1/*
2 * Copyright (c) 2012-2014,2018 ARM Limited
3 * All rights reserved
4 *
5 * The license below extends only to copyright in the software and shall
6 * not be construed as granting a license to any other intellectual
7 * property including but not limited to intellectual property relating
8 * to a hardware implementation of the functionality of the software
9 * licensed hereunder. You may use the software subject to the license
10 * terms below provided that you ensure that this notice is replicated
11 * unmodified and in its entirety in all distributions of the software,
12 * modified or unmodified, in source code or in binary form.
13 *
14 * Copyright (c) 2012 Google
15 * All rights reserved.
16 *
17 * Redistribution and use in source and binary forms, with or without
18 * modification, are permitted provided that the following conditions are
19 * met: redistributions of source code must retain the above copyright
20 * notice, this list of conditions and the following disclaimer;
21 * redistributions in binary form must reproduce the above copyright
22 * notice, this list of conditions and the following disclaimer in the
23 * documentation and/or other materials provided with the distribution;
24 * neither the name of the copyright holders nor the names of its
25 * contributors may be used to endorse or promote products derived from
26 * this software without specific prior written permission.
27 *
28 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
29 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
30 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
31 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
32 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
33 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
34 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
35 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
36 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
37 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
38 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
39 *
40 * Authors: Gabe Black
41 */
42
43#include "arch/arm/decoder.hh"
44
45#include "arch/arm/isa.hh"
46#include "arch/arm/isa_traits.hh"
47#include "arch/arm/utility.hh"
48#include "base/trace.hh"
49#include "debug/Decoder.hh"
50
51namespace ArmISA
52{
53
54GenericISA::BasicDecodeCache Decoder::defaultCache;
55
56Decoder::Decoder(ISA* isa)
57 : data(0), fpscrLen(0), fpscrStride(0), decoderFlavour(isa
58 ? isa->decoderFlavour()
59 : Enums::Generic)
60{
61 reset();
62}
63
64void
65Decoder::reset()
66{
67 bigThumb = false;
68 offset = 0;
69 emi = 0;
70 instDone = false;
71 outOfBytes = true;
72 foundIt = false;
73}
74
75void
76Decoder::process()
77{
78 // emi is typically ready, with some caveats below...
79 instDone = true;
80
81 if (!emi.thumb) {
82 emi.instBits = data;
83 if (!emi.aarch64) {
84 emi.sevenAndFour = bits(data, 7) && bits(data, 4);
85 emi.isMisc = (bits(data, 24, 23) == 0x2 &&
86 bits(data, 20) == 0);
87 }
88 consumeBytes(4);
89 DPRINTF(Decoder, "Arm inst: %#x.\n", (uint64_t)emi);
90 } else {
91 uint16_t word = (data >> (offset * 8));
92 if (bigThumb) {
93 // A 32 bit thumb inst is half collected.
94 emi.instBits = emi.instBits | word;
95 bigThumb = false;
96 consumeBytes(2);
97 DPRINTF(Decoder, "Second half of 32 bit Thumb: %#x.\n",
98 emi.instBits);
99 } else {
100 uint16_t highBits = word & 0xF800;
101 if (highBits == 0xE800 || highBits == 0xF000 ||
102 highBits == 0xF800) {
103 // The start of a 32 bit thumb inst.
104 emi.bigThumb = 1;
105 if (offset == 0) {
106 // We've got the whole thing.
107 emi.instBits = (data >> 16) | (data << 16);
108 DPRINTF(Decoder, "All of 32 bit Thumb: %#x.\n",
109 emi.instBits);
110 consumeBytes(4);
111 } else {
112 // We only have the first half word.
113 DPRINTF(Decoder,
114 "First half of 32 bit Thumb.\n");
115 emi.instBits = (uint32_t)word << 16;
116 bigThumb = true;
117 consumeBytes(2);
118 // emi not ready yet.
119 instDone = false;
120 }
121 } else {
122 // A 16 bit thumb inst.
123 consumeBytes(2);
124 emi.instBits = word;
125 // Set the condition code field artificially.
126 emi.condCode = COND_UC;
127 DPRINTF(Decoder, "16 bit Thumb: %#x.\n",
128 emi.instBits);
129 if (bits(word, 15, 8) == 0xbf &&
130 bits(word, 3, 0) != 0x0) {
131 foundIt = true;
132 itBits = bits(word, 7, 0);
133 DPRINTF(Decoder,
134 "IT detected, cond = %#x, mask = %#x\n",
135 itBits.cond, itBits.mask);
136 }
137 }
138 }
139 }
140}
141
142void
143Decoder::consumeBytes(int numBytes)
144{
145 offset += numBytes;
146 assert(offset <= sizeof(MachInst) || emi.decoderFault);
147 if (offset == sizeof(MachInst))
148 outOfBytes = true;
149}
150
151void
152Decoder::moreBytes(const PCState &pc, Addr fetchPC, MachInst inst)
153{
154 data = inst;
155 offset = (fetchPC >= pc.instAddr()) ? 0 : pc.instAddr() - fetchPC;
156 emi.thumb = pc.thumb();
157 emi.aarch64 = pc.aarch64();
158 emi.fpscrLen = fpscrLen;
159 emi.fpscrStride = fpscrStride;
160
161 const Addr alignment(pc.thumb() ? 0x1 : 0x3);
162 emi.decoderFault = static_cast<uint8_t>(
163 pc.instAddr() & alignment ? DecoderFault::UNALIGNED : DecoderFault::OK);
164
165 outOfBytes = false;
166 process();
167}
168
169StaticInstPtr
170Decoder::decode(ArmISA::PCState &pc)
171{
172 if (!instDone)
173 return NULL;
174
175 const int inst_size((!emi.thumb || emi.bigThumb) ? 4 : 2);
176 ExtMachInst this_emi(emi);
177
178 pc.npc(pc.pc() + inst_size);
179 if (foundIt)
180 pc.nextItstate(itBits);
181 this_emi.itstate = pc.itstate();
182 this_emi.illegalExecution = pc.illegalExec() ? 1 : 0;
183
184 pc.size(inst_size);
185
186 emi = 0;
187 instDone = false;
188 foundIt = false;
189
190 return decode(this_emi, pc.instAddr());
191}
192
193}