decoder.cc revision 10610
1/* 2 * Copyright (c) 2012-2014 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#include "arch/arm/isa_traits.hh" 45#include "arch/arm/utility.hh" 46#include "base/trace.hh" 47#include "debug/Decoder.hh" 48 49namespace ArmISA 50{ 51 52GenericISA::BasicDecodeCache Decoder::defaultCache; 53 54Decoder::Decoder() 55 : data(0), fpscrLen(0), fpscrStride(0) 56{ 57 reset(); 58} 59 60void 61Decoder::reset() 62{ 63 bigThumb = false; 64 offset = 0; 65 emi = 0; 66 instDone = false; 67 outOfBytes = true; 68 foundIt = false; 69} 70 71void 72Decoder::process() 73{ 74 // emi is typically ready, with some caveats below... 75 instDone = true; 76 77 if (!emi.thumb) { 78 emi.instBits = data; 79 if (!emi.aarch64) { 80 emi.sevenAndFour = bits(data, 7) && bits(data, 4); 81 emi.isMisc = (bits(data, 24, 23) == 0x2 && 82 bits(data, 20) == 0); 83 } 84 consumeBytes(4); 85 DPRINTF(Decoder, "Arm inst: %#x.\n", (uint64_t)emi); 86 } else { 87 uint16_t word = (data >> (offset * 8)); 88 if (bigThumb) { 89 // A 32 bit thumb inst is half collected. 90 emi.instBits = emi.instBits | word; 91 bigThumb = false; 92 consumeBytes(2); 93 DPRINTF(Decoder, "Second half of 32 bit Thumb: %#x.\n", 94 emi.instBits); 95 } else { 96 uint16_t highBits = word & 0xF800; 97 if (highBits == 0xE800 || highBits == 0xF000 || 98 highBits == 0xF800) { 99 // The start of a 32 bit thumb inst. 100 emi.bigThumb = 1; 101 if (offset == 0) { 102 // We've got the whole thing. 103 emi.instBits = (data >> 16) | (data << 16); 104 DPRINTF(Decoder, "All of 32 bit Thumb: %#x.\n", 105 emi.instBits); 106 consumeBytes(4); 107 } else { 108 // We only have the first half word. 109 DPRINTF(Decoder, 110 "First half of 32 bit Thumb.\n"); 111 emi.instBits = (uint32_t)word << 16; 112 bigThumb = true; 113 consumeBytes(2); 114 // emi not ready yet. 115 instDone = false; 116 } 117 } else { 118 // A 16 bit thumb inst. 119 consumeBytes(2); 120 emi.instBits = word; 121 // Set the condition code field artificially. 122 emi.condCode = COND_UC; 123 DPRINTF(Decoder, "16 bit Thumb: %#x.\n", 124 emi.instBits); 125 if (bits(word, 15, 8) == 0xbf && 126 bits(word, 3, 0) != 0x0) { 127 foundIt = true; 128 itBits = bits(word, 7, 0); 129 DPRINTF(Decoder, 130 "IT detected, cond = %#x, mask = %#x\n", 131 itBits.cond, itBits.mask); 132 } 133 } 134 } 135 } 136} 137 138void 139Decoder::consumeBytes(int numBytes) 140{ 141 offset += numBytes; 142 assert(offset <= sizeof(MachInst)); 143 if (offset == sizeof(MachInst)) 144 outOfBytes = true; 145} 146 147void 148Decoder::moreBytes(const PCState &pc, Addr fetchPC, MachInst inst) 149{ 150 data = inst; 151 offset = (fetchPC >= pc.instAddr()) ? 0 : pc.instAddr() - fetchPC; 152 emi.thumb = pc.thumb(); 153 emi.aarch64 = pc.aarch64(); 154 emi.fpscrLen = fpscrLen; 155 emi.fpscrStride = fpscrStride; 156 157 outOfBytes = false; 158 process(); 159} 160 161StaticInstPtr 162Decoder::decode(ArmISA::PCState &pc) 163{ 164 if (!instDone) 165 return NULL; 166 167 const int inst_size((!emi.thumb || emi.bigThumb) ? 4 : 2); 168 ExtMachInst this_emi(emi); 169 170 pc.npc(pc.pc() + inst_size); 171 if (foundIt) 172 pc.nextItstate(itBits); 173 this_emi.itstate = pc.itstate(); 174 pc.size(inst_size); 175 176 emi = 0; 177 instDone = false; 178 foundIt = false; 179 180 return decode(this_emi, pc.instAddr()); 181} 182 183} 184