fu_pool.hh revision 10814 
1/*
2 * Copyright (c) 2012-2013 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 * Copyright (c) 2006 The Regents of The University of Michigan
15 * All rights reserved.
16 *
17 * Redistribution and use in source and binary forms, with or without
18 * modification, are permitted provided that the following conditions are
19 * met: redistributions of source code must retain the above copyright
20 * notice, this list of conditions and the following disclaimer;
21 * redistributions in binary form must reproduce the above copyright
22 * notice, this list of conditions and the following disclaimer in the
23 * documentation and/or other materials provided with the distribution;
24 * neither the name of the copyright holders nor the names of its
25 * contributors may be used to endorse or promote products derived from
26 * this software without specific prior written permission.
27 *
28 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
29 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
30 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
31 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
32 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
33 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
34 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
35 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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38 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
39 *
40 * Authors: Kevin Lim
41 */
42
43#ifndef __CPU_O3_FU_POOL_HH__
44#define __CPU_O3_FU_POOL_HH__
45
46#include <array>
47#include <bitset>
48#include <list>
49#include <string>
50#include <vector>
51
52#include "cpu/op_class.hh"
53#include "params/FUPool.hh"
54#include "sim/sim_object.hh"
55
56class FUDesc;
57class FuncUnit;
58
59/**
60 * Pool of FU's, specific to the new CPU model. The old FU pool had lists of
61 * free units and busy units, and whenever a FU was needed it would iterate
62 * through the free units to find a FU that provided the capability. This pool
63 * has lists of units specific to each of the capabilities, and whenever a FU
64 * is needed, it iterates through that list to find a free unit. The previous
65 * FU pool would have to be ticked each cycle to update which units became
66 * free. This FU pool lets the IEW stage handle freeing units, which frees
67 * them as their scheduled execution events complete. This limits units in this
68 * model to either have identical issue and op latencies, or 1 cycle issue
69 * latencies.
70 */
71class FUPool : public SimObject
72{
73  private:
74    /** Maximum op execution latencies, per op class. */
75    std::array<Cycles, Num_OpClasses> maxOpLatencies;
76    /** Whether op is pipelined or not. */
77    std::array<bool, Num_OpClasses> pipelined;
78
79    /** Bitvector listing capabilities of this FU pool. */
80    std::bitset<Num_OpClasses> capabilityList;
81
82    /** Bitvector listing which FUs are busy. */
83    std::vector<bool> unitBusy;
84
85    /** List of units to be freed at the end of this cycle. */
86    std::vector<int> unitsToBeFreed;
87
88    /**
89     * Class that implements a circular queue to hold FU indices. The hope is
90     * that FUs that have been just used will be moved to the end of the queue
91     * by iterating through it, thus leaving free units at the head of the
92     * queue.
93     */
94    class FUIdxQueue {
95      public:
96        /** Constructs a circular queue of FU indices. */
97        FUIdxQueue()
98            : idx(0), size(0)
99        { }
100
101        /** Adds a FU to the queue. */
102        inline void addFU(int fu_idx);
103
104        /** Returns the index of the FU at the head of the queue, and changes
105         *  the index to the next element.
106         */
107        inline int getFU();
108
109      private:
110        /** Circular queue index. */
111        int idx;
112
113        /** Size of the queue. */
114        int size;
115
116        /** Queue of FU indices. */
117        std::vector<int> funcUnitsIdx;
118    };
119
120    /** Per op class queues of FUs that provide that capability. */
121    FUIdxQueue fuPerCapList[Num_OpClasses];
122
123    /** Number of FUs. */
124    int numFU;
125
126    /** Functional units. */
127    std::vector<FuncUnit *> funcUnits;
128
129    typedef std::vector<FuncUnit *>::iterator fuListIterator;
130
131  public:
132    typedef FUPoolParams Params;
133    /** Constructs a FU pool. */
134    FUPool(const Params *p);
135    ~FUPool();
136
137    /**
138     * Gets a FU providing the requested capability. Will mark the unit as busy,
139     * but leaves the freeing of the unit up to the IEW stage.
140     * @param capability The capability requested.
141     * @return Returns -2 if the FU pool does not have the capability, -1 if
142     * there is no free FU, and the FU's index otherwise.
143     */
144    int getUnit(OpClass capability);
145
146    /** Frees a FU at the end of this cycle. */
147    void freeUnitNextCycle(int fu_idx);
148
149    /** Frees all FUs on the list. */
150    void processFreeUnits();
151
152    /** Returns the total number of FUs. */
153    int size() { return numFU; }
154
155    /** Debugging function used to dump FU information. */
156    void dump();
157
158    /** Returns the operation execution latency of the given capability. */
159    Cycles getOpLatency(OpClass capability) {
160        return maxOpLatencies[capability];
161    }
162
163    /** Returns the issue latency of the given capability. */
164    bool isPipelined(OpClass capability) {
165        return pipelined[capability];
166    }
167
168    /** Have all the FUs drained? */
169    bool isDrained() const;
170
171    /** Takes over from another CPU's thread. */
172    void takeOverFrom() {};
173};
174
175#endif // __CPU_O3_FU_POOL_HH__
176