forked from openrs2/openrs2
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package dev.openrs2.deob.transform; |
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import java.util.Set; |
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import dev.openrs2.asm.InsnMatcher; |
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import dev.openrs2.asm.InsnNodeUtils; |
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import dev.openrs2.asm.Library; |
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import dev.openrs2.asm.Transformer; |
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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.slf4j.Logger; |
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import org.slf4j.LoggerFactory; |
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public final class BitShiftTransformer extends Transformer { |
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private static final Logger logger = LoggerFactory.getLogger(BitShiftTransformer.class); |
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private static final InsnMatcher CONST_SHIFT_MATCHER = InsnMatcher.compile("(ICONST | BIPUSH | SIPUSH | LDC) (ISHL | ISHR | IUSHR | LSHL | LSHR | LUSHR)"); |
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private static final Set<Integer> LONG_SHIFTS = Set.of(Opcodes.LSHL, Opcodes.LSHR, Opcodes.LUSHR); |
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private int simplified; |
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@Override |
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public void preTransform(Library library) { |
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simplified = 0; |
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} |
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@Override |
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public void transformCode(ClassNode clazz, MethodNode method) { |
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CONST_SHIFT_MATCHER.match(method).forEach(match -> { |
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var push = match.get(0); |
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var bits = InsnNodeUtils.getIntConstant(push); |
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var opcode = match.get(1).getOpcode(); |
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var simplifiedBits = bits & (LONG_SHIFTS.contains(opcode) ? 63 : 31); |
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if (bits != simplifiedBits) { |
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method.instructions.set(push, InsnNodeUtils.createIntConstant(simplifiedBits)); |
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simplified++; |
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} |
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}); |
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} |
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@Override |
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public void postTransform(Library library) { |
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logger.info("Simplified {} bit shifts", simplified); |
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} |
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} |
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