src/arch/arm/decoder.cc

   1 /*
   2  * Copyright (c) 2012-2013 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
  49 namespace ArmISA
  50 {
  51
  52 GenericISA::BasicDecodeCache Decoder::defaultCache;
  53
  54 void
  55 Decoder::process()
  56 {
  57     // emi is typically ready, with some caveats below...
  58     instDone = true;
  59
  60     if (!emi.thumb) {
  61         emi.instBits = data;
  62         if (!emi.aarch64) {
  63             emi.sevenAndFour = bits(data, 7) && bits(data, 4);
  64             emi.isMisc = (bits(data, 24, 23) == 0x2 &&
  65                           bits(data, 20) == 0);
  66         }
  67         consumeBytes(4);
  68         DPRINTF(Decoder, "Arm inst: %#x.\n", (uint64_t)emi);
  69     } else {
  70         uint16_t word = (data >> (offset * 8));
  71         if (bigThumb) {
  72             // A 32 bit thumb inst is half collected.
  73             emi.instBits = emi.instBits | word;
  74             bigThumb = false;
  75             consumeBytes(2);
  76             DPRINTF(Decoder, "Second half of 32 bit Thumb: %#x.\n",
  77                     emi.instBits);
  78         } else {
  79             uint16_t highBits = word & 0xF800;
  80             if (highBits == 0xE800 || highBits == 0xF000 ||
  81                     highBits == 0xF800) {
  82                 // The start of a 32 bit thumb inst.
  83                 emi.bigThumb = 1;
  84                 if (offset == 0) {
  85                     // We've got the whole thing.
  86                     emi.instBits = (data >> 16) | (data << 16);
  87                     DPRINTF(Decoder, "All of 32 bit Thumb: %#x.\n",
  88                             emi.instBits);
  89                     consumeBytes(4);
  90                 } else {
  91                     // We only have the first half word.
  92                     DPRINTF(Decoder,
  93                             "First half of 32 bit Thumb.\n");
  94                     emi.instBits = (uint32_t)word << 16;
  95                     bigThumb = true;
  96                     consumeBytes(2);
  97                     // emi not ready yet.
  98                     instDone = false;
  99                 }
 100             } else {
 101                 // A 16 bit thumb inst.
 102                 consumeBytes(2);
 103                 emi.instBits = word;
 104                 // Set the condition code field artificially.
 105                 emi.condCode = COND_UC;
 106                 DPRINTF(Decoder, "16 bit Thumb: %#x.\n",
 107                         emi.instBits);
 108                 if (bits(word, 15, 8) == 0xbf &&
 109                         bits(word, 3, 0) != 0x0) {
 110                     foundIt = true;
 111                     itBits = bits(word, 7, 0);
 112                     DPRINTF(Decoder,
 113                             "IT detected, cond = %#x, mask = %#x\n",
 114                             itBits.cond, itBits.mask);
 115                 }
 116             }
 117         }
 118     }
 119 }
 120
 121 //Use this to give data to the decoder. This should be used
 122 //when there is control flow.
 123 void
 124 Decoder::moreBytes(const PCState &pc, Addr fetchPC, MachInst inst)
 125 {
 126     data = inst;
 127     offset = (fetchPC >= pc.instAddr()) ? 0 : pc.instAddr() - fetchPC;
 128     emi.thumb = pc.thumb();
 129     emi.aarch64 = pc.aarch64();
 130     emi.fpscrLen = fpscrLen;
 131     emi.fpscrStride = fpscrStride;
 132
 133     outOfBytes = false;
 134     process();
 135 }
 136
 137 }