Open-source multiplayer game server compatible with the RuneScape client https://www.openrs2.org/
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openrs2/deob-bytecode/src/main/kotlin/org/openrs2/deob/bytecode/transform/UnusedLocalTransformer.kt

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package org.openrs2.deob.bytecode.transform
import com.github.michaelbull.logging.InlineLogger
import org.objectweb.asm.Opcodes
import org.objectweb.asm.tree.AbstractInsnNode
import org.objectweb.asm.tree.ClassNode
import org.objectweb.asm.tree.MethodNode
import org.objectweb.asm.tree.VarInsnNode
import org.openrs2.asm.classpath.ClassPath
import org.openrs2.asm.classpath.Library
import org.openrs2.asm.deleteExpression
import org.openrs2.asm.isPure
import org.openrs2.asm.transform.Transformer
import org.openrs2.deob.bytecode.analysis.LiveVariableAnalyzer
import javax.inject.Singleton
@Singleton
public class UnusedLocalTransformer : Transformer() {
private var localsRemoved = 0
override fun preTransform(classPath: ClassPath) {
localsRemoved = 0
}
override fun transformCode(classPath: ClassPath, library: Library, clazz: ClassNode, method: MethodNode): Boolean {
val analyzer = LiveVariableAnalyzer(clazz.name, method)
analyzer.analyze()
val deadStores = mutableListOf<AbstractInsnNode>()
for (insn in method.instructions) {
if (insn !is VarInsnNode || !STORE_OPCODES.contains(insn.opcode)) {
continue
}
val live = analyzer.getInSet(insn)?.contains(insn.`var`) ?: false
if (live) {
continue
}
deadStores += insn
}
for (insn in deadStores) {
if (method.instructions.deleteExpression(insn, AbstractInsnNode::isPure)) {
localsRemoved++
}
}
return false
}
override fun postTransform(classPath: ClassPath) {
logger.info { "Removed $localsRemoved unused local variables" }
}
private companion object {
private val logger = InlineLogger()
private val STORE_OPCODES = setOf(
Opcodes.ISTORE,
Opcodes.LSTORE,
Opcodes.FSTORE,
Opcodes.DSTORE,
Opcodes.ASTORE
)
}
}