ByteSwap.swift

//===--- ByteSwap.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 byte swap.
// rdar://problem/22151907

import TestsUtils

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

// a naive O(n) implementation of byteswap.
@inline(never)
func byteswap_n(_ a:UInt64)->UInt64{
return((a &0x00000000000000FF)&<<56) |
((a &0x000000000000FF00)&<<40) |
((a &0x0000000000FF0000)&<<24) |
((a &0x00000000FF000000)&<<8) |
((a &0x000000FF00000000)&>>8) |
((a &0x0000FF0000000000)&>>24) |
((a &0x00FF000000000000)&>>40) |
((a &0xFF00000000000000)&>>56)
}

// a O(logn) implementation of byteswap.
@inline(never)
func byteswap_logn(_ a:UInt64)->UInt64{
vara= a
 a =(a &0x00000000FFFFFFFF) << 32 | (a &0xFFFFFFFF00000000) >> 32
 a =(a &0x0000FFFF0000FFFF) << 16 | (a &0xFFFF0000FFFF0000) >> 16
 a =(a &0x00FF00FF00FF00FF) << 8 | (a &0xFF00FF00FF00FF00) >> 8
return a
}

@inline(never)
publicfunc run_ByteSwap(_ n:Int){
vars:UInt64=0
for_in1...10000*n {
 // Check some results.
letx:UInt64=UInt64(getInt(0))
 s = s &+byteswap_logn(byteswap_n(x &+2457))
&+byteswap_logn(byteswap_n(x &+9129))
&+byteswap_logn(byteswap_n(x &+3333))
}
check(s ==(2457&+9129&+3333)&*10000&* n)
}