hotspot/src/jdk.vm.compiler/share/classes/org.graalvm.compiler.replacements/src/org/graalvm/compiler/replacements/nodes/arithmetic/IntegerAddExactNode.java

/*
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 * 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.
 *
 * 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 org.graalvm.compiler.replacements.nodes.arithmetic;

import static org.graalvm.compiler.core.common.type.IntegerStamp.addOverflowsNegatively;
import static org.graalvm.compiler.core.common.type.IntegerStamp.addOverflowsPositively;
import static org.graalvm.compiler.core.common.type.IntegerStamp.carryBits;
import static org.graalvm.compiler.nodeinfo.NodeCycles.CYCLES_2;
import static org.graalvm.compiler.nodeinfo.NodeSize.SIZE_2;

import org.graalvm.compiler.core.common.type.IntegerStamp;
import org.graalvm.compiler.core.common.type.Stamp;
import org.graalvm.compiler.core.common.type.StampFactory;
import org.graalvm.compiler.graph.NodeClass;
import org.graalvm.compiler.graph.spi.CanonicalizerTool;
import org.graalvm.compiler.nodeinfo.NodeInfo;
import org.graalvm.compiler.nodes.AbstractBeginNode;
import org.graalvm.compiler.nodes.ConstantNode;
import org.graalvm.compiler.nodes.ValueNode;
import org.graalvm.compiler.nodes.calc.AddNode;
import org.graalvm.compiler.nodes.spi.LoweringTool;

import jdk.vm.ci.code.CodeUtil;
import jdk.vm.ci.meta.JavaConstant;
import jdk.vm.ci.meta.JavaKind;

/**
 * Node representing an exact integer addition that will throw an {@link ArithmeticException} in
 * case the addition would overflow the 32 bit range.
 */
@NodeInfo(cycles = CYCLES_2, size = SIZE_2)
public final class IntegerAddExactNode extends AddNode implements IntegerExactArithmeticNode {
    public static final NodeClass<IntegerAddExactNode> TYPE = NodeClass.create(IntegerAddExactNode.class);

    public IntegerAddExactNode(ValueNode x, ValueNode y) {
        super(TYPE, x, y);
        setStamp(x.stamp().unrestricted());
        assert x.stamp().isCompatible(y.stamp()) && x.stamp() instanceof IntegerStamp;
    }

    @Override
    public boolean inferStamp() {
        /*
         * Note: it is not allowed to use the foldStamp method of the regular add node as we do not
         * know the result stamp of this node if we do not know whether we may deopt. If we know we
         * can never overflow we will replace this node with its non overflow checking counterpart
         * anyway.
         */
        return false;
    }

    @Override
    public Stamp foldStamp(Stamp stampX, Stamp stampY) {
        IntegerStamp a = (IntegerStamp) stampX;
        IntegerStamp b = (IntegerStamp) stampY;

        int bits = a.getBits();
        assert bits == b.getBits();

        long defaultMask = CodeUtil.mask(bits);
        long variableBits = (a.downMask() ^ a.upMask()) | (b.downMask() ^ b.upMask());
        long variableBitsWithCarry = variableBits | (carryBits(a.downMask(), b.downMask()) ^ carryBits(a.upMask(), b.upMask()));
        long newDownMask = (a.downMask() + b.downMask()) & ~variableBitsWithCarry;
        long newUpMask = (a.downMask() + b.downMask()) | variableBitsWithCarry;

        newDownMask &= defaultMask;
        newUpMask &= defaultMask;

        long newLowerBound;
        long newUpperBound;
        boolean lowerOverflowsPositively = addOverflowsPositively(a.lowerBound(), b.lowerBound(), bits);
        boolean upperOverflowsPositively = addOverflowsPositively(a.upperBound(), b.upperBound(), bits);
        boolean lowerOverflowsNegatively = addOverflowsNegatively(a.lowerBound(), b.lowerBound(), bits);
        boolean upperOverflowsNegatively = addOverflowsNegatively(a.upperBound(), b.upperBound(), bits);
        if (lowerOverflowsPositively) {
            newLowerBound = CodeUtil.maxValue(bits);
        } else if (lowerOverflowsNegatively) {
            newLowerBound = CodeUtil.minValue(bits);
        } else {
            newLowerBound = CodeUtil.signExtend((a.lowerBound() + b.lowerBound()) & defaultMask, bits);
        }

        if (upperOverflowsPositively) {
            newUpperBound = CodeUtil.maxValue(bits);
        } else if (upperOverflowsNegatively) {
            newUpperBound = CodeUtil.minValue(bits);
        } else {
            newUpperBound = CodeUtil.signExtend((a.upperBound() + b.upperBound()) & defaultMask, bits);
        }

        IntegerStamp limit = StampFactory.forInteger(bits, newLowerBound, newUpperBound);
        newUpMask &= limit.upMask();
        newUpperBound = CodeUtil.signExtend(newUpperBound & newUpMask, bits);
        newDownMask |= limit.downMask();
        newLowerBound |= newDownMask;
        return new IntegerStamp(bits, newLowerBound, newUpperBound, newDownMask, newUpMask);
    }

    @Override
    public ValueNode canonical(CanonicalizerTool tool, ValueNode forX, ValueNode forY) {
        ValueNode result = findSynonym(forX, forY);
        if (result == null) {
            return this;
        } else {
            return result;
        }
    }

    private static ValueNode findSynonym(ValueNode forX, ValueNode forY) {
        if (forX.isConstant() && !forY.isConstant()) {
            return new IntegerAddExactNode(forY, forX);
        }
        if (forX.isConstant()) {
            ConstantNode constantNode = canonicalXconstant(forX, forY);
            if (constantNode != null) {
                return constantNode;
            }
        } else if (forY.isConstant()) {
            long c = forY.asJavaConstant().asLong();
            if (c == 0) {
                return forX;
            }
        }
        return null;
    }

    private static ConstantNode canonicalXconstant(ValueNode forX, ValueNode forY) {
        JavaConstant xConst = forX.asJavaConstant();
        JavaConstant yConst = forY.asJavaConstant();
        if (xConst != null && yConst != null) {
            assert xConst.getJavaKind() == yConst.getJavaKind();
            try {
                if (xConst.getJavaKind() == JavaKind.Int) {
                    return ConstantNode.forInt(Math.addExact(xConst.asInt(), yConst.asInt()));
                } else {
                    assert xConst.getJavaKind() == JavaKind.Long;
                    return ConstantNode.forLong(Math.addExact(xConst.asLong(), yConst.asLong()));
                }
            } catch (ArithmeticException ex) {
                // The operation will result in an overflow exception, so do not canonicalize.
            }
        }
        return null;
    }

    @Override
    public IntegerExactArithmeticSplitNode createSplit(AbstractBeginNode next, AbstractBeginNode deopt) {
        return graph().add(new IntegerAddExactSplitNode(stamp(), getX(), getY(), next, deopt));
    }

    @Override
    public void lower(LoweringTool tool) {
        IntegerExactArithmeticSplitNode.lower(tool, this);
    }
}