gem5/cpu/o3/commit.hh
Kevin Lim cbfbb7bc56 Updates to bring CPU portion of m5 up-to-date with newmem.
--HG--
extra : convert_revision : 00e6eefb24e6ffd9c7c5d8165db26fbf6199fdc4
2006-08-02 12:05:34 -04:00

443 lines
14 KiB
C++

/*
* 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 "arch/faults.hh"
#include "base/statistics.hh"
#include "base/timebuf.hh"
#include "cpu/exetrace.hh"
#include "cpu/inst_seq.hh"
#include "mem/memory_interface.hh"
template <class>
class O3ThreadState;
/**
* DefaultCommit 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.
*/
template<class Impl>
class DefaultCommit
{
public:
// Typedefs from the Impl.
typedef typename Impl::FullCPU FullCPU;
typedef typename Impl::DynInstPtr DynInstPtr;
typedef typename Impl::Params Params;
typedef typename Impl::CPUPol CPUPol;
typedef typename CPUPol::RenameMap RenameMap;
typedef typename CPUPol::ROB ROB;
typedef typename CPUPol::TimeStruct TimeStruct;
typedef typename CPUPol::FetchStruct FetchStruct;
typedef typename CPUPol::IEWStruct IEWStruct;
typedef typename CPUPol::RenameStruct RenameStruct;
typedef typename CPUPol::Fetch Fetch;
typedef typename CPUPol::IEW IEW;
typedef O3ThreadState<Impl> Thread;
/** Event class used to schedule a squash due to a trap (fault or
* interrupt) to happen on a specific cycle.
*/
class TrapEvent : public Event {
private:
DefaultCommit<Impl> *commit;
unsigned tid;
public:
TrapEvent(DefaultCommit<Impl> *_commit, unsigned _tid);
void process();
const char *description();
};
/** 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
};
/** Commit policy for SMT mode. */
enum CommitPolicy {
Aggressive,
RoundRobin,
OldestReady
};
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[Impl::MaxThreads];
/** Commit policy used in SMT mode. */
CommitPolicy commitPolicy;
public:
/** Construct a DefaultCommit with the given parameters. */
DefaultCommit(Params *params);
/** Returns the name of the DefaultCommit. */
std::string name() const;
/** Registers statistics. */
void regStats();
/** Sets the CPU pointer. */
void setCPU(FullCPU *cpu_ptr);
/** Sets the list of threads. */
void setThreads(std::vector<Thread *> &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<unsigned> *at_ptr);
/** Sets pointer to the commited state rename map. */
void setRenameMap(RenameMap rm_ptr[Impl::MaxThreads]);
/** Sets pointer to the ROB. */
void setROB(ROB *rob_ptr);
/** Initializes stage by sending back the number of free entries. */
void initStage();
/** Initializes the switching out of commit. */
void switchOut();
/** Completes the switch out of commit. */
void doSwitchOut();
/** Takes over from another CPU's thread. */
void takeOverFrom();
/** 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. */
unsigned numROBFreeEntries(unsigned tid);
/** Generates an event to schedule a squash due to a trap. */
void generateTrapEvent(unsigned tid);
/** Records that commit needs to initiate a squash due to an
* external state update through the XC.
*/
void generateXCEvent(unsigned tid);
private:
/** Updates the overall status of commit with the nextStatus, and
* tell the CPU if commit is active/inactive.
*/
void updateStatus();
/** Sets the next status based on threads' statuses, which becomes the
* current status at the end of the cycle.
*/
void setNextStatus();
/** Checks if the ROB is completed with squashing. This is for the case
* where the ROB can take multiple cycles to complete squashing.
*/
bool robDoneSquashing();
/** 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(unsigned tid);
/** Handles squashing due to a trap. */
void squashFromTrap(unsigned tid);
/** Handles squashing due to an XC write. */
void squashFromXC(unsigned tid);
/** 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(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. */
int getCommittingThread();
/** Returns the thread ID to use based on a round robin policy. */
int roundRobin();
/** Returns the thread ID to use based on an oldest instruction policy. */
int oldestReady();
public:
/** Returns the PC of the head instruction of the ROB.
* @todo: Probably remove this function as it returns only thread 0.
*/
uint64_t readPC() { return PC[0]; }
/** Returns the PC of a specific thread. */
uint64_t readPC(unsigned tid) { return PC[tid]; }
/** Sets the PC of a specific thread. */
void setPC(uint64_t val, unsigned tid) { PC[tid] = val; }
/** Reads the PC of a specific thread. */
uint64_t readNextPC(unsigned tid) { return nextPC[tid]; }
/** Sets the next PC of a specific thread. */
void setNextPC(uint64_t val, unsigned tid) { nextPC[tid] = val; }
private:
/** Time buffer interface. */
TimeBuffer<TimeStruct> *timeBuffer;
/** Wire to write information heading to previous stages. */
typename TimeBuffer<TimeStruct>::wire toIEW;
/** Wire to read information from IEW (for ROB). */
typename TimeBuffer<TimeStruct>::wire robInfoFromIEW;
TimeBuffer<FetchStruct> *fetchQueue;
typename TimeBuffer<FetchStruct>::wire fromFetch;
/** IEW instruction queue interface. */
TimeBuffer<IEWStruct> *iewQueue;
/** Wire to read information from IEW queue. */
typename TimeBuffer<IEWStruct>::wire fromIEW;
/** Rename instruction queue interface, for ROB. */
TimeBuffer<RenameStruct> *renameQueue;
/** Wire to read information from rename queue. */
typename TimeBuffer<RenameStruct>::wire fromRename;
public:
/** ROB interface. */
ROB *rob;
private:
/** Pointer to FullCPU. */
FullCPU *cpu;
/** Memory interface. Used for d-cache accesses. */
MemInterface *dcacheInterface;
/** Vector of all of the threads. */
std::vector<Thread *> thread;
Fault fetchFault;
int fetchTrapWait;
/** 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[Impl::MaxThreads];
/** A counter of how many threads are currently squashing. */
int squashCounter;
/** Records if a thread has to squash this cycle due to a trap. */
bool trapSquash[Impl::MaxThreads];
/** Records if a thread has to squash this cycle due to an XC write. */
bool xcSquash[Impl::MaxThreads];
/** Priority List used for Commit Policy */
std::list<unsigned> priority_list;
/** IEW to Commit delay, in ticks. */
unsigned iewToCommitDelay;
/** Commit to IEW delay, in ticks. */
unsigned commitToIEWDelay;
/** Rename to ROB delay, in ticks. */
unsigned renameToROBDelay;
unsigned fetchToCommitDelay;
/** Rename width, in instructions. Used so ROB knows how many
* instructions to get from the rename instruction queue.
*/
unsigned renameWidth;
/** Commit width, in instructions. */
unsigned commitWidth;
/** Number of Reorder Buffers */
unsigned numRobs;
/** Number of Active Threads */
unsigned numThreads;
/** Is a switch out pending. */
bool switchPending;
/** Is commit switched out. */
bool switchedOut;
/** The latency to handle a trap. Used when scheduling trap
* squash event.
*/
Tick trapLatency;
/** The commit PC of each thread. Refers to the instruction that
* is currently being processed/committed.
*/
Addr PC[Impl::MaxThreads];
/** The next PC of each thread. */
Addr nextPC[Impl::MaxThreads];
/** The sequence number of the youngest valid instruction in the ROB. */
InstSeqNum youngestSeqNum[Impl::MaxThreads];
/** Pointer to the list of active threads. */
std::list<unsigned> *activeThreads;
/** Rename map interface. */
RenameMap *renameMap[Impl::MaxThreads];
/** Updates commit stats based on this instruction. */
void updateComInstStats(DynInstPtr &inst);
/** Stat for the total number of committed instructions. */
Stats::Scalar<> commitCommittedInsts;
/** Stat for the total number of squashed instructions discarded by commit.
*/
Stats::Scalar<> commitSquashedInsts;
/** Stat for the total number of times commit is told to squash.
* @todo: Actually increment this stat.
*/
Stats::Scalar<> commitSquashEvents;
/** Stat for the total number of times commit has had to stall due to a non-
* speculative instruction reaching the head of the ROB.
*/
Stats::Scalar<> commitNonSpecStalls;
/** Stat for the total number of branch mispredicts that caused a squash. */
Stats::Scalar<> branchMispredicts;
/** Distribution of the number of committed instructions each cycle. */
Stats::Distribution<> numCommittedDist;
/** Total number of instructions committed. */
Stats::Vector<> statComInst;
/** Total number of software prefetches committed. */
Stats::Vector<> statComSwp;
/** Stat for the total number of committed memory references. */
Stats::Vector<> statComRefs;
/** Stat for the total number of committed loads. */
Stats::Vector<> statComLoads;
/** Total number of committed memory barriers. */
Stats::Vector<> statComMembars;
/** Total number of committed branches. */
Stats::Vector<> statComBranches;
/** Number of cycles where the commit bandwidth limit is reached. */
Stats::Scalar<> commitEligibleSamples;
/** Number of instructions not committed due to bandwidth limits. */
Stats::Vector<> commitEligible;
};
#endif // __CPU_O3_COMMIT_HH__