From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Kevin Raneri <kevin.raneri@gmail.com>
Date: Tue, 9 Nov 2021 14:33:16 -0500
Subject: [PATCH] Optimize entity coordinate key

When executing getCoordinateKey for entities (a hotpath), the JVM is
required to repeatedly cast doubles to longs. The performance impact of
this depends on the CPU architecture, but generally switching between
FPU and ALU incurs a significant performance hit. The casted/rounded
data is already available in the blockPosition struct, so we use that
instead of re-doing the casting.

diff --git a/src/main/java/io/papermc/paper/util/MCUtil.java b/src/main/java/io/papermc/paper/util/MCUtil.java
index 8240bb085b619f257f8c0a25775e0b15068e440f..6d9668d993bb922ae9d2b76a4d766903cc3f98a4 100644
--- a/src/main/java/io/papermc/paper/util/MCUtil.java
+++ b/src/main/java/io/papermc/paper/util/MCUtil.java
@@ -213,7 +213,7 @@ public final class MCUtil {
     }
 
     public static long getCoordinateKey(final Entity entity) {
-        return ((long)(MCUtil.fastFloor(entity.getZ()) >> 4) << 32) | ((MCUtil.fastFloor(entity.getX()) >> 4) & 0xFFFFFFFFL);
+        return ((long)(entity.blockPosition.getZ() >> 4) << 32) | ((entity.blockPosition.getX() >> 4) & 0xFFFFFFFFL); // Pufferfish - eliminate double->long cast in hotpath
     }
 
     public static long getCoordinateKey(final ChunkPos pair) {
diff --git a/src/main/java/net/minecraft/world/entity/Entity.java b/src/main/java/net/minecraft/world/entity/Entity.java
index 9abe817ae202edaa2d88cd59ae5c7db0b1c634be..cfb4daaa28263aef1c74eac574b4f0e8b2f87776 100644
--- a/src/main/java/net/minecraft/world/entity/Entity.java
+++ b/src/main/java/net/minecraft/world/entity/Entity.java
@@ -307,7 +307,7 @@ public abstract class Entity implements Nameable, EntityAccess, CommandSource, S
     public double yo;
     public double zo;
     private Vec3 position;
-    private BlockPos blockPosition;
+    public BlockPos blockPosition; // Pufferfish - private->public
     private ChunkPos chunkPosition;
     private Vec3 deltaMovement;
     private float yRot;