Merge pull request #41512 from lorentey/clock-fixes

[stdlib] Some more clock adjustments

Author: lorentey

stdlib/public/Concurrency/Clock.cpp

@@ -127,7 +127,7 @@ switch (clock_id) {
       *seconds = suspending.tv_sec;
       *nanoseconds = suspending.tv_nsec;
 #elif defined(__APPLE__) && HAS_TIME
-      clock_gettime(CLOCK_UPTIME_RAW, &suspending);
+      clock_getres(CLOCK_UPTIME_RAW, &suspending);
       *seconds = suspending.tv_sec;
       *nanoseconds = suspending.tv_nsec;
 #elif defined(_WIN32)

stdlib/public/core/Duration.swift

@@ -43,13 +43,13 @@ public struct Duration: Sendable {
   internal var _high: Int64
 
   @inlinable
-  internal init(_low: UInt64, high: Int64) {
-    self._low = _low
-    self._high = high
+  internal init(_high: Int64, low: UInt64) {
+    self._low = low
+    self._high = _high
   }
 
   internal init(_attoseconds: _Int128) {
-    self.init(_low: _attoseconds.low, high: _attoseconds.high)
+    self.init(_high: _attoseconds.high, low: _attoseconds.low)
   }
 
   /// Construct a `Duration` by adding attoseconds to a seconds value.
@@ -86,16 +86,18 @@ public struct Duration: Sendable {
   internal var _attoseconds: _Int128 {
     _Int128(high: _high, low: _low)
   }
+}
 
+@available(SwiftStdlib 5.7, *)
+extension Duration {
   /// The composite components of the `Duration`.
   ///
   /// This is intended for facilitating conversions to existing time types. The
   /// attoseconds value will not exceed 1e18 or be lower than -1e18.
+  @available(SwiftStdlib 5.7, *)
   public var components: (seconds: Int64, attoseconds: Int64) {
-    let seconds = _attoseconds / 1_000_000_000_000_000_000
-    let attoseconds =
-      Int64((_attoseconds - seconds * 1_000_000_000_000_000_000))
-    return (Int64(seconds), attoseconds)
+    let (seconds, attoseconds) = _attoseconds.dividedBy1e18()
+    return (Int64(seconds), Int64(attoseconds))
   }
 }
 
@@ -109,8 +111,8 @@ extension Duration {
   /// - Returns: A `Duration` representing a given number of seconds.
   @available(SwiftStdlib 5.7, *)
   public static func seconds<T: BinaryInteger>(_ seconds: T) -> Duration {
-    return Duration(_attoseconds: _Int128(seconds) *
-                                 1_000_000_000_000_000_000)
+    return Duration(_attoseconds:
+      _Int128(seconds).multiplied(by: 1_000_000_000_000_000_000 as UInt64))
   }
 
   /// Construct a `Duration` given a number of seconds represented as a 
@@ -121,8 +123,7 @@ extension Duration {
   /// - Returns: A `Duration` representing a given number of seconds.
   @available(SwiftStdlib 5.7, *)
   public static func seconds(_ seconds: Double) -> Duration {
-    return Duration(_attoseconds: _Int128(seconds *
-                                 1_000_000_000_000_000_000))
+    return Duration(_attoseconds: _Int128(seconds * 1_000_000_000_000_000_000))
   }
 
   /// Construct a `Duration` given a number of milliseconds represented as a 
@@ -135,8 +136,8 @@ extension Duration {
   public static func milliseconds<T: BinaryInteger>(
     _ milliseconds: T
   ) -> Duration {
-    return Duration(_attoseconds: _Int128(milliseconds) *
-                                 1_000_000_000_000_000)
+    return Duration(_attoseconds:
+      _Int128(milliseconds).multiplied(by: 1_000_000_000_000_000 as UInt64))
   }
 
   /// Construct a `Duration` given a number of seconds milliseconds as a 
@@ -147,8 +148,8 @@ extension Duration {
   /// - Returns: A `Duration` representing a given number of milliseconds.
   @available(SwiftStdlib 5.7, *)
   public static func milliseconds(_ milliseconds: Double) -> Duration {
-    return Duration(_attoseconds: _Int128(milliseconds *
-                                 1_000_000_000_000_000))
+    return Duration(_attoseconds:
+      _Int128(milliseconds * 1_000_000_000_000_000))
   }
 
   /// Construct a `Duration` given a number of microseconds represented as a 
@@ -161,8 +162,8 @@ extension Duration {
   public static func microseconds<T: BinaryInteger>(
     _ microseconds: T
   ) -> Duration {
-    return Duration(_attoseconds: _Int128(microseconds) *
-                                 1_000_000_000_000)
+    return Duration(_attoseconds:
+      _Int128(microseconds).multiplied(by: 1_000_000_000_000 as UInt64))
   }
 
   /// Construct a `Duration` given a number of seconds microseconds as a 
@@ -173,8 +174,8 @@ extension Duration {
   /// - Returns: A `Duration` representing a given number of microseconds.
   @available(SwiftStdlib 5.7, *)
   public static func microseconds(_ microseconds: Double) -> Duration {
-    return Duration(_attoseconds: _Int128(microseconds *
-                                 1_000_000_000_000))
+    return Duration(_attoseconds:
+      _Int128(microseconds * 1_000_000_000_000))
   }
 
   /// Construct a `Duration` given a number of nanoseconds represented as a 
@@ -187,21 +188,21 @@ extension Duration {
   public static func nanoseconds<T: BinaryInteger>(
     _ nanoseconds: T
   ) -> Duration {
-    return Duration(_attoseconds: _Int128(nanoseconds) *
-                                 1_000_000_000)
+    return Duration(_attoseconds:
+      _Int128(nanoseconds).multiplied(by: 1_000_000_000))
   }
 }
 
 @available(SwiftStdlib 5.7, *)
-extension Duration: Codable { 
+extension Duration: Codable {
   @available(SwiftStdlib 5.7, *)
   public init(from decoder: Decoder) throws {
     var container = try decoder.unkeyedContainer()
     let high = try container.decode(Int64.self)
     let low = try container.decode(UInt64.self)
-    self.init(_attoseconds: _Int128(high: high, low: low))
+    self.init(_high: high, low: low)
   }
-  
+
   @available(SwiftStdlib 5.7, *)
   public func encode(to encoder: Encoder) throws {
     var container = encoder.unkeyedContainer()
@@ -211,7 +212,7 @@ extension Duration: Codable {
 }
 
 @available(SwiftStdlib 5.7, *)
-extension Duration: Hashable { 
+extension Duration: Hashable {
   @available(SwiftStdlib 5.7, *)
   public func hash(into hasher: inout Hasher) {
     hasher.combine(_attoseconds)

stdlib/public/core/Int128.swift.gyb

@@ -149,7 +149,7 @@ extension _${U}Int128: Numeric {
 
     // Is 'source' entirely representable in Low?
     if let low = Low(exactly: source.magnitude) {
-      self.init(source._isNegative ? (~0, ~low &+ 1) : (0, low))
+      self.init(source._isNegative ? (~0, low._twosComplement) : (0, low))
     } else {
       // At this point we know source.bitWidth > High.bitWidth, or else we
       // would've taken the first branch.
@@ -260,7 +260,7 @@ extension _${U}Int128: FixedWidthInteger {
     let isNegative = (self._isNegative != rhs._isNegative)
     let (p, overflow) = self.magnitude.multipliedReportingOverflow(
       by: rhs.magnitude)
-    let r = _Int128(bitPattern: isNegative ? ~(p &- .one) : p)
+    let r = _Int128(bitPattern: isNegative ? p._twosComplement : p)
     return (r, overflow || (isNegative != r._isNegative))
     % else:
     let h1 = self.high.multipliedReportingOverflow(by: rhs.low)
@@ -275,16 +275,39 @@ extension _${U}Int128: FixedWidthInteger {
     % end
   }
 
+  /// Returns the product of this value and the given 64-bit value, along with a
+  /// Boolean value indicating whether overflow occurred in the operation.
+  internal func multipliedReportingOverflow(
+    by other: UInt64
+  ) -> (partialValue: Self, overflow: Bool) {
+    % if signed:
+    let isNegative = self._isNegative
+    let (p, overflow) = self.magnitude.multipliedReportingOverflow(by: other)
+    let r = _Int128(bitPattern: isNegative ? p._twosComplement : p)
+    return (r, overflow || (isNegative != r._isNegative))
+    % else:
+    let h1 = self.high.multipliedReportingOverflow(by: other)
+    let (h2, l) = self.low.multipliedFullWidth(by: other)
+    let high = h1.partialValue.addingReportingOverflow(h2)
+    let overflow = h1.overflow || high.overflow
+    return (Self(high: high.partialValue, low: l), overflow)
+    % end
+  }
+
+  internal func multiplied(by other: UInt64) -> Self {
+    let r = multipliedReportingOverflow(by: other)
+    _precondition(!r.overflow, "Overflow in multiplication")
+    return r.partialValue
+  }
+
   internal func quotientAndRemainder(
     dividingBy other: Self
   ) -> (quotient: Self, remainder: Self) {
     let (q, r) = _wideDivide22(
       self.magnitude.components, by: other.magnitude.components)
     let quotient = Self.Magnitude(q)
     let remainder = Self.Magnitude(r)
-    guard Self.isSigned else {
-      return (Self(quotient), Self(remainder))
-    }
+    % if signed:
     let isNegative = (self.high._isNegative != other.high._isNegative)
     let quotient_ = (isNegative
       ? quotient == Self.min.magnitude ? Self.min : 0 - Self(quotient)
@@ -293,6 +316,9 @@ extension _${U}Int128: FixedWidthInteger {
       ? 0 - Self(remainder)
       : Self(remainder))
     return (quotient_, remainder_)
+    % else:
+    return (quotient, remainder)
+    % end
   }
 
   internal func dividedReportingOverflow(
@@ -514,6 +540,13 @@ extension BinaryInteger {
   fileprivate var _isNegative: Bool { self < Self.zero }
 }
 
+extension FixedWidthInteger {
+  @inline(__always)
+  fileprivate var _twosComplement: Self {
+    ~self &+ 1
+  }
+}
+
 private typealias _Wide2<F: FixedWidthInteger> =
   (high: F, low: F.Magnitude)
 
@@ -725,8 +758,9 @@ private func _wideDivide22<F: FixedWidthInteger & UnsignedInteger>(
 
   // Left shift both rhs and lhs, then divide and right shift the remainder.
   let shift = F.Magnitude(rhs.high.leadingZeroBitCount)
+  let rollover = F.Magnitude(F.bitWidth + F.Magnitude.bitWidth) &- shift
   let rhs = _wideMaskedShiftLeft(rhs, shift)
-  let high = _wideMaskedShiftRight(lhs, F.Magnitude(F.bitWidth) &- shift).low
+  let high = _wideMaskedShiftRight(lhs, rollover).low
   let lhs = _wideMaskedShiftLeft(lhs, shift)
   let (quotient, remainder) = _wideDivide32(
     (F(high), F.Magnitude(lhs.high), lhs.low), by: rhs)
@@ -798,3 +832,44 @@ private func _wideDivide42<F: FixedWidthInteger & UnsignedInteger>(
 
 extension _UInt128: UnsignedInteger {}
 extension _Int128: SignedNumeric, SignedInteger {}
+
+%{
+# This finds the magic numbers for signed division by a constant, following
+# the algorithm described in [Warren 2013, page 212].
+def magic(w, d):
+  nc = (2 ** (w - 1)) // d * d - 1
+  for p in range(2, 2 * w):
+    pp = 2 ** p
+    delta = d - pp % d
+    if pp > nc * delta:
+      m = (pp + delta) // d
+      overflow = m > 2 ** (w - 1) - 1
+      if overflow:
+        m = m - 2 ** w
+      w2 = w // 2
+      ml = m & (2 ** w2 - 1)
+      mh = m >> w2
+      return (mh, ml, p - w, overflow)
+  raise RuntimeError("No magic found")
+}%
+
+% for exp in [18, 15, 12, 9, 6, 3]:
+%   d = 10 ** exp
+%   (mh, ml, s, overflow) = magic(128, d)
+extension _Int128 {
+  internal func dividedBy1e${exp}() -> (quotient: Self, remainder: Self) {
+    let m = _Int128(high: ${mh}, low: ${ml})
+    var q = self.multipliedFullWidth(by: m).high
+    % if overflow:
+    q &+= self
+    % end
+    % if s > 0:
+    q &>>= ${s}
+    % end
+    // Add 1 to q if self is negative
+    q &+= _Int128(bitPattern: _UInt128(bitPattern: self) &>> 127)
+    let r = self &- q &* (${d} as _Int128)
+    return (q, r)
+  }
+}
+% end