gem5/cpu/o3/rename.hh
Kevin Lim e3d5588ca7 O3 code update/cleanup.
cpu/o3/commit_impl.hh:
    O3 code update/cleanup.  Fetch fault code no longer needed (see previous checkin).

--HG--
extra : convert_revision : f602e7f978e19b8900dce482f38f9c7a195e94da
2006-05-19 15:53:17 -04:00

462 lines
16 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_RENAME_HH__
#define __CPU_O3_RENAME_HH__
#include <list>
#include "base/statistics.hh"
#include "base/timebuf.hh"
/**
* DefaultRename handles both single threaded and SMT rename. Its
* width is specified by the parameters; each cycle it tries to rename
* that many instructions. It holds onto the rename history of all
* instructions with destination registers, storing the
* arch. register, the new physical register, and the old physical
* register, to allow for undoing of mappings if squashing happens, or
* freeing up registers upon commit. Rename handles blocking if the
* ROB, IQ, or LSQ is going to be full. Rename also handles barriers,
* and does so by stalling on the instruction until the ROB is empty
* and there are no instructions in flight to the ROB.
*/
template<class Impl>
class DefaultRename
{
public:
// Typedefs from the Impl.
typedef typename Impl::CPUPol CPUPol;
typedef typename Impl::DynInstPtr DynInstPtr;
typedef typename Impl::FullCPU FullCPU;
typedef typename Impl::Params Params;
// Typedefs from the CPUPol
typedef typename CPUPol::DecodeStruct DecodeStruct;
typedef typename CPUPol::RenameStruct RenameStruct;
typedef typename CPUPol::TimeStruct TimeStruct;
typedef typename CPUPol::FreeList FreeList;
typedef typename CPUPol::RenameMap RenameMap;
// These are used only for initialization.
typedef typename CPUPol::IEW IEW;
typedef typename CPUPol::Commit Commit;
// Typedefs from the ISA.
typedef TheISA::RegIndex RegIndex;
// A list is used to queue the instructions. Barrier insts must
// be added to the front of the list, which is the only reason for
// using a list instead of a queue. (Most other stages use a
// queue)
typedef std::list<DynInstPtr> InstQueue;
public:
/** Overall rename status. Used to determine if the CPU can
* deschedule itself due to a lack of activity.
*/
enum RenameStatus {
Active,
Inactive
};
/** Individual thread status. */
enum ThreadStatus {
Running,
Idle,
StartSquash,
Squashing,
Blocked,
Unblocking,
SerializeStall
};
private:
/** Rename status. */
RenameStatus _status;
/** Per-thread status. */
ThreadStatus renameStatus[Impl::MaxThreads];
public:
/** DefaultRename constructor. */
DefaultRename(Params *params);
/** Returns the name of rename. */
std::string name() const;
/** Registers statistics. */
void regStats();
/** Sets CPU pointer. */
void setCPU(FullCPU *cpu_ptr);
/** Sets the main backwards communication time buffer pointer. */
void setTimeBuffer(TimeBuffer<TimeStruct> *tb_ptr);
/** Sets pointer to time buffer used to communicate to the next stage. */
void setRenameQueue(TimeBuffer<RenameStruct> *rq_ptr);
/** Sets pointer to time buffer coming from decode. */
void setDecodeQueue(TimeBuffer<DecodeStruct> *dq_ptr);
/** Sets pointer to IEW stage. Used only for initialization. */
void setIEWStage(IEW *iew_stage)
{ iew_ptr = iew_stage; }
/** Sets pointer to commit stage. Used only for initialization. */
void setCommitStage(Commit *commit_stage)
{ commit_ptr = commit_stage; }
private:
/** Pointer to IEW stage. Used only for initialization. */
IEW *iew_ptr;
/** Pointer to commit stage. Used only for initialization. */
Commit *commit_ptr;
public:
/** Initializes variables for the stage. */
void initStage();
/** Sets pointer to list of active threads. */
void setActiveThreads(std::list<unsigned> *at_ptr);
/** Sets pointer to rename maps (per-thread structures). */
void setRenameMap(RenameMap rm_ptr[Impl::MaxThreads]);
/** Sets pointer to the free list. */
void setFreeList(FreeList *fl_ptr);
/** Sets pointer to the scoreboard. */
void setScoreboard(Scoreboard *_scoreboard);
void switchOut();
void doSwitchOut();
void takeOverFrom();
/** Squashes all instructions in a thread. */
void squash(unsigned tid);
/** Ticks rename, which processes all input signals and attempts to rename
* as many instructions as possible.
*/
void tick();
/** Debugging function used to dump history buffer of renamings. */
void dumpHistory();
private:
/** Determines what to do based on rename's current status.
* @param status_change rename() sets this variable if there was a status
* change (ie switching from blocking to unblocking).
* @param tid Thread id to rename instructions from.
*/
void rename(bool &status_change, unsigned tid);
/** Renames instructions for the given thread. Also handles serializing
* instructions.
*/
void renameInsts(unsigned tid);
/** Inserts unused instructions from a given thread into the skid buffer,
* to be renamed once rename unblocks.
*/
void skidInsert(unsigned tid);
/** Separates instructions from decode into individual lists of instructions
* sorted by thread.
*/
void sortInsts();
/** Returns if all of the skid buffers are empty. */
bool skidsEmpty();
/** Updates overall rename status based on all of the threads' statuses. */
void updateStatus();
/** Switches rename to blocking, and signals back that rename has become
* blocked.
* @return Returns true if there is a status change.
*/
bool block(unsigned tid);
/** Switches rename to unblocking if the skid buffer is empty, and signals
* back that rename has unblocked.
* @return Returns true if there is a status change.
*/
bool unblock(unsigned tid);
/** Executes actual squash, removing squashed instructions. */
void doSquash(unsigned tid);
/** Removes a committed instruction's rename history. */
void removeFromHistory(InstSeqNum inst_seq_num, unsigned tid);
/** Renames the source registers of an instruction. */
inline void renameSrcRegs(DynInstPtr &inst, unsigned tid);
/** Renames the destination registers of an instruction. */
inline void renameDestRegs(DynInstPtr &inst, unsigned tid);
/** Calculates the number of free ROB entries for a specific thread. */
inline int calcFreeROBEntries(unsigned tid);
/** Calculates the number of free IQ entries for a specific thread. */
inline int calcFreeIQEntries(unsigned tid);
/** Calculates the number of free LSQ entries for a specific thread. */
inline int calcFreeLSQEntries(unsigned tid);
/** Returns the number of valid instructions coming from decode. */
unsigned validInsts();
/** Reads signals telling rename to block/unblock. */
void readStallSignals(unsigned tid);
/** Checks if any stages are telling rename to block. */
bool checkStall(unsigned tid);
void readFreeEntries(unsigned tid);
bool checkSignalsAndUpdate(unsigned tid);
/** Either serializes on the next instruction available in the InstQueue,
* or records that it must serialize on the next instruction to enter
* rename.
* @param inst_list The list of younger, unprocessed instructions for the
* thread that has the serializeAfter instruction.
* @param tid The thread id.
*/
void serializeAfter(InstQueue &inst_list, unsigned tid);
/** Holds the information for each destination register rename. It holds
* the instruction's sequence number, the arch register, the old physical
* register for that arch. register, and the new physical register.
*/
struct RenameHistory {
RenameHistory(InstSeqNum _instSeqNum, RegIndex _archReg,
PhysRegIndex _newPhysReg, PhysRegIndex _prevPhysReg)
: instSeqNum(_instSeqNum), archReg(_archReg),
newPhysReg(_newPhysReg), prevPhysReg(_prevPhysReg)
{
}
/** The sequence number of the instruction that renamed. */
InstSeqNum instSeqNum;
/** The architectural register index that was renamed. */
RegIndex archReg;
/** The new physical register that the arch. register is renamed to. */
PhysRegIndex newPhysReg;
/** The old physical register that the arch. register was renamed to. */
PhysRegIndex prevPhysReg;
};
/** A per-thread list of all destination register renames, used to either
* undo rename mappings or free old physical registers.
*/
std::list<RenameHistory> historyBuffer[Impl::MaxThreads];
/** Pointer to CPU. */
FullCPU *cpu;
/** Pointer to main time buffer used for backwards communication. */
TimeBuffer<TimeStruct> *timeBuffer;
/** Wire to get IEW's output from backwards time buffer. */
typename TimeBuffer<TimeStruct>::wire fromIEW;
/** Wire to get commit's output from backwards time buffer. */
typename TimeBuffer<TimeStruct>::wire fromCommit;
/** Wire to write infromation heading to previous stages. */
typename TimeBuffer<TimeStruct>::wire toDecode;
/** Rename instruction queue. */
TimeBuffer<RenameStruct> *renameQueue;
/** Wire to write any information heading to IEW. */
typename TimeBuffer<RenameStruct>::wire toIEW;
/** Decode instruction queue interface. */
TimeBuffer<DecodeStruct> *decodeQueue;
/** Wire to get decode's output from decode queue. */
typename TimeBuffer<DecodeStruct>::wire fromDecode;
/** Queue of all instructions coming from decode this cycle. */
InstQueue insts[Impl::MaxThreads];
/** Skid buffer between rename and decode. */
InstQueue skidBuffer[Impl::MaxThreads];
/** Rename map interface. */
RenameMap *renameMap[Impl::MaxThreads];
/** Free list interface. */
FreeList *freeList;
/** Pointer to the list of active threads. */
std::list<unsigned> *activeThreads;
/** Pointer to the scoreboard. */
Scoreboard *scoreboard;
/** Count of instructions in progress that have been sent off to the IQ
* and ROB, but are not yet included in their occupancy counts.
*/
int instsInProgress[Impl::MaxThreads];
/** Variable that tracks if decode has written to the time buffer this
* cycle. Used to tell CPU if there is activity this cycle.
*/
bool wroteToTimeBuffer;
/** Structures whose free entries impact the amount of instructions that
* can be renamed.
*/
struct FreeEntries {
unsigned iqEntries;
unsigned lsqEntries;
unsigned robEntries;
};
/** Per-thread tracking of the number of free entries of back-end
* structures.
*/
FreeEntries freeEntries[Impl::MaxThreads];
/** Records if the ROB is empty. In SMT mode the ROB may be dynamically
* partitioned between threads, so the ROB must tell rename when it is
* empty.
*/
bool emptyROB[Impl::MaxThreads];
/** Source of possible stalls. */
struct Stalls {
bool iew;
bool commit;
};
/** Tracks which stages are telling decode to stall. */
Stalls stalls[Impl::MaxThreads];
/** The serialize instruction that rename has stalled on. */
DynInstPtr serializeInst[Impl::MaxThreads];
/** Records if rename needs to serialize on the next instruction for any
* thread.
*/
bool serializeOnNextInst[Impl::MaxThreads];
/** Delay between iew and rename, in ticks. */
int iewToRenameDelay;
/** Delay between decode and rename, in ticks. */
int decodeToRenameDelay;
/** Delay between commit and rename, in ticks. */
unsigned commitToRenameDelay;
/** Rename width, in instructions. */
unsigned renameWidth;
/** Commit width, in instructions. Used so rename knows how many
* instructions might have freed registers in the previous cycle.
*/
unsigned commitWidth;
/** The index of the instruction in the time buffer to IEW that rename is
* currently using.
*/
unsigned toIEWIndex;
/** Whether or not rename needs to block this cycle. */
bool blockThisCycle;
/** The number of threads active in rename. */
unsigned numThreads;
/** The maximum skid buffer size. */
unsigned skidBufferMax;
/** Enum to record the source of a structure full stall. Can come from
* either ROB, IQ, LSQ, and it is priortized in that order.
*/
enum FullSource {
ROB,
IQ,
LSQ,
NONE
};
/** Function used to increment the stat that corresponds to the source of
* the stall.
*/
inline void incrFullStat(const FullSource &source);
/** Stat for total number of cycles spent squashing. */
Stats::Scalar<> renameSquashCycles;
/** Stat for total number of cycles spent idle. */
Stats::Scalar<> renameIdleCycles;
/** Stat for total number of cycles spent blocking. */
Stats::Scalar<> renameBlockCycles;
/** Stat for total number of cycles spent stalling for a serializing inst. */
Stats::Scalar<> renameSerializeStallCycles;
/** Stat for total number of cycles spent running normally. */
Stats::Scalar<> renameRunCycles;
/** Stat for total number of cycles spent unblocking. */
Stats::Scalar<> renameUnblockCycles;
/** Stat for total number of renamed instructions. */
Stats::Scalar<> renameRenamedInsts;
/** Stat for total number of squashed instructions that rename discards. */
Stats::Scalar<> renameSquashedInsts;
/** Stat for total number of times that the ROB starts a stall in rename. */
Stats::Scalar<> renameROBFullEvents;
/** Stat for total number of times that the IQ starts a stall in rename. */
Stats::Scalar<> renameIQFullEvents;
/** Stat for total number of times that the LSQ starts a stall in rename. */
Stats::Scalar<> renameLSQFullEvents;
/** Stat for total number of times that rename runs out of free registers
* to use to rename. */
Stats::Scalar<> renameFullRegistersEvents;
/** Stat for total number of renamed destination registers. */
Stats::Scalar<> renameRenamedOperands;
/** Stat for total number of source register rename lookups. */
Stats::Scalar<> renameRenameLookups;
/** Stat for total number of committed renaming mappings. */
Stats::Scalar<> renameCommittedMaps;
/** Stat for total number of mappings that were undone due to a squash. */
Stats::Scalar<> renameUndoneMaps;
Stats::Scalar<> renamedSerializing;
Stats::Scalar<> renamedTempSerializing;
Stats::Scalar<> renameSkidInsts;
};
#endif // __CPU_O3_RENAME_HH__