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/*
* 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.
*
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* modification, are permitted provided that the following conditions are
* met: redistributions of source code must retain the above copyright
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* neither the name of the copyright holders nor the names of its
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*
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#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"
#include "enums/CommitPolicy.hh"
#include "sim/probe/probe.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;
/** 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[Impl::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 DefaultCommit with the given parameters. */
DefaultCommit(O3CPU *_cpu, const DerivO3CPUParams &params);
/** Returns the name of the DefaultCommit. */
std::string name() const;
/** Registers probes. */
void regProbePoints();
/** 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<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 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. */
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];
/** 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];
/**
* 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[Impl::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 Reorder Buffers */
unsigned numRobs;
/** 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.
*/
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;
/** 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[Impl::MaxThreads];
int htmStops[Impl::MaxThreads];
struct CommitStats : public Stats::Group {
CommitStats(O3CPU *cpu, DefaultCommit *commit);
/** Stat for the total number of squashed instructions discarded by
* commit.
*/
Stats::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.
*/
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;
/** Stat for the total number of committed memory references. */
Stats::Vector memRefs;
/** Stat for the total number of committed loads. */
Stats::Vector loads;
/** Stat for the total number of committed atomics. */
Stats::Vector amos;
/** Total number of committed memory barriers. */
Stats::Vector membars;
/** Total number of committed branches. */
Stats::Vector branches;
/** Total number of vector instructions */
Stats::Vector vectorInstructions;
/** Total number of floating point instructions */
Stats::Vector floating;
/** Total number of integer instructions */
Stats::Vector integer;
/** Total number of function calls */
Stats::Vector functionCalls;
/** Committed instructions by instruction type (OpClass) */
Stats::Vector2d committedInstType;
/** Number of cycles where the commit bandwidth limit is reached. */
Stats::Scalar commitEligibleSamples;
} stats;
};
#endif // __CPU_O3_COMMIT_HH__