[jit] Always pass the imt arg to interface calls in gsharedvt methods. Fixes #22624.

Author: vargaz

mono/mini/gshared.cs

@@ -944,6 +944,47 @@ public static int test_0_virtual_generic () {
 		return 0;
 	}
 
+	public interface IFace1<T> {
+		void m1 ();
+		void m2 ();
+		void m3 ();
+		void m4 ();
+		void m5 ();
+	}
+
+	public class ClassIFace<T> : IFace1<T> {
+		public void m1 () {
+		}
+		public void m2 () {
+		}
+		public void m3 () {
+		}
+		public void m4 () {
+		}
+		public void m5 () {
+		}
+	}
+
+	interface IFaceIFaceCall {
+		void call<T, T2> (IFace1<object> iface);
+	}
+
+	class MakeIFaceCall : IFaceIFaceCall {
+		public void call<T, T2> (IFace1<object> iface) {
+			iface.m1 ();
+		}
+	}
+
+	// Check normal interface calls from gsharedvt call to fully instantiated methods
+	public static int test_0_instatiated_iface_call () {
+		ClassIFace<object> c1 = new ClassIFace<object> ();
+
+		IFaceIFaceCall c = new MakeIFaceCall ();
+
+		c.call<object, int> (c1);
+		return 0;
+	}
+
 	[MethodImplAttribute (MethodImplOptions.NoInlining)]
 	static string to_string<T, T2>(T t, T2 t2) {
 		return t.ToString ();

mono/mini/method-to-ir.c

@@ -8411,6 +8411,11 @@ mono_method_to_ir (MonoCompile *cfg, MonoMethod *method, MonoBasicBlock *start_b
 														 cmethod, MONO_RGCTX_INFO_METHOD);
 						/* This is not needed, as the trampoline code will pass one, and it might be passed in the same reg as the imt arg */
 						vtable_arg = NULL;
+					} else if ((cmethod->klass->flags & TYPE_ATTRIBUTE_INTERFACE) && !imt_arg) {
+						/* This can happen when we call a fully instantiated iface method */
+						imt_arg = emit_get_rgctx_method (cfg, context_used,
+														 cmethod, MONO_RGCTX_INFO_METHOD);
+						vtable_arg = NULL;
 					}
 				}