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Fix Boissinot
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Bug was due to using pre-dom order (incorrect; too strict) when popping the dominator stack in checkInterfere; correct is to check dominator relationship
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@rcx
rcx committed Nov 1, 2020
1 parent aa0bb1f commit 9bfa36c
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106 changes: 70 additions & 36 deletions org.mapleir.ir/src/main/java/org/mapleir/ir/algorithms/BoissinotDestructor.java
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,9 @@
*
* @see <a href="https://hal.inria.fr/inria-00349925v1/document">Revisiting
* Out-of-SSA Translation for Correctness, CodeQuality, and Efficiency</a>
*
* Ref: Boissinot's PhD thesis: https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.385.8510&rep=rep1&type=pdf
* Ref: Slides: https://compilers.cs.uni-saarland.de/ssasem/talks/Alain.Darte.pdf
*/
public class BoissinotDestructor {
// private boolean DO_VALUE_INTERFERENCE = true;
Expand Down Expand Up @@ -83,7 +86,7 @@ private BoissinotDestructor(ControlFlowGraph cfg) {

// compute the dominance here after we have lifted non variable phi operands.
resolver = new DominanceLivenessAnalyser(cfg, entry, null);

copyPhiOperands();

dom_dfs = traverseDominatorTree();
Expand Down Expand Up @@ -301,7 +304,7 @@ private void coalescePhis() {
Local l = e.getKey();
BasicBlock b = e.getValue().getBlock();

// since we are now in csaa, phi locals never interfere and are in the same congruence class.
// since we are now in cssa, phi locals never interfere and are in the same congruence class.
// therefore we can coalesce them all together and drop phis. with this, we leave cssa.
PhiExpr phi = e.getValue().getExpression();

Expand Down Expand Up @@ -553,46 +556,62 @@ private boolean checkInterfereSingle(CongruenceClass red, CongruenceClass blue)
}
}

// returns true if a's def dominates b's def
private boolean dominates(Local a, Local b) {
BasicBlock defA = defuse.defs.get(a);
BasicBlock defB = defuse.defs.get(b);
if (defA != defB) {
// typical case (between blocks)
return resolver.domc.getDominates(defA).contains(defB);
} else {
// special case (same basic block, rely on statement ordering within block)
return checkPreDomOrder(a, b);
}
}

private boolean checkInterfere(CongruenceClass red, CongruenceClass blue) {
Stack<Local> dom = new Stack<>();
Stack<Boolean> domClasses = new Stack<>();
int nr = 0, nb = 0;
Local ir = red.first(), ib = blue.first();
// System.out.println("Enter interfere: " + red + " vs " + blue);
Stack<Local> dom = new Stack<>(); // dominator tree traversal stack
Stack<Integer> domClasses = new Stack<>(); // 0=red, 1=blue
int nr = 0, nb = 0; // from the paper
Local ir = red.first(), ib = blue.first(); // iteration pointers
Local lr = red.last(), lb = blue.last(); // end sentinels
boolean redHasNext = true, blueHasNext = true;
equalAncOut.put(ir, null); // these have no parents so we have to manually init them
equalAncOut.put(ib, null);
do {
// System.out.println("\n ir, ib, lr, lb: " + ir + " " + ib + " " + lr + " " + lb);
// System.out.println(" dom: " + dom);
Local current;
boolean currentClass;
int currentClass;
if (!blueHasNext || (redHasNext && checkPreDomOrder(ir, ib))) {
current = ir; // current = red[ir++]
currentClass = true;
// current = red[ir++] (Red case)
current = ir;
currentClass = 0;
nr++;
if (redHasNext = ir != lr)
ir = red.higher(ir);
} else {
current = ib; // current = blue[ib++]
currentClass = false;
// current = blue[ib++] (Blue case)
current = ib;
currentClass = 1;
nb++;
if (blueHasNext = ib != lb)
ib = blue.higher(ib);
}

if (!dom.isEmpty()) {
Local parent;
boolean parentClass;
do {
parent = dom.pop();
parentClass = domClasses.pop();
if (parentClass)
nr--;
else
nb--;
} while (!dom.isEmpty() && !checkPreDomOrder(parent, current));

if (interference(current, parent, currentClass == parentClass))
return true;
while (!dom.isEmpty() && !dominates(dom.peek(), current)) {
if (domClasses.peek() == 0)
nr--;
else if (domClasses.peek() == 1)
nb--;
else
assert false;
dom.pop();
domClasses.pop();
}
if (!dom.isEmpty() && interference(current, dom.peek(), currentClass == domClasses.peek())) {
return true;
}
dom.push(current);
domClasses.push(currentClass);
Expand All @@ -602,18 +621,26 @@ private boolean checkInterfere(CongruenceClass red, CongruenceClass blue) {
}

private boolean interference(Local a, Local b, boolean sameConClass) {
// System.out.println("Check interference: " + a + " " + b + " " + sameConClass);
equalAncOut.put(a, null);
if (sameConClass) {
b = equalAncOut.get(b);
}
if (b == null) {
return false;
}
if (dominates(a, b))
throw new IllegalArgumentException("b should dom a");

Local tmp = b;
while (tmp != null && !intersect(a, tmp)) {
tmp = equalAncIn.get(tmp);
}
if (values.getNonNull(a) != values.getNonNull(b)) {
// chain_intersect
return tmp != null;
} else {
// update_equal_anc_out
equalAncOut.put(a, tmp);
return false;
}
Expand All @@ -627,7 +654,7 @@ private boolean intersect(Local a, Local b) {
throw new IllegalArgumentException("me too thanks: " + a);
}

if (checkPreDomOrder(a, b))
if (dominates(a, b))
throw new IllegalArgumentException("b should dom a");

BasicBlock defA = defuse.defs.get(a);
Expand All @@ -647,6 +674,7 @@ private boolean intersect(Local a, Local b) {
}

private void merge(CongruenceClass conClassA, CongruenceClass conClassB) {
// System.out.println("Merge class " + conClassA + " <- " + conClassB);
conClassA.addAll(conClassB);
for (Local l : conClassB)
congruenceClasses.put(l, conClassA);
Expand All @@ -655,9 +683,9 @@ private void merge(CongruenceClass conClassA, CongruenceClass conClassB) {
Local in = equalAncIn.get(l);
Local out = equalAncOut.get(l);
if (in != null && out != null)
equalAncIn.put(l, checkPreDomOrder(in, out) ? in : out);
else
equalAncIn.put(l, in != null ? in : out != null ? out : null);
equalAncIn.put(l, checkPreDomOrder(in, out) ? out : in); // the MAXIMUM
else if (in != null || out != null)
equalAncIn.put(l, in != null ? in : out);
}
}

Expand Down Expand Up @@ -873,14 +901,20 @@ private class CongruenceClass extends TreeSet<Local> {
private static final long serialVersionUID = -4472334406997712498L;

CongruenceClass() {
super(new Comparator<Local>() {
@Override
public int compare(Local o1, Local o2) {
if (o1 == o2)
return 0;
return ((defuse.defIndex.get(o1) - defuse.defIndex.get(o2))) >> 31 | 1;
}
super((o1, o2) -> {
if (o1 == o2)
return 0;
return ((defuse.defIndex.get(o1) - defuse.defIndex.get(o2))) >> 31 | 1;
});
}
}

// Used for dumping the dominator graph
// private static <N extends FastGraphVertex> void dumpGraph(FastDirectedGraph<N, FastGraphEdge<N>> g, String name) {
// try {
// Exporter.fromGraph(GraphUtils.makeDotSkeleton(g)).export(new File("cfg testing", name + ".png"));
// } catch (IOException e) {
// e.printStackTrace();
// }
// }
}
34 changes: 22 additions & 12 deletions org.mapleir.main/src/main/java/org/mapleir/CleanBoot.java
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Original file line number Diff line number Diff line change
@@ -1,15 +1,15 @@
package org.mapleir;

import org.mapleir.asm.ClassHelper;
import org.mapleir.asm.ClassNode;
import org.mapleir.asm.InsnListUtils;
import org.mapleir.asm.MethodNode;
import org.mapleir.context.IRCache;
import org.mapleir.ir.algorithms.BoissinotDestructor;
import org.mapleir.ir.algorithms.LocalsReallocator;
import org.mapleir.ir.cfg.ControlFlowGraph;
import org.mapleir.ir.codegen.ControlFlowGraphDumper;
import org.mapleir.ir.utils.CFGUtils;
import org.mapleir.asm.ClassHelper;
import org.mapleir.asm.InsnListUtils;
import org.mapleir.asm.ClassNode;
import org.mapleir.asm.MethodNode;
import org.objectweb.asm.ClassWriter;

import java.io.File;
import java.io.FileInputStream;
Expand All @@ -18,26 +18,36 @@
public class CleanBoot {

public static void main(String[] args) throws Exception {
ClassNode cn = ClassHelper.create(new FileInputStream(new File("res", "BiteCode.class")));
ClassNode cn = ClassHelper.create(new FileInputStream(new File("MemeIn.class")));
IRCache irFactory = new IRCache();
for (MethodNode mn : cn.getMethods()) {
// if (!mn.getName().equals("merge"))
// continue;
// if (mn.getName().equals("merge"))
// System.out.println(InsnListUtils.insnListToString(mn.node.instructions));

ControlFlowGraph cfg = irFactory.getNonNull(mn);

System.out.println(cfg);
CFGUtils.easyDumpCFG(cfg, "pre-destruct");
// if (mn.getName().equals("merge"))
// System.out.println(cfg);
// if (mn.getName().equals("merge"))
// CFGUtils.easyDumpCFG(cfg, "pre-destruct");
cfg.verify();

BoissinotDestructor.leaveSSA(cfg);

CFGUtils.easyDumpCFG(cfg, "pre-reaalloc");
// if (mn.getName().equals("merge"))
// CFGUtils.easyDumpCFG(cfg, "pre-reaalloc");
LocalsReallocator.realloc(cfg);
CFGUtils.easyDumpCFG(cfg, "post-reaalloc");
System.out.println(cfg);
// if (mn.getName().equals("merge"))
// CFGUtils.easyDumpCFG(cfg, "post-reaalloc");
// System.out.println(cfg);
cfg.verify();
System.out.println("Rewriting " + mn.getName());
(new ControlFlowGraphDumper(cfg, mn)).dump();

System.out.println(InsnListUtils.insnListToString(mn.node.instructions));
}
ClassHelper.dump(cn, new FileOutputStream(new File("out", "Bad.class")));
new FileOutputStream(new File("Meme.class")).write(ClassHelper.toByteArray(cn, ClassWriter.COMPUTE_FRAMES));
}
}

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