src/cpu/o3/commit.hh - public/gem5 - Git at Google

 /*
  * Copyright (c) 2010-2012, 2014, 2019 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.
  *
  * Copyright (c) 2004-2006 The Regents of The University of Michigan
  * All rights reserved.
  *
  * 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.
  */

 #ifndef __CPU_O3_COMMIT_HH__
 #define __CPU_O3_COMMIT_HH__

 #include <queue>

 #include "base/statistics.hh"
 #include "cpu/exetrace.hh"
 #include "cpu/inst_seq.hh"
 #include "cpu/o3/comm.hh"
 #include "cpu/o3/dyn_inst_ptr.hh"
 #include "cpu/o3/iew.hh"
 #include "cpu/o3/limits.hh"
 #include "cpu/o3/rename_map.hh"
 #include "cpu/o3/rob.hh"
 #include "cpu/timebuf.hh"
 #include "enums/CommitPolicy.hh"
 #include "sim/probe/probe.hh"

 namespace gem5
 {

 struct BaseO3CPUParams;

 namespace o3
 {

 class ThreadState;

 /**
  * Commit handles single threaded and SMT commit. Its width is
  * specified by the parameters; each cycle it tries to commit that
  * many instructions. The SMT policy decides which thread it tries to
  * commit instructions from. Non- speculative instructions must reach
  * the head of the ROB before they are ready to execute; once they
  * reach the head, commit will broadcast the instruction's sequence
  * number to the previous stages so that they can issue/ execute the
  * instruction. Only one non-speculative instruction is handled per
  * cycle. Commit is responsible for handling all back-end initiated
  * redirects.  It receives the redirect, and then broadcasts it to all
  * stages, indicating the sequence number they should squash until,
  * and any necessary branch misprediction information as well. It
  * priortizes redirects by instruction's age, only broadcasting a
  * redirect if it corresponds to an instruction that should currently
  * be in the ROB. This is done by tracking the sequence number of the
  * youngest instruction in the ROB, which gets updated to any
  * squashing instruction's sequence number, and only broadcasting a
  * redirect if it corresponds to an older instruction. Commit also
  * supports multiple cycle squashing, to model a ROB that can only
  * remove a certain number of instructions per cycle.
  */
 class Commit
 {
   public:
     /** Overall commit status. Used to determine if the CPU can deschedule
      * itself due to a lack of activity.
      */
     enum CommitStatus
     {
         Active,
         Inactive
     };

     /** Individual thread status. */
     enum ThreadStatus
     {
         Running,
         Idle,
         ROBSquashing,
         TrapPending,
         FetchTrapPending,
         SquashAfterPending, //< Committing instructions before a squash.
     };

   private:
     /** Overall commit status. */
     CommitStatus _status;
     /** Next commit status, to be set at the end of the cycle. */
     CommitStatus _nextStatus;
     /** Per-thread status. */
     ThreadStatus commitStatus[MaxThreads];
     /** Commit policy used in SMT mode. */
     CommitPolicy commitPolicy;

     /** Probe Points. */
     ProbePointArg<DynInstPtr> *ppCommit;
     ProbePointArg<DynInstPtr> *ppCommitStall;
     /** To probe when an instruction is squashed */
     ProbePointArg<DynInstPtr> *ppSquash;

     /** Mark the thread as processing a trap. */
     void processTrapEvent(ThreadID tid);

   public:
     /** Construct a Commit with the given parameters. */
     Commit(CPU *_cpu, const BaseO3CPUParams &params);

     /** Returns the name of the Commit. */
     std::string name() const;

     /** Registers probes. */
     void regProbePoints();

     /** Sets the list of threads. */
     void setThreads(std::vector<ThreadState *> &threads);

     /** Sets the main time buffer pointer, used for backwards communication. */
     void setTimeBuffer(TimeBuffer<TimeStruct> *tb_ptr);

     void setFetchQueue(TimeBuffer<FetchStruct> *fq_ptr);

     /** Sets the pointer to the queue coming from rename. */
     void setRenameQueue(TimeBuffer<RenameStruct> *rq_ptr);

     /** Sets the pointer to the queue coming from IEW. */
     void setIEWQueue(TimeBuffer<IEWStruct> *iq_ptr);

     /** Sets the pointer to the IEW stage. */
     void setIEWStage(IEW *iew_stage);

     /** The pointer to the IEW stage. Used solely to ensure that
      * various events (traps, interrupts, syscalls) do not occur until
      * all stores have written back.
      */
     IEW *iewStage;

     /** Sets pointer to list of active threads. */
     void setActiveThreads(std::list<ThreadID> *at_ptr);

     /** Sets pointer to the commited state rename map. */
     void setRenameMap(UnifiedRenameMap rm_ptr[MaxThreads]);

     /** Sets pointer to the ROB. */
     void setROB(ROB *rob_ptr);

     /** Initializes stage by sending back the number of free entries. */
     void startupStage();

     /** Clear all thread-specific states */
     void clearStates(ThreadID tid);

     /** Initializes the draining of commit. */
     void drain();

     /** Resumes execution after draining. */
     void drainResume();

     /** Perform sanity checks after a drain. */
     void drainSanityCheck() const;

     /** Has the stage drained? */
     bool isDrained() const;

     /** Takes over from another CPU's thread. */
     void takeOverFrom();

     /** Deschedules a thread from scheduling */
     void deactivateThread(ThreadID tid);

     /** Is the CPU currently processing a HTM transaction? */
     bool executingHtmTransaction(ThreadID) const;

     /* Reset HTM tracking, e.g. after an abort */
     void resetHtmStartsStops(ThreadID);

     /** Ticks the commit stage, which tries to commit instructions. */
     void tick();

     /** Handles any squashes that are sent from IEW, and adds instructions
      * to the ROB and tries to commit instructions.
      */
     void commit();

     /** Returns the number of free ROB entries for a specific thread. */
     size_t numROBFreeEntries(ThreadID tid);

     /** Generates an event to schedule a squash due to a trap. */
     void generateTrapEvent(ThreadID tid, Fault inst_fault);

     /** Records that commit needs to initiate a squash due to an
      * external state update through the TC.
      */
     void generateTCEvent(ThreadID tid);

   private:
     /** Updates the overall status of commit with the nextStatus, and
      * tell the CPU if commit is active/inactive.
      */
     void updateStatus();

     /** Returns if any of the threads have the number of ROB entries changed
      * on this cycle. Used to determine if the number of free ROB entries needs
      * to be sent back to previous stages.
      */
     bool changedROBEntries();

     /** Squashes all in flight instructions. */
     void squashAll(ThreadID tid);

     /** Handles squashing due to a trap. */
     void squashFromTrap(ThreadID tid);

     /** Handles squashing due to an TC write. */
     void squashFromTC(ThreadID tid);

     /** Handles a squash from a squashAfter() request. */
     void squashFromSquashAfter(ThreadID tid);

     /**
      * Handle squashing from instruction with SquashAfter set.
      *
      * This differs from the other squashes as it squashes following
      * instructions instead of the current instruction and doesn't
      * clean up various status bits about traps/tc writes
      * pending. Since there might have been instructions committed by
      * the commit stage before the squashing instruction was reached
      * and we can't commit and squash in the same cycle, we have to
      * squash in two steps:
      *
      * <ol>
      *   <li>Immediately set the commit status of the thread of
      *       SquashAfterPending. This forces the thread to stop
      *       committing instructions in this cycle. The last
      *       instruction to be committed in this cycle will be the
      *       SquashAfter instruction.
      *   <li>In the next cycle, commit() checks for the
      *       SquashAfterPending state and squashes <i>all</i>
      *       in-flight instructions. Since the SquashAfter instruction
      *       was the last instruction to be committed in the previous
      *       cycle, this causes all subsequent instructions to be
      *       squashed.
      * </ol>
      *
      * @param tid ID of the thread to squash.
      * @param head_inst Instruction that requested the squash.
      */
     void squashAfter(ThreadID tid, const DynInstPtr &head_inst);

     /** Handles processing an interrupt. */
     void handleInterrupt();

     /** Get fetch redirecting so we can handle an interrupt */
     void propagateInterrupt();

     /** Commits as many instructions as possible. */
     void commitInsts();

     /** Tries to commit the head ROB instruction passed in.
      * @param head_inst The instruction to be committed.
      */
     bool commitHead(const DynInstPtr &head_inst, unsigned inst_num);

     /** Gets instructions from rename and inserts them into the ROB. */
     void getInsts();

     /** Marks completed instructions using information sent from IEW. */
     void markCompletedInsts();

     /** Gets the thread to commit, based on the SMT policy. */
     ThreadID getCommittingThread();

     /** Returns the thread ID to use based on a round robin policy. */
     ThreadID roundRobin();

     /** Returns the thread ID to use based on an oldest instruction policy. */
     ThreadID oldestReady();

   public:
     /** Reads the PC of a specific thread. */
     const PCStateBase &pcState(ThreadID tid) { return *pc[tid]; }

     /** Sets the PC of a specific thread. */
     void pcState(const PCStateBase &val, ThreadID tid) { set(pc[tid], val); }

   private:
     /** Time buffer interface. */
     TimeBuffer<TimeStruct> *timeBuffer;

     /** Wire to write information heading to previous stages. */
     TimeBuffer<TimeStruct>::wire toIEW;

     /** Wire to read information from IEW (for ROB). */
     TimeBuffer<TimeStruct>::wire robInfoFromIEW;

     TimeBuffer<FetchStruct> *fetchQueue;

     TimeBuffer<FetchStruct>::wire fromFetch;

     /** IEW instruction queue interface. */
     TimeBuffer<IEWStruct> *iewQueue;

     /** Wire to read information from IEW queue. */
     TimeBuffer<IEWStruct>::wire fromIEW;

     /** Rename instruction queue interface, for ROB. */
     TimeBuffer<RenameStruct> *renameQueue;

     /** Wire to read information from rename queue. */
     TimeBuffer<RenameStruct>::wire fromRename;

   public:
     /** ROB interface. */
     ROB *rob;

   private:
     /** Pointer to O3CPU. */
     CPU *cpu;

     /** Vector of all of the threads. */
     std::vector<ThreadState *> thread;

     /** Records that commit has written to the time buffer this cycle. Used for
      * the CPU to determine if it can deschedule itself if there is no activity.
      */
     bool wroteToTimeBuffer;

     /** Records if the number of ROB entries has changed this cycle. If it has,
      * then the number of free entries must be re-broadcast.
      */
     bool changedROBNumEntries[MaxThreads];

     /** Records if a thread has to squash this cycle due to a trap. */
     bool trapSquash[MaxThreads];

     /** Records if a thread has to squash this cycle due to an XC write. */
     bool tcSquash[MaxThreads];

     /**
      * Instruction passed to squashAfter().
      *
      * The squash after implementation needs to buffer the instruction
      * that caused a squash since this needs to be passed to the fetch
      * stage once squashing starts.
      */
     DynInstPtr squashAfterInst[MaxThreads];

     /** Priority List used for Commit Policy */
     std::list<ThreadID> priority_list;

     /** IEW to Commit delay. */
     const Cycles iewToCommitDelay;

     /** Commit to IEW delay. */
     const Cycles commitToIEWDelay;

     /** Rename to ROB delay. */
     const Cycles renameToROBDelay;

     const Cycles fetchToCommitDelay;

     /** Rename width, in instructions.  Used so ROB knows how many
      *  instructions to get from the rename instruction queue.
      */
     const unsigned renameWidth;

     /** Commit width, in instructions. */
     const unsigned commitWidth;

     /** Number of Active Threads */
     const ThreadID numThreads;

     /** Is a drain pending? Commit is looking for an instruction boundary while
      * there are no pending interrupts
      */
     bool drainPending;

     /** Is a drain imminent? Commit has found an instruction boundary while no
      * interrupts were present or in flight.  This was the last architecturally
      * committed instruction.  Interrupts disabled and pipeline flushed.
      * Waiting for structures to finish draining.
      */
     bool drainImminent;

     /** The latency to handle a trap.  Used when scheduling trap
      * squash event.
      */
     const Cycles trapLatency;

     /** The interrupt fault. */
     Fault interrupt;

     /** The commit PC state of each thread.  Refers to the instruction that
      * is currently being processed/committed.
      */
     std::unique_ptr<PCStateBase> pc[MaxThreads];

     /** The sequence number of the youngest valid instruction in the ROB. */
     InstSeqNum youngestSeqNum[MaxThreads];

     /** The sequence number of the last commited instruction. */
     InstSeqNum lastCommitedSeqNum[MaxThreads];

     /** Records if there is a trap currently in flight. */
     bool trapInFlight[MaxThreads];

     /** Records if there were any stores committed this cycle. */
     bool committedStores[MaxThreads];

     /** Records if commit should check if the ROB is truly empty (see
         commit_impl.hh). */
     bool checkEmptyROB[MaxThreads];

     /** Pointer to the list of active threads. */
     std::list<ThreadID> *activeThreads;

     /** Rename map interface. */
     UnifiedRenameMap *renameMap[MaxThreads];

     /** True if last committed microop can be followed by an interrupt */
     bool canHandleInterrupts;

     /** Have we had an interrupt pending and then seen it de-asserted because
         of a masking change? In this case the variable is set and the next time
         interrupts are enabled and pending the pipeline will squash to avoid
         a possible livelock senario.  */
     bool avoidQuiesceLiveLock;

     /** Updates commit stats based on this instruction. */
     void updateComInstStats(const DynInstPtr &inst);

     // HTM
     int htmStarts[MaxThreads];
     int htmStops[MaxThreads];

     struct CommitStats : public statistics::Group
     {
         CommitStats(CPU *cpu, Commit *commit);
         /** Stat for the total number of squashed instructions discarded by
          * commit.
          */
         statistics::Scalar commitSquashedInsts;
         /** Stat for the total number of times commit has had to stall due
          * to a non-speculative instruction reaching the head of the ROB.
          */
         statistics::Scalar commitNonSpecStalls;
         /** Stat for the total number of branch mispredicts that caused a
          * squash.
          */
         statistics::Scalar branchMispredicts;
         /** Distribution of the number of committed instructions each cycle. */
         statistics::Distribution numCommittedDist;

         /** Total number of instructions committed. */
         statistics::Vector instsCommitted;
         /** Total number of ops (including micro ops) committed. */
         statistics::Vector opsCommitted;
         /** Stat for the total number of committed memory references. */
         statistics::Vector memRefs;
         /** Stat for the total number of committed loads. */
         statistics::Vector loads;
         /** Stat for the total number of committed atomics. */
         statistics::Vector amos;
         /** Total number of committed memory barriers. */
         statistics::Vector membars;
         /** Total number of committed branches. */
         statistics::Vector branches;
         /** Total number of vector instructions */
         statistics::Vector vectorInstructions;
         /** Total number of floating point instructions */
         statistics::Vector floating;
         /** Total number of integer instructions */
         statistics::Vector integer;
         /** Total number of function calls */
         statistics::Vector functionCalls;
         /** Committed instructions by instruction type (OpClass) */
         statistics::Vector2d committedInstType;

         /** Number of cycles where the commit bandwidth limit is reached. */
         statistics::Scalar commitEligibleSamples;
     } stats;
 };

 } // namespace o3
 } // namespace gem5

 #endif // __CPU_O3_COMMIT_HH__
	/*
	* Copyright (c) 2010-2012, 2014, 2019 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.
	*
	* Copyright (c) 2004-2006 The Regents of The University of Michigan
	* All rights reserved.
	*
	* 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.
	*/

	#ifndef __CPU_O3_COMMIT_HH__
	#define __CPU_O3_COMMIT_HH__

	#include <queue>

	#include "base/statistics.hh"
	#include "cpu/exetrace.hh"
	#include "cpu/inst_seq.hh"
	#include "cpu/o3/comm.hh"
	#include "cpu/o3/dyn_inst_ptr.hh"
	#include "cpu/o3/iew.hh"
	#include "cpu/o3/limits.hh"
	#include "cpu/o3/rename_map.hh"
	#include "cpu/o3/rob.hh"
	#include "cpu/timebuf.hh"
	#include "enums/CommitPolicy.hh"
	#include "sim/probe/probe.hh"

	namespace gem5
	{

	struct BaseO3CPUParams;

	namespace o3
	{

	class ThreadState;

	/**
	* Commit handles single threaded and SMT commit. Its width is
	* specified by the parameters; each cycle it tries to commit that
	* many instructions. The SMT policy decides which thread it tries to
	* commit instructions from. Non- speculative instructions must reach
	* the head of the ROB before they are ready to execute; once they
	* reach the head, commit will broadcast the instruction's sequence
	* number to the previous stages so that they can issue/ execute the
	* instruction. Only one non-speculative instruction is handled per
	* cycle. Commit is responsible for handling all back-end initiated
	* redirects. It receives the redirect, and then broadcasts it to all
	* stages, indicating the sequence number they should squash until,
	* and any necessary branch misprediction information as well. It
	* priortizes redirects by instruction's age, only broadcasting a
	* redirect if it corresponds to an instruction that should currently
	* be in the ROB. This is done by tracking the sequence number of the
	* youngest instruction in the ROB, which gets updated to any
	* squashing instruction's sequence number, and only broadcasting a
	* redirect if it corresponds to an older instruction. Commit also
	* supports multiple cycle squashing, to model a ROB that can only
	* remove a certain number of instructions per cycle.
	*/
	class Commit
	{
	public:
	/** Overall commit status. Used to determine if the CPU can deschedule
	* itself due to a lack of activity.
	*/
	enum CommitStatus
	{
	Active,
	Inactive
	};

	/** Individual thread status. */
	enum ThreadStatus
	{
	Running,
	Idle,
	ROBSquashing,
	TrapPending,
	FetchTrapPending,
	SquashAfterPending, //< Committing instructions before a squash.
	};

	private:
	/** Overall commit status. */
	CommitStatus _status;
	/** Next commit status, to be set at the end of the cycle. */
	CommitStatus _nextStatus;
	/** Per-thread status. */
	ThreadStatus commitStatus[MaxThreads];
	/** Commit policy used in SMT mode. */
	CommitPolicy commitPolicy;

	/** Probe Points. */
	ProbePointArg<DynInstPtr> *ppCommit;
	ProbePointArg<DynInstPtr> *ppCommitStall;
	/** To probe when an instruction is squashed */
	ProbePointArg<DynInstPtr> *ppSquash;

	/** Mark the thread as processing a trap. */
	void processTrapEvent(ThreadID tid);

	public:
	/** Construct a Commit with the given parameters. */
	Commit(CPU *_cpu, const BaseO3CPUParams &params);

	/** Returns the name of the Commit. */
	std::string name() const;

	/** Registers probes. */
	void regProbePoints();

	/** Sets the list of threads. */
	void setThreads(std::vector<ThreadState *> &threads);

	/** Sets the main time buffer pointer, used for backwards communication. */
	void setTimeBuffer(TimeBuffer<TimeStruct> *tb_ptr);

	void setFetchQueue(TimeBuffer<FetchStruct> *fq_ptr);

	/** Sets the pointer to the queue coming from rename. */
	void setRenameQueue(TimeBuffer<RenameStruct> *rq_ptr);

	/** Sets the pointer to the queue coming from IEW. */
	void setIEWQueue(TimeBuffer<IEWStruct> *iq_ptr);

	/** Sets the pointer to the IEW stage. */
	void setIEWStage(IEW *iew_stage);

	/** The pointer to the IEW stage. Used solely to ensure that
	* various events (traps, interrupts, syscalls) do not occur until
	* all stores have written back.
	*/
	IEW *iewStage;

	/** Sets pointer to list of active threads. */
	void setActiveThreads(std::list<ThreadID> *at_ptr);

	/** Sets pointer to the commited state rename map. */
	void setRenameMap(UnifiedRenameMap rm_ptr[MaxThreads]);

	/** Sets pointer to the ROB. */
	void setROB(ROB *rob_ptr);

	/** Initializes stage by sending back the number of free entries. */
	void startupStage();

	/** Clear all thread-specific states */
	void clearStates(ThreadID tid);

	/** Initializes the draining of commit. */
	void drain();

	/** Resumes execution after draining. */
	void drainResume();

	/** Perform sanity checks after a drain. */
	void drainSanityCheck() const;

	/** Has the stage drained? */
	bool isDrained() const;

	/** Takes over from another CPU's thread. */
	void takeOverFrom();

	/** Deschedules a thread from scheduling */
	void deactivateThread(ThreadID tid);

	/** Is the CPU currently processing a HTM transaction? */
	bool executingHtmTransaction(ThreadID) const;

	/* Reset HTM tracking, e.g. after an abort */
	void resetHtmStartsStops(ThreadID);

	/** Ticks the commit stage, which tries to commit instructions. */
	void tick();

	/** Handles any squashes that are sent from IEW, and adds instructions
	* to the ROB and tries to commit instructions.
	*/
	void commit();

	/** Returns the number of free ROB entries for a specific thread. */
	size_t numROBFreeEntries(ThreadID tid);

	/** Generates an event to schedule a squash due to a trap. */
	void generateTrapEvent(ThreadID tid, Fault inst_fault);

	/** Records that commit needs to initiate a squash due to an
	* external state update through the TC.
	*/
	void generateTCEvent(ThreadID tid);

	private:
	/** Updates the overall status of commit with the nextStatus, and
	* tell the CPU if commit is active/inactive.
	*/
	void updateStatus();

	/** Returns if any of the threads have the number of ROB entries changed
	* on this cycle. Used to determine if the number of free ROB entries needs
	* to be sent back to previous stages.
	*/
	bool changedROBEntries();

	/** Squashes all in flight instructions. */
	void squashAll(ThreadID tid);

	/** Handles squashing due to a trap. */
	void squashFromTrap(ThreadID tid);

	/** Handles squashing due to an TC write. */
	void squashFromTC(ThreadID tid);

	/** Handles a squash from a squashAfter() request. */
	void squashFromSquashAfter(ThreadID tid);

	/**
	* Handle squashing from instruction with SquashAfter set.
	*
	* This differs from the other squashes as it squashes following
	* instructions instead of the current instruction and doesn't
	* clean up various status bits about traps/tc writes
	* pending. Since there might have been instructions committed by
	* the commit stage before the squashing instruction was reached
	* and we can't commit and squash in the same cycle, we have to
	* squash in two steps:
	*
	* <ol>
	* <li>Immediately set the commit status of the thread of
	* SquashAfterPending. This forces the thread to stop
	* committing instructions in this cycle. The last
	* instruction to be committed in this cycle will be the
	* SquashAfter instruction.
	* <li>In the next cycle, commit() checks for the
	* SquashAfterPending state and squashes <i>all</i>
	* in-flight instructions. Since the SquashAfter instruction
	* was the last instruction to be committed in the previous
	* cycle, this causes all subsequent instructions to be
	* squashed.
	* </ol>
	*
	* @param tid ID of the thread to squash.
	* @param head_inst Instruction that requested the squash.
	*/
	void squashAfter(ThreadID tid, const DynInstPtr &head_inst);

	/** Handles processing an interrupt. */
	void handleInterrupt();

	/** Get fetch redirecting so we can handle an interrupt */
	void propagateInterrupt();

	/** Commits as many instructions as possible. */
	void commitInsts();

	/** Tries to commit the head ROB instruction passed in.
	* @param head_inst The instruction to be committed.
	*/
	bool commitHead(const DynInstPtr &head_inst, unsigned inst_num);

	/** Gets instructions from rename and inserts them into the ROB. */
	void getInsts();

	/** Marks completed instructions using information sent from IEW. */
	void markCompletedInsts();

	/** Gets the thread to commit, based on the SMT policy. */
	ThreadID getCommittingThread();

	/** Returns the thread ID to use based on a round robin policy. */
	ThreadID roundRobin();

	/** Returns the thread ID to use based on an oldest instruction policy. */
	ThreadID oldestReady();

	public:
	/** Reads the PC of a specific thread. */
	const PCStateBase &pcState(ThreadID tid) { return *pc[tid]; }

	/** Sets the PC of a specific thread. */
	void pcState(const PCStateBase &val, ThreadID tid) { set(pc[tid], val); }

	private:
	/** Time buffer interface. */
	TimeBuffer<TimeStruct> *timeBuffer;

	/** Wire to write information heading to previous stages. */
	TimeBuffer<TimeStruct>::wire toIEW;

	/** Wire to read information from IEW (for ROB). */
	TimeBuffer<TimeStruct>::wire robInfoFromIEW;

	TimeBuffer<FetchStruct> *fetchQueue;

	TimeBuffer<FetchStruct>::wire fromFetch;

	/** IEW instruction queue interface. */
	TimeBuffer<IEWStruct> *iewQueue;

	/** Wire to read information from IEW queue. */
	TimeBuffer<IEWStruct>::wire fromIEW;

	/** Rename instruction queue interface, for ROB. */
	TimeBuffer<RenameStruct> *renameQueue;

	/** Wire to read information from rename queue. */
	TimeBuffer<RenameStruct>::wire fromRename;

	public:
	/** ROB interface. */
	ROB *rob;

	private:
	/** Pointer to O3CPU. */
	CPU *cpu;

	/** Vector of all of the threads. */
	std::vector<ThreadState *> thread;

	/** Records that commit has written to the time buffer this cycle. Used for
	* the CPU to determine if it can deschedule itself if there is no activity.
	*/
	bool wroteToTimeBuffer;

	/** Records if the number of ROB entries has changed this cycle. If it has,
	* then the number of free entries must be re-broadcast.
	*/
	bool changedROBNumEntries[MaxThreads];

	/** Records if a thread has to squash this cycle due to a trap. */
	bool trapSquash[MaxThreads];

	/** Records if a thread has to squash this cycle due to an XC write. */
	bool tcSquash[MaxThreads];

	/**
	* Instruction passed to squashAfter().
	*
	* The squash after implementation needs to buffer the instruction
	* that caused a squash since this needs to be passed to the fetch
	* stage once squashing starts.
	*/
	DynInstPtr squashAfterInst[MaxThreads];

	/** Priority List used for Commit Policy */
	std::list<ThreadID> priority_list;

	/** IEW to Commit delay. */
	const Cycles iewToCommitDelay;

	/** Commit to IEW delay. */
	const Cycles commitToIEWDelay;

	/** Rename to ROB delay. */
	const Cycles renameToROBDelay;

	const Cycles fetchToCommitDelay;

	/** Rename width, in instructions. Used so ROB knows how many
	* instructions to get from the rename instruction queue.
	*/
	const unsigned renameWidth;

	/** Commit width, in instructions. */
	const unsigned commitWidth;

	/** Number of Active Threads */
	const ThreadID numThreads;

	/** Is a drain pending? Commit is looking for an instruction boundary while
	* there are no pending interrupts
	*/
	bool drainPending;

	/** Is a drain imminent? Commit has found an instruction boundary while no
	* interrupts were present or in flight. This was the last architecturally
	* committed instruction. Interrupts disabled and pipeline flushed.
	* Waiting for structures to finish draining.
	*/
	bool drainImminent;

	/** The latency to handle a trap. Used when scheduling trap
	* squash event.
	*/
	const Cycles trapLatency;

	/** The interrupt fault. */
	Fault interrupt;

	/** The commit PC state of each thread. Refers to the instruction that
	* is currently being processed/committed.
	*/
	std::unique_ptr<PCStateBase> pc[MaxThreads];

	/** The sequence number of the youngest valid instruction in the ROB. */
	InstSeqNum youngestSeqNum[MaxThreads];

	/** The sequence number of the last commited instruction. */
	InstSeqNum lastCommitedSeqNum[MaxThreads];

	/** Records if there is a trap currently in flight. */
	bool trapInFlight[MaxThreads];

	/** Records if there were any stores committed this cycle. */
	bool committedStores[MaxThreads];

	/** Records if commit should check if the ROB is truly empty (see
	commit_impl.hh). */
	bool checkEmptyROB[MaxThreads];

	/** Pointer to the list of active threads. */
	std::list<ThreadID> *activeThreads;

	/** Rename map interface. */
	UnifiedRenameMap *renameMap[MaxThreads];

	/** True if last committed microop can be followed by an interrupt */
	bool canHandleInterrupts;

	/** Have we had an interrupt pending and then seen it de-asserted because
	of a masking change? In this case the variable is set and the next time
	interrupts are enabled and pending the pipeline will squash to avoid
	a possible livelock senario. */
	bool avoidQuiesceLiveLock;

	/** Updates commit stats based on this instruction. */
	void updateComInstStats(const DynInstPtr &inst);

	// HTM
	int htmStarts[MaxThreads];
	int htmStops[MaxThreads];

	struct CommitStats : public statistics::Group
	{
	CommitStats(CPU cpu, Commit commit);
	/** Stat for the total number of squashed instructions discarded by
	* commit.
	*/
	statistics::Scalar commitSquashedInsts;
	/** Stat for the total number of times commit has had to stall due
	* to a non-speculative instruction reaching the head of the ROB.
	*/
	statistics::Scalar commitNonSpecStalls;
	/** Stat for the total number of branch mispredicts that caused a
	* squash.
	*/
	statistics::Scalar branchMispredicts;
	/** Distribution of the number of committed instructions each cycle. */
	statistics::Distribution numCommittedDist;

	/** Total number of instructions committed. */
	statistics::Vector instsCommitted;
	/** Total number of ops (including micro ops) committed. */
	statistics::Vector opsCommitted;
	/** Stat for the total number of committed memory references. */
	statistics::Vector memRefs;
	/** Stat for the total number of committed loads. */
	statistics::Vector loads;
	/** Stat for the total number of committed atomics. */
	statistics::Vector amos;
	/** Total number of committed memory barriers. */
	statistics::Vector membars;
	/** Total number of committed branches. */
	statistics::Vector branches;
	/** Total number of vector instructions */
	statistics::Vector vectorInstructions;
	/** Total number of floating point instructions */
	statistics::Vector floating;
	/** Total number of integer instructions */
	statistics::Vector integer;
	/** Total number of function calls */
	statistics::Vector functionCalls;
	/** Committed instructions by instruction type (OpClass) */
	statistics::Vector2d committedInstType;

	/** Number of cycles where the commit bandwidth limit is reached. */
	statistics::Scalar commitEligibleSamples;
	} stats;
	};

	} // namespace o3
	} // namespace gem5

	#endif // __CPU_O3_COMMIT_HH__