swift-mirror/stdlib/public/core/Builtin.swift

//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2016 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See http://swift.org/LICENSE.txt for license information
// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//

import SwiftShims

// Definitions that make elements of Builtin usable in real code
// without gobs of boilerplate.

@available(*, unavailable, message: "use MemoryLayout<T>.size instead.")
public func sizeof<T>(_:T.Type) -> Int {
  Builtin.unreachable()
}

@available(*, unavailable, renamed: "MemoryLayout.size(ofValue:)")
public func sizeofValue<T>(_:T) -> Int {
  Builtin.unreachable()
}

@available(*, unavailable, message: "use MemoryLayout<T>.alignment instead.")
public func alignof<T>(_:T.Type) -> Int {
  Builtin.unreachable()
}

@available(*, unavailable, renamed: "MemoryLayout.alignment(ofValue:)")
public func alignofValue<T>(_:T) -> Int {
  Builtin.unreachable()
}

@available(*, unavailable, message: "use MemoryLayout<T>.stride instead.")
public func strideof<T>(_:T.Type) -> Int {
  Builtin.unreachable()
}

@available(*, unavailable, renamed: "MemoryLayout.stride(ofValue:)")
public func strideofValue<T>(_:T) -> Int {
  Builtin.unreachable()
}

// This function is the implementation of the `_roundUp` overload set.  It is
// marked `@inline(__always)` to make primary `_roundUp` entry points seem
// cheap enough for the inliner.
@_versioned
@inline(__always)
internal func _roundUpImpl(_ offset: UInt, toAlignment alignment: Int) -> UInt {
  _sanityCheck(alignment > 0)
  _sanityCheck(_isPowerOf2(alignment))
  // Note, given that offset is >= 0, and alignment > 0, we don't
  // need to underflow check the -1, as it can never underflow.
  let x = offset + UInt(bitPattern: alignment) &- 1
  // Note, as alignment is a power of 2, we'll use masking to efficiently
  // get the aligned value
  return x & ~(UInt(bitPattern: alignment) &- 1)
}

@_versioned
internal func _roundUp(_ offset: UInt, toAlignment alignment: Int) -> UInt {
  return _roundUpImpl(offset, toAlignment: alignment)
}

@_versioned
internal func _roundUp(_ offset: Int, toAlignment alignment: Int) -> Int {
  _sanityCheck(offset >= 0)
  return Int(_roundUpImpl(UInt(bitPattern: offset), toAlignment: alignment))
}

// This function takes a raw pointer and returns a typed pointer. It implicitly
// assumes that memory at the returned pointer is bound to `Destination` type.
@_versioned
internal func _roundUp<DestinationType>(
  _ pointer: UnsafeMutableRawPointer,
  toAlignmentOf destinationType: DestinationType.Type
) -> UnsafeMutablePointer<DestinationType> {
  // Note: unsafe unwrap is safe because this operation can only increase the
  // value, and can not produce a null pointer.
  return UnsafeMutablePointer<DestinationType>(
    bitPattern: _roundUpImpl(
      UInt(bitPattern: pointer),
      toAlignment: MemoryLayout<DestinationType>.alignment)
  ).unsafelyUnwrapped
}

/// Returns a tri-state of 0 = no, 1 = yes, 2 = maybe.
@_transparent
public // @testable
func _canBeClass<T>(_: T.Type) -> Int8 {
  return Int8(Builtin.canBeClass(T.self))
}

/// Returns the bits of `x`, interpreted as having type `U`.
///
/// - Warning: Breaks the guarantees of Swift's type system; use
///   with extreme care.  There's almost always a better way to do
///   anything.
///
@_transparent
public func unsafeBitCast<T, U>(_ x: T, to: U.Type) -> U {
  _precondition(MemoryLayout<T>.size == MemoryLayout<U>.size,
    "can't unsafeBitCast between types of different sizes")
  return Builtin.reinterpretCast(x)
}

/// `unsafeBitCast` something to `AnyObject`.
@_transparent
internal func _reinterpretCastToAnyObject<T>(_ x: T) -> AnyObject {
  return unsafeBitCast(x, to: AnyObject.self)
}

@_transparent
func == (lhs: Builtin.NativeObject, rhs: Builtin.NativeObject) -> Bool {
  return unsafeBitCast(lhs, to: Int.self) == unsafeBitCast(rhs, to: Int.self)
}

@_transparent
func != (lhs: Builtin.NativeObject, rhs: Builtin.NativeObject) -> Bool {
  return !(lhs == rhs)
}

@_transparent
func == (lhs: Builtin.RawPointer, rhs: Builtin.RawPointer) -> Bool {
  return unsafeBitCast(lhs, to: Int.self) == unsafeBitCast(rhs, to: Int.self)
}

@_transparent
func != (lhs: Builtin.RawPointer, rhs: Builtin.RawPointer) -> Bool {
  return !(lhs == rhs)
}

/// Returns `true` iff `t0` is identical to `t1`; i.e. if they are both
/// `nil` or they both represent the same type.
public func == (t0: Any.Type?, t1: Any.Type?) -> Bool {
  return unsafeBitCast(t0, to: Int.self) == unsafeBitCast(t1, to: Int.self)
}

/// Returns `false` iff `t0` is identical to `t1`; i.e. if they are both
/// `nil` or they both represent the same type.
public func != (t0: Any.Type?, t1: Any.Type?) -> Bool {
  return !(t0 == t1)
}


/// Tell the optimizer that this code is unreachable if condition is
/// known at compile-time to be true.  If condition is false, or true
/// but not a compile-time constant, this call has no effect.
@_transparent
internal func _unreachable(_ condition: Bool = true) {
  if condition {
    // FIXME: use a parameterized version of Builtin.unreachable when
    // <rdar://problem/16806232> is closed.
    Builtin.unreachable()
  }
}

/// Tell the optimizer that this code is unreachable if this builtin is
/// reachable after constant folding build configuration builtins.
@_versioned @_transparent internal
func _conditionallyUnreachable() -> Never {
  Builtin.conditionallyUnreachable()
}

@_versioned
@_silgen_name("_swift_isClassOrObjCExistentialType")
func _swift_isClassOrObjCExistentialType<T>(_ x: T.Type) -> Bool

/// Returns `true` iff `T` is a class type or an `@objc` existential such as
/// `AnyObject`.
@_versioned
@inline(__always)
internal func _isClassOrObjCExistential<T>(_ x: T.Type) -> Bool {

  switch _canBeClass(x) {
  // Is not a class.
  case 0:
    return false
  // Is a class.
  case 1:
    return true
  // Maybe a class.
  default:
    return _swift_isClassOrObjCExistentialType(x)
  }
}

/// Returns an `UnsafePointer` to the storage used for `object`.  There's
/// not much you can do with this other than use it to identify the
/// object.
@available(*, unavailable, message: "Removed in Swift 3. Use Unmanaged.passUnretained(x).toOpaque() instead.")
public func unsafeAddress(of object: AnyObject) -> UnsafeRawPointer {
  Builtin.unreachable()
}

@available(*, unavailable, message: "Removed in Swift 3. Use Unmanaged.passUnretained(x).toOpaque() instead.")
public func unsafeAddressOf(_ object: AnyObject) -> UnsafeRawPointer {
  Builtin.unreachable()
}

/// Converts a reference of type `T` to a reference of type `U` after
/// unwrapping one level of Optional.
///
/// Unwrapped `T` and `U` must be convertible to AnyObject. They may
/// be either a class or a class protocol. Either T, U, or both may be
/// optional references.
@_transparent
public func _unsafeReferenceCast<T, U>(_ x: T, to: U.Type) -> U {
  return Builtin.castReference(x)
}

/// - returns: `x as T`.
///
/// - Precondition: `x is T`.  In particular, in -O builds, no test is
///   performed to ensure that `x` actually has dynamic type `T`.
///
/// - Warning: Trades safety for performance.  Use `unsafeDowncast`
///   only when `x as T` has proven to be a performance problem and you
///   are confident that, always, `x is T`.  It is better than an
///   `unsafeBitCast` because it's more restrictive, and because
///   checking is still performed in debug builds.
@_transparent
public func unsafeDowncast<T : AnyObject>(_ x: AnyObject, to: T.Type) -> T {
  _debugPrecondition(x is T, "invalid unsafeDowncast")
  return Builtin.castReference(x)
}

@inline(__always)
public func _getUnsafePointerToStoredProperties(_ x: AnyObject)
  -> UnsafeMutableRawPointer {
  let storedPropertyOffset = _roundUp(
    MemoryLayout<_HeapObject>.size,
    toAlignment: MemoryLayout<Optional<AnyObject>>.alignment)
  return UnsafeMutableRawPointer(Builtin.bridgeToRawPointer(x)) +
    storedPropertyOffset
}

//===----------------------------------------------------------------------===//
// Branch hints
//===----------------------------------------------------------------------===//

// Use @_semantics to indicate that the optimizer recognizes the
// semantics of these function calls. This won't be necessary with
// mandatory generic inlining.

@_versioned
@_transparent
@_semantics("branchhint")
internal func _branchHint(_ actual: Bool, expected: Bool) -> Bool {
  return Bool(Builtin.int_expect_Int1(actual._value, expected._value))
}

/// Optimizer hint that `x` is expected to be `true`.
@_transparent
@_semantics("fastpath")
public func _fastPath(_ x: Bool) -> Bool {
  return _branchHint(x, expected: true)
}

/// Optimizer hint that `x` is expected to be `false`.
@_transparent
@_semantics("slowpath")
public func _slowPath(_ x: Bool) -> Bool {
  return _branchHint(x, expected: false)
}

/// Optimizer hint that the code where this function is called is on the fast
/// path.
@_transparent
public func _onFastPath() {
  Builtin.onFastPath()
}

//===--- Runtime shim wrappers --------------------------------------------===//

/// Returns `true` iff the class indicated by `theClass` uses native
/// Swift reference-counting.
#if _runtime(_ObjC)
// Declare it here instead of RuntimeShims.h, because we need to specify
// the type of argument to be AnyClass. This is currently not possible
// when using RuntimeShims.h
@_versioned
@_silgen_name("swift_objc_class_usesNativeSwiftReferenceCounting")
func _usesNativeSwiftReferenceCounting(_ theClass: AnyClass) -> Bool
#else
@_versioned
@inline(__always)
func _usesNativeSwiftReferenceCounting(_ theClass: AnyClass) -> Bool {
  return true
}
#endif

@_silgen_name("swift_class_getInstanceExtents")
func swift_class_getInstanceExtents(_ theClass: AnyClass)
  -> (negative: UInt, positive: UInt)

@_silgen_name("swift_objc_class_unknownGetInstanceExtents")
func swift_objc_class_unknownGetInstanceExtents(_ theClass: AnyClass)
  -> (negative: UInt, positive: UInt)

/// - Returns: 
@inline(__always)
internal func _class_getInstancePositiveExtentSize(_ theClass: AnyClass) -> Int {
#if _runtime(_ObjC)
  return Int(swift_objc_class_unknownGetInstanceExtents(theClass).positive)
#else
  return Int(swift_class_getInstanceExtents(theClass).positive)
#endif
}

//===--- Builtin.BridgeObject ---------------------------------------------===//

#if arch(i386) || arch(arm)
@_versioned
internal var _objectPointerSpareBits: UInt {
    @inline(__always) get { return 0x0000_0003 }
}
@_versioned
internal var _objectPointerIsObjCBit: UInt {
    @inline(__always) get { return 0x0000_0002 }
}
@_versioned
internal var _objectPointerLowSpareBitShift: UInt {
    @inline(__always) get { return 0 }
}
@_versioned
internal var _objCTaggedPointerBits: UInt {
  @inline(__always) get { return 0 }
}
#elseif arch(x86_64)
@_versioned
internal var _objectPointerSpareBits: UInt {
  @inline(__always) get { return 0x7F00_0000_0000_0006 }
}
@_versioned
internal var _objectPointerIsObjCBit: UInt {
  @inline(__always) get { return 0x4000_0000_0000_0000 }
}
@_versioned
internal var _objectPointerLowSpareBitShift: UInt {
  @inline(__always) get { return 1 }
}
@_versioned
internal var _objCTaggedPointerBits: UInt {
  @inline(__always) get { return 0x8000_0000_0000_0001 }
}
#elseif arch(arm64)
@_versioned
internal var _objectPointerSpareBits: UInt {
  @inline(__always) get { return 0x7F00_0000_0000_0007 }
}
@_versioned
internal var _objectPointerIsObjCBit: UInt {
  @inline(__always) get { return 0x4000_0000_0000_0000 }
}
@_versioned
internal var _objectPointerLowSpareBitShift: UInt {
    @inline(__always) get { return 0 }
}
@_versioned
internal var _objCTaggedPointerBits: UInt {
    @inline(__always) get { return 0x8000_0000_0000_0000 }
}
#elseif arch(powerpc64) || arch(powerpc64le)
@_versioned
internal var _objectPointerSpareBits: UInt {
  @inline(__always) get { return 0x0000_0000_0000_0007 }
}
@_versioned
internal var _objectPointerIsObjCBit: UInt {
  @inline(__always) get { return 0x0000_0000_0000_0002 }
}
@_versioned
internal var _objectPointerLowSpareBitShift: UInt {
    @inline(__always) get { return 0 }
}
@_versioned
internal var _objCTaggedPointerBits: UInt {
    @inline(__always) get { return 0 }
}
#elseif arch(s390x)
internal var _objectPointerSpareBits: UInt {
  @inline(__always) get { return 0x0000_0000_0000_0007 }
}
internal var _objectPointerIsObjCBit: UInt {
  @inline(__always) get { return 0x0000_0000_0000_0002 }
}
internal var _objectPointerLowSpareBitShift: UInt {
  @inline(__always) get { return 0 }
}
internal var _objCTaggedPointerBits: UInt {
  @inline(__always) get { return 0 }
}
#endif

/// Extract the raw bits of `x`.
@_versioned
@inline(__always)
internal func _bitPattern(_ x: Builtin.BridgeObject) -> UInt {
  return UInt(Builtin.castBitPatternFromBridgeObject(x))
}

/// Extract the raw spare bits of `x`.
@_versioned
@inline(__always)
internal func _nonPointerBits(_ x: Builtin.BridgeObject) -> UInt {
  return _bitPattern(x) & _objectPointerSpareBits
}

@_versioned
@inline(__always)
internal func _isObjCTaggedPointer(_ x: AnyObject) -> Bool {
  return (Builtin.reinterpretCast(x) & _objCTaggedPointerBits) != 0
}

/// Create a `BridgeObject` around the given `nativeObject` with the
/// given spare bits.
///
/// Reference-counting and other operations on this
/// object will have access to the knowledge that it is native.
///
/// - Precondition: `bits & _objectPointerIsObjCBit == 0`,
///   `bits & _objectPointerSpareBits == bits`.
@_versioned
@inline(__always)
internal func _makeNativeBridgeObject(
  _ nativeObject: AnyObject, _ bits: UInt
) -> Builtin.BridgeObject {
  _sanityCheck(
    (bits & _objectPointerIsObjCBit) == 0,
    "BridgeObject is treated as non-native when ObjC bit is set"
  )
  return _makeBridgeObject(nativeObject, bits)
}

/// Create a `BridgeObject` around the given `objCObject`.
@inline(__always)
public // @testable
func _makeObjCBridgeObject(
  _ objCObject: AnyObject
) -> Builtin.BridgeObject {
  return _makeBridgeObject(
    objCObject,
    _isObjCTaggedPointer(objCObject) ? 0 : _objectPointerIsObjCBit)
}

/// Create a `BridgeObject` around the given `object` with the
/// given spare bits.
///
/// - Precondition:
///
///   1. `bits & _objectPointerSpareBits == bits`
///   2. if `object` is a tagged pointer, `bits == 0`.  Otherwise,
///      `object` is either a native object, or `bits ==
///      _objectPointerIsObjCBit`.
@_versioned
@inline(__always)
internal func _makeBridgeObject(
  _ object: AnyObject, _ bits: UInt
) -> Builtin.BridgeObject {
  _sanityCheck(!_isObjCTaggedPointer(object) || bits == 0,
    "Tagged pointers cannot be combined with bits")

  _sanityCheck(
    _isObjCTaggedPointer(object)
    || _usesNativeSwiftReferenceCounting(type(of: object))
    || bits == _objectPointerIsObjCBit,
    "All spare bits must be set in non-native, non-tagged bridge objects"
  )

  _sanityCheck(
    bits & _objectPointerSpareBits == bits,
    "Can't store non-spare bits into Builtin.BridgeObject")

  return Builtin.castToBridgeObject(
    object, bits._builtinWordValue
  )
}

@_versioned
@_silgen_name("_swift_class_getSuperclass")
internal func _swift_class_getSuperclass(_ t: AnyClass) -> AnyClass?

/// Returns the superclass of `t`, if any.  The result is `nil` if `t` is
/// a root class or class protocol.
@inline(__always)
public // @testable
func _getSuperclass(_ t: AnyClass) -> AnyClass? {
  return _swift_class_getSuperclass(t)
}

/// Returns the superclass of `t`, if any.  The result is `nil` if `t` is
/// not a class, is a root class, or is a class protocol.
@inline(__always)
public // @testable
func _getSuperclass(_ t: Any.Type) -> AnyClass? {
  return (t as? AnyClass).flatMap { _getSuperclass($0) }
}

//===--- Builtin.IsUnique -------------------------------------------------===//
// _isUnique functions must take an inout object because they rely on
// Builtin.isUnique which requires an inout reference to preserve
// source-level copies in the presence of ARC optimization.
//
// Taking an inout object makes sense for two additional reasons:
//
// 1. You should only call it when about to mutate the object.
//    Doing so otherwise implies a race condition if the buffer is
//    shared across threads.
//
// 2. When it is not an inout function, self is passed by
//    value... thus bumping the reference count and disturbing the
//    result we are trying to observe, Dr. Heisenberg!
//
// _isUnique and _isUniquePinned cannot be made public or the compiler
// will attempt to generate generic code for the transparent function
// and type checking will fail.

/// Returns `true` if `object` is uniquely referenced.
@_versioned
@_transparent
internal func _isUnique<T>(_ object: inout T) -> Bool {
  return Bool(Builtin.isUnique(&object))
}

/// Returns `true` if `object` is uniquely referenced or pinned.
@_versioned
@_transparent
internal func _isUniqueOrPinned<T>(_ object: inout T) -> Bool {
  return Bool(Builtin.isUniqueOrPinned(&object))
}

/// Returns `true` if `object` is uniquely referenced.
/// This provides sanity checks on top of the Builtin.
@_transparent
public // @testable
func _isUnique_native<T>(_ object: inout T) -> Bool {
  // This could be a bridge object, single payload enum, or plain old
  // reference. Any case it's non pointer bits must be zero, so
  // force cast it to BridgeObject and check the spare bits.
  _sanityCheck(
    (_bitPattern(Builtin.reinterpretCast(object)) & _objectPointerSpareBits)
    == 0)
  _sanityCheck(_usesNativeSwiftReferenceCounting(
      type(of: Builtin.reinterpretCast(object) as AnyObject)))
  return Bool(Builtin.isUnique_native(&object))
}

/// Returns `true` if `object` is uniquely referenced or pinned.
/// This provides sanity checks on top of the Builtin.
@_transparent
public // @testable
func _isUniqueOrPinned_native<T>(_ object: inout T) -> Bool {
  // This could be a bridge object, single payload enum, or plain old
  // reference. Any case it's non pointer bits must be zero.
  _sanityCheck(
    (_bitPattern(Builtin.reinterpretCast(object)) & _objectPointerSpareBits)
    == 0)
  _sanityCheck(_usesNativeSwiftReferenceCounting(
      type(of: Builtin.reinterpretCast(object) as AnyObject)))
  return Bool(Builtin.isUniqueOrPinned_native(&object))
}

/// Returns `true` if type is a POD type. A POD type is a type that does not
/// require any special handling on copying or destruction.
@_transparent
public // @testable
func _isPOD<T>(_ type: T.Type) -> Bool {
  return Bool(Builtin.ispod(type))
}

/// Returns `true` if type is nominally an Optional type.
@_transparent
public // @testable
func _isOptional<T>(_ type: T.Type) -> Bool {
  return Bool(Builtin.isOptional(type))
}

@available(*, unavailable, message: "Removed in Swift 3. Please use Optional.unsafelyUnwrapped instead.")
public func unsafeUnwrap<T>(_ nonEmpty: T?) -> T {
  Builtin.unreachable()
}

/// Extract an object reference from an Any known to contain an object.
internal func _unsafeDowncastToAnyObject(fromAny any: Any) -> AnyObject {
  _sanityCheck(type(of: any) is AnyObject.Type
               || type(of: any) is AnyObject.Protocol,
               "Any expected to contain object reference")
  // With a SIL instruction, we could more efficiently grab the object reference
  // out of the Any's inline storage.

  // On Linux, bridging isn't supported, so this is a force cast.
#if _runtime(_ObjC)
  return any as AnyObject
#else
  return any as! AnyObject
#endif
}