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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift Collections open source project
//
// Copyright (c) 2022 - 2024 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
//
//===----------------------------------------------------------------------===//
%{
from gyb_utils import *
}%
${autogenerated_warning()}
% for modifier in visibility_levels:
${visibility_boilerplate(modifier)}
extension FixedWidthInteger {
@inlinable @inline(__always)
internal var _nonzeroBitCount: Self {
Self(truncatingIfNeeded: nonzeroBitCount)
}
@inlinable @inline(__always)
${modifier} func _rank(ofBit bit: UInt) -> Int {
assert(bit < Self.bitWidth)
let mask: Self = (1 &<< bit) &- 1
return (self & mask).nonzeroBitCount
}
}
extension UInt {
@_effects(releasenone)
${"@usableFromInline" if modifier != "public" else "//@usableFromInline" }
${modifier} func _bit(ranked n: Int) -> UInt? {
// FIXME: Use bit deposit instruction when available (PDEP on Intel).
assert(UInt.bitWidth == 64 || UInt.bitWidth == 32,
"Unsupported UInt bitWidth")
var shift: Self = 0
var n = Self(truncatingIfNeeded: n)
if MemoryLayout<UInt>.size == 8 {
let c32 = (self & 0xFFFFFFFF)._nonzeroBitCount
if n >= c32 {
shift &+= 32
n &-= c32
}
} else {
assert(MemoryLayout<Self>.size == 4, "Unknown platform")
}
let c16 = ((self &>> shift) & 0xFFFF)._nonzeroBitCount
if n >= c16 {
shift &+= 16
n &-= c16
}
let c8 = ((self &>> shift) & 0xFF)._nonzeroBitCount
if n >= c8 {
shift &+= 8
n &-= c8
}
let c4 = ((self &>> shift) & 0xF)._nonzeroBitCount
if n >= c4 {
shift &+= 4
n &-= c4
}
let c2 = ((self &>> shift) & 0x3)._nonzeroBitCount
if n >= c2 {
shift &+= 2
n &-= c2
}
let c1 = (self &>> shift) & 0x1
if n >= c1 {
shift &+= 1
n &-= c1
}
guard n == 0 && (self &>> shift) & 0x1 == 1 else { return nil }
return shift
}
}
extension UInt32 {
// Returns the position of the `n`th set bit in `self`, i.e., the bit with
// rank `n`.
@_effects(releasenone)
${"@usableFromInline" if modifier != "public" else "//@usableFromInline" }
${modifier} func _bit(ranked n: Int) -> UInt? {
// FIXME: Use bit deposit instruction when available (PDEP on Intel).
assert(n >= 0 && n < Self.bitWidth)
var shift: Self = 0
var n = Self(truncatingIfNeeded: n)
let c16 = (self & 0xFFFF)._nonzeroBitCount
if n >= c16 {
shift = 16
n -= c16
}
let c8 = ((self &>> shift) & 0xFF)._nonzeroBitCount
if n >= c8 {
shift &+= 8
n -= c8
}
let c4 = ((self &>> shift) & 0xF)._nonzeroBitCount
if n >= c4 {
shift &+= 4
n -= c4
}
let c2 = ((self &>> shift) & 0x3)._nonzeroBitCount
if n >= c2 {
shift &+= 2
n -= c2
}
let c1 = (self &>> shift) & 0x1
if n >= c1 {
shift &+= 1
n -= c1
}
guard n == 0, (self &>> shift) & 0x1 == 1 else { return nil }
return UInt(truncatingIfNeeded: shift)
}
}
extension UInt16 {
// Returns the position of the `n`th set bit in `self`, i.e., the bit with
// rank `n`.
@_effects(releasenone)
${"@usableFromInline" if modifier != "public" else "//@usableFromInline" }
${modifier} func _bit(ranked n: Int) -> UInt? {
// FIXME: Use bit deposit instruction when available (PDEP on Intel).
assert(n >= 0 && n < Self.bitWidth)
var shift: Self = 0
var n = Self(truncatingIfNeeded: n)
let c8 = ((self &>> shift) & 0xFF)._nonzeroBitCount
if n >= c8 {
shift &+= 8
n -= c8
}
let c4 = ((self &>> shift) & 0xF)._nonzeroBitCount
if n >= c4 {
shift &+= 4
n -= c4
}
let c2 = ((self &>> shift) & 0x3)._nonzeroBitCount
if n >= c2 {
shift &+= 2
n -= c2
}
let c1 = (self &>> shift) & 0x1
if n >= c1 {
shift &+= 1
n -= c1
}
guard n == 0, (self &>> shift) & 0x1 == 1 else { return nil }
return UInt(truncatingIfNeeded: shift)
}
}
% end
${visibility_boilerplate("end")}
|
