1 /*
   2  * Copyright (c) 2011, 2019, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  */
  23 
  24 
  25 package org.graalvm.compiler.nodes.calc;
  26 
  27 import jdk.vm.ci.code.CodeUtil;
  28 import org.graalvm.compiler.core.common.type.ArithmeticOpTable;
  29 import org.graalvm.compiler.core.common.type.ArithmeticOpTable.ShiftOp.UShr;
  30 import org.graalvm.compiler.core.common.type.IntegerStamp;
  31 import org.graalvm.compiler.core.common.type.Stamp;
  32 import org.graalvm.compiler.graph.NodeClass;
  33 import org.graalvm.compiler.graph.spi.CanonicalizerTool;
  34 import org.graalvm.compiler.lir.gen.ArithmeticLIRGeneratorTool;
  35 import org.graalvm.compiler.nodeinfo.NodeInfo;
  36 import org.graalvm.compiler.nodes.ConstantNode;
  37 import org.graalvm.compiler.nodes.NodeView;
  38 import org.graalvm.compiler.nodes.ValueNode;
  39 import org.graalvm.compiler.nodes.spi.NodeLIRBuilderTool;
  40 
  41 import jdk.vm.ci.meta.JavaKind;
  42 
  43 @NodeInfo(shortName = ">>>")
  44 public final class UnsignedRightShiftNode extends ShiftNode<UShr> {
  45 
  46     public static final NodeClass<UnsignedRightShiftNode> TYPE = NodeClass.create(UnsignedRightShiftNode.class);
  47 
  48     public UnsignedRightShiftNode(ValueNode x, ValueNode y) {
  49         super(TYPE, ArithmeticOpTable::getUShr, x, y);
  50     }
  51 
  52     public static ValueNode create(ValueNode x, ValueNode y, NodeView view) {
  53         ArithmeticOpTable.ShiftOp<UShr> op = ArithmeticOpTable.forStamp(x.stamp(view)).getUShr();
  54         Stamp stamp = op.foldStamp(x.stamp(view), (IntegerStamp) y.stamp(view));
  55         ValueNode value = ShiftNode.canonical(op, stamp, x, y, view);
  56         if (value != null) {
  57             return value;
  58         }
  59 
  60         return canonical(null, op, stamp, x, y, view);
  61     }
  62 
  63     @Override
  64     public ValueNode canonical(CanonicalizerTool tool, ValueNode forX, ValueNode forY) {
  65         NodeView view = NodeView.from(tool);
  66         ValueNode ret = super.canonical(tool, forX, forY);
  67         if (ret != this) {
  68             return ret;
  69         }
  70 
  71         return canonical(this, this.getArithmeticOp(), this.stamp(view), forX, forY, view);
  72     }
  73 
  74     @SuppressWarnings("unused")
  75     private static ValueNode canonical(UnsignedRightShiftNode node, ArithmeticOpTable.ShiftOp<UShr> op, Stamp stamp, ValueNode forX, ValueNode forY, NodeView view) {
  76         if (forY.isConstant()) {
  77             int amount = forY.asJavaConstant().asInt();
  78             int originalAmout = amount;
  79             int mask = op.getShiftAmountMask(stamp);
  80             amount &= mask;
  81             if (amount == 0) {
  82                 return forX;
  83             }
  84 
  85             Stamp xStampGeneric = forX.stamp(view);
  86             if (xStampGeneric instanceof IntegerStamp) {
  87                 IntegerStamp xStamp = (IntegerStamp) xStampGeneric;
  88                 long xMask = CodeUtil.mask(xStamp.getBits());
  89                 long xLowerBound = xStamp.lowerBound() & xMask;
  90                 long xUpperBound = xStamp.upperBound() & xMask;
  91 
  92                 if (xLowerBound >>> amount == xUpperBound >>> amount) {
  93                     // The result of the shift is constant.
  94                     return ConstantNode.forIntegerKind(stamp.getStackKind(), xLowerBound >>> amount);
  95                 }
  96 
  97                 if (amount == xStamp.getBits() - 1 && xStamp.lowerBound() == -1 && xStamp.upperBound() == 0) {
  98                     // Shift is equivalent to a negation, i.e., turns -1 into 1 and keeps 0 at 0.
  99                     return NegateNode.create(forX, view);
 100                 }
 101             }
 102 
 103             if (forX instanceof ShiftNode) {
 104                 ShiftNode<?> other = (ShiftNode<?>) forX;
 105                 if (other.getY().isConstant()) {
 106                     int otherAmount = other.getY().asJavaConstant().asInt() & mask;
 107                     if (other instanceof UnsignedRightShiftNode) {
 108                         int total = amount + otherAmount;
 109                         if (total != (total & mask)) {
 110                             return ConstantNode.forIntegerKind(stamp.getStackKind(), 0);
 111                         }
 112                         return new UnsignedRightShiftNode(other.getX(), ConstantNode.forInt(total));
 113                     } else if (other instanceof LeftShiftNode && otherAmount == amount) {
 114                         if (stamp.getStackKind() == JavaKind.Long) {
 115                             return new AndNode(other.getX(), ConstantNode.forLong(-1L >>> amount));
 116                         } else {
 117                             assert stamp.getStackKind() == JavaKind.Int;
 118                             return new AndNode(other.getX(), ConstantNode.forInt(-1 >>> amount));
 119                         }
 120                     }
 121                 }
 122             }
 123             if (originalAmout != amount) {
 124                 return new UnsignedRightShiftNode(forX, ConstantNode.forInt(amount));
 125             }
 126         }
 127 
 128         if (node != null) {
 129             return node;
 130         }
 131         return new UnsignedRightShiftNode(forX, forY);
 132     }
 133 
 134     @Override
 135     public void generate(NodeLIRBuilderTool nodeValueMap, ArithmeticLIRGeneratorTool gen) {
 136         nodeValueMap.setResult(this, gen.emitUShr(nodeValueMap.operand(getX()), nodeValueMap.operand(getY())));
 137     }
 138 
 139     @Override
 140     public boolean isNarrowable(int resultBits) {
 141         if (super.isNarrowable(resultBits)) {
 142             /*
 143              * For unsigned right shifts, the narrow can be done before the shift if the cut off
 144              * bits are all zero.
 145              */
 146             IntegerStamp inputStamp = (IntegerStamp) getX().stamp(NodeView.DEFAULT);
 147             return (inputStamp.upMask() & ~(resultBits - 1)) == 0;
 148         } else {
 149             return false;
 150         }
 151     }
 152 }
--- EOF ---