decoder.hh revision 9023:e9201a7bce59 
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_ARM_DECODER_HH__
32#define __ARCH_ARM_DECODER_HH__
33
34#include <cassert>
35
36#include "arch/arm/miscregs.hh"
37#include "arch/arm/types.hh"
38#include "base/types.hh"
39#include "cpu/decode_cache.hh"
40
41class ThreadContext;
42
43namespace ArmISA
44{
45
46class Decoder
47{
48  protected:
49    ThreadContext * tc;
50    //The extended machine instruction being generated
51    ExtMachInst emi;
52    MachInst data;
53    bool bigThumb;
54    bool instDone;
55    bool outOfBytes;
56    int offset;
57    bool foundIt;
58    ITSTATE itBits;
59
60  public:
61    void reset()
62    {
63        bigThumb = false;
64        offset = 0;
65        emi = 0;
66        instDone = false;
67        outOfBytes = true;
68        foundIt = false;
69    }
70
71    Decoder(ThreadContext * _tc) : tc(_tc), data(0)
72    {
73        reset();
74    }
75
76    ThreadContext * getTC()
77    {
78        return tc;
79    }
80
81    void
82    setTC(ThreadContext * _tc)
83    {
84        tc = _tc;
85    }
86
87    void process();
88
89    //Use this to give data to the decoder. This should be used
90    //when there is control flow.
91    void moreBytes(const PCState &pc, Addr fetchPC, MachInst inst);
92
93    //Use this to give data to the decoder. This should be used
94    //when instructions are executed in order.
95    void moreBytes(MachInst machInst)
96    {
97        moreBytes(0, 0, machInst);
98    }
99
100    inline void consumeBytes(int numBytes)
101    {
102        offset += numBytes;
103        assert(offset <= sizeof(MachInst));
104        if (offset == sizeof(MachInst))
105            outOfBytes = true;
106    }
107
108    bool needMoreBytes() const
109    {
110        return outOfBytes;
111    }
112
113    bool instReady() const
114    {
115        return instDone;
116    }
117
118    int getInstSize() const
119    {
120        return (!emi.thumb || emi.bigThumb) ? 4 : 2;
121    }
122
123  protected:
124    /// A cache of decoded instruction objects.
125    static DecodeCache defaultCache;
126
127  public:
128    StaticInstPtr decodeInst(ExtMachInst mach_inst);
129
130    /// Decode a machine instruction.
131    /// @param mach_inst The binary instruction to decode.
132    /// @retval A pointer to the corresponding StaticInst object.
133    StaticInstPtr
134    decode(ExtMachInst mach_inst, Addr addr)
135    {
136        return defaultCache.decode(this, mach_inst, addr);
137    }
138
139    StaticInstPtr
140    decode(ArmISA::PCState &nextPC)
141    {
142        if (!instDone)
143            return NULL;
144
145        assert(instDone);
146        ExtMachInst thisEmi = emi;
147        nextPC.npc(nextPC.pc() + getInstSize());
148        if (foundIt)
149            nextPC.nextItstate(itBits);
150        thisEmi.itstate = nextPC.itstate();
151        nextPC.size(getInstSize());
152        emi = 0;
153        instDone = false;
154        foundIt = false;
155        return decode(thisEmi, nextPC.instAddr());
156    }
157};
158
159} // namespace ArmISA
160
161#endif // __ARCH_ARM_DECODER_HH__
162