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// Copyright (c) 2016, the R8 project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
package com.android.tools.r8.ir.code;
import com.android.tools.r8.cf.LoadStoreHelper;
import com.android.tools.r8.cf.TypeVerificationHelper;
import com.android.tools.r8.cf.code.CfCheckCast;
import com.android.tools.r8.code.MoveObject;
import com.android.tools.r8.code.MoveObjectFrom16;
import com.android.tools.r8.dex.Constants;
import com.android.tools.r8.graph.AppInfo;
import com.android.tools.r8.graph.AppView;
import com.android.tools.r8.graph.DexType;
import com.android.tools.r8.ir.analysis.type.TypeLatticeElement;
import com.android.tools.r8.ir.conversion.CfBuilder;
import com.android.tools.r8.ir.conversion.DexBuilder;
import com.android.tools.r8.ir.optimize.Inliner.ConstraintWithTarget;
import com.android.tools.r8.ir.optimize.InliningConstraints;
public class CheckCast extends Instruction {
private final DexType type;
// A CheckCast dex instruction takes only one register containing a value and changes
// the associated type information for that value. In the IR we let the CheckCast
// instruction define a new value. During register allocation we then need to arrange it
// so that the source and destination are assigned the same register.
public CheckCast(Value dest, Value value, DexType type) {
super(dest, value);
this.type = type;
}
@Override
public <T> T accept(InstructionVisitor<T> visitor) {
return visitor.visit(this);
}
public DexType getType() {
return type;
}
public Value object() {
return inValues().get(0);
}
@Override
public void buildDex(DexBuilder builder) {
// The check cast instruction in dex doesn't write a new register. Therefore,
// if the register allocator could not put input and output in the same register
// we have to insert a move before the check cast instruction.
int inRegister = builder.allocatedRegister(inValues.get(0), getNumber());
if (outValue == null) {
builder.add(this, new com.android.tools.r8.code.CheckCast(inRegister, type));
} else {
int outRegister = builder.allocatedRegister(outValue, getNumber());
if (inRegister == outRegister) {
builder.add(this, new com.android.tools.r8.code.CheckCast(outRegister, type));
} else {
com.android.tools.r8.code.CheckCast cast =
new com.android.tools.r8.code.CheckCast(outRegister, type);
if (outRegister <= Constants.U4BIT_MAX && inRegister <= Constants.U4BIT_MAX) {
builder.add(this, new MoveObject(outRegister, inRegister), cast);
} else {
builder.add(this, new MoveObjectFrom16(outRegister, inRegister), cast);
}
}
}
}
@Override
public boolean identicalNonValueNonPositionParts(Instruction other) {
return other.isCheckCast() && other.asCheckCast().type == type;
}
@Override
public int maxInValueRegister() {
return Constants.U8BIT_MAX;
}
@Override
public int maxOutValueRegister() {
return Constants.U8BIT_MAX;
}
@Override
public boolean instructionTypeCanThrow() {
return true;
}
@Override
public boolean isCheckCast() {
return true;
}
@Override
public CheckCast asCheckCast() {
return this;
}
@Override
public String toString() {
return super.toString() + "; " + type;
}
@Override
public ConstraintWithTarget inliningConstraint(
InliningConstraints inliningConstraints, DexType invocationContext) {
return inliningConstraints.forCheckCast(type, invocationContext);
}
@Override
public TypeLatticeElement evaluate(AppView<? extends AppInfo> appView) {
return object().getTypeLattice().checkCast(appView, type);
}
@Override
public boolean verifyTypes(AppView<? extends AppInfo> appView) {
assert super.verifyTypes(appView);
TypeLatticeElement inType = object().getTypeLattice();
assert inType.isPreciseType();
TypeLatticeElement outType = outValue().getTypeLattice();
TypeLatticeElement castType =
TypeLatticeElement.fromDexType(getType(), inType.nullability(), appView);
if (inType.lessThanOrEqual(castType, appView)) {
// Cast can be removed. Check that it is sound to replace all users of the out-value by the
// in-value.
assert inType.lessThanOrEqual(outType, appView);
// TODO(b/72693244): Consider checking equivalence. This requires that the types are always
// as precise as possible, though, meaning that almost all changes to the IR must be followed
// by a fix-point analysis.
// assert outType.equals(inType);
} else {
// We don't have enough information to remove the cast. Check that the out-value does not
// have a more precise type than the cast-type.
assert outType.equalUpToNullability(castType);
// Check soundness of null information.
assert inType.nullability().lessThanOrEqual(outType.nullability());
// Since we cannot remove the cast the in-value must be different from null.
assert !inType.isNullType();
// TODO(b/72693244): Consider checking equivalence. This requires that the types are always
// as precise as possible, though, meaning that almost all changes to the IR must be followed
// by a fix-point analysis.
// assert outType.equals(castType);
}
return true;
}
@Override
public void insertLoadAndStores(InstructionListIterator it, LoadStoreHelper helper) {
helper.loadInValues(this, it);
helper.storeOutValue(this, it);
}
@Override
public boolean hasInvariantOutType() {
// Nullability of in-value can be refined.
return false;
}
@Override
public DexType computeVerificationType(
AppView<? extends AppInfo> appView, TypeVerificationHelper helper) {
return type;
}
@Override
public void buildCf(CfBuilder builder) {
builder.add(new CfCheckCast(type));
}
}