Improve IndexOf(char, OrdinalIgnoreCase)

[EgorBo]

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

[dotnet-issue-labeler]

I couldn't figure out the best area label to add to this PR. If you have write-permissions please help me learn by adding exactly one area label.

[stephentoub]

Thanks.

[ghost]

Tagging subscribers to this area: @dotnet/area-system-runtime
See info in area-owners.md if you want to be subscribed.

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 #73247