001/*
002 * Copyright (c) 2011, 2015, Oracle and/or its affiliates. All rights reserved.
003 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004 *
005 * This code is free software; you can redistribute it and/or modify it
006 * under the terms of the GNU General Public License version 2 only, as
007 * published by the Free Software Foundation.
008 *
009 * This code is distributed in the hope that it will be useful, but WITHOUT
010 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
011 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
012 * version 2 for more details (a copy is included in the LICENSE file that
013 * accompanied this code).
014 *
015 * You should have received a copy of the GNU General Public License version
016 * 2 along with this work; if not, write to the Free Software Foundation,
017 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
018 *
019 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
020 * or visit www.oracle.com if you need additional information or have any
021 * questions.
022 */
023package com.oracle.graal.nodes.calc;
024
025import jdk.internal.jvmci.meta.*;
026
027import com.oracle.graal.compiler.common.type.*;
028import com.oracle.graal.compiler.common.type.ArithmeticOpTable.ShiftOp.UShr;
029import com.oracle.graal.graph.*;
030import com.oracle.graal.graph.spi.*;
031import com.oracle.graal.lir.gen.*;
032import com.oracle.graal.nodeinfo.*;
033import com.oracle.graal.nodes.*;
034import com.oracle.graal.nodes.spi.*;
035
036@NodeInfo(shortName = ">>>")
037public final class UnsignedRightShiftNode extends ShiftNode<UShr> {
038
039    public static final NodeClass<UnsignedRightShiftNode> TYPE = NodeClass.create(UnsignedRightShiftNode.class);
040
041    public UnsignedRightShiftNode(ValueNode x, ValueNode y) {
042        super(TYPE, ArithmeticOpTable::getUShr, x, y);
043    }
044
045    @Override
046    public ValueNode canonical(CanonicalizerTool tool, ValueNode forX, ValueNode forY) {
047        ValueNode ret = super.canonical(tool, forX, forY);
048        if (ret != this) {
049            return ret;
050        }
051
052        if (forY.isConstant()) {
053            int amount = forY.asJavaConstant().asInt();
054            int originalAmout = amount;
055            int mask = getShiftAmountMask();
056            amount &= mask;
057            if (amount == 0) {
058                return forX;
059            }
060            if (forX instanceof ShiftNode) {
061                ShiftNode<?> other = (ShiftNode<?>) forX;
062                if (other.getY().isConstant()) {
063                    int otherAmount = other.getY().asJavaConstant().asInt() & mask;
064                    if (other instanceof UnsignedRightShiftNode) {
065                        int total = amount + otherAmount;
066                        if (total != (total & mask)) {
067                            return ConstantNode.forIntegerKind(getKind(), 0);
068                        }
069                        return new UnsignedRightShiftNode(other.getX(), ConstantNode.forInt(total));
070                    } else if (other instanceof LeftShiftNode && otherAmount == amount) {
071                        if (getKind() == Kind.Long) {
072                            return new AndNode(other.getX(), ConstantNode.forLong(-1L >>> amount));
073                        } else {
074                            assert getKind() == Kind.Int;
075                            return new AndNode(other.getX(), ConstantNode.forInt(-1 >>> amount));
076                        }
077                    }
078                }
079            }
080            if (originalAmout != amount) {
081                return new UnsignedRightShiftNode(forX, ConstantNode.forInt(amount));
082            }
083        }
084        return this;
085    }
086
087    @Override
088    public void generate(NodeValueMap nodeValueMap, ArithmeticLIRGenerator gen) {
089        nodeValueMap.setResult(this, gen.emitUShr(nodeValueMap.operand(getX()), nodeValueMap.operand(getY())));
090    }
091
092    @Override
093    public boolean isNarrowable(int resultBits) {
094        if (super.isNarrowable(resultBits)) {
095            /*
096             * For unsigned right shifts, the narrow can be done before the shift if the cut off
097             * bits are all zero.
098             */
099            IntegerStamp inputStamp = (IntegerStamp) getX().stamp();
100            return (inputStamp.upMask() & ~(resultBits - 1)) == 0;
101        } else {
102            return false;
103        }
104    }
105}