Report CALLCONV_ASYNCCALL and FLAG_ASYNC on AsyncExplicitImpl methods

src/coreclr/tools/Common/Compiler/AsyncMethodVariant.cs

@@ -34,12 +34,10 @@ public override MethodSignature Signature
         private MethodSignature InitializeSignature()
         {
             var signature = _wrappedMethod.Signature;
-            Debug.Assert(!signature.IsAsyncCall);
             Debug.Assert(signature.ReturnsTaskOrValueTask());
             TypeDesc md = signature.ReturnType;
             MethodSignatureBuilder builder = new MethodSignatureBuilder(signature);
             builder.ReturnType = md.HasInstantiation ? md.Instantiation[0] : this.Context.GetWellKnownType(WellKnownType.Void);
-            builder.Flags = signature.Flags | MethodSignatureFlags.AsyncCall;
             return (_asyncSignature = builder.ToSignature());
         }
 

src/coreclr/tools/Common/Compiler/MethodExtensions.cs

@@ -153,5 +153,12 @@ public static bool ReturnsTaskOrValueTask(this MethodSignature method)
             }
             return false;
         }
+
+        /// <summary>
+        /// Determines whether a method uses the async calling convention.
+        /// Returns true for async variants (compiler-generated wrappers around Task-returning methods)
+        /// and for special async intrinsics that don't return Task/ValueTask but use async calling convention.
+        /// </summary>
+        public static bool IsAsyncCall(this MethodDesc method) => method.IsAsync && (method.IsAsyncVariant() || !method.Signature.ReturnsTaskOrValueTask());
     }
 }

src/coreclr/tools/Common/JitInterface/CorInfoImpl.cs

@@ -833,6 +833,9 @@ private void Get_CORINFO_SIG_INFO(MethodDesc method, CORINFO_SIG_INFO* sig, Meth
         {
             Get_CORINFO_SIG_INFO(method.Signature, sig, scope);
 
+            if (method.IsAsyncCall())
+                sig->callConv |= CorInfoCallConv.CORINFO_CALLCONV_ASYNCCALL;
+
             // Does the method have a hidden parameter?
             bool hasHiddenParameter = !suppressHiddenArgument && method.RequiresInstArg();
 
@@ -877,7 +880,6 @@ private void Get_CORINFO_SIG_INFO(MethodSignature signature, CORINFO_SIG_INFO* s
 
             if (!signature.IsStatic) sig->callConv |= CorInfoCallConv.CORINFO_CALLCONV_HASTHIS;
             if (signature.IsExplicitThis) sig->callConv |= CorInfoCallConv.CORINFO_CALLCONV_EXPLICITTHIS;
-            if (signature.IsAsyncCall) sig->callConv |= CorInfoCallConv.CORINFO_CALLCONV_ASYNCCALL;
 
             TypeDesc returnType = signature.ReturnType;
 
@@ -4332,7 +4334,7 @@ private uint getJitFlags(ref CORJIT_FLAGS flags, uint sizeInBytes)
                 flags.Set(CorJitFlag.CORJIT_FLAG_SOFTFP_ABI);
             }
 
-            if (this.MethodBeingCompiled.Signature.IsAsyncCall)
+            if (this.MethodBeingCompiled.IsAsyncCall())
             {
                 flags.Set(CorJitFlag.CORJIT_FLAG_ASYNC);
             }

src/coreclr/tools/Common/TypeSystem/Common/MethodDesc.cs

@@ -23,8 +23,6 @@ public enum MethodSignatureFlags
 
         Static = 0x0010,
         ExplicitThis = 0x0020,
-
-        AsyncCall                            = 0x0100,
     }
 
     public enum EmbeddedSignatureDataKind
@@ -140,14 +138,6 @@ public bool IsExplicitThis
             }
         }
 
-        public bool IsAsyncCall
-        {
-            get
-            {
-                return (_flags & MethodSignatureFlags.AsyncCall) != 0;
-            }
-        }
-
         public int GenericParameterCount
         {
             get