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 }