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Use PopCount intrinsic (#5715)

This commit is contained in:
Ben Adams 2018-12-26 18:03:36 +00:00 committed by Pavel Krymets
parent 4d0ff9967a
commit b87ac1d652
1 changed files with 19 additions and 9 deletions
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28
src/Servers/Kestrel/Core/src/Internal/Http/HttpHeaders.cs
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@ -6,6 +6,7 @@ using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Runtime.Intrinsics.X86;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Infrastructure;
using Microsoft.Extensions.Primitives;
@ -122,20 +123,29 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
return StringValues.Concat(existing, append);
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
protected static int BitCount(long value)
{
// see https://github.com/dotnet/corefx/blob/5965fd3756bc9dd9c89a27621eb10c6931126de2/src/System.Reflection.Metadata/src/System/Reflection/Internal/Utilities/BitArithmetic.cs
int SoftwareFallback(ulong v)
{
// see https://github.com/dotnet/corefx/blob/5965fd3756bc9dd9c89a27621eb10c6931126de2/src/System.Reflection.Metadata/src/System/Reflection/Internal/Utilities/BitArithmetic.cs
const ulong Mask01010101 = 0x5555555555555555UL;
const ulong Mask00110011 = 0x3333333333333333UL;
const ulong Mask00001111 = 0x0F0F0F0F0F0F0F0FUL;
const ulong Mask00000001 = 0x0101010101010101UL;
const ulong Mask01010101 = 0x5555555555555555UL;
const ulong Mask00110011 = 0x3333333333333333UL;
const ulong Mask00001111 = 0x0F0F0F0F0F0F0F0FUL;
const ulong Mask00000001 = 0x0101010101010101UL;
var v = (ulong)value;
v = v - ((v >> 1) & Mask01010101);
v = (v & Mask00110011) + ((v >> 2) & Mask00110011);
return (int)(unchecked(((v + (v >> 4)) & Mask00001111) * Mask00000001) >> 56);
}
v = v - ((v >> 1) & Mask01010101);
v = (v & Mask00110011) + ((v >> 2) & Mask00110011);
return (int)(unchecked(((v + (v >> 4)) & Mask00001111) * Mask00000001) >> 56);
if (Popcnt.X64.IsSupported)
{
return (int)Popcnt.X64.PopCount((ulong)value);
}
return SoftwareFallback((ulong)value);
}
protected virtual int GetCountFast()