1 /*
   2  * Copyright (c) 2009, 2015, 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 package org.graalvm.compiler.nodes.calc;
  24 
  25 import static org.graalvm.compiler.nodeinfo.NodeCycles.CYCLES_1;
  26 import static org.graalvm.compiler.nodeinfo.NodeSize.SIZE_1;
  27 
  28 import java.io.Serializable;
  29 import java.util.function.Function;
  30 
  31 import org.graalvm.compiler.core.common.type.ArithmeticOpTable;
  32 import org.graalvm.compiler.core.common.type.ArithmeticOpTable.ShiftOp;
  33 import org.graalvm.compiler.core.common.type.IntegerStamp;
  34 import org.graalvm.compiler.core.common.type.Stamp;
  35 import org.graalvm.compiler.graph.NodeClass;
  36 import org.graalvm.compiler.graph.spi.CanonicalizerTool;
  37 import org.graalvm.compiler.nodeinfo.NodeInfo;
  38 import org.graalvm.compiler.nodes.ArithmeticOperation;
  39 import org.graalvm.compiler.nodes.ConstantNode;
  40 import org.graalvm.compiler.nodes.ValueNode;
  41 import org.graalvm.compiler.nodes.spi.ArithmeticLIRLowerable;
  42 
  43 import jdk.vm.ci.code.CodeUtil;
  44 import jdk.vm.ci.meta.JavaConstant;
  45 import jdk.vm.ci.meta.JavaKind;
  46 
  47 /**
  48  * The {@code ShiftOp} class represents shift operations.
  49  */
  50 @NodeInfo(cycles = CYCLES_1, size = SIZE_1)
  51 public abstract class ShiftNode<OP> extends BinaryNode implements ArithmeticOperation, ArithmeticLIRLowerable, NarrowableArithmeticNode {
  52 
  53     @SuppressWarnings("rawtypes") public static final NodeClass<ShiftNode> TYPE = NodeClass.create(ShiftNode.class);
  54 
  55     protected interface SerializableShiftFunction<T> extends Function<ArithmeticOpTable, ShiftOp<T>>, Serializable {
  56     }
  57 
  58     protected final SerializableShiftFunction<OP> getOp;
  59 
  60     /**
  61      * Creates a new shift operation.
  62      *
  63      * @param x the first input value
  64      * @param s the second input value
  65      */
  66     protected ShiftNode(NodeClass<? extends ShiftNode<OP>> c, SerializableShiftFunction<OP> getOp, ValueNode x, ValueNode s) {
  67         super(c, getOp.apply(ArithmeticOpTable.forStamp(x.stamp())).foldStamp(x.stamp(), (IntegerStamp) s.stamp()), x, s);
  68         assert ((IntegerStamp) s.stamp()).getBits() == 32;
  69         this.getOp = getOp;
  70     }
  71 
  72     protected final ShiftOp<OP> getOp(ValueNode forValue) {
  73         return getOp.apply(ArithmeticOpTable.forStamp(forValue.stamp()));
  74     }
  75 
  76     @Override
  77     public final ShiftOp<OP> getArithmeticOp() {
  78         return getOp(getX());
  79     }
  80 
  81     @Override
  82     public Stamp foldStamp(Stamp stampX, Stamp stampY) {
  83         return getArithmeticOp().foldStamp(stampX, (IntegerStamp) stampY);
  84     }
  85 
  86     @Override
  87     public ValueNode canonical(CanonicalizerTool tool, ValueNode forX, ValueNode forY) {
  88         if (forX.isConstant() && forY.isConstant()) {
  89             JavaConstant amount = forY.asJavaConstant();
  90             assert amount.getJavaKind() == JavaKind.Int;
  91             return ConstantNode.forPrimitive(stamp(), getOp(forX).foldConstant(forX.asConstant(), amount.asInt()));
  92         }
  93         return this;
  94     }
  95 
  96     public int getShiftAmountMask() {
  97         return getArithmeticOp().getShiftAmountMask(stamp());
  98     }
  99 
 100     @Override
 101     public boolean isNarrowable(int resultBits) {
 102         assert CodeUtil.isPowerOf2(resultBits);
 103         int narrowMask = resultBits - 1;
 104         int wideMask = getShiftAmountMask();
 105         assert (wideMask & narrowMask) == narrowMask : String.format("wideMask %x should be wider than narrowMask %x", wideMask, narrowMask);
 106 
 107         /*
 108          * Shifts are special because narrowing them also changes the implicit mask of the shift
 109          * amount. We can narrow only if (y & wideMask) == (y & narrowMask) for all possible values
 110          * of y.
 111          */
 112         IntegerStamp yStamp = (IntegerStamp) getY().stamp();
 113         return (yStamp.upMask() & (wideMask & ~narrowMask)) == 0;
 114     }
 115 }