decoder.cc revision 12120 
1/*
2 * Copyright (c) 2012 Google
3 * Copyright (c) The University of Virginia
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions are
8 * met: redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer;
10 * redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution;
13 * neither the name of the copyright holders nor the names of its
14 * contributors may be used to endorse or promote products derived from
15 * this software without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
18 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
19 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
20 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
21 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
22 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
23 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
24 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
25 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
26 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
27 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28 *
29 * Authors: Gabe Black
30 *          Alec Roelke
31 */
32
33#include "arch/riscv/decoder.hh"
34#include "arch/riscv/types.hh"
35#include "debug/Decode.hh"
36
37namespace RiscvISA
38{
39
40void
41Decoder::moreBytes(const PCState &pc, Addr fetchPC, MachInst inst)
42{
43    DPRINTF(Decode, "Getting bytes 0x%08x from address %#x\n",
44            inst, pc.pc());
45
46    bool aligned = pc.pc() % sizeof(MachInst) == 0;
47    if (mid) {
48        assert(!aligned);
49        emi |= (inst & 0xFFFF) << 16;
50        instDone = true;
51    } else {
52        MachInst instChunk = aligned ? inst & 0xFFFF :
53                                      (inst & 0xFFFF0000) >> 16;
54        if (aligned) {
55            emi = (inst & 0x3) < 0x3 ? instChunk : inst;
56            instDone = true;
57        } else {
58            emi = instChunk;
59            instDone = (instChunk & 0x3) < 0x3;
60        }
61    }
62    mid = !instDone;
63}
64
65StaticInstPtr
66Decoder::decode(ExtMachInst mach_inst, Addr addr)
67{
68    DPRINTF(Decode, "Decoding instruction 0x%08x at address %#x\n",
69            mach_inst, addr);
70    if (instMap.find(mach_inst) != instMap.end())
71        return instMap[mach_inst];
72    else {
73        StaticInstPtr si = decodeInst(mach_inst);
74        instMap[mach_inst] = si;
75        return si;
76    }
77}
78
79StaticInstPtr
80Decoder::decode(RiscvISA::PCState &nextPC)
81{
82    if (!instDone)
83        return nullptr;
84    instDone = false;
85
86    if ((emi & 0x3) < 0x3) {
87        nextPC.compressed(true);
88        nextPC.npc(nextPC.pc() + sizeof(MachInst)/2);
89    } else {
90        nextPC.compressed(false);
91        nextPC.npc(nextPC.pc() + sizeof(MachInst));
92    }
93
94    return decode(emi, nextPC.instAddr());
95}
96
97}
98