├── .gitignore ├── .travis.yml ├── CHANGELOG.md ├── Cargo.toml ├── LICENSE-APACHE ├── LICENSE-MIT ├── README.md ├── bors.toml ├── rustfmt.toml └── src ├── boxed.rs ├── lib.rs └── vec.rs /.gitignore: -------------------------------------------------------------------------------- 1 | /target 2 | **/*.rs.bk 3 | Cargo.lock 4 | -------------------------------------------------------------------------------- /.travis.yml: -------------------------------------------------------------------------------- 1 | language: rust 2 | arch: 3 | - amd64 4 | - ppc64le 5 | rust: 6 | - stable 7 | - nightly 8 | 9 | branches: 10 | except: 11 | - staging.tmp 12 | 13 | before_install: 14 | # Do not run bors builds against the nightly compiler. 15 | # We want to find out about nightly bugs, so they're done in master, but we don't block on them. 16 | - if [[ $TRAVIS_RUST_VERSION == "nightly" && $TRAVIS_BRANCH == "staging" ]]; then exit; fi 17 | 18 | script: 19 | - cargo check 20 | - cargo test --release 21 | # check out memcpy-find and scan the output on a few samples 22 | -------------------------------------------------------------------------------- /CHANGELOG.md: -------------------------------------------------------------------------------- 1 | # Change Log 2 | 3 | ## v0.1.5 (01-06-2020) 4 | - switch license to MIT + Apache 2.0 5 | 6 | ## v0.1.4 (24-06-2019) 7 | - `BoxHelper`: replaced nullable pointer with NonNull 8 | 9 | ## v0.1.3 (31-05-2019) 10 | - fixed zero-sized box allocations 11 | - fixed file permissions in the package 12 | 13 | ## v0.1.2 (19-03-2019) 14 | - fixed box alignment 15 | 16 | ## v0.1.1 (15-03-2019) 17 | - `BoxHelper` extension 18 | 19 | ## v0.1 (15-03-2019) 20 | - `VecHelper` extension 21 | -------------------------------------------------------------------------------- /Cargo.toml: -------------------------------------------------------------------------------- 1 | [package] 2 | name = "copyless" 3 | description = "Ways to eliminate memcpy calls when using the standard library." 4 | version = "0.1.5" 5 | authors = ["Dzmitry Malyshau "] 6 | license = "MIT OR Apache-2.0" 7 | edition = "2018" 8 | homepage = "https://github.com/kvark/copyless" 9 | repository = "https://github.com/kvark/copyless" 10 | keywords = ["containers", "memcpy"] 11 | 12 | [lib] 13 | 14 | [dependencies] 15 | -------------------------------------------------------------------------------- /LICENSE-APACHE: -------------------------------------------------------------------------------- 1 | Apache License 2 | Version 2.0, January 2004 3 | http://www.apache.org/licenses/ 4 | 5 | TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 6 | 7 | 1. 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IN NO EVENT 21 | SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY 22 | CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION 23 | OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR 24 | IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 25 | DEALINGS IN THE SOFTWARE. 26 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | ## copyless 2 | [![Build Status](https://travis-ci.org/kvark/copyless.svg)](https://travis-ci.org/kvark/copyless) 3 | [![Crates.io](https://img.shields.io/crates/v/copyless.svg)](https://crates.io/crates/copyless) 4 | 5 | NOTE: crate is marked as DEPRECATED because of https://github.com/kvark/copyless/issues/22 6 | 7 | Rust abstractions can be zero cost in theory, but often reveal quite a few unnecessary `memcpy` calls in practice. This library provides a number of trait extensions for standard containers that expose API that is more friendly to LLVM optimization passes and doesn't end up with as many copies. 8 | 9 | It aims to accelerate [WebRender](https://github.com/servo/webrender) and [gfx-rs](https://github.com/gfx-rs/gfx). 10 | 11 | ## Background 12 | 13 | The `memcpy` instructions showed in profiles of WebRender running in Gecko. @jrmuizel built a tool called [memcpy-find](https://github.com/jrmuizel/memcpy-find) that analyzes LLVM IR and spews out the call stacks that end up producing `memcpy` instructions. We figured out a way to convince the compiler to eliminate the copies. This library attempts to make these ways available to Rust ecosystem, at least until the compiler gets smart enough ;) 14 | 15 | ## Here is a small example 16 | 17 | ```rust 18 | use copyless::BoxHelper; 19 | 20 | enum Foo { 21 | Small(i8), 22 | Big([f32; 100]), 23 | } 24 | 25 | #[inline(never)] 26 | fn foo() -> Box { 27 | Box::new(Foo::Small(4)) // this has 1 memcopy 28 | //Box::alloc().init(Foo::Small(4)) // this has 0 memcopies 29 | } 30 | 31 | fn main() { 32 | let z = foo(); 33 | println!("{:?}", &*z as *const _); 34 | } 35 | ``` 36 | 37 | Playground [permalink](https://play.rust-lang.org/?version=stable&mode=release&edition=2018&gist=579ab13345b1266752b1fa4400194cc7). 38 | -------------------------------------------------------------------------------- /bors.toml: -------------------------------------------------------------------------------- 1 | status = [ 2 | "continuous-integration/travis-ci/push", 3 | ] 4 | 5 | timeout_sec = 18000 # 5 hours 6 | -------------------------------------------------------------------------------- /rustfmt.toml: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/kvark/copyless/dc36153ddc53c47f721d4415edc0d14fb6b40f36/rustfmt.toml -------------------------------------------------------------------------------- /src/boxed.rs: -------------------------------------------------------------------------------- 1 | use { 2 | alloc::{ 3 | alloc::{alloc, dealloc, handle_alloc_error, Layout}, 4 | boxed::Box, 5 | }, 6 | core::{ 7 | mem, 8 | ptr::{self, NonNull}, 9 | }, 10 | }; 11 | 12 | /// A typesafe helper that stores the allocated pointer without the data initialized. 13 | pub struct BoxAllocation( 14 | // ptr cannot be null since it would mean the allocation failed. 15 | // Note: covariance is acceptable since this eventually becomes a `Box`, 16 | // which is covariant too. 17 | NonNull, 18 | ); 19 | 20 | impl BoxAllocation { 21 | /// Consumes self and writes the given value into the allocation. 22 | #[inline(always)] // if this does not get inlined then copying happens 23 | pub fn init(self, value: T) -> Box { 24 | if mem::size_of::() == 0 { 25 | return Box::new(value); 26 | } 27 | 28 | unsafe { 29 | let ptr = self.0.as_ptr(); 30 | mem::forget(self); 31 | ptr::write(ptr, value); 32 | Box::from_raw(ptr) 33 | } 34 | } 35 | } 36 | 37 | impl Drop for BoxAllocation { 38 | fn drop(&mut self) { 39 | if mem::size_of::() == 0 { 40 | return; 41 | } 42 | 43 | let layout = Layout::new::(); 44 | unsafe { 45 | dealloc(self.0.as_ptr() as *mut u8, layout); 46 | } 47 | } 48 | } 49 | 50 | /// Helper trait for a `Box` type that allocates up-front. 51 | pub trait BoxHelper { 52 | /// Allocates the storage without providing any data. 53 | fn alloc() -> BoxAllocation; 54 | } 55 | 56 | impl BoxHelper for Box { 57 | fn alloc() -> BoxAllocation { 58 | if mem::size_of::() == 0 { 59 | return BoxAllocation(NonNull::dangling()); 60 | } 61 | 62 | let layout = Layout::new::(); 63 | BoxAllocation( 64 | NonNull::new(unsafe { alloc(layout) as *mut T }) 65 | .unwrap_or_else(|| handle_alloc_error(layout)), // oom 66 | ) 67 | } 68 | } 69 | 70 | //TODO: is it possible to construct a test case similar to one in `vec` module? 71 | -------------------------------------------------------------------------------- /src/lib.rs: -------------------------------------------------------------------------------- 1 | #![warn(missing_docs)] 2 | #![no_std] 3 | 4 | //! Helper extensions of standard containers that allow memcopy-less operation. 5 | 6 | extern crate alloc; 7 | 8 | pub use self::{ 9 | boxed::{BoxAllocation, BoxHelper}, 10 | vec::{VecAllocation, VecEntry, VecHelper}, 11 | }; 12 | 13 | mod boxed; 14 | mod vec; 15 | -------------------------------------------------------------------------------- /src/vec.rs: -------------------------------------------------------------------------------- 1 | 2 | use {alloc::vec::Vec, core::ptr}; 3 | 4 | /// A typesafe helper that separates new value construction from 5 | /// vector growing, allowing LLVM to ideally construct the element in place. 6 | pub struct VecAllocation<'a, T: 'a> { 7 | vec: &'a mut Vec, 8 | index: usize, 9 | } 10 | 11 | impl<'a, T> VecAllocation<'a, T> { 12 | /// Consumes self and writes the given value into the allocation. 13 | // writing is safe because alloc() ensured enough capacity 14 | // and `Allocation` holds a mutable borrow to prevent anyone else 15 | // from breaking this invariant. 16 | #[inline(always)] 17 | pub fn init(self, value: T) -> usize { 18 | unsafe { 19 | ptr::write(self.vec.as_mut_ptr().add(self.index), value); 20 | self.vec.set_len(self.index + 1); 21 | } 22 | self.index 23 | } 24 | } 25 | 26 | pub struct VecArrayAllocation<'a, T: 'a, const N: usize > { 27 | vec: &'a mut Vec, 28 | index: usize, 29 | } 30 | 31 | impl<'a, T, const N: usize> VecArrayAllocation<'a, T, N> { 32 | /// Consumes self and writes the given value into the allocation. 33 | // writing is safe because alloc() ensured enough capacity 34 | // and `Allocation` holds a mutable borrow to prevent anyone else 35 | // from breaking this invariant. 36 | #[inline(always)] 37 | pub fn init(self, value: [T; N]) -> usize { 38 | unsafe { 39 | ptr::write(self.vec.as_mut_ptr().add(self.index) as *mut [T; N], value); 40 | self.vec.set_len(self.index + N); 41 | } 42 | self.index 43 | } 44 | } 45 | 46 | /// An entry into a vector, similar to `std::collections::hash_map::Entry`. 47 | pub enum VecEntry<'a, T: 'a> { 48 | /// Entry has just been freshly allocated. 49 | Vacant(VecAllocation<'a, T>), 50 | /// Existing entry. 51 | Occupied(&'a mut T), 52 | } 53 | 54 | impl<'a, T> VecEntry<'a, T> { 55 | /// Sets the value for this entry. 56 | #[inline(always)] 57 | pub fn set(self, value: T) { 58 | match self { 59 | VecEntry::Vacant(alloc) => { 60 | alloc.init(value); 61 | } 62 | VecEntry::Occupied(slot) => { 63 | *slot = value; 64 | } 65 | } 66 | } 67 | } 68 | 69 | /// Helper trait for a `Vec` type that allocates up-front. 70 | pub trait VecHelper { 71 | /// Grows the vector by a single entry, returning the allocation. 72 | fn alloc(&mut self) -> VecAllocation; 73 | /// Either returns an existing element, or grows the vector by one. 74 | /// Doesn't expect indices to be higher than the current length. 75 | fn entry(&mut self, index: usize) -> VecEntry; 76 | 77 | fn alloc_multiple(&mut self) -> VecArrayAllocation; 78 | } 79 | 80 | impl VecHelper for Vec { 81 | fn alloc(&mut self) -> VecAllocation { 82 | let index = self.len(); 83 | if self.capacity() == index { 84 | self.reserve(1); 85 | } 86 | VecAllocation { vec: self, index } 87 | } 88 | 89 | fn alloc_multiple(&mut self) -> VecArrayAllocation { 90 | self.reserve(N); 91 | let index = self.len(); 92 | VecArrayAllocation { vec: self, index } 93 | } 94 | 95 | fn entry(&mut self, index: usize) -> VecEntry { 96 | if index < self.len() { 97 | VecEntry::Occupied(unsafe { self.get_unchecked_mut(index) }) 98 | } else { 99 | assert_eq!(index, self.len()); 100 | VecEntry::Vacant(self.alloc()) 101 | } 102 | } 103 | } 104 | 105 | /// Tests are only meaningful in Release 106 | #[cfg(not(debug_assertions))] 107 | #[test] 108 | fn test_zero_copy() { 109 | union Foo { 110 | small: u8, 111 | big: [f32; 10], 112 | } 113 | let mut vec = vec![Foo { big: [1.0; 10] }]; 114 | 115 | // check that the new helper is not overwriting 116 | vec.remove(0); 117 | vec.alloc().init(Foo { small: 5 }); 118 | assert_eq!(unsafe { vec[0].big[1] }, 1.0); 119 | 120 | // check that the regular push is overwriting 121 | vec.remove(0); 122 | vec.push(Foo { small: 5 }); 123 | //TODO: make the expected value to be concrete 124 | assert_ne!(unsafe { vec[0].big[1] }, 1.0); 125 | } 126 | 127 | #[test] 128 | fn test_add_multiple() { 129 | use alloc::vec; 130 | let mut vec = vec![1, 2, 3]; 131 | 132 | // check that the new helper is not overwriting 133 | vec.remove(0); 134 | vec.alloc_multiple().init([4, 5]); 135 | assert_eq!(vec, [2, 3, 4, 5]) 136 | 137 | } 138 | --------------------------------------------------------------------------------