decoder.hh revision 10924:d02e9c239892 
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 <vector>
36
37#include "arch/x86/regs/misc.hh"
38#include "arch/x86/types.hh"
39#include "base/bitfield.hh"
40#include "base/misc.hh"
41#include "base/trace.hh"
42#include "base/types.hh"
43#include "cpu/decode_cache.hh"
44#include "cpu/static_inst.hh"
45#include "debug/Decoder.hh"
46
47namespace X86ISA
48{
49
50class Decoder
51{
52  private:
53    //These are defined and documented in decoder_tables.cc
54    static const uint8_t SizeTypeToSize[3][10];
55    typedef const uint8_t ByteTable[256];
56    static ByteTable Prefixes;
57
58    static ByteTable UsesModRMOneByte;
59    static ByteTable UsesModRMTwoByte;
60    static ByteTable UsesModRMThreeByte0F38;
61    static ByteTable UsesModRMThreeByte0F3A;
62
63    static ByteTable ImmediateTypeOneByte;
64    static ByteTable ImmediateTypeTwoByte;
65    static ByteTable ImmediateTypeThreeByte0F38;
66    static ByteTable ImmediateTypeThreeByte0F3A;
67    static ByteTable ImmediateTypeVex[10];
68
69  protected:
70    struct InstBytes
71    {
72        StaticInstPtr si;
73        std::vector<MachInst> chunks;
74        std::vector<MachInst> masks;
75        int lastOffset;
76
77        InstBytes() : lastOffset(0)
78        {}
79    };
80
81    static InstBytes dummy;
82
83    //The bytes to be predecoded
84    MachInst fetchChunk;
85    InstBytes *instBytes;
86    int chunkIdx;
87    //The pc of the start of fetchChunk
88    Addr basePC;
89    //The pc the current instruction started at
90    Addr origPC;
91    //The offset into fetchChunk of current processing
92    int offset;
93    //The extended machine instruction being generated
94    ExtMachInst emi;
95    //Predecoding state
96    X86Mode mode;
97    X86SubMode submode;
98    uint8_t altOp;
99    uint8_t defOp;
100    uint8_t altAddr;
101    uint8_t defAddr;
102    uint8_t stack;
103
104    uint8_t getNextByte()
105    {
106        return ((uint8_t *)&fetchChunk)[offset];
107    }
108
109    void getImmediate(int &collected, uint64_t &current, int size)
110    {
111        //Figure out how many bytes we still need to get for the
112        //immediate.
113        int toGet = size - collected;
114        //Figure out how many bytes are left in our "buffer"
115        int remaining = sizeof(MachInst) - offset;
116        //Get as much as we need, up to the amount available.
117        toGet = toGet > remaining ? remaining : toGet;
118
119        //Shift the bytes we want to be all the way to the right
120        uint64_t partialImm = fetchChunk >> (offset * 8);
121        //Mask off what we don't want
122        partialImm &= mask(toGet * 8);
123        //Shift it over to overlay with our displacement.
124        partialImm <<= (immediateCollected * 8);
125        //Put it into our displacement
126        current |= partialImm;
127        //Update how many bytes we've collected.
128        collected += toGet;
129        consumeBytes(toGet);
130    }
131
132    void updateOffsetState()
133    {
134        assert(offset <= sizeof(MachInst));
135        if (offset == sizeof(MachInst)) {
136            DPRINTF(Decoder, "At the end of a chunk, idx = %d, chunks = %d.\n",
137                    chunkIdx, instBytes->chunks.size());
138            chunkIdx++;
139            if (chunkIdx == instBytes->chunks.size()) {
140                outOfBytes = true;
141            } else {
142                offset = 0;
143                fetchChunk = instBytes->chunks[chunkIdx];
144                basePC += sizeof(MachInst);
145            }
146        }
147    }
148
149    void consumeByte()
150    {
151        offset++;
152        updateOffsetState();
153    }
154
155    void consumeBytes(int numBytes)
156    {
157        offset += numBytes;
158        updateOffsetState();
159    }
160
161    //State machine state
162  protected:
163    //Whether or not we're out of bytes
164    bool outOfBytes;
165    //Whether we've completed generating an ExtMachInst
166    bool instDone;
167    //The size of the displacement value
168    int displacementSize;
169    //The size of the immediate value
170    int immediateSize;
171    //This is how much of any immediate value we've gotten. This is used
172    //for both the actual immediate and the displacement.
173    int immediateCollected;
174
175    enum State {
176        ResetState,
177        FromCacheState,
178        PrefixState,
179        TwoByteVexState,
180        ThreeByteVexFirstState,
181        ThreeByteVexSecondState,
182        OneByteOpcodeState,
183        TwoByteOpcodeState,
184        ThreeByte0F38OpcodeState,
185        ThreeByte0F3AOpcodeState,
186        ModRMState,
187        SIBState,
188        DisplacementState,
189        ImmediateState,
190        //We should never get to this state. Getting here is an error.
191        ErrorState
192    };
193
194    State state;
195
196    //Functions to handle each of the states
197    State doResetState();
198    State doFromCacheState();
199    State doPrefixState(uint8_t);
200    State doTwoByteVexState(uint8_t);
201    State doThreeByteVexFirstState(uint8_t);
202    State doThreeByteVexSecondState(uint8_t);
203    State doOneByteOpcodeState(uint8_t);
204    State doTwoByteOpcodeState(uint8_t);
205    State doThreeByte0F38OpcodeState(uint8_t);
206    State doThreeByte0F3AOpcodeState(uint8_t);
207    State doModRMState(uint8_t);
208    State doSIBState(uint8_t);
209    State doDisplacementState();
210    State doImmediateState();
211
212    //Process the actual opcode found earlier, using the supplied tables.
213    State processOpcode(ByteTable &immTable, ByteTable &modrmTable,
214                        bool addrSizedImm = false);
215    // Process the opcode found with VEX / XOP prefix.
216    State processExtendedOpcode(ByteTable &immTable);
217
218  protected:
219    /// Caching for decoded instruction objects.
220
221    typedef MiscReg CacheKey;
222
223    typedef DecodeCache::AddrMap<Decoder::InstBytes> DecodePages;
224    DecodePages *decodePages;
225    typedef m5::hash_map<CacheKey, DecodePages *> AddrCacheMap;
226    AddrCacheMap addrCacheMap;
227
228    DecodeCache::InstMap *instMap;
229    typedef m5::hash_map<CacheKey, DecodeCache::InstMap *> InstCacheMap;
230    static InstCacheMap instCacheMap;
231
232  public:
233    Decoder() : basePC(0), origPC(0), offset(0),
234        outOfBytes(true), instDone(false),
235        state(ResetState)
236    {
237        memset(&emi, 0, sizeof(emi));
238        mode = LongMode;
239        submode = SixtyFourBitMode;
240        emi.mode.mode = mode;
241        emi.mode.submode = submode;
242        altOp = 0;
243        defOp = 0;
244        altAddr = 0;
245        defAddr = 0;
246        stack = 0;
247        instBytes = &dummy;
248        decodePages = NULL;
249        instMap = NULL;
250    }
251
252    void setM5Reg(HandyM5Reg m5Reg)
253    {
254        mode = (X86Mode)(uint64_t)m5Reg.mode;
255        submode = (X86SubMode)(uint64_t)m5Reg.submode;
256        emi.mode.mode = mode;
257        emi.mode.submode = submode;
258        altOp = m5Reg.altOp;
259        defOp = m5Reg.defOp;
260        altAddr = m5Reg.altAddr;
261        defAddr = m5Reg.defAddr;
262        stack = m5Reg.stack;
263
264        AddrCacheMap::iterator amIter = addrCacheMap.find(m5Reg);
265        if (amIter != addrCacheMap.end()) {
266            decodePages = amIter->second;
267        } else {
268            decodePages = new DecodePages;
269            addrCacheMap[m5Reg] = decodePages;
270        }
271
272        InstCacheMap::iterator imIter = instCacheMap.find(m5Reg);
273        if (imIter != instCacheMap.end()) {
274            instMap = imIter->second;
275        } else {
276            instMap = new DecodeCache::InstMap;
277            instCacheMap[m5Reg] = instMap;
278        }
279    }
280
281    void takeOverFrom(Decoder *old)
282    {
283        mode = old->mode;
284        submode = old->submode;
285        emi.mode.mode = mode;
286        emi.mode.submode = submode;
287        altOp = old->altOp;
288        defOp = old->defOp;
289        altAddr = old->altAddr;
290        defAddr = old->defAddr;
291        stack = old->stack;
292    }
293
294    void reset()
295    {
296        state = ResetState;
297    }
298
299    void process();
300
301    //Use this to give data to the decoder. This should be used
302    //when there is control flow.
303    void moreBytes(const PCState &pc, Addr fetchPC, MachInst data)
304    {
305        DPRINTF(Decoder, "Getting more bytes.\n");
306        basePC = fetchPC;
307        offset = (fetchPC >= pc.instAddr()) ? 0 : pc.instAddr() - fetchPC;
308        fetchChunk = data;
309        outOfBytes = false;
310        process();
311    }
312
313    bool needMoreBytes()
314    {
315        return outOfBytes;
316    }
317
318    bool instReady()
319    {
320        return instDone;
321    }
322
323    void
324    updateNPC(X86ISA::PCState &nextPC)
325    {
326        if (!nextPC.size()) {
327            int size = basePC + offset - origPC;
328            DPRINTF(Decoder,
329                    "Calculating the instruction size: "
330                    "basePC: %#x offset: %#x origPC: %#x size: %d\n",
331                    basePC, offset, origPC, size);
332            nextPC.size(size);
333            nextPC.npc(nextPC.pc() + size);
334        }
335    }
336
337  public:
338    StaticInstPtr decodeInst(ExtMachInst mach_inst);
339
340    /// Decode a machine instruction.
341    /// @param mach_inst The binary instruction to decode.
342    /// @retval A pointer to the corresponding StaticInst object.
343    StaticInstPtr decode(ExtMachInst mach_inst, Addr addr);
344    StaticInstPtr decode(X86ISA::PCState &nextPC);
345};
346
347} // namespace X86ISA
348
349#endif // __ARCH_X86_DECODER_HH__
350