From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Martijn Muijsers <martijnmuijsers@live.nl>
Date: Wed, 30 Nov 2022 21:15:33 +0100
Subject: [PATCH] Avoid Class#isAssignableFrom call in ClassInstanceMultiMap

Removed since 1.21.1, replaced by VMP optimization

License: LGPL-3.0 (https://www.gnu.org/licenses/lgpl-3.0.html)
Gale - https://galemc.org

This patch is based on the following mixin:
"me/jellysquid/mods/lithium/mixin/collections/entity_filtering/TypeFilterableListMixin.java"
By: Angeline <jellysquid3@users.noreply.github.com>
As part of: Lithium (https://github.com/CaffeineMC/lithium-fabric)
Licensed under: LGPL-3.0 (https://www.gnu.org/licenses/lgpl-3.0.html)

diff --git a/src/main/java/net/minecraft/util/ClassInstanceMultiMap.java b/src/main/java/net/minecraft/util/ClassInstanceMultiMap.java
index 4264b3a69b5cbe2e56058927ceb5409389cecf4b..1cdff53d2c39d785b3b3306eef27649a4b092e52 100644
--- a/src/main/java/net/minecraft/util/ClassInstanceMultiMap.java
+++ b/src/main/java/net/minecraft/util/ClassInstanceMultiMap.java
@@ -56,13 +56,33 @@ public class ClassInstanceMultiMap<T> extends AbstractCollection<T> {
     }
 
     public <S> Collection<S> find(Class<S> type) {
-        if (!this.baseClass.isAssignableFrom(type)) {
-            throw new IllegalArgumentException("Don't know how to search for " + type);
-        } else {
-            List<? extends T> list = this.byClass
-                .computeIfAbsent(type, typeClass -> this.allInstances.stream().filter(typeClass::isInstance).collect(Util.toMutableList()));
-            return (Collection<S>)Collections.unmodifiableCollection(list);
+        // Gale start - Lithium - avoid Class#isAssignableFrom call in ClassInstanceMultiMap
+        /*
+        Only perform the slow Class#isAssignableFrom(Class) if a list doesn't exist for the type, otherwise
+        we can assume it's already valid. The slow-path code is moved to a separate method to help the JVM inline this.
+         */
+        Collection<T> collection = this.byClass.get(type);
+
+        if (collection == null) {
+            collection = this.createAllOfType(type);
         }
+
+        return (Collection<S>) Collections.unmodifiableCollection(collection);
+    }
+
+    private <S> Collection<T> createAllOfType(Class<S> type) {
+        List<T> list = new java.util.ArrayList<>(1);
+
+        for (T allElement : this.allInstances) {
+            if (type.isInstance(allElement)) {
+                list.add(allElement);
+            }
+        }
+
+        this.byClass.put(type, list);
+
+        return list;
+        // Gale end - Lithium - avoid Class#isAssignableFrom call in ClassInstanceMultiMap
     }
 
     @Override