From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: "Sofiane H. Djerbi" <46628754+kugge@users.noreply.github.com>
Date: Thu, 11 May 2023 05:02:40 +0300
Subject: [PATCH] Add SIMD utilities

Patch from Pufferfish

diff --git a/build.gradle.kts b/build.gradle.kts
index 164678d8c7f0a0a66adc957a86849fa927b7cb73..a151ca3a0803a5e653674e51e8d41a2f38b1f3df 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -68,6 +68,12 @@ dependencies {
 }
 
 val craftbukkitPackageVersion = "1_20_R1" // Paper
+// Kaiiju start - Pufferfish - SIMD utilities
+tasks.withType<JavaCompile> {
+    val compilerArgs = options.compilerArgs
+    compilerArgs.add("--add-modules=jdk.incubator.vector")
+}
+// Kaiiju end
 tasks.jar {
     archiveClassifier.set("dev")
 
diff --git a/src/main/java/gg/pufferfish/pufferfish/simd/SIMDChecker.java b/src/main/java/gg/pufferfish/pufferfish/simd/SIMDChecker.java
new file mode 100644
index 0000000000000000000000000000000000000000..586b4cd007b3b106966524e2697edddf88e3ac9d
--- /dev/null
+++ b/src/main/java/gg/pufferfish/pufferfish/simd/SIMDChecker.java
@@ -0,0 +1,59 @@
+package gg.pufferfish.pufferfish.simd;
+
+import org.bukkit.Bukkit;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+import jdk.incubator.vector.FloatVector;
+import jdk.incubator.vector.IntVector;
+import jdk.incubator.vector.VectorSpecies;
+
+/**
+ * Basically, java is annoying and we have to push this out to its own class.
+ */
+public class SIMDChecker {
+
+	public static boolean canEnable(Logger logger) {
+		try {
+			if (SIMDDetection.getJavaVersion() != 17 && SIMDDetection.getJavaVersion() != 18 && SIMDDetection.getJavaVersion() != 19) {
+				return false;
+			} else {
+				SIMDDetection.testRun = true;
+
+				VectorSpecies<Integer> ISPEC = IntVector.SPECIES_PREFERRED;
+				VectorSpecies<Float> FSPEC = FloatVector.SPECIES_PREFERRED;
+
+				logger.log(Level.INFO, "Max SIMD vector size on this system is " + ISPEC.vectorBitSize() + " bits (int)");
+				logger.log(Level.INFO, "Max SIMD vector size on this system is " + FSPEC.vectorBitSize() + " bits (float)");
+
+				if (ISPEC.elementSize() < 2 || FSPEC.elementSize() < 2) {
+					logger.log(Level.WARNING, "SIMD is not properly supported on this system!");
+					return false;
+				}
+
+				return true;
+			}
+		} catch (NoClassDefFoundError | Exception ignored) {} // Basically, we don't do anything. This lets us detect if it's not functional and disable it.
+		return false;
+	}
+
+    public static void simdWarning() {
+		// Attempt to detect vectorization
+		try {
+			SIMDDetection.isEnabled = SIMDDetection.canEnable(Bukkit.getLogger());
+			SIMDDetection.versionLimited = SIMDDetection.getJavaVersion() != 17 && SIMDDetection.getJavaVersion() != 18 && SIMDDetection.getJavaVersion() != 19;
+		} catch (NoClassDefFoundError | Exception ignored) {
+			ignored.printStackTrace();
+		}
+
+		if (SIMDDetection.isEnabled) {
+			Bukkit.getLogger().info("SIMD operations detected as functional. Will replace some operations with faster versions.");
+		} else if (SIMDDetection.versionLimited) {
+			Bukkit.getLogger().warning("Will not enable SIMD! These optimizations are only safely supported on Java 17, Java 18, and Java 19.");
+		} else {
+			Bukkit.getLogger().warning("SIMD operations are available for your server, but are not configured!");
+			Bukkit.getLogger().warning("To enable additional optimizations, add \"--add-modules=jdk.incubator.vector\" to your startup flags, BEFORE the \"-jar\".");
+			Bukkit.getLogger().warning("If you have already added this flag, then SIMD operations are not supported on your JVM or CPU.");
+			Bukkit.getLogger().warning("Debug: Java: " + System.getProperty("java.version") + ", test run: " + SIMDDetection.testRun);
+		}
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/gg/pufferfish/pufferfish/simd/SIMDDetection.java b/src/main/java/gg/pufferfish/pufferfish/simd/SIMDDetection.java
new file mode 100644
index 0000000000000000000000000000000000000000..758fa97304a32bf17935c86dc03cbf50606935d8
--- /dev/null
+++ b/src/main/java/gg/pufferfish/pufferfish/simd/SIMDDetection.java
@@ -0,0 +1,32 @@
+package gg.pufferfish.pufferfish.simd;
+
+import java.util.logging.Logger;
+
+public class SIMDDetection {
+
+	public static boolean isEnabled = false;
+	public static boolean versionLimited = false;
+	public static boolean testRun = false;
+
+	public static boolean canEnable(Logger logger) {
+		try {
+			return SIMDChecker.canEnable(logger);
+		} catch (NoClassDefFoundError | Exception ignored) {
+			return false;
+		}
+	}
+
+	public static int getJavaVersion() {
+		// https://stackoverflow.com/a/2591122
+		String version = System.getProperty("java.version");
+		if(version.startsWith("1.")) {
+			version = version.substring(2, 3);
+		} else {
+			int dot = version.indexOf(".");
+			if(dot != -1) { version = version.substring(0, dot); }
+		}
+		version = version.split("-")[0]; // Azul is stupid
+		return Integer.parseInt(version);
+	}
+
+}
\ No newline at end of file
diff --git a/src/main/java/net/minecraft/server/dedicated/DedicatedServer.java b/src/main/java/net/minecraft/server/dedicated/DedicatedServer.java
index ee75d828174ac1c84931bc087472fefd76073bdb..991e4c19763a34a6fead88363e007c2d11aad836 100644
--- a/src/main/java/net/minecraft/server/dedicated/DedicatedServer.java
+++ b/src/main/java/net/minecraft/server/dedicated/DedicatedServer.java
@@ -225,6 +225,7 @@ public class DedicatedServer extends MinecraftServer implements ServerInterface
             DedicatedServer.LOGGER.error("Unable to load server configuration", e);
             return false;
         }
+        gg.pufferfish.pufferfish.simd.SIMDChecker.simdWarning();
         dev.kaiijumc.kaiiju.KaiijuConfig.registerCommands();
         // Kaiiju end
         com.destroystokyo.paper.VersionHistoryManager.INSTANCE.getClass(); // load version history now