1.0.0")]
 389     pub fn copy_nonoverlapping<T>(src: *const T, dst: *mut T, count: usize);
 390
 391     /// Copies `count * size_of<T>` bytes from `src` to `dst`. The source
 392     /// and destination may overlap.
 393     ///
 394     /// `copy` is semantically equivalent to C's `memmove`.
 395     ///
 396     /// # Safety
 397     ///
 398     /// Care must be taken with the ownership of `src` and `dst`.
 399     /// This method semantically moves the values of `src` into `dst`.
 400     /// However it does not drop the contents of `dst`, or prevent the contents of `src`
 401     /// from being dropped or used.
 402     ///
 403     /// # Examples
 404     ///
 405     /// Efficiently create a Rust vector from an unsafe buffer:
 406     ///
 407     /// ```
 408     /// use std::ptr;
 409     ///
 410     /// # #[allow(dead_code)]
 411     /// unsafe fn from_buf_raw<T>(ptr: *const T, elts: usize) -> Vec<T> {
 412     ///     let mut dst = Vec::with_capacity(elts);
 413     ///     dst.set_len(elts);
 414     ///     ptr::copy(ptr, dst.as_mut_ptr(), elts);
 415     ///     dst
 416     /// }
 417     /// ```
 418     ///
 419     #[stable(feature = "rust1", since = "1.0.0")]
 420     pub fn copy<T>(src: *const T, dst: *mut T, count: usize);
 421
 422     /// Invokes memset on the specified pointer, setting `count * size_of::<T>()`
 423     /// bytes of memory starting at `dst` to `val`.
 424     #[stable(feature = "rust1", since = "1.0.0")]
 425     pub fn write_bytes<T>(dst: *mut T, val: u8, count: usize);
 426
 427     /// Equivalent to the appropriate `llvm.memcpy.p0i8.0i8.*` intrinsic, with
 428     /// a size of `count` * `size_of::<T>()` and an alignment of
 429     /// `min_align_of::<T>()`
 430     ///
 431     /// The volatile parameter is set to `true`, so it will not be optimized out.
 432     pub fn volatile_copy_nonoverlapping_memory<T>(dst: *mut T, src: *const T,
 433                                                   count: usize);
 434     /// Equivalent to the appropriate `llvm.memmove.p0i8.0i8.*` intrinsic, with
 435     /// a size of `count` * `size_of::<T>()` and an alignment of
 436     /// `min_align_of::<T>()`
 437     ///
 438     /// The volatile parameter is set to `true`, so it will not be optimized out.
 439     pub fn volatile_copy_memory<T>(dst: *mut T, src: *const T, count: usize);
 440     /// Equivalent to the appropriate `llvm.memset.p0i8.*` intrinsic, with a
 441     /// size of `count` * `size_of::<T>()` and an alignment of
 442     /// `min_align_of::<T>()`.
 443     ///
 444     /// The volatile parameter is set to `true`, so it will not be optimized out.
 445     pub fn volatile_set_memory<T>(dst: *mut T, val: u8, count: usize);
 446
 447     /// Perform a volatile load from the `src` pointer.
 448     pub fn volatile_load<T>(src: *const T) -> T;
 449     /// Perform a volatile store to the `dst` pointer.
 450     pub fn volatile_store<T>(dst: *mut T, val: T);
 451
 452     /// Returns the square root of an `f32`
 453     pub fn sqrtf32(x: f32) -> f32;
 454     /// Returns the square root of an `f64`
 455     pub fn sqrtf64(x: f64) -> f64;
 456
 457     /// Raises an `f32` to an integer power.
 458     pub fn powif32(a: f32, x: i32) -> f32;
 459     /// Raises an `f64` to an integer power.
 460     pub fn powif64(a: f64, x: i32) -> f64;
 461
 462     /// Returns the sine of an `f32`.
 463     pub fn sinf32(x: f32) -> f32;
 464     /// Returns the sine of an `f64`.
 465     pub fn sinf64(x: f64) -> f64;
 466
 467     /// Returns the cosine of an `f32`.
 468     pub fn cosf32(x: f32) -> f32;
 469     /// Returns the cosine of an `f64`.
 470     pub fn cosf64(x: f64) -> f64;
 471
 472     /// Raises an `f32` to an `f32` power.
 473     pub fn powf32(a: f32, x: f32) -> f32;
 474     /// Raises an `f64` to an `f64` power.
 475     pub fn powf64(a: f64, x: f64) -> f64;
 476
 477     /// Returns the exponential of an `f32`.
 478     pub fn expf32(x: f32) -> f32;
 479     /// Returns the exponential of an `f64`.
 480     pub fn expf64(x: f64) -> f64;
 481
 482     /// Returns 2 raised to the power of an `f32`.
 483     pub fn exp2f32(x: f32) -> f32;
 484     /// Returns 2 raised to the power of an `f64`.
 485     pub fn exp2f64(x: f64) -> f64;
 486
 487     /// Returns the natural logarithm of an `f32`.
 488     pub fn logf32(x: f32) -> f32;
 489     /// Returns the natural logarithm of an `f64`.
 490     pub fn logf64(x: f64) -> f64;
 491
 492     /// Returns the base 10 logarithm of an `f32`.
 493     pub fn log10f32(x: f32) -> f32;
 494     /// Returns the base 10 logarithm of an `f64`.
 495     pub fn log10f64(x: f64) -> f64;
 496
 497     /// Returns the base 2 logarithm of an `f32`.
 498     pub fn log2f32(x: f32) -> f32;
 499     /// Returns the base 2 logarithm of an `f64`.
 500     pub fn log2f64(x: f64) -> f64;
 501
 502     /// Returns `a * b + c` for `f32` values.
 503     pub fn fmaf32(a: f32, b: f32, c: f32) -> f32;
 504     /// Returns `a * b + c` for `f64` values.
 505     pub fn fmaf64(a: f64, b: f64, c: f64) -> f64;
 506
 507     /// Returns the absolute value of an `f32`.
 508     pub fn fabsf32(x: f32) -> f32;
 509     /// Returns the absolute value of an `f64`.
 510     pub fn fabsf64(x: f64) -> f64;
 511
 512     /// Copies the sign from `y` to `x` for `f32` values.
 513     pub fn copysignf32(x: f32, y: f32) -> f32;
 514     /// Copies the sign from `y` to `x` for `f64` values.
 515     pub fn copysignf64(x: f64, y: f64) -> f64;
 516
 517     /// Returns the largest integer less than or equal to an `f32`.
 518     pub fn floorf32(x: f32) -> f32;
 519     /// Returns the largest integer less than or equal to an `f64`.
 520     pub fn floorf64(x: f64) -> f64;
 521
 522     /// Returns the smallest integer greater than or equal to an `f32`.
 523     pub fn ceilf32(x: f32) -> f32;
 524     /// Returns the smallest integer greater than or equal to an `f64`.
 525     pub fn ceilf64(x: f64) -> f64;
 526
 527     /// Returns the integer part of an `f32`.
 528     pub fn truncf32(x: f32) -> f32;
 529     /// Returns the integer part of an `f64`.
 530     pub fn truncf64(x: f64) -> f64;
 531
 532     /// Returns the nearest integer to an `f32`. May raise an inexact floating-point exception
 533     /// if the argument is not an integer.
 534     pub fn rintf32(x: f32) -> f32;
 535     /// Returns the nearest integer to an `f64`. May raise an inexact floating-point exception
 536     /// if the argument is not an integer.
 537     pub fn rintf64(x: f64) -> f64;
 538
 539     /// Returns the nearest integer to an `f32`.
 540     pub fn nearbyintf32(x: f32) -> f32;
 541     /// Returns the nearest integer to an `f64`.
 542     pub fn nearbyintf64(x: f64) -> f64;
 543
 544     /// Returns the nearest integer to an `f32`. Rounds half-way cases away from zero.
 545     pub fn roundf32(x: f32) -> f32;
 546     /// Returns the nearest integer to an `f64`. Rounds half-way cases away from zero.
 547     pub fn roundf64(x: f64) -> f64;
 548
 549     /// Float addition that allows optimizations based on algebraic rules.
 550     /// May assume inputs are finite.
 551     #[cfg(not(stage0))]
 552     pub fn fadd_fast<T>(a: T, b: T) -> T;
 553
 554     /// Float subtraction that allows optimizations based on algebraic rules.
 555     /// May assume inputs are finite.
 556     #[cfg(not(stage0))]
 557     pub fn fsub_fast<T>(a: T, b: T) -> T;
 558
 559     /// Float multiplication that allows optimizations based on algebraic rules.
 560     /// May assume inputs are finite.
 561     #[cfg(not(stage0))]
 562     pub fn fmul_fast<T>(a: T, b: T) -> T;
 563
 564     /// Float division that allows optimizations based on algebraic rules.
 565     /// May assume inputs are finite.
 566     #[cfg(not(stage0))]
 567     pub fn fdiv_fast<T>(a: T, b: T) -> T;
 568
 569     /// Float remainder that allows optimizations based on algebraic rules.
 570     /// May assume inputs are finite.
 571     #[cfg(not(stage0))]
 572     pub fn frem_fast<T>(a: T, b: T) -> T;
 573
 574
 575     /// Returns the number of bits set in an integer type `T`
 576     pub fn ctpop<T>(x: T) -> T;
 577
 578     /// Returns the number of leading bits unset in an integer type `T`
 579     pub fn ctlz<T>(x: T) -> T;
 580
 581     /// Returns the number of trailing bits unset in an integer type `T`
 582     pub fn cttz<T>(x: T) -> T;
 583
 584     /// Reverses the bytes in an integer type `T`.
 585     pub fn bswap<T>(x: T) -> T;
 586
 587     /// Performs checked integer addition.
 588     pub fn add_with_overflow<T>(x: T, y: T) -> (T, bool);
 589
 590     /// Performs checked integer subtraction
 591     pub fn sub_with_overflow<T>(x: T, y: T) -> (T, bool);
 592
 593     /// Performs checked integer multiplication
 594     pub fn mul_with_overflow<T>(x: T, y: T) -> (T, bool);
 595
 596     /// Performs an unchecked division, resulting in undefined behavior
 597     /// where y = 0 or x = `T::min_value()` and y = -1
 598     pub fn unchecked_div<T>(x: T, y: T) -> T;
 599     /// Returns the remainder of an unchecked division, resulting in
 600     /// undefined behavior where y = 0 or x = `T::min_value()` and y = -1
 601     pub fn unchecked_rem<T>(x: T, y: T) -> T;
 602
 603     /// Returns (a + b) mod 2^N, where N is the width of T in bits.
 604     pub fn overflowing_add<T>(a: T, b: T) -> T;
 605     /// Returns (a - b) mod 2^N, where N is the width of T in bits.
 606     pub fn overflowing_sub<T>(a: T, b: T) -> T;
 607     /// Returns (a * b) mod 2^N, where N is the width of T in bits.
 608     pub fn overflowing_mul<T>(a: T, b: T) -> T;
 609
 610     /// Returns the value of the discriminant for the variant in 'v',
 611     /// cast to a `u64`; if `T` has no discriminant, returns 0.
 612     pub fn discriminant_value<T>(v: &T) -> u64;
 613
 614     /// Rust's "try catch" construct which invokes the function pointer `f` with
 615     /// the data pointer `data`.
 616     ///
 617     /// The third pointer is a target-specific data pointer which is filled in
 618     /// with the specifics of the exception that occurred. For examples on Unix
 619     /// platforms this is a `*mut *mut T` which is filled in by the compiler and
 620     /// on MSVC it's `*mut [usize; 2]`. For more information see the compiler's
 621     /// source as well as std's catch implementation.
 622     pub fn try(f: fn(*mut u8), data: *mut u8, local_ptr: *mut u8) -> i32;
 623 }