1 use arena::{TypedArena, DroplessArena};
5 use std::cell::RefCell;
6 use std::marker::PhantomData;
7 use smallvec::SmallVec;
9 /// This declares a list of types which can be allocated by `Arena`.
11 /// The `few` modifier will cause allocation to use the shared arena and recording the destructor.
12 /// This is faster and more memory efficient if there's only a few allocations of the type.
13 /// Leaving `few` out will cause the type to get its own dedicated `TypedArena` which is
14 /// faster and more memory efficient if there is lots of allocations.
16 /// Specifying the `decode` modifier will add decode impls for &T and &[T] where T is the type
17 /// listed. These impls will appear in the implement_ty_decoder! macro.
19 macro_rules! arena_types {
20 ($macro:path, $args:tt, $tcx:lifetime) => (
22 [] vtable_method: Option<(
23 rustc::hir::def_id::DefId,
24 rustc::ty::subst::SubstsRef<$tcx>
26 [few, decode] mir_keys: rustc::util::nodemap::DefIdSet,
27 [decode] specialization_graph: rustc::traits::specialization_graph::Graph,
28 [] region_scope_tree: rustc::middle::region::ScopeTree,
29 [] item_local_set: rustc::util::nodemap::ItemLocalSet,
30 [decode] mir_const_qualif: rustc_data_structures::bit_set::BitSet<rustc::mir::Local>,
31 [] trait_impls_of: rustc::ty::trait_def::TraitImpls,
33 rustc::infer::canonical::Canonical<'tcx,
34 rustc::infer::canonical::QueryResponse<'tcx,
35 rustc::traits::query::dropck_outlives::DropckOutlivesResult<'tcx>
38 [] normalize_projection_ty:
39 rustc::infer::canonical::Canonical<'tcx,
40 rustc::infer::canonical::QueryResponse<'tcx,
41 rustc::traits::query::normalize::NormalizationResult<'tcx>
44 [] implied_outlives_bounds:
45 rustc::infer::canonical::Canonical<'tcx,
46 rustc::infer::canonical::QueryResponse<'tcx,
47 Vec<rustc::traits::query::outlives_bounds::OutlivesBound<'tcx>>
51 rustc::infer::canonical::Canonical<'tcx,
52 rustc::infer::canonical::QueryResponse<'tcx, ()>
54 [] type_op_normalize_poly_fn_sig:
55 rustc::infer::canonical::Canonical<'tcx,
56 rustc::infer::canonical::QueryResponse<'tcx, rustc::ty::PolyFnSig<'tcx>>
58 [] type_op_normalize_fn_sig:
59 rustc::infer::canonical::Canonical<'tcx,
60 rustc::infer::canonical::QueryResponse<'tcx, rustc::ty::FnSig<'tcx>>
62 [] type_op_normalize_predicate:
63 rustc::infer::canonical::Canonical<'tcx,
64 rustc::infer::canonical::QueryResponse<'tcx, rustc::ty::Predicate<'tcx>>
66 [] type_op_normalize_ty:
67 rustc::infer::canonical::Canonical<'tcx,
68 rustc::infer::canonical::QueryResponse<'tcx, rustc::ty::Ty<'tcx>>
70 [few] crate_inherent_impls: rustc::ty::CrateInherentImpls,
71 [decode] borrowck: rustc::middle::borrowck::BorrowCheckResult,
72 [few] upstream_monomorphizations:
73 rustc::util::nodemap::DefIdMap<
74 rustc_data_structures::fx::FxHashMap<
75 rustc::ty::subst::SubstsRef<'tcx>,
76 rustc::hir::def_id::CrateNum
79 [few] resolve_lifetimes: rustc::middle::resolve_lifetime::ResolveLifetimes,
80 [decode] generic_predicates: rustc::ty::GenericPredicates<'tcx>,
85 macro_rules! arena_for_type {
89 ([few $(, $attrs:ident)*][$ty:ty]) => {
92 ([$ignore:ident $(, $attrs:ident)*]$args:tt) => {
93 arena_for_type!([$($attrs),*]$args)
97 macro_rules! declare_arena {
98 ([], [$($a:tt $name:ident: $ty:ty,)*], $tcx:lifetime) => {
100 pub struct Arena<$tcx> {
101 dropless: DroplessArena,
103 $($name: arena_for_type!($a[$ty]),)*
108 macro_rules! which_arena_for_type {
109 ([][$arena:expr]) => {
112 ([few$(, $attrs:ident)*][$arena:expr]) => {
115 ([$ignore:ident$(, $attrs:ident)*]$args:tt) => {
116 which_arena_for_type!([$($attrs),*]$args)
120 macro_rules! impl_arena_allocatable {
121 ([], [$($a:tt $name:ident: $ty:ty,)*], $tcx:lifetime) => {
123 impl ArenaAllocatable for $ty {}
124 unsafe impl<$tcx> ArenaField<$tcx> for $ty {
126 fn arena<'a>(_arena: &'a Arena<$tcx>) -> Option<&'a TypedArena<Self>> {
127 which_arena_for_type!($a[&_arena.$name])
134 arena_types!(declare_arena, [], 'tcx);
136 arena_types!(impl_arena_allocatable, [], 'tcx);
138 pub trait ArenaAllocatable {}
140 impl<T: Copy> ArenaAllocatable for T {}
142 unsafe trait ArenaField<'tcx>: Sized {
143 /// Returns a specific arena to allocate from.
144 /// If None is returned, the DropArena will be used.
145 fn arena<'a>(arena: &'a Arena<'tcx>) -> Option<&'a TypedArena<Self>>;
148 unsafe impl<'tcx, T> ArenaField<'tcx> for T {
150 default fn arena<'a>(_: &'a Arena<'tcx>) -> Option<&'a TypedArena<Self>> {
155 impl<'tcx> Arena<'tcx> {
157 pub fn alloc<T: ArenaAllocatable>(&self, value: T) -> &mut T {
158 if !mem::needs_drop::<T>() {
159 return self.dropless.alloc(value);
161 match <T as ArenaField<'tcx>>::arena(self) {
162 Some(arena) => arena.alloc(value),
163 None => unsafe { self.drop.alloc(value) },
168 pub fn alloc_slice<T: Copy>(&self, value: &[T]) -> &mut [T] {
169 if value.len() == 0 {
172 self.dropless.alloc_slice(value)
175 pub fn alloc_from_iter<
177 I: IntoIterator<Item = T>
182 if !mem::needs_drop::<T>() {
183 return self.dropless.alloc_from_iter(iter);
185 match <T as ArenaField<'tcx>>::arena(self) {
186 Some(arena) => arena.alloc_from_iter(iter),
187 None => unsafe { self.drop.alloc_from_iter(iter) },
192 /// Calls the destructor for an object when dropped.
194 drop_fn: unsafe fn(*mut u8),
198 unsafe fn drop_for_type<T>(to_drop: *mut u8) {
199 std::ptr::drop_in_place(to_drop as *mut T)
202 impl Drop for DropType {
205 (self.drop_fn)(self.obj)
210 /// An arena which can be used to allocate any type.
211 /// Allocating in this arena is unsafe since the type system
212 /// doesn't know which types it contains. In order to
213 /// allocate safely, you must store a PhantomData<T>
214 /// alongside this arena for each type T you allocate.
217 /// A list of destructors to run when the arena drops.
218 /// Ordered so `destructors` gets dropped before the arena
219 /// since its destructor can reference memory in the arena.
220 destructors: RefCell<Vec<DropType>>,
221 arena: DroplessArena,
226 unsafe fn alloc<T>(&self, object: T) -> &mut T {
227 let mem = self.arena.alloc_raw(
230 ) as *mut _ as *mut T;
231 // Write into uninitialized memory.
232 ptr::write(mem, object);
233 let result = &mut *mem;
234 // Record the destructor after doing the allocation as that may panic
235 // and would cause `object`'s destuctor to run twice if it was recorded before
236 self.destructors.borrow_mut().push(DropType {
237 drop_fn: drop_for_type::<T>,
238 obj: result as *mut T as *mut u8,
244 unsafe fn alloc_from_iter<T, I: IntoIterator<Item = T>>(&self, iter: I) -> &mut [T] {
245 let mut vec: SmallVec<[_; 8]> = iter.into_iter().collect();
251 let start_ptr = self.arena.alloc_raw(
252 len.checked_mul(mem::size_of::<T>()).unwrap(),
254 ) as *mut _ as *mut T;
256 let mut destructors = self.destructors.borrow_mut();
257 // Reserve space for the destructors so we can't panic while adding them
258 destructors.reserve(len);
260 // Move the content to the arena by copying it and then forgetting
261 // the content of the SmallVec
262 vec.as_ptr().copy_to_nonoverlapping(start_ptr, len);
263 mem::forget(vec.drain());
265 // Record the destructors after doing the allocation as that may panic
266 // and would cause `object`'s destuctor to run twice if it was recorded before
268 destructors.push(DropType {
269 drop_fn: drop_for_type::<T>,
270 obj: start_ptr.offset(i as isize) as *mut u8,
274 slice::from_raw_parts_mut(start_ptr, len)