1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
|
/*
* 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_OZONE_LW_LSQ_HH__
#define __CPU_OZONE_LW_LSQ_HH__
#include <list>
#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/debug.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 OzoneLWLSQ {
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(DynInstPtr &inst, BackEnd *be,
Event *wb_event, OzoneLWLSQ *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. */
DynInstPtr inst;
BackEnd *be;
/** The writeback event for the store. Needed for store
* conditionals.
*/
public:
Event *wbEvent;
bool miss;
private:
/** The pointer to the LSQ unit that issued the store. */
OzoneLWLSQ<Impl> *lsqPtr;
};
public:
/** Constructs an LSQ unit. init() must be called prior to use. */
OzoneLWLSQ();
/** 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);
/** Executes a store instruction. */
Fault executeStore(DynInstPtr &inst);
/** Commits the head load. */
void commitLoad();
/** 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.back().canWB &&
!storeQueue.back().completed &&
!dcacheInterface->isBlocked(); }
void switchOut();
void takeOverFrom(ExecContext *old_xc = NULL);
bool isSwitchedOut() { return switchedOut; }
bool switchedOut;
private:
/** Completes the store at the specified index. */
void completeStore(int store_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), lqIt(NULL)
{ }
/** 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), lqIt(NULL)
{ }
/** 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;
typename std::list<DynInstPtr>::iterator lqIt;
};
enum Status {
Running,
Idle,
DcacheMissStall,
DcacheMissSwitch
};
private:
/** The OzoneLWLSQ thread id. */
unsigned lsqID;
/** The status of the LSQ unit. */
Status _status;
/** The store queue. */
std::list<SQEntry> storeQueue;
/** The load queue. */
std::list<DynInstPtr> loadQueue;
typedef typename std::list<SQEntry>::iterator SQIt;
typedef typename std::list<DynInstPtr>::iterator LQIt;
struct HashFn {
size_t operator() (const int a) const
{
unsigned hash = (((a >> 14) ^ ((a >> 2) & 0xffff))) & 0x7FFFFFFF;
return hash;
}
};
m5::hash_map<int, SQIt, HashFn> SQItHash;
std::queue<int> SQIndices;
m5::hash_map<int, LQIt, HashFn> LQItHash;
std::queue<int> LQIndices;
typedef typename m5::hash_map<int, LQIt, HashFn>::iterator LQHashIt;
typedef typename m5::hash_map<int, SQIt, HashFn>::iterator SQHashIt;
// 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;
int storesToWB;
/// @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;
// 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. */
LQIt stallingLoad;
/** 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 <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 sequence number of the head load instruction. */
InstSeqNum getLoadHeadSeqNum()
{
if (!loadQueue.empty()) {
return loadQueue.back()->seqNum;
} else {
return 0;
}
}
/** Returns the sequence number of the head store instruction. */
InstSeqNum getStoreHeadSeqNum()
{
if (!storeQueue.empty()) {
return storeQueue.back().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
OzoneLWLSQ<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
typename m5::hash_map<int, LQIt, HashFn>::iterator
lq_hash_it = LQItHash.find(load_idx);
assert(lq_hash_it != LQItHash.end());
DynInstPtr inst = (*(*lq_hash_it).second);
if (inst->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 &&
(inst != loadQueue.back() || !inst->isAtCommit())) {
DPRINTF(OzoneLSQ, "[sn:%lli] Uncached load and not head of "
"commit/LSQ!\n",
inst->seqNum);
be->rescheduleMemInst(inst);
return TheISA::genMachineCheckFault();
}
// Check the SQ for any previous stores that might lead to forwarding
SQIt sq_it = storeQueue.begin();
int store_size = 0;
DPRINTF(OzoneLSQ, "Read called, load idx: %i addr: %#x\n",
load_idx, req->paddr);
while (sq_it != storeQueue.end() && (*sq_it).inst->seqNum > inst->seqNum)
++sq_it;
while (1) {
// End once we've reached the top of the LSQ
if (sq_it == storeQueue.end()) {
break;
}
assert((*sq_it).inst);
store_size = (*sq_it).size;
if (store_size == 0) {
sq_it++;
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 >= (*sq_it).inst->effAddr;
bool store_has_upper_limit =
(req->vaddr + req->size) <= ((*sq_it).inst->effAddr +
store_size);
bool lower_load_has_store_part =
req->vaddr < ((*sq_it).inst->effAddr +
store_size);
bool upper_load_has_store_part =
(req->vaddr + req->size) > (*sq_it).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 = (*sq_it).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 [sn:%lli] to load to "
"[sn:%lli] addr %#x, data %#x\n",
(*sq_it).inst->seqNum, inst->seqNum, req->vaddr, *(req->data));
typename BackEnd::LdWritebackEvent *wb =
new typename BackEnd::LdWritebackEvent(inst,
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 ((*sq_it).completed) {
sq_it++;
break;
}
// Must stall load and force it to retry, so long as it's the oldest
// load that needs to do so.
if (!stalled ||
(stalled &&
inst->seqNum <
(*stallingLoad)->seqNum)) {
stalled = true;
stallingStoreIsn = (*sq_it).inst->seqNum;
stallingLoad = (*lq_hash_it).second;
}
// Tell IQ/mem dep unit that this instruction will need to be
// rescheduled eventually
be->rescheduleMemInst(inst);
DPRINTF(OzoneLSQ, "Load-store forwarding mis-match. "
"Store [sn:%lli] to load addr %#x\n",
(*sq_it).inst->seqNum, req->vaddr);
return NoFault;
}
sq_it++;
}
// If there's no forwarding case, then go access memory
DPRINTF(OzoneLSQ, "Doing functional access for inst PC %#x\n",
inst->readPC());
// Setup MemReq pointer
req->cmd = Read;
req->completionEvent = NULL;
req->time = curTick;
assert(!req->data);
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 (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(OzoneLSQ, "D-cache: PC:%#x reading from paddr:%#x "
"vaddr:%#x flags:%i\n",
inst->readPC(), req->paddr, req->vaddr, req->flags);
assert(!req->completionEvent);
req->completionEvent =
new typename BackEnd::LdWritebackEvent(inst, be);
// 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;
} else {
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
OzoneLWLSQ<Impl>::write(MemReqPtr &req, T &data, int store_idx)
{
SQHashIt sq_hash_it = SQItHash.find(store_idx);
assert(sq_hash_it != SQItHash.end());
SQIt sq_it = (*sq_hash_it).second;
assert((*sq_it).inst);
DPRINTF(OzoneLSQ, "Doing write to store idx %i, addr %#x data %#x"
" | [sn:%lli]\n",
store_idx, req->paddr, data, (*sq_it).inst->seqNum);
(*sq_it).req = req;
(*sq_it).size = sizeof(T);
(*sq_it).data = data;
assert(!req->data);
req->data = new uint8_t[64];
memcpy(req->data, (uint8_t *)&(*sq_it).data, req->size);
// This function only writes the data to the store queue, so no fault
// can happen here.
return NoFault;
}
#endif // __CPU_OZONE_LW_LSQ_HH__
|