Change from _ContiguousCollection to AccelerateBuffer.

Since we are not adding ContiguousCollection to the standard library at this point in time, we can and should use something more narrowly tailored to Accelerate's needs. In particular, Accelerate does not require almost anything from Collection; it only needs withUnsafe[Mutable]BufferPointer, count, and the Element associatedtype. So let's pare the protocol back to only those things, and give it a name scoped as well: [Mutable]AccelerateBuffer.

In practice, most types people use with these API will be Collections anyway, but this enables a few useful additional use cases:

- Fixed-size buffers
- Retroactive conformance of SIMD types

Author: stephentyrone

stdlib/public/Darwin/Accelerate/CMakeLists.txt

@@ -10,8 +10,6 @@ add_swift_target_library(swiftAccelerate ${SWIFT_SDK_OVERLAY_LIBRARY_BUILD_TYPES
   GYB_SOURCES
     BNNS.swift.gyb
 
-  "${SWIFT_SOURCE_DIR}/stdlib/linker-support/magic-symbols-for-install-name.c"
-
   SWIFT_COMPILE_FLAGS "${SWIFT_RUNTIME_SWIFT_COMPILE_FLAGS}"
   LINK_FLAGS "${SWIFT_RUNTIME_SWIFT_LINK_FLAGS}"
   TARGET_SDKS OSX IOS IOS_SIMULATOR TVOS TVOS_SIMULATOR WATCHOS WATCHOS_SIMULATOR

stdlib/public/Darwin/Accelerate/ContiguousCollection.swift

@@ -10,30 +10,30 @@
 //
 //===----------------------------------------------------------------------===//
 
-/// A collection that supports access to its underlying contiguous storage.
+/// An object composed of count elements that are stored contiguously in memory.
+///
+/// In practice, most types conforming to this protocol will be Collections,
+/// but they need not be--they need only have an Element type and count, and
+/// provide the withUnsafeBufferPointer function.
 @available(iOS 9999, OSX 9999, tvOS 9999, watchOS 9999, *)
-public protocol _ContiguousCollection: Collection
-where SubSequence: _ContiguousCollection {
-    /// Calls a closure with a pointer to the array's contiguous storage.
+public protocol AccelerateBuffer {
+    /// The buffer's element type.
+    associatedtype Element
+    /// The number of elements in the buffer.
+    var count: Int { get }
+    /// Calls a closure with a pointer to the object's contiguous storage.
     func withUnsafeBufferPointer<R>(
         _ body: (UnsafeBufferPointer<Element>) throws -> R
         ) rethrows -> R
 }
 
+/// A mutable object composed of count elements that are stored contiguously
+/// in memory.
+///
+/// In practice, most types conforming to this protocol will be
+/// MutableCollections, but they need not be.
 @available(iOS 9999, OSX 9999, tvOS 9999, watchOS 9999, *)
-public extension _ContiguousCollection {
-    func withUnsafeBufferPointer<R>(
-        _ body: (UnsafeBufferPointer<Element>) throws -> R
-        ) rethrows -> R {
-        return try withContiguousStorageIfAvailable(body)!
-    }
-}
-
-/// A collection that supports mutable access to its underlying contiguous
-/// storage.
-@available(iOS 9999, OSX 9999, tvOS 9999, watchOS 9999, *)
-public protocol _MutableContiguousCollection: _ContiguousCollection, MutableCollection
-where SubSequence: _MutableContiguousCollection {
+public protocol MutableAccelerateBuffer: AccelerateBuffer {
     /// Calls the given closure with a pointer to the array's mutable contiguous
     /// storage.
     mutating func withUnsafeMutableBufferPointer<R>(
@@ -42,7 +42,16 @@ where SubSequence: _MutableContiguousCollection {
 }
 
 @available(iOS 9999, OSX 9999, tvOS 9999, watchOS 9999, *)
-extension _MutableContiguousCollection {
+public extension AccelerateBuffer where Self: Collection {
+    func withUnsafeBufferPointer<R>(
+        _ body: (UnsafeBufferPointer<Element>) throws -> R
+        ) rethrows -> R {
+        return try withContiguousStorageIfAvailable(body)!
+    }
+}
+
+@available(iOS 9999, OSX 9999, tvOS 9999, watchOS 9999, *)
+extension MutableAccelerateBuffer where Self: MutableCollection {
     public mutating func withUnsafeMutableBufferPointer<R>(
         _ body: (inout UnsafeMutableBufferPointer<Element>) throws -> R
         ) rethrows -> R {
@@ -51,22 +60,22 @@ extension _MutableContiguousCollection {
 }
 
 @available(iOS 9999, OSX 9999, tvOS 9999, watchOS 9999, *)
-extension Array: _MutableContiguousCollection { }
+extension Array: MutableAccelerateBuffer { }
 
 @available(iOS 9999, OSX 9999, tvOS 9999, watchOS 9999, *)
-extension ContiguousArray: _MutableContiguousCollection { }
+extension ContiguousArray: MutableAccelerateBuffer { }
 
 @available(iOS 9999, OSX 9999, tvOS 9999, watchOS 9999, *)
-extension ArraySlice: _MutableContiguousCollection { }
+extension ArraySlice: MutableAccelerateBuffer { }
 
 @available(iOS 9999, OSX 9999, tvOS 9999, watchOS 9999, *)
-extension UnsafeBufferPointer: _ContiguousCollection { }
+extension UnsafeBufferPointer: AccelerateBuffer { }
 
 @available(iOS 9999, OSX 9999, tvOS 9999, watchOS 9999, *)
-extension UnsafeMutableBufferPointer: _MutableContiguousCollection { }
+extension UnsafeMutableBufferPointer: MutableAccelerateBuffer { }
 
 @available(iOS 9999, OSX 9999, tvOS 9999, watchOS 9999, *)
-extension Slice: _ContiguousCollection where Base: _ContiguousCollection { }
+extension Slice: AccelerateBuffer where Base: Collection { }
 
 @available(iOS 9999, OSX 9999, tvOS 9999, watchOS 9999, *)
-extension Slice: _MutableContiguousCollection where Base: _MutableContiguousCollection { }
+extension Slice: MutableAccelerateBuffer where Base: MutableCollection { }

stdlib/public/Darwin/Accelerate/Quadrature.swift

@@ -10,8 +10,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-import Accelerate
-
 // MARK: Quadrature
 
 @available(iOS 9999, macOS 9999, tvOS 9999, watchOS 9999, *)