diff options
Diffstat (limited to 'compiler/rustc_data_structures/src')
| -rw-r--r-- | compiler/rustc_data_structures/src/sync.rs | 53 |
1 files changed, 39 insertions, 14 deletions
diff --git a/compiler/rustc_data_structures/src/sync.rs b/compiler/rustc_data_structures/src/sync.rs index 31323c21df0..09765607cbd 100644 --- a/compiler/rustc_data_structures/src/sync.rs +++ b/compiler/rustc_data_structures/src/sync.rs @@ -1,21 +1,46 @@ -//! This module defines types which are thread safe if cfg!(parallel_compiler) is true. +//! This module defines various operations and types that are implemented in +//! one way for the serial compiler, and another way the parallel compiler. //! -//! `Lrc` is an alias of `Arc` if cfg!(parallel_compiler) is true, `Rc` otherwise. +//! Operations +//! ---------- +//! The parallel versions of operations use Rayon to execute code in parallel, +//! while the serial versions degenerate straightforwardly to serial execution. +//! The operations include `join`, `parallel`, `par_iter`, and `par_for_each`. //! -//! `Lock` is a mutex. -//! It internally uses `parking_lot::Mutex` if cfg!(parallel_compiler) is true, -//! `RefCell` otherwise. +//! `rustc_erase_owner!` erases an `OwningRef` owner into `Erased` for the +//! serial version and `Erased + Send + Sync` for the parallel version. //! -//! `RwLock` is a read-write lock. -//! It internally uses `parking_lot::RwLock` if cfg!(parallel_compiler) is true, -//! `RefCell` otherwise. +//! Types +//! ----- +//! The parallel versions of types provide various kinds of synchronization, +//! while the serial compiler versions do not. //! -//! `MTLock` is a mutex which disappears if cfg!(parallel_compiler) is false. +//! The following table shows how the types are implemented internally. Except +//! where noted otherwise, the type in column one is defined as a +//! newtype around the type from column two or three. //! -//! `MTRef` is an immutable reference if cfg!(parallel_compiler), and a mutable reference otherwise. +//! | Type | Serial version | Parallel version | +//! | ----------------------- | ------------------- | ------------------------------- | +//! | `Lrc<T>` | `rc::Rc<T>` | `sync::Arc<T>` | +//! |` Weak<T>` | `rc::Weak<T>` | `sync::Weak<T>` | +//! | | | | +//! | `AtomicBool` | `Cell<bool>` | `atomic::AtomicBool` | +//! | `AtomicU32` | `Cell<u32>` | `atomic::AtomicU32` | +//! | `AtomicU64` | `Cell<u64>` | `atomic::AtomicU64` | +//! | `AtomicUsize` | `Cell<usize>` | `atomic::AtomicUsize` | +//! | | | | +//! | `Lock<T>` | `RefCell<T>` | `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` | //! -//! `rustc_erase_owner!` erases an OwningRef owner into Erased or Erased + Send + Sync -//! depending on the value of cfg!(parallel_compiler). +//! [^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] `MTLockRef` is a typedef. use crate::owning_ref::{Erased, OwningRef}; use std::collections::HashMap; @@ -209,7 +234,7 @@ cfg_if! { } } - pub type MTRef<'a, T> = &'a mut T; + pub type MTLockRef<'a, T> = &'a mut MTLock<T>; #[derive(Debug, Default)] pub struct MTLock<T>(T); @@ -267,7 +292,7 @@ cfg_if! { pub use std::sync::Arc as Lrc; pub use std::sync::Weak as Weak; - pub type MTRef<'a, T> = &'a T; + pub type MTLockRef<'a, T> = &'a MTLock<T>; #[derive(Debug, Default)] pub struct MTLock<T>(Lock<T>); |