decoder.hh revision 9478:ba80f7d4f452 
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_ALPHA_DECODER_HH__
32#define __ARCH_ALPHA_DECODER_HH__
33
34#include "arch/generic/decode_cache.hh"
35#include "arch/types.hh"
36#include "cpu/static_inst.hh"
37#include "sim/full_system.hh"
38
39namespace AlphaISA
40{
41
42class Decoder
43{
44  protected:
45    // The extended machine instruction being generated
46    ExtMachInst ext_inst;
47    bool instDone;
48
49  public:
50    Decoder() : instDone(false)
51    {}
52
53    void
54    process()
55    { }
56
57    void
58    reset()
59    {
60        instDone = false;
61    }
62
63    // Use this to give data to the predecoder. This should be used
64    // when there is control flow.
65    void
66    moreBytes(const PCState &pc, Addr fetchPC, MachInst inst)
67    {
68        ext_inst = inst;
69        instDone = true;
70        if (FullSystem)
71            ext_inst |= (static_cast<ExtMachInst>(pc.pc() & 0x1) << 32);
72    }
73
74    bool
75    needMoreBytes()
76    {
77        return true;
78    }
79
80    bool
81    instReady()
82    {
83        return instDone;
84    }
85
86    void takeOverFrom(Decoder * old) {}
87
88  protected:
89    /// A cache of decoded instruction objects.
90    static GenericISA::BasicDecodeCache defaultCache;
91
92  public:
93    StaticInstPtr decodeInst(ExtMachInst mach_inst);
94
95    /// Decode a machine instruction.
96    /// @param mach_inst The binary instruction to decode.
97    /// @retval A pointer to the corresponding StaticInst object.
98    StaticInstPtr
99    decode(ExtMachInst mach_inst, Addr addr)
100    {
101        return defaultCache.decode(this, mach_inst, addr);
102    }
103
104    StaticInstPtr
105    decode(AlphaISA::PCState &nextPC)
106    {
107        if (!instDone)
108            return NULL;
109        instDone = false;
110        return decode(ext_inst, nextPC.instAddr());
111    }
112};
113
114} // namespace AlphaISA
115
116#endif // __ARCH_ALPHA_DECODER_HH__
117