Remove sync::LRef and sync::MTLockRef

With the removal of `cfg(parallel_compiler)`, these are always shared
references.

Author: Zalathar

compiler/rustc_data_structures/src/sync.rs

@@ -18,21 +18,16 @@
 //!
 //! | 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};
@@ -115,8 +110,6 @@ mod mode {
 
 // FIXME(parallel_compiler): Get rid of these aliases across the compiler.
 
-pub type LRef<'a, T> = &'a T;
-
 #[derive(Debug, Default)]
 pub struct MTLock<T>(Lock<T>);
 
@@ -151,8 +144,6 @@ impl<T> MTLock<T> {
 /// 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);

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.

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

@@ -48,7 +48,6 @@ are implemented differently depending on whether `parallel-compiler` is true.
 | -------------------------------- | --------------------------------------------------- | ------------ |
 | 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 |