src/cpu/o3/fu_pool.hh

   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,
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  38  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  39  */
  40
  41 #ifndef __CPU_O3_FU_POOL_HH__
  42 #define __CPU_O3_FU_POOL_HH__
  43
  44 #include <array>
  45 #include <bitset>
  46 #include <list>
  47 #include <string>
  48 #include <vector>
  49
  50 #include "cpu/op_class.hh"
  51 #include "params/FUPool.hh"
  52 #include "sim/sim_object.hh"
  53
  54 class FUDesc;
  55 class FuncUnit;
  56
  57 /**
  58  * Pool of FU's, specific to the new CPU model. The old FU pool had lists of
  59  * free units and busy units, and whenever a FU was needed it would iterate
  60  * through the free units to find a FU that provided the capability. This pool
  61  * has lists of units specific to each of the capabilities, and whenever a FU
  62  * is needed, it iterates through that list to find a free unit. The previous
  63  * FU pool would have to be ticked each cycle to update which units became
  64  * free. This FU pool lets the IEW stage handle freeing units, which frees
  65  * them as their scheduled execution events complete. This limits units in this
  66  * model to either have identical issue and op latencies, or 1 cycle issue
  67  * latencies.
  68  */
  69 class FUPool : public SimObject
  70 {
  71   private:
  72     /** Maximum op execution latencies, per op class. */
  73     std::array<Cycles, Num_OpClasses> maxOpLatencies;
  74     /** Whether op is pipelined or not. */
  75     std::array<bool, Num_OpClasses> pipelined;
  76
  77     /** Bitvector listing capabilities of this FU pool. */
  78     std::bitset<Num_OpClasses> capabilityList;
  79
  80     /** Bitvector listing which FUs are busy. */
  81     std::vector<bool> unitBusy;
  82
  83     /** List of units to be freed at the end of this cycle. */
  84     std::vector<int> unitsToBeFreed;
  85
  86     /**
  87      * Class that implements a circular queue to hold FU indices. The hope is
  88      * that FUs that have been just used will be moved to the end of the queue
  89      * by iterating through it, thus leaving free units at the head of the
  90      * queue.
  91      */
  92     class FUIdxQueue {
  93       public:
  94         /** Constructs a circular queue of FU indices. */
  95         FUIdxQueue()
  96             : idx(0), size(0)
  97         { }
  98
  99         /** Adds a FU to the queue. */
 100         inline void addFU(int fu_idx);
 101
 102         /** Returns the index of the FU at the head of the queue, and changes
 103          *  the index to the next element.
 104          */
 105         inline int getFU();
 106
 107       private:
 108         /** Circular queue index. */
 109         int idx;
 110
 111         /** Size of the queue. */
 112         int size;
 113
 114         /** Queue of FU indices. */
 115         std::vector<int> funcUnitsIdx;
 116     };
 117
 118     /** Per op class queues of FUs that provide that capability. */
 119     FUIdxQueue fuPerCapList[Num_OpClasses];
 120
 121     /** Number of FUs. */
 122     int numFU;
 123
 124     /** Functional units. */
 125     std::vector<FuncUnit *> funcUnits;
 126
 127     typedef std::vector<FuncUnit *>::iterator fuListIterator;
 128
 129   public:
 130     typedef FUPoolParams Params;
 131     /** Constructs a FU pool. */
 132     FUPool(const Params *p);
 133     ~FUPool();
 134
 135     static constexpr auto NoCapableFU = -2;
 136     static constexpr auto NoFreeFU = -1;
 137     /**
 138      * Gets a FU providing the requested capability. Will mark the
 139      * unit as busy, but leaves the freeing of the unit up to the IEW
 140      * stage.
 141      *
 142      * @param capability The capability requested.
 143      * @return Returns NoCapableFU if the FU pool does not have the
 144      * capability, NoFreeFU if there is no free FU, and the FU's index
 145      * otherwise.
 146      */
 147     int getUnit(OpClass capability);
 148
 149     /** Frees a FU at the end of this cycle. */
 150     void freeUnitNextCycle(int fu_idx);
 151
 152     /** Frees all FUs on the list. */
 153     void processFreeUnits();
 154
 155     /** Returns the total number of FUs. */
 156     int size() { return numFU; }
 157
 158     /** Debugging function used to dump FU information. */
 159     void dump();
 160
 161     /** Returns the operation execution latency of the given capability. */
 162     Cycles getOpLatency(OpClass capability) {
 163         return maxOpLatencies[capability];
 164     }
 165
 166     /** Returns the issue latency of the given capability. */
 167     bool isPipelined(OpClass capability) {
 168         return pipelined[capability];
 169     }
 170
 171     /** Have all the FUs drained? */
 172     bool isDrained() const;
 173
 174     /** Takes over from another CPU's thread. */
 175     void takeOverFrom() {};
 176 };
 177
 178 #endif // __CPU_O3_FU_POOL_HH__