src/arch/arm/predecoder.cc

   1 /*
   2  * Copyright (c) 2010 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) 2006 The Regents of The University of Michigan
  15  * Copyright (c) 2007-2008 The Florida State University
  16  * All rights reserved.
  17  *
  18  * Redistribution and use in source and binary forms, with or without
  19  * modification, are permitted provided that the following conditions are
  20  * met: redistributions of source code must retain the above copyright
  21  * notice, this list of conditions and the following disclaimer;
  22  * redistributions in binary form must reproduce the above copyright
  23  * notice, this list of conditions and the following disclaimer in the
  24  * documentation and/or other materials provided with the distribution;
  25  * neither the name of the copyright holders nor the names of its
  26  * contributors may be used to endorse or promote products derived from
  27  * this software without specific prior written permission.
  28  *
  29  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  30  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  31  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  32  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  33  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  34  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  35  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  36  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  37  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  38  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  39  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  40  *
  41  * Authors: Gabe Black
  42  */
  43
  44 #include "arch/arm/isa_traits.hh"
  45 #include "arch/arm/predecoder.hh"
  46 #include "arch/arm/utility.hh"
  47 #include "base/trace.hh"
  48 #include "cpu/thread_context.hh"
  49 #include "debug/Predecoder.hh"
  50
  51 namespace ArmISA
  52 {
  53
  54 void
  55 Predecoder::process()
  56 {
  57     // emi is typically ready, with some caveats below...
  58     emiReady = true;
  59
  60     if (!emi.thumb) {
  61         emi.instBits = data;
  62         emi.sevenAndFour = bits(data, 7) && bits(data, 4);
  63         emi.isMisc = (bits(data, 24, 23) == 0x2 &&
  64                       bits(data, 20) == 0);
  65         consumeBytes(4);
  66         DPRINTF(Predecoder, "Arm inst: %#x.\n", (uint64_t)emi);
  67     } else {
  68         uint16_t word = (data >> (offset * 8));
  69         if (bigThumb) {
  70             // A 32 bit thumb inst is half collected.
  71             emi.instBits = emi.instBits | word;
  72             bigThumb = false;
  73             consumeBytes(2);
  74             DPRINTF(Predecoder, "Second half of 32 bit Thumb: %#x.\n",
  75                     emi.instBits);
  76         } else {
  77             uint16_t highBits = word & 0xF800;
  78             if (highBits == 0xE800 || highBits == 0xF000 ||
  79                     highBits == 0xF800) {
  80                 // The start of a 32 bit thumb inst.
  81                 emi.bigThumb = 1;
  82                 if (offset == 0) {
  83                     // We've got the whole thing.
  84                     emi.instBits = (data >> 16) | (data << 16);
  85                     DPRINTF(Predecoder, "All of 32 bit Thumb: %#x.\n",
  86                             emi.instBits);
  87                     consumeBytes(4);
  88                 } else {
  89                     // We only have the first half word.
  90                     DPRINTF(Predecoder,
  91                             "First half of 32 bit Thumb.\n");
  92                     emi.instBits = (uint32_t)word << 16;
  93                     bigThumb = true;
  94                     consumeBytes(2);
  95                     // emi not ready yet.
  96                     emiReady = false;
  97                 }
  98             } else {
  99                 // A 16 bit thumb inst.
 100                 consumeBytes(2);
 101                 emi.instBits = word;
 102                 // Set the condition code field artificially.
 103                 emi.condCode = COND_UC;
 104                 DPRINTF(Predecoder, "16 bit Thumb: %#x.\n",
 105                         emi.instBits);
 106                 if (bits(word, 15, 8) == 0xbf &&
 107                         bits(word, 3, 0) != 0x0) {
 108                     foundIt = true;
 109                     itBits = bits(word, 7, 0);
 110                     DPRINTF(Predecoder,
 111                             "IT detected, cond = %#x, mask = %#x\n",
 112                             itBits.cond, itBits.mask);
 113                 }
 114             }
 115         }
 116     }
 117 }
 118
 119 //Use this to give data to the predecoder. This should be used
 120 //when there is control flow.
 121 void
 122 Predecoder::moreBytes(const PCState &pc, Addr fetchPC, MachInst inst)
 123 {
 124     data = inst;
 125     offset = (fetchPC >= pc.instAddr()) ? 0 : pc.instAddr() - fetchPC;
 126     emi.thumb = pc.thumb();
 127     FPSCR fpscr = tc->readMiscReg(MISCREG_FPSCR);
 128     emi.fpscrLen = fpscr.len;
 129     emi.fpscrStride = fpscr.stride;
 130
 131     outOfBytes = false;
 132     process();
 133 }
 134
 135 }