001/*
002 * Copyright (c) 2012, 2014, 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.replacements.amd64;
024
025import jdk.internal.jvmci.code.*;
026import jdk.internal.jvmci.meta.*;
027
028import com.oracle.graal.compiler.common.type.*;
029import com.oracle.graal.graph.*;
030import com.oracle.graal.graph.spi.*;
031import com.oracle.graal.nodeinfo.*;
032import com.oracle.graal.nodes.*;
033import com.oracle.graal.nodes.calc.*;
034import com.oracle.graal.nodes.spi.*;
035
036/**
037 * Count the number of leading zeros using the {@code lzcntq} or {@code lzcntl} instructions.
038 */
039@NodeInfo
040public final class AMD64CountLeadingZerosNode extends UnaryNode implements LIRLowerable {
041    public static final NodeClass<AMD64CountLeadingZerosNode> TYPE = NodeClass.create(AMD64CountLeadingZerosNode.class);
042
043    public AMD64CountLeadingZerosNode(ValueNode value) {
044        super(TYPE, StampFactory.forInteger(Kind.Int, 0, ((PrimitiveStamp) value.stamp()).getBits()), value);
045        assert value.getKind() == Kind.Int || value.getKind() == Kind.Long;
046    }
047
048    @Override
049    public boolean inferStamp() {
050        assert value.getKind() == Kind.Int || value.getKind() == Kind.Long;
051        IntegerStamp valueStamp = (IntegerStamp) getValue().stamp();
052        long mask = CodeUtil.mask(valueStamp.getBits());
053        // Don't count zeros from the mask in the result.
054        int adjust = Long.numberOfLeadingZeros(mask);
055        assert adjust == 0 || adjust == 32;
056        int min = Long.numberOfLeadingZeros(valueStamp.upMask() & mask) - adjust;
057        int max = Long.numberOfLeadingZeros(valueStamp.downMask() & mask) - adjust;
058        return updateStamp(StampFactory.forInteger(Kind.Int, min, max));
059    }
060
061    public static ValueNode tryFold(ValueNode value) {
062        if (value.isConstant()) {
063            JavaConstant c = value.asJavaConstant();
064            if (value.getKind() == Kind.Int) {
065                return ConstantNode.forInt(Integer.numberOfLeadingZeros(c.asInt()));
066            } else {
067                return ConstantNode.forInt(Long.numberOfLeadingZeros(c.asLong()));
068            }
069        }
070        return null;
071    }
072
073    @Override
074    public ValueNode canonical(CanonicalizerTool tool, ValueNode forValue) {
075        ValueNode folded = tryFold(forValue);
076        return folded != null ? folded : this;
077    }
078
079    @Override
080    public void generate(NodeLIRBuilderTool gen) {
081        Value result = gen.getLIRGeneratorTool().emitCountLeadingZeros(gen.operand(getValue()));
082        gen.setResult(this, result);
083    }
084}