src/cpu/minor/fetch2.hh - public/gem5 - Git at Google

 /*
  * Copyright (c) 2013-2014 ARM Limited
  * All rights reserved
  *
  * The license below extends only to copyright in the software and shall
  * not be construed as granting a license to any other intellectual
  * property including but not limited to intellectual property relating
  * to a hardware implementation of the functionality of the software
  * licensed hereunder.  You may use the software subject to the license
  * terms below provided that you ensure that this notice is replicated
  * unmodified and in its entirety in all distributions of the software,
  * modified or unmodified, in source code or in binary form.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met: redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer;
  * redistributions in binary form must reproduce the above copyright
  * notice, this list of conditions and the following disclaimer in the
  * documentation and/or other materials provided with the distribution;
  * neither the name of the copyright holders nor the names of its
  * contributors may be used to endorse or promote products derived from
  * this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  * Authors: Andrew Bardsley
  */

 /**
  * @file
  *
  *  Fetch2 receives lines of data from Fetch1, separates them into
  *  instructions and passes them to Decode
  */

 #ifndef __CPU_MINOR_FETCH2_HH__
 #define __CPU_MINOR_FETCH2_HH__

 #include "cpu/minor/buffers.hh"
 #include "cpu/minor/cpu.hh"
 #include "cpu/minor/pipe_data.hh"
 #include "cpu/pred/bpred_unit.hh"
 #include "params/MinorCPU.hh"

 namespace Minor
 {

 /** This stage receives lines of data from Fetch1, separates them into
  *  instructions and passes them to Decode */
 class Fetch2 : public Named
 {
   protected:
     /** Pointer back to the containing CPU */
     MinorCPU &cpu;

     /** Input port carrying lines from Fetch1 */
     Latch<ForwardLineData>::Output inp;

     /** Input port carrying branches from Execute.  This is a snoop of the
      *  data provided to F1. */
     Latch<BranchData>::Output branchInp;

     /** Output port carrying predictions back to Fetch1 */
     Latch<BranchData>::Input predictionOut;

     /** Output port carrying instructions into Decode */
     Latch<ForwardInstData>::Input out;

     /** Interface to reserve space in the next stage */
     std::vector<InputBuffer<ForwardInstData>> &nextStageReserve;

     /** Width of output of this stage/input of next in instructions */
     unsigned int outputWidth;

     /** If true, more than one input word can be processed each cycle if
      *  there is room in the output to contain its processed data */
     bool processMoreThanOneInput;

     /** Branch predictor passed from Python configuration */
     BPredUnit &branchPredictor;

   public:
     /* Public so that Pipeline can pass it to Fetch1 */
     std::vector<InputBuffer<ForwardLineData>> inputBuffer;

   protected:
     /** Data members after this line are cycle-to-cycle state */

     struct Fetch2ThreadInfo {

         /** Default constructor */
         Fetch2ThreadInfo() :
             inputIndex(0),
             pc(TheISA::PCState(0)),
             havePC(false),
             lastStreamSeqNum(InstId::firstStreamSeqNum),
             fetchSeqNum(InstId::firstFetchSeqNum),
             expectedStreamSeqNum(InstId::firstStreamSeqNum),
             predictionSeqNum(InstId::firstPredictionSeqNum),
             blocked(false)
         { }

         Fetch2ThreadInfo(const Fetch2ThreadInfo& other) :
             inputIndex(other.inputIndex),
             pc(other.pc),
             havePC(other.havePC),
             lastStreamSeqNum(other.lastStreamSeqNum),
             expectedStreamSeqNum(other.expectedStreamSeqNum),
             predictionSeqNum(other.predictionSeqNum),
             blocked(other.blocked)
         { }

         /** Index into an incompletely processed input line that instructions
          *  are to be extracted from */
         unsigned int inputIndex;


         /** Remembered program counter value.  Between contiguous lines, this
          *  is just updated with advancePC.  For lines following changes of
          *  stream, a new PC must be loaded and havePC be set.
          *  havePC is needed to accomodate instructions which span across
          *  lines meaning that Fetch2 and the decoder need to remember a PC
          *  value and a partially-offered instruction from the previous line */
         TheISA::PCState pc;

         /** PC is currently valid.  Initially false, gets set to true when a
          *  change-of-stream line is received and false again when lines are
          *  discarded for any reason */
         bool havePC;

         /** Stream sequence number of the last seen line used to identify
          *  changes of instruction stream */
         InstSeqNum lastStreamSeqNum;

         /** Fetch2 is the source of fetch sequence numbers.  These represent the
          *  sequence that instructions were extracted from fetched lines. */
         InstSeqNum fetchSeqNum;

         /** Stream sequence number remembered from last time the
          *  predictionSeqNum changed.  Lines should only be discarded when their
          *  predictionSeqNums disagree with Fetch2::predictionSeqNum *and* they
          *  are from the same stream that bore that prediction number */
         InstSeqNum expectedStreamSeqNum;

         /** Fetch2 is the source of prediction sequence numbers.  These
          *  represent predicted changes of control flow sources from branch
          *  prediction in Fetch2. */
         InstSeqNum predictionSeqNum;

         /** Blocked indication for report */
         bool blocked;
     };

     std::vector<Fetch2ThreadInfo> fetchInfo;
     ThreadID threadPriority;

     /** Stats */
     Stats::Scalar intInstructions;
     Stats::Scalar fpInstructions;
     Stats::Scalar vecInstructions;
     Stats::Scalar loadInstructions;
     Stats::Scalar storeInstructions;

   protected:
     /** Get a piece of data to work on from the inputBuffer, or 0 if there
      *  is no data. */
     const ForwardLineData *getInput(ThreadID tid);

     /** Pop an element off the input buffer, if there are any */
     void popInput(ThreadID tid);

     /** Dump the whole contents of the input buffer.  Useful after a
      *  prediction changes control flow */
     void dumpAllInput(ThreadID tid);

     /** Update local branch prediction structures from feedback from
      *  Execute. */
     void updateBranchPrediction(const BranchData &branch);

     /** Predicts branches for the given instruction.  Updates the
      *  instruction's predicted... fields and also the branch which
      *  carries the prediction to Fetch1 */
     void predictBranch(MinorDynInstPtr inst, BranchData &branch);

     /** Use the current threading policy to determine the next thread to
      *  fetch from. */
     ThreadID getScheduledThread();

   public:
     Fetch2(const std::string &name,
         MinorCPU &cpu_,
         MinorCPUParams &params,
         Latch<ForwardLineData>::Output inp_,
         Latch<BranchData>::Output branchInp_,
         Latch<BranchData>::Input predictionOut_,
         Latch<ForwardInstData>::Input out_,
         std::vector<InputBuffer<ForwardInstData>> &next_stage_input_buffer);

   public:
     /** Pass on input/buffer data to the output if you can */
     void evaluate();

     void minorTrace() const;

     void regStats();

     /** Is this stage drained?  For Fetch2, draining is initiated by
      *  Execute halting Fetch1 causing Fetch2 to naturally drain.
      *  Branch predictions are ignored by Fetch1 during halt */
     bool isDrained();
 };

 }

 #endif /* __CPU_MINOR_FETCH2_HH__ */
	/*
	* Copyright (c) 2013-2014 ARM Limited
	* All rights reserved
	*
	* The license below extends only to copyright in the software and shall
	* not be construed as granting a license to any other intellectual
	* property including but not limited to intellectual property relating
	* to a hardware implementation of the functionality of the software
	* licensed hereunder. You may use the software subject to the license
	* terms below provided that you ensure that this notice is replicated
	* unmodified and in its entirety in all distributions of the software,
	* modified or unmodified, in source code or in binary form.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions are
	* met: redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer;
	* redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution;
	* neither the name of the copyright holders nor the names of its
	* contributors may be used to endorse or promote products derived from
	* this software without specific prior written permission.
	*
	* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
	* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
	* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
	* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
	* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*
	* Authors: Andrew Bardsley
	*/

	/**
	* @file
	*
	* Fetch2 receives lines of data from Fetch1, separates them into
	* instructions and passes them to Decode
	*/

	#ifndef __CPU_MINOR_FETCH2_HH__
	#define __CPU_MINOR_FETCH2_HH__

	#include "cpu/minor/buffers.hh"
	#include "cpu/minor/cpu.hh"
	#include "cpu/minor/pipe_data.hh"
	#include "cpu/pred/bpred_unit.hh"
	#include "params/MinorCPU.hh"

	namespace Minor
	{

	/** This stage receives lines of data from Fetch1, separates them into
	* instructions and passes them to Decode */
	class Fetch2 : public Named
	{
	protected:
	/** Pointer back to the containing CPU */
	MinorCPU &cpu;

	/** Input port carrying lines from Fetch1 */
	Latch<ForwardLineData>::Output inp;

	/** Input port carrying branches from Execute. This is a snoop of the
	* data provided to F1. */
	Latch<BranchData>::Output branchInp;

	/** Output port carrying predictions back to Fetch1 */
	Latch<BranchData>::Input predictionOut;

	/** Output port carrying instructions into Decode */
	Latch<ForwardInstData>::Input out;

	/** Interface to reserve space in the next stage */
	std::vector<InputBuffer<ForwardInstData>> &nextStageReserve;

	/** Width of output of this stage/input of next in instructions */
	unsigned int outputWidth;

	/** If true, more than one input word can be processed each cycle if
	* there is room in the output to contain its processed data */
	bool processMoreThanOneInput;

	/** Branch predictor passed from Python configuration */
	BPredUnit &branchPredictor;

	public:
	/* Public so that Pipeline can pass it to Fetch1 */
	std::vector<InputBuffer<ForwardLineData>> inputBuffer;

	protected:
	/** Data members after this line are cycle-to-cycle state */

	struct Fetch2ThreadInfo {

	/** Default constructor */
	Fetch2ThreadInfo() :
	inputIndex(0),
	pc(TheISA::PCState(0)),
	havePC(false),
	lastStreamSeqNum(InstId::firstStreamSeqNum),
	fetchSeqNum(InstId::firstFetchSeqNum),
	expectedStreamSeqNum(InstId::firstStreamSeqNum),
	predictionSeqNum(InstId::firstPredictionSeqNum),
	blocked(false)
	{ }

	Fetch2ThreadInfo(const Fetch2ThreadInfo& other) :
	inputIndex(other.inputIndex),
	pc(other.pc),
	havePC(other.havePC),
	lastStreamSeqNum(other.lastStreamSeqNum),
	expectedStreamSeqNum(other.expectedStreamSeqNum),
	predictionSeqNum(other.predictionSeqNum),
	blocked(other.blocked)
	{ }

	/** Index into an incompletely processed input line that instructions
	* are to be extracted from */
	unsigned int inputIndex;


	/** Remembered program counter value. Between contiguous lines, this
	* is just updated with advancePC. For lines following changes of
	* stream, a new PC must be loaded and havePC be set.
	* havePC is needed to accomodate instructions which span across
	* lines meaning that Fetch2 and the decoder need to remember a PC
	* value and a partially-offered instruction from the previous line */
	TheISA::PCState pc;

	/** PC is currently valid. Initially false, gets set to true when a
	* change-of-stream line is received and false again when lines are
	* discarded for any reason */
	bool havePC;

	/** Stream sequence number of the last seen line used to identify
	* changes of instruction stream */
	InstSeqNum lastStreamSeqNum;

	/** Fetch2 is the source of fetch sequence numbers. These represent the
	* sequence that instructions were extracted from fetched lines. */
	InstSeqNum fetchSeqNum;

	/** Stream sequence number remembered from last time the
	* predictionSeqNum changed. Lines should only be discarded when their
	* predictionSeqNums disagree with Fetch2::predictionSeqNum and they
	* are from the same stream that bore that prediction number */
	InstSeqNum expectedStreamSeqNum;

	/** Fetch2 is the source of prediction sequence numbers. These
	* represent predicted changes of control flow sources from branch
	* prediction in Fetch2. */
	InstSeqNum predictionSeqNum;

	/** Blocked indication for report */
	bool blocked;
	};

	std::vector<Fetch2ThreadInfo> fetchInfo;
	ThreadID threadPriority;

	/** Stats */
	Stats::Scalar intInstructions;
	Stats::Scalar fpInstructions;
	Stats::Scalar vecInstructions;
	Stats::Scalar loadInstructions;
	Stats::Scalar storeInstructions;

	protected:
	/** Get a piece of data to work on from the inputBuffer, or 0 if there
	* is no data. */
	const ForwardLineData *getInput(ThreadID tid);

	/** Pop an element off the input buffer, if there are any */
	void popInput(ThreadID tid);

	/** Dump the whole contents of the input buffer. Useful after a
	* prediction changes control flow */
	void dumpAllInput(ThreadID tid);

	/** Update local branch prediction structures from feedback from
	* Execute. */
	void updateBranchPrediction(const BranchData &branch);

	/** Predicts branches for the given instruction. Updates the
	* instruction's predicted... fields and also the branch which
	* carries the prediction to Fetch1 */
	void predictBranch(MinorDynInstPtr inst, BranchData &branch);

	/** Use the current threading policy to determine the next thread to
	* fetch from. */
	ThreadID getScheduledThread();

	public:
	Fetch2(const std::string &name,
	MinorCPU &cpu_,
	MinorCPUParams &params,
	Latch<ForwardLineData>::Output inp_,
	Latch<BranchData>::Output branchInp_,
	Latch<BranchData>::Input predictionOut_,
	Latch<ForwardInstData>::Input out_,
	std::vector<InputBuffer<ForwardInstData>> &next_stage_input_buffer);

	public:
	/** Pass on input/buffer data to the output if you can */
	void evaluate();

	void minorTrace() const;

	void regStats();

	/** Is this stage drained? For Fetch2, draining is initiated by
	* Execute halting Fetch1 causing Fetch2 to naturally drain.
	* Branch predictions are ignored by Fetch1 during halt */
	bool isDrained();
	};

	}

	#endif /* __CPU_MINOR_FETCH2_HH__ */