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 ISA;
43class Decoder
44{
45  protected:
46    // The extended machine instruction being generated
47    ExtMachInst ext_inst;
48    bool instDone;
49
50  public:
51    Decoder(ISA* isa = nullptr) : instDone(false)
52    {}
53
54    void
55    process()
56    { }
57
58    void
59    reset()
60    {
61        instDone = false;
62    }
63
64    // Use this to give data to the predecoder. This should be used
65    // when there is control flow.
66    void
67    moreBytes(const PCState &pc, Addr fetchPC, MachInst inst)
68    {
69        ext_inst = inst;
70        instDone = true;
71        if (FullSystem)
72            ext_inst |= (static_cast<ExtMachInst>(pc.pc() & 0x1) << 32);
73    }
74
75    bool
76    needMoreBytes()
77    {
78        return true;
79    }
80
81    bool
82    instReady()
83    {
84        return instDone;
85    }
86
87    void takeOverFrom(Decoder * old) {}
88
89  protected:
90    /// A cache of decoded instruction objects.
91    static GenericISA::BasicDecodeCache defaultCache;
92
93  public:
94    StaticInstPtr decodeInst(ExtMachInst mach_inst);
95
96    /// Decode a machine instruction.
97    /// @param mach_inst The binary instruction to decode.
98    /// @retval A pointer to the corresponding StaticInst object.
99    StaticInstPtr
100    decode(ExtMachInst mach_inst, Addr addr)
101    {
102        return defaultCache.decode(this, mach_inst, addr);
103    }
104
105    StaticInstPtr
106    decode(AlphaISA::PCState &nextPC)
107    {
108        if (!instDone)
109            return NULL;
110        instDone = false;
111        return decode(ext_inst, nextPC.instAddr());
112    }
113};
114
115} // namespace AlphaISA
116
117#endif // __ARCH_ALPHA_DECODER_HH__
118