decoder.hh revision 9478 
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_SPARC_DECODER_HH__
32#define __ARCH_SPARC_DECODER_HH__
33
34#include "arch/generic/decode_cache.hh"
35#include "arch/sparc/registers.hh"
36#include "arch/types.hh"
37#include "cpu/static_inst.hh"
38
39namespace SparcISA
40{
41
42class Decoder
43{
44  protected:
45    // The extended machine instruction being generated
46    ExtMachInst emi;
47    bool instDone;
48    MiscReg asi;
49
50  public:
51    Decoder() : instDone(false), asi(0)
52    {}
53
54    void process() {}
55
56    void
57    reset()
58    {
59        instDone = false;
60    }
61
62    // Use this to give data to the predecoder. This should be used
63    // when there is control flow.
64    void
65    moreBytes(const PCState &pc, Addr fetchPC, MachInst inst)
66    {
67        emi = inst;
68        // The I bit, bit 13, is used to figure out where the ASI
69        // should come from. Use that in the ExtMachInst. This is
70        // slightly redundant, but it removes the need to put a condition
71        // into all the execute functions
72        if (inst & (1 << 13)) {
73            emi |= (static_cast<ExtMachInst>(
74                        asi << (sizeof(MachInst) * 8)));
75        } else {
76            emi |= (static_cast<ExtMachInst>(bits(inst, 12, 5))
77                    << (sizeof(MachInst) * 8));
78        }
79        instDone = true;
80    }
81
82    bool
83    needMoreBytes()
84    {
85        return true;
86    }
87
88    bool
89    instReady()
90    {
91        return instDone;
92    }
93
94    void
95    setContext(MiscReg _asi)
96    {
97        asi = _asi;
98    }
99
100    void takeOverFrom(Decoder *old) {}
101
102  protected:
103    /// A cache of decoded instruction objects.
104    static GenericISA::BasicDecodeCache defaultCache;
105
106  public:
107    StaticInstPtr decodeInst(ExtMachInst mach_inst);
108
109    /// Decode a machine instruction.
110    /// @param mach_inst The binary instruction to decode.
111    /// @retval A pointer to the corresponding StaticInst object.
112    StaticInstPtr
113    decode(ExtMachInst mach_inst, Addr addr)
114    {
115        return defaultCache.decode(this, mach_inst, addr);
116    }
117
118    StaticInstPtr
119    decode(SparcISA::PCState &nextPC)
120    {
121        if (!instDone)
122            return NULL;
123        instDone = false;
124        return decode(emi, nextPC.instAddr());
125    }
126};
127
128} // namespace SparcISA
129
130#endif // __ARCH_SPARC_DECODER_HH__
131