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Restore BitArray constructor performance #131833

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Restore BitArray constructor performance #131833

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43 changes: 23 additions & 20 deletions src/libraries/System.Private.CoreLib/src/System/Collections/BitArray.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -172,10 +172,11 @@ private static byte[] CreateArray(ReadOnlySpan<byte> bytes, out int bitLength)
throw new ArgumentException(SR.Format(SR.Argument_ArrayTooLarge, BitsPerByte), nameof(bytes));
}

bitLength = bytes.Length * BitsPerByte;
byte[] array = AllocateByteArray(bitLength);
int length = bytes.Length * BitsPerByte;
byte[] array = AllocateByteArray(length);

bytes.CopyTo(array);
bitLength = length;
Comment on lines +175 to +179
return array;
}

Expand All @@ -192,7 +193,8 @@ public BitArray(bool[] values)
{
ArgumentNullException.ThrowIfNull(values);

_array = CreateArray(values, out _bitLength);
_array = CreateArray(values);
_bitLength = values.Length;
}

/// <summary>
Expand All @@ -205,15 +207,15 @@ public BitArray(bool[] values)
/// </remarks>
public BitArray(ReadOnlySpan<bool> values)
{
_array = CreateArray(values, out _bitLength);
_array = CreateArray(values);
_bitLength = values.Length;
}

private static byte[] CreateArray(ReadOnlySpan<bool> values, out int bitLength)
private static byte[] CreateArray(ReadOnlySpan<bool> values)
{
bitLength = values.Length;
byte[] array = AllocateByteArray(bitLength);
byte[] array = AllocateByteArray(values.Length);

uint i = 0;
int i = 0;

if (!BitConverter.IsLittleEndian || values.Length < Vector256<byte>.Count)
{
Expand All @@ -234,8 +236,8 @@ private static byte[] CreateArray(ReadOnlySpan<bool> values, out int bitLength)
Vector512<byte> isFalse = Vector512.Equals(vector, Vector512<byte>.Zero);

ulong result = isFalse.ExtractMostSignificantBits();
Unsafe.WriteUnaligned(ref Unsafe.Add(ref arrayRef, sizeof(ulong) * (i / 64u)), ~result);
i += (uint)Vector512<byte>.Count;
Unsafe.WriteUnaligned(ref Unsafe.Add(ref arrayRef, sizeof(ulong) * (i / 64)), ~result);
i += Vector512<byte>.Count;
valuesAsBytes = valuesAsBytes.Slice(Vector512<byte>.Count);
}
}
Expand All @@ -247,8 +249,8 @@ private static byte[] CreateArray(ReadOnlySpan<bool> values, out int bitLength)
Vector256<byte> isFalse = Vector256.Equals(vector, Vector256<byte>.Zero);

uint result = isFalse.ExtractMostSignificantBits();
Unsafe.WriteUnaligned(ref Unsafe.Add(ref arrayRef, sizeof(uint) * (i / 32u)), ~result);
i += (uint)Vector256<byte>.Count;
Unsafe.WriteUnaligned(ref Unsafe.Add(ref arrayRef, sizeof(uint) * (i / 32)), ~result);
i += Vector256<byte>.Count;
valuesAsBytes = valuesAsBytes.Slice(Vector256<byte>.Count);
}
}
Expand All @@ -265,20 +267,20 @@ private static byte[] CreateArray(ReadOnlySpan<bool> values, out int bitLength)
uint upperResult = upperIsFalse.ExtractMostSignificantBits();

Unsafe.WriteUnaligned(
ref Unsafe.Add(ref arrayRef, sizeof(uint) * (i / 32u)),
ref Unsafe.Add(ref arrayRef, sizeof(uint) * (i / 32)),
~((upperResult << 16) | lowerResult));
i += (uint)Vector128<byte>.Count * 2u;
i += Vector128<byte>.Count * 2;
valuesAsBytes = valuesAsBytes.Slice(Vector128<byte>.Count * 2);
}
}

Remainder:
for (; i < (uint)values.Length; i++)
for (; i < values.Length; i++)
{
if (values[(int)i])
if (values[i])
{
(uint byteIndex, uint bitOffset) = Math.DivRem(i, BitsPerByte);
array[byteIndex] |= (byte)(1 << (int)bitOffset);
(int byteIndex, int bitOffset) = Math.DivRem(i, BitsPerByte);
array[byteIndex] |= (byte)(1 << bitOffset);
}
}

Expand Down Expand Up @@ -333,8 +335,8 @@ private static byte[] CreateArray(ReadOnlySpan<int> values, out int bitLength)
throw new ArgumentException(SR.Format(SR.Argument_ArrayTooLarge, BitsPerInt32), nameof(values));
}

bitLength = values.Length * BitsPerInt32;
byte[] array = AllocateByteArray(bitLength);
int length = values.Length * BitsPerInt32;
byte[] array = AllocateByteArray(length);

if (BitConverter.IsLittleEndian)
{
Expand All @@ -345,6 +347,7 @@ private static byte[] CreateArray(ReadOnlySpan<int> values, out int bitLength)
BinaryPrimitives.ReverseEndianness(values, MemoryMarshal.Cast<byte, int>((Span<byte>)array));
}

bitLength = length;
return array;
}

Expand Down