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Unroll String.Equals for constant input [0..16] length #64821

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EgorBo wants to merge 21 commits into from
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Unroll String.Equals for constant input [0..16] length #64821

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65d29fb
Unroll Equals too
EgorBo Feb 5, 2022
11941a4
remove irrelevant comment
EgorBo Feb 5, 2022
aef78ef
formatting
EgorBo Feb 5, 2022
60fb02f
better codegen
EgorBo Feb 5, 2022
23f5a29
Reformat
EgorBo Feb 5, 2022
6bdd6b0
Inliner's friendly version
EgorBo Feb 5, 2022
3257a51
Clean up
EgorBo Feb 5, 2022
fb9b881
Fix SIMD impl, clean up. Remove StartsWith for now - leaving it up-fo…
EgorBo Feb 5, 2022
3097c5b
Clean up again
EgorBo Feb 5, 2022
05ccb49
Address feedback
EgorBo Feb 5, 2022
b838215
Update src/libraries/System.Private.CoreLib/src/System/String.Compari…
EgorBo Feb 5, 2022
9817514
Add a comment
EgorBo Feb 5, 2022
3def0ac
Merge branch 'unroll-startswith' of https://github.com/EgorBo/runtime…
EgorBo Feb 5, 2022
49871fd
simple change, big codegen diff O_o
EgorBo Feb 5, 2022
147647d
Update src/libraries/System.Private.CoreLib/src/System/String.Compari…
EgorBo Feb 5, 2022
6f82123
address feedback
EgorBo Feb 5, 2022
4b7b810
Clean up
EgorBo Feb 5, 2022
8cc4dc2
only fold index expression in global morph
EgorBo Feb 5, 2022
d195951
Merge branch 'main' of https://github.com/dotnet/runtime into unroll-…
EgorBo Feb 9, 2022
e0bd4ba
Add tests
EgorBo Feb 10, 2022
a27a975
do 8-char longs strings via SIMD path - it's smaller
EgorBo Feb 10, 2022
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@EgorBo
EgorBo committed Feb 5, 2022
commit 23f5a29f10794af8f5cdc5ef01b1e7a2bba93b7b
87 changes: 41 additions & 46 deletions src/libraries/System.Private.CoreLib/src/System/String.Comparison.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -742,53 +742,48 @@ static bool EqualsUnrolled(string? a, string b)
return EqualsInternal(a, b);
}

/*
// // Vectorized unrolling demo:

// if (RuntimeHelpers.IsKnownConstant(b) && b != null && b.Length >= 8 && b.Length <= 16) // TODO: 16
// {
// return EqualsUnrolled_8_to_16_Vector128(a, b);
// }

// [MethodImpl(MethodImplOptions.AggressiveInlining)]
// static bool EqualsUnrolled_8_to_16_Vector128(string? a, string b)
// {
// // if both are constants - EqualsInternal will handle it just fine
// if (a == null)
// {
// return false; // b is not null
// }

// // if both are constants - EqualsInternal will handle it just fine
// if (RuntimeHelpers.IsKnownConstant(a))
// {
// return EqualsInternal(a, b);
// }

// Vector128<ushort> constV1 = Vector128.Create(b[0], b[1], b[2], b[3], b[4], b[5], b[6], b[7]);
// Vector128<ushort> constV2 = default;

// if (b.Length == 8) constV2 = constV1;
// if (b.Length == 9) constV2 = Vector128.Create(b[1], b[2], b[3], b[4], b[5], b[6], b[7], b[8]);
// if (b.Length == 10) constV2 = Vector128.Create(b[2], b[3], b[4], b[5], b[6], b[7], b[8], b[9]);
// if (b.Length == 11) constV2 = Vector128.Create(b[3], b[4], b[5], b[6], b[7], b[8], b[9], b[10]);
// if (b.Length == 12) constV2 = Vector128.Create(b[4], b[5], b[6], b[7], b[8], b[9], b[10], b[11]);
// if (b.Length == 13) constV2 = Vector128.Create(b[5], b[6], b[7], b[8], b[9], b[10], b[11], b[12];
// if (b.Length == 14) constV2 = Vector128.Create(b[6], b[7], b[8], b[9], b[10], b[11], b[10], b[13]);
// if (b.Length == 15) constV2 = Vector128.Create(b[7], b[8], b[9], b[10], b[11], b[10], b[11]), b[14]);
// if (b.Length == 16) constV2 = Vector128.Create(b[8], b[9], b[10], b[11], b[10], b[11]), b[11]), b[15]);

// // TODO: len == 8 and len == 16 can be special cased

// return ((Unsafe.ReadUnaligned<Vector128<ushort>>(ref Unsafe.As<char, byte>(ref a._firstChar)) ^ constV1) |
// (Unsafe.ReadUnaligned<Vector128<ushort>>(ref Unsafe.As<char, byte>(ref Unsafe.Add(ref a._firstChar, a.Length - 16))) ^ constV2)) ==
// Vector128<ushort>.Zero;
// }

// Vectorized unrolling demo:

if (RuntimeHelpers.IsKnownConstant(b) && b != null && b.Length >= 8 && b.Length <= 10) // TODO: 16
{
return EqualsUnrolled_8_to_16_Vector128(a, b);
}

[MethodImpl(MethodImplOptions.AggressiveInlining)]
static bool EqualsUnrolled_8_to_16_Vector128(string? a, string b)
{
// if both are constants - EqualsInternal will handle it just fine
if (a == null)
{
return false; // b is not null
}

// if both are constants - EqualsInternal will handle it just fine
if (RuntimeHelpers.IsKnownConstant(a))
{
return EqualsInternal(a, b);
}

Vector128<ushort> v1 = Unsafe.ReadUnaligned<Vector128<ushort>>(
ref Unsafe.As<char, byte>(ref a._firstChar));
Vector128<ushort> v2 = Unsafe.ReadUnaligned<Vector128<ushort>>(
ref Unsafe.As<char, byte>(ref Unsafe.Add(ref a._firstChar, a.Length - 16)));

Vector128<ushort> constV1 = Vector128.Create(b[0], b[1], b[2], b[3], b[4], b[5], b[6], b[7]);
Vector128<ushort> constV2 = default;

if (b.Length == 8) constV2 = constV1; // TODO: for len=8 we don't need the 2nd vector at all
if (b.Length == 9) constV2 = Vector128.Create(b[1], b[2], b[3], b[4], b[5], b[6], b[7], b[8]);
if (b.Length == 10) constV2 = Vector128.Create(b[2], b[3], b[4], b[5], b[6], b[7], b[8], b[9]);
if (b.Length == 11) constV2 = Vector128.Create(b[3], b[4], b[5], b[6], b[7], b[8], b[9], b[10]);
if (b.Length == 12) constV2 = Vector128.Create(b[4], b[5], b[6], b[7], b[8], b[9], b[10], b[11]);
if (b.Length == 13) constV2 = Vector128.Create(b[5], b[6], b[7], b[8], b[9], b[10], b[11], b[12];
if (b.Length == 14) constV2 = Vector128.Create(b[6], b[7], b[8], b[9], b[10], b[11], b[10], b[13]);
if (b.Length == 15) constV2 = Vector128.Create(b[7], b[8], b[9], b[10], b[11], b[10], b[11]), b[14]);

// 16 can be done via a single Vector256
if (b.Length == 16) constV2 = Vector128.Create(b[8], b[9], b[10], b[11], b[10], b[11]), b[11]), b[15]);

return ((v1 ^ constV1) | (v2 ^ constV2)) == Vector128<ushort>.Zero;
}
*/
#endif
return EqualsInternal(a, b);

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