矢量化比较泄漏时序信息吗？

Question

我很好奇使用向量运算实现恒定时间比较是否有问题。天真的，似乎绝对没有泄漏任何可操作的信息，因为所有字节都是使用占用相同时间量的操作进行比较的，而与输入无关。但是，代码的矢量化部分和非矢量化部分之间肯定存在可测量的差异，因此有人想知道这是否可以以任何方式滥用...

/// <summary>
/// Compares the contents of two spans for equality in constant time.
/// </summary>
/// <param name="x">The first span that will be compared.</param>
/// <param name="y">The second span that will be compared.</param>
public static bool CompareInConstantTime(ReadOnlySpan<byte> x, ReadOnlySpan<byte> y) {
    var min = ((x.Length > y.Length) ? y.Length : x.Length);
    var max = ((x.Length < y.Length) ? y.Length : x.Length);
    var offset = 0;
    var result = 0;
    var z = (Span<byte>)stackalloc byte[] { byte.MinValue, byte.MaxValue };

    if (Vector.IsHardwareAccelerated) {
        var vectorX = MemoryMarshal.Cast<byte, Vector<byte>>(x.Slice(0, min));
        var vectorY = MemoryMarshal.Cast<byte, Vector<byte>>(y.Slice(0, min));
        var vectorCount = vectorX.Length;
        var vectorResult = Vector<byte>.Zero;

        for (var i = offset; (i < vectorCount); i++) {
            vectorResult |= (vectorX[i] ^ vectorY[i]);
        }

        offset = (Vector<byte>.Count * vectorCount);
        result |= (Vector<byte>.Zero == vectorResult ? byte.MinValue : byte.MaxValue);
    }

    for (var i = offset; (i < min); i++) {
        result |= (x[i] ^ y[i]);
    }

    for (var i = min; (i < max); i++) {
        result |= (z[0] ^ z[1]);
    }

    return (0 == result);
}