1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
|
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.drill.exec.compile.bytecode;
import org.objectweb.asm.tree.analysis.Analyzer;
import org.objectweb.asm.tree.analysis.Frame;
import org.objectweb.asm.tree.analysis.Interpreter;
import org.objectweb.asm.tree.analysis.Value;
/**
* Analyzer that allows us to inject additional functionality into ASMs basic analysis.
*
* <p>We need to be able to keep track of local variables that are assigned to each other
* so that we can infer their replacability (for scalar replacement). In order to do that,
* we need to know when local variables are assigned (with the old value being overwritten)
* so that we can associate them with the new value, and hence determine whether they can
* also be replaced, or not.
*
* <p>In order to capture the assignment operation, we have to provide our own Frame<>, but
* ASM doesn't provide a direct way to do that. Here, we use the Analyzer's newFrame() methods
* as factories that will provide our own derivative of Frame<> which we use to detect
*/
public class MethodAnalyzer<V extends Value> extends Analyzer <V> {
/**
* Custom Frame<> that captures setLocal() calls in order to associate values
* that are assigned to the same local variable slot.
*
* <p>Since this is almost a pass-through, the constructors' arguments match
* those from Frame<>.
*/
private static class AssignmentTrackingFrame<V extends Value> extends Frame<V> {
/**
* Constructor.
*
* @param nLocals the number of locals the frame should have
* @param nStack the maximum size of the stack the frame should have
*/
public AssignmentTrackingFrame(final int nLocals, final int nStack) {
super(nLocals, nStack);
}
/**
* Copy constructor.
*
* @param src the frame being copied
*/
public AssignmentTrackingFrame(final Frame<? extends V> src) {
super(src);
}
@Override
public void setLocal(final int i, final V value) {
/*
* If we're replacing one ReplacingBasicValue with another, we need to
* associate them together so that they will have the same replacability
* attributes. We also track the local slot the new value will be stored in.
*/
if (value instanceof ReplacingBasicValue) {
final ReplacingBasicValue replacingValue = (ReplacingBasicValue) value;
replacingValue.setFrameSlot(i);
final V localValue = getLocal(i);
if ((localValue != null) && (localValue instanceof ReplacingBasicValue)) {
final ReplacingBasicValue localReplacingValue = (ReplacingBasicValue) localValue;
localReplacingValue.associate(replacingValue);
}
}
super.setLocal(i, value);
}
}
/**
* Constructor.
*
* @param interpreter the interpreter to use
*/
public MethodAnalyzer(final Interpreter<V> interpreter) {
super(interpreter);
}
@Override
protected Frame<V> newFrame(final int maxLocals, final int maxStack) {
return new AssignmentTrackingFrame<V>(maxLocals, maxStack);
}
@Override
protected Frame<V> newFrame(final Frame<? extends V> src) {
return new AssignmentTrackingFrame<V>(src);
}
}
|
