| //! The arena, a fast but limited type of allocator. |
| //! |
| //! Arenas are a type of allocator that destroy the objects within, all at |
| //! once, once the arena itself is destroyed. They do not support deallocation |
| //! of individual objects while the arena itself is still alive. The benefit |
| //! of an arena is very fast allocation; just a pointer bump. |
| //! |
| //! This crate implements several kinds of arena. |
| |
| // tidy-alphabetical-start |
| #![allow(clippy::mut_from_ref)] // Arena allocators are one place where this pattern is fine. |
| #![allow(internal_features)] |
| #![cfg_attr(test, feature(test))] |
| #![deny(unsafe_op_in_unsafe_fn)] |
| #![doc( |
| html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/", |
| test(no_crate_inject, attr(deny(warnings))) |
| )] |
| #![doc(rust_logo)] |
| #![feature(core_intrinsics)] |
| #![feature(decl_macro)] |
| #![feature(dropck_eyepatch)] |
| #![feature(maybe_uninit_slice)] |
| #![feature(never_type)] |
| #![feature(rustc_attrs)] |
| #![feature(rustdoc_internals)] |
| #![feature(unwrap_infallible)] |
| // tidy-alphabetical-end |
| |
| use std::alloc::Layout; |
| use std::cell::{Cell, RefCell}; |
| use std::marker::PhantomData; |
| use std::mem::{self, MaybeUninit}; |
| use std::ptr::{self, NonNull}; |
| use std::{cmp, intrinsics, slice}; |
| |
| use smallvec::SmallVec; |
| |
| /// This calls the passed function while ensuring it won't be inlined into the caller. |
| #[inline(never)] |
| #[cold] |
| fn outline<F: FnOnce() -> R, R>(f: F) -> R { |
| f() |
| } |
| |
| struct ArenaChunk<T = u8> { |
| /// The raw storage for the arena chunk. |
| storage: NonNull<[MaybeUninit<T>]>, |
| /// The number of valid entries in the chunk. |
| entries: usize, |
| } |
| |
| unsafe impl<#[may_dangle] T> Drop for ArenaChunk<T> { |
| fn drop(&mut self) { |
| unsafe { drop(Box::from_raw(self.storage.as_mut())) } |
| } |
| } |
| |
| impl<T> ArenaChunk<T> { |
| #[inline] |
| unsafe fn new(capacity: usize) -> ArenaChunk<T> { |
| ArenaChunk { |
| storage: NonNull::from(Box::leak(Box::new_uninit_slice(capacity))), |
| entries: 0, |
| } |
| } |
| |
| /// Destroys this arena chunk. |
| /// |
| /// # Safety |
| /// |
| /// The caller must ensure that `len` elements of this chunk have been initialized. |
| #[inline] |
| unsafe fn destroy(&mut self, len: usize) { |
| // The branch on needs_drop() is an -O1 performance optimization. |
| // Without the branch, dropping TypedArena<T> takes linear time. |
| if mem::needs_drop::<T>() { |
| // SAFETY: The caller must ensure that `len` elements of this chunk have |
| // been initialized. |
| unsafe { |
| let slice = self.storage.as_mut(); |
| slice[..len].assume_init_drop(); |
| } |
| } |
| } |
| |
| // Returns a pointer to the first allocated object. |
| #[inline] |
| fn start(&mut self) -> *mut T { |
| self.storage.as_ptr() as *mut T |
| } |
| |
| // Returns a pointer to the end of the allocated space. |
| #[inline] |
| fn end(&mut self) -> *mut T { |
| unsafe { |
| if size_of::<T>() == 0 { |
| // A pointer as large as possible for zero-sized elements. |
| ptr::without_provenance_mut(!0) |
| } else { |
| self.start().add(self.storage.len()) |
| } |
| } |
| } |
| } |
| |
| // The arenas start with PAGE-sized chunks, and then each new chunk is twice as |
| // big as its predecessor, up until we reach HUGE_PAGE-sized chunks, whereupon |
| // we stop growing. This scales well, from arenas that are barely used up to |
| // arenas that are used for 100s of MiBs. Note also that the chosen sizes match |
| // the usual sizes of pages and huge pages on Linux. |
| const PAGE: usize = 4096; |
| const HUGE_PAGE: usize = 2 * 1024 * 1024; |
| |
| /// An arena that can hold objects of only one type. |
| pub struct TypedArena<T> { |
| /// A pointer to the next object to be allocated. |
| ptr: Cell<*mut T>, |
| |
| /// A pointer to the end of the allocated area. When this pointer is |
| /// reached, a new chunk is allocated. |
| end: Cell<*mut T>, |
| |
| /// A vector of arena chunks. |
| chunks: RefCell<Vec<ArenaChunk<T>>>, |
| |
| /// Marker indicating that dropping the arena causes its owned |
| /// instances of `T` to be dropped. |
| _own: PhantomData<T>, |
| } |
| |
| impl<T> Default for TypedArena<T> { |
| /// Creates a new `TypedArena`. |
| fn default() -> TypedArena<T> { |
| TypedArena { |
| // We set both `ptr` and `end` to 0 so that the first call to |
| // alloc() will trigger a grow(). |
| ptr: Cell::new(ptr::null_mut()), |
| end: Cell::new(ptr::null_mut()), |
| chunks: Default::default(), |
| _own: PhantomData, |
| } |
| } |
| } |
| |
| impl<T> TypedArena<T> { |
| /// Allocates an object in the `TypedArena`, returning a reference to it. |
| #[inline] |
| pub fn alloc(&self, object: T) -> &mut T { |
| if self.ptr == self.end { |
| self.grow(1) |
| } |
| |
| unsafe { |
| if size_of::<T>() == 0 { |
| self.ptr.set(self.ptr.get().wrapping_byte_add(1)); |
| let ptr = ptr::NonNull::<T>::dangling().as_ptr(); |
| // Don't drop the object. This `write` is equivalent to `forget`. |
| ptr::write(ptr, object); |
| &mut *ptr |
| } else { |
| let ptr = self.ptr.get(); |
| // Advance the pointer. |
| self.ptr.set(self.ptr.get().add(1)); |
| // Write into uninitialized memory. |
| ptr::write(ptr, object); |
| &mut *ptr |
| } |
| } |
| } |
| |
| #[inline] |
| fn can_allocate(&self, additional: usize) -> bool { |
| // FIXME: this should *likely* use `offset_from`, but more |
| // investigation is needed (including running tests in miri). |
| let available_bytes = self.end.get().addr() - self.ptr.get().addr(); |
| let additional_bytes = additional.checked_mul(size_of::<T>()).unwrap(); |
| available_bytes >= additional_bytes |
| } |
| |
| #[inline] |
| fn alloc_raw_slice(&self, len: usize) -> *mut T { |
| assert!(size_of::<T>() != 0); |
| assert!(len != 0); |
| |
| // Ensure the current chunk can fit `len` objects. |
| if !self.can_allocate(len) { |
| self.grow(len); |
| debug_assert!(self.can_allocate(len)); |
| } |
| |
| let start_ptr = self.ptr.get(); |
| // SAFETY: `can_allocate`/`grow` ensures that there is enough space for |
| // `len` elements. |
| unsafe { self.ptr.set(start_ptr.add(len)) }; |
| start_ptr |
| } |
| |
| /// Allocates the elements of this iterator into a contiguous slice in the `TypedArena`. |
| /// |
| /// Note: for reasons of reentrancy and panic safety we collect into a `SmallVec<[_; 8]>` before |
| /// storing the elements in the arena. |
| #[inline] |
| pub fn alloc_from_iter<I: IntoIterator<Item = T>>(&self, iter: I) -> &mut [T] { |
| self.try_alloc_from_iter(iter.into_iter().map(Ok::<T, !>)).into_ok() |
| } |
| |
| /// Allocates the elements of this iterator into a contiguous slice in the `TypedArena`. |
| /// |
| /// Note: for reasons of reentrancy and panic safety we collect into a `SmallVec<[_; 8]>` before |
| /// storing the elements in the arena. |
| #[inline] |
| pub fn try_alloc_from_iter<E>( |
| &self, |
| iter: impl IntoIterator<Item = Result<T, E>>, |
| ) -> Result<&mut [T], E> { |
| // Despite the similarlty with `DroplessArena`, we cannot reuse their fast case. The reason |
| // is subtle: these arenas are reentrant. In other words, `iter` may very well be holding a |
| // reference to `self` and adding elements to the arena during iteration. |
| // |
| // For this reason, if we pre-allocated any space for the elements of this iterator, we'd |
| // have to track that some uninitialized elements are followed by some initialized elements, |
| // else we might accidentally drop uninitialized memory if something panics or if the |
| // iterator doesn't fill all the length we expected. |
| // |
| // So we collect all the elements beforehand, which takes care of reentrancy and panic |
| // safety. This function is much less hot than `DroplessArena::alloc_from_iter`, so it |
| // doesn't need to be hyper-optimized. |
| assert!(size_of::<T>() != 0); |
| |
| let vec: Result<SmallVec<[T; 8]>, E> = iter.into_iter().collect(); |
| let mut vec = vec?; |
| if vec.is_empty() { |
| return Ok(&mut []); |
| } |
| // Move the content to the arena by copying and then forgetting it. |
| let len = vec.len(); |
| let start_ptr = self.alloc_raw_slice(len); |
| Ok(unsafe { |
| vec.as_ptr().copy_to_nonoverlapping(start_ptr, len); |
| vec.set_len(0); |
| slice::from_raw_parts_mut(start_ptr, len) |
| }) |
| } |
| |
| /// Grows the arena. |
| #[inline(never)] |
| #[cold] |
| fn grow(&self, additional: usize) { |
| unsafe { |
| // We need the element size to convert chunk sizes (ranging from |
| // PAGE to HUGE_PAGE bytes) to element counts. |
| let elem_size = cmp::max(1, size_of::<T>()); |
| let mut chunks = self.chunks.borrow_mut(); |
| let mut new_cap; |
| if let Some(last_chunk) = chunks.last_mut() { |
| // If a type is `!needs_drop`, we don't need to keep track of how many elements |
| // the chunk stores - the field will be ignored anyway. |
| if mem::needs_drop::<T>() { |
| // FIXME: this should *likely* use `offset_from`, but more |
| // investigation is needed (including running tests in miri). |
| let used_bytes = self.ptr.get().addr() - last_chunk.start().addr(); |
| last_chunk.entries = used_bytes / size_of::<T>(); |
| } |
| |
| // If the previous chunk's len is less than HUGE_PAGE |
| // bytes, then this chunk will be least double the previous |
| // chunk's size. |
| new_cap = last_chunk.storage.len().min(HUGE_PAGE / elem_size / 2); |
| new_cap *= 2; |
| } else { |
| new_cap = PAGE / elem_size; |
| } |
| // Also ensure that this chunk can fit `additional`. |
| new_cap = cmp::max(additional, new_cap); |
| |
| let mut chunk = ArenaChunk::<T>::new(new_cap); |
| self.ptr.set(chunk.start()); |
| self.end.set(chunk.end()); |
| chunks.push(chunk); |
| } |
| } |
| |
| // Drops the contents of the last chunk. The last chunk is partially empty, unlike all other |
| // chunks. |
| fn clear_last_chunk(&self, last_chunk: &mut ArenaChunk<T>) { |
| // Determine how much was filled. |
| let start = last_chunk.start().addr(); |
| // We obtain the value of the pointer to the first uninitialized element. |
| let end = self.ptr.get().addr(); |
| // We then calculate the number of elements to be dropped in the last chunk, |
| // which is the filled area's length. |
| let diff = if size_of::<T>() == 0 { |
| // `T` is ZST. It can't have a drop flag, so the value here doesn't matter. We get |
| // the number of zero-sized values in the last and only chunk, just out of caution. |
| // Recall that `end` was incremented for each allocated value. |
| end - start |
| } else { |
| // FIXME: this should *likely* use `offset_from`, but more |
| // investigation is needed (including running tests in miri). |
| (end - start) / size_of::<T>() |
| }; |
| // Pass that to the `destroy` method. |
| unsafe { |
| last_chunk.destroy(diff); |
| } |
| // Reset the chunk. |
| self.ptr.set(last_chunk.start()); |
| } |
| } |
| |
| unsafe impl<#[may_dangle] T> Drop for TypedArena<T> { |
| fn drop(&mut self) { |
| unsafe { |
| // Determine how much was filled. |
| let mut chunks_borrow = self.chunks.borrow_mut(); |
| if let Some(mut last_chunk) = chunks_borrow.pop() { |
| // Drop the contents of the last chunk. |
| self.clear_last_chunk(&mut last_chunk); |
| // The last chunk will be dropped. Destroy all other chunks. |
| for chunk in chunks_borrow.iter_mut() { |
| chunk.destroy(chunk.entries); |
| } |
| } |
| // Box handles deallocation of `last_chunk` and `self.chunks`. |
| } |
| } |
| } |
| |
| unsafe impl<T: Send> Send for TypedArena<T> {} |
| |
| #[inline(always)] |
| fn align_down(val: usize, align: usize) -> usize { |
| debug_assert!(align.is_power_of_two()); |
| val & !(align - 1) |
| } |
| |
| #[inline(always)] |
| fn align_up(val: usize, align: usize) -> usize { |
| debug_assert!(align.is_power_of_two()); |
| (val + align - 1) & !(align - 1) |
| } |
| |
| // Pointer alignment is common in compiler types, so keep `DroplessArena` aligned to them |
| // to optimize away alignment code. |
| const DROPLESS_ALIGNMENT: usize = align_of::<usize>(); |
| |
| /// An arena that can hold objects of multiple different types that impl `Copy` |
| /// and/or satisfy `!mem::needs_drop`. |
| pub struct DroplessArena { |
| /// A pointer to the start of the free space. |
| start: Cell<*mut u8>, |
| |
| /// A pointer to the end of free space. |
| /// |
| /// The allocation proceeds downwards from the end of the chunk towards the |
| /// start. (This is slightly simpler and faster than allocating upwards, |
| /// see <https://fitzgeraldnick.com/2019/11/01/always-bump-downwards.html>.) |
| /// When this pointer crosses the start pointer, a new chunk is allocated. |
| /// |
| /// This is kept aligned to DROPLESS_ALIGNMENT. |
| end: Cell<*mut u8>, |
| |
| /// A vector of arena chunks. |
| chunks: RefCell<Vec<ArenaChunk>>, |
| } |
| |
| unsafe impl Send for DroplessArena {} |
| |
| impl Default for DroplessArena { |
| #[inline] |
| fn default() -> DroplessArena { |
| DroplessArena { |
| // We set both `start` and `end` to 0 so that the first call to |
| // alloc() will trigger a grow(). |
| start: Cell::new(ptr::null_mut()), |
| end: Cell::new(ptr::null_mut()), |
| chunks: Default::default(), |
| } |
| } |
| } |
| |
| impl DroplessArena { |
| #[inline(never)] |
| #[cold] |
| fn grow(&self, layout: Layout) { |
| // Add some padding so we can align `self.end` while |
| // still fitting in a `layout` allocation. |
| let additional = layout.size() + cmp::max(DROPLESS_ALIGNMENT, layout.align()) - 1; |
| |
| unsafe { |
| let mut chunks = self.chunks.borrow_mut(); |
| let mut new_cap; |
| if let Some(last_chunk) = chunks.last_mut() { |
| // There is no need to update `last_chunk.entries` because that |
| // field isn't used by `DroplessArena`. |
| |
| // If the previous chunk's len is less than HUGE_PAGE |
| // bytes, then this chunk will be least double the previous |
| // chunk's size. |
| new_cap = last_chunk.storage.len().min(HUGE_PAGE / 2); |
| new_cap *= 2; |
| } else { |
| new_cap = PAGE; |
| } |
| // Also ensure that this chunk can fit `additional`. |
| new_cap = cmp::max(additional, new_cap); |
| |
| let mut chunk = ArenaChunk::new(align_up(new_cap, PAGE)); |
| self.start.set(chunk.start()); |
| |
| // Align the end to DROPLESS_ALIGNMENT. |
| let end = align_down(chunk.end().addr(), DROPLESS_ALIGNMENT); |
| |
| // Make sure we don't go past `start`. This should not happen since the allocation |
| // should be at least DROPLESS_ALIGNMENT - 1 bytes. |
| debug_assert!(chunk.start().addr() <= end); |
| |
| self.end.set(chunk.end().with_addr(end)); |
| |
| chunks.push(chunk); |
| } |
| } |
| |
| #[inline] |
| pub fn alloc_raw(&self, layout: Layout) -> *mut u8 { |
| assert!(layout.size() != 0); |
| |
| // This loop executes once or twice: if allocation fails the first |
| // time, the `grow` ensures it will succeed the second time. |
| loop { |
| let start = self.start.get().addr(); |
| let old_end = self.end.get(); |
| let end = old_end.addr(); |
| |
| // Align allocated bytes so that `self.end` stays aligned to |
| // DROPLESS_ALIGNMENT. |
| let bytes = align_up(layout.size(), DROPLESS_ALIGNMENT); |
| |
| // Tell LLVM that `end` is aligned to DROPLESS_ALIGNMENT. |
| unsafe { intrinsics::assume(end == align_down(end, DROPLESS_ALIGNMENT)) }; |
| |
| if let Some(sub) = end.checked_sub(bytes) { |
| let new_end = align_down(sub, layout.align()); |
| if start <= new_end { |
| let new_end = old_end.with_addr(new_end); |
| // `new_end` is aligned to DROPLESS_ALIGNMENT as `align_down` |
| // preserves alignment as both `end` and `bytes` are already |
| // aligned to DROPLESS_ALIGNMENT. |
| self.end.set(new_end); |
| return new_end; |
| } |
| } |
| |
| // No free space left. Allocate a new chunk to satisfy the request. |
| // On failure the grow will panic or abort. |
| self.grow(layout); |
| } |
| } |
| |
| #[inline] |
| pub fn alloc<T>(&self, object: T) -> &mut T { |
| assert!(!mem::needs_drop::<T>()); |
| assert!(size_of::<T>() != 0); |
| |
| let mem = self.alloc_raw(Layout::new::<T>()) as *mut T; |
| |
| unsafe { |
| // Write into uninitialized memory. |
| ptr::write(mem, object); |
| &mut *mem |
| } |
| } |
| |
| /// Allocates a slice of objects that are copied into the `DroplessArena`, returning a mutable |
| /// reference to it. Will panic if passed a zero-sized type. |
| /// |
| /// Panics: |
| /// |
| /// - Zero-sized types |
| /// - Zero-length slices |
| #[inline] |
| pub fn alloc_slice<T>(&self, slice: &[T]) -> &mut [T] |
| where |
| T: Copy, |
| { |
| assert!(!mem::needs_drop::<T>()); |
| assert!(size_of::<T>() != 0); |
| assert!(!slice.is_empty()); |
| |
| let mem = self.alloc_raw(Layout::for_value::<[T]>(slice)) as *mut T; |
| |
| unsafe { |
| mem.copy_from_nonoverlapping(slice.as_ptr(), slice.len()); |
| slice::from_raw_parts_mut(mem, slice.len()) |
| } |
| } |
| |
| /// Used by `Lift` to check whether this slice is allocated |
| /// in this arena. |
| #[inline] |
| pub fn contains_slice<T>(&self, slice: &[T]) -> bool { |
| for chunk in self.chunks.borrow_mut().iter_mut() { |
| let ptr = slice.as_ptr().cast::<u8>().cast_mut(); |
| if chunk.start() <= ptr && chunk.end() >= ptr { |
| return true; |
| } |
| } |
| false |
| } |
| |
| /// Allocates a string slice that is copied into the `DroplessArena`, returning a |
| /// reference to it. Will panic if passed an empty string. |
| /// |
| /// Panics: |
| /// |
| /// - Zero-length string |
| #[inline] |
| pub fn alloc_str(&self, string: &str) -> &str { |
| let slice = self.alloc_slice(string.as_bytes()); |
| |
| // SAFETY: the result has a copy of the same valid UTF-8 bytes. |
| unsafe { std::str::from_utf8_unchecked(slice) } |
| } |
| |
| /// # Safety |
| /// |
| /// The caller must ensure that `mem` is valid for writes up to `size_of::<T>() * len`, and that |
| /// that memory stays allocated and not shared for the lifetime of `self`. This must hold even |
| /// if `iter.next()` allocates onto `self`. |
| #[inline] |
| unsafe fn write_from_iter<T, I: Iterator<Item = T>>( |
| &self, |
| mut iter: I, |
| len: usize, |
| mem: *mut T, |
| ) -> &mut [T] { |
| let mut i = 0; |
| // Use a manual loop since LLVM manages to optimize it better for |
| // slice iterators |
| loop { |
| // SAFETY: The caller must ensure that `mem` is valid for writes up to |
| // `size_of::<T>() * len`. |
| unsafe { |
| match iter.next() { |
| Some(value) if i < len => mem.add(i).write(value), |
| Some(_) | None => { |
| // We only return as many items as the iterator gave us, even |
| // though it was supposed to give us `len` |
| return slice::from_raw_parts_mut(mem, i); |
| } |
| } |
| } |
| i += 1; |
| } |
| } |
| |
| #[inline] |
| pub fn alloc_from_iter<T, I: IntoIterator<Item = T>>(&self, iter: I) -> &mut [T] { |
| // Warning: this function is reentrant: `iter` could hold a reference to `&self` and |
| // allocate additional elements while we're iterating. |
| let iter = iter.into_iter(); |
| assert!(size_of::<T>() != 0); |
| assert!(!mem::needs_drop::<T>()); |
| |
| let size_hint = iter.size_hint(); |
| |
| match size_hint { |
| (min, Some(max)) if min == max => { |
| // We know the exact number of elements the iterator expects to produce here. |
| let len = min; |
| |
| if len == 0 { |
| return &mut []; |
| } |
| |
| let mem = self.alloc_raw(Layout::array::<T>(len).unwrap()) as *mut T; |
| // SAFETY: `write_from_iter` doesn't touch `self`. It only touches the slice we just |
| // reserved. If the iterator panics or doesn't output `len` elements, this will |
| // leave some unallocated slots in the arena, which is fine because we do not call |
| // `drop`. |
| unsafe { self.write_from_iter(iter, len, mem) } |
| } |
| (_, _) => outline(move || self.try_alloc_from_iter(iter.map(Ok::<T, !>)).into_ok()), |
| } |
| } |
| |
| #[inline] |
| pub fn try_alloc_from_iter<T, E>( |
| &self, |
| iter: impl IntoIterator<Item = Result<T, E>>, |
| ) -> Result<&mut [T], E> { |
| // Despite the similarlty with `alloc_from_iter`, we cannot reuse their fast case, as we |
| // cannot know the minimum length of the iterator in this case. |
| assert!(size_of::<T>() != 0); |
| |
| // Takes care of reentrancy. |
| let vec: Result<SmallVec<[T; 8]>, E> = iter.into_iter().collect(); |
| let mut vec = vec?; |
| if vec.is_empty() { |
| return Ok(&mut []); |
| } |
| // Move the content to the arena by copying and then forgetting it. |
| let len = vec.len(); |
| Ok(unsafe { |
| let start_ptr = self.alloc_raw(Layout::for_value::<[T]>(vec.as_slice())) as *mut T; |
| vec.as_ptr().copy_to_nonoverlapping(start_ptr, len); |
| vec.set_len(0); |
| slice::from_raw_parts_mut(start_ptr, len) |
| }) |
| } |
| } |
| |
| /// Declare an `Arena` containing one dropless arena and many typed arenas (the |
| /// types of the typed arenas are specified by the arguments). |
| /// |
| /// There are three cases of interest. |
| /// - Types that are `Copy`: these need not be specified in the arguments. They |
| /// will use the `DroplessArena`. |
| /// - Types that are `!Copy` and `!Drop`: these must be specified in the |
| /// arguments. An empty `TypedArena` will be created for each one, but the |
| /// `DroplessArena` will always be used and the `TypedArena` will stay empty. |
| /// This is odd but harmless, because an empty arena allocates no memory. |
| /// - Types that are `!Copy` and `Drop`: these must be specified in the |
| /// arguments. The `TypedArena` will be used for them. |
| /// |
| #[rustc_macro_transparency = "semitransparent"] |
| pub macro declare_arena([$($a:tt $name:ident: $ty:ty,)*]) { |
| #[derive(Default)] |
| pub struct Arena<'tcx> { |
| pub dropless: $crate::DroplessArena, |
| $($name: $crate::TypedArena<$ty>,)* |
| } |
| |
| pub trait ArenaAllocatable<'tcx, C = rustc_arena::IsNotCopy>: Sized { |
| #[allow(clippy::mut_from_ref)] |
| fn allocate_on(self, arena: &'tcx Arena<'tcx>) -> &'tcx mut Self; |
| #[allow(clippy::mut_from_ref)] |
| fn allocate_from_iter( |
| arena: &'tcx Arena<'tcx>, |
| iter: impl ::std::iter::IntoIterator<Item = Self>, |
| ) -> &'tcx mut [Self]; |
| } |
| |
| // Any type that impls `Copy` can be arena-allocated in the `DroplessArena`. |
| impl<'tcx, T: Copy> ArenaAllocatable<'tcx, rustc_arena::IsCopy> for T { |
| #[inline] |
| #[allow(clippy::mut_from_ref)] |
| fn allocate_on(self, arena: &'tcx Arena<'tcx>) -> &'tcx mut Self { |
| arena.dropless.alloc(self) |
| } |
| #[inline] |
| #[allow(clippy::mut_from_ref)] |
| fn allocate_from_iter( |
| arena: &'tcx Arena<'tcx>, |
| iter: impl ::std::iter::IntoIterator<Item = Self>, |
| ) -> &'tcx mut [Self] { |
| arena.dropless.alloc_from_iter(iter) |
| } |
| } |
| $( |
| impl<'tcx> ArenaAllocatable<'tcx, rustc_arena::IsNotCopy> for $ty { |
| #[inline] |
| fn allocate_on(self, arena: &'tcx Arena<'tcx>) -> &'tcx mut Self { |
| if !::std::mem::needs_drop::<Self>() { |
| arena.dropless.alloc(self) |
| } else { |
| arena.$name.alloc(self) |
| } |
| } |
| |
| #[inline] |
| #[allow(clippy::mut_from_ref)] |
| fn allocate_from_iter( |
| arena: &'tcx Arena<'tcx>, |
| iter: impl ::std::iter::IntoIterator<Item = Self>, |
| ) -> &'tcx mut [Self] { |
| if !::std::mem::needs_drop::<Self>() { |
| arena.dropless.alloc_from_iter(iter) |
| } else { |
| arena.$name.alloc_from_iter(iter) |
| } |
| } |
| } |
| )* |
| |
| impl<'tcx> Arena<'tcx> { |
| #[inline] |
| #[allow(clippy::mut_from_ref)] |
| pub fn alloc<T: ArenaAllocatable<'tcx, C>, C>(&'tcx self, value: T) -> &mut T { |
| value.allocate_on(self) |
| } |
| |
| // Any type that impls `Copy` can have slices be arena-allocated in the `DroplessArena`. |
| #[inline] |
| #[allow(clippy::mut_from_ref)] |
| pub fn alloc_slice<T: ::std::marker::Copy>(&self, value: &[T]) -> &mut [T] { |
| if value.is_empty() { |
| return &mut []; |
| } |
| self.dropless.alloc_slice(value) |
| } |
| |
| #[inline] |
| pub fn alloc_str(&self, string: &str) -> &str { |
| if string.is_empty() { |
| return ""; |
| } |
| self.dropless.alloc_str(string) |
| } |
| |
| #[allow(clippy::mut_from_ref)] |
| pub fn alloc_from_iter<T: ArenaAllocatable<'tcx, C>, C>( |
| &'tcx self, |
| iter: impl ::std::iter::IntoIterator<Item = T>, |
| ) -> &mut [T] { |
| T::allocate_from_iter(self, iter) |
| } |
| } |
| } |
| |
| // Marker types that let us give different behaviour for arenas allocating |
| // `Copy` types vs `!Copy` types. |
| pub struct IsCopy; |
| pub struct IsNotCopy; |
| |
| #[cfg(test)] |
| mod tests; |
