[mono][mini] Do a non-virtual call for bound delegates (#20039)mono-6.12.0.86

When we call a delegate that was bound to a specific function, don't do a virtual call.

Fixes mono/mono#19964

Co-authored-by: lambdageek <lambdageek@users.noreply.github.com>

3 files changed, 40 insertions, 24 deletions

diff --git a/mono/mini/interp/interp.c b/mono/mini/interp/interp.c
index e7b1f90483d..f9cdc168898 100644
--- a/mono/mini/interp/interp.c
+++ b/mono/mini/interp/interp.c
@@ -1635,6 +1635,9 @@ interp_init_delegate (MonoDelegate *del, MonoError *error)
 	if (del->interp_method) {
 		/* Delegate created by a call to ves_icall_mono_delegate_ctor_interp () */
 		del->method = ((InterpMethod *)del->interp_method)->method;
+	} if (del->method_ptr && !del->method) {
+		/* Delegate created from methodInfo.MethodHandle.GetFunctionPointer() */
+		del->interp_method = (InterpMethod *)del->method_ptr;
 	} else if (del->method) {
 		/* Delegate created dynamically */
 		del->interp_method = mono_interp_get_imethod (del->object.vtable->domain, del->method, error);
diff --git a/mono/mini/mini-trampolines.c b/mono/mini/mini-trampolines.c
index 55834cd393d..e5bb1cea2a2 100644
--- a/mono/mini/mini-trampolines.c
+++ b/mono/mini/mini-trampolines.c
@@ -1142,7 +1142,7 @@ mono_delegate_trampoline (host_mgreg_t *regs, guint8 *code, gpointer *arg, guint
 			}
 		}
 
-		if (tramp_info->method == NULL && delegate->target != NULL && method->flags & METHOD_ATTRIBUTE_VIRTUAL) {
+		if (delegate->method_ptr == NULL && tramp_info->method == NULL && delegate->target != NULL && method->flags & METHOD_ATTRIBUTE_VIRTUAL) {
 			/* tramp_info->method == NULL happens when someone asks us to JIT some delegate's
 			 * Invoke method (see compile_special).  In that case if method is virtual, the target
 			 * could be some derived class, so we need to find the correct override.
diff --git a/mono/tests/delegate17.cs b/mono/tests/delegate17.cs
index 09818514ecd..235e168ebc2 100644
--- a/mono/tests/delegate17.cs
+++ b/mono/tests/delegate17.cs
@@ -1,6 +1,33 @@
 using System;
 using System.Reflection;
 
+public enum WasCalled {
+	BaseWasCalled,
+	DerivedWasCalled
+}
+
+public delegate WasCalled Del1 (string s);
+public delegate WasCalled Del2 (string s);
+
+public class Base
+{
+	public virtual WasCalled Foo (string s)
+	{
+		Console.WriteLine ("Base.Foo called. Expected {0}", s);
+		return WasCalled.BaseWasCalled;
+	}
+}
+
+public class Derived : Base
+{
+	public override WasCalled Foo (string s)
+	{
+		Console.WriteLine ("Derived.Foo called. Expected {0}", s);
+		return WasCalled.DerivedWasCalled;
+	}
+}
+
+
 internal class Program
 {
 	public static int Main (string[] args)
@@ -14,29 +41,15 @@ internal class Program
 		// newobj Del2::.ctor
 		Del2 f = new Del2 (b.Invoke);
 		// should call Derived.Foo not Base.Foo
-		var r = f ("abcd");
-		return r;
-	}
-}
-
-
-public delegate int Del1 (string s);
-public delegate int Del2 (string s);
-
-public class Base
-{
-	public virtual int Foo (string s)
-	{
-		Console.WriteLine ("Base.Foo called. Bad");
-		return 1;
-	}
-}
-
-public class Derived : Base
-{
-	public override int Foo (string s)
-	{
-		Console.WriteLine ("Derived.Foo called. Good");
+		var r = f ("Derived.Foo");
+		if (r != WasCalled.DerivedWasCalled)
+			return 1;
+		// should call Base.Foo not Derived.Foo
+		var boundDelegate = (Del2)Activator.CreateInstance (typeof (Del2), b, typeof (Base).GetMethod (nameof (Base.Foo)).MethodHandle.GetFunctionPointer());
+		r = boundDelegate ("Base.Foo");
+		if (r != WasCalled.BaseWasCalled)
+			return 2;
 		return 0;
 	}
 }
+