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// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! rustc compiler intrinsics.
//!
//! The corresponding definitions are in librustc_trans/intrinsic.rs.
//!
//! # Volatiles
//!
//! The volatile intrinsics provide operations intended to act on I/O
//! memory, which are guaranteed to not be reordered by the compiler
//! across other volatile intrinsics. See the LLVM documentation on
//! [[volatile]].
//!
//! [volatile]: http://llvm.org/docs/LangRef.html#volatile-memory-accesses
//!
//! # Atomics
//!
//! The atomic intrinsics provide common atomic operations on machine
//! words, with multiple possible memory orderings. They obey the same
//! semantics as C++11. See the LLVM documentation on [[atomics]].
//!
//! [atomics]: http://llvm.org/docs/Atomics.html
//!
//! A quick refresher on memory ordering:
//!
//! * Acquire - a barrier for acquiring a lock. Subsequent reads and writes
//! take place after the barrier.
//! * Release - a barrier for releasing a lock. Preceding reads and writes
//! take place before the barrier.
//! * Sequentially consistent - sequentially consistent operations are
//! guaranteed to happen in order. This is the standard mode for working
//! with atomic types and is equivalent to Java's `volatile`.
#![unstable(feature = "core_intrinsics",
reason = "intrinsics are unlikely to ever be stabilized, instead \
they should be used through stabilized interfaces \
in the rest of the standard library",
issue = "0")]
#![allow(missing_docs)]
use marker::Sized;
extern "rust-intrinsic" {
// NB: These intrinsics take raw pointers because they mutate aliased
// memory, which is not valid for either `&` or `&mut`.
pub fn atomic_cxchg<T>(dst: *mut T, old: T, src: T) -> (T, bool);
pub fn atomic_cxchg_acq<T>(dst: *mut T, old: T, src: T) -> (T, bool);
pub fn atomic_cxchg_rel<T>(dst: *mut T, old: T, src: T) -> (T, bool);
pub fn atomic_cxchg_acqrel<T>(dst: *mut T, old: T, src: T) -> (T, bool);
pub fn atomic_cxchg_relaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool);
pub fn atomic_cxchg_failrelaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool);
pub fn atomic_cxchg_failacq<T>(dst: *mut T, old: T, src: T) -> (T, bool);
pub fn atomic_cxchg_acq_failrelaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool);
pub fn atomic_cxchg_acqrel_failrelaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool);
pub fn atomic_cxchgweak<T>(dst: *mut T, old: T, src: T) -> (T, bool);
pub fn atomic_cxchgweak_acq<T>(dst: *mut T, old: T, src: T) -> (T, bool);
pub fn atomic_cxchgweak_rel<T>(dst: *mut T, old: T, src: T) -> (T, bool);
pub fn atomic_cxchgweak_acqrel<T>(dst: *mut T, old: T, src: T) -> (T, bool);
pub fn atomic_cxchgweak_relaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool);
pub fn atomic_cxchgweak_failrelaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool);
pub fn atomic_cxchgweak_failacq<T>(dst: *mut T, old: T, src: T) -> (T, bool);
pub fn atomic_cxchgweak_acq_failrelaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool);
pub fn atomic_cxchgweak_acqrel_failrelaxed<T>(dst: *mut T, old: T, src: T) -> (T, bool);
pub fn atomic_load<T>(src: *const T) -> T;
pub fn atomic_load_acq<T>(src: *const T) -> T;
pub fn atomic_load_relaxed<T>(src: *const T) -> T;
pub fn atomic_load_unordered<T>(src: *const T) -> T;
pub fn atomic_store<T>(dst: *mut T, val: T);
pub fn atomic_store_rel<T>(dst: *mut T, val: T);
pub fn atomic_store_relaxed<T>(dst: *mut T, val: T);
pub fn atomic_store_unordered<T>(dst: *mut T, val: T);
pub fn atomic_xchg<T>(dst: *mut T, src: T) -> T;
pub fn atomic_xchg_acq<T>(dst: *mut T, src: T) -> T;
pub fn atomic_xchg_rel<T>(dst: *mut T, src: T) -> T;
pub fn atomic_xchg_acqrel<T>(dst: *mut T, src: T) -> T;
pub fn atomic_xchg_relaxed<T>(dst: *mut T, src: T) -> T;
pub fn atomic_xadd<T>(dst: *mut T, src: T) -> T;
pub fn atomic_xadd_acq<T>(dst: *mut T, src: T) -> T;
pub fn atomic_xadd_rel<T>(dst: *mut T, src: T) -> T;
pub fn atomic_xadd_acqrel<T>(dst: *mut T, src: T) -> T;
pub fn atomic_xadd_relaxed<T>(dst: *mut T, src: T) -> T;
pub fn atomic_xsub<T>(dst: *mut T, src: T) -> T;
pub fn atomic_xsub_acq<T>(dst: *mut T, src: T) -> T;
pub fn atomic_xsub_rel<T>(dst: *mut T, src: T) -> T;
pub fn atomic_xsub_acqrel<T>(dst: *mut T, src: T) -> T;
pub fn atomic_xsub_relaxed<T>(dst: *mut T, src: T) -> T;
pub fn atomic_and<T>(dst: *mut T, src: T) -> T;
pub fn atomic_and_acq<T>(dst: *mut T, src: T) -> T;
pub fn atomic_and_rel<T>(dst: *mut T, src: T) -> T;
pub fn atomic_and_acqrel<T>(dst: *mut T, src: T) -> T;
pub fn atomic_and_relaxed<T>(dst: *mut T, src: T) -> T;
pub fn atomic_nand<T>(dst: *mut T, src: T) -> T;
pub fn atomic_nand_acq<T>(dst: *mut T, src: T) -> T;
pub fn atomic_nand_rel<T>(dst: *mut T, src: T) -> T;
pub fn atomic_nand_acqrel<T>(dst: *mut T, src: T) -> T;
pub fn atomic_nand_relaxed<T>(dst: *mut T, src: T) -> T;
pub fn atomic_or<T>(dst: *mut T, src: T) -> T;
pub fn atomic_or_acq<T>(dst: *mut T, src: T) -> T;
pub fn atomic_or_rel<T>(dst: *mut T, src: T) -> T;
pub fn atomic_or_acqrel<T>(dst: *mut T, src: T) -> T;
pub fn atomic_or_relaxed<T>(dst: *mut T, src: T) -> T;
pub fn atomic_xor<T>(dst: *mut T, src: T) -> T;
pub fn atomic_xor_acq<T>(dst: *mut T, src: T) -> T;
pub fn atomic_xor_rel<T>(dst: *mut T, src: T) -> T;
pub fn atomic_xor_acqrel<T>(dst: *mut T, src: T) -> T;
pub fn atomic_xor_relaxed<T>(dst: *mut T, src: T) -> T;
pub fn atomic_max<T>(dst: *mut T, src: T) -> T;
pub fn atomic_max_acq<T>(dst: *mut T, src: T) -> T;
pub fn atomic_max_rel<T>(dst: *mut T, src: T) -> T;
pub fn atomic_max_acqrel<T>(dst: *mut T, src: T) -> T;
pub fn atomic_max_relaxed<T>(dst: *mut T, src: T) -> T;
pub fn atomic_min<T>(dst: *mut T, src: T) -> T;
pub fn atomic_min_acq<T>(dst: *mut T, src: T) -> T;
pub fn atomic_min_rel<T>(dst: *mut T, src: T) -> T;
pub fn atomic_min_acqrel<T>(dst: *mut T, src: T) -> T;
pub fn atomic_min_relaxed<T>(dst: *mut T, src: T) -> T;
pub fn atomic_umin<T>(dst: *mut T, src: T) -> T;
pub fn atomic_umin_acq<T>(dst: *mut T, src: T) -> T;
pub fn atomic_umin_rel<T>(dst: *mut T, src: T) -> T;
pub fn atomic_umin_acqrel<T>(dst: *mut T, src: T) -> T;
pub fn atomic_umin_relaxed<T>(dst: *mut T, src: T) -> T;
pub fn atomic_umax<T>(dst: *mut T, src: T) -> T;
pub fn atomic_umax_acq<T>(dst: *mut T, src: T) -> T;
pub fn atomic_umax_rel<T>(dst: *mut T, src: T) -> T;
pub fn atomic_umax_acqrel<T>(dst: *mut T, src: T) -> T;
pub fn atomic_umax_relaxed<T>(dst: *mut T, src: T) -> T;
}
extern "rust-intrinsic" {
pub fn atomic_fence();
pub fn atomic_fence_acq();
pub fn atomic_fence_rel();
pub fn atomic_fence_acqrel();
/// A compiler-only memory barrier.
///
/// Memory accesses will never be reordered across this barrier by the
/// compiler, but no instructions will be emitted for it. This is
/// appropriate for operations on the same thread that may be preempted,
/// such as when interacting with signal handlers.
pub fn atomic_singlethreadfence();
pub fn atomic_singlethreadfence_acq();
pub fn atomic_singlethreadfence_rel();
pub fn atomic_singlethreadfence_acqrel();
/// Magic intrinsic that derives its meaning from attributes
/// attached to the function.
///
/// For example, dataflow uses this to inject static assertions so
/// that `rustc_peek(potentially_uninitialized)` would actually
/// double-check that dataflow did indeed compute that it is
/// uninitialized at that point in the control flow.
pub fn rustc_peek<T>(_: T) -> T;
/// Aborts the execution of the process.
pub fn abort() -> !;
/// Tells LLVM that this point in the code is not reachable,
/// enabling further optimizations.
///
/// NB: This is very different from the `unreachable!()` macro!
pub fn unreachable() -> !;
/// Informs the optimizer that a condition is always true.
/// If the condition is false, the behavior is undefined.
///
/// No code is generated for this intrinsic, but the optimizer will try
/// to preserve it (and its condition) between passes, which may interfere
/// with optimization of surrounding code and reduce performance. It should
/// not be used if the invariant can be discovered by the optimizer on its
/// own, or if it does not enable any significant optimizations.
pub fn assume(b: bool);
/// Executes a breakpoint trap, for inspection by a debugger.
pub fn breakpoint();
/// The size of a type in bytes.
///
/// More specifically, this is the offset in bytes between successive
/// items of the same type, including alignment padding.
pub fn size_of<T>() -> usize;
/// Moves a value to an uninitialized memory location.
///
/// Drop glue is not run on the destination.
pub fn move_val_init<T>(dst: *mut T, src: T);
pub fn min_align_of<T>() -> usize;
pub fn pref_align_of<T>() -> usize;
pub fn size_of_val<T: ?Sized>(_: &T) -> usize;
pub fn min_align_of_val<T: ?Sized>(_: &T) -> usize;
/// Executes the destructor (if any) of the pointed-to value.
///
/// This has two use cases:
///
/// * It is *required* to use `drop_in_place` to drop unsized types like
/// trait objects, because they can't be read out onto the stack and
/// dropped normally.
///
/// * It is friendlier to the optimizer to do this over `ptr::read` when
/// dropping manually allocated memory (e.g. when writing Box/Rc/Vec),
/// as the compiler doesn't need to prove that it's sound to elide the
/// copy.
///
/// # Undefined Behavior
///
/// This has all the same safety problems as `ptr::read` with respect to
/// invalid pointers, types, and double drops.
#[stable(feature = "drop_in_place", since = "1.8.0")]
pub fn drop_in_place<T: ?Sized>(to_drop: *mut T);
/// Gets a static string slice containing the name of a type.
pub fn type_name<T: ?Sized>() -> &'static str;
/// Gets an identifier which is globally unique to the specified type. This
/// function will return the same value for a type regardless of whichever
/// crate it is invoked in.
pub fn type_id<T: ?Sized + 'static>() -> u64;
/// Creates a value initialized to so that its drop flag,
/// if any, says that it has been dropped.
///
/// `init_dropped` is unsafe because it returns a datum with all
/// of its bytes set to the drop flag, which generally does not
/// correspond to a valid value.
///
/// This intrinsic is likely to be deprecated in the future when
/// Rust moves to non-zeroing dynamic drop (and thus removes the
/// embedded drop flags that are being established by this
/// intrinsic).
pub fn init_dropped<T>() -> T;
/// Creates a value initialized to zero.
///
/// `init` is unsafe because it returns a zeroed-out datum,
/// which is unsafe unless T is `Copy`. Also, even if T is
/// `Copy`, an all-zero value may not correspond to any legitimate
/// state for the type in question.
pub fn init<T>() -> T;
/// Creates an uninitialized value.
///
/// `uninit` is unsafe because there is no guarantee of what its
/// contents are. In particular its drop-flag may be set to any
/// state, which means it may claim either dropped or
/// undropped. In the general case one must use `ptr::write` to
/// initialize memory previous set to the result of `uninit`.
pub fn uninit<T>() -> T;
/// Moves a value out of scope without running drop glue.
pub fn forget<T>(_: T) -> ();
/// Reinterprets the bits of a value of one type as another type; both types
/// must have the same size. Neither the original, nor the result, may be an
/// [invalid value] (../../nomicon/meet-safe-and-unsafe.html).
///
/// `transmute` is semantically equivalent to a bitwise move of one type
/// into another. It copies the bits from the destination type into the
/// source type, then forgets the original. It's equivalent to C's `memcpy`
/// under the hood, just like `transmute_copy`.
///
/// `transmute` is incredibly unsafe. There are a vast number of ways to
/// cause undefined behavior with this function. `transmute` should be
/// the absolute last resort.
///
/// The [nomicon](../../nomicon/transmutes.html) has additional
/// documentation.
///
/// # Examples
///
/// There are a few things that `transmute` is really useful for.
///
/// Getting the bitpattern of a floating point type (or, more generally,
/// type punning, when `T` and `U` aren't pointers):
///
/// ```
/// let bitpattern = unsafe {
/// std::mem::transmute::<f32, u32>(1.0)
/// };
/// assert_eq!(bitpattern, 0x3F800000);
/// ```
///
/// Turning a pointer into a function pointer:
///
/// ```
/// fn foo() -> i32 {
/// 0
/// }
/// let pointer = foo as *const ();
/// let function = unsafe {
/// std::mem::transmute::<*const (), fn() -> i32>(pointer)
/// };
/// assert_eq!(function(), 0);
/// ```
///
/// Extending a lifetime, or shortening an invariant lifetime; this is
/// advanced, very unsafe rust:
///
/// ```
/// struct R<'a>(&'a i32);
/// unsafe fn extend_lifetime<'b>(r: R<'b>) -> R<'static> {
/// std::mem::transmute::<R<'b>, R<'static>>(r)
/// }
///
/// unsafe fn shorten_invariant_lifetime<'b, 'c>(r: &'b mut R<'static>)
/// -> &'b mut R<'c> {
/// std::mem::transmute::<&'b mut R<'static>, &'b mut R<'c>>(r)
/// }
/// ```
///
/// # Alternatives
///
/// However, many uses of `transmute` can be achieved through other means.
/// `transmute` can transform any type into any other, with just the caveat
/// that they're the same size, and often interesting results occur. Below
/// are common applications of `transmute` which can be replaced with safe
/// applications of `as`:
///
/// Turning a pointer into a `usize`:
///
/// ```
/// let ptr = &0;
/// let ptr_num_transmute = unsafe {
/// std::mem::transmute::<&i32, usize>(ptr)
/// };
/// // Use an `as` cast instead
/// let ptr_num_cast = ptr as *const i32 as usize;
/// ```
///
/// Turning a `*mut T` into an `&mut T`:
///
/// ```
/// let ptr: *mut i32 = &mut 0;
/// let ref_transmuted = unsafe {
/// std::mem::transmute::<*mut i32, &mut i32>(ptr)
/// };
/// // Use a reborrow instead
/// let ref_casted = unsafe { &mut *ptr };
/// ```
///
/// Turning an `&mut T` into an `&mut U`:
///
/// ```
/// let ptr = &mut 0;
/// let val_transmuted = unsafe {
/// std::mem::transmute::<&mut i32, &mut u32>(ptr)
/// };
/// // Now, put together `as` and reborrowing - note the chaining of `as`
/// // `as` is not transitive
/// let val_casts = unsafe { &mut *(ptr as *mut i32 as *mut u32) };
/// ```
///
/// Turning an `&str` into an `&[u8]`:
///
/// ```
/// // this is not a good way to do this.
/// let slice = unsafe { std::mem::transmute::<&str, &[u8]>("Rust") };
/// assert_eq!(slice, &[82, 117, 115, 116]);
/// // You could use `str::as_bytes`
/// let slice = "Rust".as_bytes();
/// assert_eq!(slice, &[82, 117, 115, 116]);
/// // Or, just use a byte string, if you have control over the string
/// // literal
/// assert_eq!(b"Rust", &[82, 117, 115, 116]);
/// ```
///
/// Turning a `Vec<&T>` into a `Vec<Option<&T>>`:
///
/// ```
/// let store = [0, 1, 2, 3];
/// let mut v_orig = store.iter().collect::<Vec<&i32>>();
/// // Using transmute: this is Undefined Behavior, and a bad idea.
/// // However, it is no-copy.
/// let v_transmuted = unsafe {
/// std::mem::transmute::<Vec<&i32>, Vec<Option<&i32>>>(
/// v_orig.clone())
/// };
/// // This is the suggested, safe way.
/// // It does copy the entire Vector, though, into a new array.
/// let v_collected = v_orig.clone()
/// .into_iter()
/// .map(|r| Some(r))
/// .collect::<Vec<Option<&i32>>>();
/// // The no-copy, unsafe way, still using transmute, but not UB.
/// // This is equivalent to the original, but safer, and reuses the
/// // same Vec internals. Therefore the new inner type must have the
/// // exact same size, and the same or lesser alignment, as the old
/// // type. The same caveats exist for this method as transmute, for
/// // the original inner type (`&i32`) to the converted inner type
/// // (`Option<&i32>`), so read the nomicon pages linked above.
/// let v_from_raw = unsafe {
/// Vec::from_raw_parts(v_orig.as_mut_ptr(),
/// v_orig.len(),
/// v_orig.capacity())
/// };
/// std::mem::forget(v_orig);
/// ```
///
/// Implementing `split_at_mut`:
///
/// ```
/// use std::{slice, mem};
/// // There are multiple ways to do this; and there are multiple problems
/// // with the following, transmute, way.
/// fn split_at_mut_transmute<T>(slice: &mut [T], mid: usize)
/// -> (&mut [T], &mut [T]) {
/// let len = slice.len();
/// assert!(mid <= len);
/// unsafe {
/// let slice2 = mem::transmute::<&mut [T], &mut [T]>(slice);
/// // first: transmute is not typesafe; all it checks is that T and
/// // U are of the same size. Second, right here, you have two
/// // mutable references pointing to the same memory.
/// (&mut slice[0..mid], &mut slice2[mid..len])
/// }
/// }
/// // This gets rid of the typesafety problems; `&mut *` will *only* give
/// // you an `&mut T` from an `&mut T` or `*mut T`.
/// fn split_at_mut_casts<T>(slice: &mut [T], mid: usize)
/// -> (&mut [T], &mut [T]) {
/// let len = slice.len();
/// assert!(mid <= len);
/// unsafe {
/// let slice2 = &mut *(slice as *mut [T]);
/// // however, you still have two mutable references pointing to
/// // the same memory.
/// (&mut slice[0..mid], &mut slice2[mid..len])
/// }
/// }
/// // This is how the standard library does it. This is the best method, if
/// // you need to do something like this
/// fn split_at_stdlib<T>(slice: &mut [T], mid: usize)
/// -> (&mut [T], &mut [T]) {
/// let len = slice.len();
/// assert!(mid <= len);
/// unsafe {
/// let ptr = slice.as_mut_ptr();
/// // This now has three mutable references pointing at the same
/// // memory. `slice`, the rvalue ret.0, and the rvalue ret.1.
/// // `slice` is never used after `let ptr = ...`, and so one can
/// // treat it as "dead", and therefore, you only have two real
/// // mutable slices.
/// (slice::from_raw_parts_mut(ptr, mid),
/// slice::from_raw_parts_mut(ptr.offset(mid as isize), len - mid))
/// }
/// }
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn transmute<T, U>(e: T) -> U;
/// Returns `true` if the actual type given as `T` requires drop
/// glue; returns `false` if the actual type provided for `T`
/// implements `Copy`.
///
/// If the actual type neither requires drop glue nor implements
/// `Copy`, then may return `true` or `false`.
pub fn needs_drop<T>() -> bool;
/// Calculates the offset from a pointer.
///
/// This is implemented as an intrinsic to avoid converting to and from an
/// integer, since the conversion would throw away aliasing information.
///
/// # Safety
///
/// Both the starting and resulting pointer must be either in bounds or one
/// byte past the end of an allocated object. If either pointer is out of
/// bounds or arithmetic overflow occurs then any further use of the
/// returned value will result in undefined behavior.
pub fn offset<T>(dst: *const T, offset: isize) -> *const T;
/// Calculates the offset from a pointer, potentially wrapping.
///
/// This is implemented as an intrinsic to avoid converting to and from an
/// integer, since the conversion inhibits certain optimizations.
///
/// # Safety
///
/// Unlike the `offset` intrinsic, this intrinsic does not restrict the
/// resulting pointer to point into or one byte past the end of an allocated
/// object, and it wraps with two's complement arithmetic. The resulting
/// value is not necessarily valid to be used to actually access memory.
pub fn arith_offset<T>(dst: *const T, offset: isize) -> *const T;
/// Copies `count * size_of<T>` bytes from `src` to `dst`. The source
/// and destination may *not* overlap.
///
/// `copy_nonoverlapping` is semantically equivalent to C's `memcpy`.
///
/// # Safety
///
/// Beyond requiring that the program must be allowed to access both regions
/// of memory, it is Undefined Behavior for source and destination to
/// overlap. Care must also be taken with the ownership of `src` and
/// `dst`. This method semantically moves the values of `src` into `dst`.
/// However it does not drop the contents of `dst`, or prevent the contents
/// of `src` from being dropped or used.
///
/// # Examples
///
/// A safe swap function:
///
/// ```
/// use std::mem;
/// use std::ptr;
///
/// # #[allow(dead_code)]
/// fn swap<T>(x: &mut T, y: &mut T) {
/// unsafe {
/// // Give ourselves some scratch space to work with
/// let mut t: T = mem::uninitialized();
///
/// // Perform the swap, `&mut` pointers never alias
/// ptr::copy_nonoverlapping(x, &mut t, 1);
/// ptr::copy_nonoverlapping(y, x, 1);
/// ptr::copy_nonoverlapping(&t, y, 1);
///
/// // y and t now point to the same thing, but we need to completely forget `tmp`
/// // because it's no longer relevant.
/// mem::forget(t);
/// }
/// }
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn copy_nonoverlapping<T>(src: *const T, dst: *mut T, count: usize);
/// Copies `count * size_of<T>` bytes from `src` to `dst`. The source
/// and destination may overlap.
///
/// `copy` is semantically equivalent to C's `memmove`.
///
/// # Safety
///
/// Care must be taken with the ownership of `src` and `dst`.
/// This method semantically moves the values of `src` into `dst`.
/// However it does not drop the contents of `dst`, or prevent the contents of `src`
/// from being dropped or used.
///
/// # Examples
///
/// Efficiently create a Rust vector from an unsafe buffer:
///
/// ```
/// use std::ptr;
///
/// # #[allow(dead_code)]
/// unsafe fn from_buf_raw<T>(ptr: *const T, elts: usize) -> Vec<T> {
/// let mut dst = Vec::with_capacity(elts);
/// dst.set_len(elts);
/// ptr::copy(ptr, dst.as_mut_ptr(), elts);
/// dst
/// }
/// ```
///
#[stable(feature = "rust1", since = "1.0.0")]
pub fn copy<T>(src: *const T, dst: *mut T, count: usize);
/// Invokes memset on the specified pointer, setting `count * size_of::<T>()`
/// bytes of memory starting at `dst` to `val`.
#[stable(feature = "rust1", since = "1.0.0")]
pub fn write_bytes<T>(dst: *mut T, val: u8, count: usize);
/// Equivalent to the appropriate `llvm.memcpy.p0i8.0i8.*` intrinsic, with
/// a size of `count` * `size_of::<T>()` and an alignment of
/// `min_align_of::<T>()`
///
/// The volatile parameter is set to `true`, so it will not be optimized out.
pub fn volatile_copy_nonoverlapping_memory<T>(dst: *mut T, src: *const T,
count: usize);
/// Equivalent to the appropriate `llvm.memmove.p0i8.0i8.*` intrinsic, with
/// a size of `count` * `size_of::<T>()` and an alignment of
/// `min_align_of::<T>()`
///
/// The volatile parameter is set to `true`, so it will not be optimized out.
pub fn volatile_copy_memory<T>(dst: *mut T, src: *const T, count: usize);
/// Equivalent to the appropriate `llvm.memset.p0i8.*` intrinsic, with a
/// size of `count` * `size_of::<T>()` and an alignment of
/// `min_align_of::<T>()`.
///
/// The volatile parameter is set to `true`, so it will not be optimized out.
pub fn volatile_set_memory<T>(dst: *mut T, val: u8, count: usize);
/// Perform a volatile load from the `src` pointer.
pub fn volatile_load<T>(src: *const T) -> T;
/// Perform a volatile store to the `dst` pointer.
pub fn volatile_store<T>(dst: *mut T, val: T);
/// Returns the square root of an `f32`
pub fn sqrtf32(x: f32) -> f32;
/// Returns the square root of an `f64`
pub fn sqrtf64(x: f64) -> f64;
/// Raises an `f32` to an integer power.
pub fn powif32(a: f32, x: i32) -> f32;
/// Raises an `f64` to an integer power.
pub fn powif64(a: f64, x: i32) -> f64;
/// Returns the sine of an `f32`.
pub fn sinf32(x: f32) -> f32;
/// Returns the sine of an `f64`.
pub fn sinf64(x: f64) -> f64;
/// Returns the cosine of an `f32`.
pub fn cosf32(x: f32) -> f32;
/// Returns the cosine of an `f64`.
pub fn cosf64(x: f64) -> f64;
/// Raises an `f32` to an `f32` power.
pub fn powf32(a: f32, x: f32) -> f32;
/// Raises an `f64` to an `f64` power.
pub fn powf64(a: f64, x: f64) -> f64;
/// Returns the exponential of an `f32`.
pub fn expf32(x: f32) -> f32;
/// Returns the exponential of an `f64`.
pub fn expf64(x: f64) -> f64;
/// Returns 2 raised to the power of an `f32`.
pub fn exp2f32(x: f32) -> f32;
/// Returns 2 raised to the power of an `f64`.
pub fn exp2f64(x: f64) -> f64;
/// Returns the natural logarithm of an `f32`.
pub fn logf32(x: f32) -> f32;
/// Returns the natural logarithm of an `f64`.
pub fn logf64(x: f64) -> f64;
/// Returns the base 10 logarithm of an `f32`.
pub fn log10f32(x: f32) -> f32;
/// Returns the base 10 logarithm of an `f64`.
pub fn log10f64(x: f64) -> f64;
/// Returns the base 2 logarithm of an `f32`.
pub fn log2f32(x: f32) -> f32;
/// Returns the base 2 logarithm of an `f64`.
pub fn log2f64(x: f64) -> f64;
/// Returns `a * b + c` for `f32` values.
pub fn fmaf32(a: f32, b: f32, c: f32) -> f32;
/// Returns `a * b + c` for `f64` values.
pub fn fmaf64(a: f64, b: f64, c: f64) -> f64;
/// Returns the absolute value of an `f32`.
pub fn fabsf32(x: f32) -> f32;
/// Returns the absolute value of an `f64`.
pub fn fabsf64(x: f64) -> f64;
/// Copies the sign from `y` to `x` for `f32` values.
pub fn copysignf32(x: f32, y: f32) -> f32;
/// Copies the sign from `y` to `x` for `f64` values.
pub fn copysignf64(x: f64, y: f64) -> f64;
/// Returns the largest integer less than or equal to an `f32`.
pub fn floorf32(x: f32) -> f32;
/// Returns the largest integer less than or equal to an `f64`.
pub fn floorf64(x: f64) -> f64;
/// Returns the smallest integer greater than or equal to an `f32`.
pub fn ceilf32(x: f32) -> f32;
/// Returns the smallest integer greater than or equal to an `f64`.
pub fn ceilf64(x: f64) -> f64;
/// Returns the integer part of an `f32`.
pub fn truncf32(x: f32) -> f32;
/// Returns the integer part of an `f64`.
pub fn truncf64(x: f64) -> f64;
/// Returns the nearest integer to an `f32`. May raise an inexact floating-point exception
/// if the argument is not an integer.
pub fn rintf32(x: f32) -> f32;
/// Returns the nearest integer to an `f64`. May raise an inexact floating-point exception
/// if the argument is not an integer.
pub fn rintf64(x: f64) -> f64;
/// Returns the nearest integer to an `f32`.
pub fn nearbyintf32(x: f32) -> f32;
/// Returns the nearest integer to an `f64`.
pub fn nearbyintf64(x: f64) -> f64;
/// Returns the nearest integer to an `f32`. Rounds half-way cases away from zero.
pub fn roundf32(x: f32) -> f32;
/// Returns the nearest integer to an `f64`. Rounds half-way cases away from zero.
pub fn roundf64(x: f64) -> f64;
/// Float addition that allows optimizations based on algebraic rules.
/// May assume inputs are finite.
pub fn fadd_fast<T>(a: T, b: T) -> T;
/// Float subtraction that allows optimizations based on algebraic rules.
/// May assume inputs are finite.
pub fn fsub_fast<T>(a: T, b: T) -> T;
/// Float multiplication that allows optimizations based on algebraic rules.
/// May assume inputs are finite.
pub fn fmul_fast<T>(a: T, b: T) -> T;
/// Float division that allows optimizations based on algebraic rules.
/// May assume inputs are finite.
pub fn fdiv_fast<T>(a: T, b: T) -> T;
/// Float remainder that allows optimizations based on algebraic rules.
/// May assume inputs are finite.
pub fn frem_fast<T>(a: T, b: T) -> T;
/// Returns the number of bits set in an integer type `T`
pub fn ctpop<T>(x: T) -> T;
/// Returns the number of leading bits unset in an integer type `T`
pub fn ctlz<T>(x: T) -> T;
/// Returns the number of trailing bits unset in an integer type `T`
pub fn cttz<T>(x: T) -> T;
/// Reverses the bytes in an integer type `T`.
pub fn bswap<T>(x: T) -> T;
/// Performs checked integer addition.
pub fn add_with_overflow<T>(x: T, y: T) -> (T, bool);
/// Performs checked integer subtraction
pub fn sub_with_overflow<T>(x: T, y: T) -> (T, bool);
/// Performs checked integer multiplication
pub fn mul_with_overflow<T>(x: T, y: T) -> (T, bool);
/// Performs an unchecked division, resulting in undefined behavior
/// where y = 0 or x = `T::min_value()` and y = -1
pub fn unchecked_div<T>(x: T, y: T) -> T;
/// Returns the remainder of an unchecked division, resulting in
/// undefined behavior where y = 0 or x = `T::min_value()` and y = -1
pub fn unchecked_rem<T>(x: T, y: T) -> T;
/// Returns (a + b) mod 2^N, where N is the width of T in bits.
pub fn overflowing_add<T>(a: T, b: T) -> T;
/// Returns (a - b) mod 2^N, where N is the width of T in bits.
pub fn overflowing_sub<T>(a: T, b: T) -> T;
/// Returns (a * b) mod 2^N, where N is the width of T in bits.
pub fn overflowing_mul<T>(a: T, b: T) -> T;
/// Returns the value of the discriminant for the variant in 'v',
/// cast to a `u64`; if `T` has no discriminant, returns 0.
pub fn discriminant_value<T>(v: &T) -> u64;
/// Rust's "try catch" construct which invokes the function pointer `f` with
/// the data pointer `data`.
///
/// The third pointer is a target-specific data pointer which is filled in
/// with the specifics of the exception that occurred. For examples on Unix
/// platforms this is a `*mut *mut T` which is filled in by the compiler and
/// on MSVC it's `*mut [usize; 2]`. For more information see the compiler's
/// source as well as std's catch implementation.
pub fn try(f: fn(*mut u8), data: *mut u8, local_ptr: *mut u8) -> i32;
}