/*
* 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
*/
#ifndef __CPU_OZONE_LSQ_UNIT_HH__
#define __CPU_OZONE_LSQ_UNIT_HH__
#include <algorithm>
#include <map>
#include <queue>
#include "arch/types.hh"
#include "base/hashmap.hh"
#include "config/the_isa.hh"
#include "cpu/inst_seq.hh"
#include "mem/mem_interface.hh"
//#include "mem/page_table.hh"
#include "sim/fault_fwd.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() const;
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; }
/** 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->isUncacheable() &&
(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__