BitCount.swift

//===--- BitCount.swift ---------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2021 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
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//

// This test checks performance of Swift bit count.
// and mask operator.
// rdar://problem/22151678
import TestsUtils

publicletbenchmarks=
BenchmarkInfo(
 name:"BitCount",
 runFunction: run_BitCount,
 tags:[.validation,.algorithm])

func countBitSet(_ num:Int)->Int{
letbits=MemoryLayout<Int>.size *8
varcnt:Int=0
varmask:Int=1
for_in0...bits {
if num & mask !=0{
 cnt +=1
}
 mask <<=1
}
return cnt
}

@inline(never)
publicfunc run_BitCount(_ n:Int){
varsum=0
for_in1...1000*n {
 // Check some results.
 sum = sum &+countBitSet(getInt(1))
&+countBitSet(getInt(2))
&+countBitSet(getInt(2457))
}
check(sum ==8*1000* n)
}