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Commit b979315

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#57 Implement phase 1 of SSA Exit - make conventional SSA
1 parent 109fdc2 commit b979315

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3 files changed

+195
-0
lines changed

3 files changed

+195
-0
lines changed

‎optvm/src/main/java/com/compilerprogramming/ezlang/compiler/BasicBlock.java‎

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@@ -158,6 +158,11 @@ public int whichPred(BasicBlock pred) {
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}
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throw new IllegalStateException();
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}
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public BasicBlock predecessor(int i) {
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if (i >= predecessors.size())
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return null;
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return predecessors.get(i);
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}
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public int whichSucc(BasicBlock succ) {
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int i = 0;
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for (BasicBlock s: successors) {
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@@ -0,0 +1,127 @@
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package com.compilerprogramming.ezlang.compiler;
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import java.util.*;
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/**
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* Implement method to exit SSA by converting to conventional SSA,
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* without coalescing. This is the basic form.
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*/
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public class ExitSSA2 {
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CompiledFunction function;
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Map<BasicBlock,PCopy> parallelCopies = new HashMap<>();
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List<BasicBlock> allBlocks;
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public ExitSSA2(CompiledFunction function, EnumSet<Options> options) {
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this.function = function;
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allBlocks = function.getBlocks();
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insertPCopiesForEachBlock();
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makeConventionalSSA();
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removePhis();
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sequentialzeParallelCopies();
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}
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private void insertPCopiesForEachBlock() {
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// We do not actually insert pcopy instruction until needed
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// but we create an auxiliary data structure to help us track these
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for (BasicBlock block: allBlocks) {
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parallelCopies.put(block,new PCopy(block));
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}
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}
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private void insertAtEnd(BasicBlock bb, Instruction i) {
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assert bb.instructions.size() > 0;
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// Last instruction is a branch - so new instruction will
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// go before that
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int pos = bb.instructions.size()-1;
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bb.add(pos, i);
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}
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private Instruction.ParallelCopyInstruction getParallelCopyAtEnd(BasicBlock block) {
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PCopy pcopy = parallelCopies.get(block);
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if (pcopy.pCopyEnd == null) {
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pcopy.pCopyEnd = new Instruction.ParallelCopyInstruction();
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insertAtEnd(block,pcopy.pCopyEnd);
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}
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return pcopy.pCopyEnd;
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}
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private void insertAfterPhis(BasicBlock bb, Instruction newInst) {
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assert bb.instructions.size() > 0;
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int insertionPos = -1;
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for (int pos = 0; pos < bb.instructions.size(); pos++) {
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Instruction i = bb.instructions.get(pos);
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if (i instanceof Instruction.Phi) {
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insertionPos = pos+1; // After phi
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}
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else
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break;
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}
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if (insertionPos < 0) {
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throw new IllegalStateException();
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}
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bb.add(insertionPos, newInst);
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}
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private Instruction.ParallelCopyInstruction getParallelCopyAtBegin(BasicBlock block) {
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PCopy pcopy = parallelCopies.get(block);
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if (pcopy.pCopyBegin == null) {
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pcopy.pCopyBegin = new Instruction.ParallelCopyInstruction();
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insertAfterPhis(block,pcopy.pCopyBegin);
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}
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return pcopy.pCopyBegin;
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}
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/**
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* Isolate phi nodes to make SSA conventionalS
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* This is Phase 1 as described in Engineering a Compiler 3rd Edition, p490.
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*/
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private void makeConventionalSSA() {
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var blocks = function.getBlocks();
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for (BasicBlock block: blocks) {
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var phis = block.phis();
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if (phis.isEmpty())
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continue;
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for (var phi: phis) {
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for (int j = 0; j < phi.numInputs(); j++) {
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BasicBlock pred = block.predecessor(j);
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var pCopyBEnd = getParallelCopyAtEnd(pred);
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var oldInput = phi.input(j);
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var newInput = function.registerPool.newTempReg(oldInput.type);
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pCopyBEnd.addCopy(oldInput,new Operand.RegisterOperand(newInput));
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phi.replaceInput(j,newInput);
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}
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var oldPhiVar = phi.value();
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var newPhiVar = function.registerPool.newTempReg(oldPhiVar.type);
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phi.replaceValue(newPhiVar);
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var pCopyBBegin = getParallelCopyAtBegin(block);
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pCopyBBegin.addCopy(new Operand.RegisterOperand(newPhiVar),new Operand.RegisterOperand(oldPhiVar));
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}
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}
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}
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private void removePhis() {
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}
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private void sequentialzeParallelCopies() {
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}
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static final class PCopy {
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BasicBlock block;
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/**
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* Parallel copy instruction after any Phi instructions
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* in the block, null if not present
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*/
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Instruction.ParallelCopyInstruction pCopyBegin = null;
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/**
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* Parallel copy instruction at the end of a block,
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* null if not present
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*/
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Instruction.ParallelCopyInstruction pCopyEnd = null;
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public PCopy(BasicBlock block) {
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this.block = block;
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}
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}
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}

‎optvm/src/main/java/com/compilerprogramming/ezlang/compiler/Instruction.java‎

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@@ -25,6 +25,7 @@ public abstract class Instruction {
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static final int I_ARRAY_LOAD = 13;
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static final int I_FIELD_GET = 14;
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static final int I_FIELD_SET = 15;
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static final int I_PARALLEL_COPY = 16;
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public final int opcode;
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protected Operand.RegisterOperand def;
@@ -477,5 +478,67 @@ public StringBuilder toStr(StringBuilder sb) {
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}
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}
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/**
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* The parallel copy instruction is only used temporarily to exit
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* SSA form. It represents the parallel copy semantics of phi instructions.
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*/
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public static class ParallelCopyInstruction extends Instruction {
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List<Operand> sourceOperands = new ArrayList<>();
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List<Operand.RegisterOperand> destOperands = new ArrayList<>();
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protected ParallelCopyInstruction() {
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super(I_PARALLEL_COPY);
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}
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@Override
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public StringBuilder toStr(StringBuilder sb) {
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sb.append("(");
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for (int i = 0; i < destOperands.size(); i++) {
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if (i > 0)
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sb.append(",");
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sb.append(destOperands.get(i));
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}
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sb.append(") = (");
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for (int i = 0; i < sourceOperands.size(); i++) {
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if (i > 0)
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sb.append(",");
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sb.append(sourceOperands.get(i));
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}
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sb.append(")");
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return sb;
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}
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public void addCopy(Operand sourceOperand, Operand.RegisterOperand destOperand) {
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sourceOperands.add(sourceOperand);
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destOperands.add(destOperand);
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}
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@Override
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public Register def() {
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throw new UnsupportedOperationException();
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}
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@Override
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public void replaceDef(Register newDef) {
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throw new UnsupportedOperationException();
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}
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@Override
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public boolean definesVar() {
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return false;
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}
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@Override
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public List<Register> uses() {
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return Collections.emptyList();
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}
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@Override
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public void replaceUses(Register[] newUses) {
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throw new UnsupportedOperationException();
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}
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@Override
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public boolean replaceUse(Register source, Register target) {
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throw new UnsupportedOperationException();
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}
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}
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public abstract StringBuilder toStr(StringBuilder sb);
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}

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