Replace LockCell with atomic types

src/librustc/session/mod.rs

@@ -16,7 +16,10 @@ use util::common::{duration_to_secs_str, ErrorReported};
 use util::common::ProfileQueriesMsg;
 
 use rustc_data_structures::base_n;
-use rustc_data_structures::sync::{self, Lrc, Lock, LockCell, OneThread, Once, RwLock};
+use rustc_data_structures::sync::{
+    self, Lrc, Lock, OneThread, Once, RwLock, AtomicU64, AtomicUsize, AtomicBool, Ordering,
+    Ordering::SeqCst,
+};
 
 use errors::{self, DiagnosticBuilder, DiagnosticId, Applicability};
 use errors::emitter::{Emitter, EmitterWriter};
@@ -41,7 +44,6 @@ use std::io::Write;
 use std::path::PathBuf;
 use std::time::Duration;
 use std::sync::mpsc;
-use std::sync::atomic::{AtomicUsize, Ordering};
 
 mod code_stats;
 pub mod config;
@@ -138,15 +140,15 @@ pub struct Session {
     /// If -zfuel=crate=n is specified, Some(crate).
     optimization_fuel_crate: Option<String>,
     /// If -zfuel=crate=n is specified, initially set to n. Otherwise 0.
-    optimization_fuel_limit: LockCell<u64>,
+    optimization_fuel_limit: AtomicU64,
     /// We're rejecting all further optimizations.
-    out_of_fuel: LockCell<bool>,
+    out_of_fuel: AtomicBool,
 
     // The next two are public because the driver needs to read them.
     /// If -zprint-fuel=crate, Some(crate).
     pub print_fuel_crate: Option<String>,
     /// Always set to zero and incremented so that we can print fuel expended by a crate.
-    pub print_fuel: LockCell<u64>,
+    pub print_fuel: AtomicU64,
 
     /// Loaded up early on in the initialization of this `Session` to avoid
     /// false positives about a job server in our environment.
@@ -857,32 +859,43 @@ impl Session {
                  self.perf_stats.normalize_projection_ty.load(Ordering::Relaxed));
     }
 
-    /// We want to know if we're allowed to do an optimization for crate foo from -z fuel=foo=n.
-    /// This expends fuel if applicable, and records fuel if applicable.
-    pub fn consider_optimizing<T: Fn() -> String>(&self, crate_name: &str, msg: T) -> bool {
+    #[inline(never)]
+    #[cold]
+    pub fn consider_optimizing_cold<T: Fn() -> String>(&self, crate_name: &str, msg: T) -> bool {
         let mut ret = true;
         if let Some(ref c) = self.optimization_fuel_crate {
             if c == crate_name {
                 assert_eq!(self.query_threads(), 1);
-                let fuel = self.optimization_fuel_limit.get();
+                let fuel = self.optimization_fuel_limit.load(SeqCst);
                 ret = fuel != 0;
-                if fuel == 0 && !self.out_of_fuel.get() {
+                if fuel == 0 && !self.out_of_fuel.load(SeqCst) {
                     eprintln!("optimization-fuel-exhausted: {}", msg());
-                    self.out_of_fuel.set(true);
+                    self.out_of_fuel.store(true, SeqCst);
                 } else if fuel > 0 {
-                    self.optimization_fuel_limit.set(fuel - 1);
+                    self.optimization_fuel_limit.store(fuel - 1, SeqCst);
                 }
             }
         }
         if let Some(ref c) = self.print_fuel_crate {
             if c == crate_name {
                 assert_eq!(self.query_threads(), 1);
-                self.print_fuel.set(self.print_fuel.get() + 1);
+                self.print_fuel.store(self.print_fuel.load(SeqCst) + 1, SeqCst);
             }
         }
         ret
     }
 
+    /// We want to know if we're allowed to do an optimization for crate foo from -z fuel=foo=n.
+    /// This expends fuel if applicable, and records fuel if applicable.
+    #[inline(always)]
+    pub fn consider_optimizing<T: Fn() -> String>(&self, crate_name: &str, msg: T) -> bool {
+        if likely!(self.optimization_fuel_crate.is_none() && self.print_fuel_crate.is_none()) {
+            true
+        } else {
+            self.consider_optimizing_cold(crate_name, msg)
+        }
+    }
+
     /// Returns the number of query threads that should be used for this
     /// compilation
     pub fn query_threads_from_opts(opts: &config::Options) -> usize {
@@ -1128,9 +1141,9 @@ pub fn build_session_(
 
     let optimization_fuel_crate = sopts.debugging_opts.fuel.as_ref().map(|i| i.0.clone());
     let optimization_fuel_limit =
-        LockCell::new(sopts.debugging_opts.fuel.as_ref().map(|i| i.1).unwrap_or(0));
+        AtomicU64::new(sopts.debugging_opts.fuel.as_ref().map(|i| i.1).unwrap_or(0));
     let print_fuel_crate = sopts.debugging_opts.print_fuel.clone();
-    let print_fuel = LockCell::new(0);
+    let print_fuel = AtomicU64::new(0);
 
     let working_dir = env::current_dir().unwrap_or_else(|e|
         p_s.span_diagnostic
@@ -1195,7 +1208,7 @@ pub fn build_session_(
         optimization_fuel_limit,
         print_fuel_crate,
         print_fuel,
-        out_of_fuel: LockCell::new(false),
+        out_of_fuel: AtomicBool::new(false),
         // Note that this is unsafe because it may misinterpret file descriptors
         // on Unix as jobserver file descriptors. We hopefully execute this near
         // the beginning of the process though to ensure we don't get false

src/librustc_data_structures/lib.rs

@@ -21,6 +21,7 @@
 #![feature(hash_raw_entry)]
 #![feature(stmt_expr_attributes)]
 #![feature(core_intrinsics)]
+#![feature(integer_atomics)]
 
 #![cfg_attr(unix, feature(libc))]
 #![cfg_attr(test, feature(test))]

src/librustc_data_structures/sync.rs

@@ -10,10 +10,6 @@
 //! It internally uses `parking_lot::RwLock` if cfg!(parallel_queries) is true,
 //! `RefCell` otherwise.
 //!
-//! `LockCell` is a thread safe version of `Cell`, with `set` and `get` operations.
-//! It can never deadlock. It uses `Cell` when
-//! cfg!(parallel_queries) is false, otherwise it is a `Lock`.
-//!
 //! `MTLock` is a mutex which disappears if cfg!(parallel_queries) is false.
 //!
 //! `MTRef` is a immutable reference if cfg!(parallel_queries), and an mutable reference otherwise.
@@ -23,11 +19,7 @@
 
 use std::collections::HashMap;
 use std::hash::{Hash, BuildHasher};
-use std::cmp::Ordering;
 use std::marker::PhantomData;
-use std::fmt::Debug;
-use std::fmt::Formatter;
-use std::fmt;
 use std::ops::{Deref, DerefMut};
 use owning_ref::{Erased, OwningRef};
 
@@ -54,6 +46,9 @@ pub fn serial_scope<F, R>(f: F) -> R
     f(&SerialScope)
 }
 
+pub use std::sync::atomic::Ordering::SeqCst;
+pub use std::sync::atomic::Ordering;
+
 cfg_if! {
     if #[cfg(not(parallel_queries))] {
         pub auto trait Send {}
@@ -69,6 +64,62 @@ cfg_if! {
             }
         }
 
+        use std::ops::Add;
+
+        #[derive(Debug)]
+        pub struct Atomic<T: Copy>(Cell<T>);
+
+        impl<T: Copy> Atomic<T> {
+            pub fn new(v: T) -> Self {
+                Atomic(Cell::new(v))
+            }
+        }
+
+        impl<T: Copy + PartialEq> Atomic<T> {
+            pub fn into_inner(self) -> T {
+                self.0.into_inner()
+            }
+
+            pub fn load(&self, _: Ordering) -> T {
+                self.0.get()
+            }
+
+            pub fn store(&self, val: T, _: Ordering) {
+                self.0.set(val)
+            }
+
+            pub fn swap(&self, val: T, _: Ordering) -> T {
+                self.0.replace(val)
+            }
+
+            pub fn compare_exchange(&self,
+                                    current: T,
+                                    new: T,
+                                    _: Ordering,
+                                    _: Ordering)
+                                    -> Result<T, T> {
+                let read = self.0.get();
+                if read == current {
+                    self.0.set(new);
+                    Ok(read)
+                } else {
+                    Err(read)
+                }
+            }
+        }
+
+        impl<T: Add<Output=T> + Copy> Atomic<T> {
+            pub fn fetch_add(&self, val: T, _: Ordering) -> T {
+                let old = self.0.get();
+                self.0.set(old + val);
+                old
+            }
+        }
+
+        pub type AtomicUsize = Atomic<usize>;
+        pub type AtomicBool = Atomic<bool>;
+        pub type AtomicU64 = Atomic<u64>;
+
         pub use self::serial_join as join;
         pub use self::serial_scope as scope;
 
@@ -160,47 +211,6 @@ cfg_if! {
                 MTLock(self.0.clone())
             }
         }
-
-        pub struct LockCell<T>(Cell<T>);
-
-        impl<T> LockCell<T> {
-            #[inline(always)]
-            pub fn new(inner: T) -> Self {
-                LockCell(Cell::new(inner))
-            }
-
-            #[inline(always)]
-            pub fn into_inner(self) -> T {
-                self.0.into_inner()
-            }
-
-            #[inline(always)]
-            pub fn set(&self, new_inner: T) {
-                self.0.set(new_inner);
-            }
-
-            #[inline(always)]
-            pub fn get(&self) -> T where T: Copy {
-                self.0.get()
-            }
-
-            #[inline(always)]
-            pub fn set_mut(&mut self, new_inner: T) {
-                self.0.set(new_inner);
-            }
-
-            #[inline(always)]
-            pub fn get_mut(&mut self) -> T where T: Copy {
-                self.0.get()
-            }
-        }
-
-        impl<T> LockCell<Option<T>> {
-            #[inline(always)]
-            pub fn take(&self) -> Option<T> {
-                unsafe { (*self.0.as_ptr()).take() }
-            }
-        }
     } else {
         pub use std::marker::Send as Send;
         pub use std::marker::Sync as Sync;
@@ -213,6 +223,8 @@ cfg_if! {
         pub use parking_lot::MutexGuard as LockGuard;
         pub use parking_lot::MappedMutexGuard as MappedLockGuard;
 
+        pub use std::sync::atomic::{AtomicBool, AtomicUsize, AtomicU64};
+
         pub use std::sync::Arc as Lrc;
         pub use std::sync::Weak as Weak;
 
@@ -278,47 +290,6 @@ cfg_if! {
                 v.erase_send_sync_owner()
             }}
         }
-
-        pub struct LockCell<T>(Lock<T>);
-
-        impl<T> LockCell<T> {
-            #[inline(always)]
-            pub fn new(inner: T) -> Self {
-                LockCell(Lock::new(inner))
-            }
-
-            #[inline(always)]
-            pub fn into_inner(self) -> T {
-                self.0.into_inner()
-            }
-
-            #[inline(always)]
-            pub fn set(&self, new_inner: T) {
-                *self.0.lock() = new_inner;
-            }
-
-            #[inline(always)]
-            pub fn get(&self) -> T where T: Copy {
-                *self.0.lock()
-            }
-
-            #[inline(always)]
-            pub fn set_mut(&mut self, new_inner: T) {
-                *self.0.get_mut() = new_inner;
-            }
-
-            #[inline(always)]
-            pub fn get_mut(&mut self) -> T where T: Copy {
-                *self.0.get_mut()
-            }
-        }
-
-        impl<T> LockCell<Option<T>> {
-            #[inline(always)]
-            pub fn take(&self) -> Option<T> {
-                self.0.lock().take()
-            }
-        }
     }
 }
 
@@ -466,65 +437,6 @@ impl<T> Once<T> {
     }
 }
 
-impl<T: Copy + Debug> Debug for LockCell<T> {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        f.debug_struct("LockCell")
-            .field("value", &self.get())
-            .finish()
-    }
-}
-
-impl<T:Default> Default for LockCell<T> {
-    /// Creates a `LockCell<T>`, with the `Default` value for T.
-    #[inline]
-    fn default() -> LockCell<T> {
-        LockCell::new(Default::default())
-    }
-}
-
-impl<T:PartialEq + Copy> PartialEq for LockCell<T> {
-    #[inline]
-    fn eq(&self, other: &LockCell<T>) -> bool {
-        self.get() == other.get()
-    }
-}
-
-impl<T:Eq + Copy> Eq for LockCell<T> {}
-
-impl<T:PartialOrd + Copy> PartialOrd for LockCell<T> {
-    #[inline]
-    fn partial_cmp(&self, other: &LockCell<T>) -> Option<Ordering> {
-        self.get().partial_cmp(&other.get())
-    }
-
-    #[inline]
-    fn lt(&self, other: &LockCell<T>) -> bool {
-        self.get() < other.get()
-    }
-
-    #[inline]
-    fn le(&self, other: &LockCell<T>) -> bool {
-        self.get() <= other.get()
-    }
-
-    #[inline]
-    fn gt(&self, other: &LockCell<T>) -> bool {
-        self.get() > other.get()
-    }
-
-    #[inline]
-    fn ge(&self, other: &LockCell<T>) -> bool {
-        self.get() >= other.get()
-    }
-}
-
-impl<T:Ord + Copy> Ord for LockCell<T> {
-    #[inline]
-    fn cmp(&self, other: &LockCell<T>) -> Ordering {
-        self.get().cmp(&other.get())
-    }
-}
-
 #[derive(Debug)]
 pub struct Lock<T>(InnerLock<T>);