// 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 or the MIT license // , 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)] 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(dst: *mut T, old: T, src: T) -> (T, bool); pub fn atomic_cxchg_acq(dst: *mut T, old: T, src: T) -> (T, bool); pub fn atomic_cxchg_rel(dst: *mut T, old: T, src: T) -> (T, bool); pub fn atomic_cxchg_acqrel(dst: *mut T, old: T, src: T) -> (T, bool); pub fn atomic_cxchg_relaxed(dst: *mut T, old: T, src: T) -> (T, bool); pub fn atomic_cxchg_failrelaxed(dst: *mut T, old: T, src: T) -> (T, bool); pub fn atomic_cxchg_failacq(dst: *mut T, old: T, src: T) -> (T, bool); pub fn atomic_cxchg_acq_failrelaxed(dst: *mut T, old: T, src: T) -> (T, bool); pub fn atomic_cxchg_acqrel_failrelaxed(dst: *mut T, old: T, src: T) -> (T, bool); pub fn atomic_cxchgweak(dst: *mut T, old: T, src: T) -> (T, bool); pub fn atomic_cxchgweak_acq(dst: *mut T, old: T, src: T) -> (T, bool); pub fn atomic_cxchgweak_rel(dst: *mut T, old: T, src: T) -> (T, bool); pub fn atomic_cxchgweak_acqrel(dst: *mut T, old: T, src: T) -> (T, bool); pub fn atomic_cxchgweak_relaxed(dst: *mut T, old: T, src: T) -> (T, bool); pub fn atomic_cxchgweak_failrelaxed(dst: *mut T, old: T, src: T) -> (T, bool); pub fn atomic_cxchgweak_failacq(dst: *mut T, old: T, src: T) -> (T, bool); pub fn atomic_cxchgweak_acq_failrelaxed(dst: *mut T, old: T, src: T) -> (T, bool); pub fn atomic_cxchgweak_acqrel_failrelaxed(dst: *mut T, old: T, src: T) -> (T, bool); pub fn atomic_load(src: *const T) -> T; pub fn atomic_load_acq(src: *const T) -> T; pub fn atomic_load_relaxed(src: *const T) -> T; pub fn atomic_load_unordered(src: *const T) -> T; pub fn atomic_store(dst: *mut T, val: T); pub fn atomic_store_rel(dst: *mut T, val: T); pub fn atomic_store_relaxed(dst: *mut T, val: T); pub fn atomic_store_unordered(dst: *mut T, val: T); pub fn atomic_xchg(dst: *mut T, src: T) -> T; pub fn atomic_xchg_acq(dst: *mut T, src: T) -> T; pub fn atomic_xchg_rel(dst: *mut T, src: T) -> T; pub fn atomic_xchg_acqrel(dst: *mut T, src: T) -> T; pub fn atomic_xchg_relaxed(dst: *mut T, src: T) -> T; pub fn atomic_xadd(dst: *mut T, src: T) -> T; pub fn atomic_xadd_acq(dst: *mut T, src: T) -> T; pub fn atomic_xadd_rel(dst: *mut T, src: T) -> T; pub fn atomic_xadd_acqrel(dst: *mut T, src: T) -> T; pub fn atomic_xadd_relaxed(dst: *mut T, src: T) -> T; pub fn atomic_xsub(dst: *mut T, src: T) -> T; pub fn atomic_xsub_acq(dst: *mut T, src: T) -> T; pub fn atomic_xsub_rel(dst: *mut T, src: T) -> T; pub fn atomic_xsub_acqrel(dst: *mut T, src: T) -> T; pub fn atomic_xsub_relaxed(dst: *mut T, src: T) -> T; pub fn atomic_and(dst: *mut T, src: T) -> T; pub fn atomic_and_acq(dst: *mut T, src: T) -> T; pub fn atomic_and_rel(dst: *mut T, src: T) -> T; pub fn atomic_and_acqrel(dst: *mut T, src: T) -> T; pub fn atomic_and_relaxed(dst: *mut T, src: T) -> T; pub fn atomic_nand(dst: *mut T, src: T) -> T; pub fn atomic_nand_acq(dst: *mut T, src: T) -> T; pub fn atomic_nand_rel(dst: *mut T, src: T) -> T; pub fn atomic_nand_acqrel(dst: *mut T, src: T) -> T; pub fn atomic_nand_relaxed(dst: *mut T, src: T) -> T; pub fn atomic_or(dst: *mut T, src: T) -> T; pub fn atomic_or_acq(dst: *mut T, src: T) -> T; pub fn atomic_or_rel(dst: *mut T, src: T) -> T; pub fn atomic_or_acqrel(dst: *mut T, src: T) -> T; pub fn atomic_or_relaxed(dst: *mut T, src: T) -> T; pub fn atomic_xor(dst: *mut T, src: T) -> T; pub fn atomic_xor_acq(dst: *mut T, src: T) -> T; pub fn atomic_xor_rel(dst: *mut T, src: T) -> T; pub fn atomic_xor_acqrel(dst: *mut T, src: T) -> T; pub fn atomic_xor_relaxed(dst: *mut T, src: T) -> T; pub fn atomic_max(dst: *mut T, src: T) -> T; pub fn atomic_max_acq(dst: *mut T, src: T) -> T; pub fn atomic_max_rel(dst: *mut T, src: T) -> T; pub fn atomic_max_acqrel(dst: *mut T, src: T) -> T; pub fn atomic_max_relaxed(dst: *mut T, src: T) -> T; pub fn atomic_min(dst: *mut T, src: T) -> T; pub fn atomic_min_acq(dst: *mut T, src: T) -> T; pub fn atomic_min_rel(dst: *mut T, src: T) -> T; pub fn atomic_min_acqrel(dst: *mut T, src: T) -> T; pub fn atomic_min_relaxed(dst: *mut T, src: T) -> T; pub fn atomic_umin(dst: *mut T, src: T) -> T; pub fn atomic_umin_acq(dst: *mut T, src: T) -> T; pub fn atomic_umin_rel(dst: *mut T, src: T) -> T; pub fn atomic_umin_acqrel(dst: *mut T, src: T) -> T; pub fn atomic_umin_relaxed(dst: *mut T, src: T) -> T; pub fn atomic_umax(dst: *mut T, src: T) -> T; pub fn atomic_umax_acq(dst: *mut T, src: T) -> T; pub fn atomic_umax_rel(dst: *mut T, src: T) -> T; pub fn atomic_umax_acqrel(dst: *mut T, src: T) -> T; pub fn atomic_umax_relaxed(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; /// 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() -> usize; /// Moves a value to an uninitialized memory location. /// /// Drop glue is not run on the destination. pub fn move_val_init(dst: *mut T, src: T); pub fn min_align_of() -> usize; pub fn pref_align_of() -> usize; pub fn size_of_val(_: &T) -> usize; pub fn min_align_of_val(_: &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(to_drop: *mut T); /// Gets a static string slice containing the name of a type. pub fn type_name() -> &'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() -> u64; /// 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; /// 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; /// Moves a value out of scope without running drop glue. pub fn forget(_: 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 source value into the /// destination value, 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][ub] with this function. `transmute` should be /// the absolute last resort. /// /// The [nomicon](../../nomicon/transmutes.html) has additional /// documentation. /// /// [ub]: ../../reference.html#behavior-considered-undefined /// /// # 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::(1.0) /// }; /// assert_eq!(bitpattern, 0x3F800000); /// ``` /// /// Turning a pointer into a function pointer. This is *not* portable to /// machines where function pointers and data pointers have different sizes. /// /// ``` /// 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<'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 /// /// Don't despair: many uses of `transmute` can be achieved through other means. /// Below are common applications of `transmute` which can be replaced with safer /// constructs. /// /// 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>`: /// /// ``` /// let store = [0, 1, 2, 3]; /// let mut v_orig = store.iter().collect::>(); /// /// // Using transmute: this is Undefined Behavior, and a bad idea. /// // However, it is no-copy. /// let v_transmuted = unsafe { /// std::mem::transmute::, Vec>>( /// 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::>>(); /// /// // 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(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(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(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(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() -> 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(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(dst: *const T, offset: isize) -> *const T; /// Copies `count * size_of` 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(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(src: *const T, dst: *mut T, count: usize); /// Copies `count * size_of` 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(ptr: *const T, elts: usize) -> Vec { /// 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(src: *const T, dst: *mut T, count: usize); /// Invokes memset on the specified pointer, setting `count * size_of::()` /// bytes of memory starting at `dst` to `val`. #[stable(feature = "rust1", since = "1.0.0")] pub fn write_bytes(dst: *mut T, val: u8, count: usize); /// Equivalent to the appropriate `llvm.memcpy.p0i8.0i8.*` intrinsic, with /// a size of `count` * `size_of::()` and an alignment of /// `min_align_of::()` /// /// The volatile parameter is set to `true`, so it will not be optimized out. pub fn volatile_copy_nonoverlapping_memory(dst: *mut T, src: *const T, count: usize); /// Equivalent to the appropriate `llvm.memmove.p0i8.0i8.*` intrinsic, with /// a size of `count` * `size_of::()` and an alignment of /// `min_align_of::()` /// /// The volatile parameter is set to `true`, so it will not be optimized out. pub fn volatile_copy_memory(dst: *mut T, src: *const T, count: usize); /// Equivalent to the appropriate `llvm.memset.p0i8.*` intrinsic, with a /// size of `count` * `size_of::()` and an alignment of /// `min_align_of::()`. /// /// The volatile parameter is set to `true`, so it will not be optimized out. pub fn volatile_set_memory(dst: *mut T, val: u8, count: usize); /// Perform a volatile load from the `src` pointer. pub fn volatile_load(src: *const T) -> T; /// Perform a volatile store to the `dst` pointer. pub fn volatile_store(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(a: T, b: T) -> T; /// Float subtraction that allows optimizations based on algebraic rules. /// May assume inputs are finite. pub fn fsub_fast(a: T, b: T) -> T; /// Float multiplication that allows optimizations based on algebraic rules. /// May assume inputs are finite. pub fn fmul_fast(a: T, b: T) -> T; /// Float division that allows optimizations based on algebraic rules. /// May assume inputs are finite. pub fn fdiv_fast(a: T, b: T) -> T; /// Float remainder that allows optimizations based on algebraic rules. /// May assume inputs are finite. pub fn frem_fast(a: T, b: T) -> T; /// Returns the number of bits set in an integer type `T` pub fn ctpop(x: T) -> T; /// Returns the number of leading bits unset in an integer type `T` pub fn ctlz(x: T) -> T; /// Returns the number of trailing bits unset in an integer type `T` pub fn cttz(x: T) -> T; /// Reverses the bytes in an integer type `T`. pub fn bswap(x: T) -> T; /// Performs checked integer addition. pub fn add_with_overflow(x: T, y: T) -> (T, bool); /// Performs checked integer subtraction pub fn sub_with_overflow(x: T, y: T) -> (T, bool); /// Performs checked integer multiplication pub fn mul_with_overflow(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(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(x: T, y: T) -> T; /// Returns (a + b) mod 2^N, where N is the width of T in bits. pub fn overflowing_add(a: T, b: T) -> T; /// Returns (a - b) mod 2^N, where N is the width of T in bits. pub fn overflowing_sub(a: T, b: T) -> T; /// Returns (a * b) mod 2^N, where N is the width of T in bits. pub fn overflowing_mul(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(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; }