From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <spottedleaf@spottedleaf.dev>
Date: Mon, 27 Apr 2020 02:48:06 -0700
Subject: [PATCH] Reduce MutableInt allocations from light engine

We can abuse the fact light is single threaded and share an instance
per light engine instance

diff --git a/src/main/java/net/minecraft/world/level/lighting/BlockLightEngine.java b/src/main/java/net/minecraft/world/level/lighting/BlockLightEngine.java
index 8979101a52537f4ec03a5f43030264b8e72fcea4..709fc42057f8a0282c3c942067e63abb874d9042 100644
--- a/src/main/java/net/minecraft/world/level/lighting/BlockLightEngine.java
+++ b/src/main/java/net/minecraft/world/level/lighting/BlockLightEngine.java
@@ -16,6 +16,7 @@ public final class BlockLightEngine extends LayerLightEngine<BlockLightSectionSt
 
     private static final Direction[] DIRECTIONS = Direction.values();
     private final BlockPos.MutableBlockPos pos = new BlockPos.MutableBlockPos();
+    private final MutableInt mutableint = new MutableInt(); // Paper
 
     public BlockLightEngine(LightChunkGetter chunkProvider) {
         super(chunkProvider, LightLayer.BLOCK, new BlockLightSectionStorage(chunkProvider));
@@ -47,7 +48,7 @@ public final class BlockLightEngine extends LayerLightEngine<BlockLightSectionSt
             if (enumdirection == null) {
                 return 15;
             } else {
-                MutableInt mutableint = new MutableInt();
+                //MutableInt mutableint = new MutableInt(); // Paper - share mutableint, single threaded
                 BlockState iblockdata = this.getStateAndOpacity(targetId, mutableint);
 
                 if (mutableint.getValue() >= 15) {
diff --git a/src/main/java/net/minecraft/world/level/lighting/SkyLightEngine.java b/src/main/java/net/minecraft/world/level/lighting/SkyLightEngine.java
index d99890121bdf1e499e364bdc953e628c04d69b95..ff1fbc46776b26ca56c3293e40ed55028230ec46 100644
--- a/src/main/java/net/minecraft/world/level/lighting/SkyLightEngine.java
+++ b/src/main/java/net/minecraft/world/level/lighting/SkyLightEngine.java
@@ -15,6 +15,7 @@ public final class SkyLightEngine extends LayerLightEngine<SkyLightSectionStorag
 
     private static final Direction[] DIRECTIONS = Direction.values();
     private static final Direction[] HORIZONTALS = new Direction[]{Direction.NORTH, Direction.SOUTH, Direction.WEST, Direction.EAST};
+    private final MutableInt mutableint = new MutableInt(); // Paper
 
     public SkyLightEngine(LightChunkGetter chunkProvider) {
         super(chunkProvider, LightLayer.SKY, new SkyLightSectionStorage(chunkProvider));
@@ -36,7 +37,7 @@ public final class SkyLightEngine extends LayerLightEngine<SkyLightSectionStorag
             if (level >= 15) {
                 return level;
             } else {
-                MutableInt mutableint = new MutableInt();
+                //MutableInt mutableint = new MutableInt(); // Paper - share mutableint, single threaded
                 BlockState iblockdata = this.getStateAndOpacity(targetId, mutableint);
 
                 if (mutableint.getValue() >= 15) {