Add live variable analysis

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

@@ -0,0 +1,30 @@
+package dev.openrs2.deob.analysis
+
+import org.objectweb.asm.Opcodes
+import org.objectweb.asm.tree.AbstractInsnNode
+import org.objectweb.asm.tree.IincInsnNode
+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) {
+    override fun createInitialSet(): Set<Int> {
+        return emptySet()
+    }
+
+    override fun join(set1: Set<Int>, set2: Set<Int>): Set<Int> {
+        return set1 union set2
+    }
+
+    override fun transfer(set: Set<Int>, insn: AbstractInsnNode): Set<Int> {
+        return when (insn) {
+            is VarInsnNode -> when (insn.opcode) {
+                Opcodes.ILOAD, Opcodes.LLOAD, Opcodes.FLOAD, Opcodes.DLOAD, Opcodes.ALOAD -> set.plus(insn.`var`)
+                Opcodes.ISTORE, Opcodes.LSTORE, Opcodes.FSTORE, Opcodes.DSTORE, Opcodes.ASTORE -> set.minus(insn.`var`)
+                else -> set
+            }
+            is IincInsnNode -> set.plus(insn.`var`)
+            else -> set
+        }
+    }
+}