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Vectorise string.Replace(char, char) #279

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merged 2 commits into from
Nov 27, 2019
Merged

Vectorise string.Replace(char, char) #279

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47f108c
Vectorise string.Replace(char, char)
Gnbrkm41 Nov 26, 2019
97b17ec
Add missing using for System.Numerics
Gnbrkm41 Nov 26, 2019
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87 changes: 40 additions & 47 deletions src/libraries/System.Private.CoreLib/src/System/String.Manipulation.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@
using System.Collections.Generic;
using System.Diagnostics;
using System.Globalization;
using System.Numerics;
using System.Text;
using Internal.Runtime.CompilerServices;

Expand Down Expand Up @@ -1055,63 +1056,55 @@ public string Replace(char oldChar, char newChar)
if (oldChar == newChar)
return this;

unsafe
{
int remainingLength = Length;

fixed (char* pChars = &_firstChar)
{
char* pSrc = pChars;
int firstIndex = IndexOf(oldChar);

while (remainingLength > 0)
{
if (*pSrc == oldChar)
{
break;
}
if (firstIndex < 0)
return this;

remainingLength--;
pSrc++;
}
}
int remainingLength = Length - firstIndex;
string result = FastAllocateString(Length);

if (remainingLength == 0)
return this;
int copyLength = firstIndex;

string result = FastAllocateString(Length);

fixed (char* pChars = &_firstChar)
{
fixed (char* pResult = &result._firstChar)
{
int copyLength = Length - remainingLength;
// Copy the characters already proven not to match.
if (copyLength > 0)
{
Buffer.Memmove(ref result._firstChar, ref _firstChar, (uint)copyLength);
}

// Copy the characters already proven not to match.
if (copyLength > 0)
{
wstrcpy(pResult, pChars, copyLength);
}
// Copy the remaining characters, doing the replacement as we go.
ref ushort pSrc = ref Unsafe.Add(ref Unsafe.As<char, ushort>(ref _firstChar), copyLength);
ref ushort pDst = ref Unsafe.Add(ref Unsafe.As<char, ushort>(ref result._firstChar), copyLength);

// Copy the remaining characters, doing the replacement as we go.
char* pSrc = pChars + copyLength;
char* pDst = pResult + copyLength;
if (Vector.IsHardwareAccelerated && remainingLength >= Vector<ushort>.Count)
{
Vector<ushort> oldChars = new Vector<ushort>(oldChar);
Vector<ushort> newChars = new Vector<ushort>(newChar);

do
{
char currentChar = *pSrc;
if (currentChar == oldChar)
currentChar = newChar;
*pDst = currentChar;

remainingLength--;
pSrc++;
pDst++;
} while (remainingLength > 0);
}
do
{
Vector<ushort> original = Unsafe.ReadUnaligned<Vector<ushort>>(ref Unsafe.As<ushort, byte>(ref pSrc));
Vector<ushort> equals = Vector.Equals(original, oldChars);
Vector<ushort> results = Vector.ConditionalSelect(equals, newChars, original);
Unsafe.WriteUnaligned(ref Unsafe.As<ushort, byte>(ref pDst), results);

pSrc = ref Unsafe.Add(ref pSrc, Vector<ushort>.Count);
pDst = ref Unsafe.Add(ref pDst, Vector<ushort>.Count);
remainingLength -= Vector<ushort>.Count;
}
while (remainingLength >= Vector<ushort>.Count);
}

return result;
for (; remainingLength > 0; remainingLength--)
{
ushort currentChar = pSrc;
pDst = currentChar == oldChar ? newChar : currentChar;

pSrc = ref Unsafe.Add(ref pSrc, 1);
pDst = ref Unsafe.Add(ref pDst, 1);
}

return result;
}

public string Replace(string oldValue, string? newValue)
Expand Down