scoreboard.hh revision 10935:acd48ddd725f 
1/*
2 * Copyright (c) 2013-2014 ARM Limited
3 * All rights reserved
4 *
5 * The license below extends only to copyright in the software and shall
6 * not be construed as granting a license to any other intellectual
7 * property including but not limited to intellectual property relating
8 * to a hardware implementation of the functionality of the software
9 * licensed hereunder.  You may use the software subject to the license
10 * terms below provided that you ensure that this notice is replicated
11 * unmodified and in its entirety in all distributions of the software,
12 * modified or unmodified, in source code or in binary form.
13 *
14 * Redistribution and use in source and binary forms, with or without
15 * modification, are permitted provided that the following conditions are
16 * met: redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer;
18 * redistributions in binary form must reproduce the above copyright
19 * notice, this list of conditions and the following disclaimer in the
20 * documentation and/or other materials provided with the distribution;
21 * neither the name of the copyright holders nor the names of its
22 * contributors may be used to endorse or promote products derived from
23 * this software without specific prior written permission.
24 *
25 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
26 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
27 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
28 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
29 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
30 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
31 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
32 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
33 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
35 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
36 *
37 * Authors: Andrew Bardsley
38 */
39
40/**
41 * @file
42 *
43 *  A simple instruction scoreboard for tracking dependencies in Execute.
44 */
45
46#ifndef __CPU_MINOR_SCOREBOARD_HH__
47#define __CPU_MINOR_SCOREBOARD_HH__
48
49#include "cpu/minor/cpu.hh"
50#include "cpu/minor/dyn_inst.hh"
51#include "cpu/minor/trace.hh"
52
53namespace Minor
54{
55
56/** A scoreboard of register dependencies including, for each register:
57 *  The number of in-flight instructions which will generate a result for
58 *  this register */
59class Scoreboard : public Named
60{
61  public:
62    /** The number of registers in the Scoreboard.  These
63     *  are just the integer, CC and float registers packed
64     *  together with integer regs in the range [0,NumIntRegs-1],
65     *  CC regs in the range [NumIntRegs, NumIntRegs+NumCCRegs-1]
66     *  and float regs in the range
67     *  [NumIntRegs+NumCCRegs, NumFloatRegs+NumIntRegs+NumCCRegs-1] */
68    const unsigned numRegs;
69
70    /** Type to use for thread context registers */
71    typedef TheISA::RegIndex RegIndex;
72
73    /** Type to use when indexing numResults */
74    typedef unsigned short int Index;
75
76    /** Count of the number of in-flight instructions that
77     *  have results for each register */
78    std::vector<Index> numResults;
79
80    /** Count of the number of results which can't be predicted */
81    std::vector<Index> numUnpredictableResults;
82
83    /** Index of the FU generating this result */
84    std::vector<int> fuIndices;
85
86    /** The estimated cycle number that the result will be presented.
87     *  This can be offset from to allow forwarding to be simulated as
88     *  long as instruction completion is *strictly* in order with
89     *  respect to instructions with unpredictable result timing */
90    std::vector<Cycles> returnCycle;
91
92    /** The execute sequence number of the most recent inst to generate this
93     *  register value */
94    std::vector<InstSeqNum> writingInst;
95
96  public:
97    Scoreboard(const std::string &name) :
98        Named(name),
99        numRegs(TheISA::NumIntRegs + TheISA::NumCCRegs +
100            TheISA::NumFloatRegs),
101        numResults(numRegs, 0),
102        numUnpredictableResults(numRegs, 0),
103        fuIndices(numRegs, 0),
104        returnCycle(numRegs, Cycles(0)),
105        writingInst(numRegs, 0)
106    { }
107
108  public:
109    /** Sets scoreboard_index to the index into numResults of the
110     *  given register index.  Returns true if the given register
111     *  is in the scoreboard and false if it isn't */
112    bool findIndex(RegIndex reg, Index &scoreboard_index);
113
114    /** Mark up an instruction's effects by incrementing
115     *  numResults counts.  If mark_unpredictable is true, the inst's
116     *  destination registers are marked as being unpredictable without
117     *  an estimated retire time */
118    void markupInstDests(MinorDynInstPtr inst, Cycles retire_time,
119        ThreadContext *thread_context, bool mark_unpredictable);
120
121    /** Clear down the dependencies for this instruction.  clear_unpredictable
122     *  must match mark_unpredictable for the same inst. */
123    void clearInstDests(MinorDynInstPtr inst, bool clear_unpredictable);
124
125    /** Returns the exec sequence number of the most recent inst on
126     *  which the given inst depends.  Useful for determining which
127     *  inst must actually be committed before a dependent inst
128     *  can call initiateAcc */
129    InstSeqNum execSeqNumToWaitFor(MinorDynInstPtr inst,
130        ThreadContext *thread_context);
131
132    /** Can this instruction be issued.  Are any of its source registers
133     *  due to be written by other marked-up instructions in flight */
134    bool canInstIssue(MinorDynInstPtr inst,
135        const std::vector<Cycles> *src_reg_relative_latencies,
136        const std::vector<bool> *cant_forward_from_fu_indices,
137        Cycles now, ThreadContext *thread_context);
138
139    /** MinorTraceIF interface */
140    void minorTrace() const;
141};
142
143}
144
145#endif /* __CPU_MINOR_SCOREBOARD_HH__ */
146