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/*
* Copyright (c) 2010 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.
*
* Authors: Kevin Lim
* Korey Sewell
*/
#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/timebuf.hh"
struct DerivO3CPUParams;
template <class>
struct 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::O3CPU O3CPU;
typedef typename Impl::DynInstPtr DynInstPtr;
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;
ThreadID tid;
public:
TrapEvent(DefaultCommit<Impl> *_commit, ThreadID _tid);
void process();
const char *description() const;
};
/** 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(O3CPU *_cpu, DerivO3CPUParams *params);
/** Returns the name of the DefaultCommit. */
std::string name() const;
/** Registers statistics. */
void regStats();
/** 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);
/** Skid buffer between rename and commit. */
std::queue<DynInstPtr> skidBuffer;
/** 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(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 draining of commit. */
bool drain();
/** Resumes execution after draining. */
void resume();
/** Completes the switch out of commit. */
void switchOut();
/** 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. */
size_t numROBFreeEntries(ThreadID tid);
/** Generates an event to schedule a squash due to a trap. */
void generateTrapEvent(ThreadID tid);
/** 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();
/** 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(ThreadID tid);
/** Handles squashing due to a trap. */
void squashFromTrap(ThreadID tid);
/** Handles squashing due to an TC write. */
void squashFromTC(ThreadID tid);
/** Handles 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.
*/
void squashAfter(ThreadID tid, DynInstPtr &head_inst,
uint64_t squash_after_seq_num);
/** 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(DynInstPtr &head_inst, unsigned inst_num);
/** Gets instructions from rename and inserts them into the ROB. */
void getInsts();
/** Insert all instructions from rename into skidBuffer */
void skidInsert();
/** 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. */
TheISA::PCState pcState(ThreadID tid) { return pc[tid]; }
/** Sets the PC of a specific thread. */
void pcState(const TheISA::PCState &val, ThreadID tid)
{ pc[tid] = val; }
/** Returns the PC of a specific thread. */
Addr instAddr(ThreadID tid) { return pc[tid].instAddr(); }
/** Returns the next PC of a specific thread. */
Addr nextInstAddr(ThreadID tid) { return pc[tid].nextInstAddr(); }
/** Reads the micro PC of a specific thread. */
Addr microPC(ThreadID tid) { return pc[tid].microPC(); }
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 O3CPU. */
O3CPU *cpu;
/** Vector of all of the threads. */
std::vector<Thread *> 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[Impl::MaxThreads];
/** A counter of how many threads are currently squashing. */
ThreadID 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 tcSquash[Impl::MaxThreads];
/** Priority List used for Commit Policy */
std::list<ThreadID> priority_list;
/** IEW to Commit delay. */
Cycles iewToCommitDelay;
/** Commit to IEW delay. */
Cycles commitToIEWDelay;
/** Rename to ROB delay. */
Cycles renameToROBDelay;
Cycles 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 */
ThreadID numThreads;
/** Is a drain pending. */
bool drainPending;
/** Is commit switched out. */
bool switchedOut;
/** The latency to handle a trap. Used when scheduling trap
* squash event.
*/
Cycles trapLatency;
/** The interrupt fault. */
Fault interrupt;
/** The commit PC state of each thread. Refers to the instruction that
* is currently being processed/committed.
*/
TheISA::PCState pc[Impl::MaxThreads];
/** The sequence number of the youngest valid instruction in the ROB. */
InstSeqNum youngestSeqNum[Impl::MaxThreads];
/** The sequence number of the last commited instruction. */
InstSeqNum lastCommitedSeqNum[Impl::MaxThreads];
/** Records if there is a trap currently in flight. */
bool trapInFlight[Impl::MaxThreads];
/** Records if there were any stores committed this cycle. */
bool committedStores[Impl::MaxThreads];
/** Records if commit should check if the ROB is truly empty (see
commit_impl.hh). */
bool checkEmptyROB[Impl::MaxThreads];
/** Pointer to the list of active threads. */
std::list<ThreadID> *activeThreads;
/** Rename map interface. */
RenameMap *renameMap[Impl::MaxThreads];
/** True if last committed microop can be followed by an interrupt */
bool canHandleInterrupts;
/** Updates commit stats based on this instruction. */
void updateComInstStats(DynInstPtr &inst);
/** 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 instsCommitted;
/** Total number of ops (including micro ops) committed. */
Stats::Vector opsCommitted;
/** 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;
/** Total number of floating point instructions */
Stats::Vector statComFloating;
/** Total number of integer instructions */
Stats::Vector statComInteger;
/** Total number of function calls */
Stats::Vector statComFunctionCalls;
/** 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__
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