Open-source multiplayer game server compatible with the RuneScape client
https://www.openrs2.org/
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81 lines
2.3 KiB
81 lines
2.3 KiB
package org.openrs2.deob.bytecode.transform
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import com.github.michaelbull.logging.InlineLogger
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import jakarta.inject.Singleton
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import org.objectweb.asm.Opcodes
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import org.objectweb.asm.tree.ClassNode
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import org.objectweb.asm.tree.MethodNode
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import org.objectweb.asm.tree.VarInsnNode
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import org.openrs2.asm.classpath.ClassPath
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import org.openrs2.asm.classpath.Library
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import org.openrs2.asm.transform.Transformer
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import org.openrs2.deob.bytecode.analysis.CopyPropagationAnalyzer
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/**
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* A [Transformer] that performs
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* [copy propagation](https://en.wikipedia.org/wiki/Copy_propagation) of
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* assignments of one variable to another.
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*
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* This is primarily for improving the decompilation of `for` loops. Without
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* copy propagation, the initializer in many `for` loops declares a different
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* variable to the one in the increment expression:
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*
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* ```
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* Object[] array = ...
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* int i = 0;
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* for (Object[] array2 = array; i < n; i++) {
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* // use array2[n]
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* }
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* ```
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*
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* With copy propagation, the variables match:
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*
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* ```
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* Object[] array = ...
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* for (int i = 0; i < n; i++) {
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* // use array[n]
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* }
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* ```
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*/
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@Singleton
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public class CopyPropagationTransformer : Transformer() {
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private var propagatedLocals = 0
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override fun preTransform(classPath: ClassPath) {
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propagatedLocals = 0
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}
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override fun transformCode(classPath: ClassPath, library: Library, clazz: ClassNode, method: MethodNode): Boolean {
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val analyzer = CopyPropagationAnalyzer(clazz.name, method)
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analyzer.analyze()
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for (insn in method.instructions) {
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if (insn !is VarInsnNode || !LOAD_OPCODES.contains(insn.opcode)) {
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continue
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}
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val set = analyzer.getInSet(insn) ?: continue
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val assignment = set.singleOrNull { it.destination == insn.`var` } ?: continue
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insn.`var` = assignment.source
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propagatedLocals++
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}
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return false
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}
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override fun postTransform(classPath: ClassPath) {
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logger.info { "Propagated $propagatedLocals copies" }
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}
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private companion object {
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private val logger = InlineLogger()
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private val LOAD_OPCODES = setOf(
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Opcodes.ILOAD,
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Opcodes.LLOAD,
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Opcodes.FLOAD,
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Opcodes.DLOAD,
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Opcodes.ALOAD
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)
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}
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}
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