1/*
2 * Copyright (c) 2004-2006 The Regents of The University of Michigan
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are
7 * met: redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer;
9 * redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the

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23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
26 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 *
28 * Authors: Kevin Lim
29 */
30
31#ifndef __CPU_O3_MEM_DEP_UNIT_HH__
32#define __CPU_O3_MEM_DEP_UNIT_HH__
33
34#include <list>
35#include <set>
36
37#include "base/hashmap.hh"
38#include "base/refcnt.hh"
39#include "base/statistics.hh"
40#include "cpu/inst_seq.hh"
41
42struct SNHash {
43 size_t operator() (const InstSeqNum &seq_num) const {
44 unsigned a = (unsigned)seq_num;
45 unsigned hash = (((a >> 14) ^ ((a >> 2) & 0xffff))) & 0x7FFFFFFF;
46
47 return hash;
48 }
49};
50
51template <class Impl>
52class InstructionQueue;
53
54/**
55 * Memory dependency unit class. This holds the memory dependence predictor.
56 * As memory operations are issued to the IQ, they are also issued to this
57 * unit, which then looks up the prediction as to what they are dependent
58 * upon. This unit must be checked prior to a memory operation being able
59 * to issue. Although this is templated, it's somewhat hard to make a generic
60 * memory dependence unit. This one is mostly for store sets; it will be
61 * quite limited in what other memory dependence predictions it can also
62 * utilize. Thus this class should be most likely be rewritten for other
63 * dependence prediction schemes.
64 */
65template <class MemDepPred, class Impl>
66class MemDepUnit {
67 public:
68 typedef typename Impl::Params Params;
69 typedef typename Impl::DynInstPtr DynInstPtr;
70
71 /** Empty constructor. Must call init() prior to using in this case. */
72 MemDepUnit() {}
73
74 /** Constructs a MemDepUnit with given parameters. */
75 MemDepUnit(Params *params);
76
77 /** Frees up any memory allocated. */
78 ~MemDepUnit();
79
80 /** Returns the name of the memory dependence unit. */
81 std::string name() const;
82
83 /** Initializes the unit with parameters and a thread id. */
84 void init(Params *params, int tid);
85
86 /** Registers statistics. */
87 void regStats();
88
89 void switchOut();
90
91 void takeOverFrom();
92
93 /** Sets the pointer to the IQ. */
94 void setIQ(InstructionQueue<Impl> *iq_ptr);
95
96 /** Inserts a memory instruction. */
97 void insert(DynInstPtr &inst);
98
99 /** Inserts a non-speculative memory instruction. */
100 void insertNonSpec(DynInstPtr &inst);
101
102 /** Inserts a barrier instruction. */
103 void insertBarrier(DynInstPtr &barr_inst);
104
105 /** Indicate that an instruction has its registers ready. */
106 void regsReady(DynInstPtr &inst);
107
108 /** Indicate that a non-speculative instruction is ready. */
109 void nonSpecInstReady(DynInstPtr &inst);
110
111 /** Reschedules an instruction to be re-executed. */
112 void reschedule(DynInstPtr &inst);
113
114 /** Replays all instructions that have been rescheduled by moving them to
115 * the ready list.
116 */
117 void replay(DynInstPtr &inst);
118
119 /** Completes a memory instruction. */
120 void completed(DynInstPtr &inst);
121
122 /** Completes a barrier instruction. */
123 void completeBarrier(DynInstPtr &inst);
124
125 /** Wakes any dependents of a memory instruction. */
126 void wakeDependents(DynInstPtr &inst);
127
128 /** Squashes all instructions up until a given sequence number for a
129 * specific thread.
130 */
131 void squash(const InstSeqNum &squashed_num, unsigned tid);
132
133 /** Indicates an ordering violation between a store and a younger load. */
134 void violation(DynInstPtr &store_inst, DynInstPtr &violating_load);
135
136 /** Issues the given instruction */
137 void issue(DynInstPtr &inst);
138
139 /** Debugging function to dump the lists of instructions. */
140 void dumpLists();
141
142 private:
143 typedef typename std::list<DynInstPtr>::iterator ListIt;
144
145 class MemDepEntry;
146
147 typedef RefCountingPtr<MemDepEntry> MemDepEntryPtr;
148
149 /** Memory dependence entries that track memory operations, marking
150 * when the instruction is ready to execute and what instructions depend
151 * upon it.
152 */
153 class MemDepEntry : public RefCounted {
154 public:
155 /** Constructs a memory dependence entry. */
156 MemDepEntry(DynInstPtr &new_inst)
157 : inst(new_inst), regsReady(false), memDepReady(false),
158 completed(false), squashed(false)
159 {
160 ++memdep_count;
161
162 DPRINTF(MemDepUnit, "Memory dependency entry created. "
163 "memdep_count=%i\n", memdep_count);
164 }
165
166 /** Frees any pointers. */
167 ~MemDepEntry()
168 {
169 for (int i = 0; i < dependInsts.size(); ++i) {
170 dependInsts[i] = NULL;
171 }
172
173 --memdep_count;
174
175 DPRINTF(MemDepUnit, "Memory dependency entry deleted. "
176 "memdep_count=%i\n", memdep_count);
177 }
178
179 /** Returns the name of the memory dependence entry. */
180 std::string name() const { return "memdepentry"; }
181
182 /** The instruction being tracked. */
183 DynInstPtr inst;
184
185 /** The iterator to the instruction's location inside the list. */
186 ListIt listIt;
187
188 /** A vector of any dependent instructions. */
189 std::vector<MemDepEntryPtr> dependInsts;
190
191 /** If the registers are ready or not. */
192 bool regsReady;
193 /** If all memory dependencies have been satisfied. */
194 bool memDepReady;
195 /** If the instruction is completed. */
196 bool completed;
197 /** If the instruction is squashed. */
198 bool squashed;
199
200 /** For debugging. */
201 static int memdep_count;
202 static int memdep_insert;
203 static int memdep_erase;
204 };
205
206 /** Finds the memory dependence entry in the hash map. */
207 inline MemDepEntryPtr &findInHash(const DynInstPtr &inst);
208
209 /** Moves an entry to the ready list. */
210 inline void moveToReady(MemDepEntryPtr &ready_inst_entry);
211
212 typedef m5::hash_map<InstSeqNum, MemDepEntryPtr, SNHash> MemDepHash;
213
214 typedef typename MemDepHash::iterator MemDepHashIt;
215
216 /** A hash map of all memory dependence entries. */
217 MemDepHash memDepHash;
218
219 /** A list of all instructions in the memory dependence unit. */
220 std::list<DynInstPtr> instList[Impl::MaxThreads];
221
222 /** A list of all instructions that are going to be replayed. */
223 std::list<DynInstPtr> instsToReplay;
224
225 /** The memory dependence predictor. It is accessed upon new
226 * instructions being added to the IQ, and responds by telling
227 * this unit what instruction the newly added instruction is dependent
228 * upon.
229 */
230 MemDepPred depPred;
231
232 bool loadBarrier;
233 InstSeqNum loadBarrierSN;
234 bool storeBarrier;
235 InstSeqNum storeBarrierSN;
236
237 /** Pointer to the IQ. */
238 InstructionQueue<Impl> *iqPtr;
239
240 /** The thread id of this memory dependence unit. */
241 int id;
242
243 /** Stat for number of inserted loads. */
244 Stats::Scalar<> insertedLoads;
245 /** Stat for number of inserted stores. */
246 Stats::Scalar<> insertedStores;
247 /** Stat for number of conflicting loads that had to wait for a store. */
248 Stats::Scalar<> conflictingLoads;
249 /** Stat for number of conflicting stores that had to wait for a store. */
250 Stats::Scalar<> conflictingStores;
251};
252
253#endif // __CPU_O3_MEM_DEP_UNIT_HH__