decoder.hh revision 11168:f98eb2da15a4 
1/*
2 * Copyright (c) 2012 Google
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are
7 * met: redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer;
9 * redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution;
12 * neither the name of the copyright holders nor the names of its
13 * contributors may be used to endorse or promote products derived from
14 * this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
17 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
18 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
19 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
20 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
21 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
22 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
26 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 *
28 * Authors: Gabe Black
29 */
30
31#ifndef __ARCH_X86_DECODER_HH__
32#define __ARCH_X86_DECODER_HH__
33
34#include <cassert>
35#include <unordered_map>
36#include <vector>
37
38#include "arch/x86/regs/misc.hh"
39#include "arch/x86/types.hh"
40#include "base/bitfield.hh"
41#include "base/misc.hh"
42#include "base/trace.hh"
43#include "base/types.hh"
44#include "cpu/decode_cache.hh"
45#include "cpu/static_inst.hh"
46#include "debug/Decoder.hh"
47
48namespace X86ISA
49{
50
51class ISA;
52class Decoder
53{
54  private:
55    //These are defined and documented in decoder_tables.cc
56    static const uint8_t SizeTypeToSize[3][10];
57    typedef const uint8_t ByteTable[256];
58    static ByteTable Prefixes;
59
60    static ByteTable UsesModRMOneByte;
61    static ByteTable UsesModRMTwoByte;
62    static ByteTable UsesModRMThreeByte0F38;
63    static ByteTable UsesModRMThreeByte0F3A;
64
65    static ByteTable ImmediateTypeOneByte;
66    static ByteTable ImmediateTypeTwoByte;
67    static ByteTable ImmediateTypeThreeByte0F38;
68    static ByteTable ImmediateTypeThreeByte0F3A;
69    static ByteTable ImmediateTypeVex[10];
70
71  protected:
72    struct InstBytes
73    {
74        StaticInstPtr si;
75        std::vector<MachInst> chunks;
76        std::vector<MachInst> masks;
77        int lastOffset;
78
79        InstBytes() : lastOffset(0)
80        {}
81    };
82
83    static InstBytes dummy;
84
85    //The bytes to be predecoded
86    MachInst fetchChunk;
87    InstBytes *instBytes;
88    int chunkIdx;
89    //The pc of the start of fetchChunk
90    Addr basePC;
91    //The pc the current instruction started at
92    Addr origPC;
93    //The offset into fetchChunk of current processing
94    int offset;
95    //The extended machine instruction being generated
96    ExtMachInst emi;
97    //Predecoding state
98    X86Mode mode;
99    X86SubMode submode;
100    uint8_t altOp;
101    uint8_t defOp;
102    uint8_t altAddr;
103    uint8_t defAddr;
104    uint8_t stack;
105
106    uint8_t getNextByte()
107    {
108        return ((uint8_t *)&fetchChunk)[offset];
109    }
110
111    void getImmediate(int &collected, uint64_t &current, int size)
112    {
113        //Figure out how many bytes we still need to get for the
114        //immediate.
115        int toGet = size - collected;
116        //Figure out how many bytes are left in our "buffer"
117        int remaining = sizeof(MachInst) - offset;
118        //Get as much as we need, up to the amount available.
119        toGet = toGet > remaining ? remaining : toGet;
120
121        //Shift the bytes we want to be all the way to the right
122        uint64_t partialImm = fetchChunk >> (offset * 8);
123        //Mask off what we don't want
124        partialImm &= mask(toGet * 8);
125        //Shift it over to overlay with our displacement.
126        partialImm <<= (immediateCollected * 8);
127        //Put it into our displacement
128        current |= partialImm;
129        //Update how many bytes we've collected.
130        collected += toGet;
131        consumeBytes(toGet);
132    }
133
134    void updateOffsetState()
135    {
136        assert(offset <= sizeof(MachInst));
137        if (offset == sizeof(MachInst)) {
138            DPRINTF(Decoder, "At the end of a chunk, idx = %d, chunks = %d.\n",
139                    chunkIdx, instBytes->chunks.size());
140            chunkIdx++;
141            if (chunkIdx == instBytes->chunks.size()) {
142                outOfBytes = true;
143            } else {
144                offset = 0;
145                fetchChunk = instBytes->chunks[chunkIdx];
146                basePC += sizeof(MachInst);
147            }
148        }
149    }
150
151    void consumeByte()
152    {
153        offset++;
154        updateOffsetState();
155    }
156
157    void consumeBytes(int numBytes)
158    {
159        offset += numBytes;
160        updateOffsetState();
161    }
162
163    //State machine state
164  protected:
165    //Whether or not we're out of bytes
166    bool outOfBytes;
167    //Whether we've completed generating an ExtMachInst
168    bool instDone;
169    //The size of the displacement value
170    int displacementSize;
171    //The size of the immediate value
172    int immediateSize;
173    //This is how much of any immediate value we've gotten. This is used
174    //for both the actual immediate and the displacement.
175    int immediateCollected;
176
177    enum State {
178        ResetState,
179        FromCacheState,
180        PrefixState,
181        TwoByteVexState,
182        ThreeByteVexFirstState,
183        ThreeByteVexSecondState,
184        OneByteOpcodeState,
185        TwoByteOpcodeState,
186        ThreeByte0F38OpcodeState,
187        ThreeByte0F3AOpcodeState,
188        ModRMState,
189        SIBState,
190        DisplacementState,
191        ImmediateState,
192        //We should never get to this state. Getting here is an error.
193        ErrorState
194    };
195
196    State state;
197
198    //Functions to handle each of the states
199    State doResetState();
200    State doFromCacheState();
201    State doPrefixState(uint8_t);
202    State doTwoByteVexState(uint8_t);
203    State doThreeByteVexFirstState(uint8_t);
204    State doThreeByteVexSecondState(uint8_t);
205    State doOneByteOpcodeState(uint8_t);
206    State doTwoByteOpcodeState(uint8_t);
207    State doThreeByte0F38OpcodeState(uint8_t);
208    State doThreeByte0F3AOpcodeState(uint8_t);
209    State doModRMState(uint8_t);
210    State doSIBState(uint8_t);
211    State doDisplacementState();
212    State doImmediateState();
213
214    //Process the actual opcode found earlier, using the supplied tables.
215    State processOpcode(ByteTable &immTable, ByteTable &modrmTable,
216                        bool addrSizedImm = false);
217    // Process the opcode found with VEX / XOP prefix.
218    State processExtendedOpcode(ByteTable &immTable);
219
220  protected:
221    /// Caching for decoded instruction objects.
222
223    typedef MiscReg CacheKey;
224
225    typedef DecodeCache::AddrMap<Decoder::InstBytes> DecodePages;
226    DecodePages *decodePages;
227    typedef std::unordered_map<CacheKey, DecodePages *> AddrCacheMap;
228    AddrCacheMap addrCacheMap;
229
230    DecodeCache::InstMap *instMap;
231    typedef std::unordered_map<CacheKey, DecodeCache::InstMap *> InstCacheMap;
232    static InstCacheMap instCacheMap;
233
234  public:
235    Decoder(ISA* isa = nullptr) : basePC(0), origPC(0), offset(0),
236        outOfBytes(true), instDone(false),
237        state(ResetState)
238    {
239        memset(&emi, 0, sizeof(emi));
240        mode = LongMode;
241        submode = SixtyFourBitMode;
242        emi.mode.mode = mode;
243        emi.mode.submode = submode;
244        altOp = 0;
245        defOp = 0;
246        altAddr = 0;
247        defAddr = 0;
248        stack = 0;
249        instBytes = &dummy;
250        decodePages = NULL;
251        instMap = NULL;
252    }
253
254    void setM5Reg(HandyM5Reg m5Reg)
255    {
256        mode = (X86Mode)(uint64_t)m5Reg.mode;
257        submode = (X86SubMode)(uint64_t)m5Reg.submode;
258        emi.mode.mode = mode;
259        emi.mode.submode = submode;
260        altOp = m5Reg.altOp;
261        defOp = m5Reg.defOp;
262        altAddr = m5Reg.altAddr;
263        defAddr = m5Reg.defAddr;
264        stack = m5Reg.stack;
265
266        AddrCacheMap::iterator amIter = addrCacheMap.find(m5Reg);
267        if (amIter != addrCacheMap.end()) {
268            decodePages = amIter->second;
269        } else {
270            decodePages = new DecodePages;
271            addrCacheMap[m5Reg] = decodePages;
272        }
273
274        InstCacheMap::iterator imIter = instCacheMap.find(m5Reg);
275        if (imIter != instCacheMap.end()) {
276            instMap = imIter->second;
277        } else {
278            instMap = new DecodeCache::InstMap;
279            instCacheMap[m5Reg] = instMap;
280        }
281    }
282
283    void takeOverFrom(Decoder *old)
284    {
285        mode = old->mode;
286        submode = old->submode;
287        emi.mode.mode = mode;
288        emi.mode.submode = submode;
289        altOp = old->altOp;
290        defOp = old->defOp;
291        altAddr = old->altAddr;
292        defAddr = old->defAddr;
293        stack = old->stack;
294    }
295
296    void reset()
297    {
298        state = ResetState;
299    }
300
301    void process();
302
303    //Use this to give data to the decoder. This should be used
304    //when there is control flow.
305    void moreBytes(const PCState &pc, Addr fetchPC, MachInst data)
306    {
307        DPRINTF(Decoder, "Getting more bytes.\n");
308        basePC = fetchPC;
309        offset = (fetchPC >= pc.instAddr()) ? 0 : pc.instAddr() - fetchPC;
310        fetchChunk = data;
311        outOfBytes = false;
312        process();
313    }
314
315    bool needMoreBytes()
316    {
317        return outOfBytes;
318    }
319
320    bool instReady()
321    {
322        return instDone;
323    }
324
325    void
326    updateNPC(X86ISA::PCState &nextPC)
327    {
328        if (!nextPC.size()) {
329            int size = basePC + offset - origPC;
330            DPRINTF(Decoder,
331                    "Calculating the instruction size: "
332                    "basePC: %#x offset: %#x origPC: %#x size: %d\n",
333                    basePC, offset, origPC, size);
334            nextPC.size(size);
335            nextPC.npc(nextPC.pc() + size);
336        }
337    }
338
339  public:
340    StaticInstPtr decodeInst(ExtMachInst mach_inst);
341
342    /// Decode a machine instruction.
343    /// @param mach_inst The binary instruction to decode.
344    /// @retval A pointer to the corresponding StaticInst object.
345    StaticInstPtr decode(ExtMachInst mach_inst, Addr addr);
346    StaticInstPtr decode(X86ISA::PCState &nextPC);
347};
348
349} // namespace X86ISA
350
351#endif // __ARCH_X86_DECODER_HH__
352