dep_graph.hh revision 2689:dbf969c18a65 
1/*
2 * Copyright (c) 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_DEP_GRAPH_HH__
32#define __CPU_O3_DEP_GRAPH_HH__
33
34#include "cpu/o3/comm.hh"
35
36/** Node in a linked list. */
37template <class DynInstPtr>
38class DependencyEntry
39{
40  public:
41    DependencyEntry()
42        : inst(NULL), next(NULL)
43    { }
44
45    DynInstPtr inst;
46    //Might want to include data about what arch. register the
47    //dependence is waiting on.
48    DependencyEntry<DynInstPtr> *next;
49};
50
51/** Array of linked list that maintains the dependencies between
52 * producing instructions and consuming instructions.  Each linked
53 * list represents a single physical register, having the future
54 * producer of the register's value, and all consumers waiting on that
55 * value on the list.  The head node of each linked list represents
56 * the producing instruction of that register.  Instructions are put
57 * on the list upon reaching the IQ, and are removed from the list
58 * either when the producer completes, or the instruction is squashed.
59*/
60template <class DynInstPtr>
61class DependencyGraph
62{
63  public:
64    typedef DependencyEntry<DynInstPtr> DepEntry;
65
66    /** Default construction.  Must call resize() prior to use. */
67    DependencyGraph()
68        : numEntries(0), memAllocCounter(0), nodesTraversed(0), nodesRemoved(0)
69    { }
70
71    /** Resize the dependency graph to have num_entries registers. */
72    void resize(int num_entries);
73
74    /** Clears all of the linked lists. */
75    void reset();
76
77    /** Inserts an instruction to be dependent on the given index. */
78    void insert(PhysRegIndex idx, DynInstPtr &new_inst);
79
80    /** Sets the producing instruction of a given register. */
81    void setInst(PhysRegIndex idx, DynInstPtr &new_inst)
82    { dependGraph[idx].inst = new_inst; }
83
84    /** Clears the producing instruction. */
85    void clearInst(PhysRegIndex idx)
86    { dependGraph[idx].inst = NULL; }
87
88    /** Removes an instruction from a single linked list. */
89    void remove(PhysRegIndex idx, DynInstPtr &inst_to_remove);
90
91    /** Removes and returns the newest dependent of a specific register. */
92    DynInstPtr pop(PhysRegIndex idx);
93
94    /** Checks if there are any dependents on a specific register. */
95    bool empty(PhysRegIndex idx) { return !dependGraph[idx].next; }
96
97    /** Debugging function to dump out the dependency graph.
98     */
99    void dump();
100
101  private:
102    /** Array of linked lists.  Each linked list is a list of all the
103     *  instructions that depend upon a given register.  The actual
104     *  register's index is used to index into the graph; ie all
105     *  instructions in flight that are dependent upon r34 will be
106     *  in the linked list of dependGraph[34].
107     */
108    DepEntry *dependGraph;
109
110    /** Number of linked lists; identical to the number of registers. */
111    int numEntries;
112
113    // Debug variable, remove when done testing.
114    unsigned memAllocCounter;
115
116  public:
117    // Debug variable, remove when done testing.
118    uint64_t nodesTraversed;
119    // Debug variable, remove when done testing.
120    uint64_t nodesRemoved;
121};
122
123template <class DynInstPtr>
124void
125DependencyGraph<DynInstPtr>::resize(int num_entries)
126{
127    numEntries = num_entries;
128    dependGraph = new DepEntry[numEntries];
129}
130
131template <class DynInstPtr>
132void
133DependencyGraph<DynInstPtr>::reset()
134{
135    // Clear the dependency graph
136    DepEntry *curr;
137    DepEntry *prev;
138
139    for (int i = 0; i < numEntries; ++i) {
140        curr = dependGraph[i].next;
141
142        while (curr) {
143            memAllocCounter--;
144
145            prev = curr;
146            curr = prev->next;
147            prev->inst = NULL;
148
149            delete prev;
150        }
151
152        if (dependGraph[i].inst) {
153            dependGraph[i].inst = NULL;
154        }
155
156        dependGraph[i].next = NULL;
157    }
158}
159
160template <class DynInstPtr>
161void
162DependencyGraph<DynInstPtr>::insert(PhysRegIndex idx, DynInstPtr &new_inst)
163{
164    //Add this new, dependent instruction at the head of the dependency
165    //chain.
166
167    // First create the entry that will be added to the head of the
168    // dependency chain.
169    DepEntry *new_entry = new DepEntry;
170    new_entry->next = dependGraph[idx].next;
171    new_entry->inst = new_inst;
172
173    // Then actually add it to the chain.
174    dependGraph[idx].next = new_entry;
175
176    ++memAllocCounter;
177}
178
179
180template <class DynInstPtr>
181void
182DependencyGraph<DynInstPtr>::remove(PhysRegIndex idx,
183                                    DynInstPtr &inst_to_remove)
184{
185    DepEntry *prev = &dependGraph[idx];
186    DepEntry *curr = dependGraph[idx].next;
187
188    // Make sure curr isn't NULL.  Because this instruction is being
189    // removed from a dependency list, it must have been placed there at
190    // an earlier time.  The dependency chain should not be empty,
191    // unless the instruction dependent upon it is already ready.
192    if (curr == NULL) {
193        return;
194    }
195
196    nodesRemoved++;
197
198    // Find the instruction to remove within the dependency linked list.
199    while (curr->inst != inst_to_remove) {
200        prev = curr;
201        curr = curr->next;
202        nodesTraversed++;
203
204        assert(curr != NULL);
205    }
206
207    // Now remove this instruction from the list.
208    prev->next = curr->next;
209
210    --memAllocCounter;
211
212    // Could push this off to the destructor of DependencyEntry
213    curr->inst = NULL;
214
215    delete curr;
216}
217
218template <class DynInstPtr>
219DynInstPtr
220DependencyGraph<DynInstPtr>::pop(PhysRegIndex idx)
221{
222    DepEntry *node;
223    node = dependGraph[idx].next;
224    DynInstPtr inst = NULL;
225    if (node) {
226        inst = node->inst;
227        dependGraph[idx].next = node->next;
228        node->inst = NULL;
229        memAllocCounter--;
230        delete node;
231    }
232    return inst;
233}
234
235template <class DynInstPtr>
236void
237DependencyGraph<DynInstPtr>::dump()
238{
239    DepEntry *curr;
240
241    for (int i = 0; i < numEntries; ++i)
242    {
243        curr = &dependGraph[i];
244
245        if (curr->inst) {
246            cprintf("dependGraph[%i]: producer: %#x [sn:%lli] consumer: ",
247                    i, curr->inst->readPC(), curr->inst->seqNum);
248        } else {
249            cprintf("dependGraph[%i]: No producer. consumer: ", i);
250        }
251
252        while (curr->next != NULL) {
253            curr = curr->next;
254
255            cprintf("%#x [sn:%lli] ",
256                    curr->inst->readPC(), curr->inst->seqNum);
257        }
258
259        cprintf("\n");
260    }
261    cprintf("memAllocCounter: %i\n", memAllocCounter);
262}
263
264#endif // __CPU_O3_DEP_GRAPH_HH__
265