Execute delayed lowering in a sandbox

compiler/rustc_data_structures/src/sharded.rs

@@ -199,6 +199,16 @@ impl<K: Eq + Hash, V> ShardedHashMap<K, V> {
             }
         }
     }
+
+    #[inline]
+    pub fn remove(&self, key: &K) {
+        let hash = make_hash(key);
+        let mut shard = self.lock_shard_by_hash(hash);
+
+        if let Entry::Occupied(e) = table_entry(&mut shard, hash, key) {
+            e.remove();
+        }
+    }
 }
 
 impl<K: Eq + Hash + Copy> ShardedHashMap<K, ()> {

compiler/rustc_data_structures/src/vec_cache.rs

@@ -206,6 +206,24 @@ impl SlotIndex {
 
         index_and_lock.store(extra.checked_add(2).unwrap(), Ordering::Release);
     }
+
+    #[inline]
+    unsafe fn remove<V>(&self, buckets: &[AtomicPtr<Slot<V>>; 21]) {
+        let bucket = &buckets[self.bucket_idx];
+        let ptr = self.bucket_ptr(bucket);
+
+        debug_assert!(self.index_in_bucket < self.bucket_idx.capacity());
+
+        // SAFETY: `bucket` was allocated (so <= isize in total bytes) to hold `entries`, so this
+        // must be inbounds.
+        let slot = unsafe { ptr.add(self.index_in_bucket) };
+
+        // SAFETY: initialized bucket has zeroed all memory within the bucket, so we are valid for
+        // AtomicU32 access.
+        let index_and_lock = unsafe { &(*slot).index_and_lock };
+
+        index_and_lock.store(0, Ordering::Release);
+    }
 }
 
 /// In-memory cache for queries whose keys are densely-numbered IDs
@@ -339,6 +357,39 @@ where
     pub fn len(&self) -> usize {
         self.len.load(Ordering::Acquire)
     }
+
+    pub fn remove(&self, key: &K) {
+        let key = u32::try_from(key.index()).unwrap();
+        let slot_idx = SlotIndex::from_index(key);
+
+        unsafe { slot_idx.remove(&self.buckets) };
+    }
+
+    pub fn invalidate(&self, selector: impl Fn(K) -> bool) {
+        let mut to_remove = vec![];
+        let mut remaining = vec![];
+
+        self.for_each(&mut |key, _, _| {
+            if selector(*key) {
+                to_remove.push(*key);
+            } else {
+                remaining.push(*key);
+            }
+        });
+
+        for key in to_remove {
+            self.remove(&key);
+        }
+
+        for (index, key) in remaining.iter().enumerate() {
+            let slot = SlotIndex::from_index(u32::try_from(index).unwrap());
+            let key = u32::try_from(key.index()).unwrap();
+
+            unsafe { slot.put_unique(&self.present, (), key) };
+        }
+
+        self.len.store(remaining.len(), Ordering::Release);
+    }
 }
 
 /// Index into an array of buckets.

compiler/rustc_hir/src/definitions.rs

@@ -7,6 +7,7 @@
 use std::fmt::{self, Write};
 use std::hash::Hash;
 
+use rustc_data_structures::indexmap::IndexSet;
 use rustc_data_structures::stable_hasher::StableHasher;
 use rustc_data_structures::unord::UnordMap;
 use rustc_hashes::Hash64;
@@ -30,6 +31,7 @@ pub struct DefPathTable {
     // We do only store the local hash, as all the definitions are from the current crate.
     def_path_hashes: IndexVec<DefIndex, Hash64>,
     def_path_hash_to_index: DefPathHashMap,
+    allow_overwrite: IndexSet<DefIndex>,
 }
 
 impl DefPathTable {
@@ -39,38 +41,45 @@ impl DefPathTable {
             index_to_key: Default::default(),
             def_path_hashes: Default::default(),
             def_path_hash_to_index: Default::default(),
+            allow_overwrite: Default::default(),
         }
     }
 
-    fn allocate(&mut self, key: DefKey, def_path_hash: DefPathHash) -> DefIndex {
+    fn allocate(&mut self, key: DefKey, def_path_hash: DefPathHash, in_sandbox: bool) -> DefIndex {
         // Assert that all DefPathHashes correctly contain the local crate's StableCrateId.
         debug_assert_eq!(self.stable_crate_id, def_path_hash.stable_crate_id());
         let local_hash = def_path_hash.local_hash();
-
-        let index = self.index_to_key.push(key);
-        debug!("DefPathTable::insert() - {key:?} <-> {index:?}");
-
-        self.def_path_hashes.push(local_hash);
-        debug_assert!(self.def_path_hashes.len() == self.index_to_key.len());
+        let index = self.index_to_key.next_index();
 
         // Check for hash collisions of DefPathHashes. These should be
         // exceedingly rare.
         if let Some(existing) = self.def_path_hash_to_index.insert(&local_hash, &index) {
-            let def_path1 = DefPath::make(LOCAL_CRATE, existing, |idx| self.def_key(idx));
-            let def_path2 = DefPath::make(LOCAL_CRATE, index, |idx| self.def_key(idx));
-
-            // Continuing with colliding DefPathHashes can lead to correctness
-            // issues. We must abort compilation.
-            //
-            // The likelihood of such a collision is very small, so actually
-            // running into one could be indicative of a poor hash function
-            // being used.
-            //
-            // See the documentation for DefPathHash for more information.
-            panic!(
-                "found DefPathHash collision between {def_path1:#?} and {def_path2:#?}. \
+            if !in_sandbox && self.allow_overwrite.swap_remove(&existing) {
+                self.def_path_hash_to_index.insert(&local_hash, &existing);
+                return existing;
+            } else {
+                let def_path1 = DefPath::make(LOCAL_CRATE, existing, |idx| self.def_key(idx));
+                let def_path2 = DefPath::make(LOCAL_CRATE, index, |idx| self.def_key(idx));
+
+                // Continuing with colliding DefPathHashes can lead to correctness
+                // issues. We must abort compilation.
+                //
+                // The likelihood of such a collision is very small, so actually
+                // running into one could be indicative of a poor hash function
+                // being used.
+                //
+                // See the documentation for DefPathHash for more information.
+                panic!(
+                    "found DefPathHash collision between {def_path1:#?} and {def_path2:#?}. \
                     Compilation cannot continue."
-            );
+                );
+            }
+        } else {
+            self.index_to_key.push(key);
+            debug!("DefPathTable::insert() - {key:?} <-> {index:?}");
+
+            self.def_path_hashes.push(local_hash);
+            debug_assert!(self.def_path_hashes.len() == self.index_to_key.len());
         }
 
         index
@@ -374,7 +383,7 @@ impl Definitions {
 
         // Create the root definition.
         let mut table = DefPathTable::new(stable_crate_id);
-        let root = LocalDefId { local_def_index: table.allocate(key, def_path_hash) };
+        let root = LocalDefId { local_def_index: table.allocate(key, def_path_hash, false) };
         assert_eq!(root.local_def_index, CRATE_DEF_INDEX);
 
         Definitions { table }
@@ -390,6 +399,7 @@ impl Definitions {
         parent: LocalDefId,
         data: DefPathData,
         disambiguator: &mut DisambiguatorState,
+        in_sandbox: bool,
     ) -> LocalDefId {
         // We can't use `Debug` implementation for `LocalDefId` here, since it tries to acquire a
         // reference to `Definitions` and we're already holding a mutable reference.
@@ -418,8 +428,14 @@ impl Definitions {
 
         debug!("create_def: after disambiguation, key = {:?}", key);
 
+        let local_def_index = self.table.allocate(key, def_path_hash, in_sandbox);
+
+        if in_sandbox {
+            assert_eq!(self.table.allow_overwrite.insert(local_def_index), true);
+        }
+
         // Create the definition.
-        LocalDefId { local_def_index: self.table.allocate(key, def_path_hash) }
+        LocalDefId { local_def_index }
     }
 
     #[inline(always)]

compiler/rustc_hir/src/intravisit.rs

@@ -226,6 +226,11 @@ pub trait Visitor<'v>: Sized {
     /// or `ControlFlow<T>`.
     type Result: VisitorResult = ();
 
+    #[inline]
+    fn visit_if_delayed(&self, _: LocalDefId) -> bool {
+        true
+    }
+
     /// If `type NestedFilter` is set to visit nested items, this method
     /// must also be overridden to provide a map to retrieve nested items.
     fn maybe_tcx(&mut self) -> Self::MaybeTyCtxt {
@@ -244,18 +249,23 @@ pub trait Visitor<'v>: Sized {
     /// this method is if you want a nested pattern but cannot supply a
     /// `TyCtxt`; see `maybe_tcx` for advice.
     fn visit_nested_item(&mut self, id: ItemId) -> Self::Result {
-        if Self::NestedFilter::INTER {
+        if self.should_visit_maybe_delayed_inter(id.owner_id.def_id) {
             let item = self.maybe_tcx().hir_item(id);
             try_visit!(self.visit_item(item));
         }
         Self::Result::output()
     }
 
+    // Now delayed owners are only delegations, which are either item, trait item or impl item.
+    fn should_visit_maybe_delayed_inter(&mut self, id: LocalDefId) -> bool {
+        Self::NestedFilter::INTER && self.visit_if_delayed(id)
+    }
+
     /// Like `visit_nested_item()`, but for trait items. See
     /// `visit_nested_item()` for advice on when to override this
     /// method.
     fn visit_nested_trait_item(&mut self, id: TraitItemId) -> Self::Result {
-        if Self::NestedFilter::INTER {
+        if self.should_visit_maybe_delayed_inter(id.owner_id.def_id) {
             let item = self.maybe_tcx().hir_trait_item(id);
             try_visit!(self.visit_trait_item(item));
         }
@@ -266,7 +276,7 @@ pub trait Visitor<'v>: Sized {
     /// `visit_nested_item()` for advice on when to override this
     /// method.
     fn visit_nested_impl_item(&mut self, id: ImplItemId) -> Self::Result {
-        if Self::NestedFilter::INTER {
+        if self.should_visit_maybe_delayed_inter(id.owner_id.def_id) {
             let item = self.maybe_tcx().hir_impl_item(id);
             try_visit!(self.visit_impl_item(item));
         }

compiler/rustc_macros/src/query.rs

@@ -138,6 +138,7 @@ struct QueryModifiers {
     // tidy-alphabetical-start
     arena_cache: Option<Ident>,
     cache_on_disk: Option<Ident>,
+    callfront: Option<Ident>,
     depth_limit: Option<Ident>,
     desc: Desc,
     eval_always: Option<Ident>,
@@ -153,6 +154,7 @@ fn parse_query_modifiers(input: ParseStream<'_>) -> Result<QueryModifiers> {
     // tidy-alphabetical-start
     let mut arena_cache = None;
     let mut cache_on_disk = None;
+    let mut callfront = None;
     let mut depth_limit = None;
     let mut desc = None;
     let mut eval_always = None;
@@ -179,6 +181,8 @@ fn parse_query_modifiers(input: ParseStream<'_>) -> Result<QueryModifiers> {
             try_insert!(arena_cache = modifier);
         } else if modifier == "cache_on_disk" {
             try_insert!(cache_on_disk = modifier);
+        } else if modifier == "callfront" {
+            try_insert!(callfront = modifier);
         } else if modifier == "depth_limit" {
             try_insert!(depth_limit = modifier);
         } else if modifier == "desc" {
@@ -211,6 +215,7 @@ fn parse_query_modifiers(input: ParseStream<'_>) -> Result<QueryModifiers> {
         // tidy-alphabetical-start
         arena_cache,
         cache_on_disk,
+        callfront,
         depth_limit,
         desc,
         eval_always,
@@ -247,6 +252,7 @@ fn make_modifiers_stream(query: &Query) -> proc_macro2::TokenStream {
         // tidy-alphabetical-start
         arena_cache,
         cache_on_disk,
+        callfront,
         depth_limit,
         desc,
         eval_always,
@@ -261,6 +267,7 @@ fn make_modifiers_stream(query: &Query) -> proc_macro2::TokenStream {
     // tidy-alphabetical-start
     let arena_cache = arena_cache.is_some();
     let cache_on_disk = cache_on_disk.is_some();
+    let callfront = callfront.is_some();
     let depth_limit = depth_limit.is_some();
     let desc = {
         // Put a description closure in the `desc` modifier.
@@ -284,7 +291,7 @@ fn make_modifiers_stream(query: &Query) -> proc_macro2::TokenStream {
     // tidy-alphabetical-end
 
     // Giving an input span to the modifier names in the modifier list seems
-    // to give slightly more helpful errors when one of the callback macros
+    // to give slightly more helpful errors when one of the callfront macros
     // fails to parse the modifier list.
     let query_name_span = query.name.span();
     quote_spanned! {
@@ -293,6 +300,7 @@ fn make_modifiers_stream(query: &Query) -> proc_macro2::TokenStream {
         // tidy-alphabetical-start
         arena_cache: #arena_cache,
         cache_on_disk: #cache_on_disk,
+        callfront: #callfront,
         depth_limit: #depth_limit,
         desc: #desc,
         eval_always: #eval_always,