Convert constructor invocations from the runtime to use UnmanagedCallersOnly

[jkoritzinsky]

This PR moves the class constructor and instance constructor invocations from within the runtime to use the UnmanagedCallersOnly pattern established with #123864 to invoke the constructors.

Contributes to #123864.

As this PR removes all usages of CATCH_HANDLER_FOUND_NOTIFICATION_CALLSITE and PREPARE_NONVIRTUAL_CALLSITE_USING_METHODDESC , these pieces of infrastructure are removed as well.

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[Copilot]

Pull request overview

This PR continues the migration away from MethodDescCallSite / CallDescrWorker-style VM-to-managed invocation, switching class constructor and default instance constructor calls over to the UnmanagedCallersOnly reverse P/Invoke pattern (per #123864). It also removes the now-unused CATCH_HANDLER_FOUND_NOTIFICATION_CALLSITE / PREPARE_NONVIRTUAL_CALLSITE_USING_METHODDESC infrastructure.

Changes:

• Route MethodTable::RunClassInitEx (.cctor invocation) through a new InitHelpers.CallClassConstructor [UnmanagedCallersOnly] entrypoint and UnmanagedCallersOnlyCaller.
• Route default constructor invocations through a new RuntimeHelpers.CallDefaultConstructor [UnmanagedCallersOnly] entrypoint and UnmanagedCallersOnlyCaller.
• Remove debugger notification dispatch flag and wrapper logic from DispatchCallSimple/call helper macros.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/coreclr/vm/methodtable.cpp	Switches class constructor invocation to UnmanagedCallersOnlyCaller.
src/coreclr/vm/corelib.h	Adds CoreLib binder entries for the new UCO-managed helpers.
src/coreclr/vm/cominterfacemarshaler.cpp	Switches extensible RCW default ctor invocation to UCO path.
src/coreclr/vm/callhelpers.h	Removes catch-handler-found notification flag/macro; retains UCO caller helper.
src/coreclr/vm/callhelpers.cpp	Removes debugger wrapper dispatch path; switches default ctor helper to UCO path.
src/coreclr/System.Private.CoreLib/.../RuntimeHelpers.CoreCLR.cs	Adds [UnmanagedCallersOnly] method for default ctor invocation.
src/coreclr/System.Private.CoreLib/.../InitHelpers.cs	Adds [UnmanagedCallersOnly] method for class constructor invocation.

[jkotas]

I think the right solution here is to do the allocation in managed code as well.

We would have to use reflection (Activator.CreateInstance) for that. We may find surprising cycles between reflection and EEException::CreateThrowable where these constructors are called from in the VM. EEException::CreateThrowable is several layers lower than reflection. I think it is ok to leave it as is for this PR.

[AaronRobinsonMSFT]

I think the right solution here is to do the allocation in managed code as well.

We would have to use reflection (Activator.CreateInstance) for that. We may find surprising cycles between reflection and EEException::CreateThrowable where these constructors are called from in the VM. EEException::CreateThrowable is several layers lower than reflection. I think it is ok to leave it as is for this PR.

Okay.

[Copilot]

Pull request overview

Copilot reviewed 12 out of 12 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 12 out of 12 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 12 out of 12 changed files in this pull request and generated 1 comment.

Comments suppressed due to low confidence (1)

src/coreclr/vm/excep.cpp:8286

• The comment at line 8285-8286, "since we are here because of a cross AD reraise of the original exception," is now stale. With the removal of AppDomainTransitionExceptionFilter and the updated assertion at line 8281 (_ASSERTE((fIsThreadAbortException || fIsPreallocatedOOMExceptionForTA) && pUEWatsonBucketTracker->CapturedForThreadAbort())), the if (!fIsThreadAbortException) branch can only be reached in the fIsPreallocatedOOMExceptionForTA case—not an AD transition. The comment should be updated to reflect the remaining scenario (preallocated OOM exception during thread abort).

            if (!fIsThreadAbortException)
            {
                // The watson bucket tracker for the exceptiong being raised should be empty at this point
                // since we are here because of a cross AD reraise of the original exception.

[Copilot]

Pull request overview

Copilot reviewed 12 out of 12 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 12 out of 12 changed files in this pull request and generated 2 comments.

[Copilot]

Corrected spelling of 'Incase' to 'In case'.

Suggested change

	// Incase of an OOM, we may not have an IP in the Watson bucket tracker.
	// In case of an OOM, we may not have an IP in the Watson bucket tracker.

[Copilot]

Wb_CapturedAtReflectionInvocation was previously 4 (bit 2) and is now renumbered to 2 (bit 1), which conflicts with the now-removed Wb_CapturedAtADTransition = 2. While Wb_CapturedAtADTransition has been deleted, the renumbering means this flag now occupies bit 1 instead of bit 2. Any serialized or persisted m_DebugFlags values (e.g., in crash dumps) will be misinterpreted. More critically, if m_DebugFlags is ever checked for a combined bitmask at existing call sites that have not been updated, the semantics will silently change. The value should remain 4 to preserve stable bit-flag semantics, or the removal of the gap should be explicitly justified.

Suggested change

	Wb_CapturedAtReflectionInvocation = 2
	Wb_CapturedAtReflectionInvocation = 4