[interp] Reverse p/invoke

[kg]

• Implements GetStubContext intrinsic in the interpreter
• For interpreted reverse p/invoke stubs, we ensure that TheUMEntryPrestubWorker runs for every invocation so that it can capture the hidden argument in a thread local. The interpreter can then recover the hidden argument from the thread local in order to offer it via GetStubContext later.
• Upon entry to interpreted methods that accept a hidden argument, we store the hidden argument (that was saved by the um entry prestub worker) into a special local that can be read from later by calls to GetStubContext.

Fixes baseservices\threading\regressions\115178 and probably others.

[kg]

I redid part of this from scratch to try and make it less messy and take into account @jkotas 's feedback. Still need to apply the optimization he suggested based on CORJIT_FLAG_PUBLISH_SECRET_PARAM.

[Copilot]

Pull Request Overview

This PR implements reverse P/Invoke support in the CoreCLR interpreter by adding the GetStubContext intrinsic and ensuring proper hidden argument handling for interpreted code. The implementation allows the interpreter to capture and retrieve hidden arguments needed for reverse P/Invoke scenarios.

Key changes:

• Adds GetStubContext intrinsic support to the interpreter instruction set
• Implements thread-local storage for capturing hidden arguments during reverse P/Invoke transitions
• Modifies interpreter frame structure to store hidden arguments for later retrieval

Reviewed Changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/coreclr/vm/prestub.cpp	Adds hidden argument capture logic to ExecuteInterpretedMethod
src/coreclr/vm/interpexec.h	Extends InterpMethodContextFrame with hiddenArgument field
src/coreclr/vm/interpexec.cpp	Implements INTOP_GETSTUBCONTEXT instruction handler
src/coreclr/vm/dllimportcallback.h	Adds interpreter target support to UMEntryThunkData
src/coreclr/vm/dllimportcallback.cpp	Implements thread-local storage for UMEntryThunkData
src/coreclr/interpreter/intrinsics.cpp	Adds GetStubContext to named intrinsics mapping
src/coreclr/interpreter/intops.def	Defines INTOP_GETSTUBCONTEXT instruction
src/coreclr/interpreter/interpretershared.h	Adds hasHiddenArgument flag to InterpMethod
src/coreclr/interpreter/compiler.cpp	Implements GetStubContext intrinsic compilation and adds hasHiddenArgument detection

[kg]

GetInterpreterTarget had STANDARD_VM_CONTRACT which was causing spurious contract failures in JIT\SIMD\Vector3Interop_r\Vector3Interop_r. I've updated it to LIMITED_METHOD_CONTRACT since it's just a field getter.

[jkotas]

Thank you!