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Diffstat (limited to 'cpu/ozone/lsq_unit.hh')
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diff --git a/cpu/ozone/lsq_unit.hh b/cpu/ozone/lsq_unit.hh new file mode 100644 index 000000000..4b600af67 --- /dev/null +++ b/cpu/ozone/lsq_unit.hh @@ -0,0 +1,637 @@ +/* + * 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_OZONE_LSQ_UNIT_HH__ +#define __CPU_OZONE_LSQ_UNIT_HH__ + +#include <map> +#include <queue> +#include <algorithm> + +#include "arch/faults.hh" +#include "arch/isa_traits.hh" +#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" + +class PageTable; + +/** + * 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 Impl> +class OzoneLSQ { + public: + typedef typename Impl::Params Params; + typedef typename Impl::FullCPU FullCPU; + typedef typename Impl::BackEnd BackEnd; + typedef typename Impl::DynInstPtr DynInstPtr; + typedef typename Impl::IssueStruct IssueStruct; + + typedef TheISA::IntReg IntReg; + + typedef typename std::map<InstSeqNum, DynInstPtr>::iterator LdMapIt; + + private: + class StoreCompletionEvent : public Event { + public: + /** Constructs a store completion event. */ + StoreCompletionEvent(int store_idx, Event *wb_event, OzoneLSQ *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. */ + OzoneLSQ<Impl> *lsqPtr; + }; + + friend class StoreCompletionEvent; + + public: + /** Constructs an LSQ unit. init() must be called prior to use. */ + OzoneLSQ(); + + /** 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 back-end stage pointer. */ + void setBE(BackEnd *be_ptr) + { be = be_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. + */ + inline bool loadBlocked(); + + /** 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 back-end stage. */ + BackEnd *be; + + /** 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 OzoneLSQ thread id. */ + unsigned lsqID; + + /** The status of the LSQ unit. */ + Status _status; + + /** The store queue. */ + std::vector<SQEntry> storeQueue; + + /** The load queue. */ + std::vector<DynInstPtr> 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<InstSeqNum> mshrSeqNums; + + //Stats::Scalar<> dcacheStallCycles; + Counter lastDcacheStall; + + /** Wire to read information from the issue stage time queue. */ + typename TimeBuffer<IssueStruct>::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; + + /** 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 <class T> + Fault read(MemReqPtr &req, T &data, int load_idx); + + /** Executes the store at the given index. */ + template <class T> + 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 <class Impl> +template <class T> +Fault +OzoneLSQ<Impl>::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]->readyToCommit())) { + + 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(OzoneLSQ, "Read called, load idx: %i, store idx: %i, " + "storeHead: %i addr: %#x\n", + load_idx, store_idx, storeHead, req->paddr); + + 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(OzoneLSQ, "Forwarding from store idx %i to load to " + "addr %#x, data %#x\n", + store_idx, req->vaddr, *(req->data)); + + typename BackEnd::LdWritebackEvent *wb = + new typename BackEnd::LdWritebackEvent(loadQueue[load_idx], + be); + + // We'll say this has a 1 cycle load-store forwarding latency + // for now. + // FIXME - 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 + be->rescheduleMemInst(loadQueue[load_idx]); + + DPRINTF(OzoneLSQ, "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]; + + ++usedPorts; + + // 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(OzoneLSQ, "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); + typedef typename BackEnd::LdWritebackEvent LdWritebackEvent; + + LdWritebackEvent *wb = new LdWritebackEvent(loadQueue[load_idx], be); + + req->completionEvent = wb; + + // 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(OzoneLSQ, "D-cache miss!\n"); + DPRINTF(Activity, "Activity: ld accessing mem miss [sn:%lli]\n", + inst->seqNum); + + lastDcacheStall = curTick; + + _status = DcacheMissStall; + + wb->setDcacheMiss(); + + } else { +// DPRINTF(Activity, "Activity: ld accessing mem hit [sn:%lli]\n", +// inst->seqNum); + + DPRINTF(OzoneLSQ, "D-cache hit!\n"); + } + } else { + fatal("Must use D-cache with new memory system"); + } + + return NoFault; +} + +template <class Impl> +template <class T> +Fault +OzoneLSQ<Impl>::write(MemReqPtr &req, T &data, int store_idx) +{ + assert(storeQueue[store_idx].inst); + + DPRINTF(OzoneLSQ, "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); + + 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; +} + +template <class Impl> +inline bool +OzoneLSQ<Impl>::loadBlocked() +{ + bool ret_val = isLoadBlocked; + isLoadBlocked = false; + return ret_val; +} + +#endif // __CPU_OZONE_LSQ_UNIT_HH__ |