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Fixing Span IndexOf vectorization. #17500

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ahsonkhan merged 3 commits into from
Mar 25, 2017
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Fixing Span IndexOf vectorization. #17500

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22e4c23
Fixing Span IndexOf vectorization.
ahsonkhan Mar 24, 2017
4c51297
Addressing PR comments
ahsonkhan Mar 24, 2017
bae24f6
Changing >= to > since we changed what nLength is.
ahsonkhan Mar 25, 2017
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6 changes: 3 additions & 3 deletions src/System.Memory/src/System/SpanHelpers.byte.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -61,7 +61,7 @@ public static unsafe int IndexOf(ref byte searchSpace, byte value, int length)
unchecked
{
int unaligned = (int)(byte*)Unsafe.AsPointer(ref searchSpace) & (Vector<byte>.Count - 1);
nLength = (IntPtr)(uint)unaligned;
nLength = (IntPtr)(uint)((Vector<byte>.Count - unaligned) & (Vector<byte>.Count - 1));
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@benaadams benaadams Mar 25, 2017

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Actually, unaligned will always be < Vector<byte>.Count so (from mask on line above) the & part isn't needed?

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@ahsonkhan ahsonkhan Mar 25, 2017 •
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What if unaligned == 0?
If we don't do the &, nLength would equal Vector<byte>.Count rather than 0.

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@benaadams benaadams Mar 25, 2017

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True

}
}
SequentialScan:
Expand Down Expand Up @@ -122,7 +122,7 @@ public static unsafe int IndexOf(ref byte searchSpace, byte value, int length)
{
goto NotFound;
}
nLength = (IntPtr)(uint)(length - Vector<byte>.Count);
nLength = (IntPtr)(uint)((length - (uint)index) & ~(Vector<byte>.Count - 1));
// Get comparision Vector
Vector<byte> vComparision = GetVector(value);
while ((byte*)nLength > (byte*)index)
Expand All @@ -139,7 +139,7 @@ public static unsafe int IndexOf(ref byte searchSpace, byte value, int length)
goto VectorFound;
}

if ((int)(byte*)index > length)
if ((int)(byte*)index >= length)
{
goto NotFound;
}
Expand Down