Improve IndexOf(char, OrdinalIgnoreCase)

[EgorBo]

trafficstars

A similar trick is used for IndexOf(string, OrdinalIgnoreCase) see here.

Benchmark:

using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;

BenchmarkSwitcher.FromAssembly(typeof(Benchmarks).Assembly).Run(args);

public class Benchmarks
{
    const string TestStr =
        ".NET Runtime uses third-party libraries or other resources that may be" +
        " distributed under licenses different than the.NET Runtime software.";

    [Benchmark]
    public int IndexOfDash() => TestStr.IndexOf('-', StringComparison.OrdinalIgnoreCase);

    [Benchmark]
    public int IndexOfL() => TestStr.IndexOf('L', StringComparison.OrdinalIgnoreCase);

    [Benchmark]
    public int IndexOfZ() => TestStr.IndexOf('z', StringComparison.OrdinalIgnoreCase);
}

Method	Job	Toolchain	Mean	Ratio
IndexOfDash	Job-GBURIF	\Core_Root_base\corerun.exe	16.125 ns	1.00
IndexOfDash	Job-DLWGWE	\Core_Root\corerun.exe	7.084 ns	0.44
IndexOfL	Job-GBURIF	\Core_Root_base\corerun.exe	14.907 ns	1.00
IndexOfL	Job-DLWGWE	\Core_Root\corerun.exe	5.630 ns	0.38
IndexOfZ	Job-GBURIF	\Core_Root_base\corerun.exe	16.809 ns	1.00
IndexOfZ	Job-DLWGWE	\Core_Root\corerun.exe	8.337 ns	0.50

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Issue Details

---

A similar trick is used for IndexOf(string, OrdinalIgnoreCase) see here.

Benchmark:

using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;

BenchmarkSwitcher.FromAssembly(typeof(Benchmarks).Assembly).Run(args);

public class Benchmarks
{
    const string TestStr =
        ".NET Runtime uses third-party libraries or other resources that may be" +
        " distributed under licenses different than the.NET Runtime software.";

    [Benchmark]
    public int IndexOfDash() => TestStr.IndexOf('-', StringComparison.OrdinalIgnoreCase);

    [Benchmark]
    public int IndexOfL() => TestStr.IndexOf('L', StringComparison.OrdinalIgnoreCase);

    [Benchmark]
    public int IndexOfZ() => TestStr.IndexOf('z', StringComparison.OrdinalIgnoreCase);
}

Method	Job	Toolchain	Mean	Ratio
IndexOfDash	Job-GBURIF	\Core_Root_base\corerun.exe	16.125 ns	1.00
IndexOfDash	Job-DLWGWE	\Core_Root\corerun.exe	7.084 ns	0.44
IndexOfL	Job-GBURIF	\Core_Root_base\corerun.exe	14.907 ns	1.00
IndexOfL	Job-DLWGWE	\Core_Root\corerun.exe	5.630 ns	0.38
IndexOfZ	Job-GBURIF	\Core_Root_base\corerun.exe	16.809 ns	1.00
IndexOfZ	Job-DLWGWE	\Core_Root\corerun.exe	8.337 ns	0.50

Author:	EgorBo
Assignees:	EgorBo
Labels:	area-System.Runtime
Milestone:	-

[EgorBo]

Failure is https://github.com/dotnet/runtime/issues/73247