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/*
* Copyright (c) 2010-2012, 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.
*
* 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_FETCH_HH__
#define __CPU_O3_FETCH_HH__
#include "arch/decoder.hh"
#include "arch/utility.hh"
#include "base/statistics.hh"
#include "config/the_isa.hh"
#include "cpu/pc_event.hh"
#include "cpu/pred/bpred_unit.hh"
#include "cpu/timebuf.hh"
#include "cpu/translation.hh"
#include "enums/FetchPolicy.hh"
#include "mem/packet.hh"
#include "mem/port.hh"
#include "sim/eventq.hh"
#include "sim/probe/probe.hh"
struct DerivO3CPUParams;
/**
* DefaultFetch class handles both single threaded and SMT fetch. Its
* width is specified by the parameters; each cycle it tries to fetch
* that many instructions. It supports using a branch predictor to
* predict direction and targets.
* It supports the idling functionality of the CPU by indicating to
* the CPU when it is active and inactive.
*/
template <class Impl>
class DefaultFetch
{
public:
/** Typedefs from Impl. */
typedef typename Impl::CPUPol CPUPol;
typedef typename Impl::DynInst DynInst;
typedef typename Impl::DynInstPtr DynInstPtr;
typedef typename Impl::O3CPU O3CPU;
/** Typedefs from the CPU policy. */
typedef typename CPUPol::FetchStruct FetchStruct;
typedef typename CPUPol::TimeStruct TimeStruct;
/** Typedefs from ISA. */
typedef TheISA::MachInst MachInst;
class FetchTranslation : public BaseTLB::Translation
{
protected:
DefaultFetch<Impl> *fetch;
public:
FetchTranslation(DefaultFetch<Impl> *_fetch)
: fetch(_fetch)
{}
void
markDelayed()
{}
void
finish(const Fault &fault, const RequestPtr &req, ThreadContext *tc,
BaseTLB::Mode mode)
{
assert(mode == BaseTLB::Execute);
fetch->finishTranslation(fault, req);
delete this;
}
};
private:
/* Event to delay delivery of a fetch translation result in case of
* a fault and the nop to carry the fault cannot be generated
* immediately */
class FinishTranslationEvent : public Event
{
private:
DefaultFetch<Impl> *fetch;
Fault fault;
RequestPtr req;
public:
FinishTranslationEvent(DefaultFetch<Impl> *_fetch)
: fetch(_fetch), req(nullptr)
{}
void setFault(Fault _fault)
{
fault = _fault;
}
void setReq(const RequestPtr &_req)
{
req = _req;
}
/** Process the delayed finish translation */
void process()
{
assert(fetch->numInst < fetch->fetchWidth);
fetch->finishTranslation(fault, req);
}
const char *description() const
{
return "FullO3CPU FetchFinishTranslation";
}
};
public:
/** Overall fetch status. Used to determine if the CPU can
* deschedule itsef due to a lack of activity.
*/
enum FetchStatus {
Active,
Inactive
};
/** Individual thread status. */
enum ThreadStatus {
Running,
Idle,
Squashing,
Blocked,
Fetching,
TrapPending,
QuiescePending,
ItlbWait,
IcacheWaitResponse,
IcacheWaitRetry,
IcacheAccessComplete,
NoGoodAddr
};
private:
/** Fetch status. */
FetchStatus _status;
/** Per-thread status. */
ThreadStatus fetchStatus[Impl::MaxThreads];
/** Fetch policy. */
FetchPolicy fetchPolicy;
/** List that has the threads organized by priority. */
std::list<ThreadID> priorityList;
/** Probe points. */
ProbePointArg<DynInstPtr> *ppFetch;
/** To probe when a fetch request is successfully sent. */
ProbePointArg<RequestPtr> *ppFetchRequestSent;
public:
/** DefaultFetch constructor. */
DefaultFetch(O3CPU *_cpu, DerivO3CPUParams *params);
/** Returns the name of fetch. */
std::string name() const;
/** Registers statistics. */
void regStats();
/** Registers probes. */
void regProbePoints();
/** Sets the main backwards communication time buffer pointer. */
void setTimeBuffer(TimeBuffer<TimeStruct> *time_buffer);
/** Sets pointer to list of active threads. */
void setActiveThreads(std::list<ThreadID> *at_ptr);
/** Sets pointer to time buffer used to communicate to the next stage. */
void setFetchQueue(TimeBuffer<FetchStruct> *fq_ptr);
/** Initialize stage. */
void startupStage();
/** Handles retrying the fetch access. */
void recvReqRetry();
/** Processes cache completion event. */
void processCacheCompletion(PacketPtr pkt);
/** Resume after a drain. */
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();
/**
* Stall the fetch stage after reaching a safe drain point.
*
* The CPU uses this method to stop fetching instructions from a
* thread that has been drained. The drain stall is different from
* all other stalls in that it is signaled instantly from the
* commit stage (without the normal communication delay) when it
* has reached a safe point to drain from.
*/
void drainStall(ThreadID tid);
/** Tells fetch to wake up from a quiesce instruction. */
void wakeFromQuiesce();
/** For priority-based fetch policies, need to keep update priorityList */
void deactivateThread(ThreadID tid);
private:
/** Reset this pipeline stage */
void resetStage();
/** Changes the status of this stage to active, and indicates this
* to the CPU.
*/
inline void switchToActive();
/** Changes the status of this stage to inactive, and indicates
* this to the CPU.
*/
inline void switchToInactive();
/**
* Looks up in the branch predictor to see if the next PC should be
* either next PC+=MachInst or a branch target.
* @param next_PC Next PC variable passed in by reference. It is
* expected to be set to the current PC; it will be updated with what
* the next PC will be.
* @param next_NPC Used for ISAs which use delay slots.
* @return Whether or not a branch was predicted as taken.
*/
bool lookupAndUpdateNextPC(const DynInstPtr &inst, TheISA::PCState &pc);
/**
* Fetches the cache line that contains the fetch PC. Returns any
* fault that happened. Puts the data into the class variable
* fetchBuffer, which may not hold the entire fetched cache line.
* @param vaddr The memory address that is being fetched from.
* @param ret_fault The fault reference that will be set to the result of
* the icache access.
* @param tid Thread id.
* @param pc The actual PC of the current instruction.
* @return Any fault that occured.
*/
bool fetchCacheLine(Addr vaddr, ThreadID tid, Addr pc);
void finishTranslation(const Fault &fault, const RequestPtr &mem_req);
/** Check if an interrupt is pending and that we need to handle
*/
bool
checkInterrupt(Addr pc)
{
return (interruptPending && (THE_ISA != ALPHA_ISA || !(pc & 0x3)));
}
/** Squashes a specific thread and resets the PC. */
inline void doSquash(const TheISA::PCState &newPC,
const DynInstPtr squashInst, ThreadID tid);
/** Squashes a specific thread and resets the PC. Also tells the CPU to
* remove any instructions between fetch and decode that should be sqaushed.
*/
void squashFromDecode(const TheISA::PCState &newPC,
const DynInstPtr squashInst,
const InstSeqNum seq_num, ThreadID tid);
/** Checks if a thread is stalled. */
bool checkStall(ThreadID tid) const;
/** Updates overall fetch stage status; to be called at the end of each
* cycle. */
FetchStatus updateFetchStatus();
public:
/** Squashes a specific thread and resets the PC. Also tells the CPU to
* remove any instructions that are not in the ROB. The source of this
* squash should be the commit stage.
*/
void squash(const TheISA::PCState &newPC, const InstSeqNum seq_num,
DynInstPtr squashInst, ThreadID tid);
/** Ticks the fetch stage, processing all inputs signals and fetching
* as many instructions as possible.
*/
void tick();
/** Checks all input signals and updates the status as necessary.
* @return: Returns if the status has changed due to input signals.
*/
bool checkSignalsAndUpdate(ThreadID tid);
/** Does the actual fetching of instructions and passing them on to the
* next stage.
* @param status_change fetch() sets this variable if there was a status
* change (ie switching to IcacheMissStall).
*/
void fetch(bool &status_change);
/** Align a PC to the start of a fetch buffer block. */
Addr fetchBufferAlignPC(Addr addr)
{
return (addr & ~(fetchBufferMask));
}
/** The decoder. */
TheISA::Decoder *decoder[Impl::MaxThreads];
private:
DynInstPtr buildInst(ThreadID tid, StaticInstPtr staticInst,
StaticInstPtr curMacroop, TheISA::PCState thisPC,
TheISA::PCState nextPC, bool trace);
/** Returns the appropriate thread to fetch, given the fetch policy. */
ThreadID getFetchingThread();
/** Returns the appropriate thread to fetch using a round robin policy. */
ThreadID roundRobin();
/** Returns the appropriate thread to fetch using the IQ count policy. */
ThreadID iqCount();
/** Returns the appropriate thread to fetch using the LSQ count policy. */
ThreadID lsqCount();
/** Returns the appropriate thread to fetch using the branch count
* policy. */
ThreadID branchCount();
/** Pipeline the next I-cache access to the current one. */
void pipelineIcacheAccesses(ThreadID tid);
/** Profile the reasons of fetch stall. */
void profileStall(ThreadID tid);
private:
/** Pointer to the O3CPU. */
O3CPU *cpu;
/** Time buffer interface. */
TimeBuffer<TimeStruct> *timeBuffer;
/** Wire to get decode's information from backwards time buffer. */
typename TimeBuffer<TimeStruct>::wire fromDecode;
/** Wire to get rename's information from backwards time buffer. */
typename TimeBuffer<TimeStruct>::wire fromRename;
/** Wire to get iew's information from backwards time buffer. */
typename TimeBuffer<TimeStruct>::wire fromIEW;
/** Wire to get commit's information from backwards time buffer. */
typename TimeBuffer<TimeStruct>::wire fromCommit;
//Might be annoying how this name is different than the queue.
/** Wire used to write any information heading to decode. */
typename TimeBuffer<FetchStruct>::wire toDecode;
/** BPredUnit. */
BPredUnit *branchPred;
TheISA::PCState pc[Impl::MaxThreads];
Addr fetchOffset[Impl::MaxThreads];
StaticInstPtr macroop[Impl::MaxThreads];
/** Can the fetch stage redirect from an interrupt on this instruction? */
bool delayedCommit[Impl::MaxThreads];
/** Memory request used to access cache. */
RequestPtr memReq[Impl::MaxThreads];
/** Variable that tracks if fetch has written to the time buffer this
* cycle. Used to tell CPU if there is activity this cycle.
*/
bool wroteToTimeBuffer;
/** Tracks how many instructions has been fetched this cycle. */
int numInst;
/** Source of possible stalls. */
struct Stalls {
bool decode;
bool drain;
};
/** Tracks which stages are telling fetch to stall. */
Stalls stalls[Impl::MaxThreads];
/** Decode to fetch delay. */
Cycles decodeToFetchDelay;
/** Rename to fetch delay. */
Cycles renameToFetchDelay;
/** IEW to fetch delay. */
Cycles iewToFetchDelay;
/** Commit to fetch delay. */
Cycles commitToFetchDelay;
/** The width of fetch in instructions. */
unsigned fetchWidth;
/** The width of decode in instructions. */
unsigned decodeWidth;
/** Is the cache blocked? If so no threads can access it. */
bool cacheBlocked;
/** The packet that is waiting to be retried. */
PacketPtr retryPkt;
/** The thread that is waiting on the cache to tell fetch to retry. */
ThreadID retryTid;
/** Cache block size. */
unsigned int cacheBlkSize;
/** The size of the fetch buffer in bytes. The fetch buffer
* itself may be smaller than a cache line.
*/
unsigned fetchBufferSize;
/** Mask to align a fetch address to a fetch buffer boundary. */
Addr fetchBufferMask;
/** The fetch data that is being fetched and buffered. */
uint8_t *fetchBuffer[Impl::MaxThreads];
/** The PC of the first instruction loaded into the fetch buffer. */
Addr fetchBufferPC[Impl::MaxThreads];
/** The size of the fetch queue in micro-ops */
unsigned fetchQueueSize;
/** Queue of fetched instructions. Per-thread to prevent HoL blocking. */
std::deque<DynInstPtr> fetchQueue[Impl::MaxThreads];
/** Whether or not the fetch buffer data is valid. */
bool fetchBufferValid[Impl::MaxThreads];
/** Size of instructions. */
int instSize;
/** Icache stall statistics. */
Counter lastIcacheStall[Impl::MaxThreads];
/** List of Active Threads */
std::list<ThreadID> *activeThreads;
/** Number of threads. */
ThreadID numThreads;
/** Number of threads that are actively fetching. */
ThreadID numFetchingThreads;
/** Thread ID being fetched. */
ThreadID threadFetched;
/** Checks if there is an interrupt pending. If there is, fetch
* must stop once it is not fetching PAL instructions.
*/
bool interruptPending;
/** Set to true if a pipelined I-cache request should be issued. */
bool issuePipelinedIfetch[Impl::MaxThreads];
/** Event used to delay fault generation of translation faults */
FinishTranslationEvent finishTranslationEvent;
// @todo: Consider making these vectors and tracking on a per thread basis.
/** Stat for total number of cycles stalled due to an icache miss. */
Stats::Scalar icacheStallCycles;
/** Stat for total number of fetched instructions. */
Stats::Scalar fetchedInsts;
/** Total number of fetched branches. */
Stats::Scalar fetchedBranches;
/** Stat for total number of predicted branches. */
Stats::Scalar predictedBranches;
/** Stat for total number of cycles spent fetching. */
Stats::Scalar fetchCycles;
/** Stat for total number of cycles spent squashing. */
Stats::Scalar fetchSquashCycles;
/** Stat for total number of cycles spent waiting for translation */
Stats::Scalar fetchTlbCycles;
/** Stat for total number of cycles spent blocked due to other stages in
* the pipeline.
*/
Stats::Scalar fetchIdleCycles;
/** Total number of cycles spent blocked. */
Stats::Scalar fetchBlockedCycles;
/** Total number of cycles spent in any other state. */
Stats::Scalar fetchMiscStallCycles;
/** Total number of cycles spent in waiting for drains. */
Stats::Scalar fetchPendingDrainCycles;
/** Total number of stall cycles caused by no active threads to run. */
Stats::Scalar fetchNoActiveThreadStallCycles;
/** Total number of stall cycles caused by pending traps. */
Stats::Scalar fetchPendingTrapStallCycles;
/** Total number of stall cycles caused by pending quiesce instructions. */
Stats::Scalar fetchPendingQuiesceStallCycles;
/** Total number of stall cycles caused by I-cache wait retrys. */
Stats::Scalar fetchIcacheWaitRetryStallCycles;
/** Stat for total number of fetched cache lines. */
Stats::Scalar fetchedCacheLines;
/** Total number of outstanding icache accesses that were dropped
* due to a squash.
*/
Stats::Scalar fetchIcacheSquashes;
/** Total number of outstanding tlb accesses that were dropped
* due to a squash.
*/
Stats::Scalar fetchTlbSquashes;
/** Distribution of number of instructions fetched each cycle. */
Stats::Distribution fetchNisnDist;
/** Rate of how often fetch was idle. */
Stats::Formula idleRate;
/** Number of branch fetches per cycle. */
Stats::Formula branchRate;
/** Number of instruction fetched per cycle. */
Stats::Formula fetchRate;
};
#endif //__CPU_O3_FETCH_HH__