1 /*
2 * Copyright (c) 2011, 2018, 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 org.graalvm.compiler.core.common.type.ArithmeticOpTable;
28 import org.graalvm.compiler.core.common.type.ArithmeticOpTable.ShiftOp.Shr;
29 import org.graalvm.compiler.core.common.type.IntegerStamp;
30 import org.graalvm.compiler.core.common.type.Stamp;
31 import org.graalvm.compiler.graph.NodeClass;
32 import org.graalvm.compiler.graph.spi.CanonicalizerTool;
33 import org.graalvm.compiler.lir.gen.ArithmeticLIRGeneratorTool;
34 import org.graalvm.compiler.nodeinfo.NodeInfo;
35 import org.graalvm.compiler.nodes.ConstantNode;
36 import org.graalvm.compiler.nodes.NodeView;
37 import org.graalvm.compiler.nodes.ValueNode;
38 import org.graalvm.compiler.nodes.spi.NodeLIRBuilderTool;
39
40 import jdk.vm.ci.code.CodeUtil;
41
42 @NodeInfo(shortName = ">>")
43 public final class RightShiftNode extends ShiftNode<Shr> {
44
45 public static final NodeClass<RightShiftNode> TYPE = NodeClass.create(RightShiftNode.class);
46
47 public RightShiftNode(ValueNode x, ValueNode y) {
48 super(TYPE, ArithmeticOpTable::getShr, x, y);
49 }
50
51 public static ValueNode create(ValueNode x, int y, NodeView view) {
52 if (y == 0) {
53 return x;
54 }
55 return create(x, ConstantNode.forInt(y), view);
56 }
57
58 public static ValueNode create(ValueNode x, ValueNode y, NodeView view) {
59 ArithmeticOpTable.ShiftOp<Shr> op = ArithmeticOpTable.forStamp(x.stamp(view)).getShr();
60 Stamp stamp = op.foldStamp(x.stamp(view), (IntegerStamp) y.stamp(view));
61 ValueNode value = ShiftNode.canonical(op, stamp, x, y, view);
62 if (value != null) {
63 return value;
64 }
65
66 return canonical(null, op, stamp, x, y, view);
67 }
68
69 @Override
70 public ValueNode canonical(CanonicalizerTool tool, ValueNode forX, ValueNode forY) {
71 NodeView view = NodeView.from(tool);
72 ValueNode ret = super.canonical(tool, forX, forY);
73 if (ret != this) {
74 return ret;
75 }
76
77 return canonical(this, getArithmeticOp(), stamp(view), forX, forY, view);
78 }
79
80 private static ValueNode canonical(RightShiftNode rightShiftNode, ArithmeticOpTable.ShiftOp<Shr> op, Stamp stamp, ValueNode forX, ValueNode forY, NodeView view) {
81 RightShiftNode self = rightShiftNode;
82 if (forX.stamp(view) instanceof IntegerStamp && ((IntegerStamp) forX.stamp(view)).isPositive()) {
83 return new UnsignedRightShiftNode(forX, forY);
84 }
85
86 Stamp xStampGeneric = forX.stamp(view);
87 if (xStampGeneric instanceof IntegerStamp) {
88 IntegerStamp xStamp = (IntegerStamp) xStampGeneric;
89 if (xStamp.lowerBound() >= -1 && xStamp.upperBound() <= 0) {
90 // Right shift by any amount does not change any bit.
91 return forX;
92 }
93 }
94
95 if (forY.isConstant()) {
96 int amount = forY.asJavaConstant().asInt();
97 int originalAmout = amount;
98 int mask = op.getShiftAmountMask(stamp);
99 amount &= mask;
100 if (amount == 0) {
101 return forX;
102 }
103
104 if (xStampGeneric instanceof IntegerStamp) {
105 IntegerStamp xStamp = (IntegerStamp) xStampGeneric;
106
107 if (xStamp.lowerBound() >> amount == xStamp.upperBound() >> amount) {
108 // Right shift turns the result of the expression into a constant.
109 return ConstantNode.forIntegerKind(stamp.getStackKind(), xStamp.lowerBound() >> amount);
110 }
111 }
112
113 if (forX instanceof ShiftNode) {
114 ShiftNode<?> other = (ShiftNode<?>) forX;
115 if (other.getY().isConstant()) {
116 int otherAmount = other.getY().asJavaConstant().asInt() & mask;
117 if (other instanceof RightShiftNode) {
118 int total = amount + otherAmount;
119 if (total != (total & mask)) {
120 assert other.getX().stamp(view) instanceof IntegerStamp;
121 IntegerStamp istamp = (IntegerStamp) other.getX().stamp(view);
122
123 if (istamp.isPositive()) {
124 return ConstantNode.forIntegerKind(stamp.getStackKind(), 0);
125 }
126 if (istamp.isStrictlyNegative()) {
127 return ConstantNode.forIntegerKind(stamp.getStackKind(), -1L);
128 }
129
130 /*
131 * if we cannot replace both shifts with a constant, replace them by a
132 * full shift for this kind
133 */
134 assert total >= mask;
135 return new RightShiftNode(other.getX(), ConstantNode.forInt(mask));
136 }
137 return new RightShiftNode(other.getX(), ConstantNode.forInt(total));
138 }
139 }
140 }
141 if (originalAmout != amount) {
142 return new RightShiftNode(forX, ConstantNode.forInt(amount));
143 }
144 }
145 if (self == null) {
146 self = new RightShiftNode(forX, forY);
147 }
148 return self;
149 }
150
151 @Override
152 public void generate(NodeLIRBuilderTool nodeValueMap, ArithmeticLIRGeneratorTool gen) {
153 nodeValueMap.setResult(this, gen.emitShr(nodeValueMap.operand(getX()), nodeValueMap.operand(getY())));
154 }
155
156 @Override
157 public boolean isNarrowable(int resultBits) {
158 if (super.isNarrowable(resultBits)) {
159 /*
160 * For signed right shifts, the narrow can be done before the shift if the cut off bits
161 * are all equal to the sign bit of the input. That's equivalent to the condition that
162 * the input is in the signed range of the narrow type.
163 */
164 IntegerStamp inputStamp = (IntegerStamp) getX().stamp(NodeView.DEFAULT);
165 return CodeUtil.minValue(resultBits) <= inputStamp.lowerBound() && inputStamp.upperBound() <= CodeUtil.maxValue(resultBits);
166 } else {
167 return false;
168 }
169 }
170 }