decoder.cc revision 12763:37c243ed1112
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} 194