Auto merge of rust-lang#115422 - Zoxc:cache-once-lock, r=cjgillot

Use `OnceLock` for `SingleCache`

This uses `OnceLock` for `SingleCache` instead of `Lock<Option<T>>` so lookups are lock-free.

r? `@cjgillot`

compiler/rustc_data_structures/src/sync.rs

@@ -273,7 +273,7 @@ cfg_if! {
         pub use std::cell::RefMut as MappedWriteGuard;
         pub use std::cell::RefMut as MappedLockGuard;
 
-        pub use std::cell::OnceCell;
+        pub use std::cell::OnceCell as OnceLock;
 
         use std::cell::RefCell as InnerRwLock;
 
@@ -327,7 +327,7 @@ cfg_if! {
 
         pub use parking_lot::MappedMutexGuard as MappedLockGuard;
 
-        pub use std::sync::OnceLock as OnceCell;
+        pub use std::sync::OnceLock;
 
         pub use std::sync::atomic::{AtomicBool, AtomicUsize, AtomicU32, AtomicU64};
 

compiler/rustc_interface/src/passes.rs

@@ -8,7 +8,7 @@ use rustc_borrowck as mir_borrowck;
 use rustc_codegen_ssa::traits::CodegenBackend;
 use rustc_data_structures::parallel;
 use rustc_data_structures::steal::Steal;
-use rustc_data_structures::sync::{Lrc, OnceCell, WorkerLocal};
+use rustc_data_structures::sync::{Lrc, OnceLock, WorkerLocal};
 use rustc_errors::PResult;
 use rustc_expand::base::{ExtCtxt, LintStoreExpand};
 use rustc_feature::Features;
@@ -689,7 +689,7 @@ pub fn create_global_ctxt<'tcx>(
     lint_store: Lrc<LintStore>,
     dep_graph: DepGraph,
     untracked: Untracked,
-    gcx_cell: &'tcx OnceCell<GlobalCtxt<'tcx>>,
+    gcx_cell: &'tcx OnceLock<GlobalCtxt<'tcx>>,
     arena: &'tcx WorkerLocal<Arena<'tcx>>,
     hir_arena: &'tcx WorkerLocal<rustc_hir::Arena<'tcx>>,
 ) -> &'tcx GlobalCtxt<'tcx> {

compiler/rustc_interface/src/queries.rs

@@ -7,7 +7,7 @@ use rustc_codegen_ssa::traits::CodegenBackend;
 use rustc_codegen_ssa::CodegenResults;
 use rustc_data_structures::steal::Steal;
 use rustc_data_structures::svh::Svh;
-use rustc_data_structures::sync::{AppendOnlyIndexVec, Lrc, OnceCell, RwLock, WorkerLocal};
+use rustc_data_structures::sync::{AppendOnlyIndexVec, Lrc, OnceLock, RwLock, WorkerLocal};
 use rustc_hir::def_id::{StableCrateId, CRATE_DEF_ID, LOCAL_CRATE};
 use rustc_hir::definitions::Definitions;
 use rustc_incremental::DepGraphFuture;
@@ -78,7 +78,7 @@ impl<T> Default for Query<T> {
 
 pub struct Queries<'tcx> {
     compiler: &'tcx Compiler,
-    gcx_cell: OnceCell<GlobalCtxt<'tcx>>,
+    gcx_cell: OnceLock<GlobalCtxt<'tcx>>,
 
     arena: WorkerLocal<Arena<'tcx>>,
     hir_arena: WorkerLocal<rustc_hir::Arena<'tcx>>,
@@ -93,7 +93,7 @@ impl<'tcx> Queries<'tcx> {
     pub fn new(compiler: &'tcx Compiler) -> Queries<'tcx> {
         Queries {
             compiler,
-            gcx_cell: OnceCell::new(),
+            gcx_cell: OnceLock::new(),
             arena: WorkerLocal::new(|_| Arena::default()),
             hir_arena: WorkerLocal::new(|_| rustc_hir::Arena::default()),
             parse: Default::default(),

compiler/rustc_metadata/src/rmeta/decoder.rs

@@ -9,7 +9,7 @@ use rustc_data_structures::captures::Captures;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::owned_slice::OwnedSlice;
 use rustc_data_structures::svh::Svh;
-use rustc_data_structures::sync::{AppendOnlyVec, AtomicBool, Lock, Lrc, OnceCell};
+use rustc_data_structures::sync::{AppendOnlyVec, AtomicBool, Lock, Lrc, OnceLock};
 use rustc_data_structures::unhash::UnhashMap;
 use rustc_expand::base::{SyntaxExtension, SyntaxExtensionKind};
 use rustc_expand::proc_macro::{AttrProcMacro, BangProcMacro, DeriveProcMacro};
@@ -93,7 +93,7 @@ pub(crate) struct CrateMetadata {
     /// For every definition in this crate, maps its `DefPathHash` to its `DefIndex`.
     def_path_hash_map: DefPathHashMapRef<'static>,
     /// Likewise for ExpnHash.
-    expn_hash_map: OnceCell<UnhashMap<ExpnHash, ExpnIndex>>,
+    expn_hash_map: OnceLock<UnhashMap<ExpnHash, ExpnIndex>>,
     /// Used for decoding interpret::AllocIds in a cached & thread-safe manner.
     alloc_decoding_state: AllocDecodingState,
     /// Caches decoded `DefKey`s.

compiler/rustc_middle/src/mir/basic_blocks.rs

@@ -5,7 +5,7 @@ use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::graph;
 use rustc_data_structures::graph::dominators::{dominators, Dominators};
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
-use rustc_data_structures::sync::OnceCell;
+use rustc_data_structures::sync::OnceLock;
 use rustc_index::{IndexSlice, IndexVec};
 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
 use smallvec::SmallVec;
@@ -23,11 +23,11 @@ pub type SwitchSources = FxHashMap<(BasicBlock, BasicBlock), SmallVec<[Option<u1
 
 #[derive(Clone, Default, Debug)]
 struct Cache {
-    predecessors: OnceCell<Predecessors>,
-    switch_sources: OnceCell<SwitchSources>,
-    is_cyclic: OnceCell<bool>,
-    reverse_postorder: OnceCell<Vec<BasicBlock>>,
-    dominators: OnceCell<Dominators<BasicBlock>>,
+    predecessors: OnceLock<Predecessors>,
+    switch_sources: OnceLock<SwitchSources>,
+    is_cyclic: OnceLock<bool>,
+    reverse_postorder: OnceLock<Vec<BasicBlock>>,
+    dominators: OnceLock<Dominators<BasicBlock>>,
 }
 
 impl<'tcx> BasicBlocks<'tcx> {

compiler/rustc_query_system/src/query/caches.rs

@@ -2,7 +2,7 @@ use crate::dep_graph::DepNodeIndex;
 
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sharded::{self, Sharded};
-use rustc_data_structures::sync::Lock;
+use rustc_data_structures::sync::OnceLock;
 use rustc_index::{Idx, IndexVec};
 use std::fmt::Debug;
 use std::hash::Hash;
@@ -87,12 +87,12 @@ impl<'tcx, V: 'tcx> CacheSelector<'tcx, V> for SingleCacheSelector {
 }
 
 pub struct SingleCache<V> {
-    cache: Lock<Option<(V, DepNodeIndex)>>,
+    cache: OnceLock<(V, DepNodeIndex)>,
 }
 
 impl<V> Default for SingleCache<V> {
     fn default() -> Self {
-        SingleCache { cache: Lock::new(None) }
+        SingleCache { cache: OnceLock::new() }
     }
 }
 
@@ -105,16 +105,16 @@ where
 
     #[inline(always)]
     fn lookup(&self, _key: &()) -> Option<(V, DepNodeIndex)> {
-        *self.cache.lock()
+        self.cache.get().copied()
     }
 
     #[inline]
     fn complete(&self, _key: (), value: V, index: DepNodeIndex) {
-        *self.cache.lock() = Some((value, index));
+        self.cache.set((value, index)).ok();
     }
 
     fn iter(&self, f: &mut dyn FnMut(&Self::Key, &Self::Value, DepNodeIndex)) {
-        if let Some(value) = self.cache.lock().as_ref() {
+        if let Some(value) = self.cache.get() {
             f(&(), &value.0, value.1)
         }
     }