Inline GC handle write barrier

[Copilot]

Summary

• Inline the GC handle write-barrier worker into its callers without changing the GC/EE interface.
• Avoid the handle-type lookup when the assigned target is in generation zero.
• Relates to [Perf] Linux/x64: 2 Regressions on 7/5/2026 4:58:39 PM +00:00 #130698.

Validation

• Built the CoreCLR GC native target successfully.
• Built libraries successfully.
• Full CoreCLR Release build reached the changed GC objects successfully but failed later on pre-existing JIT identifier errors in instrsxarch.h.
• The focused GCHandle.Target test could not be built because test dependency assets have not been generated.

Performance

• EgorBot measurement requested for Linux x64 and macOS ARM64.

Note

This pull request description was generated by AI/Copilot.

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[Copilot]

Pull request overview

This PR refactors the CoreCLR GC handle write-barrier by moving the HndWriteBarrierWorker implementation into handletable.inl (so it can be inlined into its callers) and introduces a fast-path that avoids the handle-type lookup when the assigned target is in generation 0. This targets reduced overhead in hot handle assignment paths while keeping the GC/EE interface shape unchanged.

Changes:

• Inline HndWriteBarrierWorker into src/coreclr/gc/handletable.inl and remove the out-of-line implementation from handletable.cpp.
• Add an early-return fast-path in the worker to skip HandleFetchType(handle) when GetConvertedGeneration(value) is 0.
• Move/adjust declarations (GetConvertedGeneration, HandleFetchType) to be available to the inlined implementation and update includes accordingly.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
src/coreclr/gc/handletablepriv.h	Removes now-unneeded forward declarations previously used by the out-of-line worker.
src/coreclr/gc/handletable.inl	Adds the inlined HndWriteBarrierWorker implementation and updates HndAssignHandle to call it directly.
src/coreclr/gc/handletable.h	Adds handletableconstants.h include and exposes needed non-DAC prototypes for the inlined worker.
src/coreclr/gc/handletable.cpp	Removes the out-of-line HndWriteBarrierWorker implementation (now provided inline).

[Copilot]

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated no new comments.

Suppressed comments (1)

src/coreclr/gc/handletable.inl:68

• The comment describing async pinned handle behavior has a few grammar/wording issues (e.g., missing space after //, “need”/“consider”). Updating it will make the intent clearer without changing behavior.

        //OverlappedData need special treatment: because all user data pointed by it needs to be reported by this handle,
        //its age is consider to be min age of the user data, to be simple, we just make it 0

[Copilot]

Pull request overview

Copilot reviewed 10 out of 10 changed files in this pull request and generated 1 comment.

Suppressed comments (2)

src/coreclr/gc/handletablepriv.h:171

• HandleFetchType in handletable.inl reads the block type via raw uint8_t* indexing (segment[HANDLE_SEGMENT_BLOCK_TYPE_OFFSET + uBlock]). The existing offsetof static_assert guards the offset, but the implementation also assumes rgBlockType elements are 1 byte. Adding a size check here makes that assumption explicit and prevents silent breakage if the field type ever changes.

static_assert(offsetof(_TableSegmentHeader, rgBlockType) == HANDLE_SEGMENT_BLOCK_TYPE_OFFSET);

src/coreclr/gc/handletable.inl:43

• New code in handletable.inl uses C-style casts when deriving segment pointers (e.g., (uint8_t*)((uintptr_t)handle & HANDLE_SEGMENT_ALIGN_MASK)), while nearby code already uses reinterpret_cast. This is easy to fix and aligns with the repo's native guidance to prefer C++ casts.

    uint8_t* barrier = (uint8_t*)((uintptr_t)handle & HANDLE_SEGMENT_ALIGN_MASK);
    _ASSERTE(barrier);

    uintptr_t offset = (uintptr_t)handle & HANDLE_SEGMENT_CONTENT_MASK;
    _ASSERTE(offset >= HANDLE_HEADER_SIZE);

[Copilot]

Pull request overview

Copilot reviewed 15 out of 15 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 15 out of 15 changed files in this pull request and generated no new comments.

Suppressed comments (1)

src/coreclr/gc/handletable.inl:256

• The #endif comment doesn’t match the corresponding #ifndef DACCESS_COMPILE (repo native guidelines request matching #endif comments). This makes preprocessor blocks harder to audit in low-level code.

#endif // DACCESS_COMPILE

[Copilot]

Pull request overview

Copilot reviewed 15 out of 15 changed files in this pull request and generated no new comments.

[jkotas]

@EgorBot -linux_x64

using System.Runtime.InteropServices;
using BenchmarkDotNet.Attributes;

public class Bench
{
    [Benchmark]
    public void GCHandle()
    {
        using (var hnd = new PinnedGCHandle<string>("Hello"))
        {
        }
    }
}

[EgorBo]

@EgorBot -linux_x64 -profiler

using System.Runtime.InteropServices;
using BenchmarkDotNet.Attributes;

public class Bench
{
    [Benchmark]
    public void GCHandle()
    {
        using (var hnd = new PinnedGCHandle<string>("Hello"))
        {
        }
    }
}

[jkotas]

@copilot Make sure HndAssignHandle is inlined

[Copilot]

Addressed in 9ef9134 by changing HndAssignHandle to FORCEINLINE. Verified ./build.sh clr.runtime and ./build.sh clr.runtime -c Release; the Release handle-table/GC objects no longer contain an out-of-line HndAssignHandle symbol.

Note

This reply was generated by AI/Copilot.

[Copilot]

Pull request overview

Copilot reviewed 15 out of 15 changed files in this pull request and generated no new comments.