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Optimize Span.Slice by using IsKnownConstant for start = 0 #69193

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Optimize Span.Slice by using IsKnownConstant for start = 0 #69193

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12 changes: 10 additions & 2 deletions src/libraries/System.Private.CoreLib/src/System/Memory.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -249,8 +249,16 @@ public Memory<T> Slice(int start, int length)
{
#if TARGET_64BIT
// See comment in Span<T>.Slice for how this works.
if ((ulong)(uint)start + (ulong)(uint)length > (ulong)(uint)_length)
ThrowHelper.ThrowArgumentOutOfRangeException();
if (RuntimeHelpers.IsKnownConstant(start) && start == 0)
{
if ((uint)length > (uint)_length)
ThrowHelper.ThrowArgumentOutOfRangeException();
}
else
{
if ((ulong)(uint)start + (ulong)(uint)length > (ulong)(uint)_length)
ThrowHelper.ThrowArgumentOutOfRangeException();
}
#else
if ((uint)start > (uint)_length || (uint)length > (uint)(_length - start))
ThrowHelper.ThrowArgumentOutOfRangeException();
Expand Down
24 changes: 20 additions & 4 deletions src/libraries/System.Private.CoreLib/src/System/MemoryExtensions.cs
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Expand Up @@ -145,8 +145,16 @@ public static ReadOnlySpan<char> AsSpan(this string? text, int start, int length

#if TARGET_64BIT
// See comment in Span<T>.Slice for how this works.
if ((ulong)(uint)start + (ulong)(uint)length > (ulong)(uint)text.Length)
ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.start);
if (RuntimeHelpers.IsKnownConstant(start) && start == 0)
{
if ((uint)length > (uint)text.Length)
ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.start);
}
else
{
if ((ulong)(uint)start + (ulong)(uint)length > (ulong)(uint)text.Length)
ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.start);
}
#else
if ((uint)start > (uint)text.Length || (uint)length > (uint)(text.Length - start))
ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.start);
Expand Down Expand Up @@ -227,8 +235,16 @@ public static ReadOnlyMemory<char> AsMemory(this string? text, int start, int le

#if TARGET_64BIT
// See comment in Span<T>.Slice for how this works.
if ((ulong)(uint)start + (ulong)(uint)length > (ulong)(uint)text.Length)
ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.start);
if (RuntimeHelpers.IsKnownConstant(start) && start == 0)
{
if ((uint)length > (uint)text.Length)
ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.start);
}
else
{
if ((ulong)(uint)start + (ulong)(uint)length > (ulong)(uint)text.Length)
ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.start);
}
#else
if ((uint)start > (uint)text.Length || (uint)length > (uint)(text.Length - start))
ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.start);
Expand Down
24 changes: 20 additions & 4 deletions src/libraries/System.Private.CoreLib/src/System/ReadOnlyMemory.cs
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Expand Up @@ -76,8 +76,16 @@ public ReadOnlyMemory(T[]? array, int start, int length)
}
#if TARGET_64BIT
// See comment in Span<T>.Slice for how this works.
if ((ulong)(uint)start + (ulong)(uint)length > (ulong)(uint)array.Length)
ThrowHelper.ThrowArgumentOutOfRangeException();
if (RuntimeHelpers.IsKnownConstant(start) && start == 0)
{
if ((uint)length > (uint)array.Length)
ThrowHelper.ThrowArgumentOutOfRangeException();
}
else
{
if ((ulong)(uint)start + (ulong)(uint)length > (ulong)(uint)array.Length)
ThrowHelper.ThrowArgumentOutOfRangeException();
}
#else
if ((uint)start > (uint)array.Length || (uint)length > (uint)(array.Length - start))
ThrowHelper.ThrowArgumentOutOfRangeException();
Expand Down Expand Up @@ -178,8 +186,16 @@ public ReadOnlyMemory<T> Slice(int start, int length)
{
#if TARGET_64BIT
// See comment in Span<T>.Slice for how this works.
if ((ulong)(uint)start + (ulong)(uint)length > (ulong)(uint)_length)
ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.start);
if (RuntimeHelpers.IsKnownConstant(start) && start == 0)
{
if ((uint)length > (uint)_length)
ThrowHelper.ThrowArgumentOutOfRangeException();
}
else
{
if ((ulong)(uint)start + (ulong)(uint)length > (ulong)(uint)_length)
ThrowHelper.ThrowArgumentOutOfRangeException();
}
#else
if ((uint)start > (uint)_length || (uint)length > (uint)(_length - start))
ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.start);
Expand Down
24 changes: 20 additions & 4 deletions src/libraries/System.Private.CoreLib/src/System/ReadOnlySpan.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -68,8 +68,16 @@ public ReadOnlySpan(T[]? array, int start, int length)
}
#if TARGET_64BIT
// See comment in Span<T>.Slice for how this works.
if ((ulong)(uint)start + (ulong)(uint)length > (ulong)(uint)array.Length)
ThrowHelper.ThrowArgumentOutOfRangeException();
if (RuntimeHelpers.IsKnownConstant(start) && start == 0)
{
if ((uint)length > (uint)array.Length)
ThrowHelper.ThrowArgumentOutOfRangeException();
}
else
{
if ((ulong)(uint)start + (ulong)(uint)length > (ulong)(uint)array.Length)
ThrowHelper.ThrowArgumentOutOfRangeException();
}
#else
if ((uint)start > (uint)array.Length || (uint)length > (uint)(array.Length - start))
ThrowHelper.ThrowArgumentOutOfRangeException();
Expand Down Expand Up @@ -361,8 +369,16 @@ public ReadOnlySpan<T> Slice(int start, int length)
{
#if TARGET_64BIT
// See comment in Span<T>.Slice for how this works.
if ((ulong)(uint)start + (ulong)(uint)length > (ulong)(uint)_length)
ThrowHelper.ThrowArgumentOutOfRangeException();
if (RuntimeHelpers.IsKnownConstant(start) && start == 0)
{
if ((uint)length > (uint)_length)
ThrowHelper.ThrowArgumentOutOfRangeException();
}
else
{
if ((ulong)(uint)start + (ulong)(uint)length > (ulong)(uint)_length)
ThrowHelper.ThrowArgumentOutOfRangeException();
}
#else
if ((uint)start > (uint)_length || (uint)length > (uint)(_length - start))
ThrowHelper.ThrowArgumentOutOfRangeException();
Expand Down
25 changes: 21 additions & 4 deletions src/libraries/System.Private.CoreLib/src/System/Span.cs
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Expand Up @@ -73,8 +73,16 @@ public Span(T[]? array, int start, int length)
ThrowHelper.ThrowArrayTypeMismatchException();
#if TARGET_64BIT
// See comment in Span<T>.Slice for how this works.
if ((ulong)(uint)start + (ulong)(uint)length > (ulong)(uint)array.Length)
ThrowHelper.ThrowArgumentOutOfRangeException();
if (RuntimeHelpers.IsKnownConstant(start) && start == 0)
{
if ((uint)length > (uint)array.Length)
ThrowHelper.ThrowArgumentOutOfRangeException();
}
else
{
if ((ulong)(uint)start + (ulong)(uint)length > (ulong)(uint)array.Length)
ThrowHelper.ThrowArgumentOutOfRangeException();
}
#else
if ((uint)start > (uint)array.Length || (uint)length > (uint)(array.Length - start))
ThrowHelper.ThrowArgumentOutOfRangeException();
Expand Down Expand Up @@ -413,8 +421,17 @@ public Span<T> Slice(int start, int length)
// of this is that if either input is negative or if the input sum overflows past Int32.MaxValue,
// that information is captured correctly in the comparison against the backing _length field.
// We don't use this same mechanism in a 32-bit process due to the overhead of 64-bit arithmetic.
if ((ulong)(uint)start + (ulong)(uint)length > (ulong)(uint)_length)
ThrowHelper.ThrowArgumentOutOfRangeException();
// We special-case "start == 0" to optimize codegen since the pattern Slice(0, ...) is so common.
if (RuntimeHelpers.IsKnownConstant(start) && start == 0)
{
if ((uint)length > (uint)_length)
ThrowHelper.ThrowArgumentOutOfRangeException();
}
else
{
if ((ulong)(uint)start + (ulong)(uint)length > (ulong)(uint)_length)
ThrowHelper.ThrowArgumentOutOfRangeException();
}
#else
if ((uint)start > (uint)_length || (uint)length > (uint)(_length - start))
ThrowHelper.ThrowArgumentOutOfRangeException();
Expand Down