Use fastutil to reduce allocations in LiveVariableAnalyzer

Signed-off-by: Graham <gpe@openrs2.dev>

buildSrc/src/main/java/Versions.kt

@@ -4,6 +4,7 @@ object Versions {
     const val clikt = "2.6.0"
     const val commonsCompress = "1.20"
     const val dependencyLicenseReport = "1.13"
+    const val fastutil = "8.3.1"
     const val fernflower = "1.0.3"
     const val guava = "28.2-jre"
     const val guice = "4.2.3"

deob/build.gradle.kts

@@ -14,6 +14,7 @@ dependencies {
     implementation(project(":bundler"))
     implementation(project(":deob-annotations"))
     implementation("com.google.guava:guava:${Versions.guava}")
+    implementation("it.unimi.dsi:fastutil:${Versions.fastutil}")
 }
 
 publishing {

deob/src/main/java/dev/openrs2/deob/analysis/LiveVariableAnalyzer.kt

@@ -1,5 +1,8 @@
 package dev.openrs2.deob.analysis
 
+import it.unimi.dsi.fastutil.ints.IntOpenHashSet
+import it.unimi.dsi.fastutil.ints.IntSet
+import it.unimi.dsi.fastutil.ints.IntSets
 import org.objectweb.asm.Opcodes
 import org.objectweb.asm.tree.AbstractInsnNode
 import org.objectweb.asm.tree.IincInsnNode
@@ -7,17 +10,17 @@ import org.objectweb.asm.tree.MethodNode
 import org.objectweb.asm.tree.VarInsnNode
 
 class LiveVariableAnalyzer(owner: String, method: MethodNode) :
-    DataFlowAnalyzer<Set<Int>>(owner, method, backwards = true) {
+    DataFlowAnalyzer<IntSet>(owner, method, backwards = true) {
 
-    override fun createInitialSet(): Set<Int> {
-        return emptySet()
+    override fun createInitialSet(): IntSet {
+        return IntSets.EMPTY_SET
     }
 
-    override fun join(set1: Set<Int>, set2: Set<Int>): Set<Int> {
+    override fun join(set1: IntSet, set2: IntSet): IntSet {
         return set1 union set2
     }
 
-    override fun transfer(set: Set<Int>, insn: AbstractInsnNode): Set<Int> {
+    override fun transfer(set: IntSet, insn: AbstractInsnNode): IntSet {
         return when (insn) {
             is VarInsnNode -> when (insn.opcode) {
                 Opcodes.ILOAD, Opcodes.LLOAD, Opcodes.FLOAD, Opcodes.DLOAD, Opcodes.ALOAD -> set.plus(insn.`var`)
@@ -28,4 +31,38 @@ class LiveVariableAnalyzer(owner: String, method: MethodNode) :
             else -> set
         }
     }
+
+    private infix fun IntSet.union(other: IntSet): IntSet {
+        if (this == other || other.isEmpty()) {
+            return this
+        } else if (isEmpty()) {
+            return other
+        }
+
+        val set = IntOpenHashSet(this)
+        set.addAll(other)
+        return set
+    }
+
+    private fun IntSet.plus(element: Int): IntSet {
+        if (contains(element)) {
+            return this
+        }
+
+        val newSet = IntOpenHashSet(this)
+        newSet.add(element)
+        return newSet
+    }
+
+    private fun IntSet.minus(element: Int): IntSet {
+        if (!contains(element)) {
+            return this
+        } else if (size == 1) {
+            return IntSets.EMPTY_SET
+        }
+
+        val newSet = IntOpenHashSet(this)
+        newSet.remove(element)
+        return newSet
+    }
 }