Compile runtime async versions of synchronous task-returning methods

[jakobbotsch]

Instead of delegating from runtime async callable thunks to the original task returning methods this PR compiles a fully separate runtime async version. The JIT gets passed the IL of the synchronous task-returning method and is then responsible for adapting that to fit with the async variant. It does so by adding a (guaranteed) optimization to make tail calls in the synchronous task-returning methods into runtime async calls, and by otherwise introducing an async call to AsyncHelpers.TransparentAwaitWithResult around the task that would have otherwise been returned.

Fix#115771

[Copilot]

Pull request overview

This PR extends the JIT↔EE async infrastructure so the JIT can compile a dedicated “runtime async version” of synchronous Task/ValueTask-returning methods, including a tail-position optimization that turns eligible tail calls/returns into runtime-async awaits.

Changes:

• Adds a new JIT↔EE interface API (getAwaitReturnCall) and plumbs it through SuperPMI and generated wrappers/shims.
• Updates CoreCLR async thunk IL generation and AsyncHelpers to separate “suspend” helpers from typed TransparentAwait(...) helpers used by the JIT.
• Updates the JIT importer to recognize “async-version tail await” patterns and to wrap async-version returns in an await via the new EE callback.

Reviewed changes

Copilot reviewed 33 out of 33 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
src/tests/async/reflection/reflection.cs	Disables several assertions related to reflection/stack behavior for await-on-task-returning paths.
src/coreclr/vm/prestub.cpp	Adjusts IL header retrieval logic for async variant methods.
src/coreclr/vm/method.hpp	Changes IL-header eligibility rules for async/thunk/return-dropping methods; exposes GetAsyncThunkResultTypeSig.
src/coreclr/vm/metasig.h	Adds metasig entries for Task/ValueTask TransparentAwait helper signatures.
src/coreclr/vm/jitinterface.h	Adds helper declarations related to runtime lookup computation for new await-return support.
src/coreclr/vm/jitinterface.cpp	Implements getAwaitReturnCall and runtime-lookup computation for generic await helpers; sets CORINFO_ASYNC_VERSION for applicable methods.
src/coreclr/vm/corelib.h	Adds/updates CoreLibBinder entries for new suspend/await AsyncHelpers methods with proper signatures.
src/coreclr/vm/asyncthunks.cpp	Switches thunk-emitted calls from TransparentAwait* to TransparentSuspendFor* helpers.
src/coreclr/tools/superpmi/superpmi/icorjitinfo.cpp	Records/replays the new getAwaitReturnCall API for SuperPMI.
src/coreclr/tools/superpmi/superpmi-shim-simple/icorjitinfo_generated.cpp	Forwards the new API in the simple shim.
src/coreclr/tools/superpmi/superpmi-shim-counter/icorjitinfo_generated.cpp	Counts/forwards the new API in the counter shim.
src/coreclr/tools/superpmi/superpmi-shim-collector/icorjitinfo.cpp	Records the new API in the collector shim.
src/coreclr/tools/superpmi/superpmi-shared/spmirecordhelper.h	Makes lookup restore helpers take const& and updates corresponding implementations.
src/coreclr/tools/superpmi/superpmi-shared/methodcontext.h	Adds recording/replay plumbing for getAwaitReturnCall.
src/coreclr/tools/superpmi/superpmi-shared/methodcontext.cpp	Implements record/dump/replay for getAwaitReturnCall.
src/coreclr/tools/superpmi/superpmi-shared/lwmlist.h	Registers the new lightweight-map packet for GetAwaitReturnCall.
src/coreclr/tools/superpmi/superpmi-shared/agnostic.h	Adds agnostic structs for CORINFO_LOOKUP* and the await-return result payload.
src/coreclr/tools/Common/TypeSystem/IL/Stubs/AsyncThunks.cs	Updates IL stub emitter to use TransparentSuspendFor* helper names.
src/coreclr/tools/Common/JitInterface/ThunkGenerator/ThunkInput.txt	Adds the new interface method to thunk generation input.
src/coreclr/tools/Common/JitInterface/CorInfoImpl.cs	Adds a stub managed implementation of getAwaitReturnCall for the managed JIT interface.
src/coreclr/tools/Common/JitInterface/CorInfoImpl_generated.cs	Adds unmanaged callback plumbing for getAwaitReturnCall.
src/coreclr/tools/aot/jitinterface/jitinterface_generated.h	Adds the new callback and wrapper method to the AOT jitinterface wrapper.
src/coreclr/System.Private.CoreLib/src/System/Runtime/CompilerServices/AsyncHelpers.CoreCLR.cs	Renames “suspend” helpers and adds typed TransparentAwait(...) overloads used by the JIT.
src/coreclr/jit/importercalls.cpp	Adds tail-await handling for async-version tail-await prefix and blocks inlining of async-version callees.
src/coreclr/jit/importer.cpp	Adds async-version tail-call recognition, wraps async-version returns in an await via getAwaitReturnCall, and introduces impWrapTopOfStackInAwait.
src/coreclr/jit/ICorJitInfo_wrapper_generated.hpp	Adds wrapper forwarding for getAwaitReturnCall.
src/coreclr/jit/ICorJitInfo_names_generated.h	Adds name entry for getAwaitReturnCall.
src/coreclr/jit/fginline.cpp	Minor whitespace change near async flag handling for inlinee compilation.
src/coreclr/jit/compiler.h	Introduces PREFIX_IS_ASYNC_VERSION_TAIL_AWAIT, impWrapTopOfStackInAwait, and compIsAsyncVersion().
src/coreclr/jit/compiler.cpp	Adds verbose printing when compiling an async-version method.
src/coreclr/inc/jiteeversionguid.h	Updates JIT↔EE version GUID due to interface change.
src/coreclr/inc/icorjitinfoimpl_generated.h	Adds getAwaitReturnCall override to the generated ICorJitInfo impl header.
src/coreclr/inc/corinfo.h	Adds CORINFO_ASYNC_VERSION and the new ICorStaticInfo::getAwaitReturnCall method.

[Copilot]

Pull request overview

Copilot reviewed 32 out of 32 changed files in this pull request and generated 6 comments.

[jakobbotsch]

Another pattern we may want to recognize:

runtime/src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/MaxAsync.cs

Lines 24 to 38 in b129b7c

	publicstaticValueTask<TSource?>MaxAsync<TSource>(
	thisIAsyncEnumerable<TSource>source,
	IComparer<TSource>?comparer=null,
	CancellationTokencancellationToken=default)
	{
	ArgumentNullException.ThrowIfNull(source);
	comparer??=Comparer<TSource>.Default;
	// Special-case float/double/float?/double? to maintain compatibility
	// with System.Linq.Enumerable implementations.
	#pragma warning disable CA2012// Use ValueTasks correctly
	if(typeof(TSource)==typeof(float)&&comparer==Comparer<TSource>.Default)
	{
	return(ValueTask<TSource?>)(object)MaxAsync((IAsyncEnumerable<float>)(object)source,cancellationToken);

[Copilot]

Pull request overview

Copilot reviewed 32 out of 32 changed files in this pull request and generated 3 comments.

[AndyAyersMS]

JIT parts LGTM

[VSadov]

VM changes LGTM. Thanks!

[jakobbotsch]

/ba-g Timeout

[Copilot]

Pull request overview

Copilot reviewed 50 out of 50 changed files in this pull request and generated 1 comment.

[jakobbotsch]

Need a reapproval from someone after resolving the conflict and some copilot feedback.

[jakobbotsch]

/ba-g Failures are MIBC merge failures being fixed by #129706