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r8 / r8 / d06b1dc0c05aae4df04a3110840b2e9f023fc07d / . / 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 static com.android.tools.r8.ir.analysis.type.Nullability.definitelyNotNull;
import static com.android.tools.r8.ir.analysis.type.Nullability.maybeNull;
import static com.android.tools.r8.ir.optimize.ReflectionOptimizer.ClassNameComputationInfo.ClassNameComputationOption.CANONICAL_NAME;
import static com.android.tools.r8.ir.optimize.ReflectionOptimizer.ClassNameComputationInfo.ClassNameComputationOption.NAME;
import static com.android.tools.r8.ir.optimize.ReflectionOptimizer.ClassNameComputationInfo.ClassNameComputationOption.SIMPLE_NAME;
import static com.android.tools.r8.ir.optimize.ReflectionOptimizer.computeClassName;
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.AppView;
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.DexEncodedMethod.TrivialInitializer;
import com.android.tools.r8.graph.DexEncodedMethod.TrivialInitializer.TrivialClassInitializer;
import com.android.tools.r8.graph.DexEncodedMethod.TrivialInitializer.TrivialInstanceInitializer;
import com.android.tools.r8.graph.DexField;
import com.android.tools.r8.graph.DexItemFactory;
import com.android.tools.r8.graph.DexItemFactory.ThrowableMethods;
import com.android.tools.r8.graph.DexMethod;
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.DexItemBasedValueString;
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.graph.GraphLense;
import com.android.tools.r8.graph.ParameterUsagesInfo;
import com.android.tools.r8.graph.ParameterUsagesInfo.ParameterUsage;
import com.android.tools.r8.graph.ParameterUsagesInfo.ParameterUsageBuilder;
import com.android.tools.r8.ir.analysis.type.TypeAnalysis;
import com.android.tools.r8.ir.analysis.type.TypeLatticeElement;
import com.android.tools.r8.ir.code.AlwaysMaterializingNop;
import com.android.tools.r8.ir.code.ArrayPut;
import com.android.tools.r8.ir.code.BasicBlock;
import com.android.tools.r8.ir.code.BasicBlock.ThrowingInfo;
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.DebugLocalsChange;
import com.android.tools.r8.ir.code.DexItemBasedConstString;
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.InstanceOf;
import com.android.tools.r8.ir.code.InstancePut;
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.Move;
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.IRConverter;
import com.android.tools.r8.ir.conversion.OptimizationFeedback;
import com.android.tools.r8.ir.optimize.Inliner.ConstraintWithTarget;
import com.android.tools.r8.ir.optimize.ReflectionOptimizer.ClassNameComputationInfo;
import com.android.tools.r8.ir.optimize.SwitchUtils.EnumSwitchInfo;
import com.android.tools.r8.ir.regalloc.LinearScanRegisterAllocator;
import com.android.tools.r8.kotlin.Kotlin;
import com.android.tools.r8.shaking.Enqueuer.AppInfoWithLiveness;
import com.android.tools.r8.utils.InternalOptions;
import com.android.tools.r8.utils.InternalOutputMode;
import com.android.tools.r8.utils.LongInterval;
import com.android.tools.r8.utils.MethodSignatureEquivalence;
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.Int2IntOpenHashMap;
import it.unimi.dsi.fastutil.ints.Int2ObjectAVLTreeMap;
import it.unimi.dsi.fastutil.ints.Int2ObjectSortedMap;
import it.unimi.dsi.fastutil.ints.Int2ReferenceMap;
import it.unimi.dsi.fastutil.ints.Int2ReferenceMap.Entry;
import it.unimi.dsi.fastutil.ints.Int2ReferenceOpenHashMap;
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.IntOpenHashSet;
import it.unimi.dsi.fastutil.ints.IntSet;
import it.unimi.dsi.fastutil.longs.Long2ReferenceMap;
import it.unimi.dsi.fastutil.longs.Long2ReferenceOpenHashMap;
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.Collection;
import java.util.Comparator;
import java.util.Deque;
import java.util.HashMap;
import java.util.HashSet;
import java.util.IdentityHashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.ListIterator;
import java.util.Map;
import java.util.PriorityQueue;
import java.util.Set;
import java.util.function.BiFunction;
import java.util.function.Function;
import java.util.function.Predicate;
public class CodeRewriter {
private enum InstanceOfResult {
UNKNOWN,
TRUE,
FALSE
}
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 static final int SELF_RECURSION_LIMIT = 4;
public final IRConverter converter;
private final AppInfo appInfo;
private final AppView<? extends AppInfo> appView;
private final DexItemFactory dexItemFactory;
private final Set<DexMethod> libraryMethodsReturningReceiver;
private final InternalOptions options;
public CodeRewriter(
IRConverter converter,
Set<DexMethod> libraryMethodsReturningReceiver,
InternalOptions options) {
this.converter = converter;
this.appInfo = converter.appInfo;
this.appView = converter.appView;
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;
}
public static boolean isFallthroughBlock(BasicBlock block) {
for (BasicBlock pred : block.getPredecessors()) {
if (pred.exit().fallthroughBlock() == block) {
return true;
}
}
return false;
}
private static void collapseTrivialGoto(
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);
unlinkTrivialGotoBlock(block, target);
}
}
public static void unlinkTrivialGotoBlock(BasicBlock block, BasicBlock target) {
assert block.isTrivialGoto();
for (BasicBlock pred : block.getPredecessors()) {
pred.replaceSuccessor(block, target);
}
for (BasicBlock succ : block.getSuccessors()) {
succ.getMutablePredecessors().remove(block);
}
for (BasicBlock pred : block.getPredecessors()) {
if (!target.getPredecessors().contains(pred)) {
target.getMutablePredecessors().add(pred);
}
}
}
private static void collapseIfTrueTarget(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.getMutablePredecessors().remove(block);
if (!newTarget.getPredecessors().contains(block)) {
newTarget.getMutablePredecessors().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 collapseNonFallthroughSwitchTargets(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.getMutablePredecessors().remove(block);
if (!newTarget.getPredecessors().contains(block)) {
newTarget.getMutablePredecessors().add(block);
}
replacedBlocks.add(target);
}
}
}
}
// For method with many self-recursive calls, insert a try-catch to disable inlining.
// Marshmallow dex2oat aggressively inlines and eats up all the memory on devices.
public static void disableDex2OatInliningForSelfRecursiveMethods(
IRCode code, InternalOptions options, AppInfo appInfo) {
if (!options.canHaveDex2OatInliningIssue() || code.hasCatchHandlers()) {
// Catch handlers disables inlining, so if the method already has catch handlers
// there is nothing to do.
return;
}
InstructionIterator it = code.instructionIterator();
int selfRecursionFanOut = 0;
Instruction lastSelfRecursiveCall = null;
while (it.hasNext()) {
Instruction i = it.next();
if (i.isInvokeMethod() && i.asInvokeMethod().getInvokedMethod() == code.method.method) {
selfRecursionFanOut++;
lastSelfRecursiveCall = i;
}
}
if (selfRecursionFanOut > SELF_RECURSION_LIMIT) {
assert lastSelfRecursiveCall != null;
// Split out the last recursive call in its own block.
InstructionListIterator splitIterator =
lastSelfRecursiveCall.getBlock().listIterator(lastSelfRecursiveCall);
splitIterator.previous();
BasicBlock newBlock = splitIterator.split(code, 1);
// Generate rethrow block.
DexType guard = options.itemFactory.throwableType;
BasicBlock rethrowBlock = BasicBlock.createRethrowBlock(
code,
lastSelfRecursiveCall.getPosition(),
guard,
appInfo,
options);
code.blocks.add(rethrowBlock);
// Add catch handler to the block containing the last recursive call.
newBlock.addCatchHandler(rethrowBlock, guard);
}
}
// 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);
}
private static class Interval {
private final IntList keys = new IntArrayList();
public Interval(IntList... allKeys) {
assert allKeys.length > 0;
for (IntList keys : allKeys) {
assert keys.size() > 0;
this.keys.addAll(keys);
}
}
public int getMin() {
return keys.getInt(0);
}
public int getMax() {
return keys.getInt(keys.size() - 1);
}
public void addInterval(Interval other) {
assert getMax() < other.getMin();
keys.addAll(other.keys);
}
public long packedSavings(InternalOutputMode mode) {
long packedTargets = (long) getMax() - (long) getMin() + 1;
if (!Switch.canBePacked(mode, packedTargets)) {
return Long.MIN_VALUE + 1;
}
long sparseCost = Switch.baseSparseSize(mode) + Switch.sparsePayloadSize(mode, keys.size());
long packedCost = Switch.basePackedSize(mode) + Switch.packedPayloadSize(mode, packedTargets);
return sparseCost - packedCost;
}
public long estimatedSize(InternalOutputMode mode) {
return Switch.estimatedSize(mode, keys.toIntArray());
}
}
private Interval combineOrAddInterval(
List<Interval> intervals, Interval previous, Interval current) {
// As a first iteration, we only combine intervals if their packed size is less than their
// sparse counterpart. In CF we will have to add a load and a jump which add to the
// stack map table (1 is the size of a same entry).
InternalOutputMode mode = options.getInternalOutputMode();
int penalty = mode.isGeneratingClassFiles() ? 3 + 1 : 0;
if (previous == null) {
intervals.add(current);
return current;
}
Interval combined = new Interval(previous.keys, current.keys);
long packedSavings = combined.packedSavings(mode);
if (packedSavings <= 0
|| packedSavings < previous.estimatedSize(mode) + current.estimatedSize(mode) - penalty) {
intervals.add(current);
return current;
} else {
intervals.set(intervals.size() - 1, combined);
return combined;
}
}
private void tryAddToBiggestSavings(
Set<Interval> biggestPackedSet,
PriorityQueue<Interval> intervals,
Interval toAdd,
int maximumNumberOfSwitches) {
assert !biggestPackedSet.contains(toAdd);
long savings = toAdd.packedSavings(options.getInternalOutputMode());
if (savings <= 0) {
return;
}
if (intervals.size() < maximumNumberOfSwitches) {
intervals.add(toAdd);
biggestPackedSet.add(toAdd);
} else if (savings > intervals.peek().packedSavings(options.getInternalOutputMode())) {
intervals.add(toAdd);
biggestPackedSet.add(toAdd);
biggestPackedSet.remove(intervals.poll());
}
}
private int sizeForKeysWrittenAsIfs(ValueType type, Collection<Integer> keys) {
int ifsSize = If.estimatedSize(options.getInternalOutputMode()) * keys.size();
// In Cf we also require a load as well (and a stack map entry)
if (options.getInternalOutputMode().isGeneratingClassFiles()) {
ifsSize += keys.size() * (3 + 1);
}
for (int k : keys) {
if (k != 0) {
ifsSize += ConstNumber.estimatedSize(options.getInternalOutputMode(), type, k);
}
}
return ifsSize;
}
private int codeUnitMargin() {
return options.getInternalOutputMode().isGeneratingClassFiles() ? 3 : 1;
}
private int findIfsForCandidates(List<Interval> newSwitches, Switch theSwitch, IntList outliers) {
Set<Interval> switchesToRemove = new HashSet<>();
InternalOutputMode mode = options.getInternalOutputMode();
int outliersAsIfSize = 0;
// The candidateForIfs is either an index to a switch that can be eliminated totally or a sparse
// where removing a key may produce a greater saving. It is only if keys are small in the packed
// switch that removing the keys makes sense (size wise).
for (Interval candidate : newSwitches) {
int maxIfBudget = 10;
long switchSize = candidate.estimatedSize(mode);
int sizeOfAllKeysAsIf = sizeForKeysWrittenAsIfs(theSwitch.value().outType(), candidate.keys);
if (candidate.keys.size() <= maxIfBudget
&& sizeOfAllKeysAsIf < switchSize - codeUnitMargin()) {
outliersAsIfSize += sizeOfAllKeysAsIf;
switchesToRemove.add(candidate);
outliers.addAll(candidate.keys);
continue;
}
// One could do something clever here, but we use a simple algorithm that use the fact that
// all keys are sorted in ascending order and that the smallest absolute value will give the
// best saving.
IntList candidateKeys = candidate.keys;
int smallestPosition = -1;
long smallest = Long.MAX_VALUE;
for (int i = 0; i < candidateKeys.size(); i++) {
long current = Math.abs((long) candidateKeys.getInt(i));
if (current < smallest) {
smallestPosition = i;
smallest = current;
}
}
// Add as many keys forward and backward as we have budget and we decrease in size.
IntList ifKeys = new IntArrayList();
ifKeys.add(candidateKeys.getInt(smallestPosition));
long previousSavings = 0;
long currentSavings =
switchSize
- sizeForKeysWrittenAsIfs(theSwitch.value().outType(), ifKeys)
- Switch.estimatedSparseSize(mode, candidateKeys.size() - ifKeys.size());
int minIndex = smallestPosition - 1;
int maxIndex = smallestPosition + 1;
while (ifKeys.size() < maxIfBudget && currentSavings > previousSavings) {
if (minIndex >= 0 && maxIndex < candidateKeys.size()) {
long valMin = Math.abs((long) candidateKeys.getInt(minIndex));
int valMax = Math.abs(candidateKeys.getInt(maxIndex));
if (valMax <= valMin) {
ifKeys.add(candidateKeys.getInt(maxIndex++));
} else {
ifKeys.add(candidateKeys.getInt(minIndex--));
}
} else if (minIndex >= 0) {
ifKeys.add(candidateKeys.getInt(minIndex--));
} else if (maxIndex < candidateKeys.size()) {
ifKeys.add(candidateKeys.getInt(maxIndex++));
} else {
// No more elements to add as if's.
break;
}
previousSavings = currentSavings;
currentSavings =
switchSize
- sizeForKeysWrittenAsIfs(theSwitch.value().outType(), ifKeys)
- Switch.estimatedSparseSize(mode, candidateKeys.size() - ifKeys.size());
}
if (previousSavings >= currentSavings) {
// Remove the last added key since it did not contribute to savings.
int lastKey = ifKeys.getInt(ifKeys.size() - 1);
ifKeys.removeInt(ifKeys.size() - 1);
if (lastKey == candidateKeys.getInt(minIndex + 1)) {
minIndex++;
} else {
maxIndex--;
}
}
// Adjust pointers into the candidate keys.
minIndex++;
maxIndex--;
if (ifKeys.size() > 0) {
int ifsSize = sizeForKeysWrittenAsIfs(theSwitch.value().outType(), ifKeys);
long newSwitchSize = Switch.estimatedSparseSize(mode, candidateKeys.size() - ifKeys.size());
if (newSwitchSize + ifsSize + codeUnitMargin() < switchSize) {
candidateKeys.removeElements(minIndex, maxIndex);
outliers.addAll(ifKeys);
outliersAsIfSize += ifsSize;
}
}
}
newSwitches.removeAll(switchesToRemove);
return outliersAsIfSize;
}
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 {
// If there are more than 1 key, we use the following algorithm to find keys to combine.
// First, scan through the keys forward and combine each packed interval with the
// previous interval if it gives a net saving.
// Secondly, go through all created intervals and combine the ones without a saving into
// a single interval and keep a max number of packed switches.
// Finally, go through all intervals and check if the switch or part of the switch
// should be transformed to ifs.
// Phase 1: Combine packed intervals.
InternalOutputMode mode = options.getInternalOutputMode();
int[] keys = theSwitch.getKeys();
int maxNumberOfIfsOrSwitches = 10;
PriorityQueue<Interval> biggestPackedSavings =
new PriorityQueue<>(
(x, y) -> Long.compare(y.packedSavings(mode), x.packedSavings(mode)));
Set<Interval> biggestPackedSet = new HashSet<>();
List<Interval> intervals = new ArrayList<>();
int previousKey = keys[0];
IntList currentKeys = new IntArrayList();
currentKeys.add(previousKey);
Interval previousInterval = null;
for (int i = 1; i < keys.length; i++) {
int key = keys[i];
if (((long) key - (long) previousKey) > 1) {
Interval current = new Interval(currentKeys);
Interval added = combineOrAddInterval(intervals, previousInterval, current);
if (added != current && biggestPackedSet.contains(previousInterval)) {
biggestPackedSet.remove(previousInterval);
biggestPackedSavings.remove(previousInterval);
}
tryAddToBiggestSavings(
biggestPackedSet, biggestPackedSavings, added, maxNumberOfIfsOrSwitches);
previousInterval = added;
currentKeys = new IntArrayList();
}
currentKeys.add(key);
previousKey = key;
}
Interval current = new Interval(currentKeys);
Interval added = combineOrAddInterval(intervals, previousInterval, current);
if (added != current && biggestPackedSet.contains(previousInterval)) {
biggestPackedSet.remove(previousInterval);
biggestPackedSavings.remove(previousInterval);
}
tryAddToBiggestSavings(
biggestPackedSet, biggestPackedSavings, added, maxNumberOfIfsOrSwitches);
// Phase 2: combine sparse intervals into a single bin.
// Check if we should save a space for a sparse switch, if so, remove the switch with
// the smallest savings.
if (biggestPackedSet.size() == maxNumberOfIfsOrSwitches
&& maxNumberOfIfsOrSwitches < intervals.size()) {
biggestPackedSet.remove(biggestPackedSavings.poll());
}
Interval sparse = null;
List<Interval> newSwitches = new ArrayList<>(maxNumberOfIfsOrSwitches);
for (int i = 0; i < intervals.size(); i++) {
Interval interval = intervals.get(i);
if (biggestPackedSet.contains(interval)) {
newSwitches.add(interval);
} else if (sparse == null) {
sparse = interval;
newSwitches.add(sparse);
} else {
sparse.addInterval(interval);
}
}
// Phase 3: at this point we are guaranteed to have the biggest saving switches
// in newIntervals, potentially with a switch combining the remaining intervals.
// Now we check to see if we can create any if's to reduce size.
IntList outliers = new IntArrayList();
int outliersAsIfSize = findIfsForCandidates(newSwitches, theSwitch, outliers);
long newSwitchesSize = 0;
List<IntList> newSwitchSequences = new ArrayList<>(newSwitches.size());
for (Interval interval : newSwitches) {
newSwitchesSize += interval.estimatedSize(mode);
newSwitchSequences.add(interval.keys);
}
long currentSize = Switch.estimatedSize(mode, theSwitch.getKeys());
if (newSwitchesSize + outliersAsIfSize + codeUnitMargin() < currentSize) {
convertSwitchToSwitchAndIfs(
code, blocksIterator, block, iterator, theSwitch, newSwitchSequences, outliers);
}
}
}
}
}
// 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 collapseTrivialGotos(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;
do {
nextBlock = iterator.hasNext() ? iterator.next() : null;
if (block.isTrivialGoto()) {
collapseTrivialGoto(code, block, nextBlock, blocksToRemove);
}
if (block.exit().isIf()) {
collapseIfTrueTarget(block);
}
if (block.exit().isSwitch()) {
collapseNonFallthroughSwitchTargets(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()) {
collapseTrivialGoto(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, GraphLense graphLense, OptimizationFeedback feedback) {
if (method.isStatic()) {
// 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()
&& checksNullBeforeSideEffect(code, appInfo, graphLense, 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. Note that we don't
// check what is passed to superclass initializer as arguments, only check
// that it is not the instance being initialized.
//
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;
}
DexClass clazz = appInfo.definitionFor(method.method.holder);
if (clazz == null) {
return;
}
boolean receiverUsedAsReturnValue = false;
boolean seenSuperInitCall = false;
for (Instruction insn : receiver.uniqueUsers()) {
if (insn.isReturn()) {
receiverUsedAsReturnValue = true;
continue;
}
if (insn.isInstanceGet() || insn.isInstancePut()) {
if (insn.isInstancePut()) {
InstancePut instancePutInstruction = insn.asInstancePut();
// Only allow field writes to the receiver.
if (instancePutInstruction.object() != receiver) {
return;
}
// Do not allow the receiver to escape via a field write.
if (instancePutInstruction.value() == receiver) {
return;
}
}
DexField field = insn.asFieldInstruction().getField();
if (field.clazz == clazz.type && clazz.lookupInstanceField(field) != null) {
// Require only accessing instance fields of the *current* class.
continue;
}
return;
}
// If this is an instance initializer allow one call to superclass instance initializer.
if (insn.isInvokeDirect()) {
InvokeDirect invokedDirect = insn.asInvokeDirect();
DexMethod invokedMethod = invokedDirect.getInvokedMethod();
if (dexItemFactory.isConstructor(invokedMethod) &&
invokedMethod.holder == clazz.superType &&
invokedDirect.inValues().lastIndexOf(receiver) == 0 &&
!seenSuperInitCall &&
instanceInitializer) {
seenSuperInitCall = true;
continue;
}
// We don't support other direct calls yet.
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));
}
public void identifyTrivialInitializer(
DexEncodedMethod method, IRCode code, OptimizationFeedback feedback) {
boolean isInstanceInitializer = method.isInstanceInitializer();
boolean isClassInitializer = method.isClassInitializer();
assert isInstanceInitializer || isClassInitializer;
if (method.accessFlags.isNative()) {
return;
}
DexClass clazz = appInfo.definitionFor(method.method.holder);
if (clazz == null) {
return;
}
feedback.setTrivialInitializer(method,
isInstanceInitializer
? computeInstanceInitializerInfo(code, clazz, appInfo::definitionFor)
: computeClassInitializerInfo(code, clazz));
}
public void identifyParameterUsages(
DexEncodedMethod method, IRCode code, OptimizationFeedback feedback) {
List<ParameterUsage> usages = new ArrayList<>();
List<Value> values = code.collectArguments();
for (int i = 0; i < values.size(); i++) {
Value value = values.get(i);
if (value.numberOfPhiUsers() > 0) {
continue;
}
ParameterUsage usage = collectParameterUsages(i, value);
if (usage != null) {
usages.add(usage);
}
}
feedback.setParameterUsages(method, usages.isEmpty() ? null : new ParameterUsagesInfo(usages));
}
private ParameterUsage collectParameterUsages(int i, Value value) {
ParameterUsageBuilder builder = new ParameterUsageBuilder(value, i);
for (Instruction user : value.uniqueUsers()) {
if (!builder.note(user)) {
return null;
}
}
return builder.build();
}
// This method defines trivial instance initializer as follows:
//
// ** The initializer may call the initializer of the base class, which
// itself must be trivial.
//
// ** java.lang.Object.<init>() is considered trivial.
//
// ** all arguments passed to a super-class initializer must be non-throwing
// constants or arguments.
//
// ** Assigns arguments or non-throwing constants to fields of this class.
//
// (Note that this initializer does not have to have zero arguments.)
private TrivialInitializer computeInstanceInitializerInfo(
IRCode code, DexClass clazz, Function<DexType, DexClass> typeToClass) {
Value receiver = code.getThis();
InstructionIterator it = code.instructionIterator();
while (it.hasNext()) {
Instruction insn = it.next();
if (insn.isReturn()) {
continue;
}
if (insn.isArgument()) {
continue;
}
if (insn.isConstInstruction()) {
if (insn.instructionInstanceCanThrow()) {
return null;
} else {
continue;
}
}
if (insn.isInvokeDirect()) {
InvokeDirect invokedDirect = insn.asInvokeDirect();
DexMethod invokedMethod = invokedDirect.getInvokedMethod();
if (invokedMethod.holder != clazz.superType) {
return null;
}
// java.lang.Object.<init>() is considered trivial.
if (invokedMethod == dexItemFactory.objectMethods.constructor) {
continue;
}
DexClass holder = typeToClass.apply(invokedMethod.holder);
if (holder == null) {
return null;
}
DexEncodedMethod callTarget = holder.lookupDirectMethod(invokedMethod);
if (callTarget == null ||
!callTarget.isInstanceInitializer() ||
callTarget.getOptimizationInfo().getTrivialInitializerInfo() == null ||
invokedDirect.getReceiver() != receiver) {
return null;
}
for (Value value : invokedDirect.inValues()) {
if (value != receiver && !(value.isConstant() || value.isArgument())) {
return null;
}
}
continue;
}
if (insn.isInstancePut()) {
InstancePut instancePut = insn.asInstancePut();
DexEncodedField field = clazz.lookupInstanceField(instancePut.getField());
if (field == null ||
instancePut.object() != receiver ||
(instancePut.value() != receiver && !instancePut.value().isArgument())) {
return null;
}
continue;
}
if (insn.isGoto()) {
// Trivial goto to the next block.
if (insn.asGoto().isTrivialGotoToTheNextBlock(code)) {
continue;
}
return null;
}
// Other instructions make the instance initializer not eligible.
return null;
}
return TrivialInstanceInitializer.INSTANCE;
}
// This method defines trivial class initializer as follows:
//
// ** The initializer may only instantiate an instance of the same class,
// initialize it with a call to a trivial constructor *without* arguments,
// and assign this instance to a static final field of the same class.
//
private synchronized TrivialInitializer computeClassInitializerInfo(IRCode code, DexClass clazz) {
InstructionIterator it = code.instructionIterator();
Value createdSingletonInstance = null;
DexField singletonField = null;
while (it.hasNext()) {
Instruction insn = it.next();
if (insn.isReturn()) {
continue;
}
if (insn.isNewInstance()) {
NewInstance newInstance = insn.asNewInstance();
if (createdSingletonInstance != null ||
newInstance.clazz != clazz.type ||
insn.outValue() == null) {
return null;
}
createdSingletonInstance = insn.outValue();
continue;
}
if (insn.isInvokeDirect()) {
InvokeDirect invokedDirect = insn.asInvokeDirect();
if (createdSingletonInstance == null ||
invokedDirect.getReceiver() != createdSingletonInstance) {
return null;
}
DexEncodedMethod callTarget = clazz.lookupDirectMethod(invokedDirect.getInvokedMethod());
if (callTarget == null ||
!callTarget.isInstanceInitializer() ||
!callTarget.method.proto.parameters.isEmpty() ||
callTarget.getOptimizationInfo().getTrivialInitializerInfo() == null) {
return null;
}
continue;
}
if (insn.isStaticPut()) {
StaticPut staticPut = insn.asStaticPut();
if (singletonField != null ||
createdSingletonInstance == null ||
staticPut.inValue() != createdSingletonInstance) {
return null;
}
DexEncodedField field = clazz.lookupStaticField(staticPut.getField());
if (field == null ||
!field.accessFlags.isStatic() ||
!field.accessFlags.isFinal()) {
return null;
}
singletonField = field.field;
continue;
}
// Other instructions make the class initializer not eligible.
return null;
}
return singletonField == null ? null : new TrivialClassInitializer(singletonField);
}
/**
* 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,
CONDITIONAL_EFFECT,
OTHER_EFFECT,
NO_EFFECT
}
/**
* Returns true if the given code unconditionally throws if value 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.
*/
public static boolean checksNullBeforeSideEffect(
IRCode code, AppInfo appInfo, GraphLense graphLense, Value value) {
return alwaysTriggerExpectedEffectBeforeAnythingElse(
code,
(instr, it) -> {
BasicBlock currentBlock = instr.getBlock();
// If the code explicitly checks the nullability of the value, we should visit the next
// block that corresponds to the null value where NPE semantic could be preserved.
if (!currentBlock.hasCatchHandlers() && isNullCheck(instr, value)) {
return InstructionEffect.CONDITIONAL_EFFECT;
}
if (isKotlinNullCheck(appInfo, graphLense, instr, value)) {
DexMethod invokedMethod = instr.asInvokeStatic().getInvokedMethod();
// Kotlin specific way of throwing NPE: throwParameterIsNullException.
// Similarly, combined with the above CONDITIONAL_EFFECT, the code checks on NPE on
// the value.
if (invokedMethod.name
== appInfo.dexItemFactory.kotlin.intrinsics.throwParameterIsNullException.name) {
// We found a NPE (or similar exception) throwing code.
// Combined with the above CONDITIONAL_EFFECT, the code checks NPE on the value.
for (BasicBlock predecessor : currentBlock.getPredecessors()) {
Instruction last =
predecessor.listIterator(predecessor.getInstructions().size()).previous();
if (isNullCheck(last, value)) {
return InstructionEffect.DESIRED_EFFECT;
}
}
// Hitting here means that this call might be used for other parameters. If we don't
// bail out, it will be regarded as side effects for the current value.
return InstructionEffect.NO_EFFECT;
} else {
// Kotlin specific way of checking parameter nullness: checkParameterIsNotNull.
assert invokedMethod.name
== appInfo.dexItemFactory.kotlin.intrinsics.checkParameterIsNotNull.name;
return InstructionEffect.DESIRED_EFFECT;
}
}
if (isInstantiationOfNullPointerException(instr, it, appInfo.dexItemFactory)) {
it.next(); // Skip call to NullPointerException.<init>.
return InstructionEffect.NO_EFFECT;
} else if (instr.throwsNpeIfValueIsNull(value, appInfo.dexItemFactory)) {
// 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 (!currentBlock.hasCatchHandlers()) {
// We found a NPE check on the value.
return InstructionEffect.DESIRED_EFFECT;
}
} else if (instructionHasSideEffects(instr)) {
// If the current instruction is const-string, this could load the parameter name.
// Just make sure it is indeed not throwing.
if (instr.isConstString() && !instr.instructionInstanceCanThrow()) {
return InstructionEffect.NO_EFFECT;
}
// We found a side effect before a NPE check.
return InstructionEffect.OTHER_EFFECT;
}
return InstructionEffect.NO_EFFECT;
});
}
// Note that this method may have false positives, since the application could in principle
// declare a method called checkParameterIsNotNull(parameter, message) or
// throwParameterIsNullException(parameterName) in a package that starts with "kotlin".
private static boolean isKotlinNullCheck(
AppInfo appInfo, GraphLense graphLense, Instruction instr, Value value) {
if (!instr.isInvokeStatic()) {
return false;
}
// We need to strip the holder, since Kotlin adds different versions of null-check machinery,
// e.g., kotlin.collections.ArraysKt___ArraysKt... or kotlin.jvm.internal.ArrayIteratorKt...
MethodSignatureEquivalence wrapper = MethodSignatureEquivalence.get();
Wrapper<DexMethod> checkParameterIsNotNull =
wrapper.wrap(appInfo.dexItemFactory.kotlin.intrinsics.checkParameterIsNotNull);
Wrapper<DexMethod> throwParamIsNullException =
wrapper.wrap(appInfo.dexItemFactory.kotlin.intrinsics.throwParameterIsNullException);
DexMethod invokedMethod =
graphLense.getOriginalMethodSignature(instr.asInvokeStatic().getInvokedMethod());
Wrapper<DexMethod> methodWrap = wrapper.wrap(invokedMethod);
if (methodWrap.equals(throwParamIsNullException)
|| (methodWrap.equals(checkParameterIsNotNull) && instr.inValues().get(0).equals(value))) {
if (invokedMethod.getHolder().getPackageDescriptor().startsWith(Kotlin.NAME)) {
return true;
}
}
return false;
}
private static boolean isNullCheck(Instruction instr, Value value) {
return instr.isIf() && instr.asIf().isZeroTest()
&& instr.inValues().get(0).equals(value)
&& (instr.asIf().getType() == Type.EQ || instr.asIf().getType() == Type.NE);
}
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 instruction is {@code v <- new-instance NullPointerException},
* and the next instruction is {@code invoke-direct v, NullPointerException.<init>()}.
*/
private static boolean isInstantiationOfNullPointerException(
Instruction instruction, InstructionListIterator it, DexItemFactory dexItemFactory) {
if (!instruction.isNewInstance()
|| instruction.asNewInstance().clazz != dexItemFactory.npeType) {
return false;
}
Instruction next = it.peekNext();
if (next == null
|| !next.isInvokeDirect()
|| next.asInvokeDirect().getInvokedMethod() != dexItemFactory.npeMethods.init) {
return false;
}
return true;
}
/**
* 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, it) -> {
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.
*
* <p>Note: we do not track phis so we may return false negative. This is a conservative approach.
*/
private static boolean alwaysTriggerExpectedEffectBeforeAnythingElse(
IRCode code, BiFunction<Instruction, InstructionListIterator, 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;
InstructionListIterator it = currentBlock.listIterator();
while (result == InstructionEffect.NO_EFFECT && it.hasNext()) {
result = function.apply(it.next(), it);
}
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 if (result == InstructionEffect.CONDITIONAL_EFFECT) {
assert !currentBlock.getNormalSuccessors().isEmpty();
Instruction lastInstruction = currentBlock.getInstructions().getLast();
assert lastInstruction.isIf();
// The current path is checking if the value of interest is null. Go deeper into the path
// that corresponds to the null value.
BasicBlock targetIfReceiverIsNull = lastInstruction.asIf().targetFromCondition(0);
if (!targetIfReceiverIsNull.isMarked(color)) {
worklist.add(targetIfReceiverIsNull);
targetIfReceiverIsNull.mark(color);
}
} 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, int argumentIndex) {
// TODO(sgjesse): Insert cast if required.
TypeLatticeElement returnType =
TypeLatticeElement.fromDexType(
invoke.getInvokedMethod().proto.returnType, maybeNull(), appInfo);
TypeLatticeElement argumentType =
TypeLatticeElement.fromDexType(
getArgumentType(invoke, argumentIndex), maybeNull(), appInfo);
if (appView != null && appView.enableWholeProgramOptimizations()) {
return argumentType.lessThanOrEqual(returnType, appInfo);
} else {
return argumentType.equals(returnType);
}
}
private DexType getArgumentType(InvokeMethod invoke, int argumentIndex) {
if (invoke.isInvokeStatic()) {
return invoke.getInvokedMethod().proto.parameters.values[argumentIndex];
}
if (argumentIndex == 0) {
return invoke.getInvokedMethod().getHolder();
}
return invoke.getInvokedMethod().proto.parameters.values[argumentIndex - 1];
}
// 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();
Set<Value> needToWidenValues = Sets.newIdentityHashSet();
Set<Value> needToNarrowValues = Sets.newIdentityHashSet();
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()) {
if (libraryMethodsReturningReceiver.contains(invoke.getInvokedMethod())) {
if (checkArgumentType(invoke, 0)) {
invoke.outValue().replaceUsers(invoke.arguments().get(0));
invoke.setOutValue(null);
}
} else if (appInfoWithLiveness != null) {
DexEncodedMethod target =
invoke.lookupSingleTarget(appInfoWithLiveness, code.method.method.getHolder());
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 >= 0 && checkArgumentType(invoke, argumentIndex)) {
Value argument = invoke.arguments().get(argumentIndex);
Value outValue = invoke.outValue();
assert outValue.verifyCompatible(argument.outType());
if (argument.getTypeLattice().lessThanOrEqual(
outValue.getTypeLattice(), appInfo)) {
needToNarrowValues.addAll(outValue.affectedValues());
} else {
needToWidenValues.addAll(outValue.affectedValues());
}
outValue.replaceUsers(argument);
invoke.setOutValue(null);
}
}
}
}
}
}
}
if (!needToWidenValues.isEmpty() || !needToNarrowValues.isEmpty()) {
TypeAnalysis analysis = new TypeAnalysis(appInfo, code.method);
// If out value of invoke < argument (e.g., losing non-null info), widen users type.
if (!needToWidenValues.isEmpty()) {
analysis.widening(needToWidenValues);
}
// Otherwise, i.e., argument has more precise types, narrow users type.
if (!needToNarrowValues.isEmpty()) {
analysis.narrowing(needToNarrowValues);
}
}
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(
AppInfo appInfo, DexEncodedMethod method, IRCode code, OptimizationFeedback feedback) {
if (method.isClassInitializer()) {
if (!hasJavacClinitAssertionCode(code)) {
return;
}
// Mark the clinit as having code to turn on assertions.
feedback.setInitializerEnablingJavaAssertions(method);
} else {
// If the clinit of this class did not have have code to turn on assertions don't try to
// remove assertion code from the method.
DexClass clazz = appInfo.definitionFor(method.method.holder);
if (clazz == null) {
return;
}
DexEncodedMethod clinit = clazz.getClassInitializer();
if (clinit == null
|| !clinit.isProcessed()
|| !clinit.getOptimizationInfo().isInitializerEnablingJavaAssertions()) {
return;
}
}
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.createIntConstant(0));
}
} 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.createIntConstant(1));
}
}
}
}
private boolean isClassDesiredAssertionStatusInvoke(Instruction instruction) {
return instruction.isInvokeMethod()
&& instruction.asInvokeMethod().getInvokedMethod()
== dexItemFactory.classMethods.desiredAssertionStatus;
}
private boolean isAssertionsDisabledFieldPut(Instruction instruction) {
return instruction.isStaticPut()
&& instruction.asStaticPut().getField().name == dexItemFactory.assertionsDisabled;
}
private boolean isNotDebugInstruction(Instruction instruction) {
return !instruction.isDebugInstruction();
}
private Value blockWithSingleConstNumberAndGoto(BasicBlock block) {
InstructionIterator iterator = block.iterator();
Instruction constNumber = iterator.nextUntil(this::isNotDebugInstruction);
if (constNumber == null || !constNumber.isConstNumber()) {
return null;
}
Instruction exit = iterator.nextUntil(this::isNotDebugInstruction);
return exit != null && exit.isGoto() ? constNumber.outValue() : null;
}
private Value blockWithAssertionsDisabledFieldPut(BasicBlock block) {
InstructionIterator iterator = block.iterator();
Instruction fieldPut = iterator.nextUntil(this::isNotDebugInstruction);
return fieldPut != null
&& isAssertionsDisabledFieldPut(fieldPut) ? fieldPut.inValues().get(0) : null;
}
private boolean hasJavacClinitAssertionCode(IRCode code) {
InstructionIterator iterator = code.instructionIterator();
Instruction current = iterator.nextUntil(this::isClassDesiredAssertionStatusInvoke);
if (current == null) {
return false;
}
Value DesiredAssertionStatus = current.outValue();
assert iterator.hasNext();
current = iterator.next();
if (!current.isIf()
|| !current.asIf().isZeroTest()
|| current.asIf().inValues().get(0) != DesiredAssertionStatus) {
return false;
}
If theIf = current.asIf();
BasicBlock trueTarget = theIf.getTrueTarget();
BasicBlock falseTarget = theIf.fallthroughBlock();
if (trueTarget == falseTarget) {
return false;
}
Value trueValue = blockWithSingleConstNumberAndGoto(trueTarget);
Value falseValue = blockWithSingleConstNumberAndGoto(falseTarget);
if (trueValue == null
|| falseValue == null
|| (trueTarget.exit().asGoto().getTarget() != falseTarget.exit().asGoto().getTarget())) {
return false;
}
BasicBlock target = trueTarget.exit().asGoto().getTarget();
Value storeValue = blockWithAssertionsDisabledFieldPut(target);
return storeValue != null
&& storeValue.isPhi()
&& storeValue.asPhi().getOperands().size() == 2
&& storeValue.asPhi().getOperands().contains(trueValue)
&& storeValue.asPhi().getOperands().contains(falseValue);
}
// Check if the static put is a constant derived from the class holding the method.
// This checks for java.lang.Class.get*Name.
private boolean isClassNameConstantOf(DexClass clazz, StaticPut put) {
if (put.getField().type != dexItemFactory.stringType) {
return false;
}
if (put.inValue().definition != null) {
return isClassNameConstantOf(clazz, put.inValue().definition);
}
return false;
}
private boolean isClassNameConstantOf(DexClass clazz, Instruction instruction) {
if (instruction.isInvokeVirtual()) {
InvokeVirtual invoke = instruction.asInvokeVirtual();
if (dexItemFactory.classMethods.isReflectiveNameLookup(invoke.getInvokedMethod())
&& !invoke.inValues().get(0).isPhi()
&& invoke.inValues().get(0).definition.isConstClass()
&& invoke.inValues().get(0).definition.asConstClass().getValue() == clazz.type) {
return true;
}
}
return false;
}
public void collectClassInitializerDefaults(DexEncodedMethod method, IRCode code) {
if (!method.isClassInitializer()) {
return;
}
DexClass clazz = definitionFor(method.method.getHolder());
if (clazz == null) {
return;
}
// Collect straight-line static puts up to the first side-effect that is not
// a static put on a field on this class with a value that can be hoisted to
// the field initial value.
Set<StaticPut> puts = Sets.newIdentityHashSet();
Map<DexField, StaticPut> finalFieldPut = Maps.newIdentityHashMap();
computeUnnecessaryStaticPuts(code, method, clazz, puts, finalFieldPut);
if (!puts.isEmpty()) {
// Set initial values for static fields from the definitive static put instructions collected.
for (StaticPut put : finalFieldPut.values()) {
DexField field = put.getField();
DexEncodedField encodedField = appInfo.definitionFor(field);
Value inValue = put.inValue();
if (field.type == dexItemFactory.stringType) {
if (inValue.isConstant()) {
if (inValue.isConstNumber()) {
assert inValue.isZero();
encodedField.setStaticValue(DexValueNull.NULL);
} else if (inValue.isConstString()) {
ConstString cnst = inValue.getConstInstruction().asConstString();
encodedField.setStaticValue(new DexValueString(cnst.getValue()));
} else if (inValue.isDexItemBasedConstString()) {
DexItemBasedConstString cnst =
inValue.getConstInstruction().asDexItemBasedConstString();
assert !cnst.getClassNameComputationInfo().needsToComputeClassName();
encodedField.setStaticValue(
new DexItemBasedValueString(cnst.getItem(), cnst.getClassNameComputationInfo()));
} else {
assert false;
}
} else {
InvokeVirtual invoke = inValue.definition.asInvokeVirtual();
DexMethod invokedMethod = invoke.getInvokedMethod();
DexType holderType = method.method.getHolder();
DexClass holder = appInfo.definitionFor(holderType);
assert holder != null;
String descriptor = holderType.toDescriptorString();
DexItemBasedValueString deferred = null;
String name = null;
if (invokedMethod == appInfo.dexItemFactory.classMethods.getName) {
if (code.options.enableMinification
&& !converter.rootSet.noObfuscation.contains(holder)) {
deferred = new DexItemBasedValueString(
holderType, new ClassNameComputationInfo(NAME));
} else {
name = computeClassName(descriptor, holder, NAME);
}
} else if (invokedMethod == appInfo.dexItemFactory.classMethods.getTypeName) {
// TODO(b/119426668): desugar Type#getTypeName
} else if (invokedMethod == appInfo.dexItemFactory.classMethods.getCanonicalName) {
if (code.options.enableMinification
&& !converter.rootSet.noObfuscation.contains(holder)) {
deferred = new DexItemBasedValueString(
holderType, new ClassNameComputationInfo(CANONICAL_NAME));
} else {
name = computeClassName(descriptor, holder, CANONICAL_NAME);
}
} else if (invokedMethod == appInfo.dexItemFactory.classMethods.getSimpleName) {
if (code.options.enableMinification
&& !converter.rootSet.noObfuscation.contains(holder)) {
deferred = new DexItemBasedValueString(
holderType, new ClassNameComputationInfo(SIMPLE_NAME));
} else {
name = computeClassName(descriptor, holder, SIMPLE_NAME);
}
}
assert name != null || deferred != null;
if (name != null) {
encodedField.setStaticValue(new DexValueString(dexItemFactory.createString(name)));
} else {
assert deferred != null;
encodedField.setStaticValue(deferred);
}
}
} else if (field.type.isClassType() || field.type.isArrayType()) {
if (inValue.isZero()) {
encodedField.setStaticValue(DexValueNull.NULL);
} else {
throw new Unreachable("Unexpected default value for field type " + field.type + ".");
}
} else {
ConstNumber cnst = 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 field initial values.
List<Instruction> toRemove = new ArrayList<>();
InstructionIterator iterator = code.instructionIterator();
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) {
iterator = code.instructionIterator();
while (iterator.hasNext()) {
if (toRemove.contains(iterator.next())) {
iterator.remove();
}
}
}
}
}
private void computeUnnecessaryStaticPuts(IRCode code, DexEncodedMethod clinit, DexClass clazz,
Set<StaticPut> puts, Map<DexField, StaticPut> finalFieldPut) {
final int color = code.reserveMarkingColor();
try {
BasicBlock block = code.blocks.getFirst();
while (!block.isMarked(color) && block.getPredecessors().size() <= 1) {
block.mark(color);
InstructionListIterator it = block.listIterator();
while (it.hasNext()) {
Instruction instruction = it.next();
if (instructionHasSideEffects(instruction)) {
if (isClassNameConstantOf(clazz, instruction)) {
continue;
} else if (instruction.isStaticPut()) {
StaticPut put = instruction.asStaticPut();
if (put.getField().clazz != clazz.type) {
// Can cause clinit on another class which can read uninitialized static fields
// of this class.
return;
}
DexField field = put.getField();
if (clazz.definesStaticField(field)) {
if (put.inValue().isDexItemBasedConstStringThatNeedsToComputeClassName()) {
continue;
}
if (put.inValue().isConstant()) {
if ((field.type.isClassType() || field.type.isArrayType())
&& put.inValue().isZero()) {
finalFieldPut.put(put.getField(), put);
puts.add(put);
} else if (field.type.isPrimitiveType()
|| field.type == dexItemFactory.stringType) {
finalFieldPut.put(put.getField(), put);
puts.add(put);
}
} else if (isClassNameConstantOf(clazz, put)) {
// Collect put of class name constant as a potential default value.
finalFieldPut.put(put.getField(), put);
puts.add(put);
}
}
} else if (!instruction.isConstString()
&& !instruction.isDexItemBasedConstString()
&& !instruction.isConstClass()) {
// Allow const string and const class which can only throw exceptions as their
// side-effect. Bail out for anything else.
return;
}
}
}
if (block.exit().isGoto()) {
block = block.exit().asGoto().getTarget();
}
}
} finally {
code.returnMarkingColor(color);
}
}
DexClass definitionFor(DexType type) {
return converter.definitionFor(type);
}
public void removeTrivialCheckCastAndInstanceOfInstructions(
IRCode code, boolean enableWholeProgramOptimizations) {
if (!enableWholeProgramOptimizations) {
return;
}
InstructionIterator it = code.instructionIterator();
boolean needToRemoveTrivialPhis = false;
while (it.hasNext()) {
Instruction current = it.next();
if (current.isCheckCast()) {
boolean hasPhiUsers = current.outValue().numberOfPhiUsers() != 0;
if (removeCheckCastInstructionIfTrivial(current.asCheckCast(), it, code)) {
needToRemoveTrivialPhis |= hasPhiUsers;
}
} else if (current.isInstanceOf()) {
boolean hasPhiUsers = current.outValue().numberOfPhiUsers() != 0;
if (removeInstanceOfInstructionIfTrivial(current.asInstanceOf(), it, code)) {
needToRemoveTrivialPhis |= hasPhiUsers;
}
}
}
// ... 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();
}
assert code.isConsistentSSA();
}
// Returns true if the given check-cast instruction was removed.
private boolean removeCheckCastInstructionIfTrivial(
CheckCast checkCast, InstructionIterator it, IRCode code) {
Value inValue = checkCast.object();
Value outValue = checkCast.outValue();
DexType castType = checkCast.getType();
// If the cast type is not accessible in the current context, we should not remove the cast
// in order to preserve IllegalAccessError. Note that JVM and ART behave differently: see
// {@link com.android.tools.r8.ir.optimize.checkcast.IllegalAccessErrorTest}.
if (isTypeInaccessibleInCurrentContext(castType, code.method)) {
return false;
}
// 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(checkCast, it, inValue, outValue);
return true;
}
TypeLatticeElement inTypeLattice = inValue.getTypeLattice();
TypeLatticeElement outTypeLattice = outValue.getTypeLattice();
TypeLatticeElement castTypeLattice =
TypeLatticeElement.fromDexType(castType, inTypeLattice.nullability(), appInfo);
assert inTypeLattice.nullability().lessThanOrEqual(outTypeLattice.nullability());
if (inTypeLattice.lessThanOrEqual(castTypeLattice, appInfo)) {
// 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;
assert inTypeLattice.lessThanOrEqual(outTypeLattice, appInfo);
removeOrReplaceByDebugLocalWrite(checkCast, it, inValue, outValue);
return true;
}
// 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 !inTypeLattice.isDefinitelyNull();
assert outTypeLattice.asNullable().equals(castTypeLattice.asNullable());
return false;
}
private boolean isTypeInaccessibleInCurrentContext(DexType type, DexEncodedMethod context) {
DexType baseType = type.toBaseType(appInfo.dexItemFactory);
DexClass clazz = definitionFor(baseType);
if (clazz == null) {
// Conservatively say yes.
return true;
}
ConstraintWithTarget classVisibility =
ConstraintWithTarget.deriveConstraint(
context.method.getHolder(), baseType, clazz.accessFlags, appInfo);
return classVisibility == ConstraintWithTarget.NEVER;
}
// Returns true if the given instance-of instruction was removed.
private boolean removeInstanceOfInstructionIfTrivial(
InstanceOf instanceOf, InstructionIterator it, IRCode code) {
// If the instance-of type is not accessible in the current context, we should not remove the
// instance-of instruction in order to preserve IllegalAccessError.
if (isTypeInaccessibleInCurrentContext(instanceOf.type(), code.method)) {
return false;
}
Value inValue = instanceOf.value();
TypeLatticeElement inType = inValue.getTypeLattice();
TypeLatticeElement instanceOfType =
TypeLatticeElement.fromDexType(instanceOf.type(), inType.nullability(), appInfo);
InstanceOfResult result = InstanceOfResult.UNKNOWN;
if (inType.isDefinitelyNull()) {
result = InstanceOfResult.FALSE;
} else if (inType.lessThanOrEqual(instanceOfType, appInfo) && !inType.isNullable()) {
result = InstanceOfResult.TRUE;
} else if (!inValue.isPhi()
&& inValue.definition.isCreatingInstanceOrArray()
&& instanceOfType.strictlyLessThan(inType, appInfo)) {
result = InstanceOfResult.FALSE;
} else if (appInfo.hasLiveness()) {
if (instanceOf.type().isClassType()
&& isNeverInstantiatedDirectlyOrIndirectly(instanceOf.type())) {
// The type of the instance-of instruction is a program class, and is never instantiated
// directly or indirectly. Thus, the in-value must be null, meaning that the instance-of
// instruction will always evaluate to false.
result = InstanceOfResult.FALSE;
}
if (result == InstanceOfResult.UNKNOWN) {
if (inType.isClassType()
&& isNeverInstantiatedDirectlyOrIndirectly(
inType.asClassTypeLatticeElement().getClassType())) {
// The type of the in-value is a program class, and is never instantiated directly or
// indirectly. This, the in-value must be null, meaning that the instance-of instruction
// will always evaluate to false.
result = InstanceOfResult.FALSE;
}
}
}
if (result != InstanceOfResult.UNKNOWN) {
it.replaceCurrentInstruction(
new ConstNumber(
new Value(
code.valueNumberGenerator.next(),
TypeLatticeElement.INT,
instanceOf.outValue().getLocalInfo()),
result == InstanceOfResult.TRUE ? 1 : 0));
return true;
}
return false;
}
private boolean isNeverInstantiatedDirectlyOrIndirectly(DexType type) {
assert appInfo.hasLiveness();
assert type.isClassType();
DexClass clazz = appInfo.definitionFor(type);
return clazz != null
&& clazz.isProgramClass()
&& !appInfo.withLiveness().isInstantiatedDirectlyOrIndirectly(type);
}
public static void removeOrReplaceByDebugLocalWrite(
Instruction currentInstruction, InstructionIterator it, Value inValue, Value outValue) {
if (outValue.hasLocalInfo() && outValue.getLocalInfo() != inValue.getLocalInfo()) {
DebugLocalWrite debugLocalWrite = new DebugLocalWrite(outValue, inValue);
it.replaceCurrentInstruction(debugLocalWrite);
} else {
if (outValue.hasLocalInfo()) {
assert outValue.getLocalInfo() == inValue.getLocalInfo();
// Should remove the end-marker before replacing the current instruction.
currentInstruction.removeDebugValue(outValue.getLocalInfo());
}
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;
}
}
for (Phi user : value.uniquePhiUsers()) {
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 as well as ConstString instructions.
shortenLiveRangesInsideBlock(
code,
block,
dominatorTreeMemoization,
addConstantInBlock,
insn ->
(insn.isConstNumber() && insn.outValue().numberOfAllUsers() != 0)
|| (insn.isConstString() && insn.outValue().numberOfAllUsers() != 0));
} else {
// For all following blocks only process ConstString with just one use.
shortenLiveRangesInsideBlock(
code,
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(
IRCode code,
BasicBlock block,
Supplier<DominatorTree> dominatorTreeMemoization,
Map<BasicBlock, List<Instruction>> addConstantInBlock,
Predicate<ConstInstruction> selector) {
InstructionListIterator it = block.listIterator();
while (it.hasNext()) {
Instruction next = it.next();
if (!next.isConstInstruction()) {
continue;
}
ConstInstruction instruction = next.asConstInstruction();
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;
}
}
List<Instruction> csts =
addConstantInBlock.computeIfAbsent(dominator, k -> new ArrayList<>());
ConstInstruction copy = instruction.isConstNumber()
? ConstNumber.copyOf(code, instruction.asConstNumber())
: ConstString.copyOf(code, instruction.asConstString());
instruction.outValue().replaceUsers(copy.outValue());
csts.add(copy);
}
}
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.
insertAt.nextUntil(i ->
i.inValues().contains(instruction.outValue())
|| i.isJumpInstruction()
|| (hasCatchHandlers && i.instructionTypeCanThrow())
|| (options.canHaveCmpIfFloatBug() && i.isCmp()));
Instruction next = insertAt.previous();
instruction.setPosition(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();
if (index < 0 || index >= values.length) {
return null;
}
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());
}
Value invokeValue = code.createValue(
newArray.outValue().getTypeLattice(), newArray.getLocalInfo());
InvokeNewArray invoke =
new InvokeNewArray(dexItemFactory.stringArrayType, invokeValue, stringValues);
for (Value value : newArray.inValues()) {
value.removeUser(newArray);
}
newArray.outValue().replaceUsers(invokeValue);
it.removeOrReplaceByDebugLocalRead();
instructionToInsertForArray.put(invokeValue, invoke);
storesToRemoveForArray.put(invokeValue, size);
} 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;
}
if (block.hasCatchHandlers()) {
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) {
// Set the position of the new array construction to be the position of the
// last removed put at which point we are now adding the construction.
construction.setPosition(instruction.getPosition());
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.singleUniqueUser();
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);
overwrittenLocal.addDebugLocalEnd(inValue.definition);
}
if (prevInstruction != null &&
(prevInstruction.outValue() == null
|| !prevInstruction.outValue().hasLocalInfo()
|| !instruction.getDebugValues().contains(prevInstruction.outValue()))) {
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) {
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()) {
LongInterval interval = inValues.get(0).getValueRange();
if (!interval.containsValue(0)) {
// Interval doesn't contain zero at all.
int sign = Long.signum(interval.getMin());
simplifyIfWithKnownCondition(code, block, theIf, sign);
} else {
// Interval contains zero.
switch (theIf.getType()) {
case GE:
case LT:
// [a, b] >= 0 is always true if a >= 0.
// [a, b] < 0 is always false if a >= 0.
// In both cases a zero condition takes the right branch.
if (interval.getMin() == 0) {
simplifyIfWithKnownCondition(code, block, theIf, 0);
}
break;
case LE:
case GT:
// [a, b] <= 0 is always true if b <= 0.
// [a, b] > 0 is always false if b <= 0.
if (interval.getMax() == 0) {
simplifyIfWithKnownCondition(code, block, theIf, 0);
}
break;
case EQ:
case NE:
// Only a single element interval [0, 0] can be dealt with here.
// Such intervals should have been replaced by constants.
assert !interval.isSingleValue();
break;
}
}
} else {
LongInterval leftRange = inValues.get(0).getValueRange();
LongInterval rightRange = inValues.get(1).getValueRange();
// Two overlapping ranges. Check for single point overlap.
if (!leftRange.overlapsWith(rightRange)) {
// No overlap.
int cond = Long.signum(leftRange.getMin() - rightRange.getMin());
simplifyIfWithKnownCondition(code, block, theIf, cond);
} else {
// The two intervals overlap. We can simplify if they overlap at the end points.
switch (theIf.getType()) {
case LT:
case GE:
// [a, b] < [c, d] is always false when a == d.
// [a, b] >= [c, d] is always true when a == d.
// In both cases 0 condition will choose the right branch.
if (leftRange.getMin() == rightRange.getMax()) {
simplifyIfWithKnownCondition(code, block, theIf, 0);
}
break;
case GT:
case LE:
// [a, b] > [c, d] is always false when b == c.
// [a, b] <= [c, d] is always true when b == c.
// In both cases 0 condition will choose the right branch.
if (leftRange.getMax() == rightRange.getMin()) {
simplifyIfWithKnownCondition(code, block, theIf, 0);
}
break;
case EQ:
case NE:
// Since there is overlap EQ and NE cannot be determined.
break;
}
}
}
} 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 {
TypeLatticeElement l = inValues.get(0).getTypeLattice();
if (!l.isPrimitive() && !l.isNullable()) {
simplifyIfWithKnownCondition(code, block, theIf, 1);
}
}
}
}
}
Set<Value> affectedValues = code.removeUnreachableBlocks();
if (!affectedValues.isEmpty()) {
new TypeAnalysis(appInfo, code.method).narrowing(affectedValues);
}
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));
}
/**
* This optimization exploits that we can sometimes learn the constant value of an SSA value that
* flows into an if-eq of if-neq instruction.
*
* <p>Consider the following example:
*
* <pre>
* 1. if (obj != null) {
* 2. return doStuff();
* 3. }
* 4. return null;
* </pre>
*
* <p>Since we know that `obj` is null in all blocks that are dominated by the false-target of the
* if-instruction in line 1, we can safely replace the null-constant in line 4 by `obj`, and
* thereby save a const-number instruction.
*/
public void redundantConstNumberRemoval(IRCode code) {
Supplier<Long2ReferenceMap<List<ConstNumber>>> constantsByValue =
Suppliers.memoize(() -> getConstantsByValue(code));
Supplier<DominatorTree> dominatorTree = Suppliers.memoize(() -> new DominatorTree(code));
boolean changed = false;
for (BasicBlock block : code.blocks) {
Instruction lastInstruction = block.getInstructions().getLast();
if (!lastInstruction.isIf()) {
continue;
}
If ifInstruction = lastInstruction.asIf();
Type type = ifInstruction.getType();
Value lhs = ifInstruction.inValues().get(0);
Value rhs = !ifInstruction.isZeroTest() ? ifInstruction.inValues().get(1) : null;
if (!ifInstruction.isZeroTest() && !lhs.isConstNumber() && !rhs.isConstNumber()) {
// We can only conclude anything from an if-instruction if it is a zero-test or if one of
// the two operands is a constant.
continue;
}
// If the type is neither EQ nor NE, we cannot conclude anything about any of the in-values
// of the if-instruction from the outcome of the if-instruction.
if (type != Type.EQ && type != Type.NE) {
continue;
}
BasicBlock trueTarget, falseTarget;
if (type == Type.EQ) {
trueTarget = ifInstruction.getTrueTarget();
falseTarget = ifInstruction.fallthroughBlock();
} else {
falseTarget = ifInstruction.getTrueTarget();
trueTarget = ifInstruction.fallthroughBlock();
}
if (ifInstruction.isZeroTest()) {
changed |=
replaceDominatedConstNumbers(0, lhs, trueTarget, constantsByValue, dominatorTree);
if (lhs.knownToBeBoolean()) {
changed |=
replaceDominatedConstNumbers(1, lhs, falseTarget, constantsByValue, dominatorTree);
}
} else {
assert rhs != null;
if (lhs.isConstNumber()) {
ConstNumber lhsAsNumber = lhs.getConstInstruction().asConstNumber();
changed |=
replaceDominatedConstNumbers(
lhsAsNumber.getRawValue(), rhs, trueTarget, constantsByValue, dominatorTree);
if (lhs.knownToBeBoolean() && rhs.knownToBeBoolean()) {
changed |=
replaceDominatedConstNumbers(
negateBoolean(lhsAsNumber), rhs, falseTarget, constantsByValue, dominatorTree);
}
} else {
assert rhs.isConstNumber();
ConstNumber rhsAsNumber = rhs.getConstInstruction().asConstNumber();
changed |=
replaceDominatedConstNumbers(
rhsAsNumber.getRawValue(), lhs, trueTarget, constantsByValue, dominatorTree);
if (lhs.knownToBeBoolean() && rhs.knownToBeBoolean()) {
changed |=
replaceDominatedConstNumbers(
negateBoolean(rhsAsNumber), lhs, falseTarget, constantsByValue, dominatorTree);
}
}
}
if (constantsByValue.get().isEmpty()) {
break;
}
}
if (changed) {
code.removeAllTrivialPhis();
}
assert code.isConsistentSSA();
}
private static Long2ReferenceMap<List<ConstNumber>> getConstantsByValue(IRCode code) {
// A map from the raw value of constants in `code` to the const number instructions that define
// the given raw value (irrespective of the type of the raw value).
Long2ReferenceMap<List<ConstNumber>> constantsByValue = new Long2ReferenceOpenHashMap<>();
// Initialize `constantsByValue`.
Iterable<Instruction> instructions = code::instructionIterator;
for (Instruction instruction : instructions) {
if (instruction.isConstNumber()) {
ConstNumber constNumber = instruction.asConstNumber();
if (constNumber.outValue().hasLocalInfo()) {
// Not necessarily constant, because it could be changed in the debugger.
continue;
}
long rawValue = constNumber.getRawValue();
if (constantsByValue.containsKey(rawValue)) {
constantsByValue.get(rawValue).add(constNumber);
} else {
List<ConstNumber> list = new ArrayList<>();
list.add(constNumber);
constantsByValue.put(rawValue, list);
}
}
}
return constantsByValue;
}
private static int negateBoolean(ConstNumber number) {
assert number.outValue().knownToBeBoolean();
return number.getRawValue() == 0 ? 1 : 0;
}
private boolean replaceDominatedConstNumbers(
long withValue,
Value newValue,
BasicBlock dominator,
Supplier<Long2ReferenceMap<List<ConstNumber>>> constantsByValueSupplier,
Supplier<DominatorTree> dominatorTree) {
if (newValue.hasLocalInfo()) {
// We cannot replace a constant with a value that has local info, because that could change
// debugging behavior.
return false;
}
Long2ReferenceMap<List<ConstNumber>> constantsByValue = constantsByValueSupplier.get();
List<ConstNumber> constantsWithValue = constantsByValue.get(withValue);
if (constantsWithValue == null || constantsWithValue.isEmpty()) {
return false;
}
boolean changed = false;
ListIterator<ConstNumber> constantWithValueIterator = constantsWithValue.listIterator();
while (constantWithValueIterator.hasNext()) {
ConstNumber constNumber = constantWithValueIterator.next();
Value value = constNumber.outValue();
assert !value.hasLocalInfo();
assert constNumber.getRawValue() == withValue;
BasicBlock block = constNumber.getBlock();
// If the following condition does not hold, then the if-instruction does not dominate the
// block containing the constant, although the true or false target does.
if (block == dominator && block.getPredecessors().size() != 1) {
// This should generally not happen, but it is possible to write bytecode where it does.
assert false;
continue;
}
if (value.knownToBeBoolean() && !newValue.knownToBeBoolean()) {
// We cannot replace a boolean by a none-boolean since that can lead to verification
// errors. For example, the following code fails with "register v1 has type Imprecise
// Constant: 127 but expected Boolean return-1nr".
//
// public boolean convertIntToBoolean(int v1) {
// const/4 v0, 0x1
// if-eq v1, v0, :eq_true
// const/4 v1, 0x0
// :eq_true
// return v1
// }
continue;
}
if (dominatorTree.get().dominatedBy(block, dominator)) {
if (newValue.getTypeLattice().lessThanOrEqual(value.getTypeLattice(), appInfo)) {
value.replaceUsers(newValue);
block.listIterator(constNumber).removeOrReplaceByDebugLocalRead();
constantWithValueIterator.remove();
changed = true;
} else if (value.getTypeLattice().isNullType()) {
// TODO(b/120257211): Need a mechanism to determine if `newValue` can be used at all of
// the use sites of `value` without introducing a type error.
}
}
}
if (constantsWithValue.isEmpty()) {
constantsByValue.remove(withValue);
}
return changed;
}
// 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().lookupSingleTarget(
appInfoWithLiveness, code.method.method.getHolder());
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.
ConstNumber nullConstant = code.createConstNull(gotoInsn.getLocalInfo());
nullConstant.setPosition(insn.getPosition());
throwNullInsnIterator.add(nullConstant);
// Replace Goto with Throw.
Throw notReachableThrow = new Throw(nullConstant.outValue());
Instruction insnGoto = throwNullInsnIterator.next();
assert insnGoto.isGoto();
throwNullInsnIterator.replaceCurrentInstruction(notReachableThrow);
}
}
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.getTypeLattice(), 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();
}
/**
* Remove moves that are not actually used by instructions in exiting paths. These moves can arise
* due to debug local info needing a particular value and the live-interval for it then moves it
* back into the properly assigned register. If the register is only used for debug purposes, it
* is safe to just remove the move and update the local information accordingly.
*/
public static void removeUnneededMovesOnExitingPaths(
IRCode code, LinearScanRegisterAllocator allocator) {
if (!code.options.debug) {
return;
}
for (BasicBlock block : code.blocks) {
// Skip non-exit blocks.
if (!block.getSuccessors().isEmpty()) {
continue;
}
// Skip blocks with no locals at entry.
Int2ReferenceMap<DebugLocalInfo> localsAtEntry = block.getLocalsAtEntry();
if (localsAtEntry == null || localsAtEntry.isEmpty()) {
continue;
}
// Find the locals state after spill moves.
DebugLocalsChange postSpillLocalsChange = null;
for (Instruction instruction : block.getInstructions()) {
if (instruction.getNumber() != -1 || postSpillLocalsChange != null) {
break;
}
postSpillLocalsChange = instruction.asDebugLocalsChange();
}
// Skip if the locals state did not change.
if (postSpillLocalsChange == null
|| !postSpillLocalsChange.apply(new Int2ReferenceOpenHashMap<>(localsAtEntry))) {
continue;
}
// Collect the moves that can safely be removed.
Set<Move> unneededMoves = computeUnneededMoves(block, postSpillLocalsChange, allocator);
if (unneededMoves.isEmpty()) {
continue;
}
Int2IntMap previousMapping = new Int2IntOpenHashMap();
Int2IntMap mapping = new Int2IntOpenHashMap();
ListIterator<Instruction> it = block.getInstructions().listIterator();
while (it.hasNext()) {
Instruction instruction = it.next();
if (instruction.isMove()) {
Move move = instruction.asMove();
if (unneededMoves.contains(move)) {
int dst = allocator.getRegisterForValue(move.dest(), move.getNumber());
int src = allocator.getRegisterForValue(move.src(), move.getNumber());
int mappedSrc = mapping.getOrDefault(src, src);
mapping.put(dst, mappedSrc);
it.remove();
}
} else if (instruction.isDebugLocalsChange()) {
DebugLocalsChange change = instruction.asDebugLocalsChange();
updateDebugLocalsRegisterMap(previousMapping, change.getEnding());
updateDebugLocalsRegisterMap(mapping, change.getStarting());
previousMapping = mapping;
mapping = new Int2IntOpenHashMap(previousMapping);
}
}
}
}
private static Set<Move> computeUnneededMoves(
BasicBlock block,
DebugLocalsChange postSpillLocalsChange,
LinearScanRegisterAllocator allocator) {
Set<Move> unneededMoves = Sets.newIdentityHashSet();
IntSet usedRegisters = new IntOpenHashSet();
IntSet clobberedRegisters = new IntOpenHashSet();
// Backwards instruction scan collecting the registers used by actual instructions.
boolean inEntrySpillMoves = false;
InstructionListIterator it = block.listIterator(block.getInstructions().size());
while (it.hasPrevious()) {
Instruction instruction = it.previous();
if (instruction == postSpillLocalsChange) {
inEntrySpillMoves = true;
}
// If this is a move in the block-entry spill moves check if it is unneeded.
if (inEntrySpillMoves && instruction.isMove()) {
Move move = instruction.asMove();
int dst = allocator.getRegisterForValue(move.dest(), move.getNumber());
int src = allocator.getRegisterForValue(move.src(), move.getNumber());
if (!usedRegisters.contains(dst) && !clobberedRegisters.contains(src)) {
unneededMoves.add(move);
continue;
}
}
if (instruction.outValue() != null && instruction.outValue().needsRegister()) {
int register =
allocator.getRegisterForValue(instruction.outValue(), instruction.getNumber());
// The register is defined anew, so uses before this are on distinct values.
usedRegisters.remove(register);
// Mark it clobbered to avoid any uses in locals after this point to become invalid.
clobberedRegisters.add(register);
}
if (!instruction.inValues().isEmpty()) {
for (Value inValue : instruction.inValues()) {
if (inValue.needsRegister()) {
int register = allocator.getRegisterForValue(inValue, instruction.getNumber());
// Record the register as being used.
usedRegisters.add(register);
}
}
}
}
return unneededMoves;
}
private static void updateDebugLocalsRegisterMap(
Int2IntMap mapping, Int2ReferenceMap<DebugLocalInfo> locals) {
// If nothing is mapped nothing needs to be changed.
if (mapping.isEmpty()) {
return;
}
// Locals is final, so we copy and clear it during update.
Int2ReferenceMap<DebugLocalInfo> copy = new Int2ReferenceOpenHashMap<>(locals);
locals.clear();
for (Entry<DebugLocalInfo> entry : copy.int2ReferenceEntrySet()) {
int oldRegister = entry.getIntKey();
int newRegister = mapping.getOrDefault(oldRegister, oldRegister);
locals.put(newRegister, entry.getValue());
}
}
// 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) {
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) {
TypeLatticeElement typeLattice =
TypeLatticeElement.stringClassType(appInfo, definitelyNotNull());
Value value = code.createValue(typeLattice);
ThrowingInfo throwingInfo =
options.isGeneratingClassFiles() ? ThrowingInfo.NO_THROW : ThrowingInfo.CAN_THROW;
iterator.add(new ConstString(value, dexItemFactory.createString(s), throwingInfo));
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();
DexType javaLangSystemType = dexItemFactory.createType("Ljava/lang/System;");
DexType javaIoPrintStreamType = dexItemFactory.createType("Ljava/io/PrintStream;");
Value out = code.createValue(
TypeLatticeElement.fromDexType(javaIoPrintStreamType, definitelyNotNull(), appInfo));
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(
out, dexItemFactory.createField(javaLangSystemType, javaIoPrintStreamType, "out")));
Value value = addConstString(code, iterator, "INVOKE ");
iterator.add(new InvokeVirtual(print, null, ImmutableList.of(out, value)));
value = addConstString(code, iterator, 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(), position);
code.blocks.add(eol);
BasicBlock successor = block.unlinkSingleSuccessor();
block.link(eol);
eol.link(successor);
Value argument = arguments.get(i);
if (!argument.getTypeLattice().isReference()) {
iterator.add(new InvokeVirtual(print, null, ImmutableList.of(out, primitive)));
} else {
// Insert "if (argument != null) ...".
successor = block.unlinkSingleSuccessor();
If theIf = new 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(), position);
code.blocks.add(isNullBlock);
BasicBlock isNotNullBlock = BasicBlock.createGotoBlock(code.blocks.size(), position);
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(TypeLatticeElement.classClassType(appInfo, definitelyNotNull()));
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;
}
}
}
}
}
}
// If an exceptional edge could target a conditional-loop header ensure that we have a
// materializing instruction on that path to work around a bug in some L x86_64 non-emulator VMs.
// See b/111337896.
public void workaroundExceptionTargetingLoopHeaderBug(IRCode code) {
for (BasicBlock block : code.blocks) {
if (block.hasCatchHandlers()) {
for (BasicBlock handler : block.getCatchHandlers().getUniqueTargets()) {
// We conservatively assume that a block with at least two normal predecessors is a loop
// header. If we ever end up computing exact loop headers, use that here instead.
// The loop is conditional if it has at least two normal successors.
BasicBlock target = handler.endOfGotoChain();
if (target.getPredecessors().size() > 2
&& target.getNormalPredecessors().size() > 1
&& target.getNormalSuccessors().size() > 1) {
Instruction fixit = new AlwaysMaterializingNop();
fixit.setBlock(handler);
fixit.setPosition(handler.getPosition());
handler.getInstructions().addFirst(fixit);
}
}
}
}
}
}