perf: serverrpc bypasses network on host mode (#708)

When calling a server rpc on server mode (whether host or not), there is no need to go through the network. Simply invoke the user code.

This changes behaviour a little. When you call a ServerRpc, it now executes immediately. Before, it executed on the next frame.

This also allows the ServerRpc to be invoked from the server

BREAKING CHANGE: ServerRpc execute synchronous in host mode

Assets/Mirage/Weaver/Processors/RpcProcessor.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Linq;
 using System.Reflection;
 using Cysharp.Threading.Tasks;
@@ -374,5 +375,14 @@ static bool IsCallToMethod(Instruction instruction, out MethodDefinition calledM
             }
         }
 
+        protected void InvokeBody(ILProcessor worker, MethodDefinition rpc)
+        {
+            for (int i = 0; i <= rpc.Parameters.Count; i++)
+            {
+                worker.Append(worker.Create(OpCodes.Ldarg, i));
+            }
+            worker.Append(worker.Create(OpCodes.Call, rpc));
+        }
+
     }
 }

Assets/Mirage/Weaver/Processors/ServerRpcProcessor.cs

@@ -62,6 +62,13 @@ MethodDefinition GenerateStub(MethodDefinition md, CustomAttribute serverRpcAttr
 
             ILProcessor worker = md.Body.GetILProcessor();
 
+            // if (IsServer)
+            // {
+            //    call the body
+            //    return;
+            // }
+            CallBody(worker, cmd);
+
             // NetworkWriter writer = NetworkWriterPool.GetWriter()
             VariableDefinition writer = md.AddLocal<PooledNetworkWriter>();
             worker.Append(worker.Create(OpCodes.Call, md.Module.ImportReference(() => NetworkWriterPool.GetWriter())));
@@ -99,6 +106,30 @@ MethodDefinition GenerateStub(MethodDefinition md, CustomAttribute serverRpcAttr
             return cmd;
         }
 
+        public void IsServer(ILProcessor worker, Action body)
+        {
+            // if (IsLocalClient) {
+            Instruction endif = worker.Create(OpCodes.Nop);
+            worker.Append(worker.Create(OpCodes.Ldarg_0));
+            worker.Append(worker.Create(OpCodes.Call, (NetworkBehaviour nb) => nb.IsServer));
+            worker.Append(worker.Create(OpCodes.Brfalse, endif));
+
+            body();
+
+            // }
+            worker.Append(endif);
+
+        }
+
+        private void CallBody(ILProcessor worker, MethodDefinition rpc)
+        {
+            IsServer(worker, () =>
+            {
+                InvokeBody(worker, rpc);
+                worker.Append(worker.Create(OpCodes.Ret));
+            });
+        }
+
         private void CallSendServerRpc(MethodDefinition md, ILProcessor worker)
         {
             if (md.ReturnType.Is(typeof(void)))

Assets/Tests/Runtime/Host/HostComponentTests.cs

@@ -11,26 +11,6 @@ namespace Mirage.Tests.Host
 {
     public class HostComponentTests : HostSetup<MockComponent>
     {
-        [Test]
-        public void ServerRpcWithoutAuthority()
-        {
-            var gameObject2 = new GameObject("rpcObject", typeof(NetworkIdentity), typeof(MockComponent));
-            MockComponent rpcComponent2 = gameObject2.GetComponent<MockComponent>();
-
-            // spawn it without client authority
-            serverObjectManager.Spawn(gameObject2);
-
-            // process spawn message from server
-            client.Update();
-
-            // only authorized clients can call ServerRpc
-            Assert.Throws<UnauthorizedAccessException>(() =>
-           {
-               rpcComponent2.Test(1, "hello");
-           });
-
-        }
-
         [UnityTest]
         public IEnumerator ServerRpc() => UniTask.ToCoroutine(async () =>
         {