1/*
2 * Copyright (C) 2007 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.android.dx.dex.code.form;
18
19import com.android.dx.dex.code.CstInsn;
20import com.android.dx.dex.code.DalvInsn;
21import com.android.dx.dex.code.InsnFormat;
22import com.android.dx.rop.code.RegisterSpec;
23import com.android.dx.rop.code.RegisterSpecList;
24import com.android.dx.rop.cst.Constant;
25import com.android.dx.rop.cst.CstMethodRef;
26import com.android.dx.rop.cst.CstType;
27import com.android.dx.rop.type.Type;
28import com.android.dx.util.AnnotatedOutput;
29import java.util.BitSet;
30
31/**
32 * Instruction format {@code 35c}. See the instruction format spec
33 * for details.
34 */
35public final class Form35c extends InsnFormat {
36    /** {@code non-null;} unique instance of this class */
37    public static final InsnFormat THE_ONE = new Form35c();
38
39    /** Maximal number of operands */
40    private static final int MAX_NUM_OPS = 5;
41
42    /**
43     * Constructs an instance. This class is not publicly
44     * instantiable. Use {@link #THE_ONE}.
45     */
46    private Form35c() {
47        // This space intentionally left blank.
48    }
49
50    /** {@inheritDoc} */
51    @Override
52    public String insnArgString(DalvInsn insn) {
53        RegisterSpecList regs = explicitize(insn.getRegisters());
54        return regListString(regs) + ", " + cstString(insn);
55    }
56
57    /** {@inheritDoc} */
58    @Override
59    public String insnCommentString(DalvInsn insn, boolean noteIndices) {
60        if (noteIndices) {
61            return cstComment(insn);
62        } else {
63            return "";
64        }
65    }
66
67    /** {@inheritDoc} */
68    @Override
69    public int codeSize() {
70        return 3;
71    }
72
73    /** {@inheritDoc} */
74    @Override
75    public boolean isCompatible(DalvInsn insn) {
76        if (!(insn instanceof CstInsn)) {
77            return false;
78        }
79
80        CstInsn ci = (CstInsn) insn;
81        int cpi = ci.getIndex();
82
83        if (! unsignedFitsInShort(cpi)) {
84            return false;
85        }
86
87        Constant cst = ci.getConstant();
88        if (!((cst instanceof CstMethodRef) ||
89              (cst instanceof CstType))) {
90            return false;
91        }
92
93        RegisterSpecList regs = ci.getRegisters();
94        return (wordCount(regs) >= 0);
95    }
96
97    /** {@inheritDoc} */
98    @Override
99    public BitSet compatibleRegs(DalvInsn insn) {
100        RegisterSpecList regs = insn.getRegisters();
101        int sz = regs.size();
102        BitSet bits = new BitSet(sz);
103
104        for (int i = 0; i < sz; i++) {
105            RegisterSpec reg = regs.get(i);
106            /*
107             * The check below adds (category - 1) to the register, to
108             * account for the fact that the second half of a
109             * category-2 register has to be represented explicitly in
110             * the result.
111             */
112            bits.set(i, unsignedFitsInNibble(reg.getReg() +
113                                             reg.getCategory() - 1));
114        }
115
116        return bits;
117    }
118
119    /** {@inheritDoc} */
120    @Override
121    public void writeTo(AnnotatedOutput out, DalvInsn insn) {
122        int cpi = ((CstInsn) insn).getIndex();
123        RegisterSpecList regs = explicitize(insn.getRegisters());
124        int sz = regs.size();
125        int r0 = (sz > 0) ? regs.get(0).getReg() : 0;
126        int r1 = (sz > 1) ? regs.get(1).getReg() : 0;
127        int r2 = (sz > 2) ? regs.get(2).getReg() : 0;
128        int r3 = (sz > 3) ? regs.get(3).getReg() : 0;
129        int r4 = (sz > 4) ? regs.get(4).getReg() : 0;
130
131        write(out,
132              opcodeUnit(insn,
133                         makeByte(r4, sz)), // encode the fifth operand here
134              (short) cpi,
135              codeUnit(r0, r1, r2, r3));
136    }
137
138    /**
139     * Gets the number of words required for the given register list, where
140     * category-2 values count as two words. Return {@code -1} if the
141     * list requires more than five words or contains registers that need
142     * more than a nibble to identify them.
143     *
144     * @param regs {@code non-null;} the register list in question
145     * @return {@code >= -1;} the number of words required, or {@code -1}
146     * if the list couldn't possibly fit in this format
147     */
148    private static int wordCount(RegisterSpecList regs) {
149        int sz = regs.size();
150
151        if (sz > MAX_NUM_OPS) {
152            // It can't possibly fit.
153            return -1;
154        }
155
156        int result = 0;
157
158        for (int i = 0; i < sz; i++) {
159            RegisterSpec one = regs.get(i);
160            result += one.getCategory();
161            /*
162             * The check below adds (category - 1) to the register, to
163             * account for the fact that the second half of a
164             * category-2 register has to be represented explicitly in
165             * the result.
166             */
167            if (!unsignedFitsInNibble(one.getReg() + one.getCategory() - 1)) {
168                return -1;
169            }
170        }
171
172        return (result <= MAX_NUM_OPS) ? result : -1;
173    }
174
175    /**
176     * Returns a register list which is equivalent to the given one,
177     * except that it splits category-2 registers into two explicit
178     * entries. This returns the original list if no modification is
179     * required
180     *
181     * @param orig {@code non-null;} the original list
182     * @return {@code non-null;} the list with the described transformation
183     */
184    private static RegisterSpecList explicitize(RegisterSpecList orig) {
185        int wordCount = wordCount(orig);
186        int sz = orig.size();
187
188        if (wordCount == sz) {
189            return orig;
190        }
191
192        RegisterSpecList result = new RegisterSpecList(wordCount);
193        int wordAt = 0;
194
195        for (int i = 0; i < sz; i++) {
196            RegisterSpec one = orig.get(i);
197            result.set(wordAt, one);
198            if (one.getCategory() == 2) {
199                result.set(wordAt + 1,
200                           RegisterSpec.make(one.getReg() + 1, Type.VOID));
201                wordAt += 2;
202            } else {
203                wordAt++;
204            }
205        }
206
207        result.setImmutable();
208        return result;
209    }
210}
211