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Auto merge of #124662 - zetanumbers:needs_async_drop, r=oli-obk 

Implement `needs_async_drop` in rustc and optimize async drop glue

This PR expands on #121801 and implements `Ty::needs_async_drop` which works almost exactly the same as `Ty::needs_drop`, which is needed for #123948.

Also made compiler's async drop code to look more like compiler's regular drop code, which enabled me to write an optimization where types which do not use `AsyncDrop` can simply forward async drop glue to `drop_in_place`. This made size of the async block from the [async_drop test](67980dd6fb/tests/ui/async-await/async-drop.rs) to decrease by 12%.
This commit is contained in:
bors 2024-05-31 10:12:24 +00:00
parent bf8fff783f 4903cf4df6
commit 99cb42c296
19 changed files with 382 additions and 194 deletions
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1
compiler/rustc_hir/src/lang_items.rs
View File

@ -176,6 +176,7 @@ language_item_table! {
AsyncDropSlice, sym::async_drop_slice, async_drop_slice_fn, Target::Fn, GenericRequirement::Exact(1);
AsyncDropChain, sym::async_drop_chain, async_drop_chain_fn, Target::Fn, GenericRequirement::Exact(2);
AsyncDropNoop, sym::async_drop_noop, async_drop_noop_fn, Target::Fn, GenericRequirement::Exact(0);
AsyncDropDeferredDropInPlace, sym::async_drop_deferred_drop_in_place, async_drop_deferred_drop_in_place_fn, Target::Fn, GenericRequirement::Exact(1);
AsyncDropFuse, sym::async_drop_fuse, async_drop_fuse_fn, Target::Fn, GenericRequirement::Exact(1);
AsyncDropDefer, sym::async_drop_defer, async_drop_defer_fn, Target::Fn, GenericRequirement::Exact(1);
AsyncDropEither, sym::async_drop_either, async_drop_either_fn, Target::Fn, GenericRequirement::Exact(3);

5
compiler/rustc_hir_analysis/src/check/mod.rs
View File

@ -112,6 +112,7 @@ pub fn provide(providers: &mut Providers) {
wfcheck::provide(providers);
*providers = Providers {
adt_destructor,
adt_async_destructor,
region_scope_tree,
collect_return_position_impl_trait_in_trait_tys,
compare_impl_const: compare_impl_item::compare_impl_const_raw,
@ -124,6 +125,10 @@ fn adt_destructor(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option<ty::Destructor>
tcx.calculate_dtor(def_id.to_def_id(), dropck::check_drop_impl)
}
fn adt_async_destructor(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option<ty::AsyncDestructor> {
tcx.calculate_async_dtor(def_id.to_def_id(), dropck::check_drop_impl)
}
/// Given a `DefId` for an opaque type in return position, find its parent item's return
/// expressions.
fn get_owner_return_paths(

4
compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
View File

@ -287,6 +287,10 @@ provide! { tcx, def_id, other, cdata,
let _ = cdata;
tcx.calculate_dtor(def_id, |_,_| Ok(()))
}
adt_async_destructor => {
let _ = cdata;
tcx.calculate_async_dtor(def_id, |_,_| Ok(()))
}
associated_item_def_ids => {
tcx.arena.alloc_from_iter(cdata.get_associated_item_or_field_def_ids(def_id.index))
}

2
compiler/rustc_middle/src/query/erase.rs
View File

@ -238,6 +238,7 @@ trivial! {
Option<rustc_hir::CoroutineKind>,
Option<rustc_hir::HirId>,
Option<rustc_middle::middle::stability::DeprecationEntry>,
Option<rustc_middle::ty::AsyncDestructor>,
Option<rustc_middle::ty::Destructor>,
Option<rustc_middle::ty::ImplTraitInTraitData>,
Option<rustc_middle::ty::ScalarInt>,
@ -295,6 +296,7 @@ trivial! {
rustc_middle::ty::AssocItem,
rustc_middle::ty::AssocItemContainer,
rustc_middle::ty::Asyncness,
rustc_middle::ty::AsyncDestructor,
rustc_middle::ty::BoundVariableKind,
rustc_middle::ty::DeducedParamAttrs,
rustc_middle::ty::Destructor,

17
compiler/rustc_middle/src/query/mod.rs
View File

@ -703,6 +703,11 @@ rustc_queries! {
cache_on_disk_if { key.is_local() }
separate_provide_extern
}
query adt_async_destructor(key: DefId) -> Option<ty::AsyncDestructor> {
desc { |tcx| "computing `AsyncDrop` impl for `{}`", tcx.def_path_str(key) }
cache_on_disk_if { key.is_local() }
separate_provide_extern
}
query adt_sized_constraint(key: DefId) -> Option<ty::EarlyBinder<'tcx, Ty<'tcx>>> {
desc { |tcx| "computing the `Sized` constraint for `{}`", tcx.def_path_str(key) }
@ -1343,18 +1348,14 @@ rustc_queries! {
query is_unpin_raw(env: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool {
desc { "computing whether `{}` is `Unpin`", env.value }
}
/// Query backing `Ty::has_surface_async_drop`.
query has_surface_async_drop_raw(env: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool {
desc { "computing whether `{}` has `AsyncDrop` implementation", env.value }
}
/// Query backing `Ty::has_surface_drop`.
query has_surface_drop_raw(env: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool {
desc { "computing whether `{}` has `Drop` implementation", env.value }
}
/// Query backing `Ty::needs_drop`.
query needs_drop_raw(env: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool {
desc { "computing whether `{}` needs drop", env.value }
}
/// Query backing `Ty::needs_async_drop`.
query needs_async_drop_raw(env: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool {
desc { "computing whether `{}` needs async drop", env.value }
}
/// Query backing `Ty::has_significant_drop_raw`.
query has_significant_drop_raw(env: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool {
desc { "computing whether `{}` has a significant drop", env.value }

10
compiler/rustc_middle/src/ty/adt.rs
View File

@ -24,7 +24,9 @@ use std::hash::{Hash, Hasher};
use std::ops::Range;
use std::str;
use super::{Destructor, FieldDef, GenericPredicates, Ty, TyCtxt, VariantDef, VariantDiscr};
use super::{
AsyncDestructor, Destructor, FieldDef, GenericPredicates, Ty, TyCtxt, VariantDef, VariantDiscr,
};
#[derive(Clone, Copy, PartialEq, Eq, Hash, HashStable, TyEncodable, TyDecodable)]
pub struct AdtFlags(u16);
@ -577,6 +579,12 @@ impl<'tcx> AdtDef<'tcx> {
tcx.adt_destructor(self.did())
}
// FIXME: consider combining this method with `AdtDef::destructor` and removing
// this version
pub fn async_destructor(self, tcx: TyCtxt<'tcx>) -> Option<AsyncDestructor> {
tcx.adt_async_destructor(self.did())
}
/// Returns a type such that `Self: Sized` if and only if that type is `Sized`,
/// or `None` if the type is always sized.
pub fn sized_constraint(self, tcx: TyCtxt<'tcx>) -> Option<ty::EarlyBinder<'tcx, Ty<'tcx>>> {

9
compiler/rustc_middle/src/ty/mod.rs
View File

@ -1172,6 +1172,15 @@ pub struct Destructor {
pub constness: hir::Constness,
}
// FIXME: consider combining this definition with regular `Destructor`
#[derive(Copy, Clone, Debug, HashStable, Encodable, Decodable)]
pub struct AsyncDestructor {
/// The `DefId` of the async destructor future constructor
pub ctor: DefId,
/// The `DefId` of the async destructor future type
pub future: DefId,
}
#[derive(Clone, Copy, PartialEq, Eq, HashStable, TyEncodable, TyDecodable)]
pub struct VariantFlags(u8);
bitflags::bitflags! {

74
compiler/rustc_middle/src/ty/sty.rs
View File

@ -25,7 +25,7 @@ use std::assert_matches::debug_assert_matches;
use std::borrow::Cow;
use std::iter;
use std::ops::{ControlFlow, Range};
use ty::util::IntTypeExt;
use ty::util::{AsyncDropGlueMorphology, IntTypeExt};
use rustc_type_ir::TyKind::*;
use rustc_type_ir::{self as ir, BoundVar, CollectAndApply, DynKind};
@ -1951,11 +1951,22 @@ impl<'tcx> Ty<'tcx> {
}
/// Returns the type of the async destructor of this type.
pub fn async_destructor_ty(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> Ty<'tcx> {
if self.is_async_destructor_noop(tcx, param_env) || matches!(self.kind(), ty::Error(_)) {
return Ty::async_destructor_combinator(tcx, LangItem::AsyncDropNoop)
.instantiate_identity();
pub fn async_destructor_ty(self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
match self.async_drop_glue_morphology(tcx) {
AsyncDropGlueMorphology::Noop => {
return Ty::async_destructor_combinator(tcx, LangItem::AsyncDropNoop)
.instantiate_identity();
}
AsyncDropGlueMorphology::DeferredDropInPlace => {
let drop_in_place =
Ty::async_destructor_combinator(tcx, LangItem::AsyncDropDeferredDropInPlace)
.instantiate(tcx, &[self.into()]);
return Ty::async_destructor_combinator(tcx, LangItem::AsyncDropFuse)
.instantiate(tcx, &[drop_in_place.into()]);
}
AsyncDropGlueMorphology::Custom => (),
}
match *self.kind() {
ty::Param(_) | ty::Alias(..) | ty::Infer(ty::TyVar(_)) => {
let assoc_items = tcx
@ -1974,24 +1985,18 @@ impl<'tcx> Ty<'tcx> {
.adt_async_destructor_ty(
tcx,
adt_def.variants().iter().map(|v| v.fields.iter().map(|f| f.ty(tcx, args))),
param_env,
),
ty::Tuple(tys) => self.adt_async_destructor_ty(tcx, iter::once(tys), param_env),
ty::Closure(_, args) => self.adt_async_destructor_ty(
tcx,
iter::once(args.as_closure().upvar_tys()),
param_env,
),
ty::CoroutineClosure(_, args) => self.adt_async_destructor_ty(
tcx,
iter::once(args.as_coroutine_closure().upvar_tys()),
param_env,
),
ty::Tuple(tys) => self.adt_async_destructor_ty(tcx, iter::once(tys)),
ty::Closure(_, args) => {
self.adt_async_destructor_ty(tcx, iter::once(args.as_closure().upvar_tys()))
}
ty::CoroutineClosure(_, args) => self
.adt_async_destructor_ty(tcx, iter::once(args.as_coroutine_closure().upvar_tys())),
ty::Adt(adt_def, _) => {
assert!(adt_def.is_union());
let surface_drop = self.surface_async_dropper_ty(tcx, param_env).unwrap();
let surface_drop = self.surface_async_dropper_ty(tcx).unwrap();
Ty::async_destructor_combinator(tcx, LangItem::AsyncDropFuse)
.instantiate(tcx, &[surface_drop.into()])
@ -2008,17 +2013,12 @@ impl<'tcx> Ty<'tcx> {
}
}
fn adt_async_destructor_ty<I>(
self,
tcx: TyCtxt<'tcx>,
variants: I,
param_env: ParamEnv<'tcx>,
) -> Ty<'tcx>
fn adt_async_destructor_ty<I>(self, tcx: TyCtxt<'tcx>, variants: I) -> Ty<'tcx>
where
I: Iterator + ExactSizeIterator,
I::Item: IntoIterator<Item = Ty<'tcx>>,
{
debug_assert!(!self.is_async_destructor_noop(tcx, param_env));
debug_assert_eq!(self.async_drop_glue_morphology(tcx), AsyncDropGlueMorphology::Custom);
let defer = Ty::async_destructor_combinator(tcx, LangItem::AsyncDropDefer);
let chain = Ty::async_destructor_combinator(tcx, LangItem::AsyncDropChain);
@ -2041,7 +2041,7 @@ impl<'tcx> Ty<'tcx> {
})
.unwrap();
let dtor = if let Some(dropper_ty) = self.surface_async_dropper_ty(tcx, param_env) {
let dtor = if let Some(dropper_ty) = self.surface_async_dropper_ty(tcx) {
Ty::async_destructor_combinator(tcx, LangItem::AsyncDropChain)
.instantiate(tcx, &[dropper_ty.into(), variants_dtor.into()])
} else {
@ -2052,21 +2052,13 @@ impl<'tcx> Ty<'tcx> {
.instantiate(tcx, &[dtor.into()])
}
fn surface_async_dropper_ty(
self,
tcx: TyCtxt<'tcx>,
param_env: ParamEnv<'tcx>,
) -> Option<Ty<'tcx>> {
if self.has_surface_async_drop(tcx, param_env) {
Some(LangItem::SurfaceAsyncDropInPlace)
} else if self.has_surface_drop(tcx, param_env) {
Some(LangItem::AsyncDropSurfaceDropInPlace)
} else {
None
}
.map(|dropper| {
Ty::async_destructor_combinator(tcx, dropper).instantiate(tcx, &[self.into()])
})
fn surface_async_dropper_ty(self, tcx: TyCtxt<'tcx>) -> Option<Ty<'tcx>> {
let adt_def = self.ty_adt_def()?;
let dropper = adt_def
.async_destructor(tcx)
.map(|_| LangItem::SurfaceAsyncDropInPlace)
.or_else(|| adt_def.destructor(tcx).map(|_| LangItem::AsyncDropSurfaceDropInPlace))?;
Some(Ty::async_destructor_combinator(tcx, dropper).instantiate(tcx, &[self.into()]))
}
fn async_destructor_combinator(

265
compiler/rustc_middle/src/ty/util.rs
View File

@ -4,7 +4,7 @@ use crate::middle::codegen_fn_attrs::CodegenFnAttrFlags;
use crate::query::{IntoQueryParam, Providers};
use crate::ty::layout::{FloatExt, IntegerExt};
use crate::ty::{
self, FallibleTypeFolder, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable,
self, Asyncness, FallibleTypeFolder, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable,
TypeVisitableExt, Upcast,
};
use crate::ty::{GenericArgKind, GenericArgsRef};
@ -382,6 +382,64 @@ impl<'tcx> TyCtxt<'tcx> {
Some(ty::Destructor { did, constness })
}
/// Calculate the async destructor of a given type.
pub fn calculate_async_dtor(
self,
adt_did: DefId,
validate: impl Fn(Self, DefId) -> Result<(), ErrorGuaranteed>,
) -> Option<ty::AsyncDestructor> {
let async_drop_trait = self.lang_items().async_drop_trait()?;
self.ensure().coherent_trait(async_drop_trait).ok()?;
let ty = self.type_of(adt_did).instantiate_identity();
let mut dtor_candidate = None;
self.for_each_relevant_impl(async_drop_trait, ty, |impl_did| {
if validate(self, impl_did).is_err() {
// Already `ErrorGuaranteed`, no need to delay a span bug here.
return;
}
let [future, ctor] = self.associated_item_def_ids(impl_did) else {
self.dcx().span_delayed_bug(
self.def_span(impl_did),
"AsyncDrop impl without async_drop function or Dropper type",
);
return;
};
if let Some((_, _, old_impl_did)) = dtor_candidate {
self.dcx()
.struct_span_err(self.def_span(impl_did), "multiple async drop impls found")
.with_span_note(self.def_span(old_impl_did), "other impl here")
.delay_as_bug();
}
dtor_candidate = Some((*future, *ctor, impl_did));
});
let (future, ctor, _) = dtor_candidate?;
Some(ty::AsyncDestructor { future, ctor })
}
/// Returns async drop glue morphology for a definition. To get async drop
/// glue morphology for a type see [`Ty::async_drop_glue_morphology`].
//
// FIXME: consider making this a query
pub fn async_drop_glue_morphology(self, did: DefId) -> AsyncDropGlueMorphology {
let ty: Ty<'tcx> = self.type_of(did).instantiate_identity();
// Async drop glue morphology is an internal detail, so reveal_all probably
// should be fine
let param_env = ty::ParamEnv::reveal_all();
if ty.needs_async_drop(self, param_env) {
AsyncDropGlueMorphology::Custom
} else if ty.needs_drop(self, param_env) {
AsyncDropGlueMorphology::DeferredDropInPlace
} else {
AsyncDropGlueMorphology::Noop
}
}
/// Returns the set of types that are required to be alive in
/// order to run the destructor of `def` (see RFCs 769 and
/// 1238).
@ -1138,6 +1196,18 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for WeakAliasTypeExpander<'tcx> {
}
}
/// Indicates the form of `AsyncDestruct::Destructor`. Used to simplify async
/// drop glue for types not using async drop.
#[derive(Clone, Copy, PartialEq, Eq, Debug)]
pub enum AsyncDropGlueMorphology {
/// Async destructor simply does nothing
Noop,
/// Async destructor simply runs `drop_in_place`
DeferredDropInPlace,
/// Async destructor has custom logic
Custom,
}
impl<'tcx> Ty<'tcx> {
/// Returns the `Size` for primitive types (bool, uint, int, char, float).
pub fn primitive_size(self, tcx: TyCtxt<'tcx>) -> Size {
@ -1303,80 +1373,16 @@ impl<'tcx> Ty<'tcx> {
}
}
/// Checks whether values of this type `T` implements the `AsyncDrop`
/// trait.
pub fn has_surface_async_drop(self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> bool {
self.could_have_surface_async_drop() && tcx.has_surface_async_drop_raw(param_env.and(self))
}
/// Fast path helper for testing if a type has `AsyncDrop`
/// implementation.
///
/// Returning `false` means the type is known to not have `AsyncDrop`
/// implementation. Returning `true` means nothing -- could be
/// `AsyncDrop`, might not be.
fn could_have_surface_async_drop(self) -> bool {
!self.is_async_destructor_trivially_noop()
&& !matches!(
self.kind(),
ty::Tuple(_)
| ty::Slice(_)
| ty::Array(_, _)
| ty::Closure(..)
| ty::CoroutineClosure(..)
| ty::Coroutine(..)
)
}
/// Checks whether values of this type `T` implements the `Drop`
/// trait.
pub fn has_surface_drop(self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> bool {
self.could_have_surface_drop() && tcx.has_surface_drop_raw(param_env.and(self))
}
/// Fast path helper for testing if a type has `Drop` implementation.
///
/// Returning `false` means the type is known to not have `Drop`
/// implementation. Returning `true` means nothing -- could be
/// `Drop`, might not be.
fn could_have_surface_drop(self) -> bool {
!self.is_async_destructor_trivially_noop()
&& !matches!(
self.kind(),
ty::Tuple(_)
| ty::Slice(_)
| ty::Array(_, _)
| ty::Closure(..)
| ty::CoroutineClosure(..)
| ty::Coroutine(..)
)
}
/// Checks whether values of this type `T` implement has noop async destructor.
/// Get morphology of the async drop glue, needed for types which do not
/// use async drop. To get async drop glue morphology for a definition see
/// [`TyCtxt::async_drop_glue_morphology`]. Used for `AsyncDestruct::Destructor`
/// type construction.
//
// FIXME: implement optimization to make ADTs, which do not need drop,
// to skip fields or to have noop async destructor.
pub fn is_async_destructor_noop(
self,
tcx: TyCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
) -> bool {
self.is_async_destructor_trivially_noop()
|| if let ty::Adt(adt_def, _) = self.kind() {
(adt_def.is_union() || adt_def.is_payloadfree())
&& !self.has_surface_async_drop(tcx, param_env)
&& !self.has_surface_drop(tcx, param_env)
} else {
false
}
}
/// Fast path helper for testing if a type has noop async destructor.
///
/// Returning `true` means the type is known to have noop async destructor
/// implementation. Returning `true` means nothing -- could be
/// `Drop`, might not be.
fn is_async_destructor_trivially_noop(self) -> bool {
// FIXME: implement optimization to not instantiate a certain morphology of
// async drop glue too soon to allow per type optimizations, see array case
// for more info. Perhaps then remove this method and use `needs_(async_)drop`
// instead.
pub fn async_drop_glue_morphology(self, tcx: TyCtxt<'tcx>) -> AsyncDropGlueMorphology {
match self.kind() {
ty::Int(_)
| ty::Uint(_)
@ -1388,10 +1394,43 @@ impl<'tcx> Ty<'tcx> {
| ty::Ref(..)
| ty::RawPtr(..)
| ty::FnDef(..)
| ty::FnPtr(_) => true,
ty::Tuple(tys) => tys.is_empty(),
ty::Adt(adt_def, _) => adt_def.is_manually_drop(),
_ => false,
| ty::FnPtr(_)
| ty::Infer(ty::FreshIntTy(_))
| ty::Infer(ty::FreshFloatTy(_)) => AsyncDropGlueMorphology::Noop,
ty::Tuple(tys) if tys.is_empty() => AsyncDropGlueMorphology::Noop,
ty::Adt(adt_def, _) if adt_def.is_manually_drop() => AsyncDropGlueMorphology::Noop,
// Foreign types can never have destructors.
ty::Foreign(_) => AsyncDropGlueMorphology::Noop,
// FIXME: implement dynamic types async drops
ty::Error(_) | ty::Dynamic(..) => AsyncDropGlueMorphology::DeferredDropInPlace,
ty::Tuple(_) | ty::Array(_, _) | ty::Slice(_) => {
// Assume worst-case scenario, because we can instantiate async
// destructors in different orders:
//
// 1. Instantiate [T; N] with T = String and N = 0
// 2. Instantiate <[String; 0] as AsyncDestruct>::Destructor
//
// And viceversa, thus we cannot rely on String not using async
// drop or array having zero (0) elements
AsyncDropGlueMorphology::Custom
}
ty::Pat(ty, _) => ty.async_drop_glue_morphology(tcx),
ty::Adt(adt_def, _) => tcx.async_drop_glue_morphology(adt_def.did()),
ty::Closure(did, _)
| ty::CoroutineClosure(did, _)
| ty::Coroutine(did, _)
| ty::CoroutineWitness(did, _) => tcx.async_drop_glue_morphology(*did),
ty::Alias(..) | ty::Param(_) | ty::Bound(..) | ty::Placeholder(..) | ty::Infer(_) => {
// No specifics, but would usually mean forwarding async drop glue
AsyncDropGlueMorphology::Custom
}
}
}
@ -1430,6 +1469,46 @@ impl<'tcx> Ty<'tcx> {
}
}
/// If `ty.needs_async_drop(...)` returns `true`, then `ty` is definitely
/// non-copy and *might* have a async destructor attached; if it returns
/// `false`, then `ty` definitely has no async destructor (i.e., no async
/// drop glue).
///
/// (Note that this implies that if `ty` has an async destructor attached,
/// then `needs_async_drop` will definitely return `true` for `ty`.)
///
/// When constructing `AsyncDestruct::Destructor` type, use
/// [`Ty::async_drop_glue_morphology`] instead.
//
// FIXME(zetanumbers): Note that this method is used to check eligible types
// in unions.
#[inline]
pub fn needs_async_drop(self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> bool {
// Avoid querying in simple cases.
match needs_drop_components(tcx, self) {
Err(AlwaysRequiresDrop) => true,
Ok(components) => {
let query_ty = match *components {
[] => return false,
// If we've got a single component, call the query with that
// to increase the chance that we hit the query cache.
[component_ty] => component_ty,
_ => self,
};
// This doesn't depend on regions, so try to minimize distinct
// query keys used.
// If normalization fails, we just use `query_ty`.
debug_assert!(!param_env.has_infer());
let query_ty = tcx
.try_normalize_erasing_regions(param_env, query_ty)
.unwrap_or_else(|_| tcx.erase_regions(query_ty));
tcx.needs_async_drop_raw(param_env.and(query_ty))
}
}
}
/// Checks if `ty` has a significant drop.
///
/// Note that this method can return false even if `ty` has a destructor
@ -1601,9 +1680,24 @@ impl<'tcx> ExplicitSelf<'tcx> {
/// Returns a list of types such that the given type needs drop if and only if
/// *any* of the returned types need drop. Returns `Err(AlwaysRequiresDrop)` if
/// this type always needs drop.
//
// FIXME(zetanumbers): consider replacing this with only
// `needs_drop_components_with_async`
#[inline]
pub fn needs_drop_components<'tcx>(
tcx: TyCtxt<'tcx>,
ty: Ty<'tcx>,
) -> Result<SmallVec<[Ty<'tcx>; 2]>, AlwaysRequiresDrop> {
needs_drop_components_with_async(tcx, ty, Asyncness::No)
}
/// Returns a list of types such that the given type needs drop if and only if
/// *any* of the returned types need drop. Returns `Err(AlwaysRequiresDrop)` if
/// this type always needs drop.
pub fn needs_drop_components_with_async<'tcx>(
tcx: TyCtxt<'tcx>,
ty: Ty<'tcx>,
asyncness: Asyncness,
) -> Result<SmallVec<[Ty<'tcx>; 2]>, AlwaysRequiresDrop> {
match *ty.kind() {
ty::Infer(ty::FreshIntTy(_))
@ -1623,11 +1717,18 @@ pub fn needs_drop_components<'tcx>(
// Foreign types can never have destructors.
ty::Foreign(..) => Ok(SmallVec::new()),
ty::Dynamic(..) | ty::Error(_) => Err(AlwaysRequiresDrop),
// FIXME(zetanumbers): Temporary workaround for async drop of dynamic types
ty::Dynamic(..) | ty::Error(_) => {
if asyncness.is_async() {
Ok(SmallVec::new())
} else {
Err(AlwaysRequiresDrop)
}
}
ty::Pat(ty, _) | ty::Slice(ty) => needs_drop_components(tcx, ty),
ty::Pat(ty, _) | ty::Slice(ty) => needs_drop_components_with_async(tcx, ty, asyncness),
ty::Array(elem_ty, size) => {
match needs_drop_components(tcx, elem_ty) {
match needs_drop_components_with_async(tcx, elem_ty, asyncness) {
Ok(v) if v.is_empty() => Ok(v),
res => match size.try_to_target_usize(tcx) {
// Arrays of size zero don't need drop, even if their element
@ -1643,7 +1744,7 @@ pub fn needs_drop_components<'tcx>(
}
// If any field needs drop, then the whole tuple does.
ty::Tuple(fields) => fields.iter().try_fold(SmallVec::new(), move |mut acc, elem| {
acc.extend(needs_drop_components(tcx, elem)?);
acc.extend(needs_drop_components_with_async(tcx, elem, asyncness)?);
Ok(acc)
}),

37
compiler/rustc_mir_transform/src/shim/async_destructor_ctor.rs
View File

@ -12,7 +12,7 @@ use rustc_middle::mir::{
Terminator, TerminatorKind, UnwindAction, UnwindTerminateReason, RETURN_PLACE,
};
use rustc_middle::ty::adjustment::PointerCoercion;
use rustc_middle::ty::util::Discr;
use rustc_middle::ty::util::{AsyncDropGlueMorphology, Discr};
use rustc_middle::ty::{self, Ty, TyCtxt};
use rustc_middle::{bug, span_bug};
use rustc_span::source_map::respan;
@ -116,15 +116,25 @@ impl<'tcx> AsyncDestructorCtorShimBuilder<'tcx> {
}
fn build(self) -> Body<'tcx> {
let (tcx, def_id, Some(self_ty)) = (self.tcx, self.def_id, self.self_ty) else {
let (tcx, Some(self_ty)) = (self.tcx, self.self_ty) else {
return self.build_zst_output();
};
match self_ty.async_drop_glue_morphology(tcx) {
AsyncDropGlueMorphology::Noop => span_bug!(
self.span,
"async drop glue shim generator encountered type with noop async drop glue morphology"
),
AsyncDropGlueMorphology::DeferredDropInPlace => {
return self.build_deferred_drop_in_place();
}
AsyncDropGlueMorphology::Custom => (),
}
let surface_drop_kind = || {
let param_env = tcx.param_env_reveal_all_normalized(def_id);
if self_ty.has_surface_async_drop(tcx, param_env) {
let adt_def = self_ty.ty_adt_def()?;
if adt_def.async_destructor(tcx).is_some() {
Some(SurfaceDropKind::Async)
} else if self_ty.has_surface_drop(tcx, param_env) {
} else if adt_def.destructor(tcx).is_some() {
Some(SurfaceDropKind::Sync)
} else {
None
@ -267,6 +277,13 @@ impl<'tcx> AsyncDestructorCtorShimBuilder<'tcx> {
self.return_()
}
fn build_deferred_drop_in_place(mut self) -> Body<'tcx> {
self.put_self();
let deferred = self.combine_deferred_drop_in_place();
self.combine_fuse(deferred);
self.return_()
}
fn build_fused_async_surface(mut self) -> Body<'tcx> {
self.put_self();
let surface = self.combine_async_surface();
@ -441,6 +458,14 @@ impl<'tcx> AsyncDestructorCtorShimBuilder<'tcx> {
)
}
fn combine_deferred_drop_in_place(&mut self) -> Ty<'tcx> {
self.apply_combinator(
1,
LangItem::AsyncDropDeferredDropInPlace,
&[self.self_ty.unwrap().into()],
)
}
fn combine_fuse(&mut self, inner_future_ty: Ty<'tcx>) -> Ty<'tcx> {
self.apply_combinator(1, LangItem::AsyncDropFuse, &[inner_future_ty.into()])
}
@ -481,7 +506,7 @@ impl<'tcx> AsyncDestructorCtorShimBuilder<'tcx> {
if let Some(ty) = self.self_ty {
debug_assert_eq!(
output.ty(&self.locals, self.tcx),
ty.async_destructor_ty(self.tcx, self.param_env),
ty.async_destructor_ty(self.tcx),
"output async destructor types did not match for type: {ty:?}",
);
}

1
compiler/rustc_span/src/symbol.rs
View File

@ -429,6 +429,7 @@ symbols! {
async_drop,
async_drop_chain,
async_drop_defer,
async_drop_deferred_drop_in_place,
async_drop_either,
async_drop_fuse,
async_drop_in_place,

2
compiler/rustc_trait_selection/src/solve/normalizes_to/mod.rs
View File

@ -845,7 +845,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for NormalizesTo<'tcx> {
| ty::Str
| ty::Slice(_)
| ty::Tuple(_)
| ty::Error(_) => self_ty.async_destructor_ty(ecx.interner(), goal.param_env),
| ty::Error(_) => self_ty.async_destructor_ty(ecx.interner()),
// We do not call `Ty::async_destructor_ty` on alias, param, or placeholder
// types, which return `<self_ty as AsyncDestruct>::AsyncDestructor`

2
compiler/rustc_trait_selection/src/traits/project.rs
View File

@ -1560,7 +1560,7 @@ fn confirm_builtin_candidate<'cx, 'tcx>(
let destructor_def_id = tcx.associated_item_def_ids(trait_def_id)[0];
assert_eq!(destructor_def_id, item_def_id);
(self_ty.async_destructor_ty(tcx, obligation.param_env).into(), Vec::new())
(self_ty.async_destructor_ty(tcx).into(), Vec::new())
} else if lang_items.pointee_trait() == Some(trait_def_id) {
let metadata_def_id = tcx.require_lang_item(LangItem::Metadata, None);
assert_eq!(metadata_def_id, item_def_id);

21
compiler/rustc_ty_utils/src/common_traits.rs
View File

@ -22,17 +22,6 @@ fn is_unpin_raw<'tcx>(tcx: TyCtxt<'tcx>, query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>)
is_item_raw(tcx, query, LangItem::Unpin)
}
fn has_surface_async_drop_raw<'tcx>(
tcx: TyCtxt<'tcx>,
query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>,
) -> bool {
is_item_raw(tcx, query, LangItem::AsyncDrop)
}
fn has_surface_drop_raw<'tcx>(tcx: TyCtxt<'tcx>, query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool {
is_item_raw(tcx, query, LangItem::Drop)
}
fn is_item_raw<'tcx>(
tcx: TyCtxt<'tcx>,
query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>,
@ -45,13 +34,5 @@ fn is_item_raw<'tcx>(
}
pub(crate) fn provide(providers: &mut Providers) {
*providers = Providers {
is_copy_raw,
is_sized_raw,
is_freeze_raw,
is_unpin_raw,
has_surface_async_drop_raw,
has_surface_drop_raw,
..*providers
};
*providers = Providers { is_copy_raw, is_sized_raw, is_freeze_raw, is_unpin_raw, ..*providers };
}

3
compiler/rustc_ty_utils/src/instance.rs
View File

@ -4,6 +4,7 @@ use rustc_infer::infer::TyCtxtInferExt;
use rustc_middle::bug;
use rustc_middle::query::Providers;
use rustc_middle::traits::{BuiltinImplSource, CodegenObligationError};
use rustc_middle::ty::util::AsyncDropGlueMorphology;
use rustc_middle::ty::GenericArgsRef;
use rustc_middle::ty::{self, Instance, TyCtxt, TypeVisitableExt};
use rustc_span::sym;
@ -59,7 +60,7 @@ fn resolve_instance<'tcx>(
} else if Some(def_id) == tcx.lang_items().async_drop_in_place_fn() {
let ty = args.type_at(0);
if !ty.is_async_destructor_noop(tcx, param_env) {
if ty.async_drop_glue_morphology(tcx) != AsyncDropGlueMorphology::Noop {
match *ty.kind() {
ty::Closure(..)
| ty::CoroutineClosure(..)

16
compiler/rustc_ty_utils/src/needs_drop.rs
View File

@ -30,6 +30,21 @@ fn needs_drop_raw<'tcx>(tcx: TyCtxt<'tcx>, query: ty::ParamEnvAnd<'tcx, Ty<'tcx>
res
}
fn needs_async_drop_raw<'tcx>(tcx: TyCtxt<'tcx>, query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool {
// If we don't know a type doesn't need async drop, for example if it's a
// type parameter without a `Copy` bound, then we conservatively return that
// it needs async drop.
let adt_has_async_dtor =
|adt_def: ty::AdtDef<'tcx>| adt_def.async_destructor(tcx).map(|_| DtorType::Significant);
let res = drop_tys_helper(tcx, query.value, query.param_env, adt_has_async_dtor, false)
.filter(filter_array_elements(tcx, query.param_env))
.next()
.is_some();
debug!("needs_drop_raw({:?}) = {:?}", query, res);
res
}
/// HACK: in order to not mistakenly assume that `[PhantomData<T>; N]` requires drop glue
/// we check the element type for drop glue. The correct fix would be looking at the
/// entirety of the code around `needs_drop_components` and this file and come up with
@ -389,6 +404,7 @@ fn adt_significant_drop_tys(
pub(crate) fn provide(providers: &mut Providers) {
*providers = Providers {
needs_drop_raw,
needs_async_drop_raw,
has_significant_drop_raw,
adt_drop_tys,
adt_significant_drop_tys,

13
library/core/src/future/async_drop.rs
View File

@ -161,6 +161,11 @@ async unsafe fn surface_drop_in_place<T: Drop + ?Sized>(ptr: *mut T) {
/// wrapped future completes by returning `Poll::Ready(())` on poll. This
/// is useful for constructing async destructors to guarantee this
/// "fuse" property
//
// FIXME: Consider optimizing combinators to not have to use fuse in majority
// of cases, perhaps by adding `#[(rustc_)idempotent(_future)]` attribute for
// async functions and blocks with the unit return type. However current layout
// optimizations currently encode `None` case into the async block's discriminant.
struct Fuse<T> {
inner: Option<T>,
}
@ -251,6 +256,14 @@ async unsafe fn either<O: IntoFuture<Output = ()>, M: IntoFuture<Output = ()>, T
}
}
#[cfg(not(bootstrap))]
#[lang = "async_drop_deferred_drop_in_place"]
async unsafe fn deferred_drop_in_place<T>(to_drop: *mut T) {
// SAFETY: same safety requirements as with drop_in_place (implied by
// function's name)
unsafe { crate::ptr::drop_in_place(to_drop) }
}
/// Used for noop async destructors. We don't use [`core::future::Ready`]
/// because it panics after its second poll, which could be potentially
/// bad if that would happen during the cleanup.

5
src/tools/miri/tests/pass/async-drop.rs
View File

@ -1,6 +1,11 @@
//@revisions: stack tree
//@compile-flags: -Zmiri-strict-provenance
//@[tree]compile-flags: -Zmiri-tree-borrows
// WARNING: If you would ever want to modify this test,
// please consider modifying rustc's async drop test at
// `tests/ui/async-await/async-drop.rs`.
#![feature(async_drop, impl_trait_in_assoc_type, noop_waker, async_closure)]
#![allow(incomplete_features, dead_code)]

89
tests/ui/async-await/async-drop.rs
View File

@ -1,6 +1,10 @@
//@ run-pass
//@ check-run-results
// WARNING: If you would ever want to modify this test,
// please consider modifying miri's async drop test at
// `src/tools/miri/tests/pass/async-drop.rs`.
#![feature(async_drop, impl_trait_in_assoc_type, noop_waker, async_closure)]
#![allow(incomplete_features, dead_code)]
@ -13,9 +17,21 @@ use core::mem::{self, ManuallyDrop};
use core::pin::{pin, Pin};
use core::task::{Context, Poll, Waker};
async fn test_async_drop<T>(x: T) {
async fn test_async_drop<T>(x: T, _size: usize) {
let mut x = mem::MaybeUninit::new(x);
let dtor = pin!(unsafe { async_drop_in_place(x.as_mut_ptr()) });
// FIXME(zetanumbers): This check fully depends on the layout of
// the coroutine state, since async destructor combinators are just
// async functions.
#[cfg(target_pointer_width = "64")]
assert_eq!(
mem::size_of_val(&*dtor),
_size,
"sizes did not match for async destructor of type {}",
core::any::type_name::<T>(),
);
test_idempotency(dtor).await;
}
@ -36,51 +52,58 @@ fn main() {
let i = 13;
let fut = pin!(async {
test_async_drop(Int(0)).await;
test_async_drop(AsyncInt(0)).await;
test_async_drop([AsyncInt(1), AsyncInt(2)]).await;
test_async_drop((AsyncInt(3), AsyncInt(4))).await;
test_async_drop(5).await;
test_async_drop(Int(0), 0).await;
test_async_drop(AsyncInt(0), 104).await;
test_async_drop([AsyncInt(1), AsyncInt(2)], 152).await;
test_async_drop((AsyncInt(3), AsyncInt(4)), 488).await;
test_async_drop(5, 0).await;
let j = 42;
test_async_drop(&i).await;
test_async_drop(&j).await;
test_async_drop(AsyncStruct { b: AsyncInt(8), a: AsyncInt(7), i: 6 }).await;
test_async_drop(ManuallyDrop::new(AsyncInt(9))).await;
test_async_drop(&i, 0).await;
test_async_drop(&j, 0).await;
test_async_drop(AsyncStruct { b: AsyncInt(8), a: AsyncInt(7), i: 6 }, 1688).await;
test_async_drop(ManuallyDrop::new(AsyncInt(9)), 0).await;
let foo = AsyncInt(10);
test_async_drop(AsyncReference { foo: &foo }).await;
test_async_drop(AsyncReference { foo: &foo }, 104).await;
let foo = AsyncInt(11);
test_async_drop(|| {
black_box(foo);
let foo = AsyncInt(10);
foo
}).await;
test_async_drop(
|| {
black_box(foo);
let foo = AsyncInt(10);
foo
},
120,
)
.await;
test_async_drop(AsyncEnum::A(AsyncInt(12))).await;
test_async_drop(AsyncEnum::B(SyncInt(13))).await;
test_async_drop(AsyncEnum::A(AsyncInt(12)), 680).await;
test_async_drop(AsyncEnum::B(SyncInt(13)), 680).await;
test_async_drop(SyncInt(14)).await;
test_async_drop(SyncThenAsync {
i: 15,
a: AsyncInt(16),
b: SyncInt(17),
c: AsyncInt(18),
}).await;
test_async_drop(SyncInt(14), 16).await;
test_async_drop(
SyncThenAsync { i: 15, a: AsyncInt(16), b: SyncInt(17), c: AsyncInt(18) },
3064,
)
.await;
let async_drop_fut = pin!(core::future::async_drop(AsyncInt(19)));
test_idempotency(async_drop_fut).await;
let foo = AsyncInt(20);
test_async_drop(async || {
black_box(foo);
let foo = AsyncInt(19);
// Await point there, but this is async closure so it's fine
black_box(core::future::ready(())).await;
foo
}).await;
test_async_drop(
async || {
black_box(foo);
let foo = AsyncInt(19);
// Await point there, but this is async closure so it's fine
black_box(core::future::ready(())).await;
foo
},
120,
)
.await;
test_async_drop(AsyncUnion { signed: 21 }).await;
test_async_drop(AsyncUnion { signed: 21 }, 32).await;
});
let res = fut.poll(&mut cx);
assert_eq!(res, Poll::Ready(()));