decoder.hh revision 9024 
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#include "cpu/thread_context.hh"
39
40class ThreadContext;
41
42namespace SparcISA
43{
44
45class Decoder
46{
47  protected:
48    ThreadContext * tc;
49    // The extended machine instruction being generated
50    ExtMachInst emi;
51    bool instDone;
52
53  public:
54    Decoder(ThreadContext * _tc) : tc(_tc), instDone(false)
55    {}
56
57    ThreadContext *
58    getTC()
59    {
60        return tc;
61    }
62
63    void
64    setTC(ThreadContext * _tc)
65    {
66        tc = _tc;
67    }
68
69    void process() {}
70
71    void
72    reset()
73    {
74        instDone = false;
75    }
76
77    // Use this to give data to the predecoder. This should be used
78    // when there is control flow.
79    void
80    moreBytes(const PCState &pc, Addr fetchPC, MachInst inst)
81    {
82        emi = inst;
83        // The I bit, bit 13, is used to figure out where the ASI
84        // should come from. Use that in the ExtMachInst. This is
85        // slightly redundant, but it removes the need to put a condition
86        // into all the execute functions
87        if (inst & (1 << 13)) {
88            emi |= (static_cast<ExtMachInst>(
89                        tc->readMiscRegNoEffect(MISCREG_ASI))
90                    << (sizeof(MachInst) * 8));
91        } else {
92            emi |= (static_cast<ExtMachInst>(bits(inst, 12, 5))
93                    << (sizeof(MachInst) * 8));
94        }
95        instDone = true;
96    }
97
98    bool
99    needMoreBytes()
100    {
101        return true;
102    }
103
104    bool
105    instReady()
106    {
107        return instDone;
108    }
109
110  protected:
111    /// A cache of decoded instruction objects.
112    static GenericISA::BasicDecodeCache defaultCache;
113
114  public:
115    StaticInstPtr decodeInst(ExtMachInst mach_inst);
116
117    /// Decode a machine instruction.
118    /// @param mach_inst The binary instruction to decode.
119    /// @retval A pointer to the corresponding StaticInst object.
120    StaticInstPtr
121    decode(ExtMachInst mach_inst, Addr addr)
122    {
123        return defaultCache.decode(this, mach_inst, addr);
124    }
125
126    StaticInstPtr
127    decode(SparcISA::PCState &nextPC)
128    {
129        if (!instDone)
130            return NULL;
131        instDone = false;
132        return decode(emi, nextPC.instAddr());
133    }
134};
135
136} // namespace SparcISA
137
138#endif // __ARCH_SPARC_DECODER_HH__
139