Remove unsafe code from System.Collections.BitArray

[EgorBo]

Note

This PR is AI-generated.

No diffs

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[EgorBo]

@MihuBot

[Copilot]

Pull request overview

This PR updates the BitArray(bool[] values) constructor in System.Private.CoreLib to avoid reinterpreting the bool[] backing storage via Unsafe.As<bool, byte> by instead operating over a ReadOnlySpan<byte> obtained from MemoryMarshal.AsBytes.

Changes:

• Convert the input bool[] to ReadOnlySpan<byte> and use it as the SIMD input source.
• Replace Vector*.LoadUnsafe(ref, offset) loops with Vector*.Create(ReadOnlySpan<byte>) plus span slicing to advance through the input.
• Adjust loop structure from indexed for loops to while (valuesAsBytes.Length >= ...) loops.

[EgorBo]

Note

AI-generated benchmark.

@EgorBot -arm -amd

using System;
using System.Collections;
using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;

BenchmarkSwitcher.FromAssembly(typeof(Bench).Assembly).Run(args);

public class Bench
{
    private bool[] _values = default!;

    [Params(64, 256, 1024, 16384)]
    public int Length { get; set; }

    [GlobalSetup]
    public void Setup()
    {
        var rng = new Random(42);
        _values = new bool[Length];
        for (int i = 0; i < Length; i++)
            _values[i] = rng.Next(2) == 0;
    }

    [Benchmark]
    public BitArray Construct() => new BitArray(_values);
}

[EgorBo]

It's fully safe to bitcast Span<bool> to Span<byte>