Intrinsify Span.Slice(int,int) for Span[X..]

[EgorBo]

Closes #121987
Closes #122042

Just an experiment, if dotnet/roslyn#81485 lands, we can delete/ignore this (or intrinsify Slice anyway since it's a popular operation in general)

[EgorBo]

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[EgorBo]

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[En3Tho]

@EgorBo I do believe that Slice(x, y) should be quite common in the real world too. So I don't think it's entirely about Roslyn.
A quick example would be something like this I guess:

static ReadOnlySpan<byte> Foo(ReadOnlySpan<byte> data)
{
    if (data.Length < sizeof(ushort))
        throw new ArgumentException("Data is too short", nameof(data));

    var header = MemoryMarshal.Read<ushort>(data);

    if (data.Length < sizeof(ushort) + header)
    {
        throw new ArgumentException("Data is too short for header", nameof(data));
    }

    return data.Slice(sizeof(ushort), header);
}

Ideally there should be no bound checks inserted by the jit. This can be extrapolated further to include multiple data sections/slices

[En3Tho]

Top regression method is funny :) Reducing those throw calls to 1 could easily result in an improvement

[EgorBo]

@EgorBo I do believe that Slice(x, y) should be quite common in the real world too

It is, but this PR was targeting a very specific pattern emitted by span[X..] syntax as it was difficult to properly handle it downstream.

Top regression method is funny

No clue why those tails were not merged

[EgorBo]

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[En3Tho]

@EgorBo I wonder if results are much better now after your tail merge fix

[EgorBo]

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[En3Tho]

I wonder if there is a conceptual difference between
call [rax]System.ThrowHelper:ThrowArgumentOutOfRangeException()
and
call CORINFO_HELP_THROW_ARGUMENTOUTOFRANGEEXCEPTION
?

[EgorBo]

I wonder if there is a conceptual difference between call [rax]System.ThrowHelper:ThrowArgumentOutOfRangeException() and call CORINFO_HELP_THROW_ARGUMENTOUTOFRANGEEXCEPTION ?

Should be the same thing

[En3Tho]

Interesting. If you look at System.IO.Compression.ZipGenericExtraField:WriteBlockCore(System.Span1[byte]):this (top regression method) - this PR adds call CORINFO_HELP_THROW_ARGUMENTOUTOFRANGEEXCEPTION in addition to existing call [rax]System.ThrowHelper:ThrowArgumentOutOfRangeException()

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[EgorBo]

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Draft Pull Request was automatically closed for 30 days of inactivity. Please let us know if you'd like to reopen it.