/* * Copyright (c) 2004-2005 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_LSQ_UNIT_HH__ #define __CPU_O3_LSQ_UNIT_HH__ #include #include #include #include "config/full_system.hh" #include "base/hashmap.hh" #include "cpu/inst_seq.hh" #include "mem/mem_interface.hh" //#include "mem/page_table.hh" #include "sim/sim_object.hh" #include "arch/faults.hh" /** * Class that implements the actual LQ and SQ for each specific thread. * Both are circular queues; load entries are freed upon committing, while * store entries are freed once they writeback. The LSQUnit tracks if there * are memory ordering violations, and also detects partial load to store * forwarding cases (a store only has part of a load's data) that requires * the load to wait until the store writes back. In the former case it * holds onto the instruction until the dependence unit looks at it, and * in the latter it stalls the LSQ until the store writes back. At that * point the load is replayed. */ template class LSQUnit { protected: typedef TheISA::IntReg IntReg; public: typedef typename Impl::Params Params; typedef typename Impl::FullCPU FullCPU; typedef typename Impl::DynInstPtr DynInstPtr; typedef typename Impl::CPUPol::IEW IEW; typedef typename Impl::CPUPol::IssueStruct IssueStruct; private: class StoreCompletionEvent : public Event { public: /** Constructs a store completion event. */ StoreCompletionEvent(int store_idx, Event *wb_event, LSQUnit *lsq_ptr); /** Processes the store completion event. */ void process(); /** Returns the description of this event. */ const char *description(); private: /** The store index of the store being written back. */ int storeIdx; /** The writeback event for the store. Needed for store * conditionals. */ Event *wbEvent; /** The pointer to the LSQ unit that issued the store. */ LSQUnit *lsqPtr; }; friend class StoreCompletionEvent; public: /** Constructs an LSQ unit. init() must be called prior to use. */ LSQUnit(); /** Initializes the LSQ unit with the specified number of entries. */ void init(Params *params, unsigned maxLQEntries, unsigned maxSQEntries, unsigned id); /** Returns the name of the LSQ unit. */ std::string name() const; /** Sets the CPU pointer. */ void setCPU(FullCPU *cpu_ptr) { cpu = cpu_ptr; } /** Sets the IEW stage pointer. */ void setIEW(IEW *iew_ptr) { iewStage = iew_ptr; } /** Sets the page table pointer. */ // void setPageTable(PageTable *pt_ptr); /** Ticks the LSQ unit, which in this case only resets the number of * used cache ports. * @todo: Move the number of used ports up to the LSQ level so it can * be shared by all LSQ units. */ void tick() { usedPorts = 0; } /** Inserts an instruction. */ void insert(DynInstPtr &inst); /** Inserts a load instruction. */ void insertLoad(DynInstPtr &load_inst); /** Inserts a store instruction. */ void insertStore(DynInstPtr &store_inst); /** Executes a load instruction. */ Fault executeLoad(DynInstPtr &inst); Fault executeLoad(int lq_idx); /** Executes a store instruction. */ Fault executeStore(DynInstPtr &inst); /** Commits the head load. */ void commitLoad(); /** Commits a specific load, given by the sequence number. */ void commitLoad(InstSeqNum &inst); /** Commits loads older than a specific sequence number. */ void commitLoads(InstSeqNum &youngest_inst); /** Commits stores older than a specific sequence number. */ void commitStores(InstSeqNum &youngest_inst); /** Writes back stores. */ void writebackStores(); // @todo: Include stats in the LSQ unit. //void regStats(); /** Clears all the entries in the LQ. */ void clearLQ(); /** Clears all the entries in the SQ. */ void clearSQ(); /** Resizes the LQ to a given size. */ void resizeLQ(unsigned size); /** Resizes the SQ to a given size. */ void resizeSQ(unsigned size); /** Squashes all instructions younger than a specific sequence number. */ void squash(const InstSeqNum &squashed_num); /** Returns if there is a memory ordering violation. Value is reset upon * call to getMemDepViolator(). */ bool violation() { return memDepViolator; } /** Returns the memory ordering violator. */ DynInstPtr getMemDepViolator(); /** Returns if a load became blocked due to the memory system. It clears * the bool's value upon this being called. */ bool loadBlocked() { return isLoadBlocked; } void clearLoadBlocked() { isLoadBlocked = false; } bool isLoadBlockedHandled() { return loadBlockedHandled; } void setLoadBlockedHandled() { loadBlockedHandled = true; } /** Returns the number of free entries (min of free LQ and SQ entries). */ unsigned numFreeEntries(); /** Returns the number of loads ready to execute. */ int numLoadsReady(); /** Returns the number of loads in the LQ. */ int numLoads() { return loads; } /** Returns the number of stores in the SQ. */ int numStores() { return stores; } /** Returns if either the LQ or SQ is full. */ bool isFull() { return lqFull() || sqFull(); } /** Returns if the LQ is full. */ bool lqFull() { return loads >= (LQEntries - 1); } /** Returns if the SQ is full. */ bool sqFull() { return stores >= (SQEntries - 1); } /** Debugging function to dump instructions in the LSQ. */ void dumpInsts(); /** Returns the number of instructions in the LSQ. */ unsigned getCount() { return loads + stores; } /** Returns if there are any stores to writeback. */ bool hasStoresToWB() { return storesToWB; } /** Returns the number of stores to writeback. */ int numStoresToWB() { return storesToWB; } /** Returns if the LSQ unit will writeback on this cycle. */ bool willWB() { return storeQueue[storeWBIdx].canWB && !storeQueue[storeWBIdx].completed && !dcacheInterface->isBlocked(); } private: /** Completes the store at the specified index. */ void completeStore(int store_idx); /** Increments the given store index (circular queue). */ inline void incrStIdx(int &store_idx); /** Decrements the given store index (circular queue). */ inline void decrStIdx(int &store_idx); /** Increments the given load index (circular queue). */ inline void incrLdIdx(int &load_idx); /** Decrements the given load index (circular queue). */ inline void decrLdIdx(int &load_idx); private: /** Pointer to the CPU. */ FullCPU *cpu; /** Pointer to the IEW stage. */ IEW *iewStage; /** Pointer to the D-cache. */ MemInterface *dcacheInterface; /** Pointer to the page table. */ // PageTable *pTable; public: struct SQEntry { /** Constructs an empty store queue entry. */ SQEntry() : inst(NULL), req(NULL), size(0), data(0), canWB(0), committed(0), completed(0) { } /** Constructs a store queue entry for a given instruction. */ SQEntry(DynInstPtr &_inst) : inst(_inst), req(NULL), size(0), data(0), canWB(0), committed(0), completed(0) { } /** The store instruction. */ DynInstPtr inst; /** The memory request for the store. */ MemReqPtr req; /** The size of the store. */ int size; /** The store data. */ IntReg data; /** Whether or not the store can writeback. */ bool canWB; /** Whether or not the store is committed. */ bool committed; /** Whether or not the store is completed. */ bool completed; }; enum Status { Running, Idle, DcacheMissStall, DcacheMissSwitch }; private: /** The LSQUnit thread id. */ unsigned lsqID; /** The status of the LSQ unit. */ Status _status; /** The store queue. */ std::vector storeQueue; /** The load queue. */ std::vector loadQueue; // Consider making these 16 bits /** The number of LQ entries. */ unsigned LQEntries; /** The number of SQ entries. */ unsigned SQEntries; /** The number of load instructions in the LQ. */ int loads; /** The number of store instructions in the SQ (excludes those waiting to * writeback). */ int stores; /** The number of store instructions in the SQ waiting to writeback. */ int storesToWB; /** The index of the head instruction in the LQ. */ int loadHead; /** The index of the tail instruction in the LQ. */ int loadTail; /** The index of the head instruction in the SQ. */ int storeHead; /** The index of the first instruction that is ready to be written back, * and has not yet been written back. */ int storeWBIdx; /** The index of the tail instruction in the SQ. */ int storeTail; /// @todo Consider moving to a more advanced model with write vs read ports /** The number of cache ports available each cycle. */ int cachePorts; /** The number of used cache ports in this cycle. */ int usedPorts; //list mshrSeqNums; //Stats::Scalar<> dcacheStallCycles; Counter lastDcacheStall; /** Wire to read information from the issue stage time queue. */ typename TimeBuffer::wire fromIssue; // Make these per thread? /** Whether or not the LSQ is stalled. */ bool stalled; /** The store that causes the stall due to partial store to load * forwarding. */ InstSeqNum stallingStoreIsn; /** The index of the above store. */ int stallingLoadIdx; /** Whether or not a load is blocked due to the memory system. It is * cleared when this value is checked via loadBlocked(). */ bool isLoadBlocked; bool loadBlockedHandled; InstSeqNum blockedLoadSeqNum; /** The oldest faulting load instruction. */ DynInstPtr loadFaultInst; /** The oldest faulting store instruction. */ DynInstPtr storeFaultInst; /** The oldest load that caused a memory ordering violation. */ DynInstPtr memDepViolator; // Will also need how many read/write ports the Dcache has. Or keep track // of that in stage that is one level up, and only call executeLoad/Store // the appropriate number of times. public: /** Executes the load at the given index. */ template Fault read(MemReqPtr &req, T &data, int load_idx); /** Executes the store at the given index. */ template Fault write(MemReqPtr &req, T &data, int store_idx); /** Returns the index of the head load instruction. */ int getLoadHead() { return loadHead; } /** Returns the sequence number of the head load instruction. */ InstSeqNum getLoadHeadSeqNum() { if (loadQueue[loadHead]) { return loadQueue[loadHead]->seqNum; } else { return 0; } } /** Returns the index of the head store instruction. */ int getStoreHead() { return storeHead; } /** Returns the sequence number of the head store instruction. */ InstSeqNum getStoreHeadSeqNum() { if (storeQueue[storeHead].inst) { return storeQueue[storeHead].inst->seqNum; } else { return 0; } } /** Returns whether or not the LSQ unit is stalled. */ bool isStalled() { return stalled; } }; template template Fault LSQUnit::read(MemReqPtr &req, T &data, int load_idx) { //Depending on issue2execute delay a squashed load could //execute if it is found to be squashed in the same //cycle it is scheduled to execute assert(loadQueue[load_idx]); if (loadQueue[load_idx]->isExecuted()) { panic("Should not reach this point with split ops!"); memcpy(&data,req->data,req->size); return NoFault; } // Make sure this isn't an uncacheable access // A bit of a hackish way to get uncached accesses to work only if they're // at the head of the LSQ and are ready to commit (at the head of the ROB // too). // @todo: Fix uncached accesses. if (req->flags & UNCACHEABLE && (load_idx != loadHead || !loadQueue[load_idx]->reachedCommit)) { iewStage->rescheduleMemInst(loadQueue[load_idx]); return TheISA::genMachineCheckFault(); } // Check the SQ for any previous stores that might lead to forwarding int store_idx = loadQueue[load_idx]->sqIdx; int store_size = 0; DPRINTF(LSQUnit, "Read called, load idx: %i, store idx: %i, " "storeHead: %i addr: %#x\n", load_idx, store_idx, storeHead, req->paddr); #ifdef FULL_SYSTEM if (req->flags & LOCKED) { cpu->lockAddr = req->paddr; cpu->lockFlag = true; } #endif while (store_idx != -1) { // End once we've reached the top of the LSQ if (store_idx == storeWBIdx) { break; } // Move the index to one younger if (--store_idx < 0) store_idx += SQEntries; assert(storeQueue[store_idx].inst); store_size = storeQueue[store_idx].size; if (store_size == 0) continue; // Check if the store data is within the lower and upper bounds of // addresses that the request needs. bool store_has_lower_limit = req->vaddr >= storeQueue[store_idx].inst->effAddr; bool store_has_upper_limit = (req->vaddr + req->size) <= (storeQueue[store_idx].inst->effAddr + store_size); bool lower_load_has_store_part = req->vaddr < (storeQueue[store_idx].inst->effAddr + store_size); bool upper_load_has_store_part = (req->vaddr + req->size) > storeQueue[store_idx].inst->effAddr; // If the store's data has all of the data needed, we can forward. if (store_has_lower_limit && store_has_upper_limit) { int shift_amt = req->vaddr & (store_size - 1); // Assumes byte addressing shift_amt = shift_amt << 3; // Cast this to type T? data = storeQueue[store_idx].data >> shift_amt; req->cmd = Read; assert(!req->completionEvent); req->completionEvent = NULL; req->time = curTick; assert(!req->data); req->data = new uint8_t[64]; memcpy(req->data, &data, req->size); DPRINTF(LSQUnit, "Forwarding from store idx %i to load to " "addr %#x, data %#x\n", store_idx, req->vaddr, *(req->data)); typename IEW::LdWritebackEvent *wb = new typename IEW::LdWritebackEvent(loadQueue[load_idx], iewStage); // We'll say this has a 1 cycle load-store forwarding latency // for now. // @todo: Need to make this a parameter. wb->schedule(curTick); // Should keep track of stat for forwarded data return NoFault; } else if ((store_has_lower_limit && lower_load_has_store_part) || (store_has_upper_limit && upper_load_has_store_part) || (lower_load_has_store_part && upper_load_has_store_part)) { // This is the partial store-load forwarding case where a store // has only part of the load's data. // If it's already been written back, then don't worry about // stalling on it. if (storeQueue[store_idx].completed) { continue; } // Must stall load and force it to retry, so long as it's the oldest // load that needs to do so. if (!stalled || (stalled && loadQueue[load_idx]->seqNum < loadQueue[stallingLoadIdx]->seqNum)) { stalled = true; stallingStoreIsn = storeQueue[store_idx].inst->seqNum; stallingLoadIdx = load_idx; } // Tell IQ/mem dep unit that this instruction will need to be // rescheduled eventually iewStage->rescheduleMemInst(loadQueue[load_idx]); // Do not generate a writeback event as this instruction is not // complete. DPRINTF(LSQUnit, "Load-store forwarding mis-match. " "Store idx %i to load addr %#x\n", store_idx, req->vaddr); return NoFault; } } // If there's no forwarding case, then go access memory DynInstPtr inst = loadQueue[load_idx]; DPRINTF(LSQUnit, "Doing functional access for inst PC %#x\n", loadQueue[load_idx]->readPC()); assert(!req->data); req->cmd = Read; req->completionEvent = NULL; req->time = curTick; req->data = new uint8_t[64]; Fault fault = cpu->read(req, data); memcpy(req->data, &data, sizeof(T)); ++usedPorts; // if we have a cache, do cache access too if (fault == NoFault && dcacheInterface) { if (dcacheInterface->isBlocked()) { // There's an older load that's already going to squash. if (isLoadBlocked && blockedLoadSeqNum < inst->seqNum) return NoFault; isLoadBlocked = true; loadBlockedHandled = false; blockedLoadSeqNum = inst->seqNum; // No fault occurred, even though the interface is blocked. return NoFault; } DPRINTF(LSQUnit, "Doing timing access for inst PC %#x\n", loadQueue[load_idx]->readPC()); assert(!req->completionEvent); req->completionEvent = new typename IEW::LdWritebackEvent(loadQueue[load_idx], iewStage); MemAccessResult result = dcacheInterface->access(req); assert(dcacheInterface->doEvents()); // Ugly hack to get an event scheduled *only* if the access is // a miss. We really should add first-class support for this // at some point. if (result != MA_HIT) { DPRINTF(LSQUnit, "LSQUnit: D-cache miss!\n"); DPRINTF(Activity, "Activity: ld accessing mem miss [sn:%lli]\n", inst->seqNum); lastDcacheStall = curTick; _status = DcacheMissStall; } else { DPRINTF(Activity, "Activity: ld accessing mem hit [sn:%lli]\n", inst->seqNum); DPRINTF(LSQUnit, "LSQUnit: D-cache hit!\n"); } } #if 0 // if we have a cache, do cache access too if (dcacheInterface) { if (dcacheInterface->isBlocked()) { isLoadBlocked = true; // No fault occurred, even though the interface is blocked. return NoFault; } DPRINTF(LSQUnit, "LSQUnit: D-cache: PC:%#x reading from paddr:%#x " "vaddr:%#x flags:%i\n", inst->readPC(), req->paddr, req->vaddr, req->flags); // Setup MemReq pointer req->cmd = Read; req->completionEvent = NULL; req->time = curTick; assert(!req->data); req->data = new uint8_t[64]; assert(!req->completionEvent); req->completionEvent = new typename IEW::LdWritebackEvent(loadQueue[load_idx], iewStage); // Do Cache Access MemAccessResult result = dcacheInterface->access(req); // Ugly hack to get an event scheduled *only* if the access is // a miss. We really should add first-class support for this // at some point. // @todo: Probably should support having no events if (result != MA_HIT) { DPRINTF(LSQUnit, "LSQUnit: D-cache miss!\n"); DPRINTF(Activity, "Activity: ld accessing mem miss [sn:%lli]\n", inst->seqNum); lastDcacheStall = curTick; _status = DcacheMissStall; } else { DPRINTF(Activity, "Activity: ld accessing mem hit [sn:%lli]\n", inst->seqNum); DPRINTF(LSQUnit, "LSQUnit: D-cache hit!\n"); } } else { fatal("Must use D-cache with new memory system"); } #endif return fault; } template template Fault LSQUnit::write(MemReqPtr &req, T &data, int store_idx) { assert(storeQueue[store_idx].inst); DPRINTF(LSQUnit, "Doing write to store idx %i, addr %#x data %#x" " | storeHead:%i [sn:%i]\n", store_idx, req->paddr, data, storeHead, storeQueue[store_idx].inst->seqNum); /* if (req->flags & LOCKED) { if (req->flags & UNCACHEABLE) { req->result = 2; } else { req->result = 1; } } */ storeQueue[store_idx].req = req; storeQueue[store_idx].size = sizeof(T); storeQueue[store_idx].data = data; // This function only writes the data to the store queue, so no fault // can happen here. return NoFault; } #endif // __CPU_O3_LSQ_UNIT_HH__