A few cleanups after the removal of cfg(not(parallel))

compiler/rustc_data_structures/src/sharded.rs

@@ -43,10 +43,10 @@ impl<T> Sharded<T> {
 
     /// The shard is selected by hashing `val` with `FxHasher`.
     #[inline]
-    pub fn get_shard_by_value<K: Hash + ?Sized>(&self, _val: &K) -> &Lock<T> {
+    pub fn get_shard_by_value<K: Hash + ?Sized>(&self, val: &K) -> &Lock<T> {
         match self {
             Self::Single(single) => single,
-            Self::Shards(..) => self.get_shard_by_hash(make_hash(_val)),
+            Self::Shards(..) => self.get_shard_by_hash(make_hash(val)),
         }
     }
 
@@ -56,20 +56,20 @@ impl<T> Sharded<T> {
     }
 
     #[inline]
-    pub fn get_shard_by_index(&self, _i: usize) -> &Lock<T> {
+    pub fn get_shard_by_index(&self, i: usize) -> &Lock<T> {
         match self {
             Self::Single(single) => single,
             Self::Shards(shards) => {
                 // SAFETY: The index gets ANDed with the shard mask, ensuring it is always inbounds.
-                unsafe { &shards.get_unchecked(_i & (SHARDS - 1)).0 }
+                unsafe { &shards.get_unchecked(i & (SHARDS - 1)).0 }
             }
         }
     }
 
     /// The shard is selected by hashing `val` with `FxHasher`.
     #[inline]
     #[track_caller]
-    pub fn lock_shard_by_value<K: Hash + ?Sized>(&self, _val: &K) -> LockGuard<'_, T> {
+    pub fn lock_shard_by_value<K: Hash + ?Sized>(&self, val: &K) -> LockGuard<'_, T> {
         match self {
             Self::Single(single) => {
                 // Synchronization is disabled so use the `lock_assume_no_sync` method optimized
@@ -79,7 +79,7 @@ impl<T> Sharded<T> {
                 // `might_be_dyn_thread_safe` was also false.
                 unsafe { single.lock_assume(Mode::NoSync) }
             }
-            Self::Shards(..) => self.lock_shard_by_hash(make_hash(_val)),
+            Self::Shards(..) => self.lock_shard_by_hash(make_hash(val)),
         }
     }
 
@@ -91,7 +91,7 @@ impl<T> Sharded<T> {
 
     #[inline]
     #[track_caller]
-    pub fn lock_shard_by_index(&self, _i: usize) -> LockGuard<'_, T> {
+    pub fn lock_shard_by_index(&self, i: usize) -> LockGuard<'_, T> {
         match self {
             Self::Single(single) => {
                 // Synchronization is disabled so use the `lock_assume_no_sync` method optimized
@@ -109,7 +109,7 @@ impl<T> Sharded<T> {
                 // always inbounds.
                 // SAFETY (lock_assume_sync): We know `is_dyn_thread_safe` was true when creating
                 // the lock thus `might_be_dyn_thread_safe` was also true.
-                unsafe { shards.get_unchecked(_i & (SHARDS - 1)).0.lock_assume(Mode::Sync) }
+                unsafe { shards.get_unchecked(i & (SHARDS - 1)).0.lock_assume(Mode::Sync) }
             }
         }
     }

compiler/rustc_data_structures/src/sync.rs

@@ -18,42 +18,54 @@
 //!
 //! | Type                    | Serial version      | Parallel version                |
 //! | ----------------------- | ------------------- | ------------------------------- |
-//! | `LRef<'a, T>` [^2]      | `&'a mut T`         | `&'a T`                         |
-//! |                         |                     |                                 |
 //! | `Lock<T>`               | `RefCell<T>`        | `RefCell<T>` or                 |
 //! |                         |                     | `parking_lot::Mutex<T>`         |
 //! | `RwLock<T>`             | `RefCell<T>`        | `parking_lot::RwLock<T>`        |
 //! | `MTLock<T>`        [^1] | `T`                 | `Lock<T>`                       |
-//! | `MTLockRef<'a, T>` [^2] | `&'a mut MTLock<T>` | `&'a MTLock<T>`                 |
 //! |                         |                     |                                 |
 //! | `ParallelIterator`      | `Iterator`          | `rayon::iter::ParallelIterator` |
 //!
 //! [^1]: `MTLock` is similar to `Lock`, but the serial version avoids the cost
 //! of a `RefCell`. This is appropriate when interior mutability is not
 //! required.
-//!
-//! [^2]: `MTRef`, `MTLockRef` are type aliases.
 
 use std::collections::HashMap;
 use std::hash::{BuildHasher, Hash};
 
-pub use crate::marker::*;
+pub use parking_lot::{
+    MappedRwLockReadGuard as MappedReadGuard, MappedRwLockWriteGuard as MappedWriteGuard,
+    RwLockReadGuard as ReadGuard, RwLockWriteGuard as WriteGuard,
+};
 
-mod lock;
+pub use self::atomic::AtomicU64;
+pub use self::freeze::{FreezeLock, FreezeReadGuard, FreezeWriteGuard};
 #[doc(no_inline)]
-pub use lock::{Lock, LockGuard, Mode};
-
-mod worker_local;
-pub use worker_local::{Registry, WorkerLocal};
+pub use self::lock::{Lock, LockGuard, Mode};
+pub use self::mode::{is_dyn_thread_safe, set_dyn_thread_safe_mode};
+pub use self::parallel::{
+    join, par_for_each_in, par_map, parallel_guard, scope, try_par_for_each_in,
+};
+pub use self::vec::{AppendOnlyIndexVec, AppendOnlyVec};
+pub use self::worker_local::{Registry, WorkerLocal};
+pub use crate::marker::*;
 
+mod freeze;
+mod lock;
 mod parallel;
-pub use parallel::{join, par_for_each_in, par_map, parallel_guard, scope, try_par_for_each_in};
-pub use vec::{AppendOnlyIndexVec, AppendOnlyVec};
-
 mod vec;
+mod worker_local;
 
-mod freeze;
-pub use freeze::{FreezeLock, FreezeReadGuard, FreezeWriteGuard};
+/// Keep the conditional imports together in a submodule, so that import-sorting
+/// doesn't split them up.
+mod atomic {
+    // Most hosts can just use a regular AtomicU64.
+    #[cfg(target_has_atomic = "64")]
+    pub use std::sync::atomic::AtomicU64;
+
+    // Some 32-bit hosts don't have AtomicU64, so use a fallback.
+    #[cfg(not(target_has_atomic = "64"))]
+    pub use portable_atomic::AtomicU64;
+}
 
 mod mode {
     use std::sync::atomic::{AtomicU8, Ordering};
@@ -97,21 +109,6 @@ mod mode {
 
 // FIXME(parallel_compiler): Get rid of these aliases across the compiler.
 
-pub use std::sync::OnceLock;
-// Use portable AtomicU64 for targets without native 64-bit atomics
-#[cfg(target_has_atomic = "64")]
-pub use std::sync::atomic::AtomicU64;
-
-pub use mode::{is_dyn_thread_safe, set_dyn_thread_safe_mode};
-pub use parking_lot::{
-    MappedRwLockReadGuard as MappedReadGuard, MappedRwLockWriteGuard as MappedWriteGuard,
-    RwLockReadGuard as ReadGuard, RwLockWriteGuard as WriteGuard,
-};
-#[cfg(not(target_has_atomic = "64"))]
-pub use portable_atomic::AtomicU64;
-
-pub type LRef<'a, T> = &'a T;
-
 #[derive(Debug, Default)]
 pub struct MTLock<T>(Lock<T>);
 
@@ -142,14 +139,10 @@ impl<T> MTLock<T> {
     }
 }
 
-use parking_lot::RwLock as InnerRwLock;
-
 /// This makes locks panic if they are already held.
 /// It is only useful when you are running in a single thread
 const ERROR_CHECKING: bool = false;
 
-pub type MTLockRef<'a, T> = LRef<'a, MTLock<T>>;
-
 #[derive(Default)]
 #[repr(align(64))]
 pub struct CacheAligned<T>(pub T);
@@ -167,12 +160,12 @@ impl<K: Eq + Hash, V: Eq, S: BuildHasher> HashMapExt<K, V> for HashMap<K, V, S>
 }
 
 #[derive(Debug, Default)]
-pub struct RwLock<T>(InnerRwLock<T>);
+pub struct RwLock<T>(parking_lot::RwLock<T>);
 
 impl<T> RwLock<T> {
     #[inline(always)]
     pub fn new(inner: T) -> Self {
-        RwLock(InnerRwLock::new(inner))
+        RwLock(parking_lot::RwLock::new(inner))
     }
 
     #[inline(always)]

compiler/rustc_interface/src/passes.rs

@@ -2,14 +2,14 @@ use std::any::Any;
 use std::ffi::OsString;
 use std::io::{self, BufWriter, Write};
 use std::path::{Path, PathBuf};
-use std::sync::{Arc, LazyLock};
+use std::sync::{Arc, LazyLock, OnceLock};
 use std::{env, fs, iter};
 
 use rustc_ast as ast;
 use rustc_codegen_ssa::traits::CodegenBackend;
 use rustc_data_structures::parallel;
 use rustc_data_structures::steal::Steal;
-use rustc_data_structures::sync::{AppendOnlyIndexVec, FreezeLock, OnceLock, WorkerLocal};
+use rustc_data_structures::sync::{AppendOnlyIndexVec, FreezeLock, WorkerLocal};
 use rustc_expand::base::{ExtCtxt, LintStoreExpand};
 use rustc_feature::Features;
 use rustc_fs_util::try_canonicalize;

compiler/rustc_metadata/src/rmeta/decoder.rs

@@ -2,7 +2,7 @@
 
 use std::iter::TrustedLen;
 use std::path::Path;
-use std::sync::Arc;
+use std::sync::{Arc, OnceLock};
 use std::{io, iter, mem};
 
 pub(super) use cstore_impl::provide;
@@ -11,7 +11,7 @@ use rustc_ast as ast;
 use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_data_structures::owned_slice::OwnedSlice;
-use rustc_data_structures::sync::{Lock, OnceLock};
+use rustc_data_structures::sync::Lock;
 use rustc_data_structures::unhash::UnhashMap;
 use rustc_expand::base::{SyntaxExtension, SyntaxExtensionKind};
 use rustc_expand::proc_macro::{AttrProcMacro, BangProcMacro, DeriveProcMacro};

compiler/rustc_middle/src/mir/basic_blocks.rs

@@ -1,8 +1,9 @@
+use std::sync::OnceLock;
+
 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::OnceLock;
 use rustc_index::{IndexSlice, IndexVec};
 use rustc_macros::{HashStable, TyDecodable, TyEncodable, TypeFoldable, TypeVisitable};
 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};

compiler/rustc_monomorphize/src/collector.rs

@@ -209,7 +209,7 @@ use std::path::PathBuf;
 
 use rustc_attr_parsing::InlineAttr;
 use rustc_data_structures::fx::FxIndexMap;
-use rustc_data_structures::sync::{LRef, MTLock, par_for_each_in};
+use rustc_data_structures::sync::{MTLock, par_for_each_in};
 use rustc_data_structures::unord::{UnordMap, UnordSet};
 use rustc_hir as hir;
 use rustc_hir::def::DefKind;
@@ -357,7 +357,7 @@ impl<'tcx> Extend<Spanned<MonoItem<'tcx>>> for MonoItems<'tcx> {
 fn collect_items_rec<'tcx>(
     tcx: TyCtxt<'tcx>,
     starting_item: Spanned<MonoItem<'tcx>>,
-    state: LRef<'_, SharedState<'tcx>>,
+    state: &SharedState<'tcx>,
     recursion_depths: &mut DefIdMap<usize>,
     recursion_limit: Limit,
     mode: CollectionMode,
@@ -1671,30 +1671,26 @@ pub(crate) fn collect_crate_mono_items<'tcx>(
 
     debug!("building mono item graph, beginning at roots");
 
-    let mut state = SharedState {
+    let state = SharedState {
         visited: MTLock::new(UnordSet::default()),
         mentioned: MTLock::new(UnordSet::default()),
         usage_map: MTLock::new(UsageMap::new()),
     };
     let recursion_limit = tcx.recursion_limit();
 
-    {
-        let state: LRef<'_, _> = &mut state;
-
-        tcx.sess.time("monomorphization_collector_graph_walk", || {
-            par_for_each_in(roots, |root| {
-                let mut recursion_depths = DefIdMap::default();
-                collect_items_rec(
-                    tcx,
-                    dummy_spanned(root),
-                    state,
-                    &mut recursion_depths,
-                    recursion_limit,
-                    CollectionMode::UsedItems,
-                );
-            });
+    tcx.sess.time("monomorphization_collector_graph_walk", || {
+        par_for_each_in(roots, |root| {
+            let mut recursion_depths = DefIdMap::default();
+            collect_items_rec(
+                tcx,
+                dummy_spanned(root),
+                &state,
+                &mut recursion_depths,
+                recursion_limit,
+                CollectionMode::UsedItems,
+            );
         });
-    }
+    });
 
     // The set of MonoItems was created in an inherently indeterministic order because
     // of parallelism. We sort it here to ensure that the output is deterministic.

compiler/rustc_query_system/src/query/caches.rs

@@ -1,9 +1,9 @@
 use std::fmt::Debug;
 use std::hash::Hash;
+use std::sync::OnceLock;
 
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sharded::{self, Sharded};
-use rustc_data_structures::sync::OnceLock;
 pub use rustc_data_structures::vec_cache::VecCache;
 use rustc_hir::def_id::LOCAL_CRATE;
 use rustc_index::Idx;

src/doc/rustc-dev-guide/src/parallel-rustc.md

@@ -46,10 +46,8 @@ are implemented differently depending on whether `parallel-compiler` is true.
 
 | data structure                   | parallel                                            | non-parallel |
 | -------------------------------- | --------------------------------------------------- | ------------ |
-| OnceCell                         | std::sync::OnceLock                                 | std::cell::OnceCell |
 | Lock\<T> | (parking_lot::Mutex\<T>) | (std::cell::RefCell) |
 | RwLock\<T> | (parking_lot::RwLock\<T>) | (std::cell::RefCell) |
-| MTRef<'a, T> | &'a T | &'a mut T |
 | MTLock\<T> | (Lock\<T>) | (T) |
 | ReadGuard | parking_lot::RwLockReadGuard | std::cell::Ref |
 | MappedReadGuard | parking_lot::MappedRwLockReadGuard | std::cell::Ref |

src/tools/clippy/clippy_utils/src/macros.rs

@@ -1,14 +1,13 @@
 #![allow(clippy::similar_names)] // `expr` and `expn`
 
-use std::sync::Arc;
+use std::sync::{Arc, OnceLock};
 
 use crate::get_unique_attr;
 use crate::visitors::{Descend, for_each_expr_without_closures};
 
 use arrayvec::ArrayVec;
 use rustc_ast::{FormatArgs, FormatArgument, FormatPlaceholder};
 use rustc_data_structures::fx::FxHashMap;
-use rustc_data_structures::sync::OnceLock;
 use rustc_hir::{self as hir, Expr, ExprKind, HirId, Node, QPath};
 use rustc_lint::{LateContext, LintContext};
 use rustc_span::def_id::DefId;