1 /* 2 * Copyright (c) 2011, 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 org.graalvm.compiler.core.common.type.ArithmeticOpTable; 26 import org.graalvm.compiler.core.common.type.ArithmeticOpTable.ShiftOp.Shr; 27 import org.graalvm.compiler.core.common.type.IntegerStamp; 28 import org.graalvm.compiler.graph.NodeClass; 29 import org.graalvm.compiler.graph.spi.CanonicalizerTool; 30 import org.graalvm.compiler.lir.gen.ArithmeticLIRGeneratorTool; 31 import org.graalvm.compiler.nodeinfo.NodeInfo; 32 import org.graalvm.compiler.nodes.ConstantNode; 33 import org.graalvm.compiler.nodes.ValueNode; 34 import org.graalvm.compiler.nodes.spi.NodeLIRBuilderTool; 35 36 import jdk.vm.ci.code.CodeUtil; 37 38 @NodeInfo(shortName = ">>") 39 public final class RightShiftNode extends ShiftNode<Shr> { 40 41 public static final NodeClass<RightShiftNode> TYPE = NodeClass.create(RightShiftNode.class); 42 43 public RightShiftNode(ValueNode x, ValueNode y) { 44 super(TYPE, ArithmeticOpTable::getShr, x, y); 45 } 46 47 @Override 48 public ValueNode canonical(CanonicalizerTool tool, ValueNode forX, ValueNode forY) { 49 ValueNode ret = super.canonical(tool, forX, forY); 50 if (ret != this) { 51 return ret; 52 } 53 54 if (forX.stamp() instanceof IntegerStamp && ((IntegerStamp) forX.stamp()).isPositive()) { 55 return new UnsignedRightShiftNode(forX, forY); 56 } 57 58 if (forY.isConstant()) { 59 int amount = forY.asJavaConstant().asInt(); 60 int originalAmout = amount; 61 int mask = getShiftAmountMask(); 62 amount &= mask; 63 if (amount == 0) { 64 return forX; 65 } 66 if (forX instanceof ShiftNode) { 67 ShiftNode<?> other = (ShiftNode<?>) forX; 68 if (other.getY().isConstant()) { 69 int otherAmount = other.getY().asJavaConstant().asInt() & mask; 70 if (other instanceof RightShiftNode) { 71 int total = amount + otherAmount; 72 if (total != (total & mask)) { 73 assert other.getX().stamp() instanceof IntegerStamp; 74 IntegerStamp istamp = (IntegerStamp) other.getX().stamp(); 75 76 if (istamp.isPositive()) { 77 return ConstantNode.forIntegerKind(getStackKind(), 0); 78 } 79 if (istamp.isStrictlyNegative()) { 80 return ConstantNode.forIntegerKind(getStackKind(), -1L); 81 } 82 83 /* 84 * if we cannot replace both shifts with a constant, replace them by a 85 * full shift for this kind 86 */ 87 assert total >= mask; 88 return new RightShiftNode(other.getX(), ConstantNode.forInt(mask)); 89 } 90 return new RightShiftNode(other.getX(), ConstantNode.forInt(total)); 91 } 92 } 93 } 94 if (originalAmout != amount) { 95 return new RightShiftNode(forX, ConstantNode.forInt(amount)); 96 } 97 } 98 return this; 99 } 100 101 @Override 102 public void generate(NodeLIRBuilderTool nodeValueMap, ArithmeticLIRGeneratorTool gen) { 103 nodeValueMap.setResult(this, gen.emitShr(nodeValueMap.operand(getX()), nodeValueMap.operand(getY()))); 104 } 105 106 @Override 107 public boolean isNarrowable(int resultBits) { 108 if (super.isNarrowable(resultBits)) { 109 /* 110 * For signed right shifts, the narrow can be done before the shift if the cut off bits 111 * are all equal to the sign bit of the input. That's equivalent to the condition that 112 * the input is in the signed range of the narrow type. 113 */ 114 IntegerStamp inputStamp = (IntegerStamp) getX().stamp(); 115 return CodeUtil.minValue(resultBits) <= inputStamp.lowerBound() && inputStamp.upperBound() <= CodeUtil.maxValue(resultBits); 116 } else { 117 return false; 118 } 119 } 120 }