BytecodeOps.java revision 953:221a84ef44c0 
1/*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.  Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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24 */
25
26package jdk.nashorn.internal.codegen.types;
27
28import jdk.internal.org.objectweb.asm.MethodVisitor;
29
30
31/**
32 * Interface for byte code generation for all runtime types. Each
33 * type implements this interface and provides the type specific
34 * operations to do the generic things described herein.
35 *
36 * The bytecode ops are coupled to a MethodVisitor from ASM for
37 * byte code generation. They know nothing about our MethodGenerator,
38 * which is the abstraction for working with Nashorn JS types
39 * For exmaple, anything like "two or one slots" for a type, which
40 * is represented in bytecode and ASM, is abstracted away in the
41 * MethodGenerator. There you just say "dup" or "store".
42 *
43 * @see Type
44 * @see MethodVisitor
45 */
46interface BytecodeOps {
47
48    /**
49     * Duplicate top entry of stack. If a too large depth is
50     * given, so that there are no possible bytecode instructions
51     * available to generate the dup sequence, null is returned.
52     *
53     * @param method  method visitor
54     * @param depth   how far should the copy be pushed down
55     *
56     * @return        the type at the top of the stack or null
57     */
58    Type dup(MethodVisitor method, int depth);
59
60    /**
61     * Pop an entry of this type from the top of the bytecode
62     * stack. This works regardless of what category this type
63     * is
64     *
65     * @param method  method visitor
66     *
67     * @return the popped type
68     */
69    Type pop(MethodVisitor method);
70
71    /**
72     * Swap this type with the bytecode stack with the one below
73     * Generate appropriate code no matter the categories of the
74     * two types
75     *
76     * @param method  method visitor
77     * @param other   the type below this one on the stack
78     *
79     * @return        the other type
80     */
81    Type swap(MethodVisitor method, Type other);
82
83    /**
84     * Pop two values on top of the stack and add the
85     * first to the second, pushing the result on the stack
86     *
87     * @param method  method visitor
88     * @param programPoint program point id
89     * @return result type
90     */
91    Type add(MethodVisitor method, int programPoint);
92
93    /**
94     * Load a variable from a local slot to the stack
95     *
96     * @param method method visitor
97     * @param slot   the slot to load
98     *
99     * @return       the type that was loaded
100     */
101    Type load(MethodVisitor method, int slot);
102
103    /**
104     * Store a variable from the stack to a local slot
105     *
106     * @param method  method visitor
107     * @param slot    the slot to store to
108     */
109    void store(MethodVisitor method, int slot);
110
111    /**
112     * Load a constant to the stack.
113     *
114     * @param method  method visitor
115     * @param c       the value of the constant
116     *
117     * @return        the type at the top of the stack after load
118     */
119    Type ldc(MethodVisitor method, Object c);
120
121    /**
122     * Load the "undefined" value to the stack. Note that
123     * there may be different representations of this for
124     * e.g. doubles and objects. Abstraction removes this
125     *
126     * @param  method  method visitor.
127     *
128     * @return the undefined type at the top of the stack
129     */
130    Type loadUndefined(MethodVisitor method);
131
132    /**
133     * Load the "forced initializer" value to the stack, used to ensure that a local variable has a value when it is
134     * read by the unwarranted optimism catch block.
135     *
136     * @param  method  method visitor.
137     *
138     * @return the forced initialization type at the top of the stack
139     */
140    Type loadForcedInitializer(MethodVisitor method);
141
142
143    /**
144     * Load the "empty" value to the stack.
145     *
146     * @param  method  method visitor.
147     * @return the undefined type at the top of the stack
148     */
149    Type loadEmpty(MethodVisitor method);
150
151    /**
152     * Generate code that pops and casts the element on top of the
153     * stack to another type, given as parameter
154     *
155     * @param method  method visitor
156     * @param to      the type to cast to
157     *
158     * @return the to type
159     */
160    Type convert(MethodVisitor method, Type to);
161
162    /**
163     * Return the parameter on top of the stack
164     * from a method
165     *
166     * @param method the method visitor
167     */
168    void _return(MethodVisitor method);
169
170}
171