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The GraalVM compiler and the Graal-truffle optimizer.
/*
* Copyright (c) 2011, 2024, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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package jdk.graal.compiler.nodes.calc;
import jdk.graal.compiler.core.common.type.ArithmeticOpTable;
import jdk.graal.compiler.core.common.type.ArithmeticOpTable.ShiftOp;
import jdk.graal.compiler.core.common.type.ArithmeticOpTable.ShiftOp.UShr;
import jdk.graal.compiler.core.common.type.IntegerStamp;
import jdk.graal.compiler.core.common.type.PrimitiveStamp;
import jdk.graal.compiler.core.common.type.Stamp;
import jdk.graal.compiler.debug.Assertions;
import jdk.graal.compiler.graph.NodeClass;
import jdk.graal.compiler.lir.gen.ArithmeticLIRGeneratorTool;
import jdk.graal.compiler.nodeinfo.NodeInfo;
import jdk.graal.compiler.nodes.ConstantNode;
import jdk.graal.compiler.nodes.NodeView;
import jdk.graal.compiler.nodes.ValueNode;
import jdk.graal.compiler.nodes.spi.CanonicalizerTool;
import jdk.graal.compiler.nodes.spi.NodeLIRBuilderTool;
import jdk.vm.ci.code.CodeUtil;
import jdk.vm.ci.meta.JavaKind;
@NodeInfo(shortName = ">>>")
public final class UnsignedRightShiftNode extends ShiftNode {
public static final NodeClass TYPE = NodeClass.create(UnsignedRightShiftNode.class);
public UnsignedRightShiftNode(ValueNode x, ValueNode y) {
super(TYPE, BinaryArithmeticNode.getArithmeticOpTable(x).getUShr(), x, y);
}
public static ValueNode create(ValueNode x, ValueNode y, NodeView view) {
ArithmeticOpTable.ShiftOp op = ArithmeticOpTable.forStamp(x.stamp(view)).getUShr();
Stamp stamp = op.foldStamp(x.stamp(view), (IntegerStamp) y.stamp(view));
ValueNode value = ShiftNode.canonical(op, stamp, x, y, view);
if (value != null) {
return value;
}
return canonical(null, op, stamp, x, y, view);
}
@Override
protected ShiftOp getOp(ArithmeticOpTable table) {
return table.getUShr();
}
@Override
public ValueNode canonical(CanonicalizerTool tool, ValueNode forX, ValueNode forY) {
NodeView view = NodeView.from(tool);
ValueNode ret = super.canonical(tool, forX, forY);
if (ret != this) {
return ret;
}
return canonical(this, this.getArithmeticOp(), this.stamp(view), forX, forY, view);
}
@SuppressWarnings("unused")
private static ValueNode canonical(UnsignedRightShiftNode node, ArithmeticOpTable.ShiftOp op, Stamp stamp, ValueNode forX, ValueNode forY, NodeView view) {
if (forY.isConstant()) {
int amount = forY.asJavaConstant().asInt();
int originalAmout = amount;
int mask = op.getShiftAmountMask(stamp);
amount &= mask;
if (amount == 0) {
return forX;
}
Stamp xStampGeneric = forX.stamp(view);
if (xStampGeneric instanceof IntegerStamp) {
IntegerStamp xStamp = (IntegerStamp) xStampGeneric;
long xMask = CodeUtil.mask(xStamp.getBits());
long xLowerBound = xStamp.lowerBound() & xMask;
long xUpperBound = xStamp.upperBound() & xMask;
if (xLowerBound >>> amount == xUpperBound >>> amount) {
// The result of the shift is constant.
return ConstantNode.forIntegerBits(PrimitiveStamp.getBits(stamp), xLowerBound >>> amount);
}
if (amount == xStamp.getBits() - 1 && xStamp.lowerBound() == -1 && xStamp.upperBound() == 0) {
// Shift is equivalent to a negation, i.e., turns -1 into 1 and keeps 0 at 0.
return NegateNode.create(forX, view);
}
}
if (forX instanceof ShiftNode) {
ShiftNode other = (ShiftNode) forX;
if (other.getY().isConstant()) {
int otherAmount = other.getY().asJavaConstant().asInt() & mask;
if (other instanceof UnsignedRightShiftNode) {
int total = amount + otherAmount;
if (total != (total & mask)) {
return ConstantNode.forIntegerBits(PrimitiveStamp.getBits(stamp), 0);
}
return new UnsignedRightShiftNode(other.getX(), ConstantNode.forInt(total));
} else if (other instanceof LeftShiftNode && otherAmount == amount) {
if (stamp.getStackKind() == JavaKind.Long) {
return new AndNode(other.getX(), ConstantNode.forLong(-1L >>> amount));
} else {
assert stamp.getStackKind() == JavaKind.Int : Assertions.errorMessage(node, op, stamp, forX, forY);
return new AndNode(other.getX(), ConstantNode.forInt(-1 >>> amount));
}
}
}
}
if (originalAmout != amount) {
return new UnsignedRightShiftNode(forX, ConstantNode.forInt(amount));
}
}
if (node != null) {
return node;
}
return new UnsignedRightShiftNode(forX, forY);
}
@Override
public void generate(NodeLIRBuilderTool nodeValueMap, ArithmeticLIRGeneratorTool gen) {
nodeValueMap.setResult(this, gen.emitUShr(nodeValueMap.operand(getX()), nodeValueMap.operand(getY())));
}
@Override
public boolean isNarrowable(int resultBits) {
/*
* Note that inserting a narrow before this node can change the input's stamp, as it can
* cause a preceding (Zero|Sign)ExtendNode to be canonicalized away.
*
* Therefore, since the scalar shift on the underlying hardware will be on either a 32 or 64
* bit operation, if resultBits < Integer.SIZE, the input to the shift cannot be narrowed.
*/
if (resultBits >= Integer.SIZE && super.isNarrowable(resultBits)) {
/*
* For unsigned right shifts, the narrow can be done before the shift if the cut off
* bits are all zero.
*/
IntegerStamp inputStamp = (IntegerStamp) getX().stamp(NodeView.DEFAULT);
return (inputStamp.mayBeSet() & ~(CodeUtil.mask(resultBits))) == 0;
} else {
return false;
}
}
}