Google Git
Sign in
r8 / r8.git / d54131344be4ed23f1bab0c47f96670cd1324160 / . / src / main / java / com / android / tools / r8 / ir / optimize / CodeRewriter.java
blob: 36d70df206102c0a70c9a8d2e79d8f20723e6663 [file] [log] [blame]
// 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.graph.DexProgramClass.asProgramClassOrNull;
import static com.android.tools.r8.ir.analysis.type.Nullability.definitelyNotNull;
import static com.android.tools.r8.ir.analysis.type.Nullability.maybeNull;
import com.android.tools.r8.algorithms.scc.SCC;
import com.android.tools.r8.contexts.CompilationContext.MethodProcessingContext;
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.AccessControl;
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.DexClassAndMethod;
import com.android.tools.r8.graph.DexEncodedField;
import com.android.tools.r8.graph.DexEncodedMethod;
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.DexProgramClass;
import com.android.tools.r8.graph.DexProto;
import com.android.tools.r8.graph.DexString;
import com.android.tools.r8.graph.DexType;
import com.android.tools.r8.graph.FieldResolutionResult.SuccessfulFieldResolutionResult;
import com.android.tools.r8.graph.ProgramMethod;
import com.android.tools.r8.horizontalclassmerging.HorizontalClassMergerUtils;
import com.android.tools.r8.ir.analysis.equivalence.BasicBlockBehavioralSubsumption;
import com.android.tools.r8.ir.analysis.type.TypeAnalysis;
import com.android.tools.r8.ir.analysis.type.TypeElement;
import com.android.tools.r8.ir.analysis.value.AbstractValue;
import com.android.tools.r8.ir.analysis.value.ConstantOrNonConstantNumberValue;
import com.android.tools.r8.ir.analysis.value.SingleConstClassValue;
import com.android.tools.r8.ir.analysis.value.SingleFieldValue;
import com.android.tools.r8.ir.code.AlwaysMaterializingNop;
import com.android.tools.r8.ir.code.ArrayLength;
import com.android.tools.r8.ir.code.ArrayPut;
import com.android.tools.r8.ir.code.Assume;
import com.android.tools.r8.ir.code.BasicBlock;
import com.android.tools.r8.ir.code.Binop;
import com.android.tools.r8.ir.code.CatchHandlers;
import com.android.tools.r8.ir.code.CheckCast;
import com.android.tools.r8.ir.code.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.DominatorTree;
import com.android.tools.r8.ir.code.Goto;
import com.android.tools.r8.ir.code.IRCode;
import com.android.tools.r8.ir.code.IRMetadata;
import com.android.tools.r8.ir.code.If;
import com.android.tools.r8.ir.code.If.Type;
import com.android.tools.r8.ir.code.InstanceFieldInstruction;
import com.android.tools.r8.ir.code.InstanceGet;
import com.android.tools.r8.ir.code.InstanceOf;
import com.android.tools.r8.ir.code.Instruction;
import com.android.tools.r8.ir.code.Instruction.SideEffectAssumption;
import com.android.tools.r8.ir.code.InstructionIterator;
import com.android.tools.r8.ir.code.InstructionListIterator;
import com.android.tools.r8.ir.code.InstructionOrPhi;
import com.android.tools.r8.ir.code.IntSwitch;
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.InvokeMethodWithReceiver;
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.StaticGet;
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.MethodProcessor;
import com.android.tools.r8.ir.optimize.UtilityMethodsForCodeOptimizations.UtilityMethodForCodeOptimizations;
import com.android.tools.r8.ir.optimize.controlflow.SwitchCaseAnalyzer;
import com.android.tools.r8.ir.optimize.info.MethodOptimizationInfo;
import com.android.tools.r8.ir.regalloc.LinearScanRegisterAllocator;
import com.android.tools.r8.shaking.AppInfoWithLiveness;
import com.android.tools.r8.utils.BooleanUtils;
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.SetUtils;
import com.google.common.base.Equivalence;
import com.google.common.base.Equivalence.Wrapper;
import com.google.common.base.Suppliers;
import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Iterables;
import com.google.common.collect.ListMultimap;
import com.google.common.collect.Sets;
import com.google.common.collect.Streams;
import it.unimi.dsi.fastutil.ints.Int2IntMap;
import it.unimi.dsi.fastutil.ints.Int2IntOpenHashMap;
import it.unimi.dsi.fastutil.ints.Int2ReferenceAVLTreeMap;
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.ArrayList;
import java.util.Arrays;
import java.util.BitSet;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.IdentityHashMap;
import java.util.LinkedHashMap;
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.Consumer;
import java.util.function.Predicate;
import java.util.function.Supplier;
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 AppView<?> appView;
private final DexItemFactory dexItemFactory;
private final InternalOptions options;
public CodeRewriter(AppView<?> appView, IRConverter converter) {
this.appView = appView;
this.converter = converter;
this.options = appView.options();
this.dexItemFactory = appView.dexItemFactory();
}
public static void removeAssumeInstructions(AppView<?> appView, IRCode code) {
// We need to update the types of all values whose definitions depend on a non-null value.
// This is needed to preserve soundness of the types after the Assume instructions have been
// removed.
//
// As an example, consider a check-cast instruction on the form "z = (T) y". If y used to be
// defined by a NonNull instruction, then the type analysis could have used this information
// to mark z as non-null. However, cleanupNonNull() have now replaced y by a nullable value x.
// Since z is defined as "z = (T) x", and x is nullable, it is no longer sound to have that z
// is not nullable. This is fixed by rerunning the type analysis for the affected values.
Set<Value> valuesThatRequireWidening = Sets.newIdentityHashSet();
InstructionListIterator it = code.instructionListIterator();
boolean needToCheckTrivialPhis = false;
while (it.hasNext()) {
Instruction instruction = it.next();
// The following deletes Assume instructions and replaces any specialized value by its
// original value:
// y <- Assume(x)
// ...
// y.foo()
//
// becomes:
//
// x.foo()
if (instruction.isAssume()) {
Assume assumeInstruction = instruction.asAssume();
Value src = assumeInstruction.src();
Value dest = assumeInstruction.outValue();
valuesThatRequireWidening.addAll(dest.affectedValues());
// Replace `dest` by `src`.
needToCheckTrivialPhis |= dest.numberOfPhiUsers() > 0;
dest.replaceUsers(src);
it.remove();
}
}
// Assume insertion may introduce phis, e.g.,
// y <- Assume(x)
// ...
// z <- phi(x, y)
//
// Therefore, Assume elimination may result in a trivial phi:
// z <- phi(x, x)
if (needToCheckTrivialPhis) {
code.removeAllDeadAndTrivialPhis(valuesThatRequireWidening);
}
if (!valuesThatRequireWidening.isEmpty()) {
new TypeAnalysis(appView).widening(valuesThatRequireWidening);
}
assert Streams.stream(code.instructions()).noneMatch(Instruction::isAssume);
}
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.entryBlock() == 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;
}
// Rewrite 'throw new NullPointerException()' to 'throw null'.
public void rewriteThrowNullPointerException(IRCode code) {
boolean shouldRemoveUnreachableBlocks = false;
for (BasicBlock block : code.blocks) {
InstructionListIterator it = block.listIterator(code);
while (it.hasNext()) {
Instruction instruction = it.next();
// Check for the patterns 'if (x == null) throw null' and
// 'if (x == null) throw new NullPointerException()'.
if (instruction.isIf()) {
if (appView
.dexItemFactory()
.objectsMethods
.isRequireNonNullMethod(code.method().getReference())) {
continue;
}
If ifInstruction = instruction.asIf();
if (!ifInstruction.isZeroTest()) {
continue;
}
Value value = ifInstruction.lhs();
if (!value.getType().isReferenceType()) {
assert value.getType().isPrimitiveType();
continue;
}
BasicBlock valueIsNullTarget = ifInstruction.targetFromCondition(0);
if (valueIsNullTarget.getPredecessors().size() != 1
|| !valueIsNullTarget.exit().isThrow()) {
continue;
}
Throw throwInstruction = valueIsNullTarget.exit().asThrow();
Value exceptionValue = throwInstruction.exception().getAliasedValue();
Value message;
if (exceptionValue.isConstZero()) {
message = null;
} else if (exceptionValue.isDefinedByInstructionSatisfying(Instruction::isNewInstance)) {
NewInstance newInstance = exceptionValue.definition.asNewInstance();
if (newInstance.clazz != dexItemFactory.npeType) {
continue;
}
if (newInstance.outValue().numberOfAllUsers() != 2) {
continue; // Could be mutated before it is thrown.
}
InvokeDirect constructorCall = newInstance.getUniqueConstructorInvoke(dexItemFactory);
if (constructorCall == null) {
continue;
}
DexMethod invokedMethod = constructorCall.getInvokedMethod();
if (invokedMethod == dexItemFactory.npeMethods.init) {
message = null;
} else if (invokedMethod == dexItemFactory.npeMethods.initWithMessage) {
if (!appView.options().canUseJavaUtilObjectsRequireNonNull()) {
continue;
}
message = constructorCall.getArgument(1);
} else {
continue;
}
} else {
continue;
}
boolean canDetachValueIsNullTarget = true;
for (Instruction i : valueIsNullTarget.instructionsBefore(throwInstruction)) {
if (!i.isBlockLocalInstructionWithoutSideEffects(appView, code.context())) {
canDetachValueIsNullTarget = false;
break;
}
}
if (!canDetachValueIsNullTarget) {
continue;
}
if (message != null) {
Instruction definition = message.definition;
if (message.definition.getBlock() == valueIsNullTarget) {
it.previous();
Instruction entry;
do {
entry = valueIsNullTarget.getInstructions().removeFirst();
it.add(entry);
} while (entry != definition);
it.next();
}
}
rewriteIfToRequireNonNull(
block,
it,
ifInstruction,
ifInstruction.targetFromCondition(1),
valueIsNullTarget,
message,
throwInstruction.getPosition());
shouldRemoveUnreachableBlocks = true;
}
// Check for 'new-instance NullPointerException' with 2 users, not declaring a local and
// not ending the scope of any locals.
if (instruction.isNewInstance()
&& instruction.asNewInstance().clazz == dexItemFactory.npeType
&& instruction.outValue().numberOfAllUsers() == 2
&& !instruction.outValue().hasLocalInfo()
&& instruction.getDebugValues().isEmpty()) {
if (it.hasNext()) {
Instruction instruction2 = it.next();
// Check for 'invoke NullPointerException.init() not ending the scope of any locals
// and with the result of the first instruction as the argument. Also check that
// the two first instructions have the same position.
if (instruction2.isInvokeDirect()
&& instruction2.getDebugValues().isEmpty()) {
InvokeDirect invokeDirect = instruction2.asInvokeDirect();
if (invokeDirect.getInvokedMethod() == dexItemFactory.npeMethods.init
&& invokeDirect.getReceiver() == instruction.outValue()
&& invokeDirect.arguments().size() == 1
&& invokeDirect.getPosition() == instruction.getPosition()) {
if (it.hasNext()) {
Instruction instruction3 = it.next();
// Finally check that the last instruction is a throw of the initialized
// exception object and replace with 'throw null' if so.
if (instruction3.isThrow()
&& instruction3.asThrow().exception() == instruction.outValue()) {
// Create const 0 with null type and a throw using that value.
Instruction nullPointer = code.createConstNull();
Instruction throwInstruction = new Throw(nullPointer.outValue());
// Preserve positions: we have checked that the first two original instructions
// have the same position.
assert instruction.getPosition() == instruction2.getPosition();
nullPointer.setPosition(instruction.getPosition());
throwInstruction.setPosition(instruction3.getPosition());
// Copy debug values from original throw to new throw to correctly end scope
// of locals.
instruction3.moveDebugValues(throwInstruction);
// Remove the three original instructions.
it.remove();
it.previous();
it.remove();
it.previous();
it.remove();
// Replace them with 'const 0' and 'throw'.
it.add(nullPointer);
it.add(throwInstruction);
}
}
}
}
}
}
}
}
if (shouldRemoveUnreachableBlocks) {
Set<Value> affectedValues = code.removeUnreachableBlocks();
if (!affectedValues.isEmpty()) {
new TypeAnalysis(appView).narrowing(affectedValues);
}
}
assert code.isConsistentSSA();
}
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.entryBlock() == 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(
AppView<?> appView, IRCode code) {
if (!appView.options().canHaveDex2OatInliningIssue() || code.hasCatchHandlers()) {
// Catch handlers disables inlining, so if the method already has catch handlers
// there is nothing to do.
return;
}
int selfRecursionFanOut = 0;
Instruction lastSelfRecursiveCall = null;
for (Instruction i : code.instructions()) {
if (i.isInvokeMethod()
&& i.asInvokeMethod().getInvokedMethod() == code.method().getReference()) {
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(code, lastSelfRecursiveCall);
splitIterator.previous();
BasicBlock newBlock = splitIterator.split(code, 1);
// Generate rethrow block.
DexType guard = appView.dexItemFactory().throwableType;
BasicBlock rethrowBlock =
BasicBlock.createRethrowBlock(code, lastSelfRecursiveCall.getPosition(), guard, appView);
code.blocks.add(rethrowBlock);
// Add catch handler to the block containing the last recursive call.
newBlock.appendCatchHandler(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 Int2ReferenceSortedMap<BasicBlock> keyToTarget = new Int2ReferenceAVLTreeMap<>();
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(IRMetadata metadata) {
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());
IntSwitch newSwitch = new IntSwitch(value, keys, targetBlockIndices, fallthroughIndex);
newSwitch.setPosition(position);
BasicBlock newSwitchBlock = BasicBlock.createSwitchBlock(blockNumber, newSwitch, metadata);
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, code.metadata(), rightConst);
} else {
newIf = new If(Type.EQ, left);
ifBlock = BasicBlock.createIfBlock(blockNumber, newIf, code.metadata());
}
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,
IntSwitch 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.
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(code.getNextBlockNumber());
BasicBlock newSwitchBlock = switchBuilder.build(code.metadata());
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(code.getNextBlockNumber());
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 (!IntSwitch.canBePacked(mode, packedTargets)) {
return Long.MIN_VALUE + 1;
}
long sparseCost =
IntSwitch.baseSparseSize(mode) + IntSwitch.sparsePayloadSize(mode, keys.size());
long packedCost =
IntSwitch.basePackedSize(mode) + IntSwitch.packedPayloadSize(mode, packedTargets);
return sparseCost - packedCost;
}
public long estimatedSize(InternalOutputMode mode) {
return IntSwitch.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, IntSwitch 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)
- IntSwitch.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)
- IntSwitch.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 =
IntSwitch.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 boolean rewriteSwitch(IRCode code) {
return rewriteSwitch(code, SwitchCaseAnalyzer.getInstance());
}
private boolean rewriteSwitch(IRCode code, SwitchCaseAnalyzer switchCaseAnalyzer) {
if (!options.isSwitchRewritingEnabled()) {
return false;
}
if (!code.metadata().mayHaveSwitch()) {
return false;
}
return rewriteSwitchFull(code, switchCaseAnalyzer);
}
public void rewriteSwitchForMaxInt(IRCode code) {
if (options.canHaveSwitchMaxIntBug() && code.metadata().mayHaveSwitch()) {
// Always rewrite for workaround switch bug.
rewriteSwitchForMaxIntOnly(code);
}
}
private void rewriteSwitchForMaxIntOnly(IRCode code) {
boolean needToSplitCriticalEdges = false;
ListIterator<BasicBlock> blocksIterator = code.listIterator();
while (blocksIterator.hasNext()) {
BasicBlock block = blocksIterator.next();
InstructionListIterator iterator = block.listIterator(code);
while (iterator.hasNext()) {
Instruction instruction = iterator.next();
assert !instruction.isStringSwitch();
if (instruction.isIntSwitch()) {
IntSwitch intSwitch = instruction.asIntSwitch();
if (intSwitch.getKey(intSwitch.numberOfKeys() - 1) == Integer.MAX_VALUE) {
if (intSwitch.numberOfKeys() == 1) {
rewriteSingleKeySwitchToIf(code, block, iterator, intSwitch);
} else {
IntList newSwitchSequences = new IntArrayList(intSwitch.numberOfKeys() - 1);
for (int i = 0; i < intSwitch.numberOfKeys() - 1; i++) {
newSwitchSequences.add(intSwitch.getKey(i));
}
IntList outliers = new IntArrayList(1);
outliers.add(Integer.MAX_VALUE);
convertSwitchToSwitchAndIfs(
code,
blocksIterator,
block,
iterator,
intSwitch,
ImmutableList.of(newSwitchSequences),
outliers);
}
needToSplitCriticalEdges = true;
}
}
}
}
// 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.
if (needToSplitCriticalEdges) {
code.splitCriticalEdges();
}
}
private boolean rewriteSwitchFull(IRCode code, SwitchCaseAnalyzer switchCaseAnalyzer) {
boolean needToRemoveUnreachableBlocks = false;
ListIterator<BasicBlock> blocksIterator = code.listIterator();
while (blocksIterator.hasNext()) {
BasicBlock block = blocksIterator.next();
InstructionListIterator iterator = block.listIterator(code);
while (iterator.hasNext()) {
Instruction instruction = iterator.next();
if (instruction.isSwitch()) {
Switch theSwitch = instruction.asSwitch();
if (options.testing.enableDeadSwitchCaseElimination) {
SwitchCaseEliminator eliminator =
removeUnnecessarySwitchCases(code, theSwitch, iterator, switchCaseAnalyzer);
if (eliminator != null) {
if (eliminator.mayHaveIntroducedUnreachableBlocks()) {
needToRemoveUnreachableBlocks = true;
}
iterator.previous();
instruction = iterator.next();
if (instruction.isGoto()) {
continue;
}
assert instruction.isSwitch();
theSwitch = instruction.asSwitch();
}
}
if (theSwitch.isIntSwitch()) {
rewriteIntSwitch(code, blocksIterator, block, iterator, theSwitch.asIntSwitch());
}
}
}
}
// 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();
Set<Value> affectedValues =
needToRemoveUnreachableBlocks ? code.removeUnreachableBlocks() : ImmutableSet.of();
if (!affectedValues.isEmpty()) {
new TypeAnalysis(appView).narrowing(affectedValues);
}
assert code.isConsistentSSA();
return !affectedValues.isEmpty();
}
private void rewriteSingleKeySwitchToIf(
IRCode code, BasicBlock block, InstructionListIterator iterator, IntSwitch theSwitch) {
// Rewrite the switch to an if.
int fallthroughBlockIndex = theSwitch.getFallthroughBlockIndex();
int caseBlockIndex = theSwitch.targetBlockIndices()[0];
if (fallthroughBlockIndex < caseBlockIndex) {
block.swapSuccessorsByIndex(fallthroughBlockIndex, caseBlockIndex);
}
If replacement;
if (theSwitch.isIntSwitch() && theSwitch.asIntSwitch().getFirstKey() == 0) {
replacement = new If(Type.EQ, theSwitch.value());
} else {
Instruction labelConst = theSwitch.materializeFirstKey(appView, code);
labelConst.setPosition(theSwitch.getPosition());
iterator.previous();
iterator.add(labelConst);
Instruction dummy = iterator.next();
assert dummy == theSwitch;
replacement = new If(Type.EQ, ImmutableList.of(theSwitch.value(), labelConst.outValue()));
}
iterator.replaceCurrentInstruction(replacement);
}
private void rewriteIntSwitch(
IRCode code,
ListIterator<BasicBlock> blockIterator,
BasicBlock block,
InstructionListIterator iterator,
IntSwitch theSwitch) {
if (disableSwitchToIfRewritingForClassIdComparisons(theSwitch)) {
return;
}
if (theSwitch.numberOfKeys() == 1) {
rewriteSingleKeySwitchToIf(code, block, iterator, theSwitch);
return;
}
// 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 =
appView.options().testing.enableSwitchToIfRewriting
? findIfsForCandidates(newSwitches, theSwitch, outliers)
: 0;
long newSwitchesSize = 0;
List<IntList> newSwitchSequences = new ArrayList<>(newSwitches.size());
for (Interval interval : newSwitches) {
newSwitchesSize += interval.estimatedSize(mode);
newSwitchSequences.add(interval.keys);
}
long currentSize = IntSwitch.estimatedSize(mode, theSwitch.getKeys());
if (newSwitchesSize + outliersAsIfSize + codeUnitMargin() < currentSize) {
convertSwitchToSwitchAndIfs(
code, blockIterator, block, iterator, theSwitch, newSwitchSequences, outliers);
}
}
// TODO(b/181732463): We currently disable switch-to-if rewritings for switches on $r8$classId
// field values (from horizontal class merging. See bug for more details.
private boolean disableSwitchToIfRewritingForClassIdComparisons(IntSwitch theSwitch) {
Value switchValue = theSwitch.value().getAliasedValue();
if (!switchValue.isDefinedByInstructionSatisfying(Instruction::isInstanceGet)) {
return false;
}
AppInfoWithLiveness appInfo = appView.appInfoWithLiveness();
if (appInfo == null) {
return false;
}
InstanceGet instanceGet = switchValue.getDefinition().asInstanceGet();
SuccessfulFieldResolutionResult resolutionResult =
appInfo.resolveField(instanceGet.getField()).asSuccessfulResolution();
if (resolutionResult == null) {
return false;
}
DexEncodedField resolvedField = resolutionResult.getResolvedField();
return HorizontalClassMergerUtils.isClassIdField(appView, resolvedField);
}
private SwitchCaseEliminator removeUnnecessarySwitchCases(
IRCode code,
Switch theSwitch,
InstructionListIterator iterator,
SwitchCaseAnalyzer switchCaseAnalyzer) {
BasicBlock defaultTarget = theSwitch.fallthroughBlock();
SwitchCaseEliminator eliminator = null;
BasicBlockBehavioralSubsumption behavioralSubsumption =
new BasicBlockBehavioralSubsumption(appView, code);
// Compute the set of switch cases that can be removed.
AbstractValue switchAbstractValue = theSwitch.value().getAbstractValue(appView, code.context());
for (int i = 0; i < theSwitch.numberOfKeys(); i++) {
BasicBlock targetBlock = theSwitch.targetBlock(i);
if (switchCaseAnalyzer.switchCaseIsAlwaysHit(theSwitch, i)) {
if (eliminator == null) {
eliminator = new SwitchCaseEliminator(theSwitch, iterator);
}
eliminator.markSwitchCaseAsAlwaysHit(i);
break;
}
// This switch case can be removed if the behavior of the target block is equivalent to the
// behavior of the default block, or if the switch case is unreachable.
if (switchCaseAnalyzer.switchCaseIsUnreachable(theSwitch, switchAbstractValue, i)
|| behavioralSubsumption.isSubsumedBy(targetBlock, defaultTarget)) {
if (eliminator == null) {
eliminator = new SwitchCaseEliminator(theSwitch, iterator);
}
eliminator.markSwitchCaseForRemoval(i);
}
}
if (eliminator == null || eliminator.isFallthroughLive()) {
if (switchCaseAnalyzer.switchFallthroughIsNeverHit(theSwitch, switchAbstractValue)) {
if (eliminator == null) {
eliminator = new SwitchCaseEliminator(theSwitch, iterator);
}
eliminator.markSwitchFallthroughAsNeverHit();
}
}
if (eliminator != null) {
eliminator.optimize();
}
return eliminator;
}
/**
* 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(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();
}
private boolean checkArgumentType(InvokeMethod invoke, int argumentIndex) {
// TODO(sgjesse): Insert cast if required.
TypeElement returnType =
TypeElement.fromDexType(invoke.getInvokedMethod().proto.returnType, maybeNull(), appView);
TypeElement argumentType =
TypeElement.fromDexType(getArgumentType(invoke, argumentIndex), maybeNull(), appView);
return appView.enableWholeProgramOptimizations()
? argumentType.lessThanOrEqual(returnType, appView)
: 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().holder;
}
return invoke.getInvokedMethod().proto.parameters.values[argumentIndex - 1];
}
// Replace result uses for methods where something is known about what is returned.
public boolean rewriteMoveResult(IRCode code) {
if (options.isGeneratingClassFiles() || !code.metadata().mayHaveInvokeMethod()) {
return false;
}
AssumeRemover assumeRemover = new AssumeRemover(appView, code);
boolean changed = false;
boolean mayHaveRemovedTrivialPhi = false;
Set<Value> affectedValues = Sets.newIdentityHashSet();
Set<BasicBlock> blocksToBeRemoved = Sets.newIdentityHashSet();
ListIterator<BasicBlock> blockIterator = code.listIterator();
while (blockIterator.hasNext()) {
BasicBlock block = blockIterator.next();
if (blocksToBeRemoved.contains(block)) {
continue;
}
InstructionListIterator iterator = block.listIterator(code);
while (iterator.hasNext()) {
InvokeMethod invoke = iterator.next().asInvokeMethod();
if (invoke == null || !invoke.hasOutValue() || invoke.outValue().hasLocalInfo()) {
continue;
}
// Check if the invoked method is known to return one of its arguments.
DexClassAndMethod target = invoke.lookupSingleTarget(appView, code.context());
if (target == null) {
continue;
}
MethodOptimizationInfo optimizationInfo = target.getDefinition().getOptimizationInfo();
if (optimizationInfo.returnsArgument()) {
int argumentIndex = optimizationInfo.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());
// Make sure that we are only narrowing information here. Note, in cases where
// we cannot find the definition of types, computing lessThanOrEqual will
// return false unless it is object.
if (argument.getType().lessThanOrEqual(outValue.getType(), appView)) {
affectedValues.addAll(outValue.affectedValues());
assumeRemover.markAssumeDynamicTypeUsersForRemoval(outValue);
mayHaveRemovedTrivialPhi |= outValue.numberOfPhiUsers() > 0;
outValue.replaceUsers(argument);
invoke.setOutValue(null);
changed = true;
}
}
}
}
}
assumeRemover.removeMarkedInstructions(blocksToBeRemoved).finish();
if (!blocksToBeRemoved.isEmpty()) {
code.removeBlocks(blocksToBeRemoved);
code.removeAllDeadAndTrivialPhis(affectedValues);
assert code.getUnreachableBlocks().isEmpty();
} else if (mayHaveRemovedTrivialPhi || assumeRemover.mayHaveIntroducedTrivialPhi()) {
code.removeAllDeadAndTrivialPhis(affectedValues);
}
if (!affectedValues.isEmpty()) {
new TypeAnalysis(appView).narrowing(affectedValues);
}
assert code.isConsistentSSA();
return changed;
}
enum RemoveCheckCastInstructionIfTrivialResult {
NO_REMOVALS,
REMOVED_CAST_DO_NARROW
}
public void removeTrivialCheckCastAndInstanceOfInstructions(
IRCode code,
ProgramMethod context,
MethodProcessor methodProcessor,
MethodProcessingContext methodProcessingContext) {
if (!appView.enableWholeProgramOptimizations()) {
return;
}
assert appView.appInfo().hasLiveness();
AppView<AppInfoWithLiveness> appViewWithLiveness = appView.withLiveness();
if (!appView.options().testing.enableCheckCastAndInstanceOfRemoval) {
return;
}
IRMetadata metadata = code.metadata();
if (!metadata.mayHaveCheckCast() && !metadata.mayHaveInstanceOf()) {
return;
}
// If we can remove a CheckCast it is due to us having at least as much information about the
// type as the CheckCast gives. We then need to propagate that information to the users of
// the CheckCast to ensure further optimizations and removals of CheckCast:
//
// : 1: NewArrayEmpty v2 <- v1(1) java.lang.String[] <-- v2 = String[]
// ...
// : 2: CheckCast v5 <- v2; java.lang.Object[] <-- v5 = Object[]
// ...
// : 3: ArrayGet v7 <- v5, v6(0) <-- v7 = Object
// : 4: CheckCast v8 <- v7; java.lang.String <-- v8 = String
// ...
//
// When looking at line 2 we can conclude that the CheckCast is trivial because v2 is String[]
// and remove it. However, v7 is still only known to be Object and we cannot remove the
// CheckCast at line 4 unless we update v7 with the most precise information by narrowing the
// affected values of v5. We therefore have to run the type analysis after each CheckCast
// removal.
TypeAnalysis typeAnalysis = new TypeAnalysis(appView);
Set<Value> affectedValues = Sets.newIdentityHashSet();
InstructionListIterator it = code.instructionListIterator();
boolean needToRemoveTrivialPhis = false;
while (it.hasNext()) {
Instruction current = it.next();
if (current.isCheckCast()) {
boolean hasPhiUsers = current.outValue().hasPhiUsers();
RemoveCheckCastInstructionIfTrivialResult removeResult =
removeCheckCastInstructionIfTrivial(
appViewWithLiveness,
current.asCheckCast(),
it,
code,
context,
affectedValues,
methodProcessor,
methodProcessingContext);
if (removeResult != RemoveCheckCastInstructionIfTrivialResult.NO_REMOVALS) {
assert removeResult == RemoveCheckCastInstructionIfTrivialResult.REMOVED_CAST_DO_NARROW;
needToRemoveTrivialPhis |= hasPhiUsers;
typeAnalysis.narrowing(affectedValues);
affectedValues.clear();
}
} else if (current.isInstanceOf()) {
boolean hasPhiUsers = current.outValue().hasPhiUsers();
if (removeInstanceOfInstructionIfTrivial(
appViewWithLiveness, 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.removeAllDeadAndTrivialPhis(affectedValues);
if (!affectedValues.isEmpty()) {
typeAnalysis.narrowing(affectedValues);
}
}
assert code.isConsistentSSA();
}
// Returns true if the given check-cast instruction was removed.
private RemoveCheckCastInstructionIfTrivialResult removeCheckCastInstructionIfTrivial(
AppView<AppInfoWithLiveness> appViewWithLiveness,
CheckCast checkCast,
InstructionListIterator it,
IRCode code,
ProgramMethod context,
Set<Value> affectedValues,
MethodProcessor methodProcessor,
MethodProcessingContext methodProcessingContext) {
Value inValue = checkCast.object();
Value outValue = checkCast.outValue();
DexType castType = checkCast.getType();
DexType baseCastType = castType.toBaseType(dexItemFactory);
// If the cast type is not accessible in the current context, we should not remove the cast
// in order to preserve runtime errors. Note that JVM and ART behave differently: see
// {@link com.android.tools.r8.ir.optimize.checkcast.IllegalAccessErrorTest}.
if (baseCastType.isClassType()) {
DexClass baseCastClass = appView.definitionFor(baseCastType);
if (baseCastClass == null
|| AccessControl.isClassAccessible(baseCastClass, code.context(), appViewWithLiveness)
.isPossiblyFalse()) {
return RemoveCheckCastInstructionIfTrivialResult.NO_REMOVALS;
}
}
// If the in-value is `null` and the cast-type is a float-array type, then trivial check-cast
// elimination may lead to verification errors. See b/123269162.
if (options.canHaveArtCheckCastVerifierBug()) {
if (inValue.getType().isNullType()
&& castType.isArrayType()
&& castType.toBaseType(dexItemFactory).isFloatType()) {
return RemoveCheckCastInstructionIfTrivialResult.NO_REMOVALS;
}
}
TypeElement inTypeLattice = inValue.getType();
TypeElement outTypeLattice = outValue.getType();
TypeElement castTypeLattice =
TypeElement.fromDexType(castType, inTypeLattice.nullability(), appView);
assert inTypeLattice.nullability().lessThanOrEqual(outTypeLattice.nullability());
if (inTypeLattice.lessThanOrEqual(castTypeLattice, appView)) {
// 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, appView);
// The removeOrReplaceByDebugLocalWrite will propagate the incoming value for the CheckCast
// to the users of the CheckCast's out value.
//
// v2 = CheckCast A v1 ~~> DebugLocalWrite $v0 <- v1
//
// The DebugLocalWrite is not a user of the outvalue, we therefore have to wait and take the
// CheckCast invalue users that includes the potential DebugLocalWrite.
removeOrReplaceByDebugLocalWrite(checkCast, it, inValue, outValue);
affectedValues.addAll(inValue.affectedValues());
return RemoveCheckCastInstructionIfTrivialResult.REMOVED_CAST_DO_NARROW;
}
// If values of cast type are guaranteed to be null, then the out-value must be null if the cast
// succeeds. After removing all usages of the out-value, the check-cast instruction is replaced
// by a call to throwClassCastExceptionIfNotNull() to allow dead code elimination of the cast
// type.
if (castType.isClassType()
&& castType.isAlwaysNull(appViewWithLiveness)
&& !outValue.hasDebugUsers()) {
// Replace all usages of the out-value by null.
it.previous();
Value nullValue = it.insertConstNullInstruction(code, options);
it.next();
checkCast.outValue().replaceUsers(nullValue);
affectedValues.addAll(nullValue.affectedValues());
// Replace the check-cast instruction by throwClassCastExceptionIfNotNull().
UtilityMethodForCodeOptimizations throwClassCastExceptionIfNotNullMethod =
UtilityMethodsForCodeOptimizations.synthesizeThrowClassCastExceptionIfNotNullMethod(
appView, methodProcessingContext);
throwClassCastExceptionIfNotNullMethod.optimize(methodProcessor);
InvokeStatic replacement =
InvokeStatic.builder()
.setMethod(throwClassCastExceptionIfNotNullMethod.getMethod())
.setSingleArgument(checkCast.object())
.setPosition(checkCast)
.build();
it.replaceCurrentInstruction(replacement);
assert replacement.lookupSingleTarget(appView, context) != null;
return RemoveCheckCastInstructionIfTrivialResult.REMOVED_CAST_DO_NARROW;
}
// 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() || (inValue.isPhi() && !inTypeLattice.isNullType());
assert outTypeLattice.equalUpToNullability(castTypeLattice);
return RemoveCheckCastInstructionIfTrivialResult.NO_REMOVALS;
}
// Returns true if the given instance-of instruction was removed.
private boolean removeInstanceOfInstructionIfTrivial(
AppView<AppInfoWithLiveness> appViewWithLiveness,
InstanceOf instanceOf,
InstructionListIterator it,
IRCode code) {
ProgramMethod context = code.context();
// 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.
DexType instanceOfBaseType = instanceOf.type().toBaseType(dexItemFactory);
if (instanceOfBaseType.isClassType()) {
DexClass instanceOfClass = appView.definitionFor(instanceOfBaseType);
if (instanceOfClass == null
|| AccessControl.isClassAccessible(instanceOfClass, context, appViewWithLiveness)
.isPossiblyFalse()) {
return false;
}
}
Value inValue = instanceOf.value();
TypeElement inType = inValue.getType();
TypeElement instanceOfType =
TypeElement.fromDexType(instanceOf.type(), inType.nullability(), appView);
Value aliasValue = inValue.getAliasedValue();
InstanceOfResult result = InstanceOfResult.UNKNOWN;
if (inType.isDefinitelyNull()) {
result = InstanceOfResult.FALSE;
} else if (inType.lessThanOrEqual(instanceOfType, appView) && !inType.isNullable()) {
result = InstanceOfResult.TRUE;
} else if (!aliasValue.isPhi()
&& aliasValue.definition.isCreatingInstanceOrArray()
&& instanceOfType.strictlyLessThan(inType, appView)) {
result = InstanceOfResult.FALSE;
} else if (appView.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.asClassType().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) {
Value aliasedValue =
inValue.getSpecificAliasedValue(
value ->
value.isDefinedByInstructionSatisfying(
Instruction::isAssumeWithDynamicTypeAssumption));
if (aliasedValue != null) {
TypeElement dynamicType =
aliasedValue
.definition
.asAssume()
.getDynamicTypeAssumption()
.getDynamicUpperBoundType();
if (dynamicType.isDefinitelyNull()) {
result = InstanceOfResult.FALSE;
} else if (dynamicType.lessThanOrEqual(instanceOfType, appView)
&& (!inType.isNullable() || !dynamicType.isNullable())) {
result = InstanceOfResult.TRUE;
}
}
}
}
if (result != InstanceOfResult.UNKNOWN) {
ConstNumber newInstruction =
new ConstNumber(
new Value(
code.valueNumberGenerator.next(),
TypeElement.getInt(),
instanceOf.outValue().getLocalInfo()),
result == InstanceOfResult.TRUE ? 1 : 0);
it.replaceCurrentInstruction(newInstruction);
return true;
}
return false;
}
private boolean isNeverInstantiatedDirectlyOrIndirectly(DexType type) {
assert appView.appInfo().hasLiveness();
assert type.isClassType();
DexProgramClass clazz = asProgramClassOrNull(appView.definitionFor(type));
return clazz != null
&& !appView.appInfo().withLiveness().isInstantiatedDirectlyOrIndirectly(clazz);
}
public static void removeOrReplaceByDebugLocalWrite(
Instruction currentInstruction, InstructionListIterator 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();
}
}
// 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(code);
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();
}
}
}
assert code.isConsistentSSA();
}
/**
* If an instruction is known to be a binop/lit8 or binop//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) {
if (!code.metadata().mayHaveArithmeticOrLogicalBinop()) {
return;
}
for (BasicBlock block : code.blocks) {
InstructionListIterator instructionIterator = block.listIterator(code);
// Collect all the non constant in values for binop/lit8 or binop/lit16 instructions.
Set<Value> binopsWithLit8OrLit16NonConstantValues = Sets.newIdentityHashSet();
while (instructionIterator.hasNext()) {
Instruction currentInstruction = instructionIterator.next();
if (!isBinopWithLit8OrLit16(currentInstruction)) {
continue;
}
Value value = binopWithLit8OrLit16NonConstant(currentInstruction.asBinop());
assert value != null;
binopsWithLit8OrLit16NonConstantValues.add(value);
}
if (binopsWithLit8OrLit16NonConstantValues.isEmpty()) {
continue;
}
// Find last use in block of all the non constant in values for binop/lit8 or binop/lit16
// instructions.
Reference2IntMap<Value> lastUseOfBinopsWithLit8OrLit16NonConstantValues =
new Reference2IntOpenHashMap<>();
lastUseOfBinopsWithLit8OrLit16NonConstantValues.defaultReturnValue(-1);
int currentInstructionNumber = block.getInstructions().size();
while (instructionIterator.hasPrevious()) {
Instruction currentInstruction = instructionIterator.previous();
currentInstructionNumber--;
for (Value value :
Iterables.concat(currentInstruction.inValues(), currentInstruction.getDebugValues())) {
if (!binopsWithLit8OrLit16NonConstantValues.contains(value)) {
continue;
}
if (!lastUseOfBinopsWithLit8OrLit16NonConstantValues.containsKey(value)) {
lastUseOfBinopsWithLit8OrLit16NonConstantValues.put(value, currentInstructionNumber);
}
}
}
// Do the transformation except if the binop can use the binop/2addr format.
currentInstructionNumber--;
assert currentInstructionNumber == -1;
while (instructionIterator.hasNext()) {
Instruction currentInstruction = instructionIterator.next();
currentInstructionNumber++;
if (!isBinopWithLit8OrLit16(currentInstruction)) {
continue;
}
Binop binop = currentInstruction.asBinop();
if (!canBe2AddrInstruction(
binop, currentInstructionNumber, lastUseOfBinopsWithLit8OrLit16NonConstantValues)) {
Value constValue = binopWithLit8OrLit16Constant(currentInstruction);
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();
}
// Check if a binop can be represented in the binop/lit8 or binop/lit16 form.
private static boolean isBinopWithLit8OrLit16(Instruction instruction) {
if (!instruction.isArithmeticBinop() && !instruction.isLogicalBinop()) {
return false;
}
Binop binop = instruction.asBinop();
// If one of the values does not need a register it is implicitly a binop/lit8 or binop/lit16.
boolean result =
!binop.needsValueInRegister(binop.leftValue())
|| !binop.needsValueInRegister(binop.rightValue());
assert !result || binop.leftValue().isConstNumber() || binop.rightValue().isConstNumber();
return result;
}
// Return the constant in-value of a binop/lit8 or binop/lit16 instruction.
private static Value binopWithLit8OrLit16Constant(Instruction instruction) {
assert isBinopWithLit8OrLit16(instruction);
Binop binop = instruction.asBinop();
if (binop.leftValue().isConstNumber()) {
return binop.leftValue();
} else if (binop.rightValue().isConstNumber()) {
return binop.rightValue();
} else {
throw new Unreachable();
}
}
// Return the non-constant in-value of a binop/lit8 or binop/lit16 instruction.
private static Value binopWithLit8OrLit16NonConstant(Binop binop) {
if (binop.leftValue().isConstNumber()) {
return binop.rightValue();
} else if (binop.rightValue().isConstNumber()) {
return binop.leftValue();
} else {
throw new Unreachable();
}
}
/**
* Estimate if a binary operation can be a binop/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, int binopInstructionNumber, Reference2IntMap<Value> lastUseOfRelevantValue) {
Value value = binopWithLit8OrLit16NonConstant(binop);
assert value != null;
int lastUseInstructionNumber = lastUseOfRelevantValue.getInt(value);
// The binop instruction is a user, so there is always a last use in the block.
assert lastUseInstructionNumber != -1;
if (lastUseInstructionNumber > binopInstructionNumber) {
return false;
}
Set<BasicBlock> noPathTo = Sets.newIdentityHashSet();
BasicBlock binopBlock = binop.getBlock();
Iterable<InstructionOrPhi> users =
value.debugUsers() != null
? Iterables.concat(value.uniqueUsers(), value.debugUsers(), value.uniquePhiUsers())
: Iterables.concat(value.uniqueUsers(), value.uniquePhiUsers());
for (InstructionOrPhi user : users) {
BasicBlock userBlock = user.getBlock();
if (userBlock == binopBlock) {
// All users in the current block are either before the binop instruction or the
// binop instruction itself.
continue;
}
if (noPathTo.contains(userBlock)) {
continue;
}
if (binopBlock.hasPathTo(userBlock)) {
return false;
}
noPathTo.add(userBlock);
}
return true;
}
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, Map<Value, Instruction>> addConstantInBlock = new IdentityHashMap<>();
LinkedList<BasicBlock> blocks = code.blocks;
for (BasicBlock block : blocks) {
if (block == blocks.getFirst()) {
// For the first block process all ConstNumber as well as ConstString instructions.
shortenLiveRangesInsideBlock(
code,
block,
dominatorTreeMemoization,
addConstantInBlock,
insn ->
(insn.isConstNumber() && insn.outValue().hasAnyUsers())
|| (insn.isConstString() && insn.outValue().hasAnyUsers()));
} 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 moved to the usages.
// Process all blocks in stable order to avoid non-determinism of hash map iterator.
for (BasicBlock block : blocks) {
Map<Value, Instruction> constants = addConstantInBlock.get(block);
if (constants == null) {
continue;
}
Set<Value> alreadyMoved = SetUtils.newIdentityHashSet(constants.size());
if (block != blocks.getFirst() && constants.size() > STOP_SHARED_CONSTANT_THRESHOLD) {
// If there are too many constants in the same block, they are copied rather than shared
// except if they are used by phi instructions or they are a string constants.
assert constants instanceof LinkedHashMap;
for (Instruction constantInstruction : constants.values()) {
if (!constantInstruction.outValue().hasPhiUsers()
&& !constantInstruction.isConstString()) {
assert constantInstruction.isConstNumber();
ConstNumber constNumber = constantInstruction.asConstNumber();
Value constantValue = constantInstruction.outValue();
assert constantValue.hasUsers();
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(code, user);
iterator.previous();
iterator.add(newCstNum);
user.replaceValue(constantValue, newCstNum.outValue());
}
constantValue.clearUsers();
alreadyMoved.add(constantInstruction.outValue());
}
}
}
// Add constant into the dominator block of usages.
boolean hasCatchHandlers = block.hasCatchHandlers();
InstructionListIterator it = block.listIterator(code);
while (it.hasNext()) {
Instruction instruction = it.next();
if (instruction.isJumpInstruction()
|| (hasCatchHandlers && instruction.instructionTypeCanThrow())
|| (options.canHaveCmpIfFloatBug() && instruction.isCmp())) {
break;
}
forEachUse(
instruction,
use -> {
Instruction constantInstruction = constants.get(use);
if (constantInstruction != null && !alreadyMoved.contains(use)) {
it.previous();
constantInstruction.setPosition(instruction.getPosition());
it.add(constantInstruction);
it.next();
alreadyMoved.add(use);
}
});
}
// Insert remaining constant instructions prior to the "exit".
Instruction next = it.previous();
for (Instruction constantInstruction : constants.values()) {
if (!alreadyMoved.contains(constantInstruction.outValue())) {
constantInstruction.setPosition(next.getPosition());
it.add(constantInstruction);
}
}
}
assert code.isConsistentSSA();
}
private void forEachUse(Instruction instruction, Consumer<Value> fn) {
instruction.inValues().forEach(fn);
instruction.getDebugValues().forEach(fn);
}
private void shortenLiveRangesInsideBlock(
IRCode code,
BasicBlock block,
Supplier<DominatorTree> dominatorTreeMemoization,
Map<BasicBlock, Map<Value, Instruction>> addConstantInBlock,
Predicate<ConstInstruction> selector) {
InstructionListIterator iterator = block.listIterator(code);
while (iterator.hasNext()) {
Instruction next = iterator.next();
if (!next.isConstInstruction()) {
continue;
}
// We don't want to push const string instructions down into code that has monitors since
// we may attach catch handlers that are not catch-all when inlining. This is symmetric in how
// we don't do const string canonicalization.
if ((next.isConstString() || next.isDexItemBasedConstString())
&& code.metadata().mayHaveMonitorInstruction()) {
continue;
}
ConstInstruction instruction = next.asConstInstruction();
if (!selector.test(instruction) || instruction.outValue().hasLocalInfo()) {
continue;
}
Set<Instruction> uniqueUsers = instruction.outValue().uniqueUsers();
// Here we try to stop wasting time in the common case of large array of constants creation.
// We do not want to move a high number of constants up just to move them down because it
// takes multiple seconds in some cases (ZoneName clinit for instance).
// In array creation, the pattern is something like:
// Const number (the array index)
// Const (the array entry value)
// ArrayPut
// And both constants are used only in the put. The heuristic is therefore to check for
// constants used only once if the use is within the next two instructions, and only swap
// them if that is the case (cannot shorten the live range anyway).
// This heuristic drops down the time spent in large array of constant creation in
// shortenLiveRanges from multiple seconds to multiple milliseconds.
if (uniqueUsers.size() == 1 && instruction.outValue().uniquePhiUsers().size() == 0) {
Instruction uniqueUse = uniqueUsers.iterator().next();
if (iterator.hasNext()) {
Instruction nextNext = iterator.next();
if (uniqueUse == nextNext && nextNext.isArrayPut()) {
assert !uniqueUse.isConstInstruction();
continue;
}
if (nextNext.isConstInstruction()) {
Set<Instruction> uniqueUsersNext = nextNext.outValue().uniqueUsers();
if (uniqueUsersNext.size() == 1
&& nextNext.outValue().uniquePhiUsers().size() == 0
&& iterator.hasNext()) {
Instruction nextNextNext = iterator.peekNext();
Instruction uniqueUseNext = uniqueUsersNext.iterator().next();
if (uniqueUse == nextNextNext
&& uniqueUseNext == nextNextNext
&& nextNextNext.isArrayPut()) {
continue;
}
}
}
iterator.previous();
}
}
// Collect the blocks for all users of the constant.
List<BasicBlock> userBlocks = new LinkedList<>();
for (Instruction user : 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;
}
}
Map<Value, Instruction> csts =
addConstantInBlock.computeIfAbsent(dominator, k -> new LinkedHashMap<>());
ConstInstruction copy = instruction.isConstNumber()
? ConstNumber.copyOf(code, instruction.asConstNumber())
: ConstString.copyOf(code, instruction.asConstString());
instruction.outValue().replaceUsers(copy.outValue());
csts.put(copy.outValue(), copy);
}
}
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.
InstructionIterator it = block.iterator();
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.iterator() : 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(code);
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.getOutType(), 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(code);
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);
}
}
assert code.isConsistentSSA();
}
// 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;
}
Position position = null;
for (Instruction instruction : from.getBlock().instructionsAfter(from)) {
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) {
InstructionListIterator iterator = block.listIterator(code);
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) {
overwrittenLocal.addDebugLocalEnd(inValue.definition);
}
if (prevInstruction != null &&
(prevInstruction.outValue() == null
|| !prevInstruction.outValue().hasLocalInfo()
|| !instruction.getDebugValues().contains(prevInstruction.outValue()))) {
instruction.moveDebugValues(prevInstruction);
}
iterator.removeOrReplaceByDebugLocalRead();
}
}
}
}
}
private static class CSEExpressionEquivalence extends Equivalence<Instruction> {
private final InternalOptions options;
private CSEExpressionEquivalence(InternalOptions options) {
this.options = options;
}
@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() && 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) {
for (Instruction instruction : block.getInstructions()) {
if (isCSEInstructionCandidate(instruction)) {
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(options);
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(code);
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);
candidate.uniquePhiUsers().forEach(Phi::removeTrivialPhi);
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();
}
static class ControlFlowSimplificationResult {
private boolean anyAffectedValues;
private boolean anySimplifications;
private ControlFlowSimplificationResult(boolean anyAffectedValues, boolean anySimplifications) {
assert !anyAffectedValues || anySimplifications;
this.anyAffectedValues = anyAffectedValues;
this.anySimplifications = anySimplifications;
}
public boolean anyAffectedValues() {
return anyAffectedValues;
}
public boolean anySimplifications() {
return anySimplifications;
}
}
public boolean simplifyControlFlow(IRCode code) {
boolean anyAffectedValues = rewriteSwitch(code);
anyAffectedValues |= simplifyIf(code).anyAffectedValues();
return anyAffectedValues;
}
public ControlFlowSimplificationResult simplifyIf(IRCode code) {
BasicBlockBehavioralSubsumption behavioralSubsumption =
new BasicBlockBehavioralSubsumption(appView, code);
boolean simplified = false;
for (BasicBlock block : code.blocks) {
// Skip removed (= unreachable) blocks.
if (block.getNumber() != 0 && block.getPredecessors().isEmpty()) {
continue;
}
if (block.exit().isIf()) {
flipIfBranchesIfNeeded(code, block);
if (rewriteIfWithConstZero(code, block)) {
simplified = true;
}
if (simplifyKnownBooleanCondition(code, block)) {
simplified = true;
if (!block.exit().isIf()) {
continue;
}
}
// Simplify if conditions when possible.
If theIf = block.exit().asIf();
if (theIf.isZeroTest()) {
if (simplifyIfZeroTest(code, block, theIf)) {
simplified = true;
continue;
}
} else {
if (simplifyNonIfZeroTest(code, block, theIf)) {
simplified = true;
continue;
}
}
// Unable to determine which branch will be taken. Check if the true target can safely be
// rewritten to the false target.
if (behavioralSubsumption.isSubsumedBy(theIf.getTrueTarget(), theIf.fallthroughBlock())) {
simplifyIfWithKnownCondition(code, block, theIf, theIf.fallthroughBlock());
simplified = true;
}
}
}
Set<Value> affectedValues = code.removeUnreachableBlocks();
if (!affectedValues.isEmpty()) {
new TypeAnalysis(appView).narrowing(affectedValues);
}
assert code.isConsistentSSA();
return new ControlFlowSimplificationResult(!affectedValues.isEmpty(), simplified);
}
private boolean simplifyIfZeroTest(IRCode code, BasicBlock block, If theIf) {
Value lhs = theIf.lhs();
Value lhsRoot = lhs.getAliasedValue();
if (lhsRoot.isConstNumber()) {
ConstNumber cond = lhsRoot.getConstInstruction().asConstNumber();
BasicBlock target = theIf.targetFromCondition(cond);
simplifyIfWithKnownCondition(code, block, theIf, target);
return true;
}
if (theIf.isNullTest()) {
assert theIf.getType() == Type.EQ || theIf.getType() == Type.NE;
if (lhs.isAlwaysNull(appView)) {
simplifyIfWithKnownCondition(code, block, theIf, theIf.targetFromNullObject());
return true;
}
if (lhs.isNeverNull()) {
simplifyIfWithKnownCondition(code, block, theIf, theIf.targetFromNonNullObject());
return true;
}
}
if (theIf.getType() == Type.EQ || theIf.getType() == Type.NE) {
AbstractValue lhsAbstractValue = lhs.getAbstractValue(appView, code.context());
if (lhsAbstractValue.isConstantOrNonConstantNumberValue()
&& !lhsAbstractValue.asConstantOrNonConstantNumberValue().containsInt(0)) {
// Value doesn't contain zero at all.
simplifyIfWithKnownCondition(code, block, theIf, theIf.targetFromCondition(1));
return true;
}
}
if (lhs.hasValueRange()) {
LongInterval interval = lhs.getValueRange();
if (!interval.containsValue(0)) {
// Interval doesn't contain zero at all.
int sign = Long.signum(interval.getMin());
simplifyIfWithKnownCondition(code, block, theIf, sign);
return true;
}
// 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);
return true;
}
break;
case LE:
case GT:
// [a, b] <= 0 is always true if b <= 0.
// [a, b] > 0 is always false if b <= 0.
// In both cases a zero condition takes the right branch.
if (interval.getMax() == 0) {
simplifyIfWithKnownCondition(code, block, theIf, 0);
return true;
}
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;
}
}
return false;
}
private boolean simplifyNonIfZeroTest(IRCode code, BasicBlock block, If theIf) {
Value lhs = theIf.lhs();
Value lhsRoot = lhs.getAliasedValue();
Value rhs = theIf.rhs();
Value rhsRoot = rhs.getAliasedValue();
if (lhsRoot == rhsRoot) {
// Comparing the same value.
simplifyIfWithKnownCondition(code, block, theIf, theIf.targetFromCondition(0));
return true;
}
if (lhsRoot.isDefinedByInstructionSatisfying(Instruction::isCreatingInstanceOrArray)
&& rhsRoot.isDefinedByInstructionSatisfying(Instruction::isCreatingInstanceOrArray)) {
// Comparing two newly created objects.
assert theIf.getType() == Type.EQ || theIf.getType() == Type.NE;
simplifyIfWithKnownCondition(code, block, theIf, theIf.targetFromCondition(1));
return true;
}
if (lhsRoot.isConstNumber() && rhsRoot.isConstNumber()) {
// Zero test with a constant of comparison between between two constants.
ConstNumber left = lhsRoot.getConstInstruction().asConstNumber();
ConstNumber right = rhsRoot.getConstInstruction().asConstNumber();
BasicBlock target = theIf.targetFromCondition(left, right);
simplifyIfWithKnownCondition(code, block, theIf, target);
return true;
}
if (theIf.getType() == Type.EQ || theIf.getType() == Type.NE) {
AbstractValue lhsAbstractValue = lhs.getAbstractValue(appView, code.context());
AbstractValue rhsAbstractValue = rhs.getAbstractValue(appView, code.context());
if (lhsAbstractValue.isConstantOrNonConstantNumberValue()
&& rhsAbstractValue.isConstantOrNonConstantNumberValue()) {
ConstantOrNonConstantNumberValue lhsNumberValue =
lhsAbstractValue.asConstantOrNonConstantNumberValue();
ConstantOrNonConstantNumberValue rhsNumberValue =
rhsAbstractValue.asConstantOrNonConstantNumberValue();
if (!lhsNumberValue.mayOverlapWith(rhsNumberValue)) {
// No overlap.
simplifyIfWithKnownCondition(code, block, theIf, 1);
return true;
}
}
}
if (lhs.hasValueRange() && rhs.hasValueRange()) {
// Zero test with a value range, or comparison between between two values,
// each with a value ranges.
LongInterval leftRange = lhs.getValueRange();
LongInterval rightRange = rhs.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);
return true;
}
// 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);
return true;
}
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);
return true;
}
break;
case EQ:
case NE:
// Since there is overlap EQ and NE cannot be determined.
break;
}
}
if (theIf.getType() == Type.EQ || theIf.getType() == Type.NE) {
ProgramMethod context = code.context();
AbstractValue abstractValue = lhs.getAbstractValue(appView, context);
if (abstractValue.isSingleConstClassValue()) {
AbstractValue otherAbstractValue = rhs.getAbstractValue(appView, context);
if (otherAbstractValue.isSingleConstClassValue()) {
SingleConstClassValue singleConstClassValue = abstractValue.asSingleConstClassValue();
SingleConstClassValue otherSingleConstClassValue =
otherAbstractValue.asSingleConstClassValue();
simplifyIfWithKnownCondition(
code,
block,
theIf,
BooleanUtils.intValue(
singleConstClassValue.getType() != otherSingleConstClassValue.getType()));
return true;
}
return false;
}
if (abstractValue.isSingleFieldValue()) {
AbstractValue otherAbstractValue = rhs.getAbstractValue(appView, context);
if (otherAbstractValue.isSingleFieldValue()) {
SingleFieldValue singleFieldValue = abstractValue.asSingleFieldValue();
SingleFieldValue otherSingleFieldValue = otherAbstractValue.asSingleFieldValue();
if (singleFieldValue.getField() == otherSingleFieldValue.getField()) {
simplifyIfWithKnownCondition(code, block, theIf, 0);
return true;
}
DexClass holder = appView.definitionForHolder(singleFieldValue.getField());
DexEncodedField field = singleFieldValue.getField().lookupOnClass(holder);
if (field != null && field.isEnum()) {
DexClass otherHolder = appView.definitionForHolder(otherSingleFieldValue.getField());
DexEncodedField otherField =
otherSingleFieldValue.getField().lookupOnClass(otherHolder);
if (otherField != null && otherField.isEnum()) {
simplifyIfWithKnownCondition(code, block, theIf, 1);
return true;
}
}
}
}
}
return false;
}
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) {
if (appView.options().canHaveDalvikIntUsedAsNonIntPrimitiveTypeBug()
&& !appView.options().testing.forceRedundantConstNumberRemoval) {
// See also b/124152497.
return;
}
if (!code.metadata().mayHaveConstNumber()) {
return;
}
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, code, dominatorTree);
if (lhs.knownToBeBoolean()) {
changed |=
replaceDominatedConstNumbers(
1, lhs, falseTarget, constantsByValue, code, dominatorTree);
}
} else {
assert rhs != null;
if (lhs.isConstNumber()) {
ConstNumber lhsAsNumber = lhs.getConstInstruction().asConstNumber();
changed |=
replaceDominatedConstNumbers(
lhsAsNumber.getRawValue(),
rhs,
trueTarget,
constantsByValue,
code,
dominatorTree);
if (lhs.knownToBeBoolean() && rhs.knownToBeBoolean()) {
changed |=
replaceDominatedConstNumbers(
negateBoolean(lhsAsNumber),
rhs,
falseTarget,
constantsByValue,
code,
dominatorTree);
}
} else {
assert rhs.isConstNumber();
ConstNumber rhsAsNumber = rhs.getConstInstruction().asConstNumber();
changed |=
replaceDominatedConstNumbers(
rhsAsNumber.getRawValue(),
lhs,
trueTarget,
constantsByValue,
code,
dominatorTree);
if (lhs.knownToBeBoolean() && rhs.knownToBeBoolean()) {
changed |=
replaceDominatedConstNumbers(
negateBoolean(rhsAsNumber),
lhs,
falseTarget,
constantsByValue,
code,
dominatorTree);
}
}
}
if (constantsByValue.get().isEmpty()) {
break;
}
}
if (changed) {
code.removeAllDeadAndTrivialPhis();
}
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`.
for (Instruction instruction : code.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,
IRCode code,
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.getType().lessThanOrEqual(value.getType(), appView)) {
value.replaceUsers(newValue);
block.listIterator(code, constNumber).removeOrReplaceByDebugLocalRead();
constantWithValueIterator.remove();
changed = true;
} else if (value.getType().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 instructions that always throw, split the block after each such 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 optimizeAlwaysThrowingInstructions(IRCode code) {
if (!appView.appInfo().hasLiveness()) {
return;
}
AppView<AppInfoWithLiveness> appViewWithLiveness = appView.withLiveness();
Set<Value> affectedValues = Sets.newIdentityHashSet();
Set<BasicBlock> blocksToRemove = Sets.newIdentityHashSet();
ListIterator<BasicBlock> blockIterator = code.listIterator();
ProgramMethod context = code.context();
while (blockIterator.hasNext()) {
BasicBlock block = blockIterator.next();
if (block.getNumber() != 0 && block.getPredecessors().isEmpty()) {
continue;
}
if (blocksToRemove.contains(block)) {
continue;
}
InstructionListIterator instructionIterator = block.listIterator(code);
while (instructionIterator.hasNext()) {
Instruction instruction = instructionIterator.next();
if (instruction.throwsOnNullInput()) {
Value inValue = instruction.getNonNullInput();
if (inValue.isAlwaysNull(appView)) {
// Insert `throw null` after the instruction if it is not guaranteed to throw an NPE.
if (instruction.isInstanceFieldInstruction()) {
InstanceFieldInstruction instanceFieldInstruction =
instruction.asInstanceFieldInstruction();
if (instanceFieldInstruction.instructionInstanceCanThrow(
appView, context, SideEffectAssumption.RECEIVER_NOT_NULL)) {
instructionIterator.next();
}
} else if (instruction.isInvokeMethodWithReceiver()) {
InvokeMethodWithReceiver invoke = instruction.asInvokeMethodWithReceiver();
SideEffectAssumption assumption =
SideEffectAssumption.RECEIVER_NOT_NULL.join(
SideEffectAssumption.INVOKED_METHOD_DOES_NOT_HAVE_SIDE_EFFECTS);
if (invoke.instructionMayHaveSideEffects(appView, context, assumption)) {
instructionIterator.next();
}
}
instructionIterator.replaceCurrentInstructionWithThrowNull(
appViewWithLiveness, code, blockIterator, blocksToRemove, affectedValues);
continue;
}
}
if (!instruction.isInvokeMethod()) {
continue;
}
InvokeMethod invoke = instruction.asInvokeMethod();
DexClassAndMethod singleTarget =
invoke.lookupSingleTarget(appView.withLiveness(), code.context());
if (singleTarget == null) {
continue;
}
MethodOptimizationInfo optimizationInfo =
singleTarget.getDefinition().getOptimizationInfo();
// If the invoke instruction is a null check, we can remove it.
boolean isNullCheck = false;
if (optimizationInfo.hasNonNullParamOrThrow()) {
BitSet nonNullParamOrThrow = optimizationInfo.getNonNullParamOrThrow();
for (int i = 0; i < invoke.arguments().size(); i++) {
Value argument = invoke.arguments().get(i);
if (argument.isAlwaysNull(appView) && nonNullParamOrThrow.get(i)) {
isNullCheck = true;
break;
}
}
}
// If the invoke instruction never returns normally, we can insert a throw null instruction
// after the invoke.
if (isNullCheck || optimizationInfo.neverReturnsNormally()) {
instructionIterator.setInsertionPosition(invoke.getPosition());
instructionIterator.next();
instructionIterator.replaceCurrentInstructionWithThrowNull(
appViewWithLiveness, code, blockIterator, blocksToRemove, affectedValues);
instructionIterator.unsetInsertionPosition();
}
}
}
code.removeBlocks(blocksToRemove);
assert code.getUnreachableBlocks().isEmpty();
if (!affectedValues.isEmpty()) {
new TypeAnalysis(appView).narrowing(affectedValues);
}
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.getType(), 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.listIterator(code, insertIndex).add(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 deadPhis > 0;
}
}
}
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);
InstructionIterator it = predecessorBlock.iterator(predecessorBlock.exit());
Instruction previousPosition = null;
while (it.hasPrevious() && !(previousPosition = it.previous()).isDebugPosition()) {
// Intentionally empty.
}
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(), code);
assert block.exit().isGoto();
assert block.exit().asGoto().getTarget() == target;
}
private void rewriteIfToRequireNonNull(
BasicBlock block,
InstructionListIterator iterator,
If theIf,
BasicBlock target,
BasicBlock deadTarget,
Value message,
Position position) {
deadTarget.unlinkSinglePredecessorSiblingsAllowed();
assert theIf == block.exit();
iterator.previous();
Instruction instruction;
if (appView.options().canUseJavaUtilObjectsRequireNonNull()) {
if (message != null) {
DexMethod requireNonNullMethod =
appView.dexItemFactory().objectsMethods.requireNonNullWithMessage;
instruction =
new InvokeStatic(requireNonNullMethod, null, ImmutableList.of(theIf.lhs(), message));
} else {
DexMethod requireNonNullMethod = appView.dexItemFactory().objectsMethods.requireNonNull;
instruction = new InvokeStatic(requireNonNullMethod, null, ImmutableList.of(theIf.lhs()));
}
} else {
assert message == null;
DexMethod getClassMethod = appView.dexItemFactory().objectMembers.getClass;
instruction = new InvokeVirtual(getClassMethod, null, ImmutableList.of(theIf.lhs()));
}
instruction.setPosition(position);
iterator.add(instruction);
iterator.next();
iterator.replaceCurrentInstruction(new Goto());
assert block.exit().isGoto();
assert block.exit().asGoto().getTarget() == target;
}
private boolean rewriteIfWithConstZero(IRCode code, BasicBlock block) {
If theIf = block.exit().asIf();
if (theIf.isZeroTest()) {
return false;
}
Value leftValue = theIf.lhs();
Value rightValue = theIf.rhs();
if (leftValue.isConstNumber() || rightValue.isConstNumber()) {
if (leftValue.isConstNumber()) {
if (leftValue.getConstInstruction().asConstNumber().isZero()) {
If ifz = new If(theIf.getType().forSwappedOperands(), rightValue);
block.replaceLastInstruction(ifz, code);
assert block.exit() == ifz;
return true;
}
} else if (rightValue.getConstInstruction().asConstNumber().isZero()) {
If ifz = new If(theIf.getType(), leftValue);
block.replaceLastInstruction(ifz, code);
assert block.exit() == ifz;
return true;
}
}
return false;
}
private boolean flipIfBranchesIfNeeded(IRCode code, 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, code);
block.swapSuccessors(trueTarget, fallthrough);
return true;
}
public void rewriteKnownArrayLengthCalls(IRCode code) {
InstructionListIterator iterator = code.instructionListIterator();
while (iterator.hasNext()) {
Instruction current = iterator.next();
if (!current.isArrayLength()) {
continue;
}
ArrayLength arrayLength = current.asArrayLength();
if (arrayLength.hasOutValue() && arrayLength.outValue().hasLocalInfo()) {
continue;
}
Value array = arrayLength.array().getAliasedValue();
if (array.isPhi() || !array.isNeverNull() || array.hasLocalInfo()) {
continue;
}
Instruction arrayDefinition = array.getDefinition();
assert arrayDefinition != null;
Set<Phi> phiUsers = arrayLength.outValue().uniquePhiUsers();
if (arrayDefinition.isNewArrayEmpty()) {
Value size = arrayDefinition.asNewArrayEmpty().size();
arrayLength.outValue().replaceUsers(size);
iterator.removeOrReplaceByDebugLocalRead();
} else if (arrayDefinition.isNewArrayFilledData()) {
int size = (int) arrayDefinition.asNewArrayFilledData().size;
ConstNumber constSize = code.createIntConstant(size);
iterator.replaceCurrentInstruction(constSize);
} else {
continue;
}
phiUsers.forEach(Phi::removeTrivialPhi);
// TODO(139489070): static-get of constant array
}
assert code.isConsistentSSA();
}
public void rewriteAssertionErrorTwoArgumentConstructor(IRCode code, InternalOptions options) {
if (options.canUseAssertionErrorTwoArgumentConstructor()) {
return;
}
ListIterator<BasicBlock> blockIterator = code.listIterator();
while (blockIterator.hasNext()) {
BasicBlock block = blockIterator.next();
InstructionListIterator insnIterator = block.listIterator(code);
while (insnIterator.hasNext()) {
Instruction current = insnIterator.next();
if (current.isInvokeMethod()) {
DexMethod invokedMethod = current.asInvokeMethod().getInvokedMethod();
if (invokedMethod == dexItemFactory.assertionErrorMethods.initMessageAndCause) {
// Rewrite calls to new AssertionError(message, cause) to new AssertionError(message)
// and then initCause(cause).
List<Value> inValues = current.inValues();
assert inValues.size() == 3; // receiver, message, cause
// Remove cause from the constructor call
List<Value> newInitInValues = inValues.subList(0, 2);
insnIterator.replaceCurrentInstruction(
new InvokeDirect(
dexItemFactory.assertionErrorMethods.initMessage, null, newInitInValues));
// On API 15 and older we cannot use initCause because of a bug in AssertionError.
if (options.canInitCauseAfterAssertionErrorObjectConstructor()) {
// Add a call to Throwable.initCause(cause)
if (block.hasCatchHandlers()) {
insnIterator = insnIterator.split(code, blockIterator).listIterator(code);
}
List<Value> initCauseArguments = Arrays.asList(inValues.get(0), inValues.get(2));
InvokeVirtual initCause =
new InvokeVirtual(
dexItemFactory.throwableMethods.initCause,
code.createValue(
TypeElement.fromDexType(
dexItemFactory.throwableType, maybeNull(), appView)),
initCauseArguments);
initCause.setPosition(current.getPosition());
insnIterator.add(initCause);
}
}
}
}
}
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 (!allocator.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();
InstructionListIterator it = block.listIterator(code);
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.removeInstructionIgnoreOutValue();
}
} 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;
InstructionIterator it = block.iterator(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(code);
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 = appView.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) {
TypeElement typeLattice = TypeElement.stringClassType(appView, definitelyNotNull());
Value value = code.createValue(typeLattice);
iterator.add(new ConstString(value, dexItemFactory.createString(s)));
return value;
}
/**
* Insert code into <code>method</code> to log the argument types to System.out.
*
* The type is determined by calling getClass() on the argument.
*/
public void logArgumentTypes(DexEncodedMethod method, IRCode code) {
List<Value> arguments = code.collectArguments();
BasicBlock block = code.entryBlock();
InstructionListIterator iterator = block.listIterator(code);
// Attach some synthetic position to all inserted code.
Position position = Position.synthetic(1, method.getReference(), 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.javaLangSystemType;
DexType javaIoPrintStreamType = dexItemFactory.javaIoPrintStreamType;
Value out =
code.createValue(
TypeElement.fromDexType(javaIoPrintStreamType, definitelyNotNull(), appView));
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.getReference().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.getNextBlockNumber(), position, code.metadata());
code.blocks.add(eol);
BasicBlock successor = block.unlinkSingleSuccessor();
block.link(eol);
eol.link(successor);
Value argument = arguments.get(i);
if (!argument.getType().isReferenceType()) {
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.getNextBlockNumber(), theIf, code.metadata());
code.blocks.add(ifBlock);
// Fallthrough block must be added right after the if.
BasicBlock isNullBlock =
BasicBlock.createGotoBlock(code.getNextBlockNumber(), position, code.metadata());
code.blocks.add(isNullBlock);
BasicBlock isNotNullBlock =
BasicBlock.createGotoBlock(code.getNextBlockNumber(), position, code.metadata());
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(code);
iterator.setInsertionPosition(position);
iterator.add(new InvokeVirtual(print, null, ImmutableList.of(out, nul)));
iterator = isNotNullBlock.listIterator(code);
iterator.setInsertionPosition(position);
value = code.createValue(TypeElement.classClassType(appView, definitelyNotNull()));
iterator.add(
new InvokeVirtual(
dexItemFactory.objectMembers.getClass, value, ImmutableList.of(arguments.get(i))));
iterator.add(new InvokeVirtual(print, null, ImmutableList.of(out, value)));
}
iterator = eol.listIterator(code);
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 dexItemFactory) {
for (Instruction instruction : code.instructions()) {
if (instruction.isInvokeDirect()) {
InvokeDirect invoke = instruction.asInvokeDirect();
DexMethod method = invoke.getInvokedMethod();
if (dexItemFactory.isConstructor(method)
&& method.holder == dexItemFactory.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 = Sets.newIdentityHashSet();
Set<Value> values = Sets.newIdentityHashSet();
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<Value>(Value::uniquePhiUsers).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 = Sets.newIdentityHashSet();
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);
}
}
}
// See comment for InternalOptions.canHaveNumberConversionRegisterAllocationBug().
public void workaroundNumberConversionRegisterAllocationBug(IRCode code) {
ListIterator<BasicBlock> blocks = code.listIterator();
while (blocks.hasNext()) {
BasicBlock block = blocks.next();
InstructionListIterator it = block.listIterator(code);
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(
dexItemFactory.doubleMembers.isNaN, 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(code, block.getInstructions().size());
it.previous();
it.add(invokeIsNaN);
// Continue iteration in the split block.
block = blockWithInvokeNaN;
it = block.listIterator(code);
} 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 != null
&& target.getPredecessors().size() > 1
&& target.getNormalPredecessors().size() > 1
&& target.getNormalSuccessors().size() > 1) {
Instruction fixit = new AlwaysMaterializingNop();
fixit.setBlock(handler);
fixit.setPosition(handler.getPosition());
handler.getInstructions().addFirst(fixit);
}
}
}
}
}
}