Add atomics support in the standard library

.gitignore

@@ -22,3 +22,4 @@
 **.lib
 **.7z
 llvm.pc
+Tools/__pycache__

StandardLibrary/Sources/LowLevel/Threading/Atomic.hylo

@@ -0,0 +1,122 @@
+
+/// Defines atomic operations for `T`. 
+public type Atomic<T: AtomicRepresentable>: SemiRegular {
+
+  /// The storage for the atomic operations.
+  var storage: T.AtomicRepresentation
+
+  /// Initializes `self` with the zero value.
+  public init() {
+    &storage = .new()
+  }
+
+  /// Initializes `self` with `value`.
+  public init(value: sink T) {
+    &storage = .new()
+    store(value, ordering: /*AtomicStoreOrdering.relaxed*/ .new(value: 0))
+    // TODO: using atomic ordering constants produce linker errors
+  }
+
+  /// Atomically load the value from the atomic, using `ordering`.
+  public fun load(ordering: AtomicLoadOrdering) -> T {
+    return T.decodeAtomicRepresentation(storage.load(ordering: ordering))
+  }
+
+  /// Atomically store `value` into the atomic, using `ordering`.
+  public fun store(_ value: sink T, ordering: AtomicStoreOrdering) inout {
+    storage.store(T.encodeAtomicRepresentation(value), ordering: ordering)
+  }
+
+  /// Atomically exchanges the value in the atomic with `desired`, using `ordering`.
+  public fun exchange(desired: sink T, ordering: AtomicUpdateOrdering) inout -> T {
+    return T.decodeAtomicRepresentation(storage.exchange(desired: T.encodeAtomicRepresentation(desired), ordering: ordering))
+  }
+
+  /// Atomically exchanges the atomic with `desired`, if the original value is equal to `expected`, using `ordering`.
+  /// Returns a tuple containing the original value and a boolean indicating whether the exchange was successful.
+  public fun compare_and_exchange(expected: sink T, desired: sink T, ordering: AtomicUpdateOrdering) inout -> {exchanged: Bool, original: T} {
+    let r = storage.compare_and_exchange(
+      expected: T.encodeAtomicRepresentation(expected),
+      desired: T.encodeAtomicRepresentation(desired),
+      success_ordering: ordering,
+      failure_ordering: failure_ordering(for: ordering))
+    return (exchanged: r.0, original: T.decodeAtomicRepresentation(r.1))
+  }
+
+  /// Atomically exchanges the atomic with `desired`, if the original value is equal to `expected`, using `success_ordering` for the update, and `failure_ordering` for loading the new value in case of failure.
+  /// Returns a tuple containing the original value and a boolean indicating whether the exchange was successful.
+  public fun compare_and_exchange(expected: sink T, desired: sink T, success_ordering: AtomicUpdateOrdering, failure_ordering: AtomicLoadOrdering) inout -> {exchanged: Bool, original: T} {
+    let r = storage.compare_and_exchange(
+      expected: T.encodeAtomicRepresentation(expected),
+      desired: T.encodeAtomicRepresentation(desired),
+      success_ordering: success_ordering,
+      failure_ordering: failure_ordering)
+    return (exchanged: r.0, original: T.decodeAtomicRepresentation(r.1))
+  }
+
+  /// Same as `compare_and_exchange`, but may fail spuriously.
+  public fun weak_compare_and_exchange(expected: sink T, desired: sink T, ordering: AtomicUpdateOrdering) inout -> {exchanged: Bool, original: T} {
+    let r = storage.weak_compare_and_exchange(
+      expected: T.encodeAtomicRepresentation(expected),
+      desired: T.encodeAtomicRepresentation(desired),
+      success_ordering: ordering,
+      failure_ordering: failure_ordering(for: ordering))
+    return (exchanged: r.0, original: T.decodeAtomicRepresentation(r.1))
+  }
+
+  /// Same as `compare_and_exchange`, but may fail spuriously.
+  public fun weak_compare_and_exchange(expected: sink T, desired: sink T, success_ordering: AtomicUpdateOrdering, failure_ordering: AtomicLoadOrdering) inout -> {exchanged: Bool, original: T} {
+    let r = storage.weak_compare_and_exchange(
+      expected: T.encodeAtomicRepresentation(expected),
+      desired: T.encodeAtomicRepresentation(desired),
+      success_ordering: success_ordering,
+      failure_ordering: failure_ordering)
+    return (exchanged: r.0, original: T.decodeAtomicRepresentation(r.1))
+  }
+
+}
+
+/// Atomic operations for integer types
+public extension Atomic where T.AtomicRepresentation: IntegerPlatformAtomic, T: Numeric {
+
+  /// Atomically updates `this` by adding `value` to it, using `ordering`, and return the original value.
+  public fun fetch_add(_ value: sink T, ordering: AtomicUpdateOrdering) inout -> T {
+    return T.decodeAtomicRepresentation(storage.fetch_add(T.encodeAtomicRepresentation(value), ordering: ordering))
+  }
+
+  /// Atomically updates `this` by subtracting `value` from it, using `ordering`, and return the original value.
+  public fun fetch_sub(_ value: sink T, ordering: AtomicUpdateOrdering) inout -> T {
+    return T.decodeAtomicRepresentation(storage.fetch_sub(T.encodeAtomicRepresentation(value), ordering: ordering))
+  }
+
+  /// Atomically updates `this` by using the maximum of `value` and itself, using `ordering`, and return the original value.
+  public fun fetch_max(_ value: sink T, ordering: AtomicUpdateOrdering) inout -> T {
+    return T.decodeAtomicRepresentation(storage.fetch_max(T.encodeAtomicRepresentation(value), ordering: ordering))
+  }
+
+  /// Atomically updates `this` by using the minimum of `value` and itself, using `ordering`, and return the original value.
+  public fun fetch_min(_ value: sink T, ordering: AtomicUpdateOrdering) inout -> T {
+    return T.decodeAtomicRepresentation(storage.fetch_min(T.encodeAtomicRepresentation(value), ordering: ordering))
+  }
+
+  /// Atomically updates `this` by performing a bitwise AND of `value` and itself, using `ordering`, and return the original value.
+  public fun fetch_and(_ value: sink T, ordering: AtomicUpdateOrdering) inout -> T {
+    return T.decodeAtomicRepresentation(storage.fetch_and(T.encodeAtomicRepresentation(value), ordering: ordering))
+  }
+
+  /// Atomically updates `this` by performing a bitwise NAND of `value` and itself, using `ordering`, and return the original value.
+  public fun fetch_nand(_ value: sink T, ordering: AtomicUpdateOrdering) inout -> T {
+    return T.decodeAtomicRepresentation(storage.fetch_nand(T.encodeAtomicRepresentation(value), ordering: ordering))
+  }
+
+  /// Atomically updates `this` by performing a bitwise OR of `value` and itself, using `ordering`, and return the original value.
+  public fun fetch_or(_ value: sink T, ordering: AtomicUpdateOrdering) inout -> T {
+    return T.decodeAtomicRepresentation(storage.fetch_or(T.encodeAtomicRepresentation(value), ordering: ordering))
+  }
+
+  /// Atomically updates `this` by performing a bitwise XOR of `value` and itself, using `ordering`, and return the original value.
+  public fun fetch_xor(_ value: sink T, ordering: AtomicUpdateOrdering) inout -> T {
+    return T.decodeAtomicRepresentation(storage.fetch_xor(T.encodeAtomicRepresentation(value), ordering: ordering))
+  }
+
+}

StandardLibrary/Sources/LowLevel/Threading/AtomicOrderings.hylo

@@ -0,0 +1,167 @@
+/// Specifies the memory ordering sematics for an atomic load operation.
+public type AtomicLoadOrdering: Regular {
+
+  public memberwise init
+
+  internal let value: Int
+
+}
+
+public extension AtomicLoadOrdering {
+
+  /// Guarantees the atomicity of the load operation, but does not impose any ordering constraints
+  /// on other memory operations.
+  ///
+  /// Corresponds to the `memory_order_relaxed` C++ memory ordering.
+  public static let relaxed: AtomicLoadOrdering = .new(value: 0)
+
+  /// An acquiring load operation syncrhonizes with a releasing store operation on the same atomic
+  /// variable. The thread performing the acquiring operation agrees with the thread performing the
+  /// releasing operation that all the subsequent load operations (atomic or not) on the acquiring
+  /// thread happen after the atomic operation itself.
+  ///
+  /// Provides a barrier that prevents read/write memory operations to be reordered before the
+  /// atomic load. This barrier can be used to acquire a lock.
+  ///
+  /// Corresponds to the `memory_order_acquire` C++ memory ordering.
+  public static let acquiring: AtomicLoadOrdering = .new(value: 1)
+
+  /// A sequentially consistent load operation provides the same guarantees as an acquiring load
+  /// and also guarantees that all sequentially consistent operations on the atomic variable will
+  /// have a total squential order, across all threads.
+  ///
+  /// Provides a barrier that prevents read/write memory operations to be reordered before and
+  /// after the atomic load.
+  ///
+  /// Corresponds to the `memory_order_seq_cst` C++ memory ordering.
+  public static let sequentially_consistent: AtomicLoadOrdering = .new(value: 4)
+
+}
+
+/// Specifies the memory ordering sematics for an atomic store operation.
+public type AtomicStoreOrdering: Regular {
+
+  public memberwise init
+
+  internal let value: Int
+
+}
+
+public extension AtomicStoreOrdering {
+
+  /// Guarantees the atomicity of the store operation, but does not impose any ordering constraints
+  /// on other memory operations.
+  ///
+  /// Corresponds to the `memory_order_relaxed` C++ memory ordering.
+  public static let relaxed: AtomicStoreOrdering = .new(value: 0)
+
+  /// A releasing store operation syncrhonizes with an acquiring load operation on the same atomic
+  /// variable. The thread performing the releasing operation agrees with the thread performing the
+  /// acquiring operation that all the previous store operations (atomic or not) on the releasing
+  /// thread will be seen before the atomic operation itself.
+  ///
+  /// Provides a barrier that prevents read/write memory operations to be reordered after the
+  /// atomic store. This barrier can be used to release a lock.
+  ///
+  /// Corresponds to the `memory_order_release` C++ memory ordering.
+  public static let releasing: AtomicStoreOrdering = .new(value: 2)
+
+  /// A sequentially consistent store operation provides the same guarantees as a releasing store
+  /// and also guarantees that all sequentially consistent operations on the atomic variable will
+  /// have a total squential order, across all threads.
+  ///
+  /// Provides a barrier that prevents read/write memory operations to be reordered before and
+  /// after the atomic store.
+  ///
+  /// Corresponds to the `memory_order_seq_cst` C++ memory ordering.
+  public static let sequentially_consistent: AtomicStoreOrdering = .new(value: 4)
+
+}
+
+/// Specifies the memory ordering sematics for an atomic read-modify-write (update) operation.
+public type AtomicUpdateOrdering: Regular {
+
+  public memberwise init
+
+  internal let value: Int
+
+}
+
+public extension AtomicUpdateOrdering {
+
+  /// Guarantees the atomicity of the load operation, but does not impose any ordering constraints
+  /// on other memory operations.
+  ///
+  /// Corresponds to the `memory_order_relaxed` C++ memory ordering.
+  public static let relaxed: AtomicUpdateOrdering = .new(value: 0)
+
+  /// An acquiring update operation syncrhonizes with a releasing store operation on the same
+  /// atomic variable whose value it reads. The thread performing the acquiring operation agrees
+  /// with the thread performing the releasing operation that all the subsequent load operations
+  /// (atomic or not) on the acquiring thread happen after the atomic operation itself.
+  ///
+  /// Provides a barrier that prevents read/write memory operations to be reordered before the
+  /// atomic operation. This barrier can be used to acquire a lock.
+  ///
+  /// Corresponds to the `memory_order_acquire` C++ memory ordering.
+  public static let acquiring: AtomicUpdateOrdering = .new(value: 1)
+
+  /// A releasing update operation syncrhonizes with an acquiring load operation on the same atomic
+  /// variable that reads the updated value. The thread performing the releasing operation agrees
+  /// with the thread performing the acquiring operation that all the previous store operations
+  /// (atomic or not) on the releasing thread will be seen before the atomic operation itself.
+  ///
+  /// Provides a barrier that prevents read/write memory operations to be reordered after the
+  /// atomic update. This barrier can be used to release a lock.
+  ///
+  /// Corresponds to the `memory_order_release` C++ memory ordering.
+  public static let releasing: AtomicUpdateOrdering = .new(value: 2)
+
+  /// An acquiring and releasing update operation syncrhonizes with both acquiring loads that read
+  /// the updated value and with the releasing stores that update the value that this update reads.
+  /// The thread performing the update operation agrees with the threads performing the acquiring
+  /// load that all the previous store operations (atomic or not) on the releasing thread will be
+  /// seen before the atomic operation itself. The thread performing the update operation also
+  /// agrees with the threads performing the releasing store of the value read by the update that
+  /// all the previous store operations (atomic or not) on the updating thread happen before the
+  /// update.
+  ///
+  /// Provides a barrier that prevents read/write memory operations to be reordered before and
+  /// after the atomic update.
+  ///
+  /// Corresponds to the `memory_order_seq_cst` C++ memory ordering.
+  public static let acquiring_and_releasing: AtomicUpdateOrdering = .new(value: 3)
+
+  /// A sequentially consistent update operation provides the same guarantees as an acquiring and
+  /// releasing update and also guarantees that all sequentially consistent operations on the
+  /// atomic variable will have a total squential order, across all threads.
+  ///
+  /// Provides a barrier that prevents read/write memory operations to be reordered before and
+  /// after the atomic update.
+  ///
+  /// Corresponds to the `memory_order_seq_cst` C++ memory ordering.
+  public static let sequentially_consistent: AtomicUpdateOrdering = .new(value: 4)
+
+}
+
+/// Transforms from an atomic update ordering to a corresponding atomic load ordering, to be used
+/// in `compare_and_exchange` operations to get the failure ordering from the success ordering.
+// TODO: this should be internal, but we have a bug that generates a linker error
+public fun failure_ordering(for ordering: AtomicUpdateOrdering) -> AtomicLoadOrdering {
+  if ordering == /*AtomicUpdateOrdering.relaxed*/ AtomicUpdateOrdering(value: 0) {
+    return /*AtomicLoadOrdering.relaxed.copy()*/ AtomicLoadOrdering(value: 0)
+  }
+  if ordering == /*AtomicUpdateOrdering.acquiring*/  AtomicUpdateOrdering(value: 1) {
+    return /*AtomicLoadOrdering.acquiring.copy()*/ AtomicLoadOrdering(value: 1)
+  }
+  if ordering == /*AtomicUpdateOrdering.releasing*/  AtomicUpdateOrdering(value: 2) {
+    return /*AtomicLoadOrdering.relaxed.copy()*/ AtomicLoadOrdering(value: 0)
+  }
+  if ordering == /*AtomicUpdateOrdering.acquiring_and_releasing*/  AtomicUpdateOrdering(value: 3) {
+    return /*AtomicLoadOrdering.acquiring.copy()*/ AtomicLoadOrdering(value: 1)
+  }
+  if ordering == /*AtomicUpdateOrdering.sequentially_consistent*/  AtomicUpdateOrdering(value: 4) {
+    return /*AtomicLoadOrdering.sequentially_consistent.copy()*/ AtomicLoadOrdering(value: 4)
+  }
+  trap()
+}