Enable SymbolicRegexNode.IsNullableFor fast path to inline

[stephentoub]

Method	Toolchain	Mean	Error	StdDev	Ratio	RatioSD	Allocated
IsMatch	\main\corerun.exe	10.639 ms	0.0453 ms	0.0402 ms	1.00	0.00	-
IsMatch	\pr\corerun.exe	9.190 ms	0.1800 ms	0.2143 ms	0.87	0.02	-

using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Diagnosers;
using BenchmarkDotNet.Running;
using System.Linq;
using System.Text.RegularExpressions;

[MemoryDiagnoser]
public partial class Program
{
    public static void Main(string[] args)
    {
        BenchmarkSwitcher.FromAssembly(typeof(Program).Assembly).Run(args);
    }

    private Regex _regex = new Regex("[a-q][^u-z]{13}x", RegexOptions.NonBacktracking);
    private string _input = string.Concat(Enumerable.Repeat("abcdefghijklz", 100_000));

    [Benchmark]
    public bool IsMatch() => _regex.IsMatch(_input);
}

[ghost]

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

Issue Details

---

Method	Toolchain	Mean	Error	StdDev	Ratio	RatioSD	Allocated
IsMatch	\main\corerun.exe	10.639 ms	0.0453 ms	0.0402 ms	1.00	0.00	-
IsMatch	\pr\corerun.exe	9.190 ms	0.1800 ms	0.2143 ms	0.87	0.02	-

using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Diagnosers;
using BenchmarkDotNet.Running;
using System.Linq;
using System.Text.RegularExpressions;

[MemoryDiagnoser]
public partial class Program
{
    public static void Main(string[] args)
    {
        BenchmarkSwitcher.FromAssembly(typeof(Program).Assembly).Run(args);
    }

    private Regex _regex = new Regex("[a-q][^u-z]{13}x", RegexOptions.NonBacktracking);
    private string _input = string.Concat(Enumerable.Repeat("abcdefghijklz", 100_000));

    [Benchmark]
    public bool IsMatch() => _regex.IsMatch(_input);
}

Author:	stephentoub
Assignees:	-
Labels:	area-System.Text.RegularExpressions
Milestone:	7.0.0

[joperezr]

Code change looks good to me.