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
11 * documentation and/or other materials provided with the distribution;
12 * neither the name of the copyright holders nor the names of its
13 * contributors may be used to endorse or promote products derived from
14 * this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
17 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
18 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
19 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
20 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
21 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
22 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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_DECODE_HH__
32#define __CPU_O3_DECODE_HH__
33
34#include <queue>
35
36#include "base/statistics.hh"
37#include "base/timebuf.hh"
38
39/**
40 * DefaultDecode class handles both single threaded and SMT
41 * decode. Its width is specified by the parameters; each cycles it
42 * tries to decode that many instructions. Because instructions are
43 * actually decoded when the StaticInst is created, this stage does
44 * not do much other than check any PC-relative branches.
45 */
46template<class Impl>
47class DefaultDecode
48{
49 private:
50 // Typedefs from the Impl.
51 typedef typename Impl::O3CPU O3CPU;
52 typedef typename Impl::DynInstPtr DynInstPtr;
53 typedef typename Impl::Params Params;
54 typedef typename Impl::CPUPol CPUPol;
55
56 // Typedefs from the CPU policy.
57 typedef typename CPUPol::FetchStruct FetchStruct;
58 typedef typename CPUPol::DecodeStruct DecodeStruct;
59 typedef typename CPUPol::TimeStruct TimeStruct;
60
61 public:
62 /** Overall decode stage status. Used to determine if the CPU can
63 * deschedule itself due to a lack of activity.
64 */
65 enum DecodeStatus {
66 Active,
67 Inactive
68 };
69
70 /** Individual thread status. */
71 enum ThreadStatus {
72 Running,
73 Idle,
74 StartSquash,
75 Squashing,
76 Blocked,
77 Unblocking
78 };
79
80 private:
81 /** Decode status. */
82 DecodeStatus _status;
83
84 /** Per-thread status. */
85 ThreadStatus decodeStatus[Impl::MaxThreads];
86
87 public:
88 /** DefaultDecode constructor. */
89 DefaultDecode(Params *params);
90
91 /** Returns the name of decode. */
92 std::string name() const;
93
94 /** Registers statistics. */
95 void regStats();
96
97 /** Sets CPU pointer. */
98 void setCPU(O3CPU *cpu_ptr);
99
100 /** Sets the main backwards communication time buffer pointer. */
101 void setTimeBuffer(TimeBuffer<TimeStruct> *tb_ptr);
102
103 /** Sets pointer to time buffer used to communicate to the next stage. */
104 void setDecodeQueue(TimeBuffer<DecodeStruct> *dq_ptr);
105
106 /** Sets pointer to time buffer coming from fetch. */
107 void setFetchQueue(TimeBuffer<FetchStruct> *fq_ptr);
108
109 /** Sets pointer to list of active threads. */
110 void setActiveThreads(std::list<unsigned> *at_ptr);
111
| 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
11 * documentation and/or other materials provided with the distribution;
12 * neither the name of the copyright holders nor the names of its
13 * contributors may be used to endorse or promote products derived from
14 * this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
17 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
18 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
19 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
20 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
21 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
22 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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_DECODE_HH__
32#define __CPU_O3_DECODE_HH__
33
34#include <queue>
35
36#include "base/statistics.hh"
37#include "base/timebuf.hh"
38
39/**
40 * DefaultDecode class handles both single threaded and SMT
41 * decode. Its width is specified by the parameters; each cycles it
42 * tries to decode that many instructions. Because instructions are
43 * actually decoded when the StaticInst is created, this stage does
44 * not do much other than check any PC-relative branches.
45 */
46template<class Impl>
47class DefaultDecode
48{
49 private:
50 // Typedefs from the Impl.
51 typedef typename Impl::O3CPU O3CPU;
52 typedef typename Impl::DynInstPtr DynInstPtr;
53 typedef typename Impl::Params Params;
54 typedef typename Impl::CPUPol CPUPol;
55
56 // Typedefs from the CPU policy.
57 typedef typename CPUPol::FetchStruct FetchStruct;
58 typedef typename CPUPol::DecodeStruct DecodeStruct;
59 typedef typename CPUPol::TimeStruct TimeStruct;
60
61 public:
62 /** Overall decode stage status. Used to determine if the CPU can
63 * deschedule itself due to a lack of activity.
64 */
65 enum DecodeStatus {
66 Active,
67 Inactive
68 };
69
70 /** Individual thread status. */
71 enum ThreadStatus {
72 Running,
73 Idle,
74 StartSquash,
75 Squashing,
76 Blocked,
77 Unblocking
78 };
79
80 private:
81 /** Decode status. */
82 DecodeStatus _status;
83
84 /** Per-thread status. */
85 ThreadStatus decodeStatus[Impl::MaxThreads];
86
87 public:
88 /** DefaultDecode constructor. */
89 DefaultDecode(Params *params);
90
91 /** Returns the name of decode. */
92 std::string name() const;
93
94 /** Registers statistics. */
95 void regStats();
96
97 /** Sets CPU pointer. */
98 void setCPU(O3CPU *cpu_ptr);
99
100 /** Sets the main backwards communication time buffer pointer. */
101 void setTimeBuffer(TimeBuffer<TimeStruct> *tb_ptr);
102
103 /** Sets pointer to time buffer used to communicate to the next stage. */
104 void setDecodeQueue(TimeBuffer<DecodeStruct> *dq_ptr);
105
106 /** Sets pointer to time buffer coming from fetch. */
107 void setFetchQueue(TimeBuffer<FetchStruct> *fq_ptr);
108
109 /** Sets pointer to list of active threads. */
110 void setActiveThreads(std::list<unsigned> *at_ptr);
111
|
114
115 /** Takes over from another CPU's thread. */
116 void takeOverFrom();
117
118 /** Ticks decode, processing all input signals and decoding as many
119 * instructions as possible.
120 */
121 void tick();
122
123 /** Determines what to do based on decode's current status.
124 * @param status_change decode() sets this variable if there was a status
125 * change (ie switching from from blocking to unblocking).
126 * @param tid Thread id to decode instructions from.
127 */
128 void decode(bool &status_change, unsigned tid);
129
130 /** Processes instructions from fetch and passes them on to rename.
131 * Decoding of instructions actually happens when they are created in
132 * fetch, so this function mostly checks if PC-relative branches are
133 * correct.
134 */
135 void decodeInsts(unsigned tid);
136
137 private:
138 /** Inserts a thread's instructions into the skid buffer, to be decoded
139 * once decode unblocks.
140 */
141 void skidInsert(unsigned tid);
142
143 /** Returns if all of the skid buffers are empty. */
144 bool skidsEmpty();
145
146 /** Updates overall decode status based on all of the threads' statuses. */
147 void updateStatus();
148
149 /** Separates instructions from fetch into individual lists of instructions
150 * sorted by thread.
151 */
152 void sortInsts();
153
154 /** Reads all stall signals from the backwards communication timebuffer. */
155 void readStallSignals(unsigned tid);
156
157 /** Checks all input signals and updates decode's status appropriately. */
158 bool checkSignalsAndUpdate(unsigned tid);
159
160 /** Checks all stall signals, and returns if any are true. */
161 bool checkStall(unsigned tid) const;
162
163 /** Returns if there any instructions from fetch on this cycle. */
164 inline bool fetchInstsValid();
165
166 /** Switches decode to blocking, and signals back that decode has
167 * become blocked.
168 * @return Returns true if there is a status change.
169 */
170 bool block(unsigned tid);
171
172 /** Switches decode to unblocking if the skid buffer is empty, and
173 * signals back that decode has unblocked.
174 * @return Returns true if there is a status change.
175 */
176 bool unblock(unsigned tid);
177
178 /** Squashes if there is a PC-relative branch that was predicted
179 * incorrectly. Sends squash information back to fetch.
180 */
181 void squash(DynInstPtr &inst, unsigned tid);
182
183 public:
184 /** Squashes due to commit signalling a squash. Changes status to
185 * squashing and clears block/unblock signals as needed.
186 */
187 unsigned squash(unsigned tid);
188
189 private:
190 // Interfaces to objects outside of decode.
191 /** CPU interface. */
192 O3CPU *cpu;
193
194 /** Time buffer interface. */
195 TimeBuffer<TimeStruct> *timeBuffer;
196
197 /** Wire to get rename's output from backwards time buffer. */
198 typename TimeBuffer<TimeStruct>::wire fromRename;
199
200 /** Wire to get iew's information from backwards time buffer. */
201 typename TimeBuffer<TimeStruct>::wire fromIEW;
202
203 /** Wire to get commit's information from backwards time buffer. */
204 typename TimeBuffer<TimeStruct>::wire fromCommit;
205
206 /** Wire to write information heading to previous stages. */
207 // Might not be the best name as not only fetch will read it.
208 typename TimeBuffer<TimeStruct>::wire toFetch;
209
210 /** Decode instruction queue. */
211 TimeBuffer<DecodeStruct> *decodeQueue;
212
213 /** Wire used to write any information heading to rename. */
214 typename TimeBuffer<DecodeStruct>::wire toRename;
215
216 /** Fetch instruction queue interface. */
217 TimeBuffer<FetchStruct> *fetchQueue;
218
219 /** Wire to get fetch's output from fetch queue. */
220 typename TimeBuffer<FetchStruct>::wire fromFetch;
221
222 /** Queue of all instructions coming from fetch this cycle. */
223 std::queue<DynInstPtr> insts[Impl::MaxThreads];
224
225 /** Skid buffer between fetch and decode. */
226 std::queue<DynInstPtr> skidBuffer[Impl::MaxThreads];
227
228 /** Variable that tracks if decode has written to the time buffer this
229 * cycle. Used to tell CPU if there is activity this cycle.
230 */
231 bool wroteToTimeBuffer;
232
233 /** Source of possible stalls. */
234 struct Stalls {
235 bool rename;
236 bool iew;
237 bool commit;
238 };
239
240 /** Tracks which stages are telling decode to stall. */
241 Stalls stalls[Impl::MaxThreads];
242
243 /** Rename to decode delay, in ticks. */
244 unsigned renameToDecodeDelay;
245
246 /** IEW to decode delay, in ticks. */
247 unsigned iewToDecodeDelay;
248
249 /** Commit to decode delay, in ticks. */
250 unsigned commitToDecodeDelay;
251
252 /** Fetch to decode delay, in ticks. */
253 unsigned fetchToDecodeDelay;
254
255 /** The width of decode, in instructions. */
256 unsigned decodeWidth;
257
258 /** Index of instructions being sent to rename. */
259 unsigned toRenameIndex;
260
261 /** number of Active Threads*/
262 unsigned numThreads;
263
264 /** List of active thread ids */
265 std::list<unsigned> *activeThreads;
266
267 /** Number of branches in flight. */
268 unsigned branchCount[Impl::MaxThreads];
269
270 /** Maximum size of the skid buffer. */
271 unsigned skidBufferMax;
272
273 /** Stat for total number of idle cycles. */
274 Stats::Scalar<> decodeIdleCycles;
275 /** Stat for total number of blocked cycles. */
276 Stats::Scalar<> decodeBlockedCycles;
277 /** Stat for total number of normal running cycles. */
278 Stats::Scalar<> decodeRunCycles;
279 /** Stat for total number of unblocking cycles. */
280 Stats::Scalar<> decodeUnblockCycles;
281 /** Stat for total number of squashing cycles. */
282 Stats::Scalar<> decodeSquashCycles;
283 /** Stat for number of times a branch is resolved at decode. */
284 Stats::Scalar<> decodeBranchResolved;
285 /** Stat for number of times a branch mispredict is detected. */
286 Stats::Scalar<> decodeBranchMispred;
287 /** Stat for number of times decode detected a non-control instruction
288 * incorrectly predicted as a branch.
289 */
290 Stats::Scalar<> decodeControlMispred;
291 /** Stat for total number of decoded instructions. */
292 Stats::Scalar<> decodeDecodedInsts;
293 /** Stat for total number of squashed instructions. */
294 Stats::Scalar<> decodeSquashedInsts;
295};
296
297#endif // __CPU_O3_DECODE_HH__
| 120
121 /** Takes over from another CPU's thread. */
122 void takeOverFrom();
123
124 /** Ticks decode, processing all input signals and decoding as many
125 * instructions as possible.
126 */
127 void tick();
128
129 /** Determines what to do based on decode's current status.
130 * @param status_change decode() sets this variable if there was a status
131 * change (ie switching from from blocking to unblocking).
132 * @param tid Thread id to decode instructions from.
133 */
134 void decode(bool &status_change, unsigned tid);
135
136 /** Processes instructions from fetch and passes them on to rename.
137 * Decoding of instructions actually happens when they are created in
138 * fetch, so this function mostly checks if PC-relative branches are
139 * correct.
140 */
141 void decodeInsts(unsigned tid);
142
143 private:
144 /** Inserts a thread's instructions into the skid buffer, to be decoded
145 * once decode unblocks.
146 */
147 void skidInsert(unsigned tid);
148
149 /** Returns if all of the skid buffers are empty. */
150 bool skidsEmpty();
151
152 /** Updates overall decode status based on all of the threads' statuses. */
153 void updateStatus();
154
155 /** Separates instructions from fetch into individual lists of instructions
156 * sorted by thread.
157 */
158 void sortInsts();
159
160 /** Reads all stall signals from the backwards communication timebuffer. */
161 void readStallSignals(unsigned tid);
162
163 /** Checks all input signals and updates decode's status appropriately. */
164 bool checkSignalsAndUpdate(unsigned tid);
165
166 /** Checks all stall signals, and returns if any are true. */
167 bool checkStall(unsigned tid) const;
168
169 /** Returns if there any instructions from fetch on this cycle. */
170 inline bool fetchInstsValid();
171
172 /** Switches decode to blocking, and signals back that decode has
173 * become blocked.
174 * @return Returns true if there is a status change.
175 */
176 bool block(unsigned tid);
177
178 /** Switches decode to unblocking if the skid buffer is empty, and
179 * signals back that decode has unblocked.
180 * @return Returns true if there is a status change.
181 */
182 bool unblock(unsigned tid);
183
184 /** Squashes if there is a PC-relative branch that was predicted
185 * incorrectly. Sends squash information back to fetch.
186 */
187 void squash(DynInstPtr &inst, unsigned tid);
188
189 public:
190 /** Squashes due to commit signalling a squash. Changes status to
191 * squashing and clears block/unblock signals as needed.
192 */
193 unsigned squash(unsigned tid);
194
195 private:
196 // Interfaces to objects outside of decode.
197 /** CPU interface. */
198 O3CPU *cpu;
199
200 /** Time buffer interface. */
201 TimeBuffer<TimeStruct> *timeBuffer;
202
203 /** Wire to get rename's output from backwards time buffer. */
204 typename TimeBuffer<TimeStruct>::wire fromRename;
205
206 /** Wire to get iew's information from backwards time buffer. */
207 typename TimeBuffer<TimeStruct>::wire fromIEW;
208
209 /** Wire to get commit's information from backwards time buffer. */
210 typename TimeBuffer<TimeStruct>::wire fromCommit;
211
212 /** Wire to write information heading to previous stages. */
213 // Might not be the best name as not only fetch will read it.
214 typename TimeBuffer<TimeStruct>::wire toFetch;
215
216 /** Decode instruction queue. */
217 TimeBuffer<DecodeStruct> *decodeQueue;
218
219 /** Wire used to write any information heading to rename. */
220 typename TimeBuffer<DecodeStruct>::wire toRename;
221
222 /** Fetch instruction queue interface. */
223 TimeBuffer<FetchStruct> *fetchQueue;
224
225 /** Wire to get fetch's output from fetch queue. */
226 typename TimeBuffer<FetchStruct>::wire fromFetch;
227
228 /** Queue of all instructions coming from fetch this cycle. */
229 std::queue<DynInstPtr> insts[Impl::MaxThreads];
230
231 /** Skid buffer between fetch and decode. */
232 std::queue<DynInstPtr> skidBuffer[Impl::MaxThreads];
233
234 /** Variable that tracks if decode has written to the time buffer this
235 * cycle. Used to tell CPU if there is activity this cycle.
236 */
237 bool wroteToTimeBuffer;
238
239 /** Source of possible stalls. */
240 struct Stalls {
241 bool rename;
242 bool iew;
243 bool commit;
244 };
245
246 /** Tracks which stages are telling decode to stall. */
247 Stalls stalls[Impl::MaxThreads];
248
249 /** Rename to decode delay, in ticks. */
250 unsigned renameToDecodeDelay;
251
252 /** IEW to decode delay, in ticks. */
253 unsigned iewToDecodeDelay;
254
255 /** Commit to decode delay, in ticks. */
256 unsigned commitToDecodeDelay;
257
258 /** Fetch to decode delay, in ticks. */
259 unsigned fetchToDecodeDelay;
260
261 /** The width of decode, in instructions. */
262 unsigned decodeWidth;
263
264 /** Index of instructions being sent to rename. */
265 unsigned toRenameIndex;
266
267 /** number of Active Threads*/
268 unsigned numThreads;
269
270 /** List of active thread ids */
271 std::list<unsigned> *activeThreads;
272
273 /** Number of branches in flight. */
274 unsigned branchCount[Impl::MaxThreads];
275
276 /** Maximum size of the skid buffer. */
277 unsigned skidBufferMax;
278
279 /** Stat for total number of idle cycles. */
280 Stats::Scalar<> decodeIdleCycles;
281 /** Stat for total number of blocked cycles. */
282 Stats::Scalar<> decodeBlockedCycles;
283 /** Stat for total number of normal running cycles. */
284 Stats::Scalar<> decodeRunCycles;
285 /** Stat for total number of unblocking cycles. */
286 Stats::Scalar<> decodeUnblockCycles;
287 /** Stat for total number of squashing cycles. */
288 Stats::Scalar<> decodeSquashCycles;
289 /** Stat for number of times a branch is resolved at decode. */
290 Stats::Scalar<> decodeBranchResolved;
291 /** Stat for number of times a branch mispredict is detected. */
292 Stats::Scalar<> decodeBranchMispred;
293 /** Stat for number of times decode detected a non-control instruction
294 * incorrectly predicted as a branch.
295 */
296 Stats::Scalar<> decodeControlMispred;
297 /** Stat for total number of decoded instructions. */
298 Stats::Scalar<> decodeDecodedInsts;
299 /** Stat for total number of squashed instructions. */
300 Stats::Scalar<> decodeSquashedInsts;
301};
302
303#endif // __CPU_O3_DECODE_HH__
|