1/*
2 * Copyright (c) 2004-2005 The Regents of The University of Michigan
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

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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
29#ifndef __CPU_O3_CPU_SIMPLE_DECODE_HH__
30#define __CPU_O3_CPU_SIMPLE_DECODE_HH__
31
32#include <queue>
33
34#include "base/statistics.hh"
35#include "base/timebuf.hh"
36
37template<class Impl>
38class SimpleDecode
39{
40 private:
41 // Typedefs from the Impl.
42 typedef typename Impl::FullCPU FullCPU;
43 typedef typename Impl::DynInstPtr DynInstPtr;
44 typedef typename Impl::Params Params;
45 typedef typename Impl::CPUPol CPUPol;
46
47 // Typedefs from the CPU policy.
48 typedef typename CPUPol::FetchStruct FetchStruct;
49 typedef typename CPUPol::DecodeStruct DecodeStruct;
50 typedef typename CPUPol::TimeStruct TimeStruct;
51
52 public:
53 // The only time decode will become blocked is if dispatch becomes
54 // blocked, which means IQ or ROB is probably full.
55 enum Status {
56 Running,
57 Idle,
58 Squashing,
59 Blocked,
60 Unblocking
61 };
62
63 private:
64 // May eventually need statuses on a per thread basis.
65 Status _status;
66
67 public:
68 SimpleDecode(Params &params);
69
70 void regStats();
71
72 void setCPU(FullCPU *cpu_ptr);
73
74 void setTimeBuffer(TimeBuffer<TimeStruct> *tb_ptr);
75
76 void setDecodeQueue(TimeBuffer<DecodeStruct> *dq_ptr);
77
78 void setFetchQueue(TimeBuffer<FetchStruct> *fq_ptr);
79
80 void tick();
81
82 void decode();
83
84 private:
85 inline bool fetchInstsValid();
86
87 void block();
88
89 inline void unblock();
90
91 void squash(DynInstPtr &inst);
92
93 public:
94 // Might want to make squash a friend function.
95 void squash();
96
97 private:
98 // Interfaces to objects outside of decode.
99 /** CPU interface. */
100 FullCPU *cpu;
101
102 /** Time buffer interface. */
103 TimeBuffer<TimeStruct> *timeBuffer;

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122 typename TimeBuffer<DecodeStruct>::wire toRename;
123
124 /** Fetch instruction queue interface. */
125 TimeBuffer<FetchStruct> *fetchQueue;
126
127 /** Wire to get fetch's output from fetch queue. */
128 typename TimeBuffer<FetchStruct>::wire fromFetch;
129
130 /** Skid buffer between fetch and decode. */
131 std::queue<FetchStruct> skidBuffer;
132
133 //Consider making these unsigned to avoid any confusion.
134 /** Rename to decode delay, in ticks. */
135 unsigned renameToDecodeDelay;
136
137 /** IEW to decode delay, in ticks. */
138 unsigned iewToDecodeDelay;
139
140 /** Commit to decode delay, in ticks. */
141 unsigned commitToDecodeDelay;
142
143 /** Fetch to decode delay, in ticks. */
144 unsigned fetchToDecodeDelay;
145
146 /** The width of decode, in instructions. */
147 unsigned decodeWidth;
148
149 /** The instruction that decode is currently on. It needs to have
150 * persistent state so that when a stall occurs in the middle of a
151 * group of instructions, it can restart at the proper instruction.
152 */
153 unsigned numInst;
154
155 Stats::Scalar<> decodeIdleCycles;
156 Stats::Scalar<> decodeBlockedCycles;
157 Stats::Scalar<> decodeUnblockCycles;
158 Stats::Scalar<> decodeSquashCycles;
159 Stats::Scalar<> decodeBranchMispred;
160 Stats::Scalar<> decodeControlMispred;
161 Stats::Scalar<> decodeDecodedInsts;
162 Stats::Scalar<> decodeSquashedInsts;
163};
164
165#endif // __CPU_O3_CPU_SIMPLE_DECODE_HH__