+ vs extend() performance

swift_+_vs_extend

import Foundation

func perf(text: String, closure: () -> ()) {
    let measurementStart = NSDate();
    
    closure()
    
    let measurementStop = NSDate();
    let executionTime = measurementStop.timeIntervalSinceDate(measurementStart)
    
    println("\(text) \(executionTime)");
}

let message = [UInt8](count: 1024 * 1024, repeatedValue: 7)
var out = [UInt8]()
out.reserveCapacity(message.count)


perf("     +") { () -> () in
    out += [1]
}

perf("extend") { () -> () in
    out.extend([1])
}

rdar://20178254