src/arch/x86/predecoder.hh

   1 /*
   2  * Copyright (c) 2007 The Hewlett-Packard Development Company
   3  * All rights reserved.
   4  *
   5  * Redistribution and use of this software in source and binary forms,
   6  * with or without modification, are permitted provided that the
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   8  *
   9  * The software must be used only for Non-Commercial Use which means any
  10  * use which is NOT directed to receiving any direct monetary
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  12  * examples of non-commercial use are academic research, personal study,
  13  * teaching, education and corporate research & development.
  14  * Illustrative examples of commercial use are distributing products for
  15  * commercial advantage and providing services using the software for
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  17  *
  18  * If you wish to use this software or functionality therein that may be
  19  * covered by patents for commercial use, please contact:
  20  *     Director of Intellectual Property Licensing
  21  *     Office of Strategy and Technology
  22  *     Hewlett-Packard Company
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  31  * the COPYRIGHT HOLDER(s), HEWLETT-PACKARD COMPANY, nor the names of its
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  39  * and (ii) such Derivatives of the software include the above copyright
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  41  * applicable, this list of conditions and the disclaimer below.
  42  *
  43  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  44  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  45  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  46  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  47  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  48  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  49  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  50  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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  53  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  54  *
  55  * Authors: Gabe Black
  56  */
  57
  58 #ifndef __ARCH_X86_PREDECODER_HH__
  59 #define __ARCH_X86_PREDECODER_HH__
  60
  61 #include "arch/x86/types.hh"
  62 #include "base/bitfield.hh"
  63 #include "base/misc.hh"
  64 #include "base/trace.hh"
  65 #include "sim/host.hh"
  66
  67 class ThreadContext;
  68
  69 namespace X86ISA
  70 {
  71     class Predecoder
  72     {
  73       private:
  74         //These are defined and documented in predecoder_tables.cc
  75         static const uint8_t Prefixes[256];
  76         static const uint8_t UsesModRM[2][256];
  77         static const uint8_t ImmediateType[2][256];
  78         static const uint8_t SizeTypeToSize[3][10];
  79
  80       protected:
  81         ThreadContext * tc;
  82         //The bytes to be predecoded
  83         MachInst fetchChunk;
  84         //The pc of the start of fetchChunk
  85         Addr basePC;
  86         //The pc the current instruction started at
  87         Addr origPC;
  88         //The offset into fetchChunk of current processing
  89         int offset;
  90         //The extended machine instruction being generated
  91         ExtMachInst emi;
  92
  93         inline uint8_t getNextByte()
  94         {
  95             return (fetchChunk >> (offset * 8)) & 0xff;
  96         }
  97
  98         void getImmediate(int &collected, uint64_t &current, int size)
  99         {
 100             //Figure out how many bytes we still need to get for the
 101             //immediate.
 102             int toGet = size - collected;
 103             //Figure out how many bytes are left in our "buffer"
 104             int remaining = sizeof(MachInst) - offset;
 105             //Get as much as we need, up to the amount available.
 106             toGet = toGet > remaining ? remaining : toGet;
 107
 108             //Shift the bytes we want to be all the way to the right
 109             uint64_t partialImm = fetchChunk >> (offset * 8);
 110             //Mask off what we don't want
 111             partialImm &= mask(toGet * 8);
 112             //Shift it over to overlay with our displacement.
 113             partialImm <<= (immediateCollected * 8);
 114             //Put it into our displacement
 115             current |= partialImm;
 116             //Update how many bytes we've collected.
 117             collected += toGet;
 118             consumeBytes(toGet);
 119         }
 120
 121         inline void consumeByte()
 122         {
 123             offset++;
 124             assert(offset <= sizeof(MachInst));
 125             if(offset == sizeof(MachInst))
 126                 outOfBytes = true;
 127         }
 128
 129         inline void consumeBytes(int numBytes)
 130         {
 131             offset += numBytes;
 132             assert(offset <= sizeof(MachInst));
 133             if(offset == sizeof(MachInst))
 134                 outOfBytes = true;
 135         }
 136
 137         void reset();
 138
 139         //State machine state
 140       protected:
 141         //Whether or not we're out of bytes
 142         bool outOfBytes;
 143         //Whether we've completed generating an ExtMachInst
 144         bool emiIsReady;
 145         //The size of the displacement value
 146         int displacementSize;
 147         //The size of the immediate value
 148         int immediateSize;
 149         //This is how much of any immediate value we've gotten. This is used
 150         //for both the actual immediate and the displacement.
 151         int immediateCollected;
 152
 153         enum State {
 154             ResetState,
 155             PrefixState,
 156             OpcodeState,
 157             ModRMState,
 158             SIBState,
 159             DisplacementState,
 160             ImmediateState,
 161             //We should never get to this state. Getting here is an error.
 162             ErrorState
 163         };
 164
 165         State state;
 166
 167         //Functions to handle each of the states
 168         State doPrefixState(uint8_t);
 169         State doOpcodeState(uint8_t);
 170         State doModRMState(uint8_t);
 171         State doSIBState(uint8_t);
 172         State doDisplacementState();
 173         State doImmediateState();
 174
 175       public:
 176         Predecoder(ThreadContext * _tc) :
 177             tc(_tc), basePC(0), origPC(0), offset(0),
 178             outOfBytes(true), emiIsReady(false),
 179             state(ResetState)
 180         {
 181             emi.mode.mode = LongMode;
 182             emi.mode.submode = SixtyFourBitMode;
 183         }
 184
 185         ThreadContext * getTC()
 186         {
 187             return tc;
 188         }
 189
 190         void setTC(ThreadContext * _tc)
 191         {
 192             tc = _tc;
 193         }
 194
 195         void process();
 196
 197         //Use this to give data to the predecoder. This should be used
 198         //when there is control flow.
 199         void moreBytes(Addr pc, Addr fetchPC, MachInst data)
 200         {
 201             DPRINTF(Predecoder, "Getting more bytes.\n");
 202             basePC = fetchPC;
 203             offset = (fetchPC >= pc) ? 0 : pc - fetchPC;
 204             fetchChunk = data;
 205             outOfBytes = false;
 206             process();
 207         }
 208
 209         bool needMoreBytes()
 210         {
 211             return outOfBytes;
 212         }
 213
 214         bool extMachInstReady()
 215         {
 216             return emiIsReady;
 217         }
 218
 219         //This returns a constant reference to the ExtMachInst to avoid a copy
 220         const ExtMachInst & getExtMachInst()
 221         {
 222             assert(emiIsReady);
 223             emiIsReady = false;
 224             return emi;
 225         }
 226
 227         int getInstSize()
 228         {
 229             DPRINTF(Predecoder,
 230                     "Calculating the instruction size: "
 231                     "basePC: %#x offset: %#x origPC: %#x\n",
 232                     basePC, offset, origPC);
 233             return basePC + offset - origPC;
 234         }
 235     };
 236 };
 237
 238 #endif // __ARCH_X86_PREDECODER_HH__