1 /*
2 * Copyright (c) 2012, 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.loop;
24
25 import static org.graalvm.compiler.loop.MathUtil.add;
26 import static org.graalvm.compiler.loop.MathUtil.divBefore;
27 import static org.graalvm.compiler.loop.MathUtil.sub;
28
29 import org.graalvm.compiler.core.common.type.IntegerStamp;
30 import org.graalvm.compiler.core.common.type.Stamp;
31 import org.graalvm.compiler.loop.InductionVariable.Direction;
32 import org.graalvm.compiler.nodes.AbstractBeginNode;
33 import org.graalvm.compiler.nodes.ConstantNode;
34 import org.graalvm.compiler.nodes.GuardNode;
35 import org.graalvm.compiler.nodes.StructuredGraph;
36 import org.graalvm.compiler.nodes.ValueNode;
37 import org.graalvm.compiler.nodes.calc.CompareNode;
38 import org.graalvm.compiler.nodes.calc.ConditionalNode;
39 import org.graalvm.compiler.nodes.calc.IntegerLessThanNode;
40 import org.graalvm.compiler.nodes.extended.GuardingNode;
41
42 import jdk.vm.ci.code.CodeUtil;
43 import jdk.vm.ci.meta.DeoptimizationAction;
44 import jdk.vm.ci.meta.DeoptimizationReason;
45 import jdk.vm.ci.meta.JavaConstant;
46
47 public class CountedLoopInfo {
48
49 private final LoopEx loop;
50 private InductionVariable iv;
51 private ValueNode end;
52 private boolean oneOff;
53 private AbstractBeginNode body;
54
55 CountedLoopInfo(LoopEx loop, InductionVariable iv, ValueNode end, boolean oneOff, AbstractBeginNode body) {
56 this.loop = loop;
57 this.iv = iv;
58 this.end = end;
59 this.oneOff = oneOff;
60 this.body = body;
61 }
62
63 public ValueNode maxTripCountNode() {
64 return maxTripCountNode(false);
65 }
66
67 public ValueNode maxTripCountNode(boolean assumePositive) {
68 StructuredGraph graph = iv.valueNode().graph();
69 Stamp stamp = iv.valueNode().stamp();
70 ValueNode range = sub(graph, end, iv.initNode());
71
72 ValueNode oneDirection;
73 if (iv.direction() == Direction.Up) {
74 oneDirection = ConstantNode.forIntegerStamp(stamp, 1, graph);
75 } else {
76 assert iv.direction() == Direction.Down;
77 oneDirection = ConstantNode.forIntegerStamp(stamp, -1, graph);
78 }
79 if (oneOff) {
80 range = add(graph, range, oneDirection);
81 }
82 // round-away-from-zero divison: (range + stride -/+ 1) / stride
83 ValueNode denominator = add(graph, sub(graph, range, oneDirection), iv.strideNode());
84 ValueNode div = divBefore(graph, loop.entryPoint(), denominator, iv.strideNode());
85
86 if (assumePositive) {
87 return div;
88 }
89 ConstantNode zero = ConstantNode.forIntegerStamp(stamp, 0, graph);
90 return graph.unique(new ConditionalNode(graph.unique(new IntegerLessThanNode(zero, div)), div, zero));
91 }
92
93 /**
94 * @return true if the loop has constant bounds and the trip count is representable as a
95 * positive integer.
96 */
97 public boolean isConstantMaxTripCount() {
98 /*
99 * It's possible that the iteration range is too large to treat this as constant because it
100 * will overflow.
101 */
102 return (hasConstantBounds() && rawConstantMaxTripCount() >= 0);
103 }
104
105 /**
106 * @return true if the bounds on the iteration space are all constants.
107 */
108 public boolean hasConstantBounds() {
109 return end instanceof ConstantNode && iv.isConstantInit() && iv.isConstantStride();
110 }
111
112 public long constantMaxTripCount() {
113 assert isConstantMaxTripCount();
114 return rawConstantMaxTripCount();
115 }
116
117 /**
118 * Compute the raw value of the trip count for this loop. Since we don't have unsigned values
119 * this may be outside representable positive values.
120 */
121 protected long rawConstantMaxTripCount() {
122 assert iv.direction() != null;
123 long off = oneOff ? iv.direction() == Direction.Up ? 1 : -1 : 0;
124 long endValue = ((ConstantNode) end).asJavaConstant().asLong();
125 try {
126 // If no overflow occurs then negative values represent a trip count of 0
127 long max = Math.subtractExact(Math.addExact(endValue, off), iv.constantInit()) / iv.constantStride();
128 return Math.max(0, max);
129 } catch (ArithmeticException e) {
130 /*
131 * The computation overflowed to return a negative value. It's possible some
132 * optimization could handle this value as an unsigned and produce the right answer but
133 * we hide this value by default.
134 */
135 return -1;
136 }
137 }
138
139 public boolean isExactTripCount() {
140 return loop.loopBegin().loopExits().count() == 1;
141 }
142
143 public ValueNode exactTripCountNode() {
144 assert isExactTripCount();
145 return maxTripCountNode();
146 }
147
148 public boolean isConstantExactTripCount() {
149 assert isExactTripCount();
150 return isConstantMaxTripCount();
151 }
152
153 public long constantExactTripCount() {
154 assert isExactTripCount();
155 return constantMaxTripCount();
156 }
157
158 @Override
159 public String toString() {
160 return "iv=" + iv + " until " + end + (oneOff ? iv.direction() == Direction.Up ? "+1" : "-1" : "");
161 }
162
163 public ValueNode getLimit() {
164 return end;
165 }
166
167 public ValueNode getStart() {
168 return iv.initNode();
169 }
170
171 public boolean isLimitIncluded() {
172 return oneOff;
173 }
174
175 public AbstractBeginNode getBody() {
176 return body;
177 }
178
179 public Direction getDirection() {
180 return iv.direction();
181 }
182
183 public InductionVariable getCounter() {
184 return iv;
185 }
186
187 public GuardingNode getOverFlowGuard() {
188 return loop.loopBegin().getOverflowGuard();
189 }
190
191 public GuardingNode createOverFlowGuard() {
192 GuardingNode overflowGuard = getOverFlowGuard();
193 if (overflowGuard != null) {
194 return overflowGuard;
195 }
196 IntegerStamp stamp = (IntegerStamp) iv.valueNode().stamp();
197 StructuredGraph graph = iv.valueNode().graph();
198 CompareNode cond; // we use a negated guard with a < condition to achieve a >=
199 ConstantNode one = ConstantNode.forIntegerStamp(stamp, 1, graph);
200 if (iv.direction() == Direction.Up) {
201 ValueNode v1 = sub(graph, ConstantNode.forIntegerStamp(stamp, CodeUtil.maxValue(stamp.getBits()), graph), sub(graph, iv.strideNode(), one));
202 if (oneOff) {
203 v1 = sub(graph, v1, one);
204 }
205 cond = graph.unique(new IntegerLessThanNode(v1, end));
206 } else {
207 assert iv.direction() == Direction.Down;
208 ValueNode v1 = add(graph, ConstantNode.forIntegerStamp(stamp, CodeUtil.minValue(stamp.getBits()), graph), sub(graph, one, iv.strideNode()));
209 if (oneOff) {
210 v1 = add(graph, v1, one);
211 }
212 cond = graph.unique(new IntegerLessThanNode(end, v1));
213 }
214 assert graph.getGuardsStage().allowsFloatingGuards();
215 overflowGuard = graph.unique(new GuardNode(cond, AbstractBeginNode.prevBegin(loop.entryPoint()), DeoptimizationReason.LoopLimitCheck, DeoptimizationAction.InvalidateRecompile, true,
216 JavaConstant.NULL_POINTER)); // TODO gd: use speculation
217 loop.loopBegin().setOverflowGuard(overflowGuard);
218 return overflowGuard;
219 }
220
221 public IntegerStamp getStamp() {
222 return (IntegerStamp) iv.valueNode().stamp();
223 }
224 }