Optimize IndexOfAnyAsciiSearcher on Arm64 by tannergooding · Pull Request #126678 · dotnet/runtime

tannergooding · 2026-04-09T00:42:03Z

This improves the codegen of the dedicated Count, IndexOf, and LastIndexOf APIs on Arm64 and correspondingly updates IndexOfAnyAsciiSearcher to consume them instead of ExtractMostSignificantBits

This is notably not strictly the "ideal" codegen as it still does an extra comparison, but that is something we can address in the JIT and should still provide a 5-50% performance increase in workloads using this API as part of their core loop.

tannergooding · 2026-04-09T00:42:26Z

@EgorBot -arm -linux_arm

using System.Buffers;
using BenchmarkDotNet.Attributes;

public class Benchmarks
{
    private static readonly SearchValues<byte> s_controlQuoteBackslash = SearchValues.Create(
        "\u0000\u0001\u0002\u0003\u0004\u0005\u0006\u0007\u0008\u0009\u000A\u000B"u8 +
        "\u000C\u000D\u000E\u000F\u0010\u0011\u0012\u0013\u0014\u0015\u0016\u0017\u0018"u8 +
        "\u0019\u001A\u001B\u001C\u001D\u001E\u001F"u8 + "\""u8 + "\\"u8);

    private byte[] _str = "Product description with some text that is a bit longer than usual\""u8.ToArray();

    [Benchmark]
    public int Medium() => _str.AsSpan().IndexOfAny(s_controlQuoteBackslash);
}

tannergooding · 2026-04-09T00:42:39Z

@EgorBot -linux_azure_arm -arm

using System.Text;
using System.Text.Json;
using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;

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

[MemoryDiagnoser]
public class Benchmarks
{
    // ── TokenSerialization fields ────────────────────────────────────────────
    private List<object> _tokenObjects;
    [ThreadStatic] static Utf8JsonWriter t_writer;
    [ThreadStatic] static MemoryStream t_stream;

    [GlobalSetup]
    public void Setup()
    {
        // TokenSerialization
        _tokenObjects = new List<object>(200);
        for (int i = 0; i < 200; i++)
        {
            if (i % 3 == 0)
                _tokenObjects.Add(GenerateRecordJson(1));
            else
                _tokenObjects.Add(new Dictionary<string, object>
                {
                    ["seq"] = i,
                    ["label"] = $"item_{i}",
                    ["blob"] = new byte[100]
                });
        }
    }

    private static string GenerateRecordJson(int targetSizeKb = 150)
    {
        var sb = new StringBuilder(targetSizeKb * 1024 + 512);
        sb.Append("{");
        sb.Append("\"TypeName\":\"product\",");
        sb.Append("\"CategoryCode\":1,");
        sb.Append("\"Label\":\"Product\",");
        sb.Append("\"IsAction\":false,");
        sb.Append("\"IsActionMember\":false,");
        sb.Append("\"IsTrackingEnabled\":true,");
        sb.Append("\"IsAvailableLocal\":true,");
        sb.Append("\"IsChildRecord\":false,");
        sb.Append("\"IsLinksEnabled\":true,");
        sb.Append("\"IsCustomRecord\":false,");
        sb.Append("\"PrimaryKeyField\":\"productid\",");
        sb.Append("\"PrimaryLabelField\":\"title\",");
        sb.Append("\"Fields\":[");
        int targetBytes = targetSizeKb * 1024;
        int fieldIndex = 0;
        bool firstField = true;
        while (sb.Length < targetBytes - 512)
        {
            if (!firstField) sb.Append(",");
            firstField = false;
            sb.Append("{");
            sb.Append($"\"TypeName\":\"field_{fieldIndex}\",");
            sb.Append($"\"InternalName\":\"Field_{fieldIndex}\",");
            sb.Append($"\"FieldType\":\"String\",");
            sb.Append($"\"Label\":\"Field {fieldIndex}\",");
            sb.Append($"\"MaxSize\":100,");
            sb.Append($"\"IsReadable\":true,");
            sb.Append($"\"IsCreatable\":true,");
            sb.Append($"\"IsUpdatable\":true,");
            sb.Append($"\"IsTrackingEnabled\":false,");
            sb.Append($"\"IsPrimaryKey\":false,");
            sb.Append($"\"IsVirtual\":false,");
            sb.Append($"\"Requirement\":\"None\"");
            sb.Append("}");
            fieldIndex++;
        }
        sb.Append("]");
        sb.Append("}");
        return sb.ToString();
    }

    [Benchmark]
    public void TokenSerialization()
    {
        var stream = t_stream ??= new MemoryStream(64 * 1024);
        stream.Position = 0;
        stream.SetLength(0);
        var writer = t_writer;
        if (writer == null)
        {
            writer = new Utf8JsonWriter(stream, new JsonWriterOptions { SkipValidation = true });
            t_writer = writer;
        }
        else
            writer.Reset(stream);
        writer.WriteStartObject();
        writer.WriteStartArray("Catalog");
        foreach (var token in _tokenObjects)
        {
            if (token is string strToken)
            {
                if (!string.IsNullOrEmpty(strToken))
                    writer.WriteRawValue(strToken);
            }
            else if (token is Dictionary<string, object> dictToken)
            {
                writer.WriteStartObject();
                foreach (var kvp in dictToken)
                {
                    writer.WritePropertyName(kvp.Key);
                    JsonSerializer.Serialize(writer, kvp.Value);
                }
                writer.WriteEndObject();
            }
        }
        writer.WriteEndArray();
        writer.WriteEndObject();
        writer.Flush();
        if (stream.Length == 0) throw new Exception("unreachable");
    }
}

dotnet-policy-service · 2026-04-09T00:43:16Z

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

Copilot

Pull request overview

This PR adds an Arm64/AdvSimd-specific fast-path for computing the first match index from a Vector128<byte> match result in IndexOfAnyAsciiSearcher, aiming to reduce overhead in IndexOfAny-style searches.

Changes:

Extended INegator with IndexOfFirstMatch(Vector128<byte> result) to centralize “find first match” logic.
Implemented an AdvSimd-based first-match index computation for both DontNegate and Negate.
Updated IndexOfAnyResultMapper’s Vector128 code paths to use the new IndexOfFirstMatch helper.

src/libraries/System.Private.CoreLib/src/System/SearchValues/IndexOfAnyAsciiSearcher.cs

EgorBo · 2026-04-09T00:49:28Z

@EgorBot -aws_arm -profiler

using System.Buffers;
using BenchmarkDotNet.Attributes;

public class Benchmarks
{
    private static readonly SearchValues<byte> s_controlQuoteBackslash = SearchValues.Create(
        "\u0000\u0001\u0002\u0003\u0004\u0005\u0006\u0007\u0008\u0009\u000A\u000B"u8 +
        "\u000C\u000D\u000E\u000F\u0010\u0011\u0012\u0013\u0014\u0015\u0016\u0017\u0018"u8 +
        "\u0019\u001A\u001B\u001C\u001D\u001E\u001F"u8 + "\""u8 + "\\"u8);

    private byte[] _str = "Product description with some text that is a bit longer than usual\""u8.ToArray();

    [Benchmark]
    public int Medium() => _str.AsSpan().IndexOfAny(s_controlQuoteBackslash);
}

EgorBo · 2026-04-09T01:35:49Z

@EgorBot -aws_amd -profiler

using System.Text;
using System.Text.Json;
using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;

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

[MemoryDiagnoser]
public class Benchmarks
{
    // ── TokenSerialization fields ────────────────────────────────────────────
    private List<object> _tokenObjects;
    [ThreadStatic] static Utf8JsonWriter t_writer;
    [ThreadStatic] static MemoryStream t_stream;

    [GlobalSetup]
    public void Setup()
    {
        // TokenSerialization
        _tokenObjects = new List<object>(200);
        for (int i = 0; i < 200; i++)
        {
            if (i % 3 == 0)
                _tokenObjects.Add(GenerateRecordJson(1));
            else
                _tokenObjects.Add(new Dictionary<string, object>
                {
                    ["seq"] = i,
                    ["label"] = $"item_{i}",
                    ["blob"] = new byte[100]
                });
        }
    }

    private static string GenerateRecordJson(int targetSizeKb = 150)
    {
        var sb = new StringBuilder(targetSizeKb * 1024 + 512);
        sb.Append("{");
        sb.Append("\"TypeName\":\"product\",");
        sb.Append("\"CategoryCode\":1,");
        sb.Append("\"Label\":\"Product\",");
        sb.Append("\"IsAction\":false,");
        sb.Append("\"IsActionMember\":false,");
        sb.Append("\"IsTrackingEnabled\":true,");
        sb.Append("\"IsAvailableLocal\":true,");
        sb.Append("\"IsChildRecord\":false,");
        sb.Append("\"IsLinksEnabled\":true,");
        sb.Append("\"IsCustomRecord\":false,");
        sb.Append("\"PrimaryKeyField\":\"productid\",");
        sb.Append("\"PrimaryLabelField\":\"title\",");
        sb.Append("\"Fields\":[");
        int targetBytes = targetSizeKb * 1024;
        int fieldIndex = 0;
        bool firstField = true;
        while (sb.Length < targetBytes - 512)
        {
            if (!firstField) sb.Append(",");
            firstField = false;
            sb.Append("{");
            sb.Append($"\"TypeName\":\"field_{fieldIndex}\",");
            sb.Append($"\"InternalName\":\"Field_{fieldIndex}\",");
            sb.Append($"\"FieldType\":\"String\",");
            sb.Append($"\"Label\":\"Field {fieldIndex}\",");
            sb.Append($"\"MaxSize\":100,");
            sb.Append($"\"IsReadable\":true,");
            sb.Append($"\"IsCreatable\":true,");
            sb.Append($"\"IsUpdatable\":true,");
            sb.Append($"\"IsTrackingEnabled\":false,");
            sb.Append($"\"IsPrimaryKey\":false,");
            sb.Append($"\"IsVirtual\":false,");
            sb.Append($"\"Requirement\":\"None\"");
            sb.Append("}");
            fieldIndex++;
        }
        sb.Append("]");
        sb.Append("}");
        return sb.ToString();
    }

    [Benchmark]
    public void TokenSerialization()
    {
        var stream = t_stream ??= new MemoryStream(64 * 1024);
        stream.Position = 0;
        stream.SetLength(0);
        var writer = t_writer;
        if (writer == null)
        {
            writer = new Utf8JsonWriter(stream, new JsonWriterOptions { SkipValidation = true });
            t_writer = writer;
        }
        else
            writer.Reset(stream);
        writer.WriteStartObject();
        writer.WriteStartArray("Catalog");
        foreach (var token in _tokenObjects)
        {
            if (token is string strToken)
            {
                if (!string.IsNullOrEmpty(strToken))
                    writer.WriteRawValue(strToken);
            }
            else if (token is Dictionary<string, object> dictToken)
            {
                writer.WriteStartObject();
                foreach (var kvp in dictToken)
                {
                    writer.WritePropertyName(kvp.Key);
                    JsonSerializer.Serialize(writer, kvp.Value);
                }
                writer.WriteEndObject();
            }
        }
        writer.WriteEndArray();
        writer.WriteEndObject();
        writer.Flush();
        if (stream.Length == 0) throw new Exception("unreachable");
    }
}

Copilot

Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated 6 comments.

src/libraries/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector128.cs

src/libraries/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector64.cs

src/libraries/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector256.cs

src/libraries/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector512.cs

…ndexOf vector APIs

Copilot

Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated 4 comments.

src/libraries/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector64.cs

src/libraries/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector128.cs

tannergooding · 2026-04-11T00:28:30Z

CC. @EgorBo

Faster on Arm64 across the board. On x64, the pattern can sometimes change codegen to use EVEX kmask registers instead and so perf can be slightly slower or faster depending on hardware. It'd be something to handle separately and avoid kmask creation for V128/256 in this scenario, if we care.

EgorBo

I wonder if we could also optimize IndexOfWhereAllBitsSet by just flipping all bits and searching for all zeroes using normal IndexOf. Not fully optimal but better than nothing?

Although, let's see if I can optimize it via #126790

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

tannergooding · 2026-04-11T19:30:42Z

GitHub failed to pickup the applied typo suggestions even though it committed them. Had to force push to get it to pick it up so the merge was actually possible, no changes.

tannergooding · 2026-04-12T01:50:04Z

/ba-g machine timeout and known test errors (#126788, #126641)

Only change since last run was typo fixes in comments

Copilot AI review requested due to automatic review settings April 9, 2026 00:42

github-actions bot added the area-System.Buffers label Apr 9, 2026

dotnet-policy-service bot assigned tannergooding Apr 9, 2026

This was referenced Apr 9, 2026

Benchmarks for dotnet/runtime#126678 (for @tannergooding) EgorBot/Benchmarks#105

Open

Benchmarks for dotnet/runtime#126678 (for @tannergooding) EgorBot/Benchmarks#106

Open

Copilot started reviewing on behalf of tannergooding April 9, 2026 00:43 View session

Copilot AI reviewed Apr 9, 2026

View reviewed changes

src/libraries/System.Private.CoreLib/src/System/SearchValues/IndexOfAnyAsciiSearcher.cs Outdated Show resolved Hide resolved

src/libraries/System.Private.CoreLib/src/System/SearchValues/IndexOfAnyAsciiSearcher.cs Outdated Show resolved Hide resolved

EgorBot mentioned this pull request Apr 9, 2026

Benchmarks for dotnet/runtime#126678 (for @EgorBo) EgorBot/Benchmarks#107

Open

EgorBot mentioned this pull request Apr 9, 2026

Benchmarks for dotnet/runtime#126678 (for @EgorBo) EgorBot/Benchmarks#108

Open

EgorBo mentioned this pull request Apr 9, 2026

JSON Token Serialization performance on .NET 10 with ARM64 is not on par with X64 #126679

Open

EgorBo mentioned this pull request Apr 9, 2026

Add a fast path to IndexOfQuoteOrAnyControlOrBackSlash #126700

Open

tannergooding force-pushed the ascii-search branch from 9dfb601 to 8d992f6 Compare April 9, 2026 18:02

tannergooding changed the title ~~Try to optimize IndexOfAnyAsciiSearcher for finding the first index on Arm64~~ Optimize IndexOfAnyAsciiSearcher on Arm64 Apr 9, 2026

This was referenced Apr 10, 2026

WasmTestOnChrome: can't open file gen-debug-dump-docs.py #126706

Open

wasm lanes fail with log error: Error message: Could not load file or assembly '/System.Private.CoreLib.dll'. The module was expected to contain an assembly manifest. (0x80131018) #126714

Open

tannergooding force-pushed the ascii-search branch from 8d992f6 to 73a99fa Compare April 10, 2026 16:42

Copilot AI review requested due to automatic review settings April 10, 2026 16:42

Copilot started reviewing on behalf of tannergooding April 10, 2026 16:43 View session

Copilot AI reviewed Apr 10, 2026

View reviewed changes

tannergooding force-pushed the ascii-search branch from 73a99fa to e150405 Compare April 10, 2026 18:14

Improve the codegen for Count, IndexOf, and LastIndexOf on Arm64

b2f2866

Update IndexOfAnyAsciiSearcher to use the dedicated IndexOf and LastI…

21503a6

…ndexOf vector APIs

Copilot AI review requested due to automatic review settings April 10, 2026 22:23

tannergooding force-pushed the ascii-search branch from e150405 to 21503a6 Compare April 10, 2026 22:23

Copilot started reviewing on behalf of tannergooding April 10, 2026 22:24 View session

Copilot AI reviewed Apr 10, 2026

View reviewed changes

tannergooding marked this pull request as ready for review April 11, 2026 00:27

tannergooding requested a review from EgorBo April 11, 2026 00:28

This was referenced Apr 11, 2026

Unable to pull image from mcr.microsoft.com #117164

Open

[wasm] OpenQA.Selenium.WebDriverTimeoutException: timeout: Timed out receiving message from renderer #117486

Open

Copilot AI mentioned this pull request Apr 11, 2026

Fix WasmTestOnChrome: exclude browser/wasi from gen-debug-dump-docs.py helix post-command #126789

Open

1 task

EgorBo approved these changes Apr 11, 2026

View reviewed changes

tannergooding enabled auto-merge (squash) April 11, 2026 16:31

Apply suggestions from code review

5474a17

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

tannergooding force-pushed the ascii-search branch from b9d28fe to 5474a17 Compare April 11, 2026 19:29

build-analysis bot mentioned this pull request Apr 12, 2026

Android arm32 device not found (armeabi-v7a architecture unavailable) #125440

Open

tannergooding merged commit 2ebe5d9 into dotnet:main Apr 12, 2026
136 of 152 checks passed

tannergooding deleted the ascii-search branch April 12, 2026 01:50

Conversation

tannergooding commented Apr 9, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

tannergooding commented Apr 9, 2026

Uh oh!

tannergooding commented Apr 9, 2026

Uh oh!

dotnet-policy-service bot commented Apr 9, 2026

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Uh oh!

Uh oh!

Uh oh!

EgorBo commented Apr 9, 2026

Uh oh!

EgorBo commented Apr 9, 2026

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

tannergooding commented Apr 11, 2026

Uh oh!

EgorBo left a comment • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

tannergooding commented Apr 11, 2026

Uh oh!

tannergooding commented Apr 12, 2026

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

tannergooding commented Apr 9, 2026 •

edited

Loading

EgorBo left a comment •

edited

Loading