mirrors/Ryujinx
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

Optimize the LowestBitSet method

Browse source
This commit is contained in:
gdkchan 2019-05-28 23:06:55 -03:00
parent 8e6ee56200
commit 7d29ae0c4c
1 changed files with 31 additions and 8 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

39
ARMeilleure/Common/BitUtils.cs
View file

@ -1,22 +1,45 @@
using System.Runtime.CompilerServices;
namespace ARMeilleure.Common
{
static class BitUtils
{
private const int deBrujinSequence = 0x77cb531;
private static int[] deBrujinLbsLut;
static BitUtils()
{
deBrujinLbsLut = new int[32];
for (int index = 0; index < deBrujinLbsLut.Length; index++)
{
uint lutIndex = (uint)(deBrujinSequence * (1 << index)) >> 27;
deBrujinLbsLut[lutIndex] = index;
}
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
public static int LowestBitSet(int value)
{
for (int bit = 0; bit < 32; bit++)
if (value == 0)
{
if (((value >> bit) & 1) != 0)
{
return bit;
}
return -1;
}
return -1;
int lsb = value & -value;
return deBrujinLbsLut[(uint)(deBrujinSequence * lsb) >> 27];
}
public static int HighestBitSet(int value)
{
if (value == 0)
{
return -1;
}
for (int bit = 31; bit >= 0; bit--)
{
if (((value >> bit) & 1) != 0)
@ -28,9 +51,9 @@ namespace ARMeilleure.Common
return -1;
}
private static readonly sbyte[] HbsNibbleTbl = { -1, 0, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3 };
private static readonly sbyte[] HbsNibbleLut = { -1, 0, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3 };
public static int HighestBitSetNibble(int value) => HbsNibbleTbl[value & 0b1111];
public static int HighestBitSetNibble(int value) => HbsNibbleLut[value & 0b1111];
public static long Replicate(long bits, int size)
{