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r8 / r8 / ddbaf8bcef55c2adf8aaef8993c1c57a6339f84f / . / src / main / java / com / android / tools / r8 / ir / optimize / CodeRewriter.java
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// Copyright (c) 2016, the R8 project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
package com.android.tools.r8.ir.optimize;
import com.android.tools.r8.dex.Constants;
import com.android.tools.r8.errors.CompilationError;
import com.android.tools.r8.errors.Unreachable;
import com.android.tools.r8.graph.AppInfo;
import com.android.tools.r8.graph.DebugLocalInfo;
import com.android.tools.r8.graph.DexClass;
import com.android.tools.r8.graph.DexEncodedField;
import com.android.tools.r8.graph.DexEncodedMethod;
import com.android.tools.r8.graph.DexEncodedMethod.ClassInlinerEligibility;
import com.android.tools.r8.graph.DexField;
import com.android.tools.r8.graph.DexItemFactory;
import com.android.tools.r8.graph.DexMethod;
import com.android.tools.r8.graph.DexProgramClass;
import com.android.tools.r8.graph.DexProto;
import com.android.tools.r8.graph.DexString;
import com.android.tools.r8.graph.DexType;
import com.android.tools.r8.graph.DexValue.DexValueBoolean;
import com.android.tools.r8.graph.DexValue.DexValueByte;
import com.android.tools.r8.graph.DexValue.DexValueChar;
import com.android.tools.r8.graph.DexValue.DexValueDouble;
import com.android.tools.r8.graph.DexValue.DexValueFloat;
import com.android.tools.r8.graph.DexValue.DexValueInt;
import com.android.tools.r8.graph.DexValue.DexValueLong;
import com.android.tools.r8.graph.DexValue.DexValueNull;
import com.android.tools.r8.graph.DexValue.DexValueShort;
import com.android.tools.r8.graph.DexValue.DexValueString;
import com.android.tools.r8.ir.analysis.type.TypeEnvironment;
import com.android.tools.r8.ir.analysis.type.TypeLatticeElement;
import com.android.tools.r8.ir.code.ArrayPut;
import com.android.tools.r8.ir.code.BasicBlock;
import com.android.tools.r8.ir.code.Binop;
import com.android.tools.r8.ir.code.CatchHandlers;
import com.android.tools.r8.ir.code.CheckCast;
import com.android.tools.r8.ir.code.Cmp;
import com.android.tools.r8.ir.code.Cmp.Bias;
import com.android.tools.r8.ir.code.ConstInstruction;
import com.android.tools.r8.ir.code.ConstNumber;
import com.android.tools.r8.ir.code.ConstString;
import com.android.tools.r8.ir.code.DebugLocalWrite;
import com.android.tools.r8.ir.code.DominatorTree;
import com.android.tools.r8.ir.code.Goto;
import com.android.tools.r8.ir.code.IRCode;
import com.android.tools.r8.ir.code.If;
import com.android.tools.r8.ir.code.If.Type;
import com.android.tools.r8.ir.code.Instruction;
import com.android.tools.r8.ir.code.InstructionIterator;
import com.android.tools.r8.ir.code.InstructionListIterator;
import com.android.tools.r8.ir.code.Invoke;
import com.android.tools.r8.ir.code.InvokeDirect;
import com.android.tools.r8.ir.code.InvokeMethod;
import com.android.tools.r8.ir.code.InvokeNewArray;
import com.android.tools.r8.ir.code.InvokeStatic;
import com.android.tools.r8.ir.code.InvokeVirtual;
import com.android.tools.r8.ir.code.MemberType;
import com.android.tools.r8.ir.code.NewArrayEmpty;
import com.android.tools.r8.ir.code.NewArrayFilledData;
import com.android.tools.r8.ir.code.NewInstance;
import com.android.tools.r8.ir.code.NumericType;
import com.android.tools.r8.ir.code.Phi;
import com.android.tools.r8.ir.code.Position;
import com.android.tools.r8.ir.code.Return;
import com.android.tools.r8.ir.code.StaticGet;
import com.android.tools.r8.ir.code.StaticPut;
import com.android.tools.r8.ir.code.Switch;
import com.android.tools.r8.ir.code.Throw;
import com.android.tools.r8.ir.code.Value;
import com.android.tools.r8.ir.code.ValueType;
import com.android.tools.r8.ir.code.Xor;
import com.android.tools.r8.ir.conversion.OptimizationFeedback;
import com.android.tools.r8.ir.optimize.SwitchUtils.EnumSwitchInfo;
import com.android.tools.r8.shaking.Enqueuer.AppInfoWithLiveness;
import com.android.tools.r8.utils.InternalOptions;
import com.android.tools.r8.utils.LongInterval;
import com.google.common.base.Equivalence;
import com.google.common.base.Equivalence.Wrapper;
import com.google.common.base.Supplier;
import com.google.common.base.Suppliers;
import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;
import com.google.common.collect.ListMultimap;
import com.google.common.collect.Maps;
import com.google.common.collect.Sets;
import it.unimi.dsi.fastutil.ints.Int2IntArrayMap;
import it.unimi.dsi.fastutil.ints.Int2IntMap;
import it.unimi.dsi.fastutil.ints.Int2ObjectAVLTreeMap;
import it.unimi.dsi.fastutil.ints.Int2ObjectSortedMap;
import it.unimi.dsi.fastutil.ints.Int2ReferenceSortedMap;
import it.unimi.dsi.fastutil.ints.IntArrayList;
import it.unimi.dsi.fastutil.ints.IntIterator;
import it.unimi.dsi.fastutil.ints.IntList;
import it.unimi.dsi.fastutil.ints.IntLists;
import it.unimi.dsi.fastutil.objects.Object2IntLinkedOpenHashMap;
import it.unimi.dsi.fastutil.objects.Object2IntMap;
import it.unimi.dsi.fastutil.objects.Reference2IntMap;
import it.unimi.dsi.fastutil.objects.Reference2IntOpenHashMap;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.Deque;
import java.util.HashMap;
import java.util.HashSet;
import java.util.IdentityHashMap;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.ListIterator;
import java.util.Map;
import java.util.Set;
import java.util.function.Function;
import java.util.function.Predicate;
public class CodeRewriter {
private static final int MAX_FILL_ARRAY_SIZE = 8 * Constants.KILOBYTE;
// This constant was determined by experimentation.
private static final int STOP_SHARED_CONSTANT_THRESHOLD = 50;
private final AppInfo appInfo;
private final DexItemFactory dexItemFactory;
private final Set<DexMethod> libraryMethodsReturningReceiver;
private final InternalOptions options;
// For some optimizations, e.g. optimizing synthetic classes, we may need to resolve
// the current class being optimized. Since all methods of this class are optimized
// together and are not concurrent to other optimizations, we just store current
// synthetic class.
private DexProgramClass cachedClass = null;
public CodeRewriter(
AppInfo appInfo, Set<DexMethod> libraryMethodsReturningReceiver, InternalOptions options) {
this.appInfo = appInfo;
this.options = options;
this.dexItemFactory = appInfo.dexItemFactory;
this.libraryMethodsReturningReceiver = libraryMethodsReturningReceiver;
}
private static boolean removedTrivialGotos(IRCode code) {
ListIterator<BasicBlock> iterator = code.listIterator();
assert iterator.hasNext();
BasicBlock block = iterator.next();
BasicBlock nextBlock;
do {
nextBlock = iterator.hasNext() ? iterator.next() : null;
// Trivial goto block are only kept if they are self-targeting or are targeted by
// fallthroughs.
BasicBlock blk = block; // Additional local for lambda below.
assert !block.isTrivialGoto()
|| block.exit().asGoto().getTarget() == block
|| code.blocks.get(0) == block
|| block.getPredecessors().stream().anyMatch((b) -> b.exit().fallthroughBlock() == blk);
// Trivial goto blocks never target the next block (in that case there should just be a
// fallthrough).
assert !block.isTrivialGoto() || block.exit().asGoto().getTarget() != nextBlock;
block = nextBlock;
} while (block != null);
return true;
}
private static boolean isFallthroughBlock(BasicBlock block) {
for (BasicBlock pred : block.getPredecessors()) {
if (pred.exit().fallthroughBlock() == block) {
return true;
}
}
return false;
}
private static void collapsTrivialGoto(
IRCode code, BasicBlock block, BasicBlock nextBlock, List<BasicBlock> blocksToRemove) {
// This is the base case for GOTO loops.
if (block.exit().asGoto().getTarget() == block) {
return;
}
BasicBlock target = block.endOfGotoChain();
boolean needed = false;
if (target == null) {
// This implies we are in a loop of GOTOs. In that case, we will iteratively remove each
// trivial GOTO one-by-one until the above base case (one block targeting itself) is left.
target = block.exit().asGoto().getTarget();
}
if (target != nextBlock) {
// Not targeting the fallthrough block, determine if we need this goto. We need it if
// a fallthrough can hit this block. That is the case if the block is the entry block
// or if one of the predecessors fall through to the block.
needed = code.blocks.get(0) == block || isFallthroughBlock(block);
}
if (!needed) {
blocksToRemove.add(block);
for (BasicBlock pred : block.getPredecessors()) {
pred.replaceSuccessor(block, target);
}
for (BasicBlock succ : block.getSuccessors()) {
succ.getPredecessors().remove(block);
}
for (BasicBlock pred : block.getPredecessors()) {
if (!target.getPredecessors().contains(pred)) {
target.getPredecessors().add(pred);
}
}
}
}
private static void collapsIfTrueTarget(BasicBlock block) {
If insn = block.exit().asIf();
BasicBlock target = insn.getTrueTarget();
BasicBlock newTarget = target.endOfGotoChain();
BasicBlock fallthrough = insn.fallthroughBlock();
BasicBlock newFallthrough = fallthrough.endOfGotoChain();
if (newTarget != null && target != newTarget) {
insn.getBlock().replaceSuccessor(target, newTarget);
target.getPredecessors().remove(block);
if (!newTarget.getPredecessors().contains(block)) {
newTarget.getPredecessors().add(block);
}
}
if (block.exit().isIf()) {
insn = block.exit().asIf();
if (insn.getTrueTarget() == newFallthrough) {
// Replace if with the same true and fallthrough target with a goto to the fallthrough.
block.replaceSuccessor(insn.getTrueTarget(), fallthrough);
assert block.exit().isGoto();
assert block.exit().asGoto().getTarget() == fallthrough;
}
}
}
private static void collapsNonFallthroughSwitchTargets(BasicBlock block) {
Switch insn = block.exit().asSwitch();
BasicBlock fallthroughBlock = insn.fallthroughBlock();
Set<BasicBlock> replacedBlocks = new HashSet<>();
for (int j = 0; j < insn.targetBlockIndices().length; j++) {
BasicBlock target = insn.targetBlock(j);
if (target != fallthroughBlock) {
BasicBlock newTarget = target.endOfGotoChain();
if (newTarget != null && target != newTarget && !replacedBlocks.contains(target)) {
insn.getBlock().replaceSuccessor(target, newTarget);
target.getPredecessors().remove(block);
if (!newTarget.getPredecessors().contains(block)) {
newTarget.getPredecessors().add(block);
}
replacedBlocks.add(target);
}
}
}
}
// TODO(sgjesse); Move this somewhere else, and reuse it for some of the other switch rewritings.
public abstract static class InstructionBuilder<T> {
protected int blockNumber;
protected final Position position;
protected InstructionBuilder(Position position) {
this.position = position;
}
public abstract T self();
public T setBlockNumber(int blockNumber) {
this.blockNumber = blockNumber;
return self();
}
}
public static class SwitchBuilder extends InstructionBuilder<SwitchBuilder> {
private Value value;
private final Int2ObjectSortedMap<BasicBlock> keyToTarget = new Int2ObjectAVLTreeMap<>();
private BasicBlock fallthrough;
public SwitchBuilder(Position position) {
super(position);
}
@Override
public SwitchBuilder self() {
return this;
}
public SwitchBuilder setValue(Value value) {
this.value = value;
return this;
}
public SwitchBuilder addKeyAndTarget(int key, BasicBlock target) {
keyToTarget.put(key, target);
return this;
}
public SwitchBuilder setFallthrough(BasicBlock fallthrough) {
this.fallthrough = fallthrough;
return this;
}
public BasicBlock build() {
final int NOT_FOUND = -1;
Object2IntMap<BasicBlock> targetToSuccessorIndex = new Object2IntLinkedOpenHashMap<>();
targetToSuccessorIndex.defaultReturnValue(NOT_FOUND);
int[] keys = new int[keyToTarget.size()];
int[] targetBlockIndices = new int[keyToTarget.size()];
// Sort keys descending.
int count = 0;
IntIterator iter = keyToTarget.keySet().iterator();
while (iter.hasNext()) {
int key = iter.nextInt();
BasicBlock target = keyToTarget.get(key);
Integer targetIndex =
targetToSuccessorIndex.computeIfAbsent(target, b -> targetToSuccessorIndex.size());
keys[count] = key;
targetBlockIndices[count] = targetIndex;
count++;
}
Integer fallthroughIndex =
targetToSuccessorIndex.computeIfAbsent(fallthrough, b -> targetToSuccessorIndex.size());
Switch newSwitch = new Switch(value, keys, targetBlockIndices, fallthroughIndex);
newSwitch.setPosition(position);
BasicBlock newSwitchBlock = BasicBlock.createSwitchBlock(blockNumber, newSwitch);
for (BasicBlock successor : targetToSuccessorIndex.keySet()) {
newSwitchBlock.link(successor);
}
return newSwitchBlock;
}
}
public static class IfBuilder extends InstructionBuilder<IfBuilder> {
private final IRCode code;
private Value left;
private int right;
private BasicBlock target;
private BasicBlock fallthrough;
public IfBuilder(Position position, IRCode code) {
super(position);
this.code = code;
}
@Override
public IfBuilder self() {
return this;
}
public IfBuilder setLeft(Value left) {
this.left = left;
return this;
}
public IfBuilder setRight(int right) {
this.right = right;
return this;
}
public IfBuilder setTarget(BasicBlock target) {
this.target = target;
return this;
}
public IfBuilder setFallthrough(BasicBlock fallthrough) {
this.fallthrough = fallthrough;
return this;
}
public BasicBlock build() {
assert target != null;
assert fallthrough != null;
If newIf;
BasicBlock ifBlock;
if (right != 0) {
ConstNumber rightConst = code.createIntConstant(right);
rightConst.setPosition(position);
newIf = new If(Type.EQ, ImmutableList.of(left, rightConst.dest()));
ifBlock = BasicBlock.createIfBlock(blockNumber, newIf, rightConst);
} else {
newIf = new If(Type.EQ, left);
ifBlock = BasicBlock.createIfBlock(blockNumber, newIf);
}
newIf.setPosition(position);
ifBlock.link(target);
ifBlock.link(fallthrough);
return ifBlock;
}
}
/**
* Covert the switch instruction to a sequence of if instructions checking for a specified
* set of keys, followed by a new switch with the remaining keys.
*/
private void convertSwitchToSwitchAndIfs(
IRCode code, ListIterator<BasicBlock> blocksIterator, BasicBlock originalBlock,
InstructionListIterator iterator, Switch theSwitch,
List<IntList> switches, IntList keysToRemove) {
Position position = theSwitch.getPosition();
// Extract the information from the switch before removing it.
Int2ReferenceSortedMap<BasicBlock> keyToTarget = theSwitch.getKeyToTargetMap();
// Keep track of the current fallthrough, starting with the original.
BasicBlock fallthroughBlock = theSwitch.fallthroughBlock();
// Split the switch instruction into its own block and remove it.
iterator.previous();
BasicBlock originalSwitchBlock = iterator.split(code, blocksIterator);
assert !originalSwitchBlock.hasCatchHandlers();
assert originalSwitchBlock.getInstructions().size() == 1;
assert originalBlock.exit().isGoto();
theSwitch.moveDebugValues(originalBlock.exit());
blocksIterator.remove();
theSwitch.getBlock().detachAllSuccessors();
BasicBlock block = theSwitch.getBlock().unlinkSinglePredecessor();
assert theSwitch.getBlock().getPredecessors().size() == 0;
assert theSwitch.getBlock().getSuccessors().size() == 0;
assert block == originalBlock;
// Collect the new blocks for adding to the block list.
int nextBlockNumber = code.getHighestBlockNumber() + 1;
LinkedList<BasicBlock> newBlocks = new LinkedList<>();
// Build the switch-blocks backwards, to always have the fallthrough block in hand.
for (int i = switches.size() - 1; i >= 0; i--) {
SwitchBuilder switchBuilder = new SwitchBuilder(position);
switchBuilder.setValue(theSwitch.value());
IntList keys = switches.get(i);
for (int j = 0; j < keys.size(); j++) {
int key = keys.getInt(j);
switchBuilder.addKeyAndTarget(key, keyToTarget.get(key));
}
switchBuilder
.setFallthrough(fallthroughBlock)
.setBlockNumber(nextBlockNumber++);
BasicBlock newSwitchBlock = switchBuilder.build();
newBlocks.addFirst(newSwitchBlock);
fallthroughBlock = newSwitchBlock;
}
// Build the if-blocks backwards, to always have the fallthrough block in hand.
for (int i = keysToRemove.size() - 1; i >= 0; i--) {
int key = keysToRemove.getInt(i);
BasicBlock peeledOffTarget = keyToTarget.get(key);
IfBuilder ifBuilder = new IfBuilder(position, code);
ifBuilder
.setLeft(theSwitch.value())
.setRight(key)
.setTarget(peeledOffTarget)
.setFallthrough(fallthroughBlock)
.setBlockNumber(nextBlockNumber++);
BasicBlock ifBlock = ifBuilder.build();
newBlocks.addFirst(ifBlock);
fallthroughBlock = ifBlock;
}
// Finally link the block before the original switch to the new block sequence.
originalBlock.link(fallthroughBlock);
// Finally add the blocks.
newBlocks.forEach(blocksIterator::add);
}
public void rewriteSwitch(IRCode code) {
ListIterator<BasicBlock> blocksIterator = code.listIterator();
while (blocksIterator.hasNext()) {
BasicBlock block = blocksIterator.next();
InstructionListIterator iterator = block.listIterator();
while (iterator.hasNext()) {
Instruction instruction = iterator.next();
if (instruction.isSwitch()) {
Switch theSwitch = instruction.asSwitch();
if (theSwitch.numberOfKeys() == 1) {
// Rewrite the switch to an if.
int fallthroughBlockIndex = theSwitch.getFallthroughBlockIndex();
int caseBlockIndex = theSwitch.targetBlockIndices()[0];
if (fallthroughBlockIndex < caseBlockIndex) {
block.swapSuccessorsByIndex(fallthroughBlockIndex, caseBlockIndex);
}
if (theSwitch.getFirstKey() == 0) {
iterator.replaceCurrentInstruction(new If(Type.EQ, theSwitch.value()));
} else {
ConstNumber labelConst = code.createIntConstant(theSwitch.getFirstKey());
labelConst.setPosition(theSwitch.getPosition());
iterator.previous();
iterator.add(labelConst);
Instruction dummy = iterator.next();
assert dummy == theSwitch;
If theIf = new If(Type.EQ, ImmutableList.of(theSwitch.value(), labelConst.dest()));
iterator.replaceCurrentInstruction(theIf);
}
} else {
// Split keys into outliers and sequences.
List<IntList> sequences = new ArrayList<>();
IntList outliers = new IntArrayList();
IntList current = new IntArrayList();
int[] keys = theSwitch.getKeys();
int previousKey = keys[0];
current.add(previousKey);
for (int i = 1; i < keys.length; i++) {
assert current.size() > 0;
assert current.getInt(current.size() - 1) == previousKey;
int key = keys[i];
if (((long) key - (long) previousKey) > 1) {
if (current.size() == 1) {
outliers.add(previousKey);
} else {
sequences.add(current);
}
current = new IntArrayList();
}
current.add(key);
previousKey = key;
}
if (current.size() == 1) {
outliers.add(previousKey);
} else {
sequences.add(current);
}
// Get the existing dex size for the payload and switch.
int currentSize = Switch.payloadSize(keys) + Switch.estimatedDexSize();
// Never replace with more than 10 if/switch instructions.
if (outliers.size() + sequences.size() <= 10) {
// Calculate estimated size for splitting into ifs and switches.
long rewrittenSize = 0;
for (Integer outlier : outliers) {
if (outlier != 0) {
rewrittenSize += ConstNumber.estimatedDexSize(
theSwitch.value().outType(), outlier);
}
rewrittenSize += If.estimatedDexSize();
}
for (List<Integer> sequence : sequences) {
rewrittenSize += Switch.payloadSize(sequence);
}
rewrittenSize += Switch.estimatedDexSize() * sequences.size();
if (rewrittenSize < currentSize) {
convertSwitchToSwitchAndIfs(
code, blocksIterator, block, iterator, theSwitch, sequences, outliers);
}
} else if (outliers.size() > 1) {
// Calculate estimated size for splitting into switches (packed for the sequences
// and sparse for the outliers).
long rewrittenSize = 0;
for (List<Integer> sequence : sequences) {
rewrittenSize += Switch.payloadSize(sequence);
}
rewrittenSize += Switch.payloadSize(outliers);
rewrittenSize += Switch.estimatedDexSize() * (sequences.size() + 1);
if (rewrittenSize < currentSize) {
// Create a copy to not modify sequences.
List<IntList> seqs = new ArrayList<>(sequences);
seqs.add(outliers);
convertSwitchToSwitchAndIfs(
code, blocksIterator, block, iterator, theSwitch, seqs, IntLists.EMPTY_LIST);
}
}
}
}
}
}
// Rewriting of switches introduces new branching structure. It relies on critical edges
// being split on the way in but does not maintain this property. We therefore split
// critical edges at exit.
code.splitCriticalEdges();
assert code.isConsistentSSA();
}
/**
* Inline the indirection of switch maps into the switch statement.
* <p>
* To ensure binary compatibility, javac generated code does not use ordinal values of enums
* directly in switch statements but instead generates a companion class that computes a mapping
* from switch branches to ordinals at runtime. As we have whole-program knowledge, we can
* analyze these maps and inline the indirection into the switch map again.
* <p>
* In particular, we look for code of the form
*
* <blockquote><pre>
* switch(CompanionClass.$switchmap$field[enumValue.ordinal()]) {
* ...
* }
* </pre></blockquote>
*/
public void removeSwitchMaps(IRCode code) {
for (BasicBlock block : code.blocks) {
InstructionListIterator it = block.listIterator();
while (it.hasNext()) {
Instruction insn = it.next();
// Pattern match a switch on a switch map as input.
if (insn.isSwitch()) {
Switch switchInsn = insn.asSwitch();
EnumSwitchInfo info = SwitchUtils
.analyzeSwitchOverEnum(switchInsn, appInfo.withLiveness());
if (info != null) {
Int2IntMap targetMap = new Int2IntArrayMap();
IntList keys = new IntArrayList(switchInsn.numberOfKeys());
for (int i = 0; i < switchInsn.numberOfKeys(); i++) {
assert switchInsn.targetBlockIndices()[i] != switchInsn.getFallthroughBlockIndex();
int key = info.ordinalsMap.getInt(info.indexMap.get(switchInsn.getKey(i)));
keys.add(key);
targetMap.put(key, switchInsn.targetBlockIndices()[i]);
}
keys.sort(Comparator.naturalOrder());
int[] targets = new int[keys.size()];
for (int i = 0; i < keys.size(); i++) {
targets[i] = targetMap.get(keys.getInt(i));
}
Switch newSwitch = new Switch(info.ordinalInvoke.outValue(), keys.toIntArray(),
targets, switchInsn.getFallthroughBlockIndex());
// Replace the switch itself.
it.replaceCurrentInstruction(newSwitch);
// If the original input to the switch is now unused, remove it too. It is not dead
// as it might have side-effects but we ignore these here.
Instruction arrayGet = info.arrayGet;
if (arrayGet.outValue().numberOfUsers() == 0) {
arrayGet.inValues().forEach(v -> v.removeUser(arrayGet));
arrayGet.getBlock().removeInstruction(arrayGet);
}
Instruction staticGet = info.staticGet;
if (staticGet.outValue().numberOfUsers() == 0) {
assert staticGet.inValues().isEmpty();
staticGet.getBlock().removeInstruction(staticGet);
}
}
}
}
}
}
/**
* Rewrite all branch targets to the destination of trivial goto chains when possible.
* Does not rewrite fallthrough targets as that would require block reordering and the
* transformation only makes sense after SSA destruction where there are no phis.
*/
public static void collapsTrivialGotos(DexEncodedMethod method, IRCode code) {
assert code.isConsistentGraph();
List<BasicBlock> blocksToRemove = new ArrayList<>();
// Rewrite all non-fallthrough targets to the end of trivial goto chains and remove
// first round of trivial goto blocks.
ListIterator<BasicBlock> iterator = code.listIterator();
assert iterator.hasNext();
BasicBlock block = iterator.next();
BasicBlock nextBlock;
// The marks will be used for cycle detection.
do {
nextBlock = iterator.hasNext() ? iterator.next() : null;
if (block.isTrivialGoto()) {
collapsTrivialGoto(code, block, nextBlock, blocksToRemove);
}
if (block.exit().isIf()) {
collapsIfTrueTarget(block);
}
if (block.exit().isSwitch()) {
collapsNonFallthroughSwitchTargets(block);
}
block = nextBlock;
} while (nextBlock != null);
code.removeBlocks(blocksToRemove);
// Get rid of gotos to the next block.
while (!blocksToRemove.isEmpty()) {
blocksToRemove = new ArrayList<>();
iterator = code.listIterator();
block = iterator.next();
do {
nextBlock = iterator.hasNext() ? iterator.next() : null;
if (block.isTrivialGoto()) {
collapsTrivialGoto(code, block, nextBlock, blocksToRemove);
}
block = nextBlock;
} while (block != null);
code.removeBlocks(blocksToRemove);
}
assert removedTrivialGotos(code);
assert code.isConsistentGraph();
}
public void identifyReturnsArgument(
DexEncodedMethod method, IRCode code, OptimizationFeedback feedback) {
List<BasicBlock> normalExits = code.computeNormalExitBlocks();
if (normalExits.isEmpty()) {
feedback.methodNeverReturnsNormally(method);
return;
}
Return firstExit = normalExits.get(0).exit().asReturn();
if (firstExit.isReturnVoid()) {
return;
}
Value returnValue = firstExit.returnValue();
boolean isNeverNull = returnValue.isNeverNull();
for (int i = 1; i < normalExits.size(); i++) {
Return exit = normalExits.get(i).exit().asReturn();
Value value = exit.returnValue();
if (value != returnValue) {
returnValue = null;
}
isNeverNull = isNeverNull && value.isNeverNull();
}
if (returnValue != null) {
if (returnValue.isArgument()) {
// Find the argument number.
int index = code.collectArguments().indexOf(returnValue);
assert index != -1;
feedback.methodReturnsArgument(method, index);
}
if (returnValue.isConstant() && returnValue.definition.isConstNumber()) {
long value = returnValue.definition.asConstNumber().getRawValue();
feedback.methodReturnsConstant(method, value);
}
}
if (isNeverNull) {
feedback.methodNeverReturnsNull(method);
}
}
public void identifyInvokeSemanticsForInlining(
DexEncodedMethod method, IRCode code, OptimizationFeedback feedback) {
if (method.isStaticMethod()) {
// Identifies if the method preserves class initialization after inlining.
feedback.markTriggerClassInitBeforeAnySideEffect(method,
triggersClassInitializationBeforeSideEffect(code, method.method.getHolder()));
} else {
// Identifies if the method preserves null check of the receiver after inlining.
final Value receiver = code.getThis();
feedback.markCheckNullReceiverBeforeAnySideEffect(method,
receiver.isUsed() && checksNullReceiverBeforeSideEffect(code, receiver));
}
}
public void identifyClassInlinerEligibility(
DexEncodedMethod method, IRCode code, OptimizationFeedback feedback) {
// Method eligibility is calculated in similar way for regular method
// and for the constructor. To be eligible method should only be using its
// receiver in the following ways:
//
// (1) as a receiver of reads/writes of instance fields of the holder class
// (2) as a return value
// (3) as a receiver of a call to the superclass initializer
//
boolean instanceInitializer = method.isInstanceInitializer();
if (method.accessFlags.isNative() ||
(!method.isNonAbstractVirtualMethod() && !instanceInitializer)) {
return;
}
feedback.setClassInlinerEligibility(method, null); // To allow returns below.
Value receiver = code.getThis();
if (receiver.numberOfPhiUsers() > 0) {
return;
}
boolean receiverUsedAsReturnValue = false;
boolean seenSuperInitCall = false;
for (Instruction insn : receiver.uniqueUsers()) {
if (insn.isReturn()) {
receiverUsedAsReturnValue = true;
continue;
}
if (insn.isInstanceGet() ||
(insn.isInstancePut() && insn.asInstancePut().object() == receiver)) {
DexField field = insn.asFieldInstruction().getField();
if (field.clazz == method.method.holder) {
// Since class inliner currently only supports classes directly extending
// java.lang.Object, we don't need to worry about fields defined in superclasses.
continue;
}
return;
}
// If this is an instance initializer allow one call
// to java.lang.Object.<init>() on 'this'.
if (instanceInitializer && insn.isInvokeDirect()) {
InvokeDirect invokedDirect = insn.asInvokeDirect();
if (invokedDirect.getInvokedMethod() == dexItemFactory.objectMethods.constructor &&
invokedDirect.getReceiver() == receiver &&
!seenSuperInitCall) {
seenSuperInitCall = true;
continue;
}
return;
}
// Other receiver usages make the method not eligible.
return;
}
if (instanceInitializer && !seenSuperInitCall) {
// Call to super constructor not found?
return;
}
feedback.setClassInlinerEligibility(
method, new ClassInlinerEligibility(receiverUsedAsReturnValue));
}
/**
* An enum used to classify instructions according to a particular effect that they produce.
*
* The "effect" of an instruction can be seen as a program state change (or semantic change) at
* runtime execution. For example, an instruction could cause the initialization of a class,
* change the value of a field, ... while other instructions do not.
*
* This classification also depends on the type of analysis that is using it. For instance, an
* analysis can look for instructions that cause class initialization while another look for
* instructions that check nullness of a particular object.
*
* On the other hand, some instructions may provide a non desired effect which is a signal for
* the analysis to stop.
*/
private enum InstructionEffect {
DESIRED_EFFECT,
OTHER_EFFECT,
NO_EFFECT
}
/**
* Returns true if the given code unconditionally throws if receiver is null before any other
* side effect instruction.
*
* Note: we do not track phis so we may return false negative. This is a conservative approach.
*/
private static boolean checksNullReceiverBeforeSideEffect(IRCode code, Value receiver) {
return alwaysTriggerExpectedEffectBeforeAnythingElse(code, instr -> {
if (instr.throwsNpeIfValueIsNull(receiver)) {
// In order to preserve NPE semantic, the exception must not be caught by any handler.
// Therefore, we must ignore this instruction if it is covered by a catch handler.
// Note: this is a conservative approach where we consider that any catch handler could
// catch the exception, even if it cannot catch a NullPointerException.
if (!instr.getBlock().hasCatchHandlers()) {
// We found a NPE check on receiver.
return InstructionEffect.DESIRED_EFFECT;
}
} else if (instructionHasSideEffects(instr)) {
// We found a side effect before a NPE check.
return InstructionEffect.OTHER_EFFECT;
}
return InstructionEffect.NO_EFFECT;
});
}
private static boolean instructionHasSideEffects(Instruction instruction) {
// We consider that an instruction has side effects if it can throw an exception. This is a
// conservative approach which can be revised in the future.
return instruction.instructionTypeCanThrow();
}
/**
* Returns true if the given code unconditionally triggers class initialization before any other
* side effecting instruction.
*
* Note: we do not track phis so we may return false negative. This is a conservative approach.
*/
private static boolean triggersClassInitializationBeforeSideEffect(IRCode code, DexType klass) {
return alwaysTriggerExpectedEffectBeforeAnythingElse(code, instruction -> {
if (instruction.triggersInitializationOfClass(klass)) {
// In order to preserve class initialization semantic, the exception must not be caught by
// any handler. Therefore, we must ignore this instruction if it is covered by a catch
// handler.
// Note: this is a conservative approach where we consider that any catch handler could
// catch the exception, even if it cannot catch an ExceptionInInitializerError.
if (!instruction.getBlock().hasCatchHandlers()) {
// We found an instruction that preserves initialization of the class.
return InstructionEffect.DESIRED_EFFECT;
}
} else if (instructionHasSideEffects(instruction)) {
// We found a side effect before class initialization.
return InstructionEffect.OTHER_EFFECT;
}
return InstructionEffect.NO_EFFECT;
});
}
/**
* Returns true if the given code unconditionally triggers an expected effect before anything
* else, false otherwise.
*
* Note: we do not track phis so we may return false negative. This is a conservative approach.
*/
private static boolean alwaysTriggerExpectedEffectBeforeAnythingElse(IRCode code,
Function<Instruction, InstructionEffect> function) {
final int color = code.reserveMarkingColor();
try {
ArrayDeque<BasicBlock> worklist = new ArrayDeque<>();
final BasicBlock entry = code.blocks.getFirst();
worklist.add(entry);
entry.mark(color);
while (!worklist.isEmpty()) {
BasicBlock currentBlock = worklist.poll();
assert currentBlock.isMarked(color);
InstructionEffect result = InstructionEffect.NO_EFFECT;
Iterator<Instruction> it = currentBlock.listIterator();
while (result == InstructionEffect.NO_EFFECT && it.hasNext()) {
result = function.apply(it.next());
}
if (result == InstructionEffect.OTHER_EFFECT) {
// We found an instruction that is causing an unexpected side effect.
return false;
} else if (result == InstructionEffect.DESIRED_EFFECT) {
// The current path is causing the expected effect. No need to go deeper in this path,
// go to the next block in the work list.
continue;
} else {
assert result == InstructionEffect.NO_EFFECT;
// The block did not cause any particular effect.
if (currentBlock.getNormalSuccessors().isEmpty()) {
// This is the end of the current non-exceptional path and we did not find any expected
// effect. It means there is at least one path where the expected effect does not
// happen.
Instruction lastInstruction = currentBlock.getInstructions().getLast();
assert lastInstruction.isReturn() || lastInstruction.isThrow();
return false;
} else {
// Look into successors
for (BasicBlock successor : currentBlock.getSuccessors()) {
if (!successor.isMarked(color)) {
worklist.add(successor);
successor.mark(color);
}
}
}
}
}
// If we reach this point, we checked that the expected effect happens in every possible path.
return true;
} finally {
code.returnMarkingColor(color);
}
}
private boolean checkArgumentType(InvokeMethod invoke, DexMethod target, int argumentIndex) {
DexType returnType = invoke.getInvokedMethod().proto.returnType;
// TODO(sgjesse): Insert cast if required.
if (invoke.isInvokeStatic()) {
return invoke.getInvokedMethod().proto.parameters.values[argumentIndex] == returnType;
} else {
if (argumentIndex == 0) {
return invoke.getInvokedMethod().getHolder() == returnType;
} else {
return invoke.getInvokedMethod().proto.parameters.values[argumentIndex - 1] == returnType;
}
}
}
// Replace result uses for methods where something is known about what is returned.
public void rewriteMoveResult(IRCode code) {
if (options.isGeneratingClassFiles()) {
return;
}
AppInfoWithLiveness appInfoWithLiveness = appInfo.withLiveness();
InstructionIterator iterator = code.instructionIterator();
while (iterator.hasNext()) {
Instruction current = iterator.next();
if (current.isInvokeMethod()) {
InvokeMethod invoke = current.asInvokeMethod();
if (invoke.outValue() != null && !invoke.outValue().hasLocalInfo()) {
boolean isLibraryMethodReturningReceiver =
libraryMethodsReturningReceiver.contains(invoke.getInvokedMethod());
if (isLibraryMethodReturningReceiver) {
if (checkArgumentType(invoke, invoke.getInvokedMethod(), 0)) {
invoke.outValue().replaceUsers(invoke.arguments().get(0));
invoke.setOutValue(null);
}
} else if (appInfoWithLiveness != null) {
DexEncodedMethod target = invoke.computeSingleTarget(appInfoWithLiveness);
if (target != null) {
DexMethod invokedMethod = target.method;
// Check if the invoked method is known to return one of its arguments.
DexEncodedMethod definition = appInfo.definitionFor(invokedMethod);
if (definition != null && definition.getOptimizationInfo().returnsArgument()) {
int argumentIndex = definition.getOptimizationInfo().getReturnedArgument();
// Replace the out value of the invoke with the argument and ignore the out value.
if (argumentIndex != -1 && checkArgumentType(invoke, target.method,
argumentIndex)) {
Value argument = invoke.arguments().get(argumentIndex);
assert invoke.outType().verifyCompatible(argument.outType());
invoke.outValue().replaceUsers(argument);
invoke.setOutValue(null);
}
}
}
}
}
}
}
assert code.isConsistentGraph();
}
/**
* For supporting assert javac adds the static field $assertionsDisabled to all classes which
* have methods with assertions. This is used to support the Java VM -ea flag.
*
* The class:
* <pre>
* class A {
* void m() {
* assert xxx;
* }
* }
* </pre>
* Is compiled into:
* <pre>
* class A {
* static boolean $assertionsDisabled;
* static {
* $assertionsDisabled = A.class.desiredAssertionStatus();
* }
*
* // method with "assert xxx";
* void m() {
* if (!$assertionsDisabled) {
* if (xxx) {
* throw new AssertionError(...);
* }
* }
* }
* }
* </pre>
* With the rewriting below (and other rewritings) the resulting code is:
* <pre>
* class A {
* void m() {
* }
* }
* </pre>
*/
public void disableAssertions(IRCode code) {
InstructionIterator iterator = code.instructionIterator();
while (iterator.hasNext()) {
Instruction current = iterator.next();
if (current.isInvokeMethod()) {
InvokeMethod invoke = current.asInvokeMethod();
if (invoke.getInvokedMethod() == dexItemFactory.classMethods.desiredAssertionStatus) {
iterator.replaceCurrentInstruction(code.createFalse());
}
} else if (current.isStaticPut()) {
StaticPut staticPut = current.asStaticPut();
if (staticPut.getField().name == dexItemFactory.assertionsDisabled) {
iterator.remove();
}
} else if (current.isStaticGet()) {
StaticGet staticGet = current.asStaticGet();
if (staticGet.getField().name == dexItemFactory.assertionsDisabled) {
iterator.replaceCurrentInstruction(code.createTrue());
}
}
}
}
// Check if the static put is a constant derived from the class holding the method.
// This checks for java.lang.Class.getName and java.lang.Class.getSimpleName.
private boolean isClassNameConstant(DexEncodedMethod method, StaticPut put) {
if (put.getField().type != dexItemFactory.stringType) {
return false;
}
if (put.inValue().definition != null && put.inValue().definition.isInvokeVirtual()) {
InvokeVirtual invoke = put.inValue().definition.asInvokeVirtual();
if ((invoke.getInvokedMethod() == dexItemFactory.classMethods.getSimpleName
|| invoke.getInvokedMethod() == dexItemFactory.classMethods.getName)
&& !invoke.inValues().get(0).isPhi()
&& invoke.inValues().get(0).definition.isConstClass()
&& invoke.inValues().get(0).definition.asConstClass().getValue()
== method.method.getHolder()) {
return true;
}
}
return false;
}
public void collectClassInitializerDefaults(DexEncodedMethod method, IRCode code) {
if (!method.isClassInitializer()) {
return;
}
// Collect relevant static put which are dominated by the exit block, and not dominated by a
// static get.
// This does not check for instructions that can throw. However, as classes which throw in the
// class initializer are never visible to the program (see Java Virtual Machine Specification
// section 5.5, https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-5.html#jvms-5.5), this
// does not matter (except maybe for removal of const-string instructions, but that is
// acceptable).
if (code.computeNormalExitBlocks().isEmpty()) {
return;
}
DexClass clazz = definitionFor(method.method.getHolder());
assert clazz != null;
DominatorTree dominatorTree = new DominatorTree(code);
Set<StaticPut> puts = Sets.newIdentityHashSet();
Map<DexField, StaticPut> dominatingPuts = Maps.newIdentityHashMap();
for (BasicBlock block : dominatorTree.normalExitDominatorBlocks()) {
InstructionListIterator iterator = block.listIterator(block.getInstructions().size());
while (iterator.hasPrevious()) {
Instruction current = iterator.previous();
if (current.isStaticPut()) {
StaticPut put = current.asStaticPut();
DexField field = put.getField();
if (clazz.definesStaticField(field)) {
if (put.inValue().isConstant()) {
if ((field.type.isClassType() || field.type.isArrayType())
&& put.inValue().isZero()) {
// Collect put of zero as a potential default value.
dominatingPuts.putIfAbsent(put.getField(), put);
puts.add(put);
} else if (field.type.isPrimitiveType() || field.type == dexItemFactory.stringType) {
// Collect put as a potential default value.
dominatingPuts.putIfAbsent(put.getField(), put);
puts.add(put);
}
} else if (isClassNameConstant(method, put)) {
// Collect put of class name constant as a potential default value.
dominatingPuts.putIfAbsent(put.getField(), put);
puts.add(put);
}
}
}
if (current.isStaticGet()) {
// If a static field is read, any collected potential default value cannot be a
// default value.
DexField field = current.asStaticGet().getField();
if (dominatingPuts.containsKey(field)) {
dominatingPuts.remove(field);
Iterables.removeIf(puts, put -> put.getField() == field);
}
}
}
}
if (!puts.isEmpty()) {
// Set initial values for static fields from the definitive static put instructions collected.
for (StaticPut put : dominatingPuts.values()) {
DexField field = put.getField();
DexEncodedField encodedField = appInfo.definitionFor(field);
if (field.type == dexItemFactory.stringType) {
if (put.inValue().isConstant()) {
if (put.inValue().isConstNumber()) {
assert put.inValue().isZero();
encodedField.setStaticValue(DexValueNull.NULL);
} else {
ConstString cnst = put.inValue().getConstInstruction().asConstString();
encodedField.setStaticValue(new DexValueString(cnst.getValue()));
}
} else {
InvokeVirtual invoke = put.inValue().definition.asInvokeVirtual();
String name = method.method.getHolder().toSourceString();
if (invoke.getInvokedMethod() == dexItemFactory.classMethods.getSimpleName) {
String simpleName = name.substring(name.lastIndexOf('.') + 1);
encodedField.setStaticValue(
new DexValueString(dexItemFactory.createString(simpleName)));
} else {
assert invoke.getInvokedMethod() == dexItemFactory.classMethods.getName;
encodedField.setStaticValue(new DexValueString(dexItemFactory.createString(name)));
}
}
} else if (field.type.isClassType() || field.type.isArrayType()) {
if (put.inValue().isZero()) {
encodedField.setStaticValue(DexValueNull.NULL);
} else {
throw new Unreachable("Unexpected default value for field type " + field.type + ".");
}
} else {
ConstNumber cnst = put.inValue().getConstInstruction().asConstNumber();
if (field.type == dexItemFactory.booleanType) {
encodedField.setStaticValue(DexValueBoolean.create(cnst.getBooleanValue()));
} else if (field.type == dexItemFactory.byteType) {
encodedField.setStaticValue(DexValueByte.create((byte) cnst.getIntValue()));
} else if (field.type == dexItemFactory.shortType) {
encodedField.setStaticValue(DexValueShort.create((short) cnst.getIntValue()));
} else if (field.type == dexItemFactory.intType) {
encodedField.setStaticValue(DexValueInt.create(cnst.getIntValue()));
} else if (field.type == dexItemFactory.longType) {
encodedField.setStaticValue(DexValueLong.create(cnst.getLongValue()));
} else if (field.type == dexItemFactory.floatType) {
encodedField.setStaticValue(DexValueFloat.create(cnst.getFloatValue()));
} else if (field.type == dexItemFactory.doubleType) {
encodedField.setStaticValue(DexValueDouble.create(cnst.getDoubleValue()));
} else if (field.type == dexItemFactory.charType) {
encodedField.setStaticValue(DexValueChar.create((char) cnst.getIntValue()));
} else {
throw new Unreachable("Unexpected field type " + field.type + ".");
}
}
}
// Remove the static put instructions now replaced by static filed initial values.
List<Instruction> toRemove = new ArrayList<>();
for (BasicBlock block : dominatorTree.normalExitDominatorBlocks()) {
InstructionListIterator iterator = block.listIterator();
while (iterator.hasNext()) {
Instruction current = iterator.next();
if (current.isStaticPut() && puts.contains(current.asStaticPut())) {
iterator.remove();
// Collect, for removal, the instruction that created the value for the static put,
// if all users are gone. This is done even if these instructions can throw as for
// the current patterns matched these exceptions are not detectable.
StaticPut put = current.asStaticPut();
if (put.inValue().uniqueUsers().size() == 0) {
if (put.inValue().isConstString()) {
toRemove.add(put.inValue().definition);
} else if (put.inValue().definition.isInvokeVirtual()) {
toRemove.add(put.inValue().definition);
}
}
}
}
}
// Remove the instructions collected for removal.
if (toRemove.size() > 0) {
for (BasicBlock block : dominatorTree.normalExitDominatorBlocks()) {
InstructionListIterator iterator = block.listIterator();
while (iterator.hasNext()) {
if (toRemove.contains(iterator.next())) {
iterator.remove();
}
}
}
}
}
}
private DexClass definitionFor(DexType type) {
if (cachedClass != null && cachedClass.type == type) {
return cachedClass;
}
return appInfo.definitionFor(type);
}
public void enterCachedClass(DexProgramClass clazz) {
assert cachedClass == null;
cachedClass = clazz;
}
public void leaveCachedClass(DexProgramClass clazz) {
assert cachedClass == clazz;
cachedClass = null;
}
public void removeCasts(IRCode code, TypeEnvironment typeEnvironment) {
InstructionIterator it = code.instructionIterator();
boolean needToRemoveTrivialPhis = false;
while (it.hasNext()) {
Instruction current = it.next();
if (!current.isCheckCast()) {
continue;
}
CheckCast checkCast = current.asCheckCast();
Value inValue = checkCast.object();
Value outValue = checkCast.outValue();
DexType castType = checkCast.getType();
// We might see chains of casts on subtypes. It suffices to cast to the lowest subtype,
// as that will fail if a cast on a supertype would have failed.
Predicate<Instruction> isCheckcastToSubtype =
user -> user.isCheckCast() && user.asCheckCast().getType().isSubtypeOf(castType, appInfo);
if (!checkCast.getBlock().hasCatchHandlers()
&& outValue.isUsed()
&& outValue.numberOfPhiUsers() == 0
&& outValue.uniqueUsers().stream().allMatch(isCheckcastToSubtype)) {
removeOrReplaceByDebugLocalWrite(it, inValue, outValue);
continue;
}
TypeLatticeElement inTypeLattice = typeEnvironment.getLatticeElement(inValue);
if (!inTypeLattice.isTop()) {
TypeLatticeElement outTypeLattice = typeEnvironment.getLatticeElement(outValue);
TypeLatticeElement castTypeLattice =
TypeLatticeElement.fromDexType(castType, inTypeLattice.isNullable());
// Special case: null cast, e.g., getMethod(..., (Class[]) null);
// This cast should be kept no matter what.
if (inTypeLattice.mustBeNull()) {
assert outTypeLattice.equals(castTypeLattice);
continue;
}
// 1) Trivial cast.
// A a = ...
// A a' = (A) a;
// 2) Up-cast: we already have finer type info.
// A < B
// A a = ...
// B b = (B) a;
if (TypeLatticeElement.lessThanOrEqual(appInfo, inTypeLattice, castTypeLattice)) {
assert outTypeLattice.equals(inTypeLattice);
needToRemoveTrivialPhis = needToRemoveTrivialPhis || outValue.numberOfPhiUsers() != 0;
removeOrReplaceByDebugLocalWrite(it, inValue, outValue);
continue;
}
// Otherwise, keep the checkcast to preserve verification errors. E.g., down-cast:
// A < B < C
// c = ... // Even though we know c is of type A,
// a' = (B) c; // (this could be removed, since chained below.)
// a'' = (A) a'; // this should remain for runtime verification.
assert outTypeLattice.equals(castTypeLattice);
}
}
// ... v1
// ...
// v2 <- check-cast v1, T
// v3 <- phi(v1, v2)
// Removing check-cast may result in a trivial phi:
// v3 <- phi(v1, v1)
if (needToRemoveTrivialPhis) {
code.removeAllTrivialPhis();
}
it = code.instructionIterator();
assert code.isConsistentSSA();
}
private void removeOrReplaceByDebugLocalWrite(
InstructionIterator it, Value inValue, Value outValue) {
if (outValue.getLocalInfo() != inValue.getLocalInfo() && outValue.hasLocalInfo()) {
DebugLocalWrite debugLocalWrite = new DebugLocalWrite(outValue, inValue);
it.replaceCurrentInstruction(debugLocalWrite);
} else {
outValue.replaceUsers(inValue);
it.removeOrReplaceByDebugLocalRead();
}
}
private boolean canBeFolded(Instruction instruction) {
return (instruction.isBinop() && instruction.asBinop().canBeFolded()) ||
(instruction.isUnop() && instruction.asUnop().canBeFolded());
}
// Split constants that flow into ranged invokes. This gives the register allocator more
// freedom in assigning register to ranged invokes which can greatly reduce the number
// of register needed (and thereby code size as well).
public void splitRangeInvokeConstants(IRCode code) {
for (BasicBlock block : code.blocks) {
InstructionListIterator it = block.listIterator();
while (it.hasNext()) {
Instruction current = it.next();
if (current.isInvoke() && current.asInvoke().requiredArgumentRegisters() > 5) {
Invoke invoke = current.asInvoke();
it.previous();
Map<ConstNumber, ConstNumber> oldToNew = new IdentityHashMap<>();
for (int i = 0; i < invoke.inValues().size(); i++) {
Value value = invoke.inValues().get(i);
if (value.isConstNumber() && value.numberOfUsers() > 1) {
ConstNumber definition = value.getConstInstruction().asConstNumber();
Value originalValue = definition.outValue();
ConstNumber newNumber = oldToNew.get(definition);
if (newNumber == null) {
newNumber = ConstNumber.copyOf(code, definition);
it.add(newNumber);
newNumber.setPosition(current.getPosition());
oldToNew.put(definition, newNumber);
}
invoke.inValues().set(i, newNumber.outValue());
originalValue.removeUser(invoke);
newNumber.outValue().addUser(invoke);
}
}
it.next();
}
}
}
}
/**
* If an instruction is known to be a /lit8 or /lit16 instruction, update the instruction to use
* its own constant that will be defined just before the instruction. This transformation allows
* to decrease pressure on register allocation by defining the shortest range of constant used
* by this kind of instruction. D8 knowns at build time that constant will be encoded
* directly into the final Dex instruction.
*/
public void useDedicatedConstantForLitInstruction(IRCode code) {
for (BasicBlock block : code.blocks) {
InstructionListIterator instructionIterator = block.listIterator();
while (instructionIterator.hasNext()) {
Instruction currentInstruction = instructionIterator.next();
if (shouldBeLitInstruction(currentInstruction)) {
assert currentInstruction.isBinop();
Binop binop = currentInstruction.asBinop();
Value constValue;
if (binop.leftValue().isConstNumber()) {
constValue = binop.leftValue();
} else if (binop.rightValue().isConstNumber()) {
constValue = binop.rightValue();
} else {
throw new Unreachable();
}
if (constValue.numberOfAllUsers() > 1) {
// No need to do the transformation if the const value is already used only one time.
ConstNumber newConstant = ConstNumber
.copyOf(code, constValue.definition.asConstNumber());
newConstant.setPosition(currentInstruction.getPosition());
newConstant.setBlock(currentInstruction.getBlock());
currentInstruction.replaceValue(constValue, newConstant.outValue());
constValue.removeUser(currentInstruction);
instructionIterator.previous();
instructionIterator.add(newConstant);
instructionIterator.next();
}
}
}
}
assert code.isConsistentSSA();
}
/**
* A /lit8 or /lit16 instruction only concerns arithmetic or logical instruction. /lit8 or /lit16
* instructions generate bigger code than 2addr instructions, thus we favor 2addr instructions
* rather than /lit8 or /lit16 instructions.
*/
private static boolean shouldBeLitInstruction(Instruction instruction) {
if (instruction.isArithmeticBinop() || instruction.isLogicalBinop()) {
Binop binop = instruction.asBinop();
if (!binop.needsValueInRegister(binop.leftValue()) ||
!binop.needsValueInRegister(binop.rightValue())) {
return !canBe2AddrInstruction(binop);
}
}
return false;
}
/**
* Estimate if a binary operation can be a 2addr form or not. It can be a 2addr form when an
* argument is no longer needed after the binary operation and can be overwritten. That is
* definitely the case if there is no path between the binary operation and all other usages.
*/
private static boolean canBe2AddrInstruction(Binop binop) {
Value value = null;
if (binop.needsValueInRegister(binop.leftValue())) {
value = binop.leftValue();
} else if (binop.isCommutative() && binop.needsValueInRegister(binop.rightValue())) {
value = binop.rightValue();
}
if (value != null) {
Iterable<Instruction> users = value.debugUsers() != null ?
Iterables.concat(value.uniqueUsers(), value.debugUsers()) : value.uniqueUsers();
for (Instruction user : users) {
if (hasPath(binop, user)) {
return false;
}
}
Iterable<Phi> phiUsers = value.debugPhiUsers() != null
? Iterables.concat(value.uniquePhiUsers(), value.debugPhiUsers())
: value.uniquePhiUsers();
for (Phi user : phiUsers) {
if (binop.getBlock().hasPathTo(user.getBlock())) {
return false;
}
}
}
return true;
}
/**
* Return true if there is a path between {@code source} instruction and {@code target}
* instruction.
*/
private static boolean hasPath(Instruction source, Instruction target) {
BasicBlock sourceBlock = source.getBlock();
BasicBlock targetBlock = target.getBlock();
if (sourceBlock == targetBlock) {
return sourceBlock.getInstructions().indexOf(source) <
targetBlock.getInstructions().indexOf(target);
}
return source.getBlock().hasPathTo(targetBlock);
}
public void shortenLiveRanges(IRCode code) {
// Currently, we are only shortening the live range of ConstNumbers in the entry block
// and ConstStrings with one user.
// TODO(ager): Generalize this to shorten live ranges for more instructions? Currently
// doing so seems to make things worse.
Supplier<DominatorTree> dominatorTreeMemoization =
Suppliers.memoize(() -> new DominatorTree(code));
Map<BasicBlock, List<Instruction>> addConstantInBlock = new HashMap<>();
LinkedList<BasicBlock> blocks = code.blocks;
for (int i = 0; i < blocks.size(); i++) {
BasicBlock block = blocks.get(i);
if (i == 0) {
// For the first block process all ConstNumber instructions
// as well as ConstString instructions having just one use.
shortenLiveRangesInsideBlock(block, dominatorTreeMemoization, addConstantInBlock,
insn -> (insn.isConstNumber() && insn.outValue().numberOfAllUsers() != 0)
|| (insn.isConstString() && insn.outValue().numberOfAllUsers() == 1));
} else {
// For all following blocks only process ConstString with just one use.
shortenLiveRangesInsideBlock(block, dominatorTreeMemoization, addConstantInBlock,
insn -> insn.isConstString() && insn.outValue().numberOfAllUsers() == 1);
}
}
// Heuristic to decide if constant instructions are shared in dominator block
// of usages or move to the usages.
// Process all blocks in stable order to avoid non-determinism of hash map iterator.
for (BasicBlock block : blocks) {
List<Instruction> instructions = addConstantInBlock.get(block);
if (instructions == null) {
continue;
}
if (block != blocks.get(0) && instructions.size() > STOP_SHARED_CONSTANT_THRESHOLD) {
// Too much constants in the same block, do not longer share them except if they are used
// by phi instructions or they are a sting constants.
for (Instruction instruction : instructions) {
if (instruction.outValue().numberOfPhiUsers() != 0 || instruction.isConstString()) {
// Add constant into the dominator block of usages.
insertConstantInBlock(instruction, block);
} else {
assert instruction.isConstNumber();
ConstNumber constNumber = instruction.asConstNumber();
Value constantValue = instruction.outValue();
assert constantValue.numberOfUsers() != 0;
assert constantValue.numberOfUsers() == constantValue.numberOfAllUsers();
for (Instruction user : constantValue.uniqueUsers()) {
ConstNumber newCstNum = ConstNumber.copyOf(code, constNumber);
newCstNum.setPosition(user.getPosition());
InstructionListIterator iterator = user.getBlock().listIterator(user);
iterator.previous();
iterator.add(newCstNum);
user.replaceValue(constantValue, newCstNum.outValue());
}
constantValue.clearUsers();
}
}
} else {
// Add constant into the dominator block of usages.
for (Instruction instruction : instructions) {
insertConstantInBlock(instruction, block);
}
}
}
assert code.isConsistentSSA();
}
private void shortenLiveRangesInsideBlock(BasicBlock block,
Supplier<DominatorTree> dominatorTreeMemoization,
Map<BasicBlock, List<Instruction>> addConstantInBlock,
Predicate<Instruction> selector) {
InstructionListIterator it = block.listIterator();
while (it.hasNext()) {
Instruction instruction = it.next();
if (!selector.test(instruction) || instruction.outValue().hasLocalInfo()) {
continue;
}
// Collect the blocks for all users of the constant.
List<BasicBlock> userBlocks = new LinkedList<>();
for (Instruction user : instruction.outValue().uniqueUsers()) {
userBlocks.add(user.getBlock());
}
for (Phi phi : instruction.outValue().uniquePhiUsers()) {
userBlocks.add(phi.getBlock());
}
// Locate the closest dominator block for all user blocks.
DominatorTree dominatorTree = dominatorTreeMemoization.get();
BasicBlock dominator = dominatorTree.closestDominator(userBlocks);
// If the closest dominator block is a block that uses the constant for a phi the constant
// needs to go in the immediate dominator block so that it is available for phi moves.
for (Phi phi : instruction.outValue().uniquePhiUsers()) {
if (phi.getBlock() == dominator) {
if (instruction.outValue().numberOfAllUsers() == 1 &&
phi.usesValueOneTime(instruction.outValue())) {
// Out value is used only one time, move the constant directly to the corresponding
// branch rather than into the dominator to avoid to generate a const on paths which
// does not required it.
int predIndex = phi.getOperands().indexOf(instruction.outValue());
dominator = dominator.getPredecessors().get(predIndex);
} else {
dominator = dominatorTree.immediateDominator(dominator);
}
break;
}
}
if (instruction.instructionTypeCanThrow()) {
if (block.hasCatchHandlers() || dominator.hasCatchHandlers()) {
// Do not move the constant if the constant instruction can throw
// and the dominator or the original block has catch handlers.
continue;
}
if (!dominator.isSimpleAlwaysThrowingPath()) {
// Only move string constants into blocks being part of simple
// always throwing path.
continue;
}
}
// Move the const instruction as close to its uses as possible.
it.detach();
List<Instruction> csts =
addConstantInBlock.computeIfAbsent(dominator, k -> new ArrayList<>());
csts.add(instruction);
}
}
private void insertConstantInBlock(Instruction instruction, BasicBlock block) {
boolean hasCatchHandlers = block.hasCatchHandlers();
InstructionListIterator insertAt = block.listIterator();
// Place the instruction as late in the block as we can. It needs to go before users
// and if we have catch handlers it needs to be placed before the throwing instruction.
// Also, in an attempt to help Art VMs with broken bounds check elimination code,
// we also do not lower the constants past array-length instructions in their
// target block. See comment on options.canHaveBoundsCheckEliminationBug.
insertAt.nextUntil(i ->
i.inValues().contains(instruction.outValue())
|| i.isJumpInstruction()
|| (hasCatchHandlers && i.instructionTypeCanThrow()));
Instruction next = insertAt.previous();
instruction.forceSetPosition(
next.isGoto() ? next.asGoto().getTarget().getPosition() : next.getPosition());
insertAt.add(instruction);
}
private short[] computeArrayFilledData(ConstInstruction[] values, int size, int elementSize) {
if (values == null) {
return null;
}
if (elementSize == 1) {
short[] result = new short[(size + 1) / 2];
for (int i = 0; i < size; i += 2) {
short value = (short) (values[i].asConstNumber().getIntValue() & 0xFF);
if (i + 1 < size) {
value |= (short) ((values[i + 1].asConstNumber().getIntValue() & 0xFF) << 8);
}
result[i / 2] = value;
}
return result;
}
assert elementSize == 2 || elementSize == 4 || elementSize == 8;
int shortsPerConstant = elementSize / 2;
short[] result = new short[size * shortsPerConstant];
for (int i = 0; i < size; i++) {
long value = values[i].asConstNumber().getRawValue();
for (int part = 0; part < shortsPerConstant; part++) {
result[i * shortsPerConstant + part] = (short) ((value >> (16 * part)) & 0xFFFFL);
}
}
return result;
}
private ConstInstruction[] computeConstantArrayValues(
NewArrayEmpty newArray, BasicBlock block, int size) {
if (size > MAX_FILL_ARRAY_SIZE) {
return null;
}
ConstInstruction[] values = new ConstInstruction[size];
int remaining = size;
Set<Instruction> users = newArray.outValue().uniqueUsers();
Set<BasicBlock> visitedBlocks = Sets.newIdentityHashSet();
// We allow the array instantiations to cross block boundaries as long as it hasn't encountered
// an instruction instance that can throw an exception.
InstructionListIterator it = block.listIterator();
it.nextUntil(i -> i == newArray);
do {
visitedBlocks.add(block);
while (it.hasNext()) {
Instruction instruction = it.next();
// If we encounter an instruction that can throw an exception we need to bail out of the
// optimization so that we do not transform half-initialized arrays into fully initialized
// arrays on exceptional edges. If the block has no handlers it is not observable so
// we perform the rewriting.
if (block.hasCatchHandlers() && instruction.instructionInstanceCanThrow()) {
return null;
}
if (!users.contains(instruction)) {
continue;
}
// If the initialization sequence is broken by another use we cannot use a
// fill-array-data instruction.
if (!instruction.isArrayPut()) {
return null;
}
ArrayPut arrayPut = instruction.asArrayPut();
if (!(arrayPut.value().isConstant() && arrayPut.index().isConstNumber())) {
return null;
}
int index = arrayPut.index().getConstInstruction().asConstNumber().getIntValue();
assert index >= 0 && index < values.length;
if (values[index] != null) {
return null;
}
ConstInstruction value = arrayPut.value().getConstInstruction();
values[index] = value;
--remaining;
if (remaining == 0) {
return values;
}
}
BasicBlock nextBlock = block.exit().isGoto() ? block.exit().asGoto().getTarget() : null;
block = nextBlock != null && !visitedBlocks.contains(nextBlock) ? nextBlock : null;
it = block != null ? block.listIterator() : null;
} while (it != null);
return null;
}
private boolean allowNewFilledArrayConstruction(Instruction instruction) {
if (!(instruction instanceof NewArrayEmpty)) {
return false;
}
NewArrayEmpty newArray = instruction.asNewArrayEmpty();
if (!newArray.size().isConstant()) {
return false;
}
assert newArray.size().isConstNumber();
int size = newArray.size().getConstInstruction().asConstNumber().getIntValue();
if (size < 1) {
return false;
}
if (newArray.type.isPrimitiveArrayType()) {
return true;
}
return newArray.type == dexItemFactory.stringArrayType
&& options.canUseFilledNewArrayOfObjects();
}
/**
* Replace new-array followed by stores of constants to all entries with new-array
* and fill-array-data / filled-new-array.
*/
public void simplifyArrayConstruction(IRCode code) {
if (options.isGeneratingClassFiles()) {
return;
}
for (BasicBlock block : code.blocks) {
// Map from the array value to the number of array put instruction to remove for that value.
Map<Value, Instruction> instructionToInsertForArray = new HashMap<>();
Map<Value, Integer> storesToRemoveForArray = new HashMap<>();
// First pass: identify candidates and insert fill array data instruction.
InstructionListIterator it = block.listIterator();
while (it.hasNext()) {
Instruction instruction = it.next();
if (instruction.getLocalInfo() != null
|| !allowNewFilledArrayConstruction(instruction)) {
continue;
}
NewArrayEmpty newArray = instruction.asNewArrayEmpty();
int size = newArray.size().getConstInstruction().asConstNumber().getIntValue();
ConstInstruction[] values = computeConstantArrayValues(newArray, block, size);
if (values == null) {
continue;
}
if (newArray.type == dexItemFactory.stringArrayType) {
// Don't replace with filled-new-array if it requires more than 200 consecutive registers.
if (size > 200) {
continue;
}
List<Value> stringValues = new ArrayList<>(size);
for (ConstInstruction value : values) {
stringValues.add(value.outValue());
}
InvokeNewArray invoke = new InvokeNewArray(
dexItemFactory.stringArrayType, newArray.outValue(), stringValues);
invoke.setPosition(newArray.getPosition());
it.detach();
for (Value value : newArray.inValues()) {
value.removeUser(newArray);
}
instructionToInsertForArray.put(newArray.outValue(), invoke);
} else {
// If there is only one element it is typically smaller to generate the array put
// instruction instead of fill array data.
if (size == 1) {
continue;
}
int elementSize = newArray.type.elementSizeForPrimitiveArrayType();
short[] contents = computeArrayFilledData(values, size, elementSize);
if (contents == null) {
continue;
}
int arraySize = newArray.size().getConstInstruction().asConstNumber().getIntValue();
NewArrayFilledData fillArray = new NewArrayFilledData(
newArray.outValue(), elementSize, arraySize, contents);
fillArray.setPosition(newArray.getPosition());
it.add(fillArray);
}
storesToRemoveForArray.put(newArray.outValue(), size);
}
// Second pass: remove all the array put instructions for the array for which we have
// inserted a fill array data instruction instead.
if (!storesToRemoveForArray.isEmpty()) {
Set<BasicBlock> visitedBlocks = Sets.newIdentityHashSet();
do {
visitedBlocks.add(block);
it = block.listIterator();
while (it.hasNext()) {
Instruction instruction = it.next();
if (instruction.isArrayPut()) {
Value array = instruction.asArrayPut().array();
Integer toRemoveCount = storesToRemoveForArray.get(array);
if (toRemoveCount != null) {
if (toRemoveCount > 0) {
storesToRemoveForArray.put(array, --toRemoveCount);
it.remove();
}
if (toRemoveCount == 0) {
storesToRemoveForArray.put(array, --toRemoveCount);
Instruction construction = instructionToInsertForArray.get(array);
if (construction != null) {
it.add(construction);
}
}
}
}
}
BasicBlock nextBlock = block.exit().isGoto() ? block.exit().asGoto().getTarget() : null;
block = nextBlock != null && !visitedBlocks.contains(nextBlock) ? nextBlock : null;
} while (block != null);
}
}
}
// TODO(mikaelpeltier) Manage that from and to instruction do not belong to the same block.
private static boolean hasLocalOrLineChangeBetween(
Instruction from, Instruction to, DexString localVar) {
if (from.getBlock() != to.getBlock()) {
return true;
}
if (from.getPosition().isSome()
&& to.getPosition().isSome()
&& !from.getPosition().equals(to.getPosition())) {
return true;
}
InstructionListIterator iterator = from.getBlock().listIterator(from);
Position position = null;
while (iterator.hasNext()) {
Instruction instruction = iterator.next();
if (position == null) {
if (instruction.getPosition().isSome()) {
position = instruction.getPosition();
}
} else if (instruction.getPosition().isSome()
&& !position.equals(instruction.getPosition())) {
return true;
}
if (instruction == to) {
return false;
}
if (instruction.outValue() != null && instruction.outValue().hasLocalInfo()) {
if (instruction.outValue().getLocalInfo().name == localVar) {
return true;
}
}
}
throw new Unreachable();
}
public void simplifyDebugLocals(IRCode code) {
for (BasicBlock block : code.blocks) {
for (Phi phi : block.getPhis()) {
if (!phi.hasLocalInfo() && phi.numberOfUsers() == 1 && phi.numberOfAllUsers() == 1) {
Instruction instruction = phi.uniqueUsers().iterator().next();
if (instruction.isDebugLocalWrite()) {
removeDebugWriteOfPhi(phi, instruction.asDebugLocalWrite());
}
}
}
InstructionListIterator iterator = block.listIterator();
while (iterator.hasNext()) {
Instruction prevInstruction = iterator.peekPrevious();
Instruction instruction = iterator.next();
if (instruction.isDebugLocalWrite()) {
assert instruction.inValues().size() == 1;
Value inValue = instruction.inValues().get(0);
DebugLocalInfo localInfo = instruction.outValue().getLocalInfo();
DexString localName = localInfo.name;
if (!inValue.hasLocalInfo() &&
inValue.numberOfAllUsers() == 1 &&
inValue.definition != null &&
!hasLocalOrLineChangeBetween(inValue.definition, instruction, localName)) {
inValue.setLocalInfo(localInfo);
instruction.outValue().replaceUsers(inValue);
Value overwrittenLocal = instruction.removeDebugValue(localInfo);
if (overwrittenLocal != null) {
inValue.definition.addDebugValue(overwrittenLocal);
}
if (prevInstruction != null) {
instruction.moveDebugValues(prevInstruction);
}
iterator.removeOrReplaceByDebugLocalRead();
}
}
}
}
}
private void removeDebugWriteOfPhi(Phi phi, DebugLocalWrite write) {
assert write.src() == phi;
for (InstructionListIterator iterator = phi.getBlock().listIterator(); iterator.hasNext(); ) {
Instruction next = iterator.next();
if (!next.isDebugLocalWrite()) {
// If the debug write is not in the block header bail out.
return;
}
if (next == write) {
// Associate the phi with the local.
phi.setLocalInfo(write.getLocalInfo());
// Replace uses of the write with the phi.
write.outValue().replaceUsers(phi);
// Safely remove the write.
// TODO(zerny): Once phis become instructions, move debug values there instead of a nop.
iterator.removeOrReplaceByDebugLocalRead();
return;
}
assert next.getLocalInfo().name != write.getLocalInfo().name;
}
}
private static class CSEExpressionEquivalence extends Equivalence<Instruction> {
private final IRCode code;
private CSEExpressionEquivalence(IRCode code) {
this.code = code;
}
@Override
protected boolean doEquivalent(Instruction a, Instruction b) {
// Some Dalvik VMs incorrectly handle Cmp instructions which leads to a requirement
// that we do not perform common subexpression elimination for them. See comment on
// canHaveCmpLongBug for details.
if (a.isCmp() && code.options.canHaveCmpLongBug()) {
return false;
}
// Note that we don't consider positions because CSE can at most remove an instruction.
if (!a.identicalNonValueNonPositionParts(b)) {
return false;
}
// For commutative binary operations any order of in-values are equal.
if (a.isBinop() && a.asBinop().isCommutative()) {
Value a0 = a.inValues().get(0);
Value a1 = a.inValues().get(1);
Value b0 = b.inValues().get(0);
Value b1 = b.inValues().get(1);
return (identicalValue(a0, b0) && identicalValue(a1, b1))
|| (identicalValue(a0, b1) && identicalValue(a1, b0));
} else {
// Compare all in-values.
assert a.inValues().size() == b.inValues().size();
for (int i = 0; i < a.inValues().size(); i++) {
if (!identicalValue(a.inValues().get(i), b.inValues().get(i))) {
return false;
}
}
return true;
}
}
@Override
protected int doHash(Instruction instruction) {
final int prime = 29;
int hash = instruction.getClass().hashCode();
if (instruction.isBinop()) {
Binop binop = instruction.asBinop();
Value in0 = instruction.inValues().get(0);
Value in1 = instruction.inValues().get(1);
if (binop.isCommutative()) {
hash += hash * prime + getHashCode(in0) * getHashCode(in1);
} else {
hash += hash * prime + getHashCode(in0);
hash += hash * prime + getHashCode(in1);
}
return hash;
} else {
for (Value value : instruction.inValues()) {
hash += hash * prime + getHashCode(value);
}
}
return hash;
}
private static boolean identicalValue(Value a, Value b) {
if (a.equals(b)) {
return true;
}
if (a.isConstNumber() && b.isConstNumber()) {
// Do not take assumption that constants are canonicalized.
return a.definition.identicalNonValueNonPositionParts(b.definition);
}
return false;
}
private static int getHashCode(Value a) {
if (a.isConstNumber()) {
// Do not take assumption that constants are canonicalized.
return Long.hashCode(a.definition.asConstNumber().getRawValue());
}
return a.hashCode();
}
}
private boolean shareCatchHandlers(Instruction i0, Instruction i1) {
if (!i0.instructionTypeCanThrow()) {
assert !i1.instructionTypeCanThrow();
return true;
}
assert i1.instructionTypeCanThrow();
// TODO(sgjesse): This could be even better by checking for the exceptions thrown, e.g. div
// and rem only ever throw ArithmeticException.
CatchHandlers<BasicBlock> ch0 = i0.getBlock().getCatchHandlers();
CatchHandlers<BasicBlock> ch1 = i1.getBlock().getCatchHandlers();
return ch0.equals(ch1);
}
private boolean isCSEInstructionCandidate(Instruction instruction) {
return (instruction.isBinop()
|| instruction.isUnop()
|| instruction.isInstanceOf()
|| instruction.isCheckCast())
&& instruction.getLocalInfo() == null
&& !instruction.hasInValueWithLocalInfo();
}
private boolean hasCSECandidate(IRCode code, int noCandidate) {
for (BasicBlock block : code.blocks) {
InstructionListIterator iterator = block.listIterator();
while (iterator.hasNext()) {
if (isCSEInstructionCandidate(iterator.next())) {
return true;
}
}
block.mark(noCandidate);
}
return false;
}
public void commonSubexpressionElimination(IRCode code) {
int noCandidate = code.reserveMarkingColor();
if (hasCSECandidate(code, noCandidate)) {
final ListMultimap<Wrapper<Instruction>, Value> instructionToValue =
ArrayListMultimap.create();
final CSEExpressionEquivalence equivalence = new CSEExpressionEquivalence(code);
final DominatorTree dominatorTree = new DominatorTree(code);
for (int i = 0; i < dominatorTree.getSortedBlocks().length; i++) {
BasicBlock block = dominatorTree.getSortedBlocks()[i];
if (block.isMarked(noCandidate)) {
continue;
}
InstructionListIterator iterator = block.listIterator();
while (iterator.hasNext()) {
Instruction instruction = iterator.next();
if (isCSEInstructionCandidate(instruction)) {
List<Value> candidates = instructionToValue.get(equivalence.wrap(instruction));
boolean eliminated = false;
if (candidates.size() > 0) {
for (Value candidate : candidates) {
if (dominatorTree.dominatedBy(block, candidate.definition.getBlock())
&& shareCatchHandlers(instruction, candidate.definition)) {
instruction.outValue().replaceUsers(candidate);
eliminated = true;
iterator.removeOrReplaceByDebugLocalRead();
break; // Don't try any more candidates.
}
}
}
if (!eliminated) {
instructionToValue.put(equivalence.wrap(instruction), instruction.outValue());
}
}
}
}
}
code.returnMarkingColor(noCandidate);
assert code.isConsistentSSA();
}
public void simplifyIf(IRCode code, TypeEnvironment typeEnvironment) {
for (BasicBlock block : code.blocks) {
// Skip removed (= unreachable) blocks.
if (block.getNumber() != 0 && block.getPredecessors().isEmpty()) {
continue;
}
if (block.exit().isIf()) {
flipIfBranchesIfNeeded(block);
rewriteIfWithConstZero(block);
if (simplifyKnownBooleanCondition(code, block)) {
continue;
}
// Simplify if conditions when possible.
If theIf = block.exit().asIf();
List<Value> inValues = theIf.inValues();
if (inValues.get(0).isConstNumber()
&& (theIf.isZeroTest() || inValues.get(1).isConstNumber())) {
// Zero test with a constant of comparison between between two constants.
if (theIf.isZeroTest()) {
ConstNumber cond = inValues.get(0).getConstInstruction().asConstNumber();
BasicBlock target = theIf.targetFromCondition(cond);
simplifyIfWithKnownCondition(code, block, theIf, target);
} else {
ConstNumber left = inValues.get(0).getConstInstruction().asConstNumber();
ConstNumber right = inValues.get(1).getConstInstruction().asConstNumber();
BasicBlock target = theIf.targetFromCondition(left, right);
simplifyIfWithKnownCondition(code, block, theIf, target);
}
} else if (inValues.get(0).hasValueRange()
&& (theIf.isZeroTest() || inValues.get(1).hasValueRange())) {
// Zero test with a value range, or comparison between between two values,
// each with a value ranges.
if (theIf.isZeroTest()) {
if (!inValues.get(0).isValueInRange(0)) {
int cond = Long.signum(inValues.get(0).getValueRange().getMin());
simplifyIfWithKnownCondition(code, block, theIf, cond);
}
} else {
LongInterval leftRange = inValues.get(0).getValueRange();
LongInterval rightRange = inValues.get(1).getValueRange();
if (!leftRange.overlapsWith(rightRange)) {
int cond = Long.signum(leftRange.getMin() - rightRange.getMin());
simplifyIfWithKnownCondition(code, block, theIf, cond);
}
}
} else if (theIf.isZeroTest() && !inValues.get(0).isConstNumber()
&& (theIf.getType() == Type.EQ || theIf.getType() == Type.NE)) {
if (inValues.get(0).isNeverNull()) {
simplifyIfWithKnownCondition(code, block, theIf, 1);
} else {
// TODO(b/72693244): annotate type lattice to value
TypeLatticeElement l = typeEnvironment.getLatticeElement(inValues.get(0));
if (!l.isPrimitive() && !l.isNullable()) {
simplifyIfWithKnownCondition(code, block, theIf, 1);
}
}
}
}
}
code.removeUnreachableBlocks();
assert code.isConsistentSSA();
}
private void simplifyIfWithKnownCondition(
IRCode code, BasicBlock block, If theIf, BasicBlock target) {
BasicBlock deadTarget =
target == theIf.getTrueTarget() ? theIf.fallthroughBlock() : theIf.getTrueTarget();
rewriteIfToGoto(code, block, theIf, target, deadTarget);
}
private void simplifyIfWithKnownCondition(IRCode code, BasicBlock block, If theIf, int cond) {
simplifyIfWithKnownCondition(code, block, theIf, theIf.targetFromCondition(cond));
}
// Find all method invocations that never returns normally, split the block
// after each such invoke instruction and follow it with a block throwing a
// null value (which should result in NPE). Note that this throw is not
// expected to be ever reached, but is intended to satisfy verifier.
public void processMethodsNeverReturningNormally(IRCode code) {
AppInfoWithLiveness appInfoWithLiveness = appInfo.withLiveness();
if (appInfoWithLiveness == null) {
return;
}
ListIterator<BasicBlock> blockIterator = code.listIterator();
while (blockIterator.hasNext()) {
BasicBlock block = blockIterator.next();
if (block.getNumber() != 0 && block.getPredecessors().isEmpty()) {
continue;
}
InstructionListIterator insnIterator = block.listIterator();
while (insnIterator.hasNext()) {
Instruction insn = insnIterator.next();
if (!insn.isInvokeMethod()) {
continue;
}
DexEncodedMethod singleTarget =
insn.asInvokeMethod().computeSingleTarget(appInfoWithLiveness);
if (singleTarget == null || !singleTarget.getOptimizationInfo().neverReturnsNormally()) {
continue;
}
// Split the block.
{
BasicBlock newBlock = insnIterator.split(code, blockIterator);
assert !insnIterator.hasNext(); // must be pointing *after* inserted GoTo.
// Move block iterator back so current block is 'newBlock'.
blockIterator.previous();
newBlock.unlinkSinglePredecessorSiblingsAllowed();
}
// We want to follow the invoke instruction with 'throw null', which should
// be unreachable but is needed to satisfy the verifier. Note that we have
// to put 'throw null' into a separate block to make sure we don't get two
// throwing instructions in the block having catch handler. This new block
// does not need catch handlers.
Instruction gotoInsn = insnIterator.previous();
assert gotoInsn.isGoto();
assert insnIterator.hasNext();
BasicBlock throwNullBlock = insnIterator.split(code, blockIterator);
InstructionListIterator throwNullInsnIterator = throwNullBlock.listIterator();
// Insert 'null' constant.
Value nullValue = code.createValue(ValueType.OBJECT, gotoInsn.getLocalInfo());
ConstNumber nullConstant = new ConstNumber(nullValue, 0);
nullConstant.setPosition(insn.getPosition());
throwNullInsnIterator.add(nullConstant);
// Replace Goto with Throw.
Throw notReachableThrow = new Throw(nullValue);
Instruction insnGoto = throwNullInsnIterator.next();
assert insnGoto.isGoto();
throwNullInsnIterator.replaceCurrentInstruction(notReachableThrow);
// Use position from original invoke to guarantee it has a real position.
notReachableThrow.forceSetPosition(insn.getPosition());
}
}
code.removeUnreachableBlocks();
assert code.isConsistentSSA();
}
/* Identify simple diamond shapes converting boolean true/false to 1/0. We consider the forms:
*
* (1)
*
* [dbg pos x] [dbg pos x]
* ifeqz booleanValue ifnez booleanValue
* / \ / \
* [dbg pos x][dbg pos x] [dbg pos x][dbg pos x]
* [const 0] [const 1] [const 1] [const 0]
* goto goto goto goto
* \ / \ /
* phi(0, 1) phi(1, 0)
*
* which can be replaced by a fallthrough and the phi value can be replaced
* with the boolean value itself.
*
* (2)
*
* [dbg pos x] [dbg pos x]
* ifeqz booleanValue ifnez booleanValue
* / \ / \
* [dbg pos x][dbg pos x] [dbg pos x][dbg pos x]
* [const 1] [const 0] [const 0] [const 1]
* goto goto goto goto
* \ / \ /
* phi(1, 0) phi(0, 1)
*
* which can be replaced by a fallthrough and the phi value can be replaced
* by an xor instruction which is smaller.
*/
private boolean simplifyKnownBooleanCondition(IRCode code, BasicBlock block) {
If theIf = block.exit().asIf();
Value testValue = theIf.inValues().get(0);
if (theIf.isZeroTest() && testValue.knownToBeBoolean()) {
BasicBlock trueBlock = theIf.getTrueTarget();
BasicBlock falseBlock = theIf.fallthroughBlock();
if (isBlockSupportedBySimplifyKnownBooleanCondition(trueBlock) &&
isBlockSupportedBySimplifyKnownBooleanCondition(falseBlock) &&
trueBlock.getSuccessors().get(0) == falseBlock.getSuccessors().get(0)) {
BasicBlock targetBlock = trueBlock.getSuccessors().get(0);
if (targetBlock.getPredecessors().size() == 2) {
int trueIndex = targetBlock.getPredecessors().indexOf(trueBlock);
int falseIndex = trueIndex == 0 ? 1 : 0;
int deadPhis = 0;
// Locate the phis that have the same value as the boolean and replace them
// by the boolean in all users.
for (Phi phi : targetBlock.getPhis()) {
Value trueValue = phi.getOperand(trueIndex);
Value falseValue = phi.getOperand(falseIndex);
if (trueValue.isConstNumber() && falseValue.isConstNumber()) {
ConstNumber trueNumber = trueValue.getConstInstruction().asConstNumber();
ConstNumber falseNumber = falseValue.getConstInstruction().asConstNumber();
if ((theIf.getType() == Type.EQ &&
trueNumber.isIntegerZero() &&
falseNumber.isIntegerOne()) ||
(theIf.getType() == Type.NE &&
trueNumber.isIntegerOne() &&
falseNumber.isIntegerZero())) {
phi.replaceUsers(testValue);
deadPhis++;
} else if ((theIf.getType() == Type.NE &&
trueNumber.isIntegerZero() &&
falseNumber.isIntegerOne()) ||
(theIf.getType() == Type.EQ &&
trueNumber.isIntegerOne() &&
falseNumber.isIntegerZero())) {
Value newOutValue = code.createValue(phi.outType(), phi.getLocalInfo());
ConstNumber cstToUse = trueNumber.isIntegerOne() ? trueNumber : falseNumber;
BasicBlock phiBlock = phi.getBlock();
Position phiPosition = phiBlock.getPosition();
int insertIndex = 0;
if (cstToUse.getBlock() == trueBlock || cstToUse.getBlock() == falseBlock) {
// The constant belongs to the block to remove, create a new one.
cstToUse = ConstNumber.copyOf(code, cstToUse);
cstToUse.setBlock(phiBlock);
cstToUse.setPosition(phiPosition);
phiBlock.getInstructions().add(insertIndex++, cstToUse);
}
phi.replaceUsers(newOutValue);
Instruction newInstruction = new Xor(NumericType.INT, newOutValue, testValue,
cstToUse.outValue());
newInstruction.setBlock(phiBlock);
// The xor is replacing a phi so it does not have an actual position.
newInstruction.setPosition(phiPosition);
phiBlock.getInstructions().add(insertIndex, newInstruction);
deadPhis++;
}
}
}
// If all phis were removed, there is no need for the diamond shape anymore
// and it can be rewritten to a goto to one of the branches.
if (deadPhis == targetBlock.getPhis().size()) {
rewriteIfToGoto(code, block, theIf, trueBlock, falseBlock);
return true;
}
}
}
}
return false;
}
private boolean isBlockSupportedBySimplifyKnownBooleanCondition(BasicBlock b) {
if (b.isTrivialGoto()) {
return true;
}
int instructionSize = b.getInstructions().size();
if (b.exit().isGoto() && (instructionSize == 2 || instructionSize == 3)) {
Instruction constInstruction = b.getInstructions().get(instructionSize - 2);
if (constInstruction.isConstNumber()) {
if (!constInstruction.asConstNumber().isIntegerOne() &&
!constInstruction.asConstNumber().isIntegerZero()) {
return false;
}
if (instructionSize == 2) {
return true;
}
Instruction firstInstruction = b.getInstructions().getFirst();
if (firstInstruction.isDebugPosition()) {
assert b.getPredecessors().size() == 1;
BasicBlock predecessorBlock = b.getPredecessors().get(0);
InstructionListIterator it = predecessorBlock.listIterator(predecessorBlock.exit());
Instruction previousPosition = null;
while (it.hasPrevious() && !(previousPosition = it.previous()).isDebugPosition());
if (previousPosition != null) {
return previousPosition.getPosition() == firstInstruction.getPosition();
}
}
}
}
return false;
}
private void rewriteIfToGoto(
IRCode code, BasicBlock block, If theIf, BasicBlock target, BasicBlock deadTarget) {
deadTarget.unlinkSinglePredecessorSiblingsAllowed();
assert theIf == block.exit();
block.replaceLastInstruction(new Goto());
assert block.exit().isGoto();
assert block.exit().asGoto().getTarget() == target;
}
private void rewriteIfWithConstZero(BasicBlock block) {
If theIf = block.exit().asIf();
if (theIf.isZeroTest()) {
return;
}
List<Value> inValues = theIf.inValues();
Value leftValue = inValues.get(0);
Value rightValue = inValues.get(1);
if (leftValue.isConstNumber() || rightValue.isConstNumber()) {
if (leftValue.isConstNumber()) {
if (leftValue.getConstInstruction().asConstNumber().isZero()) {
If ifz = new If(theIf.getType().forSwappedOperands(), rightValue);
block.replaceLastInstruction(ifz);
assert block.exit() == ifz;
}
} else {
if (rightValue.getConstInstruction().asConstNumber().isZero()) {
If ifz = new If(theIf.getType(), leftValue);
block.replaceLastInstruction(ifz);
assert block.exit() == ifz;
}
}
}
}
private boolean flipIfBranchesIfNeeded(BasicBlock block) {
If theIf = block.exit().asIf();
BasicBlock trueTarget = theIf.getTrueTarget();
BasicBlock fallthrough = theIf.fallthroughBlock();
assert trueTarget != fallthrough;
if (!fallthrough.isSimpleAlwaysThrowingPath() || trueTarget.isSimpleAlwaysThrowingPath()) {
return false;
}
// In case fall-through block always throws there is a good chance that it
// is created for error checks and 'trueTarget' represents most more common
// non-error case. Flipping the if in this case may result in faster code
// on older Android versions.
List<Value> inValues = theIf.inValues();
If newIf = new If(theIf.getType().inverted(), inValues);
block.replaceLastInstruction(newIf);
block.swapSuccessors(trueTarget, fallthrough);
return true;
}
public void rewriteLongCompareAndRequireNonNull(IRCode code, InternalOptions options) {
if (options.canUseLongCompareAndObjectsNonNull()) {
return;
}
InstructionIterator iterator = code.instructionIterator();
while (iterator.hasNext()) {
Instruction current = iterator.next();
if (current.isInvokeMethod()) {
DexMethod invokedMethod = current.asInvokeMethod().getInvokedMethod();
if (invokedMethod == dexItemFactory.longMethods.compare) {
// Rewrite calls to Long.compare for sdk versions that do not have that method.
List<Value> inValues = current.inValues();
assert inValues.size() == 2;
iterator.replaceCurrentInstruction(
new Cmp(NumericType.LONG, Bias.NONE, current.outValue(), inValues.get(0),
inValues.get(1)));
} else if (invokedMethod == dexItemFactory.objectsMethods.requireNonNull) {
// Rewrite calls to Objects.requireNonNull(Object) because Javac 9 start to use it for
// synthesized null checks.
InvokeVirtual callToGetClass = new InvokeVirtual(dexItemFactory.objectMethods.getClass,
null, current.inValues());
if (current.outValue() != null) {
current.outValue().replaceUsers(current.inValues().get(0));
current.setOutValue(null);
}
iterator.replaceCurrentInstruction(callToGetClass);
}
}
}
assert code.isConsistentSSA();
}
// Removes calls to Throwable.addSuppressed(Throwable) and rewrites
// Throwable.getSuppressed() into new Throwable[0].
//
// Note that addSuppressed() and getSuppressed() methods are final in
// Throwable, so these changes don't have to worry about overrides.
public void rewriteThrowableAddAndGetSuppressed(IRCode code) {
DexItemFactory.ThrowableMethods throwableMethods = dexItemFactory.throwableMethods;
for (BasicBlock block : code.blocks) {
InstructionListIterator iterator = block.listIterator();
while (iterator.hasNext()) {
Instruction current = iterator.next();
if (current.isInvokeMethod()) {
DexMethod invokedMethod = current.asInvokeMethod().getInvokedMethod();
if (matchesMethodOfThrowable(invokedMethod, throwableMethods.addSuppressed)) {
// Remove Throwable::addSuppressed(Throwable) call.
iterator.removeOrReplaceByDebugLocalRead();
} else if (matchesMethodOfThrowable(invokedMethod, throwableMethods.getSuppressed)) {
Value destValue = current.outValue();
if (destValue == null) {
// If the result of the call was not used we don't create
// an empty array and just remove the call.
iterator.removeOrReplaceByDebugLocalRead();
continue;
}
// Replace call to Throwable::getSuppressed() with new Throwable[0].
// First insert the constant value *before* the current instruction.
ConstNumber zero = code.createIntConstant(0);
zero.setPosition(current.getPosition());
assert iterator.hasPrevious();
iterator.previous();
iterator.add(zero);
// Then replace the invoke instruction with new-array instruction.
Instruction next = iterator.next();
assert current == next;
NewArrayEmpty newArray = new NewArrayEmpty(destValue, zero.outValue(),
dexItemFactory.createType(dexItemFactory.throwableArrayDescriptor));
iterator.replaceCurrentInstruction(newArray);
}
}
}
}
assert code.isConsistentSSA();
}
private boolean matchesMethodOfThrowable(DexMethod invoked, DexMethod expected) {
return invoked.name == expected.name
&& invoked.proto == expected.proto
&& isSubtypeOfThrowable(invoked.holder);
}
private boolean isSubtypeOfThrowable(DexType type) {
while (type != null && type != dexItemFactory.objectType) {
if (type == dexItemFactory.throwableType) {
return true;
}
DexClass dexClass = definitionFor(type);
if (dexClass == null) {
throw new CompilationError("Class or interface " + type.toSourceString() +
" required for desugaring of try-with-resources is not found.");
}
type = dexClass.superType;
}
return false;
}
private Value addConstString(IRCode code, InstructionListIterator iterator, String s) {
Value value = code.createValue(ValueType.OBJECT);
iterator.add(new ConstString(value, dexItemFactory.createString(s)));
return value;
}
/**
* Insert code into <code>method</code> to log the argument types to System.out.
*
* The type is determined by calling getClass() on the argument.
*/
public void logArgumentTypes(DexEncodedMethod method, IRCode code) {
List<Value> arguments = code.collectArguments();
BasicBlock block = code.blocks.getFirst();
InstructionListIterator iterator = block.listIterator();
// Attach some synthetic position to all inserted code.
Position position = Position.synthetic(1, method.method, null);
iterator.setInsertionPosition(position);
// Split arguments into their own block.
iterator.nextUntil(instruction -> !instruction.isArgument());
iterator.previous();
iterator.split(code);
iterator.previous();
// Now that the block is split there should not be any catch handlers in the block.
assert !block.hasCatchHandlers();
Value out = code.createValue(ValueType.OBJECT);
DexType javaLangSystemType = dexItemFactory.createType("Ljava/lang/System;");
DexType javaIoPrintStreamType = dexItemFactory.createType("Ljava/io/PrintStream;");
DexProto proto = dexItemFactory.createProto(dexItemFactory.voidType, dexItemFactory.objectType);
DexMethod print = dexItemFactory.createMethod(javaIoPrintStreamType, proto, "print");
DexMethod printLn = dexItemFactory.createMethod(javaIoPrintStreamType, proto, "println");
iterator.add(
new StaticGet(MemberType.OBJECT, out,
dexItemFactory.createField(javaLangSystemType, javaIoPrintStreamType, "out")));
Value value = code.createValue(ValueType.OBJECT);
iterator.add(new ConstString(value, dexItemFactory.createString("INVOKE ")));
iterator.add(new InvokeVirtual(print, null, ImmutableList.of(out, value)));
value = code.createValue(ValueType.OBJECT);
iterator.add(
new ConstString(value, dexItemFactory.createString(method.method.qualifiedName())));
iterator.add(new InvokeVirtual(print, null, ImmutableList.of(out, value)));
Value openParenthesis = addConstString(code, iterator, "(");
Value comma = addConstString(code, iterator, ",");
Value closeParenthesis = addConstString(code, iterator, ")");
Value indent = addConstString(code, iterator, " ");
Value nul = addConstString(code, iterator, "(null)");
Value primitive = addConstString(code, iterator, "(primitive)");
Value empty = addConstString(code, iterator, "");
iterator.add(new InvokeVirtual(printLn, null, ImmutableList.of(out, openParenthesis)));
for (int i = 0; i < arguments.size(); i++) {
iterator.add(new InvokeVirtual(print, null, ImmutableList.of(out, indent)));
// Add a block for end-of-line printing.
BasicBlock eol = BasicBlock.createGotoBlock(code.blocks.size());
code.blocks.add(eol);
BasicBlock successor = block.unlinkSingleSuccessor();
block.link(eol);
eol.link(successor);
Value argument = arguments.get(i);
if (argument.outType() != ValueType.OBJECT) {
iterator.add(new InvokeVirtual(print, null, ImmutableList.of(out, primitive)));
} else {
// Insert "if (argument != null) ...".
successor = block.unlinkSingleSuccessor();
If theIf = new If(If.Type.NE, argument);
theIf.setPosition(position);
BasicBlock ifBlock = BasicBlock.createIfBlock(code.blocks.size(), theIf);
code.blocks.add(ifBlock);
// Fallthrough block must be added right after the if.
BasicBlock isNullBlock = BasicBlock.createGotoBlock(code.blocks.size());
code.blocks.add(isNullBlock);
BasicBlock isNotNullBlock = BasicBlock.createGotoBlock(code.blocks.size());
code.blocks.add(isNotNullBlock);
// Link the added blocks together.
block.link(ifBlock);
ifBlock.link(isNotNullBlock);
ifBlock.link(isNullBlock);
isNotNullBlock.link(successor);
isNullBlock.link(successor);
// Fill code into the blocks.
iterator = isNullBlock.listIterator();
iterator.setInsertionPosition(position);
iterator.add(new InvokeVirtual(print, null, ImmutableList.of(out, nul)));
iterator = isNotNullBlock.listIterator();
iterator.setInsertionPosition(position);
value = code.createValue(ValueType.OBJECT);
iterator.add(new InvokeVirtual(dexItemFactory.objectMethods.getClass, value,
ImmutableList.of(arguments.get(i))));
iterator.add(new InvokeVirtual(print, null, ImmutableList.of(out, value)));
}
iterator = eol.listIterator();
iterator.setInsertionPosition(position);
if (i == arguments.size() - 1) {
iterator.add(new InvokeVirtual(printLn, null, ImmutableList.of(out, closeParenthesis)));
} else {
iterator.add(new InvokeVirtual(printLn, null, ImmutableList.of(out, comma)));
}
block = eol;
}
// When we fall out of the loop the iterator is in the last eol block.
iterator.add(new InvokeVirtual(printLn, null, ImmutableList.of(out, empty)));
}
public static void ensureDirectStringNewToInit(IRCode code) {
DexItemFactory factory = code.options.itemFactory;
for (BasicBlock block : code.blocks) {
for (InstructionListIterator it = block.listIterator(); it.hasNext(); ) {
Instruction instruction = it.next();
if (instruction.isInvokeDirect()) {
InvokeDirect invoke = instruction.asInvokeDirect();
DexMethod method = invoke.getInvokedMethod();
if (factory.isConstructor(method)
&& method.holder == factory.stringType
&& invoke.getReceiver().isPhi()) {
NewInstance newInstance = findNewInstance(invoke.getReceiver().asPhi());
replaceTrivialNewInstancePhis(newInstance.outValue());
if (invoke.getReceiver().isPhi()) {
throw new CompilationError(
"Failed to remove trivial phis between new-instance and <init>");
}
newInstance.markNoSpilling();
}
}
}
}
}
private static NewInstance findNewInstance(Phi phi) {
Set<Phi> seen = new HashSet<>();
Set<Value> values = new HashSet<>();
recursiveAddOperands(phi, seen, values);
if (values.size() != 1) {
throw new CompilationError("Failed to identify unique new-instance for <init>");
}
Value newInstanceValue = values.iterator().next();
if (newInstanceValue.definition == null || !newInstanceValue.definition.isNewInstance()) {
throw new CompilationError("Invalid defining value for call to <init>");
}
return newInstanceValue.definition.asNewInstance();
}
private static void recursiveAddOperands(Phi phi, Set<Phi> seen, Set<Value> values) {
for (Value operand : phi.getOperands()) {
if (!operand.isPhi()) {
values.add(operand);
} else {
Phi phiOp = operand.asPhi();
if (seen.add(phiOp)) {
recursiveAddOperands(phiOp, seen, values);
}
}
}
}
// If an <init> call takes place on a phi the code must contain an irreducible loop between the
// new-instance and the <init>. Assuming the code is verifiable, new-instance must flow to a
// unique <init>. Here we compute the set of strongly connected phis making use of the
// new-instance value and replace all trivial ones by the new-instance value.
// This is a simplified variant of the removeRedundantPhis algorithm in Section 3.2 of:
// http://compilers.cs.uni-saarland.de/papers/bbhlmz13cc.pdf
private static void replaceTrivialNewInstancePhis(Value newInstanceValue) {
List<Set<Value>> components = new SCC().computeSCC(newInstanceValue);
for (int i = components.size() - 1; i >= 0; i--) {
Set<Value> component = components.get(i);
if (component.size() == 1 && component.iterator().next() == newInstanceValue) {
continue;
}
Set<Phi> trivialPhis = new HashSet<>();
for (Value value : component) {
boolean isTrivial = true;
Phi p = value.asPhi();
for (Value op : p.getOperands()) {
if (op != newInstanceValue && !component.contains(op)) {
isTrivial = false;
break;
}
}
if (isTrivial) {
trivialPhis.add(p);
}
}
for (Phi trivialPhi : trivialPhis) {
for (Value op : trivialPhi.getOperands()) {
op.removePhiUser(trivialPhi);
}
trivialPhi.replaceUsers(newInstanceValue);
trivialPhi.getBlock().removePhi(trivialPhi);
}
}
}
// Dijkstra's path-based strongly-connected components algorithm.
// https://en.wikipedia.org/wiki/Path-based_strong_component_algorithm
private static class SCC {
private int currentTime = 0;
private final Reference2IntMap<Value> discoverTime = new Reference2IntOpenHashMap<>();
private final Set<Value> unassignedSet = new HashSet<>();
private final Deque<Value> unassignedStack = new ArrayDeque<>();
private final Deque<Value> preorderStack = new ArrayDeque<>();
private final List<Set<Value>> components = new ArrayList<>();
public List<Set<Value>> computeSCC(Value v) {
assert currentTime == 0;
dfs(v);
return components;
}
private void dfs(Value value) {
discoverTime.put(value, currentTime++);
unassignedSet.add(value);
unassignedStack.push(value);
preorderStack.push(value);
for (Phi phi : value.uniquePhiUsers()) {
if (!discoverTime.containsKey(phi)) {
// If not seen yet, continue the search.
dfs(phi);
} else if (unassignedSet.contains(phi)) {
// If seen already and the element is on the unassigned stack we have found a cycle.
// Pop off everything discovered later than the target from the preorder stack. This may
// not coincide with the cycle as an outer cycle may already have popped elements off.
int discoverTimeOfPhi = discoverTime.getInt(phi);
while (discoverTimeOfPhi < discoverTime.getInt(preorderStack.peek())) {
preorderStack.pop();
}
}
}
if (preorderStack.peek() == value) {
// If the current element is the top of the preorder stack, then we are at entry to a
// strongly-connected component consisting of this element and every element above this
// element on the stack.
Set<Value> component = new HashSet<>(unassignedStack.size());
while (true) {
Value member = unassignedStack.pop();
unassignedSet.remove(member);
component.add(member);
if (member == value) {
components.add(component);
break;
}
}
preorderStack.pop();
}
}
}
// See comment for InternalOptions.canHaveNumberConversionRegisterAllocationBug().
public void workaroundNumberConversionRegisterAllocationBug(IRCode code) {
final Supplier<DexMethod> javaLangDoubleisNaN = Suppliers.memoize(() ->
dexItemFactory.createMethod(
dexItemFactory.createString("Ljava/lang/Double;"),
dexItemFactory.createString("isNaN"),
dexItemFactory.booleanDescriptor,
new DexString[]{dexItemFactory.doubleDescriptor}));
ListIterator<BasicBlock> blocks = code.listIterator();
while (blocks.hasNext()) {
BasicBlock block = blocks.next();
InstructionListIterator it = block.listIterator();
while (it.hasNext()) {
Instruction instruction = it.next();
if (instruction.isArithmeticBinop() || instruction.isNeg()) {
for (Value value : instruction.inValues()) {
// Insert a call to Double.isNaN on each value which come from a number conversion
// to double and flows into an arithmetic instruction. This seems to break the traces
// in the Dalvik JIT and avoid the bug where the generated ARM code can clobber float
// values in a single-precision registers with double values written to
// double-precision registers. See b/77496850 for examples.
if (!value.isPhi()
&& value.definition.isNumberConversion()
&& value.definition.asNumberConversion().to == NumericType.DOUBLE) {
InvokeStatic invokeIsNaN =
new InvokeStatic(javaLangDoubleisNaN.get(), null, ImmutableList.of(value));
invokeIsNaN.setPosition(instruction.getPosition());
// Insert the invoke before the current instruction.
it.previous();
BasicBlock blockWithInvokeNaN =
block.hasCatchHandlers() ? it.split(code, blocks) : block;
if (blockWithInvokeNaN != block) {
// If we split, add the invoke at the end of the original block.
it = block.listIterator(block.getInstructions().size());
it.previous();
it.add(invokeIsNaN);
// Continue iteration in the split block.
block = blockWithInvokeNaN;
it = block.listIterator();
} else {
// Otherwise, add it to the current block.
it.add(invokeIsNaN);
}
// Skip over the instruction causing the invoke to be inserted.
Instruction temp = it.next();
assert temp == instruction;
}
}
}
}
}
}
}