Move StubHelpers.AsyncCallContinuation to AsyncHelpers. (#121458)

Moves StubHelpers.AsyncCallContinuation to AsyncHelpers so
StubHelpers.cs doesn't need to be added to nativeaot.

Thought it would be good to have separate commits for this and the rest
of #121456

Author: jtschuster

src/coreclr/System.Private.CoreLib/src/System/Runtime/CompilerServices/AsyncHelpers.CoreCLR.cs

@@ -144,12 +144,20 @@ public ref byte GetResultStorageOrNull()
 
     public static partial class AsyncHelpers
     {
-        // This is the "magic" method on wich other "Await" methods are built.
+        // This is the "magic" method on which other "Await" methods are built.
         // Calling this from an Async method returns the continuation to the caller thus
         // explicitly initiates suspension.
         [Intrinsic]
         private static void AsyncSuspend(Continuation continuation) => throw new UnreachableException();
 
+        // An intrinsic that provides access to continuations produced by Async calls.
+        // Calling this after an Async method call returns:
+        //   * `null` if the call has completed synchronously, or
+        //   * a continuation object if the call requires suspension.
+        //     In this case the formal result of the call is undefined.
+        [Intrinsic]
+        private static Continuation? AsyncCallContinuation() => throw new UnreachableException();
+
         // Used during suspensions to hold the continuation chain and on what we are waiting.
         // Methods like FinalizeTaskReturningThunk will unlink the state and wrap into a Task.
         private struct RuntimeAsyncAwaitState

src/coreclr/System.Private.CoreLib/src/System/StubHelpers.cs

@@ -1610,9 +1610,6 @@ internal static void MulticastDebuggerTraceHelper(object o, int count)
 
         [Intrinsic]
         internal static IntPtr NextCallReturnAddress() => throw new UnreachableException(); // Unconditionally expanded intrinsic
-
-        [Intrinsic]
-        internal static Continuation? AsyncCallContinuation() => throw new UnreachableException(); // Unconditionally expanded intrinsic
     }  // class StubHelpers
 
 #if FEATURE_COMINTEROP

src/coreclr/jit/gentree.cpp

@@ -2265,7 +2265,7 @@ bool GenTreeCall::HasSideEffects(Compiler* compiler, bool ignoreExceptions, bool
 //   those cases the JIT does not know (and does not need to know) which arg is
 //   the async continuation.
 //
-//   The VM also uses the StubHelpers.AsyncCallContinuation() intrinsic in the
+//   The VM also uses the AsyncHelpers.AsyncCallContinuation() intrinsic in the
 //   stubs discussed above. The JIT must take care in those cases to still mark
 //   the preceding call as an async call; this is required for correct LSRA
 //   behavior and GC reporting around the returned async continuation. This is

src/coreclr/jit/importercalls.cpp

@@ -3323,7 +3323,7 @@ GenTree* Compiler::impIntrinsic(CORINFO_CLASS_HANDLE    clsHnd,
         return new (this, GT_LABEL) GenTree(GT_LABEL, TYP_I_IMPL);
     }
 
-    if (ni == NI_System_StubHelpers_AsyncCallContinuation)
+    if (ni == NI_System_Runtime_CompilerServices_AsyncHelpers_AsyncCallContinuation)
     {
         GenTree* node = new (this, GT_ASYNC_CONTINUATION) GenTree(GT_ASYNC_CONTINUATION, TYP_REF);
         node->SetHasOrderingSideEffect();
@@ -10872,6 +10872,10 @@ NamedIntrinsic Compiler::lookupNamedIntrinsic(CORINFO_METHOD_HANDLE method)
                             {
                                 result = NI_System_Runtime_CompilerServices_AsyncHelpers_Await;
                             }
+                            else if (strcmp(methodName, "AsyncCallContinuation") == 0)
+                            {
+                                result = NI_System_Runtime_CompilerServices_AsyncHelpers_AsyncCallContinuation;
+                            }
                         }
                         else if (strcmp(className, "StaticsHelpers") == 0)
                         {
@@ -11129,10 +11133,6 @@ NamedIntrinsic Compiler::lookupNamedIntrinsic(CORINFO_METHOD_HANDLE method)
                         {
                             result = NI_System_StubHelpers_NextCallReturnAddress;
                         }
-                        else if (strcmp(methodName, "AsyncCallContinuation") == 0)
-                        {
-                            result = NI_System_StubHelpers_AsyncCallContinuation;
-                        }
                     }
                 }
                 else if (strcmp(namespaceName, "Text") == 0)

src/coreclr/jit/namedintrinsiclist.h

@@ -107,7 +107,6 @@ enum NamedIntrinsic : unsigned short
     NI_System_RuntimeType_get_TypeHandle,
     NI_System_StubHelpers_GetStubContext,
     NI_System_StubHelpers_NextCallReturnAddress,
-    NI_System_StubHelpers_AsyncCallContinuation,
 
     NI_Array_Address,
     NI_Array_Get,
@@ -126,6 +125,7 @@ enum NamedIntrinsic : unsigned short
 
     NI_System_Runtime_CompilerServices_AsyncHelpers_AsyncSuspend,
     NI_System_Runtime_CompilerServices_AsyncHelpers_Await,
+    NI_System_Runtime_CompilerServices_AsyncHelpers_AsyncCallContinuation,
 
     NI_System_Runtime_CompilerServices_StaticsHelpers_VolatileReadAsByref,
 

src/coreclr/vm/asyncthunks.cpp

@@ -190,7 +190,7 @@ void MethodDesc::EmitTaskReturningThunk(MethodDesc* pAsyncOtherVariant, MetaSig&
 
             if (logicalResultLocal != UINT_MAX)
                 pCode->EmitSTLOC(logicalResultLocal);
-            pCode->EmitCALL(METHOD__STUBHELPERS__ASYNC_CALL_CONTINUATION, 0, 1);
+            pCode->EmitCALL(METHOD__ASYNC_HELPERS__ASYNC_CALL_CONTINUATION, 0, 1);
             pCode->EmitBRFALSE(finishedLabel);
 
             pCode->EmitLEAVE(suspendedLabel);

src/coreclr/vm/corelib.h

@@ -747,8 +747,9 @@ DEFINE_METHOD(ASYNC_HELPERS,      COMPLETED_TASK,            CompletedTask, NoSi
 DEFINE_METHOD(ASYNC_HELPERS,      CAPTURE_EXECUTION_CONTEXT, CaptureExecutionContext, NoSig)
 DEFINE_METHOD(ASYNC_HELPERS,      RESTORE_EXECUTION_CONTEXT, RestoreExecutionContext, NoSig)
 DEFINE_METHOD(ASYNC_HELPERS,      CAPTURE_CONTINUATION_CONTEXT, CaptureContinuationContext, NoSig)
-DEFINE_METHOD(ASYNC_HELPERS,      CAPTURE_CONTEXTS, CaptureContexts, NoSig)
-DEFINE_METHOD(ASYNC_HELPERS,      RESTORE_CONTEXTS, RestoreContexts, NoSig)
+DEFINE_METHOD(ASYNC_HELPERS,      CAPTURE_CONTEXTS,          CaptureContexts, NoSig)
+DEFINE_METHOD(ASYNC_HELPERS,      RESTORE_CONTEXTS,          RestoreContexts, NoSig)
+DEFINE_METHOD(ASYNC_HELPERS,      ASYNC_CALL_CONTINUATION,   AsyncCallContinuation, NoSig)
 
 #ifdef TARGET_BROWSER
 DEFINE_METHOD(ASYNC_HELPERS,      HANDLE_ASYNC_ENTRYPOINT, HandleAsyncEntryPoint, SM_TaskOfInt_RetInt)
@@ -1098,7 +1099,6 @@ DEFINE_METHOD(STUBHELPERS,          VALIDATE_BYREF,                     Validate
 DEFINE_METHOD(STUBHELPERS,          GET_STUB_CONTEXT,                   GetStubContext,                 SM_RetIntPtr)
 DEFINE_METHOD(STUBHELPERS,          LOG_PINNED_ARGUMENT,                LogPinnedArgument,              SM_IntPtr_IntPtr_RetVoid)
 DEFINE_METHOD(STUBHELPERS,          NEXT_CALL_RETURN_ADDRESS,           NextCallReturnAddress,          SM_RetIntPtr)
-DEFINE_METHOD(STUBHELPERS,          ASYNC_CALL_CONTINUATION,            AsyncCallContinuation,          SM_RetContinuation)
 DEFINE_METHOD(STUBHELPERS,          SAFE_HANDLE_ADD_REF,    SafeHandleAddRef,           SM_SafeHandle_RefBool_RetIntPtr)
 DEFINE_METHOD(STUBHELPERS,          SAFE_HANDLE_RELEASE,    SafeHandleRelease,          SM_SafeHandle_RetVoid)
 

src/coreclr/vm/jitinterface.cpp

@@ -14763,7 +14763,7 @@ CORINFO_METHOD_HANDLE CEEJitInfo::getAsyncResumptionStub(void** entryPoint)
 
     TypeHandle continuationTypeHnd = CoreLibBinder::GetClass(CLASS__CONTINUATION);
     DWORD newContinuationLoc = pCode->NewLocal(LocalDesc(continuationTypeHnd));
-    pCode->EmitCALL(METHOD__STUBHELPERS__ASYNC_CALL_CONTINUATION, 0, 1);
+    pCode->EmitCALL(METHOD__ASYNC_HELPERS__ASYNC_CALL_CONTINUATION, 0, 1);
     pCode->EmitSTLOC(newContinuationLoc);
 
     if (!msig.IsReturnTypeVoid())

src/coreclr/vm/metasig.h

@@ -619,7 +619,6 @@ DEFINE_METASIG(SM(PtrByte_RetStr, P(b), s))
 DEFINE_METASIG(SM(Str_RetPtrByte, s, P(b)))
 DEFINE_METASIG(SM(PtrByte_RetVoid, P(b), v))
 
-DEFINE_METASIG_T(SM(RetContinuation, , C(CONTINUATION)))
 DEFINE_METASIG(GM(T_RetVoid, IMAGE_CEE_CS_CALLCONV_DEFAULT, 1, M(0), v))
 DEFINE_METASIG_T(GM(RetTaskOfT, IMAGE_CEE_CS_CALLCONV_DEFAULT, 1, , GI(C(TASK_1), 1, M(0))))
 DEFINE_METASIG_T(GM(RetValueTaskOfT, IMAGE_CEE_CS_CALLCONV_DEFAULT, 1, , GI(g(VALUETASK_1), 1, M(0))))