[Browser][coreCLR] Enable EventPipe for CoreCLR

[pavelsavara]

This PR enables the EventPipe diagnostics infrastructure for CoreCLR running on single-threaded Browser WASM.
It will probably increase size of the .wasm file.

It is split from #126324 for smaller code review.
Remaining parts are the CPU sampling instrumentation and unit tests.

Changes

Feature enablement

• Removed the FeaturePerfTracing=false override for WASM in clr.featuredefines.props. Previously EventPipe was disabled for CoreCLR on WASM pending single-threaded implementation.
• Updated clrfeatures.cmake to enable FEATURE_PERFTRACING when FEATURE_PERFTRACING_DISABLE_THREADS is set (not just when FEATURE_EVENT_TRACE is set).
• Updated clrdefinitions.cmake to define FEATURE_PERFTRACING in the elseif(FEATURE_PERFTRACING) case (EventPipe without full ETW event tracing).

Single-threaded EventPipe runtime (ep-rt-coreclr.h)

• Added no-op stubs for wait events under PERFTRACING_DISABLE_THREADS — uses INVALID_HANDLE_VALUE as an "allocated" sentinel.
• Added ep_rt_thread_create stub that hits EP_UNREACHABLE.
• Added ep_rt_queue_job implementation for HOST_BROWSER — invokes the job callback inline and reschedules via SystemJS_DiagnosticServerQueueJob if the job returns "not done".
• Made ep_rt_thread_sleep a no-op under PERFTRACING_DISABLE_THREADS.
• Propagated PERFTRACING_DISABLE_THREADS compile definition to eventpipe_objs, eventpipe_gen_objs, cee_wks_core, and clrinterpreter_objects targets.

Eventing / ETW adaptations for Browser

• Stripped LTTng/XplatEventLogger references for HOST_BROWSER/HOST_WASI in generated eventing code (genEventing.py) and runtime (eventtrace.cpp).
• Simplified DOTNET_TRACE_CONTEXT struct for Browser/WASI (EventPipe-only, no LTTng context).
• Updated ETW_EVENT_ENABLED/ETW_TRACING_ENABLED macros to avoid referencing LTTng on Browser/WASI (eventtracebase.h).
• Passed nullptr callback to CreateProvider when FEATURE_EVENT_TRACE is not defined (genEventPipe.py).
• Added EventPipeEventProvider.Callback reverse-call helper for managed provider callbacks (callhelpers-reverse.cpp).
• Added new interp-to-managed call signatures needed by EventPipe (callhelpers-interp-to-managed.cpp).

GC diagnostics deferral

• On single-threaded Browser, ForceGC (triggered by the GCHeapCollect keyword) cannot run synchronously during the provider callback. Deferred to the next event loop turn via SystemJS_DiagnosticServerQueueJob (eventtrace_gcheap.cpp).

GC profiling fix

• Fixed DiagGCEnd to call GCProfileWalkHeap when FEATURE_EVENT_TRACE is defined (not only GC_PROFILING), enabling GC heap walk events on platforms without profiling support (gcenv.ee.cpp).

Build integration

• BrowserWasmApp.CoreCLR.targets: auto-enable native relink (WasmBuildNative=true) when EnableDiagnostics=true.

Test adjustments

• Excluded EventPipeListener test harness and TraceEvent/DiagnosticsClient NuGet packages from the browser test build (these require out-of-process diagnostics, not available in-browser).
• Guarded EventPipeListener usage in TestsWrite.cs / TestsWriteEvent.cs with #if !TARGET_BROWSER.
• Added TARGET_BROWSER define and WASM0066 warning suppression to the test project.

[Copilot]

Pull request overview

This PR enables CoreCLR EventPipe diagnostics for single-threaded Browser WASM by adjusting feature flags, generated eventing code, runtime EventPipe threading abstractions, GC diagnostics behavior, browser native relink behavior, and tracing tests.

Changes:

• Enables CoreCLR perf tracing/EventPipe paths for WASM and adapts generated eventing code to avoid LTTng/XplatEventLogger on Browser/WASI.
• Adds single-threaded EventPipe runtime stubs/queueing behavior and defers Browser GC collection requests through the diagnostic server job queue.
• Updates WASM/browser tracing tests to avoid out-of-process diagnostics dependencies and define browser-specific test constants.

Reviewed changes

Copilot reviewed 22 out of 22 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/mono/browser/build/BrowserWasmApp.CoreCLR.targets	Forces native relink when diagnostics are enabled for CoreCLR browser apps.
src/libraries/System.Diagnostics.Tracing/tests/System.Diagnostics.Tracing.Tests.csproj	Adjusts browser/android target detection and excludes EventPipeListener/package dependencies on browser.
src/libraries/System.Diagnostics.Tracing/tests/BasicEventSourceTest/TestsWriteEvent.cs	Guards EventPipeListener usage out of browser builds.
src/libraries/System.Diagnostics.Tracing/tests/BasicEventSourceTest/TestsWrite.cs	Guards EventPipeListener usage out of browser builds.
src/coreclr/vm/wks/CMakeLists.txt	Propagates single-threaded perf tracing define to workstation GC VM objects.
src/coreclr/vm/wasm/entrypoints.h	Declares the browser diagnostic server job queue entrypoint for native CoreCLR code.
src/coreclr/vm/wasm/callhelpers-reverse.cpp	Adds reverse thunk support for EventPipeEventProvider.Callback.
src/coreclr/vm/wasm/callhelpers-interp-to-managed.cpp	Adds interpreter-to-managed thunk signatures needed by EventPipe event callbacks.
src/coreclr/vm/gcenv.ee.cpp	Allows GC heap walking for EventPipe builds without profiler support.
src/coreclr/vm/eventtrace.cpp	Adds Browser/WASI EventPipe-only provider contexts and excludes XplatEventLogger initialization.
src/coreclr/vm/eventtrace_gcheap.cpp	Defers browser diagnostic ForceGC requests through the event-loop job queue.
src/coreclr/vm/eventtrace_bulktype.cpp	Avoids firing Xplat bulk statics events on Browser/WASI while keeping EventPipe emission.
src/coreclr/vm/eventing/eventpipe/ep-rt-coreclr.h	Adds single-threaded wait-event/thread/job behavior for CoreCLR EventPipe.
src/coreclr/vm/eventing/eventpipe/CMakeLists.txt	Defines perf tracing symbols for EventPipe object targets and propagates single-threaded mode.
src/coreclr/vm/eventing/CMakeLists.txt	Makes eventing header dependencies conditional and preserves EventPipe subdirectory inclusion.
src/coreclr/scripts/genEventPipe.py	Emits nullptr provider callbacks when CoreCLR EventTrace is unavailable.
src/coreclr/scripts/genEventing.py	Generates Browser/WASI-safe EventPipe-only eventing structures and guards Xplat event emission.
src/coreclr/interpreter/CMakeLists.txt	Propagates single-threaded perf tracing define to interpreter objects.
src/coreclr/inc/eventtracebase.h	Defines Browser/WASI EventPipe-only tracing macros and excludes XplatEventLogger classes.
src/coreclr/clrfeatures.cmake	Enables EventTrace for browser and perf tracing when single-threaded perf tracing is requested.
src/coreclr/clrdefinitions.cmake	Defines FEATURE_PERFTRACING without requiring FEATURE_EVENT_TRACE and adds cross-component dummy headers target.
src/coreclr/clr.featuredefines.props	Removes the WASM managed FeaturePerfTracing=false override.

[maraf]

Parts I'm familiar with looks good to me 👍

[Copilot]

Pull request overview

Copilot reviewed 22 out of 22 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 22 out of 22 changed files in this pull request and generated 1 comment.