cpu/o3/decode.hh

   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
  11  * documentation and/or other materials provided with the distribution;
  12  * neither the name of the copyright holders nor the names of its
  13  * contributors may be used to endorse or promote products derived from
  14  * this software without specific prior written permission.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  17  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  18  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  19  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  20  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  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
  37 template<class Impl>
  38 class 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;
 104
 105     /** Wire to get rename's output from backwards time buffer. */
 106     typename TimeBuffer<TimeStruct>::wire fromRename;
 107
 108     /** Wire to get iew's information from backwards time buffer. */
 109     typename TimeBuffer<TimeStruct>::wire fromIEW;
 110
 111     /** Wire to get commit's information from backwards time buffer. */
 112     typename TimeBuffer<TimeStruct>::wire fromCommit;
 113
 114     /** Wire to write information heading to previous stages. */
 115     // Might not be the best name as not only fetch will read it.
 116     typename TimeBuffer<TimeStruct>::wire toFetch;
 117
 118     /** Decode instruction queue. */
 119     TimeBuffer<DecodeStruct> *decodeQueue;
 120
 121     /** Wire used to write any information heading to rename. */
 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__